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Microplastics (MPs), especially biodegradable MPs (BMPs) have attracted increasing attention in recent years. However, the effects of MPs with different biodegradability on the soil-plant systems are not well explored. In this study, the effects of polyethylene MPs (PEMPs) and polylactic acid MPs (PLAMPs) on physio-biochemical performance and metabolomic profile of soybean (Glycine max), as well as the bacterial communities in soil were investigated. Our results showed that PEMPs had no noticeable toxicity on the plant growth, while 0.1% PLAMPs significantly decreased the root length by 27.53% when compared with the control. The peroxidase (POD) activity was reduced and catalase (CAT) activity was increased by MPs in plant leaves. The metabolomics study suggested that the significantly affected metabolic pathway is amino acid metabolism. Additionally, Shannon and Simpson indices of rhizosphere soil were changed only under 0.1% PLAMPs. The key bacteria involved in the dinitrogen fixation were also altered. This study provides a novel insight into the potential effects of MPs with different biodegradability on soil-plant systems and highlights that BMPs might have stronger negative effects for terrestrial ecosystem, which needs to be further explored in future research., (Copyright © 2022 Elsevier B.V. All rights reserved.)

A set of soil under the addition of ball-milled biochar (BM-biochar) from different feedstocks (wheat straw (WS) and rice husk (RH)) and pyrolysis temperature (300 °C, 500 °C, and 700 °C) was established to analyze the tetracycline (TC) degradation performance enhancement and greenhouse gas carbon dioxide (CO 2 ), and nitrous oxide (N 2 O) emission reduction from various angles, including physicochemical properties of soil and microbial community structure. After 45 days' incubation, the pH value decreased slightly from 7.34 to 7.22 for WS biochar-treated soil, while slightly increased from 7.34 to 7.50 for RH biochar-treated soil. The lowest KCl-leachable TC concentrations of BMWS700 and RH700 was about 0.0037 mg/L. Ball-milled 500 °C and 700 °C biochars enhanced the removal rate of TC significantly. The maximum reduction of TC was from 2.17 to 0.079 mg/kg, equivalent to 96% removal after ball-milled 500 °C wheat straw biochar (BMWS500) addition, suggesting the promoting effect of biochars on microorganisms for adsorption and degradation of TC. Biochars' addition reduced CO 2 and N 2 O emissions, BM-biochar enlarged this effect under the pyrolysis temperature 500 °C for both feedstock types. Ball milled rice husk biochar pyrolyzed under 500 °C (BMRH500) presented the maximum inhibitory effect CO 2 emission. The addition of BM-biochar changed the microbial community and diversity. The relative abundance of bacterium and fungus such as Proteobacteria, Acidobacteria, Chlorofexi, Mortierella, and Chaetomium increased due to BM-biochar addition, which promoted the degradation of TC and gave rise to more healthy soil environment for plant or microbes. The larger specific surface area, π-π interactions, hydrophobic interaction, and hydrogen bonding are account for better adsorption and degradation of TC by BM-biochars. This work elucidated the management of organic contaminants in real soil by BM-biochar., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Microplastics (MPs) are characterized by small particle sizes (<5 mm) and are widely distributed in the soil environment. To date, little research has been conducted on investigating the effects of MPs on the soil microbial community, which plays a vital role in biogeochemical cycling. In the present study, we investigate the influence of two particle sizes of MPs on dissolved organic carbon (DOC) and its relative functional groups, fluxes of greenhouse gases (GHGs), and the bacterial and fungal communities in fertilized soil. The results showed that a 5% concentration of MPs had no significant effect on soil DOC, whereas the formation of aromatic functional groups was accelerated. In fertilized soil, the existence of MPs decreased the global warming potential (GWP) as a result of a reduction in N 2 O emissions during the first three days. A potential mechanism for this reduction in N 2 O emissions might be that MPs inhibited the phylum Chloroflexi, Rhodoplanes genera, and increased the abundance of Thermoleophilia on day 3. An increase in N 2 O emissions was observed on day 30, mainly due to the acceleration of the NO 3 - uptake was significantly correlated with Hyphomicrobiaceae on day 3 and Rhodomicrobium on day 30. In soil with MPs, Actinobacteria replaced Proteobacteria as the dominant phylum. Larger MPs increased the richness (Chao1) and abundance-based coverage estimators (ACE) and diversity (Shannon) of the bacterial community on day 3, whereas these decreased on day 30. The richness and diversity of the fungal community were also reduced on days 3 and 30. Smaller MPs increased the community richness and diversity of both bacterial and fungal communities in fertilized soil. Our findings suggest that MPs have selective effects on microbes and can potentially have a serious impact on terrestrial biogeochemical cycles.4 uptake was significantly correlated with Hyphomicrobiaceae on day 3 and Rhodomicrobium on day 30. In soil with MPs, Actinobacteria replaced Proteobacteria as the dominant phylum. Larger MPs increased the richness (Chao1) and abundance-based coverage estimators (ACE) and diversity (Shannon) of the bacterial community on day 3, whereas these decreased on day 30. The richness and diversity of the fungal community were also reduced on days 3 and 30. Smaller MPs increased the community richness and diversity of both bacterial and fungal communities in fertilized soil. Our findings suggest that MPs have selective effects on microbes and can potentially have a serious impact on terrestrial biogeochemical cycles., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Genes that encode for enzymes that can degrade petroleum hydrocarbons (PHs) are critical for the ability of microorganisms to bioremediate soils contaminated with PHs. Distributions of two petroleum-degrading genes AlkB and Nah in soils collected from three zones of the Dagang Oilfield, Tianjin, China were investigated. Numbers of copies of AlkB ranged between 9.1 × 10(5) and 1.9 × 10(7) copies/g dry mass (dm) soil, and were positively correlated with total concentrations of PHs (TPH) (R(2) = 0.573, p = 0.032) and alkanes (C33 ~ C40) (R(2) = 0.914, p < 0.01). The Nah gene was distributed relatively evenly among sampling zones, ranging between 1.9 × 10(7) and 1.1 × 10(8) copies/g dm soil, and was negatively correlated with concentrations of total aromatic hydrocarbons (TAH) (R(2) = -0.567, p = 0.035) and ∑16 PAHs (R(2) = -0.599, p = 0.023). Results of a factor analysis showed that individual samples of soils were not ordinated as a function of the zones.

Biochar is produced by thermal decomposition of biomass under oxygen-limited conditions (pyrolysis), and it has received attention in soil remediation and waste disposal in recent years. The characteristics of biochar are influenced mainly by the preparation temperature and biomass. Higher pyrolysis temperature often results in the increased surface area and carbonized fraction of biochar leading to high sorption capability for pollutants. Biochars derived from various source materials show different properties of surface area, porosity and the amount of functional groups which are important concerning on the effect of biochar. Biochar has been proved to be effective in improving soil properties and increasing crop biomass. It has also been suggested that it can even enhance crop resistance to disease. Biochar has recently been used to remediate soil with both heavy metal and organic pollutants. The mechanism is electrostatic interaction and precipitation in the case of heavy metal, and the surface adsorption, partition and sequestration in the case of organic contaminants. However, application of biochar in soil has been shown to result in decreased efficacy of pesticides, which indicates a trade-off between the potentially promising effect of biochar on pesticide remediation and its negative effect on pesticide efficacy. While arguments on the effectiveness of biochar appear sound, further research is needed prior to widespread application of biochar in soil remediation., (Copyright © 2013 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.)

Total petroleum hydrocarbons (TPH) contaminated soil samples were collected from Shengli Oilfield of China. Toxicity analysis was carried out based on earthworm acute toxicity, plant growth experiment and luminescent bacteria test. The soil was contaminated by-petroleum hydrogcarbons with TPH concentration of 10.57%. With lethal and sub-lethal rate as endpoint, earthworm test showed that the LD50 (lethal dose 50%) values in 4 and 7 days were 1.45% and 1.37% respectively, and the inhibition rate of earthworm body weight increased with higher oil concentration. TPH pollution in the soil inhibited seed germination in both wheat and maize experiment when the concentration of petroleum was higher than 0.1%. The EC50 (effective concentration 50%) for germination is 3.04% and 2.86% in maize and wheat, respectively. While lower value of EC50 for root elongation was to be 1.11% and 1.64% in maize and wheat, respectively, suggesting higher sensitivity of root elongation on petroleum contamination in the soil. The EC50 value in luminescent bacteria test was 0.47% for petroleum in the contaminated soil. From the experiment result, it was concluded that TPH content of 1.5% is considered to be a critical value for plant growth and living of earthworm and 0.5% will affect the activity of luminescent bacteria.

Rapid industrialization and urbanization have resulted in elevated concentrations of hazardous inorganic and organic contaminants in groundwater and soil, which has become a paramount concern to the environment and the public health. In recent years, iron sulfide (FeS), a major constituent of acid-volatile sulfides, has elicited extensive interests in environmental remediation due to its ubiquitous presence and high treatment efficiency in anoxic environment. This paper provides a comprehensive review on recent advances in: (1) synthesis of FeS particles (including nanoscale FeS); and (2) reactivity of FeS towards a variety of common environmental contaminants in groundwater and soil over extended periods of time, namely, heavy metals (Hg(II), Cu(II), Pb(II), and Cr(VI)), oxyanions (arsenite, arsenate, selenite, and selenate), radionuclides (e.g., uranium (U) and neptunium (Np)), chlorinated organic compounds (e.g., trichloroethane, trichloroethylene, and p -chloroaniline), nitroaromatic compounds, and polychlorinated biphenyls. Different physiochemical and biological methods for preparing FeS with desired particle size, structure, and surface properties are discussed. Reaction principles and removal effectiveness/constraints are discussed in details. Special attention is placed to the application of nanoscale FeS particles because of their unique properties, such as small particle size, large specific surface area, high surface reactivity, and soil deliverability in the subsurface. Moreover, current knowledge gaps and further research needs are identified. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, aging process of petroleum-contaminated soil was characterized during 210d of attenuation under different conditions: clean soil spiked with petroleum (Run 1), clean soil spiked with petroleum and humic acid (Run 2), quartz sand spiked with petroleum (Run 3) and petroleum-contaminated saline soil from an oil field (Run 4). An initial increase of pH was found before 60d of aging. Total petroleum hydrocarbon (TPH) content decreased with the process of aging and the degradation rates for the 4 runs were 61%, 60%, 24% and 20% after 210d of aging, respectively. The saturated fraction of petroleum hydrocarbons was most degraded in Run 1 in clean soil; while addition of humic acid enhanced the degradation of aromatic fraction and asphaltene and polar fraction. Addition of TPH in soil resulted in the increase of the dehydrogenase activity at the initial period of aging. A significant negative correlation was found between bacteria count and TPH content during aging process and fungi number was only increased at certain time of aging. The biological toxicity increased at the middle of aging process of 30–60d as determined by plant growth and luminescent bacteria experiment. The result suggested that proper regulation on the influencing factors such as particle size and salinity was important for the management of contaminated soils and could enhance the natural attenuation of the petroleum pollutants. [Copyright &y& Elsevier]

Cadmium (Cd) pollution in the suburbs of Tianjin, China, was monitored over a period of several years. During this period, 193 soil, 120 vegetable, and 71 rice samples from four suburban districts were analyzed. The Cd content of the soil samples was considerably higher than the background level. Some soil samples from the Dongli and Xiqing districts were even in the S5 (Heavy) and S6 (Severe) pollution levels, with a maximum concentration of 5.20 mg kg−1. The Cd contents of vegetable and rice samples were found to be in the F3 (Intermediate) and F4 (Heavy) pollution levels. Vegetables showed differing abilities to accumulate Cd and can be ranked in the following order: leaf vegetables > rootstalk vegetables > fruit vegetables. The average Cd level in different vegetables ranged from 0.0064 to 0.132 mg kg−1, and a positive relationship (p < 0.05) was found between soil and plant Cd contents. Chinese cabbage and celery were more likely to pose risks to human health, as shown by their higher hazardous quotient (HQ) values. The soil Cd pollution in Tianjin seemed primarily to be caused by wastewater irrigation and the application of sewage sludge to farmlands. Other possible sources include the use of phosphate fertilizer and atmospheric deposition. [ABSTRACT FROM AUTHOR]

Biochar/iron (BC/Fe) composites, such as nano zero-valent iron (nZVI)/BC, iron sulfide/BC, and iron oxide/BC, have been developed and applied to deal with various contaminants owing to their excellent physicochemical properties. This work summarizes the progress in the preparation of BC/Fe composites, the properties and applications of BC/Fe, and the mechanism of the synergistic effect between Fe and BC in the composites. Various methods, including pyrolysis, hydrothermal carbonization, fractional precipitation, and ball milling, have been used to synthesize BC/Fe composites. In addition, the introduction of stabilizers, such as carboxymethyl cellulose (CMC), in the fractional precipitation process further prevents the agglomeration of Fe particles, which enhances the stability and fluidity of the resultant composites to facilitate the application of the composites in soil and water remediation. The application of BC/Fe composites in water and soil remediation is discussed in three aspects based on the interaction mechanisms, namely adsorption, reduction, and oxidation. Overall, the composites showed the synergistic effect of BC and Fe owing to the combination of the specific properties of Fe, such as reduction, catalysis, and magnetism, which can enhance the properties of BC with a larger surface area, abundant functional groups, and increased electron transfer efficiency. This review systemically summarizes the recent developments in BC/Fe composites to maximize the efficiency of BC/Fe application in soil and groundwater remediation. Key challenges and further research needs are also suggested. Image 100 • BC/Fe composites can be divided into three types based on their functions. • Synthesis methods play an important role in the combination of BC and Fe. • This review reveals the mechanism of the synergistic effect between Fe and BC. • This review maximizes the efficiency of BC/Fe application. [ABSTRACT FROM AUTHOR]

Soil mercury contamination poses health risks. However, effective immobilization techniques are lacking with challenges including low efficiency, limited long-term stability, susceptibility to multi-medium interference, and difficulty in controlling health risks. This study confirmed the feasibility of thiol-modified biochar, and elucidated the underlying mechanisms. Within 32 days of treatment, the leachable mercury decreased from 184.7 μg/L to below the hazardous waste threshold (100 μg/L, HJ/T299–2007, China). After 198 days of treatment, the soil achieved a safe ecological state with a mercury immobilization rate of 79.8–98.2% and a 50% reduction in available methylmercury. Thiol-modified biochar facilitated the conversion of active mercury species (exchangeable, carbonate, and oxide) into stable forms (organic and residual) through complexation and precipitation (e.g., HgS). Soil quality improvements were observed, including enhanced cation exchange capacity, available nitrogen, and total organic carbon. Thiol-modified biochar exhibits long-term effectiveness. After one and two years of treatment, the leachable mercury remained within acceptable health risk limit (hazard quotient < 1) for adults and children, respectively. After three years, the leachable mercury met the Level III groundwater quality standard (< 1 μg/L, GB 14848–2017, China). This study demonstrates an effective strategy for long-term diminishing mercury mobility and health risks in soil. [Display omitted] • Thiol-modified biochar effectively reduces the mobility of mercury in soil. • Mercury is mainly immobilized in organic-bound and residual fractions. • Multilayer structures trap more mercury than porous structures. • Ecological and health risks of mercury decrease with improved soil fertility. • Mercury immobilization exhibits long-term stability. [ABSTRACT FROM AUTHOR]

The impact of micro- and nanoplastics (M/NPs) on terrestrial ecosystems has been a hot topic in recent years since the soil has been recognized as an important sink for M/NPs. In the current study, a CiteSpace-based scientometric analysis of 506 papers was performed to show the intellectual background, research performance, and state of art knowledge structure of M/NPs in the terrestrial environment over the past six years (2016 - January 2022). The most prolific publications, journals, authors, and countries involved in the flourishment of this field were identified. Additionally, visualization methods were employed to determine the highly productive keywords, hotspots, and research frontiers in the field of M/NPs in terrestrial environments. Furthermore, cluster analysis was performed to provide an accurate summary of this field by exploring the sub-domains of this field. China has proven to be the most prominent country among others in terms of publications and funding. This study can help researchers identify new research fronts and distinguish the most critical sub-domains of M/NPs in the terrestrial environment research. [Display omitted] • Scientometric analysis of micro- and nanoplastic in terrestrial ecosystem was done. • Sub-domains of this field were extracted through knowledge structuring. • Publications in this field increased by 8533.3% in 2021 relative to 2016. • China was the most prominent country in terms of publication and funding. • Studies about the trophic transfer of M/NPs should be considered in future. [ABSTRACT FROM AUTHOR]