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Rehabilitation of degraded drylands is challenged by environmental and anthropogenic constraints, such as limited availability of locally-sourced topsoil and poor quality alternative soil substrates. Current rehabilitation practices, at times, utilise inorganic soil amendments to improve the physicochemical and biological characteristics of reconstructed soil profiles. These approaches may be appropriate for dryland rehabilitation, but there is limited research available regarding the benefits of using these amendments. Here, we present a study in the Pilbara region of Western Australia, an arid landscape subject to intensive mining that currently uses inorganic soil amendments (gypsum and urea) in post-mining rehabilitation. The aim of this study was to assess the effectiveness of these amendments to (1) promote seed germination, seedling emergence and seedling growth across five plant species and, (2) re-instate soil quality in mine waste substrates. A series of glasshouse experiments assessed eight application combinations of these amendments in two alternative substrates and compared these to unamended substrates and topsoil. Soil amendments had a limited influence on seed germination, were detrimental to seedling emergence and resulted in increased seedling mortality. Mortality in the waste ranged from 2 to 61% but increased to 7–92% in amended waste. Seedling growth improved with high doses of amendments in waste, with a 1.3–5.6-fold increase across all plant species. Soil quality was relatively unaffected by amendments with soil nitrogen ranging from 0.01 to 0.08%, organic carbon from 0.01 to 0.12% and soil microbial activity from 2.3 to 2.4 ppm-CO2 in the amended and unamended waste. The use of soil amendments in mine rehabilitation requires consideration of the trade-off between initial reductions in seedling recruitment and enhanced seedling development at later stages. Future rehabilitation should consider the timing of amendment application to avoid detrimental impacts on seedling recruitment and maximise the benefits to seedling growth.

Hydrothermal carbonization is a promising approach of biosolids management and its utilization as a soil amendment. This study evaluated the physical and chemical properties of hydrothermally converted biosolids (Sewchar) and its effect as a potential soil amendment on the growth of rice, beans, and radish. The germination experiment was conducted in a greenhouse in a randomized design using five Sewchar doses (0, 10, 20, 40 and 60 Mg ha-1). The results showed that hydrothermal carbonization influences the physicochemical properties of the biosolids, such as promoting pore structure and trace elements below the threshold values for use in agriculture. The spectroscopic techniques demonstrated higher presence of oxygen-containing functional groups (e.g., CO/OH) on surfaces of Sewchar than that of biosolids. The Sewchar doses of 10 Mg ha-1 and 60 Mg ha-1 yielded the highest dry biomass for beans and rice respectively. Increasing Sewchar doses negatively correlated with radish dry biomass, as indicated by linear regression equation fitting (p

The reuse of water in agriculture has become more common in water management worldwide. However, there is very limited information about nutrient retention in water reclamation management. In this study, an improved low impact development (LID) practice was constructed to investigate the synergistic effects of three substrates amendment on nitrogen (N) and phosphorus (P) retention under two irrigation modules: spray and drip irrigation. The orthogonal combination of the three substrates was controlled during four leaching events, with polyacrylamide (PAM), peat soil, and straw biochar application rates of 1, 2, and 4 g kg−1; 5, 10, and 20 g kg−1; and 10, 20, and 40 g kg−1, respectively. Results showed that the optimum treatments for N and P were 2 g kg−1 of PAM; 2 g kg−1 of PAM, 10 g kg−1 of peat soil, and 40 g kg−1 of straw biochar, respectively. The highest amounts of N and P retention under spray and drip irrigation were 83.12 mg N kg−1 and 50.09 mg N·kg−1, and 11.88 mg P·kg−1 and 7.47 mg P·kg−1, respectively. The analysis of variance indicated that PAM, biochar, and peat soil affected the retention of leachate, N, and P differently. PAM application could not only improve the water, N, P retention capacity of soil, but also significantly increase the content of ＞2 mm water-stable soil aggregate (WSA) (p＜0.05), and there is an advisable linear relation between N, P retention and the content of ＞2 mm WSA (R2 = 0.79, 0.67, respectively). Overall, this study concludes that a combined application of PAM and biochar could reduce P loss and increase the ＞2 mm WSA under leaching condition.

The hydrochars derived from swine manure were prepared by CaO assisted hydrothermal carbonization (HTC), and their properties were investigated for the first time. The results showed that the pH and yield of the hydrochar were largely increased by CaO addition. HTC of swine manure increased the phosphorus (P) content in the hydrochar, and appropriately 100% of P as apatite-P was enriched in the hydrochar by CaO assisted HTC. Additionally, the CaO addition during HTC improved the porosity of the hydrochar. The FTIR analysis revealed that substantial functional groups were present on the surface of the hydrochar, indicating the facilitated exchange between the hydrochar and hydrophilic soil when the hydrochar was used for soil amendment. This study demonstrated that CaO assisted HTC was a novel strategy to quickly convert swine manure to the promising soil amendment especially for acidic soils.

Problem soils are referred to as those with poor physical, chemical, and biological properties that inhibit or prevent plant growth. These poor properties may be a result of soil formation processes but are largely due to inappropriate farming practices or anthropogenic pollution. The world has lost a third of its arable land due to erosion and pollution in the past 40 years. Thus, there is an urgent need for improving and remediating problem soils. As a novel multifunctional carbon material, biochar has been widely used as a soil amendment for improving soil quality. Previous reviews have summarized the characteristics of biochar, the interactions with various soil contaminants, and the effects on soil quality, soil productivity, and carbon sequestration. Relatively limited attention has been focused on the effects of biochar amendment on plant growth in problem soils. As a result, a comprehensive review of literature in the Web of Science was conducted with a focus on the effects of biochar amendment on plant growth in problems soils. The review is intended to present an overview about problem soils, biochars as functional materials for soil amendment, how amended biochars interact with soils, soil microbes, and plant roots in remediation of problem soil and improve plant growth. Additionally, existing knowledge gaps and future directions are discussed. Information gathered from this review suggests that biochar amendment is a viable way of improving the quality of problem soils and enhancing crop production. It is anticipated that further research on biochar amendment will increase our understanding on the interactions of biochar with components of problem soils, speed up our effort on soil remediation, and improve crop production in problem soils.

In many developing countries water scarcity has led to the use of wastewater, often untreated, to irrigate a range of crops, including tuber crops such as potatoes (Solanum tuberosum L.). Untreated wastewater contains a wide range of contaminants, including heavy metals, which can find their way into the edible part of the crop, thereby posing a risk to human health. An experiment was undertaken to elucidate the fate and transport of six water-borne heavy metals (Cd, Cr, Cu, Fe, Pb and Zn), applied through irrigation water to a potato (cv. Russet Burbank) crop grown on sandy soil, having either received no biochar amendment or having top 0.10 m of soil amended with 1% (w/w) plantain peel biochar. A non-amended control, irrigated with tap water, along with the two contaminated water treatments were replicated three times in a completely randomized design carried out on nine outdoor PVC lysimeters of 1.0 m height and 0.45 m diameter. The potatoes were planted, irrigated at 10-day intervals, and leachate then collected. Soil samples collected two days after each irrigation showed that all heavy metals accumulated in the surface soil; Fe, Pb and Zn were detected at 0.1 m depth, while only Fe was detected at 0.3 m depth. Heavy metals were not detected in the leachate. Tested individually, all portions of the potato plant (tuber flesh, peel, leaf, stem and root) bore heavy metals. Biochar-amended soil significantly reduced only Cd and Zn concentrations in tuber flesh (69% and 33%, respectively) and peel compared to the non-amended wastewater control (p < 0.05). Heavy metal concentrations were significantly lower in the tuber flesh than in the peel, suggesting that when consuming potatoes grown under wastewater irrigation, the peel poses a higher health risk than the flesh.

This work was supported by project PY20_00585 from Andalusian Ministry of Economic Transformation, Knowledge Industry and Universities. This paper will form part of Ana Cervera-Mata's doctoral thesis, which is being developed within the context of the “Nutrition and Food Sciences Programme” at the University of Granada. The authors are very grateful to Mrs. Emanuela Vida for her skilful technical assistance. The authors also acknowledge Melanie Davis for English proofreading. Funding for open access charge: Universidad de Granada / CBUA ., SCG are a bio-waste generated in great amount worldwide which are attractive as soil amendment for their high content of organic matter and nutritive elements. Nevertheless, several studies have shown that soil application of untreated SCG has detrimental agronomic and environmental effects due to their high degradability and content of noxious compounds (phenols, caffeine, and tannins). However, SCG can be valorised, in the frame of circular economy, by extraction of energy and valuable products (carbohydrates, proteins, bio-oil, bio-diesel) and generation of solid by products (biochar, hydrochar, compost) that can be utilized as soil fertilizers and amendments. Therefore, the aim of this work was the characterization of different solid SCG by-products (as second-generation products) and their assessment as effective organic amendments. The novelty of this study is that for the first time 8 different by-products derived from the same SCG were characterized and comparatively evaluated for their impact on the C and N cycles of soil. SCG was collected and treated to generate 8 different SCG by-products (biochars produced at 270 and 400 °C, hydrochars produced at 160 and 200 °C, vermicompost, defatted SCG and biochars produced from defatted SCG at 270 and 400 °C). SCG and derived by-products were characterized for SEM micromorphology, pH and EC values, and C, N, H, O, volatile matter, fixed C, LOI, carbonates, water soluble C and N, NO3− and NH4+ content. SCG and SCG by-products assessment as organic amendments was performed with an incubation experiment. The residues were added (2.5%) to a moist Mediterranean agricultural soil and the amended soil samples were placed in mesocosms and incubated at 20 °C for 30 days. During incubation, CO2 and N2O emissions were measured every 6 h by means of a gas chromatography automated system for GHG sampling and measurement. The percentage of added C remaining (CR) in the soil was calculated by fitting the cumulative respiration of amended soil to a two-pool model. After 2, 7 and 30 days of incubation, the control and amended soils were sampled and analyzed for their content of extractable organic C, N, NO3− and NH4+ and microbial biomass C and N. Results showed that SCG by-products presented a great variability in their properties. SCG and hydrochars presented higher contents in volatile matter and water soluble C and N, and low content of fixed C, while biochars showed an opposite behaviour. SEM images confirmed the different characteristics of the SCG by-products: the biochar presented a porous structure, honeycomb-like form, due to the loss of the more soluble compounds, while the SCG and hydrochars' pores were filled with amorphous carbonaceous materials. Consequently, soil addition of SCG by-products showed a distinct impact on C and N cycle and microbial biomass content. Addition of SCG and hydrochars generated the highest cumulative CO2–C emissions (2103–2300 μg g−1), the lower amount of CR (86.8–88.6%), increased the soil extractable organic C and microbial biomass C and N and caused N immobilization. On the other hand, the addition of biochars generated lower CO2–C emissions (542–1060 μg g−1), higher amounts of CR (96. 3–99.9%) and lower amounts of extractable compounds and microbial biomass C and N, generating also N immobilization, but to a lesser extent. The addition of vermicompost generated 723 μg g−1 of CO2–C and 98% of CR remaining. However, this by-product did not generate N immobilization being able to act as N fertilizer. None of the residues generated N2O emissions. The different properties of the SCG by-products and their impact on C and N cycle indicated that they can be effectively applied to soil to exert different agronomical and environmental functions., Andalusian Ministry of Economic Transformation, Knowledge Industry and Universities, CBUA, Universidad de Granada

This study investigated the long-term leachability of antimony (Sb) in a smelting residue (39519 mg/kg) solidified/stabilized by reactive magnesia (MgO). Different dosages of MgO (0% as control, 2%, 5%, and 10% on a dry basis) were compared, and the long-term performance was evaluated by an accelerated exposure test consist of 20 consecutive leaching steps with simulated strong acid rain (SAR, HNO3: H2SO4 = 1:2, pH = 3.20) as the extractant. Notably, the MgO treatments efficiently reduced the Sb leachability. Compared to the original slag (8.3 mg/L), the leaching concentrations based on a Chinese standard HJ/T299-2007 were reduced by 58%, 79%, 85%, and 86% at MgO dosages of 0%, 2%, 5%, and 10%, respectively. Because the studied slag was rich in oxides like SiO2, CaO, and MgO, the hydration reactions probably happened during the aging processes with oxic water. It was inferred that the formed hydration products have a self-solidification/stabilization function to suppress the Sb leaching from the solid phase. The mineralogical characterization results proved that the hydrated Mg(OH)2 played an essential role in the decrease of Sb leachability. Besides, the MgO addition promoted the hydration of this smelting slag and formed new hydrate gels that immobilize Sb in this slag. Our results confirmed that MgO-amended slags were resistant to continuous SAR corrosion. Compared to the control, the dosage of 5% MgO could effectively reduce the cumulatively released Sb by 57%, with only 0.46% of total Sb could be leached. The decomposition of Mg(OH)2 and hydrate gels determined the re-release of Sb in a long term. Our work has demonstrated that reactive MgO amendment could be potentially selected as an effective strategy for the treatment of Sb-containing smelting residues in field conditions.

The effectiveness and mechanism of aluminum/iron co-modified calcite (Al/Fe-CA) for the control of phosphorus (P) liberation from sediments was investigated. The results showed that Al/Fe-CA possessed good sorption performance for phosphate, and the maximum phosphate sorption capacity for Al/Fe-CA could reach 27.0 mg/g. The major mechanisms involved the surface adsorption of phosphate on calcite, the precipitation between phosphate and Ca2+ leached from calcite, and the ligand exchange between Al/Fe-bound hydroxyl groups and phosphate to form the Al–O–P and Fe–O–P inner-sphere complexes. The re-releasing risk of Al/Fe-CA-bound P under the circumstances of normal pH (5–9) and reducing environment was very low. Al/Fe-CA addition could significantly reduce the risk of P releasing from sediment to overlying water (OL-water), and the inactivation of mobile P, reactive soluble P (SRP) and diffusive gradient in thin-films (DGT)-labile P in sediment by Al/Fe-CA had a great part in the suppression of sediment-P liberation to OL-water by the Al/Fe-CA amendment. Al/Fe-CA capping and fabric-wrapped Al/Fe-CA capping both could greatly reduce the risk of P releasing from sediment into OL-water, and the formation of a static layer with low concentrations of SRP and DGT-labile P in the upper sediment was the key to sustaining a high P controlling efficiency. When the applied mode of Al/Fe-CA varied from capping to amendment, although the inactivation efficiency of DGT-labile P in the overlying water and upper sediment by Al/Fe-CA would decrease to a certain degree, the inactivation efficiency of DGT-labile P in the lower sediment by Al/Fe-CA would increase. Results of this study suggest that Al/Fe-CA has the high potential to be used as an active capping or amendment material for the management of internal P loading in surface water bodies.

Modified lignite and black coal (BC) are potential amendments for animal bedding to abate ammonia (NH3) emissions due to their large adsorption capacities for ammoniacal nitrogen (N). However, the ability of modified lignite and BC in reducing NH3 volatilization from livestock manure and the underlying mechanisms remain unknown. The present study has investigated the effect of lignite, modified lignite, BC and modified BC on NH3 volatilization from cattle manure, biological immobilization of manure ammoniacal N and manure properties. Modified lignite and BC reduced the NH3 volatilization from manure by 44 and 36%, respectively, which were comparable with original lignite (43%). The biological immobilization of applied stable isotope labelled 15N in lignite, modified lignite, BC and modified BC amended manures was 15, 18, 11 and 16%, respectively, which were significantly higher than that in unamended manure (4%, P

In this work, we evaluated the valorisation of agricultural waste materials by transforming coconut husks and shells, corncobs and rice straw into biochar for water treatment in aquaculture. We compared the biochars’ suitability for removal of organic micropollutants (acetaminophen, oxytetracycline, tetracycline, enrofloxacin, atrazine, diuron and diclofenac) from surface water needed for aquaculture. The biochars were prepared by three methods ranging from inexpensive drum kilns (200 °C) to pyrolysis with biogasfication (350–750 °C). Overall, antibiotics tetracycline and enrofloxacin were the most strongly sorbed micropollutants, and coconut husk biochar prepared at 750 °C was the best sorbent material. Molecular Dynamics simulations indicated that the major sorption mechanism is via π-π stacking interactions and there is a possibility of multilayer sorption for some of the micropollutants. We observed, a strong impact of ionic strength (salinity), which is an important consideration in coastal aquaculture applications. High salinity decreased the sorption for antibiotics oxytetracycline, tetracycline and enrofloxacin but increased diclofenac, atrazine and diuron sorption. We considered coconut husk biochar produced in drum kilns the most practical option for biochar applications in small-scale coastal aquacultures in South Asia. Pilot trials of canal water filtration at an aquaculture farm revealed that micropollutant sorption by coconut husk biochar under real-world conditions might be 10–500 times less than observed in the laboratory studies. Even so, biochar amendment of sand enhanced the micropollutant retention, which may facilitate subsequent biodegradation and improve the quality of brackish surface water used for food production in coastal aquaculture., Graphical abstract Image 1, Highlights • Biochars (BCs) derived from agricultural waste were evaluated for water treatment. • Four wastes, three pyrolysis methods and seven micropollutants were investigated. • Coconut husk BC pyrolysed at 750 °C was the best micropollutant sorbent. • Molecular dynamics simulations indicated that the major sorption mechanism is via π-π stacking interactions. • BC amendment benefits in water filtration were demonstrated for field conditions.

If biochar is applied to soil or stormwater treatment media, the saturated hydraulic conductivity (K) may be altered, which is a critical property affecting media performance. While a significant number of studies document biochar's effect on a porous medium's K, predictive models are lacking. Herein models are advanced for predicting K for repacked natural soil and engineered media when amended with biochar of various particle sizes and application rates. Experiments were conducted using three repacked natural soils, two uniform sands, and a bioretention medium amended with a wood biochar sieved to seven different biochar particle size distributions and applied at three rates. Experimental measurements showed a strong positive correlation between the interporosity of each medium and K. Across all media, the classic Kozeny-Carman (K–C) model predicted K and the relative change in K because of biochar amendment for each medium best. For soils alone, a recently developed model based on existing pedotransfer functions was optimal. The K–C model error was improved if the particle specific surface area was increased for large biochar particles, which indicates the importance of biochar particle shape on pore structure and K. X-ray Computed Tomography was coupled with pore network modeling to explain the unexpected decrease in K for sands amended with medium and large biochar. While biochar increased interporosity, mean pore radii decreased by ~25% which reduced K. The X-ray measurements and pore network modeling help to explain anomalous results reported for biochar-amended sands in other studies.

Phytomanagement is considered a suitable option in line with nature-based solutions to reduce environmental risks associated to metal(loid) mine tailings. We aimed at assessing the effectiveness of biochar from pruning trees combined with compost from urban solid refuse (USR) to ameliorate the conditions of barren acidic (pH ~5.5) metal(loid) mine tailing soils (total concentrations in mg kg-1: As ~220, Cd ~40, Mn ~1800, Pb ~5300 and Zn ~8600) from Mediterranean semiarid areas and promote spontaneous plant colonization. Two months after amendment addition were enough to observe improvements in chemical and physico-chemical tailing soil properties (reduced acidity, salinity and water-soluble metals and increased organic carbon and nutrients content), which resulted in lowered ecotoxicity for the soil invertebrate Enchytraeus crypticus. Recalcitrant organic carbon provided by biochar remained in soil whereas labile organic compounds provided by USR were consumed over time. These improvements were consistent for at least one year and led to lower bulk density, higher water retention capacity and higher scores for microbial/functional-related parameters in the amended tailing soil. Spontaneous growth of native vegetation was favored with amendment addition, but adult plants of remarkable size were only found after three years. This highlights the existence of a time-lag between the positive effects of the amendment on tailing soil properties being observed and these improvements being translated into effective spontaneous plant colonization. The present study was supported by the project RESCLICONT (CGL2016-80981-R), funded by the Ministry of Science, Innovation and Universities of Spain through FEDER funds; by the project METOXCLIM (PTDC/CTA-AMB/29557/2017), funded by FEDER, through COMPETE2020 - Programa Operacional Competitividade e Internacionalização (POCI), and by national funds (OE), through FCT/MCTES. Thanks are due to FCT/MCTES for the financial support to CESAM (UIDP/50017/2020+UIDB/50017/2020), through national funds. A. Peñalver-Alcalá was hired by the project RESCLICONT. In addition, he received two mobility fellowships for short stays at the University of Aveiro, one from the Campus Mare Nostrum of the Murcia Region-Spain and the other one from the Internal PhD Mobility Program of the Technical University of Cartagena. M.N. González-Alcaraz holds a Saavedra Fajardo research contract from the Séneca Foundation of the Murcia Region-Spain. The authors thank F.J. Jiménez-Cárceles from Biocyma S.L. for his valuable help with vegetation fieldwork. We also thanks D. Sánchez Bisquert, I. Tunç and P.A. Madrid Sánchez for their valuable help during the laboratory work

Bioretention structures such as planter boxes, swales and rain gardens are being increasingly utilized in built landscapes as a strategy to attenuate both stormwater flows and contaminant loads. Copper (Cu) roofing materials contribute significantly higher mass loads of dissolved Cu per unit area than other surfaces such as parking lots and roadways. While a recent study demonstrated that conventional bioretention media can remove greater than 90% of Cu from copper roof runoff, the median Cu concentrations at the point of discharge from bioretention structures (66 μg L-1) still did not achieve Cu concentrations in stormwater discharges sought in some jurisdictions (for example, < 14 μg L-1). Consequently, commercially available soil amendments were assessed to improve bioretention Cu removal. The ability of biochar, greensand, and zeolite to improve Cu removal was evaluated in laboratory column studies. Additionally, the performance of zeolite as an underlayer amendment was evaluated in bioretention planter boxes treating stormwater from a picnic shelter with a partitioned copper roof. Cu was measured in the planter box influent and effluent. The field setup included 2 control planter boxes containing only standard bioretention media and 2 amended with the zeolite underlayer. Samples from ten storms were collected with flow-weighted composite sampling. Total Cu in composite samples of the influent waters ranged from 445 to 1683 μg L-1 and had a median concentration of 934 μg L-1. Total Cu in the effluent from the control planter boxes ranged from 10 to 64 μg L-1, with a mean of 29 μg L-1. Total Cu in effluent from the zeolite amended planter boxes ranged from 4 to 44 μg L-1 with a mean of 18 μg L-1. Attenuation in the control planter boxes ranged from 90 to 99% with a median of 93.4% by concentration and ranged from 95 to 99% with a median of 97.5% in the zeolite amended planter boxes.

Despite efforts to utilise bauxite residue, the amount of red mud stored in reservoirs is increasing. This paper aims to evaluate the potential of red mud and other sludge waste types as a soil substitute by monitoring plant development. Pot experiments were carried out testing two types of mixtures: dredging sludge from Lake Balaton mixed with garden soil and the sewage sludge and soil blend. These were then treated with red mud (15 and 30% w/w). The plants were under-, while the roots were more developed in the sewage sludge mix than the dredging sludge blend and the control soil. In the sewage amendment, the phosphorous content increased while the calcium content was lower than in the other soil types and the optimum. The metals uptake of the plants was a factor of the red mud quantity. Lead, nickel, titanium and silicon had elevated concentrations parallel to higher red mud content, but only the nickel exceeded the threshold of the Hungarian legislation. Silicon and titanium were beneficial for plant growth, compensating for the potentially toxic effects of lead and nickel. Results suggest that the red mud in a mixture with either sewage sludge or dredging sludge can act as catalysts for the growth rate of test plants, allowing their utilisation as secondary raw materials.

Assessing the relationship between soil enzyme activities (SEAs) and heavy metals (HMs) without any amendment has rarely been conducted in soils contaminated with municipal solid wastes (MSW). Five soil enzymes [dehydrogenase (DHA), alkaline phosphatase (ALP), acid phosphatase (ACP), urease (UR), and nitrate reductase (NR)] have been assessed for HMs bioremediation using Zea mays L. grown in unamended soils that were contaminated with different types of MSW. Pot experiment was conducted for two seasons with soils collected from seven different locations within the MSW site. Experimental soil samples included a control (CA), contaminated by brick kiln wastes (SA1), kitchen and household wastes (SA2), medical wastes (SA3), mixed wastes (SA4), glass wastes (SA5), and metal scrap wastes (SA6). Rhizospheric soils were collected after the harvest of each season to investigate the impact of HMs on SEAs and physicochemical properties of soil. The results revealed an increase in DHA, ALP, and NR activities by 89.30%, 58.03% and 21.98% in SA1. Likewise, enhanced activities for UR (28.26%) and ACP (19.6%) were observed in SA3 and SA5 respectively. Insignificant increase in the macronutrients and organic carbon (OC) were also noted. The increased microbial count and the relatively higher amount of organic matter (OM) in the rhizosphere indicated the role of OM in HMs immobilization. Principal component analysis (PCA) indicated that DHA and NR are the important soil enzymes, underscored by their active involvement in the C and N turnover in the soil. Likewise, correlation analysis showed that DHA and NR activities were positively correlated with copper (Cu) (0.90, p

Bioconversion of organic waste by the black soldier fly (BSF) larva yields a by-product commonly known as 'frass'. Although BSF larval frass has often been marketed as a biofertilizer, few studies have evaluated this claim. In this study, BSF larvae reared on a pure okara diet achieved an 85% waste reduction in the fresh weight of the okara. Subsequently, the frass was mixed with soil at concentrations of 10, 20, and 30% (vol/vol), and used to cultivate lettuce plants. At 10% concentration, the lettuce plants had biomasses comparable to those of the controls. Higher frass concentrations stunted the growth of the lettuce, likely because of the low C:N ratio of larval frass resulting from the rapid mineralization of nutrients. Larval frass was also found to be able to provide sufficient nutrients for lettuce growth as fertilizer application was only necessary after the first growth cycle, suggesting its suitability as a soil amendment. Analyses of the microbial community of all the growing media showed that the growth medium treatments with BSF larval frass tended to have a lower number of microbial species than the controls. Inherently higher micronutrient levels present in the frass resulted in the growth of lettuce plants. More importantly, the microbial analysis revealed that common foodborne pathogens were absent in the BSF larval frass and elemental analysis also indicated no heavy metal pollutants present. Overall, BSF larval frass was found to be a suitable soil amendment and more in-depth studies could facilitate its sensible use in agriculture.

The goal of the present study was to evaluate the immobilization and retention of caffeine (CFN) in soil and the influence of biochar for the CFN transport in agricultural soil. The biochar was produced from the Ulva reticulata seaweed biomass (ULBC) under the slow-pyrolysis with a heating rate of 7 °C/min at 500 °C and characterized using XRD and FTIR. The CFN retention and transport abilities in loamy sand and ULBC amended (2.5%) soil were evaluated under various pH values range of 3–10 and at various CFN concentrations using batch and column experiments. The surface orientation of ULBC was portrayed as the randomized distribution of hetero and homogeneous nature. The highest retention capacity (40 μg/g) was obtained at pH 4.0. Soil amendment with ULBC shows a higher retention affinity towards CFN, of up to 150 μg/g than soil, with minimal pH dependence. The maximum CFN adsorption capacities of soil and amended soils were 420 and 820 μg/g, respectively, based on the Langmuir model. Batch experiments suggested the adsorption of CFN by the biochar amended loamy soil is governed by the electrostatic attraction. The column experiment data demonstrated a high transport potential of CFN in the loamy sand; however, a strong cumulative reduction of transport (58%) was observed with the application of ULBC into the loamy sand. Thus, the addition of seaweed biochar as an amendment in soils with biosolids and wastewater irrigation may reduce the mobilization of CFN to the aquatic system and possibly reduce plant uptake.

The impact of ferric iron stimulation on the evolution of microbial structure in marine sediment microbial fuel cells (SMFCs), operated for the bioremediation of a complex mixture of low and high molecular weight PAHs (naphthalene, fluorene, pyrene and benzo(a)pyrene), was assessed. Microbial evolution profiles showed high relative abundances of exoelectrogenic iron-reducing bacteria throughout the biodegradation, namely Geoalkalibacter, under ferric iron stimulation and anode reducing conditions, irrespective of sulfate reducing bacteria (SRB) inhibition. Highest PAHs removal was measured in the absence of anode reduction, under Fe stimulation and SRB inhibition, reaching 40.85% for benzo(a)pyrene, the most persistent PAH used in this study. Results suggest that amendment of contaminated sediment with ferric iron could constitute a better bioremediation strategy than using SMFCs. This becomes significant when considering the well-established and dominant indigenous SRB population in marine sediments that usually limits the performance of the anode as a terminal electron acceptor in marine SMFCs.

While the use of biochar as a soil amendment is gaining popularity for environmental and agricultural purposes, spatial heterogeneity of biochar (segregation) in biochar-amended media and its underlying causes have been overlooked. In this study, for the first time particle segregation in biochar-amended media and its impact on the media's saturated hydraulic conductivity ( K s a t ) were investigated. Two uniformly graded media were amended with different sizes of a wood-based biochar under dry and wet conditions. While the intended biochar volume fraction ( b f ) was 17.5%, in dry-packed columns biochar was often segregated and the measured b f ranged from 7.5 ± 0.8 SE% (SE = standard error) to 23.6 ± 1.8 SE% across all spatial locations. If, however, 20% water (volume of water/bulk volume of packed media) was added to the mixtures during mixing, homogeneous packings were achieved. In dry-packing, segregation was governed by the difference in the physical properties of the media and the biochar: particle size, density, and shape. In wet-packing, segregation was prevented due to the inter-particle adhesion forces associated with water. Although X-ray computed tomography images showed that the presence of segregation altered particle distributions and pore morphologies, the K s a t for wet-packed and dry-packed columns were statistically identical. The results of this study suggest that laboratory methods for packing biochar-amended media should include moisturizing the mixture to inhibit particle segregation. Mixing under wet conditions is recommended for any type of soil and biochar and for any scale of application, in both the laboratory and field.

Soil respiration (or CO2 production) is often determined by measuring CO2 efflux; however, there are differences between them in saline-alkali soils of arid land. The purpose of this study is to test a hypothesis that CO2 production exceeds efflux in arid saline-alkali soils under organic and gypsum amendments. We conducted a modeling study that was based on a two-year field experiment with four treatments: control, gypsum addition, wheat straw incorporation, and gypsum-straw combination. A diffusion model was forced by soil CO2, temperature and moisture that were continuously recorded at 0, 8 and 15 cm, and calibrated by measured CO2 efflux. We then applied the model to calculate CO2 production and efflux over 2014–2015, and found a strong and similar seasonality in both CO2 production and efflux under all treatments (i.e., highest in summer with one peak in 2014 and two peaks in 2015). Our results showed enhanced CO2 production and efflux over short period following rainfall. There were significantly exponential relationships between CO2 production/efflux and temperature. While straw incorporation significantly increased CO2 production and efflux, straw incorporation combined with gypsum amendment caused a decrease in CO2 production and efflux. CO2 production exceeded CO2 efflux mainly in the first half year, and annual difference was 33–130 g C m−2, with larger differences under gypsum amendment. Our study implies that a portion of respired CO2 is transformed into other forms and stored in saline-alkaline soils in arid land.

The present study assesses the effect of tailing texture (loamy sand (LT) and sandy loam (ST)), dose of pig sludge (0, 50, 100 and 200 t ha−1) and amendment-contact time (14, 28 and 42 days) on physicochemical quality of amended substrate using Lolium perenne var Nui as a bioindicator. The main properties of LT differed of ST in levels of total organic carbon (0.19 and 0.58%), in pH (4.6 and 8.5), total Cu (202 and 1647 mg kg−1) and Zn content (31 and 137 mg kg−1). Soil pore water of experimental substrates was characterized for pH, electrical conductivity (EC) and Cu2+ ion activity (pCu2+) while ammonium nitrogen (NH4+-N), infiltration rate and general physicochemical characteristics were measured in substrates. Shoot biomass (SB), root biomass (RB) and the RB:SB ratio was calculated for L. perenne. The results showed there to be a significant interaction (p 28 days, irrespective of tailing texture.

© 2019 Phytotechnologies have been used worldwide to remediate and restore damaged ecosystems, especially those caused by industrial byproducts leaching into rivers and other waterways. The objective of this study was to test the growth, physiology, and phytoextraction potential of poplar and willow established in soils amended with heavy-metal contaminated, dredged river sediments from the Great Bačka Canal near Vrbas City, Serbia. The sediments were applied to greenhouse-grown trees of Populus deltoides Bartr. ex Marsh. clone ‘Bora’ and Salix viminalis L. clone ‘SV068’. Individual pots with trees previously grown for two months were amended with 0, 0.5 and 1.0 kg of sediment containing 400 mg Cr kg −1 , 295 mg Cu kg −1 , 465 mg Zn kg −1 , 124 mg Ni kg −1 , 1.87 mg Cd kg −1 , and 61 mg Pb kg −1 . Following amendment, trees were grown for two seasons (i.e., 2014, 2015), with coppicing after the first season. In addition to growth parameters, physiological traits related to the photosynthesis and nitrogen metabolism were assessed during both growing seasons. At the end of the study, trees were harvested for biomass analysis and accumulation of heavy metals in tree tissues and soils. Application of sediment decreased aboveground biomass by 37.3% in 2014, but increased height (16.4%) and leaf area (19.2%) in 2015. Sediment application negatively impacted the content of pigments and nitrate reductase activity, causing them to decrease over time. Generally, the effect of treatments on growth was more pronounced in poplars, while willows had more pronounced physiological activity. Accumulation patterns were similar to previously-published results. In particular, Zn and Cd were mostly accumulated in leaves of both poplar and willow, which indicated successful phytoextraction. In contrast, other metals (e.g., Cr, Ni, Pb, Cu) were mostly phytostabilized in the roots. Differences in metal allocation between poplar and willow were recorded only for Cu, while other metals followed similar distribution patterns in both genera. Results of this study indicated that the composition of heavy metals in the sediments determined the mechanisms of the applied phytoremediation technique.

Nitrogen (N) bioavailability is one of the main limiting factors for microbial activity and vegetation establishment in bauxite-processing residue sand (BRS). Although beneficial effects of biochar on reducing N loss in the early stages of BRS rehabilitation have been observed previously, the underlying mechanisms of this complicated process, particularly the interactions between applied biochar and the plant rhizosphere is largely unknown. This glasshouse study (116 days), investigated the coupled effects of biochar and water stress on N bioavailability in the rhizosphere of ryegrass (Lolium rigidum) grown in BRS amended with di-ammonium phosphate (DAP) fertiliser (at rates of 0 or 2.7 t ha−1) with and without biochar amendment. The applied biochar was characterised as either aged acidic (AC) or alkaline pine (PC) and was mixed with BRS at a rate of 5% v/v under four moisture regimes (50%, 40%, 20% and 7.5% water holding capacity). Amending BRS with AC and PC biochars increased NH4 + retention and decreased cumulative NH3 volatilization within both the rhizosphere and root-free zones compared with fertiliser only treatment. These effects were more pronounced for the AC than PC biochar, suggesting that aged acidic biochar has the great potential for use in rapid establishment of vegetation in BRS disposal areas. The biochar amendment increased cumulative nitrous oxide emissions compared with DAP only treatment, with no significant differences among different moisture regimes. The Control and 20% water holding capacity (WHC) treatment showed the highest dissolved organic carbon (DOC) concentrations compared with other treatments and moisture regimes in the ryegrass rhizosphere, while the highest dissolved organic N concentration were observed in the DAP + AC treatment. Reducing moisture levels below 20% WHC generally decreased microbial biomass carbon (MBC) concentrations and activity in both the rhizosphere and root-free zones of all treatments, while total N generally decreased as moisture levels decreased from 50% to 7.5% WHC. Plant took up more N in the DAP + AC treatment compared with DAP + PC and DAP only treatments, while increasing water stress generally resulted in decreased aboveground biomass. © 2018

The conversion of poultry litter to hydrochar has been proposed for stabilization of the soils and to eliminate pathogens. Still, research on the hydrochar's effect on soil properties as a function of production temperature, and its direct use with plants is limited in general and even less so on poultry litter. We characterized poultry litter hydrochar as an amendment for sandy soils in terms of changes to the soil's bulk density, porosity, water-retention capacity, and fertility. Soil bulk density, porosity and water-retention capacity were determined in a pneumatic tension plate system for sand with hydrochar-amendment rates of 0.5, 1 and 2%, and hydrochar-production temperature of 180, 220, and 250 °C. Soil fertility was assessed by growing lettuce seedlings in a randomized block design planter experiment, consisting of 16 blocks that were sampled every 10 days. The addition of poultry litter hydrochar resulted in decreased soil bulk density. Soil porosity increased with hydrochar generated at a temperature of up to 220 °C, and decreased with hydrochar generated at 250 °C. Soil water content increased as compared to unamended sand, but decreased with increasing hydrochar-production temperature, probably due to increasing hydrophobicity of the poultry litter hydrochar. The addition of hydrochar at concentrations of 0.5 and 1% resulted in improved plant growth despite an initial delay. While increased soil moisture due to increased soil water-retention capacity was confirmed, it did not seem to be responsible for the improved plant growth. It was also demonstrated for the first time that hydrochar decreases nitrate leaching from soils. Therefore, poultry litter-derived hydrochar seems to be an adequate amendment for sandy soils.

Composting is a microbiological process that converts organic waste into organic soil amendment. We reveal enhanced biodiversity and microbial population with subsequent enhancement of composting efficiency of lignocellulosic waste using thermoacidophilic effective microorganisms (tEM). Composting with tEM + shading (tEMA) or tEM without shading (tEMB) increased the average microbial population by 12.0% or 6.7%, respectively compared to non-tEM composting without shading/control (C). The biodiversity in tEMA or tEMB treated groups was increased by 34.7% or 43.7%, respectively, compared to C. The highest increase in population (31.7% and 9.4%) and diversity (91.2% and 91.6%) were observed in tEMA and tEMB at 30 d, respectively. Regarding microbial structure, the most dominant phylum shifted from Proteobacteria to Bacteroidetes during composting. From 60 to 120 d, tEM notably improved the average abundance of Firmicutes (mainly Bacillus) by 166.7% and 75.8% in tEMA and tEMB groups, respectively. The overall gradation rate of large compost granules (2 mm) increased by 36.4% and 24.7%, following tEMA and tEMB treatment, respectively. The average rate of increase in bulk density was 42.6% or 33.3% by tEMA or tEMB, respectively, compared to C. We reveal the major differences in microbial structure, including a higher abundance of beneficial microbes like Bacillus in tEM treated composts. The study revealed that tEM could improve biodiversity and population of microbes, especially during thermophilic phase (above 45 °C), with a subsequent increase in composting rate, mineralization, and product quality. The results of this study are particularly invaluable in the areas of environmental conservation and organic agriculture.

The presence of atrazine a persistent herbicide in soil poses a serious threat to the ecosystem. The biochar amendment in soil altered the fate of this herbicide by modifying the soil properties. The present study examines the dissipation and toxicity of atrazine in three contrasting soils (silty clay, sandy loam, and sandy clay) without and with biochar amendment (4%). The experiment was performed for 150 days with three application rates of atrazine (4, 8, and 10 mg kg−1). The speciation and degradation of atrazine, metabolite content, microbial biomass, and enzymatic activities were evaluated in all treatments. Three kinetic models and soil enzyme index were calculated to scrutinize the degradation of atrazine and its toxicity on soil biota, respectively. The goodness of fit statistical indices suggested that the first-order double exponential decay (FODE) model best described the degradation of atrazine in silty clay soil. However, a single first order with plateau (SFOP) was best fitted for atrazine degradation in sandy loam and sandy clay soils. The half-life of atrazine was higher in sandy clay soil (27-106 day−1) than silty clay (28-77 day−1) and sandy loam soil (27-83 day−1). The variations in the dissipation kinetics and half-life of the atrazine in three soil were associated with atrazine partitioning, availability of mineral content (silica, aluminum, and iron), and soil microbial biomass carbon. Biochar amendment significantly reduced the plateau in the kinetic curve and also reduced the atrazine toxicity on soil microbiota. Overall, biochar was more effective in sandy clay soil for the restoration of soil microbial activities under atrazine stress due to modulation in the pH and more improved soil quality.

Multi-soil-layering (MSL) system was developed as an attractive alternative to traditional land-based treatment techniques. Within MSL system, the environmental cleanup capability of soil is maximized, while the soil microbial communities may also change during operation. This study aimed to reveal the nature of biophysiological changes in MSL systems during operation. The species diversity in soil mixture blocks was analyzed using Illumina HiSeq sequencing of the 16S rRNA gene. The interactive effects of operating factors on species richness, community diversity and bacteria abundance correlated with COD, N and P removal were revealed through factorial analysis. The results indicated the main factors, aeration, bottom submersion and microbial amendment, had different significant effects on microbial responses. The surface area and porosity of zeolites in permeable layers decreased due to the absorption of extracellular polymeric substances. The findings were applied for the design and building of a full-size MSL system in field and satisfied removal efficiency was achieved. The results of this study can help better understand the mechanisms of pollutant reduction within MSL systems from microbial insights. It will have important implications for developing appropriate strategies for operating MSL systems with high efficiency and less risks.

Denitrifying bioreactors are recently-established agricultural best management practices with growing acceptance in the US Midwest but less studied in other agriculturally significant regions, such as the US Mid-Atlantic. A bioreactor was installed in the Virginia Coastal Plain to evaluate performance in this geographically novel region facing challenges managing nutrient pollution. The 25.3 m3 woodchip bed amended with 10% biochar (v/v) intercepted subsurface drainage from 6.5 ha cultivated in soy. Influent and effluent nitrate-nitrogen (NO3–N) and total phosphorus (TP) concentrations and flowrate were monitored intensively during the second year of operation. Bed surface fluxes of greenhouse gases (GHGs) nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2) were measured periodically with the closed dynamic chamber technique. The bioreactor did not have a statistically or environmentally significant effect on TP export. Cumulative NO3–N removal efficiency (9.5%) and average removal rate (0.56 ± 0.25 g m−3 d−1) were low relative to Midwest tile bioreactors, but comparable to installations in the Maryland Coastal Plain. Underperformance was attributed mainly to low NO3–N loading (mean 9.4 ± 4.4 kg ha−1 yr−1), although intermittent flow, periods of low HRT, and low pH (mean 5.3) also likely contributed. N removal rates were correlated with influent NO3–N concentration and temperature, but decreased with hydraulic residence time, indicating that removal was often N-limited. GHG emissions were similar to other bioreactors and constructed wetlands and not considered environmentally concerning. This study suggests that expectations of NO3–N removal efficiency developed from bioreactors receiving moderate to high NO3–N loading with influent concentrations exceeding 10–20 mg L−1 are unlikely to be met by systems where N-limitation becomes significant.

Cadmium (Cd) contaminated soils from the Mae Sot district in northwest Thailand, a region in which rice Cd concentrations often exceed health limits (0.4 mg/kg) set by the World Health Organisation, were examined for isotopically exchangeable Cd (Cd E values using a 111Cd spike) to determine how this rates as a predictor of rice grain Cd in comparison with soil total Cd and solution extractable Cd (using the commonly applied BCR scheme and, in an attempt to distinguish carbonate bound forms, the Tessier soil sequential extraction scheme reagents). Step 1 of the BCR scheme (0.11 M CH3COOH) and step 1 of the Tessier scheme (1M MgCl2) showed the highest R2 values in regressions with rice Cd (91% and 90%, respectively), but all predictors were strongly linked to rice Cd (p

46 páginas, 2 tablas, 6 figuras. -- The definitive version is available at http://www.elsevier.com, Herbicides are essential in agricultural systems for maintaining crop yields, as weeds compromise grain production. Furthermore, the application of organic amendments to soil is an increasingly frequent agricultural practice for avoiding irreversible soil degradation. However, this practice could modify the behaviour of the herbicides applied, with implications for their absorption by weeds. This study evaluated the dissipation, persistence and mobility of the herbicides triasulfuron and prosulfocarb in a sandy clay loam soil unamended and amended with green compost (GC) in a field experiment using single or combined commercial formulations of both herbicides. The study was carried out in experimental plots (eight treatments × three replicates) corresponding to unamended soil and soil amended with GC, untreated and treated with the herbicide formulations Logran®, Auros® and Auros Plus® over 100 days. The half-life (DT50) of triasulfuron applied individually was 19.4 days, and increased in the GC-amended soil (46.7 days) due to its higher adsorption by this soil, although non-significant differences between DT50 values were found when it was applied in combination with prosulfocarb. Prosulfocarb dissipated faster than triasulfuron under all the conditions assayed, but non-significant differences were observed for the different treatments. The analysis of the herbicides at different soil depths (0–50 cm) after their application confirmed the leaching of both herbicides to deeper soil layers under all conditions, although larger amounts of residues were found in the 0–10 and 10–20 cm layers. The application of GC to the soil increased the persistence of both herbicides, and prevented the rapid leaching of triasulfuron in the soil, but the leaching of prosulfocarb was not inhibited. The influence of single or combined formulations was observed for triasulfuron, but not for prosulfocarb. The results obtained highlight the interest of obtaining field data to design rational joint applications of GC and herbicides to prevent the possible decrease in their effectiveness for weeds or the risk of water contamination., This work was funded by the Regional Government Junta de Castilla y León (project CSI240U14). V.B. and J.M.M.B. thank “Junta de Castilla y León” and MINECO by their predoctoral and postdoctoral “Juan de la Cierva-Incorporación” (JCI-2014-19538) contracts, respectively.

In recent decades, the innovative practice of management and valorization of agrozootechnical waste as energy through anaerobic digestion (AD) has been rapidly growing. However, whether applying digestate to soil as biofertilizer can be a source of antibiotics (ABs) and antibiotic resistance genes (ARGs) has not been fully investigated so far. In this work the ARGs responsible for sulfamethoxazole (SMX) resistance (sul1, sul2), ciprofloxacin (CIP) resistance (qnrS, qepA, aac-(6′)-Ib-cr) and the mobile genetic element intl1, together with the concentrations of the antibiotics SMX and CIP, were measured in several anaerobic digesters located in Central Italy. Based on these results, the concentrations of antibiotics and ARGs which can potentially reach soil through amendment with digestate were also estimated. The highest CIP and SMX concentrations were found during winter and spring in anaerobic digesters. The highest ARG abundances were found for the aac-(6’)-Ib-cr and sul2 genes. The overall results showed that application of digestate to soil does not exclude AB contamination and spread of ARGs in agroecosystems, especially in the case of ciprofloxacin, owing to its high intrinsic persistence.

The hyperaccumulating mechanism concerning heavy metal activation or passivation and plant response triggered by fulvic acid (FA) and humic acid (HA) recruitments are investigated herein. We carefully examine the Cd activation effect by various FA and HA, tracing from pig, goat, and duck manure composts to straw compost and commercial materials (i.e., PC, GC, DC, SC, and CM), as well as their roles in plant growth promotion and Cd uptake. Our results indicate that due to the decrease of soil pH and their multiple functional groups, the contents of available Cd (AE–Cd) increased by 4.3–4.8% and 3.6–6.3% when all FA and HA sources were applied for 30 days. A 13.1–19.9% increase in AE–Cd was observed when CFA, DFA, and PFA were applied for five days, and a 9.5% increment was found when PHA was applied for 10 days. In the pot experiment, the Cd accumulation in plants increased by 2.78 and 2.17 folds with PFA and PHA applications, respectively, compared to the blank control group. This result can be attributed to the stimulative effects of the simultaneous Sedum alfredii growth and Cd phytoavailability. Notably, the Cd accumulation increased by 2.26 times with the SFA amendment due to the predominant stimulation effect to the phytoavailable Cd rather than plant growth. However, slight inhibitory effects were observed upon plant growth or Cd uptake, which led to the reduction of the Cd accumulation with DHA, SHA, and CHA employments. Consistently, the corresponding soil Cd removal efficiencies were 43.5% and 34.6% with PFA and PHA, respectively, which hold abundant O- and N-containing groups. Our research aims to gain insights into the ternary interaction in the presence of heavy metal, humic substances, and S. alfredii to simultaneously accelerate Cd activation and hyperaccumulation.

Composting and vermicomposting have attracted attention in relation to both waste management and the potential to produce organic amendments that could improve soil quality. The main differences between compost depend on the feedstock, the production process, and the degree of maturity. In the present study, samples of compost of different origin (food and green waste, livestock waste, algae waste, urban waste or sewage sludge) or subjected to different composting methods (traditional or using earthworms) were collected for analysis. Additionally, samples collected at various stages of the composting process were compared (raw material, 15 and 30 days of composting, and final compost). Different analysis and techniques were used to establish the chemical composition, physicochemical and acid-base properties of compost samples and the organic matter extracts. The correlations obtained (between the abundance of acid groups in different extracts of the compost or between the cation exchange capacity and the C/N atomic ratio) would allow for predicting the compost behaviour based on certain characteristics, and a reduction in the number of parameters determined experimentally, thus facilitating comparisons between different compost. In addition, the potential value of the compost as amendment was tested with a Haplic Cambisol from a mining area. The application of compost increased the pH, the organic matter and nutrient content, and promoted seed germination and root growth.

Oil palm trunks (OPT) are logged for replantation and the fiber residues are disposed of into the palm plantation area. The fiber residues are expected to increase soil fertility through recycling of carbon and minerals via fiber decomposition. This study investigated the effects of OPT fiber disposal and other lignocellulosic biomass on plant growth and microbial diversity in the soil environment. Four treatment plots were tested: (A) soil+OPT fiber (1:20), (B) soil+sugarcane bagasse (1:20), (C) soil+cellulose powder (1:20), and (D) unamended soil as a negative control. Low plant height, decreased chlorophyll content, and low biomass was observed in corn grown on soil mixed with OPT fiber, cellulose, and sugarcane bagasse, when compared with those of the control. The plants grown with OPT fiber were deficient in total nitrogen and magnesium when compared with those without fiber amendment, which suggested that nitrogen and minerals in soil might be taken up by changing microflora because of the OPT fibers presence. To confirm differences in the soil microflora, metagenomics analysis was performed on untreated soil and soil from each lignocellulose treatment. The microflora of soils mixed with OPT fiber, cellulose and sugarcane bagasse revealed substantial increases in bacteria such as families Cytophagaceae and Oscillospiraceae, and two major fungal genera, Trichoderma and Trichocladium, that are involved in lignocellulose degradation. OPT fiber resulted in a drastic increase in the ratios and amounts of Trichocladium in the soil when compared with those of cellulose and sugarcane bagasse. These results indicate that unregulated disposal of OPT fiber into plantation areas could result in nutrient loss from soil by increasing the abundance of microorganisms involved in lignocellulose decomposition.

This study set out to evaluate the effect of using sewage sludge-derived compost (SSC) or biochar (SSB) as a soil amendment on the phytoaccumulation of potentially toxic elements, PTE (Cd, Cr, Cu, Ni, Pb, Zn) and natural radionuclides (U-238 and Th-232) by Chinese cabbage (Brassica rapa L. subsp. pekinensis (Lour.) Hanelt) in terra rossa and rendzina soils, which are the two common soil types in Croatia. The experiment consisted of a greenhouse pot trial using a three-factor design where soil type, sludge post-stabilisation procedure and amendment rate (12 and 120 mgP/L) were the main factors. At harvest, the concentrations of analytes in the substrate, leaves and roots were measured, from which the edible tissue uptake (ETU) and concentration ratios (CR) were determined. Also, the average daily dose (ADD) and hazard quotient (HQ) were determined to assess the health risk, as well as soil contamination factor (CF). The results showed that neither adding SSC nor SSB affected the soil loading at the rates applied, suggesting a low risk of soil contamination (CF ≤1). The ETU of Cd, Cu, and Zn were 0.0061, 1.23, and 0.91 mg/plant from compost-amended soil and 0.0046, 0.78 and 0.65 mg/plant for biochar-amended soil, respectively. This difference suggests that their ETU was higher in compost-amended soils than in soils treated with biochar. The CR data indicate that the bioavailability of Cu (CR of 5.30) is highest at an amendment rate of 12 mgP/L, while for Zn (CR of 0.69), the highest bioaccumulation was observed with an amendment rate of 120 mgP/L. Translocation of Cr, Ni, Pb and 238U to the leaves was limited. Overall, the HQ (

The last decade has seen a growing interest in applying activated carbon (AC)-based amendments for in situ subsurface remediation of organic contaminants such as chlorinated solvents and petroleum hydrocarbons. This remedial technology has been promoted by several major AC-based product vendors on the market. These products involve impregnation or co-application of chemical or biological additives to facilitate various contaminant degradation processes in conjunction with contaminant adsorption. During field applications, rapid contaminant removal and limited rebound after emplacement have often been reported and considered as two major advantages for this remedial technology. Nevertheless, questions remain to be answered regarding its true effectiveness and longevity given the lack of subsequent field characterizations and evidence of the degradation process, especially biodegradation. Additional uncertainties reside in how subsurface heterogeneity may affect the design, implementation and performance monitoring of this technology. In light of these uncertainties, this review presents an independent analysis that focuses on both the scientific and practical aspects of AC-based remedial technology for in situ subsurface remediation by gathering and synthesizing the scientific knowledge and practical lessons from a broad range of contaminant removal processes involving adsorption and/or degradation. The analysis showed that the scientific soundness of combining adsorption and degradation proposed for all the AC-based products is well supported by the literature on ex situ treatment. However, the in situ effectiveness might be affected by additional factors, such as geological heterogeneity, amendment transport and distribution, and total contaminant mass, which require more thorough and quantitative evaluation. Overall, the technology may provide a viable tool in addressing major remediation challenges encountered in current practice, such as mitigation of back diffusion from residual sources in low permeability zones and treatment of low concentration plumes.

The effects of adding two winery wastes, perlite waste (PW) and bentonite waste (BW), to an acid vineyard soil were assessed using some chemical and biological soil properties in a field study that lasted 18 months. The addition of PW (up to 81 Mg ha −1 ) had neither significant nor permanent effects on soil characteristics such as the pH, organic matter content or nutrient concentrations, the amounts of copper or zinc, or the electrical conductivity. Moreover, no persistent negative effects were found on the enzymatic activities after PW application. In contrast, soil that was amended with up to 71 Mg BW ha −1 showed increases in its soil pH values, exchangeable potassium and water soluble potassium and phosphorus contents. In addition, it caused significant increases in the electrical conductivity and water-soluble Cu. In addition, the phosphomonoesterase enzymatic activity decreased significantly (up to 28%) in response to the amendment with 71 Mg BW ha −1 . These results showed that adding BW and PW to the soil may be a good agronomic practice for recycling these types of wastes. However, in the case of PW, its use as a soil amendment must be performed with caution to control its possible harmful effects.

We investigated the potential of C-rich byproducts to replace wood chips as bulking agent (BA) during composting. The impact of these alternatives on the composting process and on compost stability and characteristics was assessed. Three BA (chopped heath biomass and spent growth media used in strawberry and tomato cultivation) were used for processing leek residues in windrow composting. All BA resulted in stable composts with an organic matter (OM) content suitable for use as soil amendment. Using chopped heath biomass led to high pile temperatures and OM degradation and a nutrient-poor compost with high C/P ratio appropriate for increasing soil organic carbon content in P-rich soils. Spent substrates can replace wood chips, however, due to their dense structure and lower biodegradation potential, adding a more coarse BA is required. Generally, the nutrient content of the composts with growth media was higher than the composts with wood chips and chopped heath biomass.

Coal fly ash (CFA) is a problematic solid waste all over the world. One distinct beneficial reuse of CFA is its utilization in land application as a soil amendment. A pot experiment was carried out to assess the feasibility of using CFA to improve plant growth and increase the supply of plant-essential elements and selenium (Se) of a loessial soil for agricultural purpose. Plants of alfalfa (Medicago sativa) were grown in a loessial soil amended with different rates (5%, 10%, 20% and 40%) of CFA for two years and subjected to four successive cuttings. Dry mass of shoots and roots, concentrations of plant-essential elements and Se in plants were measured. Shoot dry mass and root dry mass were always significantly increased by 5%, 10% and 20% CFA treatments, and by 40% CFA treatment in all harvests except the first one. The CFA had a higher supply of exchangeable phosphorus (P), magnesium (Mg), copper (Cu), zinc (Zn), molybdenum (Mo), and Se than the loessial soil. Shoot P, calcium (Ca), Mg, Mo, boron (B), and Se concentrations were generally markedly increased, but shoot potassium (K), Cu, and Zn concentrations were generally reduced. The CFA can be a promising source of some essential elements and Se for plants grown in the loessial soil, and an application rate of not higher than 5% should be safe for agricultural purpose without causing plant toxicity symptoms in the studied loessial soil and similar soils. Field trials will be carried out to confirm the results of the pot experiment.

Over three million tonnes of spent mushroom substrate (SMS) are produced in Europe every year as a by-product of the cultivation of Agaricus bisporus. The management of SMS has become an increasing challenge for the mushroom production industry, and finding environmentally and economically sustainable solutions for this organic residue is, therefore, highly desirable. Due to its physical properties and nutrient content, SMS has great potential to be employed in agricultural and horticultural sectors, and further contribute to reduce the use of non-renewable resources, such as peat. However, SMS is often regarded as not being stable and/or mature, which hampers its wide use for crop production. Here, we demonstrate the stabilisation of SMS and its subsequent use as organic fertiliser and partial peat replacement in horticulture. The stabilisation was performed in a laboratory-scale composting system, with controlled temperature and aeration. Physical and chemical parameters were monitored during composting and provided information on the progress of the process. Water soluble carbohydrates (WSC) content was found to be the most reliable parameter to predict SMS stability. In situ oxygen consumption indicated the main composting phases, reflecting major changes in microbial activity. The structure of the bacterial community was also found to be a potential predictor of stability, as the compositional changes followed the composting progress. By contrast, the fungal community did not present clear successional process along the experiment. Maturity and quality of the stabilised SMS were assessed in a horticultural growing trial. When used as the sole fertiliser source, SMS was able to support Lolium multiflorum (Italian ryegrass) growth and significantly improved grass yield with a concentration-dependent response, increasing grass biomass up to 300%, when compared to the untreated control. In summary, the results indicated that the method employed was efficient in generating a stable and mature product, which has a great potential to be applied in horticulture. This study represents a step forward in the management of SMS residue, and also provides an alternative to reduce the use of peat in horticulture, alleviating environmental impacts to peatland ecosystems.

Organic fertilization can preserve soil organic matter (SOM) and is foreseen as an effective strategy to reduce green house gases (GHGs) emissions in agriculture. However, its effectiveness needs to be clarified under specific climate, crop management and soil characteristics. A field experiment was carried out in a Mediterranean drip irrigated maize system to assess the pattern of soil CO2 and N2O fluxes in response to the replacement of a typical bare fallow–maize cycle under urea fertilization (130 kg N ha−1 y−1) (CONV) with: (i) bare fallow-maize cycles under two doses of compost (COM1 and COM2, 130 and 260 kg N ha−1 y−1, respectively) and (ii) a vetch-maize cycle, with vetch incorporation as green manure (130 kg N ha−1 y−1) (GMAN). Along the maize period (MP), reduced daily N2O emissions were detected in organic treated soils compared to CONV, mainly in the first stages of the cultivation, thanks to the slow release of available nitrogen from the organic substrates. Cumulative N2O fluxes (kg N2O-N ha−1) in MP scored to 0.24, 0.14, 0.12 and 0.085 for CONV, COM1, COM2 and GMAN, respectively, with significantly lower emissions in GMAN respect to CONV. CO2 fluxes partially reflected the ranking observed for maize yields, with cumulated values (Mg CO2-C ha−1) of 2.2, 1.5, 2.1, 2.1 for CONV, COM1, COM2 and GMAN, respectively, and significantly lower in COM1 respect to the other treatments. During the fallow period (FP), compared to CONV (0.77 Mg CO2-C ha−1 and 0.25 kg N2O-N ha−1), enhanced GHG fluxes were detected in COM treatments (about 0.90 Mg CO2-C ha−1 and 0.37 kg N2O-N ha−1, as averaged values from COM1 and COM2), likely driven by the slow prolonged mineralization of the added organic matter. GMAN showed comparable CO2 (0.82 Mg CO2-C ha−1) and N2O emissions (0.30 kg N2O-N ha−1), in consequence of restrained post-harvest residual N coupled with the counteracting effect of vetch uptake. Respect to the total yearly GHG emissions in CONV (about 194 kg CO2 eq ha−1 y−1), the overall results showed commensurate slightly higher GWP in COM treatments (+11% as averaged value from COM1 and COM2). The yield-scaled global warming potential (GWP) resulted 60% higher and nearly doubled for COM2 and COM1 respectively, according to the lower COM yields, markedly dampening at halved compost dose. GMAN appeared the best performing organic treatment, with lower GWP (−27%) and competitive yields respect to CONV. All treatments showed N2O emission factors consistently lower compared with the default IPCC 1% value.

In the present study, various co-composts of sewage sludge (SS), farm manure (FM) and rock phosphate (RP) were prepared and their influence on phosphorus (P) uptake, soil P restoration and growth of rice crop and residual effect on wheat crop were investigated. The treatments comprised of T1 (control, no amendment), T2 (452 kg Nitrophos ha−1, T3 (724 kg SS50:FM50 ha-1), T4 (594 kg SS100:FM0 ha−1), T5 (728 kg SS25:FM25:RP50 ha−1), T6 (726 kg SS5O:FM25:RP25 ha-1), T7 (508 kg SS75:FM0:RP25 ha−1), and T8 (546 kg SS50:FM0:RP50 ha−1). The post-experimental soil samples were analyzed for pH, EC, OM, Olsen's P. The plant samples (grains and straw of both crops) were analyzed for concentrations of P, and heavy metals. The P adsorption by post-wheat composts-amended soil was tested through Langmuir, and Freundlich adsorption isotherms. The investigated parameters (biomass, grain and straw yield, plant height and P concentrations in plant parts) were significantly increased in all composts as compared to the control treatment. The P uptake by the plants was higher in compost treatments as compared to the control and NP that shows long-term residual effect of applied composts. The maximum grain yield (1.63 Mg ha−1) was obtained in T5 followed by T6 (1.52 Mg ha−1). The P concentration in rice grains were recorded in the trend as T8 (2.55%) > T6 (2.24%) > T4 (1.92%) = T3 (1.88%) > T7 (1.62%). It is evident that the combined application of FM (25%) and RP (50%) enhanced the effect of SS (25%) in terms of P bioavailability and yield parameters and can be effectively used as P fertilizer.

Metals that contaminate soil is one of the major problems seriously affecting sustainable agriculture worldwide. Nickel (Ni) toxicity to agricultural crops is a global problem. Mobility of heavy metals present in contaminated soil can be reduced by the amendment of soil passivators, which will ultimately reduce the risk of them entering the food chain. A greenhouse pot experiment was conducted to investigate the effects of rice straw (RS), biochar derived from rice straw (BI) and calcium carbonate (calcite) on Ni mobility and its up take by maize (Zea maize L.) plant. Maize crop was grown in Ni spiked (100 mg kg−1) soil with three application rates of passivators (equivalent to 0, 1and 2% of each RS, BI and calcite) applied separately to the soil. Results revealed that the post-harvest soil properties (pH, DOC and MBC), plant phenology (plant height, root length, total dry weight) and physiological characteristics were significantly enhanced with passivator application. Additionally, incorporating passivator into the soil reduced Ni mobility (DTPA) by 68%, 88.9% and 79.3%, and leachability (TCLP) by 72.4%, 76.7% and 66.7% for RS, BI and calcite, respectively at 2% application rate. The Ni concentration in the maize shoots reduced by 30%, 95.2% and 95% and in the roots by 56%, 66% and 63.8% with RS, BI and calcite at 2% application rate, respectively. These findings suggest that the application of 2% biochar (BI) is very promising in reducing Ni uptake, and can reduce toxicity to plants, decrease mobility and leachability in the soil.

The use of zeolite as a geo-engineering tool has a high potential to control nitrogen (N) release from sediments, but its efficiency for controlling sedimentary phosphorus (P) release still need to be further increased. To address this issue, this work synthesized an iron-modified zeolite (IM-Z) by coating iron onto the surface of natural zeolite (NAT-Z) and then the as-obtained IM-Z was utilized as a geo-engineering material to block the upward mobilization of N and P from sediments to the overlying water. The efficiencies of IM-Z covering and amendment to prevent the liberation of N and P from sediments were evaluated, and the controlling mechanism was explored. Capping and amendment with IM-Z not only resulted in the tremendous reduction of the levels of ammonium-N (NH4+-N) and reactive soluble P (RSP) in the overlying water, but also led to the decrease of the contents of NH4+-N and RSP in the pore water. More importantly, sediment capping and amendment with IM-Z resulted in the formation of a static layer in the upper sediment directly below the sediment-water interface, with very low concentration of RSP in the pore water. In addition, IM-Z capping and addition effectively immobilized the diffusive gradients in thin films (DGT)-labile P in the overlying water and sediment. Furthermore, the decrease of the DGT-labile Fe concentrations in the overlying water as well as the top sediment were also observed after IM-Z capping and addition. Nearly 70% of P bound by IM-Z is stable and difficult to be released back into the overlying water under common pH and anoxic conditions. The adsorption of pore water NH4+-N on IM-Z, the immobilization of pore water RSP and DGT-labile P by IM-Z and the uptake of DGT-labile Fe on IM-Z played a significant role in the simultaneous control of NH4+-N and RSP liberation. Compared to NAT-Z, the efficiency of IM-Z to block the liberation of sedimentary P was higher. Results of this study demonstrate that IM-Z is suitable for use in the simultaneous interception of the upward transportation of NH4+-N and RSP from sediments into the overlying water.

peer-reviewed The full text of this article will not be available in ULIR until the embargo expires on the 31/07/2021 The secondary use of P-sorbing industrial by-products as a fertilizer or soil conditioner is gaining increased attention, particularly in light of diminishing reserves of rock phosphate traditionally used to manufacture P fertilizer. This study examined applications of red mud (RM) and water treatment residuals (WTR) at two levels of P saturation (i.e. ‘as received’ and partially saturated) in a soil incubation and runoff plot study. When incubated with soils ranging in texture and initial P concentration, P-sorbing residuals that were less enriched with P decreased water-extractable soil P (WEP) concentration to a greater extent than more P saturated residuals. In contrast to WTR treatments, not all of the RM applications decreased soil WEP concentrations below those of the control soils. The runoff study investigated soil P dynamics when partially P-saturated RM and WTR's were surface applied to grass plots at 2 t ha−1 on Day 0, followed by three rainfall simulations (7 cm h−1 for 30 min, Days 2, 7 and 28) and at 3 t ha−1 on Day 70 followed by two more rainfall simulations (Days 77 and 96). Application of residuals at these rates did not significantly increase dissolved reactive P (DRP) in runoff compared with unamended controls during the study. Forage cuttings taken 90 days after the first rainfall simulation indicated that nutrient uptake was not compromised by the application of the residuals. Overall results indicate that WTRs may be a more suitable soil amendment than RM residuals given their greater ability to reduce soil WEP across a range of soils without simultaneously increasing Mehlich-3 extractable soil P concentrations above the upper threshold limit (150 mg P kg−1), and their minimal impact on plant nutrient uptake. peer-reviewed

Biochar, a recalcitrant carbon, is known to enhance organic matter degradation and improve physical properties. The objective of the study is to examine the probable effect of biochar addition during composting of a fibrous aquatic waste, i.e., water hyacinth though degradation kinetics and spectroscopic (FTIR and PXRD) analysis. Four dosages of biochar (0, 2.5, 5, and 10% w/w) were mixed to a mixture of water hyacinth, cow-dung and saw-dust comprising a total weight of 150 kg and composted using rotary drum composter for 20 days in batch mode. The study outcomes indicated that the amendment of biochar prolonged the duration of the thermophilic temperatures, reduced salinity, and promoted nutritional quality of compost. Moreover, biochar amendment enhanced the organic matter degradation with a rate constant of 0.029 day−1 and increased the total Kjeldahl nitrogen content up to 1.75% from an initial value of 1.10% in the reactor with 2.5% biochar amendment. Concurrently, biochar amendment aided in reducing Cu and Cr in the final product inferring 2.5% biochar is best suited for composting of water hyacinth. However, future studies are encouraged to decipher the microbial shifts and bioavailability of metals due to biochar dosage during composting for mitigating and managing the menace of such fibrous waste like water hyacinth by converting it to a soil conditioner.