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In this study, a 30-day incubation experiment was performed to investigate the interactive effects of soil moisture content and two types of organic manure (animal manure: M and wheat straw: WS) on organic C mineralization and the degradation of PAH compounds. Specifically, washed sandy soil sample free from PAHs was treated with combined standard solution containing six different PAHs; pyrene (Pyr), fluoranthene (Flt), benzo[a]pyrene (BaP), benzo[g,h,i]perylene (BghiP), benzo[k]fluoranthene (BkF), and indeno[123-cd]pyrene (IP). The soil samples treated with PAHs were amended with M or WS and then, the soil samples were incubated and subjected to two levels of moisture content (50% and 100% field capacity, FC). The results indicate that CO2–C rates were the highest at day 1, but they tended to be decreased sharply when incubation time increased. The results showed that the higher rate of CO2-C efflux rate and cumulative were observed in M and WS treatments at 100% FC. Applying organic amendments at 50% FC increased the total cumulative CO2-C from 21.6 mg kg−1 to 228 mg kg−1 for M and to 216 mg kg−1 for WS. Meanwhile, applying organic amendments at 50% FC increased the total cumulative CO2-C from 30 mg kg−1 to 381 mg kg−1 for M and to 492 mg kg−1 for WS. The highest increases at 100% FC could be explained by the optimum water content at field capacity. PAHs concentrations decreased significantly in the presence of organic amendments in relation to enhance CO2-C efflux (soil respiration) and to decrease soil pH. It could be concluded that applying organic amendments might be a useful technique to remediate soil PAHs through mineralization. [ABSTRACT FROM AUTHOR]

Polymer-clay composites were prepared by natural zeolite (clinoptilolite) or naturally local clay deposits in an N,N-methylene-bis-acrylamide as cross-linked. The resultant composites were used for the removal of Cr(VI) from an aqueous solution. Additionally, their effects on soluble ions of tannery wastewater were investigated. The produced composites were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM). The results showed that Cr(VI) removal is dependent upon initial concentrations and pH. The adsorption quantity of Cr(VI) onto the polymerized clay deposit followed by polymerized zeolite exhibited higher values than their original samples. The polymer-clay composite of clay deposit showed the highest removal of 76.3-100% overall initial concentrations of 10-50 mg L-1 and at initial pH of 2. Kinetics of Cr(VI) removal by various sorbents was predicted using a pseudo-second order model. Our findings showed that the levels of salinity and various soluble ions (Cr2+, Na+, Cl- and SO42-) in tannery wastewater are very high, and their levels were reduced after treatment, especially by polymerized sorbents. It could be concluded that the polymer-clay composites may be employed as a highly efficient sorbent for the removal of Cr(VI) and toxic ions from the wastewater. [ABSTRACT FROM AUTHOR]

Biochar has an ability to alter the biological, chemical, and physical properties of soil due to its physicochemical properties such as surface area, porosity, nutrient retention ability, available nutrient contents, aromaticity, etc. The present study was designed to evaluate the impact of physical properties and application rate of biochar on the hydraulic properties of a sandy loam soil in the short term. Biochar was produced at 500 °C from dried corn residue (BC500). The BC500 was incorporated at the rates of 0, 2.5%, 5.0%, 7.5%, and 10% (w.w-1) into the sandy loam soil and filled up to a height of 4 cm, in cores having 5 cm diameter and height. Each treatment was performed in triplicate and equilibrated for 30 days. Then saturated hydraulic conductivity (Ksat), water holding capacity (WHC), and bulk density were determined in each sample after four days of saturation at room temperature in a water bath. The BC500 particle size distribution, pores, and surface functional groups were assessed. The Ksat exhibited a highly significant exponential reduction from 0% to 7.5% of BC500 application and approached an asymptote at 10% BC500. Bulk density showed a significant negative correlation to biochar application rate. The WHC and BC500 application rate illustrated a strong positive relationship. Biochar surface was free from hydrophobic functional groups. The addition of BC500 has a positive influence on soil hydraulic properties, primarily due to the increased soil porosity. The BC500 is composed of a microporous structure and hydrophilic surface that retain water in sandy textured soils. The application of BC500 would be a wise investment to maximize the water use efficiency in soils for agricultural production. [ABSTRACT FROM AUTHOR]

Conocarpus pruning waste, an agricultural byproduct, was converted into low-cost activated and non-activated carbons and used for the remediation of Cd2+, Cu2+, and Pb2+ from aqueous solutions. The carbonization was carried out at 400 °C, while the activation was carried out in the presence of KOH and ZnCl2. Batch single-solute and multi-solute equilibrium and kinetic experiments were carried out to determine the adsorption capacities of the prepared activated and non-activated carbons, and these were further compared with commercially available activated carbon. The results showed that KOH-activated carbon (CK) outperformed the other activated and non-activated carbons in terms of adsorption efficiency. CK removed >50% of the applied Cd2+ and Cu2+ and 100% of Pb2+ at the initial concentration of 40 mg L-1. Interestingly, the performance of Conocarpusderived non-activated carbon was better than that of the commercial activated carbon, as observed from the Langmuir maximum adsorption capacities of 65.61, 66.12, and 223.05 µmol g-1 for Cd2+, Cu2+, and Pb2+, respectively. The Pb2+ was the metal most easily removed from aqueous solution because of its large ionic radius. The kinetic dynamics were well described by the pseudo-second order and Elovich models. [ABSTRACT FROM AUTHOR]

Biochar, an alkaline carbonaceous substance resulting from the thermal pyrolysis of biomass, reportedly enhances the micronutrient availability in acidic soils with little or no effect on alkaline soils. In this study, biochars were produced from poultry manure (PM) at 350 °C and 550 °C (BC350 and BC550 respectively). The acidified biochars (ABC350 and ABC550, respectively) were incorporated into an alkaline sandy soil, and their effects on the soil micronutrients (Cu, Fe, Mn and Zn) availability, and CO2–C efflux were investigated in a 30-day incubation study. The treatments (PM, BC350, BC550, ABC350, and ABC550) were administered in triplicate to 100 g soil at 0%, 1%, and 3% (w/w). Relative to the poultry manure treatment, acidification drastically reduced the pH of BC350 and BC550 by 3.13 and 4.28 units, respectively, and increased the micronutrient availability of the studied soil. Furthermore, the biochars (both non-acidified and acidified) reduced the CO2 emission compared to that of the poultry manure treatment. After 1% treatment with BC550 and ABC550, the CO2 emissions from the soil were 89.6% and 91.4% lower, respectively, than in the 1% poultry manure treatment. In summary, acidified biochar improved the micronutrient availability in alkaline soil, and when produced at higher temperature, can mitigate the CO2 emissions of soil carbon sequestration. [ABSTRACT FROM AUTHOR]

Millions of human pathogenic viral particles are shed from infected individuals and introduce into wastewater, subsequently causing waterborne diseases worldwide. These viruses can be transmitted from wastewater to human beings via direct contact and/or ingestion/inhalation of aerosols. Even the advanced wastewater treatment technologies are unable to remove pathogenic viruses from wastewater completely, posing a serious health risk. Recently, coronavirus disease 2019 (COVID-19) has been urged globally due to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), which has resulted in >4.1 million deaths until July 2021. A rapid human-to-human transmission, uncertainties in effective vaccines, non-specific medical treatments, and unclear symptoms compelled the world into complete lockdown, social distancing, air-travel suspension, and closure of educational institutions, subsequently damaging the global economy and trade. Although, few medical treatments, rapid detection tools, and vaccines have been developed so far to curb the spread of COVID-19; however, several uncertainties exist in their applicability. Further, the acceptance of vaccines among communities is lower owing to the fear of side effects such as blood-clotting and heart inflammation. SARS-CoV-2, an etiologic agent of COVID-19, has frequently been detected in wastewater, depicting a potential transmission risk to healthy individuals. Contrarily, the occurrence of SARS-CoV-2 in wastewater can be used as an early outbreak detection tool via water-based epidemiology. Therefore, the spread of SARS-CoV-2 through fecal-oral pathway can be reduced and any possible outbreak can be evaded by proper wastewater surveillance. In this review, wastewater recycling complications, potential health risks of COVID-19 emergence, and current epidemiological measures to control COVID-19 spread have been discussed. Moreover, the viability of SARS-CoV-2 in various environments and survival in wastewater has been reviewed. Additionally, the necessary actions (vaccination, face mask, social distancing, and hand sanitization) to limit the transmission of SARS-CoV-2 have been recommended. Therefore, wastewater surveillance can serve as a feasible, efficient, and reliable epidemiological measure to lessen the spread of COVID-19., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The development of a simple method to synthesize highly efficient and stable magnetic microsphere beads for sulfathiazole (STZ) removal from contaminated aqueous media was demonstrated in this study. Conocarpus ( Conocarpus erectus L.) tree waste (CW) derived biochar (BC) was modified to fabricate chitosan-BC (CBC) and magnetic CBC (CBC-Fe) microsphere beads. Proximate, chemical, and structural properties of the produced adsorbents were investigated. Kinetics, equilibrium, and pH adsorption batch trials were conducted to evaluate the effectiveness of the synthesized adsorbents for STZ removal. All adsorbents exhibited the highest STZ adsorption at pH 5.0. STZ adsorption kinetics data was best emulated using pseudo-second order and Elovich models. The equilibrium adsorption data was best emulated using Langmuir, Freundlich, Redlich-Peterson, and Temkin models. CBC-Fe demonstrated the highest Elovich, pseudo-second order, and power function rate constants, as well as the highest apparent diffusion rate constant. Additionally, Langmuir isotherm predicted maximum adsorption capacity was the highest for CBC-Fe (98.67 mg g -1 ), followed by CBC (56.54 mg g -1 ) and BC (48.63 mg g -1 ). CBC-Fe and CBC removed 74.5%-108.8% and 16.2%-25.6% more STZ, respectively, than that of pristine BC. π-π electron-donor-acceptor interactions and Lewis acid-base reactions were the main mechanisms for STZ removal; however, intraparticle diffusion and H-bonding further contributed in the adsorption process. The higher efficiency of CBC-Fe for STZ adsorption could be due to its magnetic properties as well as stronger and conducting microsphere beads, which degraded the STZ molecules through generation of HO • radicals., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2021 The Author(s).)

This study was conducted to investigate the potential of Jujube (Ziziphus jujube L) wood waste-derived biochar (BC) and its derivative polymer-modified biochar (PBC) in removing hexavalent chromium (Cr VI) from aqueous solutions and in achieving Cr stabilization in tannery waste-contaminated soil. BC was produced at three different pyrolysis temperature (300 °C, 500 °C, 700 °C) and was polymerized with acrylamide and N, N1 methylenebisacrylamide. The results showed that Cr VI adsorption is a function of the pH and Cr VI initial concentration of the solution. The PBC showed highest sorption efficiency for Cr VI removal, which amounted to 76.4%-99.6% of the Cr VI overall initial concentrations (5-40 mg L -1 ) at an initial pH of 2. In greenhouse, wheat (Triticum aestivum L) was cultivated as a test crop in pots with tannery waste-contaminated soil along with BCs and PBCs amendments. The BC and PBC amended soil showed 47.7% and 65% less Cr uptake by the plant roots in comparison with unamended soil, respectively. In addition, zero concentration of Cr in the plant shoots was noted with the PBC-amended soil, while the Cr concentration in the shoots was decreased by 89% with the BC-amended soil. Thus, it was concluded that BC and PBC have great potential in removing Cr VI from aqueous phases and in decreasing the Cr mobility and bioavailability in soil., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Purpose: The Kingdom of Saudi Arabia is continuously in search of environment-friendly farming practices since mass-scale agriculture was initiated. It is imperative to gauge to the level of awareness of the farmers on the agricultural practices causing environmental issue in order to devise new agricultural extension programs. This research aims to identify the attitudes of farmers towards agriculture and environment in Al-Ghat area of Saudi Arabia., Methodology: A simple random sample of 110 farms truly representing the farming community was drawn to meet the objectives of the study. Data were collected by using the pre-tested questionnaire during the face-to-face interviews. In order to understand the message of study, data were analyzed for percentages, arithmetic average and standard deviation in addition to the simple Pearson correlation coefficient., Results: The results showed that the high proportion (87.3%) of farmers was interested in continuing to work farm and 77.3% of farmers did not consider adopting agriculture their main occupation. The findings of the survey reveal that some 55.5% of the respondent farmers were aware of the agricultural practices and their relation to the environment. Some 57.3% of the surveyed farmers are aware of potential benefits of enhanced utilization of agricultural organic wastes. However, main profession, farm employment (as the independent variables) showed a significant positive correlation with the attitudes of farmers towards their working in agriculture (as a dependent variable). Also a significant negative relationship between the educational levels and the attitudes of the farmers towards working in agriculture was noticed. The study also indicated a significant correlation between education and the degree of awareness of agricultural practices related to the environment and maximizing the optimum utilization of agricultural waste i.e. organic residues., Conclusions: The study suggested the need for new awareness and orientation programs to educate farmers and extension workers, highlighting the environment- friendly agricultural practices.Recommendation: There is need to offer incentives and facilities to keep the farmers stay in the farming business. Extension staff must keep educating them on beneficial features of organic farm waste and crop residues as organic fertilizers., (© 2020 Published by Elsevier B.V. on behalf of King Saud University.)

Waste date palm-derived biochar (DPBC) was modified with nano-zerovalent iron (BC-ZVI) and silica (BC-SiO 2 ) through mechanochemical treatments and evaluated for arsenate (As(V)) removal from water. The feedstock and synthesized adsorbents were characterized through proximate, ultimate, and chemical analyses for structural, surface, and mineralogical compositions. BC-ZVI demonstrated the highest surface area and contents of C, N, and H. A pH range of 2-6 was optimum for BC-ZVI (100% removal), 3-6 for DPBC (89% removal), and 4-6 for BC-SiO 2 (18% removal). Co-occurring PO 4 3- and SO 4 2- ions showed up to 100% reduction, while NO 3 - and Cl - ions resulted in up to 26% reduction in As(V) removal. Fitness of the Langmuir, Freundlich and Redlich-Peterson isotherms to As(V) adsorption data suggested that both mono- and multi-layer adsorption processes occurred. BC-ZVI showed superior performance by demonstrating the highest Langmuir maximum adsorption capacity (26.52 mg g -1 resulted in lower As(V) removal than that of DPBC. Pseudo-second-order kinetic model fitted well with the As(V) adsorption data (R 2  = 0.99), while the Elovich, intraparticle diffusion, and power function models showed a moderate fitness (R -1 , respectively). Blockage of pores with silica particles in BC-SiO 2 resulted in lower As(V) removal than that of DPBC. Pseudo-second-order kinetic model fitted well with the As(V) adsorption data (R 2  = 0.99), while the Elovich, intraparticle diffusion, and power function models showed a moderate fitness (R 2  = 0.53-0.93). The dynamics of As(V) adsorption onto the tested adsorbents exhibited the highest adsorption rates for BC-ZVI. As(V) adsorption onto the tested adsorbents was confirmed through post-adsorption FTIR, SEM-EDS, and XRD analyses. Adsorption of As(V) onto DPBC, BC-SiO 2 , and AC followed electrostatic interactions, surface complexation, and intraparticle diffusion, whereas, these mechanisms were further abetted by the higher surface area, nano-sized structure, and redox reactions of BC-ZVI., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The prevalence of organic micropollutants (OMPs) in various environmental compartments is posing a serious health risks to all kinds of lives on the planet. The levels of OMPs such as polyaromatic hydrocarbons, antibiotics, pesticides, contraceptive medicines, and personal care products in water bodies are increasing with each passing day. It is an urgent need of time to limit the release of OMPs into the environment, and to remove the prevailing OMPs for sustainable environmental management. The majority of the conventional means of water decontamination are either inefficient or expensive. However, due to nanosize, high surface area, and hollow and layered structure, carbon nanotubes (CNTs) serve as excellent sorbents for the removal of a diverse range of OMPs. The occurrence of emerging OMPs and their detrimental effects on human and animal health are collected and discussed in this review. The characteristics and efficacy of various CNTs (pristine and modified) for the efficient removal of different OMPs, and the removal mechanisms have been reviewed and discussed. The literature demonstrated that adsorption of OMPs onto CNTs is very complicated and rely on multiple factors including the properties of adsorbent and the adsorbate as well as solution chemistry. It was found that H-bonding, electrostatic interactions, van der Waals forces, hydrophobic interactions, H-π bongs, and π-π interactions were the major mechanisms responsible for the adsorption of OMPs onto various kinds of CNTs. Despite of higher affinities for OMPs, hydrophobicity and higher costs restrain the practical application of CNTs for wastewater treatment on large scale. However, continuous production may lead to the development of cost-effective, efficient and eco-friendly CTNs technology for wastewater treatments in future., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Biochar has vital importance as soil additives due to its characteristics, which are responsible for alleviating environmental problems and climate change. These additives should be evaluated to understand their physico-chemical properties and their ecotoxicological effects on plant growth. Therefore, this study aimed to (i) distinguish the properties of biochar produced from date palm and its derivative hydrochar, and (ii) investigate their ecotoxicological effects. Specifically, the biochar and hydrochar were produced from date palm leaflets by pyrolysis and hydrothermal carbonization, respectively. The produced chars were evaluated for their characteristics before and after water washing, and for their ecotoxicological effects on seed germination of lettuce ( Lactuca sativa L). The results show that water washing lowered biochar's pH and increased hydrochar's pH. Moreover, water washing of hydrochar caused a significant reduction in the total content of essential elements such as Ca, Mg, Mn, and Zn. Lettuce germination was significantly inhibited to 20% by hydrochar, whereas biochar enhanced lettuce growth by increasing shoot length (by 51%) and dry biomass (by 114%). Hydrochar toxicity was correlated (R > 0.95 at p  = 0.05) with high contents of total polyaromatic hydrocarbons (98.8 mg kg -1 ). Pre-treatment and assessment of hydrochar should be taken into account prior to application as a soil amendment.

Biochar (BC) was produced by pyrolyzing the date palm leaf waste at 600 °C and then loaded with phosphorus (P) via sorption process. Greenhouse pot experiment was conducted to investigate the application effects of BC and P-loaded biochar (BCP) on growth and availability of P and heavy metals to maize (Zea mays L.) plants grown in contaminated mining soil. The treatments consisted of BC and BCP (at application rates of 5, 10, 20, and 30 g kg -1 of soil), recommended NK and NPK, and a control (no amendment). Sorption experiment showed that Langmuir predicted maximum P sorption capacity of BC was 13.71 mg g -1 . Applying BCP increased the soil available P, while BC and BCP significantly decreased the soil labile heavy metals compared to control. Likewise, heavy metals in exchangeable and reducible fractions were transformed to more stable fraction with BC and BCP applications. The highest application rate of BCP (3%) was most effective treatment in enhancing plant growth parameters (shoot and root lengths and dry matter) and uptake of P and heavy metals by 2-3 folds. However, based on metal uptake and phytoextraction indices, total heavy metals extraction by maize plants was very small for practical application. It could be concluded that using P-loaded biochar as a soil additive may be considered a promising tool to immobilize heavy metals in contaminated mining areas, while positive effects on the biomass growth of plants may assist the stabilization of contaminated areas affected by wind and water erosion., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

A comparison between two digestion methods of hot plate Hossner (total-total) and USEPA method 3051 (total-recoverable) was carried out to suggest a proper method for determining nine heavy metals (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn) content of three urban soils affected by mining (Mahd AD'Dahab) or industrial activities (Riyadh and Jubail) at Saudi Arabia. The results showed no significant differences between two digestion methods for Cd, Cu, Pb and Zn in soils affected by mining and for Cr, Cu, Pb and Zn in soils affected by industrial activities. Additionally, lower biases were obtained between two methods for metals Cd, Cu, Zn and Pb in the urban soil samples from mining area with the percent biases of -16.5%, +6.24%, -12.4% and +24.1%, respectively. The results also revealed that only Cu and Zn in the soil samples from Riyadh were extracted satisfactorily using USEPA 3051 with low biases of +5.69% and -9.61%, respectively. Meanwhile, only Pb in soil samples from Jubail showed lower baise between two methods with satisfactory biase of -8.07%. The correlation coefficients were significant between total-recoverable and total-total concentrations for Cu (r = 0.66), Pb (r = 0.72) and Cd (r = 0.65) in soil samples from mining area. Overall, concentrations of Co, Cr, Fe, Mn, and Ni that may show soil background concentrations were found higher by Hossner method than by USEPA 3051; thus, this suggests the addition of hydrofluoric acid (HF) is necessary for the determination of lithogenic metal concentrations. It could be concluded that the USEPA 3051 may be recommended and applied for total Cd, Cu, Pb and Zn originated from anthropogenic source in mining and industrial areas., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

The present study was conducted in one of the most densely cultivated area of Al-Qassim region in Kingdom of Saudi Arabia to (i) monitor trace metal (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) contents in surface and subsurface soils, (ii) assess the pollution and potential ecological risk levels of trace metals, and (iii) identify trace metal sources using enrichment factor (EF), correlation matrix, and principal component analysis (PCA). The pollution levels of the analyzed trace metals calculated by the geoaccumulation index (I geo ) and contamination factor (C f ) suggested that the soils were highly contaminated with Cd and moderately contaminated with Pb. Based on the average values of EF, soil samples were found to present extremely high enrichment for Cd, significant enrichment for Pb, moderate enrichment for Zn, and deficient to minimal enrichment for other trace metals. Among the analyzed trace metals, a very high ecological risk was observed only in the case of Cd at some sampling sites. Meanwhile, other investigated trace metals had a low ecological risk. The results of PCA combined with correlation matrix suggested that Fe, Mn, Zn, Cu, Cr Ni, Cu, and Co represent natural abundance in soil, but Cd, Pb, and Cu are of anthropogenic inputs, mainly due to agrochemical and fertilizer applications. It could be generally concluded that the obtained results can be useful for assessing and conducting a future program for trace metal monitoring in agricultural areas of Saudi Arabia.

Many studies have reported the positive effect of biochar on soil carbon sequestration and soil fertility improvement in acidic soils. However, biochar may have different impacts on calcareous sandy soils. A 90-day incubation experiment was conducted to quantify the effects of woody waste biochar (10 g kg(-1)) on CO2-C emissions, K2SO4-extractable C and macro-(N, P and K) and micro-(Fe, Mn, Zn and Cu) nutrient availability in the presence or absence of poultry manure (5 g kg(-1) soil). The following six treatments were applied: (1) conocarpus (Conocarpus erectus L.) waste (CW), (2) conocarpus biochar (BC), (3) poultry manure (PM), (4) PM+CW, (5) PM+BC and (6) untreated soil (CK). Poultry manure increased CO2-C emissions and K2SO4-extractable C, and the highest increases in CO2-C emission rate and cumulative CO2-C and K2SO4-extractable C were observed for the PM+CW treatment. On the contrary, treatments with BC halted the CO2-C emission rate, indicating that the contribution of BC to CO2-C emissions is negligible compared with the soils amended with CW and PM. Furthermore, the combined addition of PM+BC increased available N, P and K compared with the PM or BC treatments. Overall, the incorporation of biochar into calcareous soils might have benefits in carbon sequestration and soil fertility improvement., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The objective of this study was to assess the use of Concarpus biochar as a soil amendment for reducing heavy metal accessibility and uptake by maize plants (Zea mays L.). The impacts of biochar rates (0.0, 1.0, 3.0, and 5.0% w/w) and two soil moisture levels (75% and 100% of field capacity, FC) on immobilization and availability of Fe, Mn, Zn, Cd, Cu and Pb to maize plants as well as its application effects on soil pH, EC, bulk density, and moisture content were evaluated using heavy metal-contaminated soil collected from mining area. The biochar addition significantly decreased the bulk density and increased moisture content of soil. Applying biochar significantly reduced NH4OAc- or AB-DTPA-extractable heavy metal concentrations of soils, indicating metal immobilization. Conocarpus biochar increased shoot dry biomass of maize plants by 54.5-102% at 75% FC and 133-266% at 100% FC. Moreover, applying biochar significantly reduced shoot heavy metal concentrations in maize plants (except for Fe at 75% FC) in response to increasing application rates, with a highest decrease of 51.3% and 60.5% for Mn, 28% and 21.2% for Zn, 60% and 29.5% for Cu, 53.2% and 47.2% for Cd at soil moisture levels of 75% FC and 100% FC, respectively. The results suggest that biochar may be effectively used as a soil amendment for heavy metal immobilization and in reducing its phytotoxicity.

The aim of this study was to investigate the concentrations and pollution status of heavy metals (Cu, Cd, Ni, Pb, Zn and Cr) in the mangrove surface sediments from the Farasan Island, Coast of Red Sea, Saudi Arabia. The ability of mangroves (Avicennia marina) to accumulate and translocate heavy metal within their different compartments was also investigated. Five sampling sites were chosen for collection of sediments and different compartments (leaf, branch and root) of A. marina. The results showed that the maximum and average concentrations of Cd, Cu and Pb in the studied area exceeded their world average concentration of shale. Additionally, only the maximum concentration of Zn exceeded its world average shale concentration. Based on the quality guidelines of sediment (SQGs), the collected sediment samples were in moderate to heavy rate for Cu, non-polluted to heavy rate for Pb and Zn, and non-polluted to moderate rate for Cr and Ni. The average metal concentrations of A. marina in the studied area were observed in the order Cu (256.0-356.6mgkg(-1))>Zn (29.5-36.8mgkg(-1))>Cr (8.15-14.9mgkg(-1))>Ni (1.37-4.02mgkg(-1))>Cd (not detectable-1.04mgkg(-1))>Pb (not detectable). Based on bio-concentration factors (BCF), their most obtained values were considered too high (>1), suggesting that A. marina can be considered as a high-efficient plant for bioaccumulation of heavy metals. Among all metals, Cu and Cr were highly bio-accumulated in different parts of A. marina. In terms of heavy metal contamination control via phyto-extraction, our findings suggest also that A. marina may be classified as potential accumulator for Cu in aboveground parts, as indicated by higher metal accumulation in the leaves combined with bio-concentration factor (BCF) and translocation factor (TF) values >1., (© 2013 Published by Elsevier Inc.)

In recent decades, heavy metal contamination in soil adjacent to chromated copper arsenate (CCA) treated wood has received increasing attention. This study was conducted to determine the pollution level (PL) based on the concentrations of Cr, Cu and As in soils and to evaluate the remediative capacity of native plant species grown in the CCA contaminated site, Gangwon Province, Korea. The pollution index (PI), integrated pollution index (IPI), bioaccumulation factors (BAF(shoots) and BAF(roots)) and translocation factor (TF) were determined to ensure soil contamination and phytoremediation availability. The 19 soil samples from 10 locations possibly contaminated with Cr, Cu and As were collected. The concentrations of Cr, Cu and As in the soil samples ranged from 50.56-94.13 mg kg(-1), 27.78-120.83 mg kg(-1), and 0.13-9.43 mg kg(-1), respectively. Generally, the metal concentrations decreased as the distance between the CCA-treated wood structure and sampling point increased. For investigating phytoremediative capacity, the 19 native plant species were also collected in the same area with soil samples. Our results showed that only one plant species of Iris ensata, which presented the highest accumulations of Cr (1120 mg kg(-1)) in its shoot, was identified as a hyperaccumulator. Moreover, the relatively higher values of BAF(shoot) (3.23-22.10) were observed for Typha orientalis, Iris ensata and Scirpus radicans Schk, suggesting that these plant species might be applicable for selective metal extraction from the soils. For phytostabilization, the 15 plant species with BAF(root) values>1 and TF values<1 were suitable; however, Typha orientalis was the best for Cr., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Rapeseed (Brassica napus L.) has been cultivated for biodiesel production worldwide. Winter rapeseed is commonly grown in the southern part of Korea under a rice-rapeseed double cropping system. In this study, a greenhouse pot experiment was conducted to assess the effects of rapeseed residue applied as a green manure alone or in combinations with mineral N fertilizer on Cd and Pb speciation in the contaminated paddy soil and their availability to rice plant (Oryza sativa L.). The changes in soil chemical and biological properties in response to the addition of rapeseed residue were also evaluated. Specifically, the following four treatments were evaluated: 100% mineral N fertilizer (N100) as a control, 70% mineral N fertilizer+rapeseed residue (N70+R), 30% mineral N fertilizer+rapeseed residue (N30+R) and rapeseed residue alone (R). The electrical conductivity and exchangeable cations of the rice paddy soil subjected to the R treatment or in combinations with mineral N fertilizer treatment, N70+R and N30+R, were higher than those in soils subjected to the N100 treatment. However, the soil pH value with the R treatment (pH 6.3) was lower than that with N100 treatment (pH 6.9). Use of rapeseed residue as a green manure led to an increase in soil organic matter (SOM) and enhanced the microbial populations in the soil. Sequential extraction also revealed that the addition of rapeseed residue decreased the easily accessible fraction of Cd by 5-14% and Pb by 30-39% through the transformation into less accessible fractions, thereby reducing metal availability to the rice plant. Overall, the incorporation of rapeseed residue into the metal contaminated rice paddy soils may sustain SOM, improve the soil chemical and biological properties, and decrease the heavy metal phytoavailability., (Copyright © 2011 Elsevier Ltd. All rights reserved.)