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1.
Purpose
Combined contamination of lead (Pb), cadmium (Cd), and arsenic (As) in soils especially wastewater-irrigated soil causes environmental concern. The aim of this study is to develop a soil amendment for simultaneous immobilization of Pb, Cd, and As in combinative contaminated soil.Materials and methods
A soil amendment of iron hydroxyl phosphate (FeHP) was prepared and characterized, and its potential application in simultaneous immobilization of Pb, Cd, and As in combined contaminated soil from wastewater-irrigated area was evaluated. The effects of FeHP dosage, reaction time, and soil moisture on Pb, Cd, and As immobilization in the soil were examined.Results and discussion
The immobilization efficiencies of Pb, Cd, and As generally increased with the increasing of FeHP dosage. With FeHP dosage of 10 %, the immobilization percentages of NaHCO3-extractable As and DTPA-extractable Pb and Cd reached 69, 59, and 44 %, respectively. The equilibrium time required for immobilization of these contaminants was in the following order: NaHCO3-extractable As (0.25 days) < DTPA-extractable Cd(3 days) < DTPA-extractable Pb (7 days). However, the immobilization efficiencies of Pb, Cd, and As have not changed much under soil moisture varied from 20 to 100 %. According to the results of the sequential extraction, the percentages of Pb, Cd, and As in residual fractions increased after the application of FeHP amendment, while their percentages in exchangeable fractions decreased, illustrating that FeHP can effectively decrease the mobilities and bioavailabilities of Pb, Cd, and As in the soil. Moreover, the application of FeHP will not have soil acidification and soil structure problem based on the soil pH measurements and soil morphology.Conclusions
FeHP can immobilize Pb, Cd, and As in the combinative contaminated soil from wastewater irrigation area simultaneously and effectively. Thus, it can be used as a potential soil amendment for the remediation of Pb, Cd, and As-combined contaminated soil.2.
Mahdi Safaei Khorram Yuan Zheng Dunli Lin Qian Zhang Hua Fang Yunlong Yu 《Journal of Soils and Sediments》2016,16(10):2439-2448
Purpose
Biochar application has been shown to be effective in improving soil fertility and sequestering soil contaminants. However, the impact of biochar amendments on the environmental fate of pesticides and the bioavailability of pesticides to living organisms in the soil environment is still not fully understood.Materials and methods
Dissipation of fomesafen and its bioavailability to corn (Zea mays L.) and the earthworm Eisenia fetida in an agricultural soil amended with three different rates of rice hull biochar (0.5, 1, and 2 % (w/w)) under laboratory conditions was investigated.Results and discussion
Biochar amendment significantly increased the DT50 of fomesafen from 34 days in unamended soil to 160 days in 2 % biochar-amended soil. Furthermore, biochar amendment decreased fomesafen concentration in soil pore water resulting in lower plant uptake of the pesticide. In this case, total plant residue and soil pore water concentrations of fomesafen in 2 % biochar-amended soil decreased to 0.29 % and 0.28–45 % of that in the control, respectively. Similar results were obtained for bioavailability of fomesafen in earthworms, as the earthworm residue and soil pore water concentration of fomesafen in 2 % biochar-amended soil declined to 0.38–45 and 0.47–0.50 % compared to the level of the control, respectively.Conclusions
As biochar could markedly reduce the concentration of fomesafen in soil pore water and subsequently reduce plant and earthworm uptake of fomesafen from contaminated soil, biochar amendment could be considered an appropriate option for immobilizing fomesafen in soils, protecting nontarget organisms from fomesafen contamination.3.
Jingtao Wu Hanqing Li Feng Li Yanju Zhang Huanping Lu Ping Zhuang Qifeng Mo Zhian Li 《Journal of Soils and Sediments》2016,16(9):2286-2295
Purpose
The objectives of this study were (1) to investigate the effects of manure compost and earthworms on Cd mobility in Cd-contaminated soil, (2) to test whether the bioturbation of earthworms reduces the immobilization effect of the manure compost when they are combined, and (3) to explore the distribution of Cd in aggregates formed by earthworms with corresponding fractionation analysis.Materials and methods
A laboratory experiment was conducted to evaluate the effect of either or both application of manure compost and the earthworms Eisenia fetida into cadmium historically contaminated soil on cadmium mobility. Soil characteristics and metal concentrations in earthworms and soil were measured, and soil aggregates in the mesocosms were separated for Cd fraction analysis based on four steps sequential extraction.Results and discussion
Manure compost reduced mobile Cd based on CaCl2 extraction and Toxicity Characteristic Leaching Procedure (TCLP) test by 60–95 and 25–30 %, respectively. However, earthworm application alone increased Cd mobility by 9–15 %. Besides, in the presence of manure compost, earthworms further immobilized cadmium to a slight extent. The interaction effect of manure compost and earthworms combined on Cd immobilization suggested that earthworms promoted the formation of large macroaggregates (>2 mm) and the redistribution of Cd concentration in soil aggregates. Additionally, earthworms reduced carbonate fraction of Cd from 42.3–49.6 to 6.3–19.5 % in different aggregates, respectively. And, residual fraction of Cd increased from 33.9–42.2 to 63.9–77.5 % simultaneously. The results may be due to the thorough mixture of phosphates and organic matter with cadmium during bioturbation on account of the available form of phosphorus, nitrogen, and cadmium changing to the more recalcitrant form.Conclusions
Manure compost addition increased the soil pH, phosphorus, nitrogen, and organic carbon content, and decreased Cd mobility. The application of earthworms and manure compost combined exhibited higher efficiency for cadmium immobilization, which can be used for Cd remediation due to the redistribution of Cd concentration in soil aggregates and the transformation of soluble Cd to the residual precipitate fraction.4.
Anle Dong Xinxin Ye Hongying Li Yunxia Zhang Guozhong Wang 《Journal of Soils and Sediments》2016,16(8):2030-2040
Purpose
The presence of high copper (Cu) and cadmium (Cd) contamination in soils around mining areas has raised serious health concerns. Improving hydroxyapatite (HAP) adsorption capacity for Cu and Cd is important if its application potential in heavily contaminated soils is to expand.Materials and methods
The micro/nanostructured HAP (mnHAP) was synthesized using a template-induced method to improve the HAP immobilization of Cu and Cd in contaminated soils. Commercial and synthetic HAPs were evaluated as amendments in Cu and Cd remediation tests with 1.5 and 3.0 % addition level for 90 days, and soils without HAP materials (0.0 %) were designated as the controls; each treatment was repeated three times. The materials were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), N2 adsorption, and scanning electron microscopy (SEM)-energy-dispersive spectra (EDS) and then quantitatively determined the Cu and Cd contents by inductively coupled plasma (ICP) and inductively coupled plasma mass spectrometry (ICP-MS).Results and discussion
The mnHAP was more effective in immobilizing Cu and Cd than the two commercial HAPs. After treatment with mnHAP at the 3.0 % addition level for 90 days, the contaminated soils showed 55.2 and 84.8 % reductions in Cu and Cd concentrations in the toxicity characteristic leaching procedure (TCLP) leaching procedure, respectively. The experimental data indicated that the enhanced Cu and Cd immobilization by mnHAP was due to the increases of surface area and the improvement of structure and newly introduced carboxylate groups on its surface.Conclusions
These findings show that regulating the structure and surface properties of HAP can enhance Cu and Cd immobilization in soils.5.
Nitrogen transformation rates and N<Subscript>2</Subscript>O producing pathways in two pasture soils
Ting Lan Helen Suter Rui Liu Xuesong Gao Deli Chen 《Journal of Soils and Sediments》2018,18(9):2970-2979
Purpose
Better understanding of N transformations and the regulation of N2O-related N transformation processes in pasture soil contributes significantly to N fertilizer management and development of targeted mitigation strategies.Materials and methods
15N tracer technique combined with acetylene (C2H2) method was used to measure gross N transformation rates and to distinguish pathways of N2O production in two Australian pasture soils. The soils were collected from Glenormiston (GN) and Terang (TR), Victoria, Australia, and incubated at a soil moisture content of 60% water-filled pore space (WFPS) and at temperature of 20 °C.Results and discussion
Two tested pasture soils were characterized by high mineralization and immobilization turnover. The average gross N nitrification rate (ntot) was 7.28 mg N kg?1 day?1 in TR soil () and 5.79 mg N kg?1 day?1 in GN soil. Heterotrophic nitrification rates (nh), which accounting for 50.8 and 41.9% of ntot, and 23.4 and 30.1% of N2O emissions in GN and TR soils, respectively, played a role similar with autotrophic nitrification in total nitrification and N2O emission. Denitrification rates in two pasture soils were as low as 0.003–0.004 mg N kg?1 day?1 under selected conditions but contributed more than 30% of N2O emissions.Conclusions
Results demonstrated that two tested pasture soils were characterized by fast N transformation rates of mineralization, immobilization, and nitrification. Heterotrophic nitrification could be an important NO3?–N production transformation process in studied pasture soils. Except for autotrophic nitrification, roles of heterotrophic nitrification and denitrification in N2O emission in two pasture soils should be considered when developing mitigation strategies.6.
Mahtab Ahmad Sang Soo Lee Sung Eun Lee Mohammad I. Al-Wabel Daniel C. W. Tsang Yong Sik Ok 《Journal of Soils and Sediments》2017,17(3):717-730
Purpose
Remediation of metal contaminated soil with biochar is attracting extensive interest in recent years. Understanding the significance of variable biochar properties and soil types helps elucidating the meticulous roles of biochar in immobilizing/mobilizing metals/metalloids in contaminated soils.Materials and methods
Six biochars were produced from widely available agricultural wastes (i.e., soybean stover, peanut shells and pine needles) at two pyrolysis temperatures of 300 and 700 °C, respectively. The Pb-, Cu-, and Sb-contaminated shooting range soils and Pb-, Zn-, and As-contaminated agricultural soils were amended with the produced biochars. The mobility of metals/metalloids was assessed by the standard batch leaching test, principal component analysis and speciation modeling.Results and discussion
The changes in soil properties were correlated to feedstock types and pyrolysis temperatures of biochars based on the principal component analysis. Biochars produced at 300 °C were more efficient in decreasing Pb and Cu mobility (>93 %) in alkaline shooting range soil via surface complexation with carboxyl groups and Fe-/Al-minerals of biochars as well as metal-phosphates precipitation. By contrast, biochars produced at 700 °C outperformed their counterparts in decreasing Pb and Zn mobility (100 %) in acidic agricultural soil by metal-hydroxides precipitation due to biochar-induced pH increase. However, Sb and As mobility in both soils was unfavorably increased by biochar amendment, possibly due to the enhanced electrostatic repulsion and competition with phosphate.Conclusions
It is noteworthy that the application of biochars is not equally effective in immobilizing metals or mobilizing metalloids in different soils. We should apply biochar to multi-metal contaminated soil with great caution and tailor biochar production for achieving desired outcome and avoiding adverse impact on soil ecosystem.7.
Bashar Qasim Mikael Motelica-Heino Sylvain Bourgerie Arnaud Gauthier Domenico Morabito 《Journal of Soils and Sediments》2016,16(3):811-820
Purpose
This study aimed at investigating the rhizosphere effects of Populus euramericana Dorskamp on the mobility of Zn, Pb and Cd in contaminated technosols from a former smelting site.Materials and methods
A rhizobox experiment was conducted with poplars, where the plant stem cuttings were grown in contaminated technosols for 2 months under glasshouse conditions. After plant growth, rhizosphere and bulk soil pore water (SPW) were sampled together. SPW properties such as pH, dissolved organic carbon (DOC) and total dissolved concentrations of Zn, Pb and Cd were determined. The concentrations of Zn, Pb and Cd in plant organs were also determined.Results and discussion
Rhizosphere SPW pH increased for all studied soils by 0.3 to 0.6 units compared to bulk soils. A significant increase was also observed for DOC concentrations regardless of the soil type or total metal concentrations, which might be attributed to the plant root activity. For all studied soils, the rhizosphere SPW metal concentrations decreased significantly after plant growth compared to bulk soils which might be attributed to the increase in pH and effects of root exudates. Zn, Pb and Cd accumulated in plant organs and the higher metal concentrations were found in plant roots compared to plant shoots.Conclusions
The restricted transfer of the studied metals to the plant shoots confirms the potential role of this species in the immobilization of these metals. Thus, P. euramericana Dorskamp can be used for phytostabilization of technosols.8.
Tharanga Bandara Indika Herath Prasanna Kumarathilaka Mihiri Seneviratne Gamini Seneviratne Nishanta Rajakaruna Meththika Vithanage Yong Sik Ok 《Journal of Soils and Sediments》2017,17(3):665-673
Purpose
In this study, we investigated the effect of biochar (BC) and fungal bacterial co-inoculation (FB) on soil enzymatic activity and immobilization of heavy metals in serpentine soil in Sri Lanka.Materials and methods
A pot experiment was conducted with tomatoes (Lycopersicon esculentum L.) at 1, 2.5, and 5 % (w/w) BC ratios. Polyphenol oxidase, catalase and dehydrogenase activities were determined by idometric, potassium permanganate oxidisable, and spectrophotometric methods, respectively. Heavy metal concentrations were assessed by 0.01 M CaCl2 and sequential extraction methods.Results and discussion
An increase in BC application reduced polyphenol oxidase, dehydrogenase, and catalase activity. The application of FB increased soil dehydrogenase activity, with the maximum activity found in 1 % BC700?+?FB treatment. Moreover, the CaCl2 extractable metals (Ni, Mn, and Cr) in 5 % BC700 amended soil decreased by 92, 94, and 100 %, respectively, compared to the control. Sequential extraction showed that the exchangeable concentrations of Ni, Mn, and Cr decreased by 55, 70, and 80 % in 5 % BC700, respectively.Conclusions
Results suggest that the addition of BC to serpentine soil immobilizes heavy metals and decreases soil enzymatic activities. The addition of FB to serpentine soil improves plant growth by mitigating heavy metal toxicity and enhancing soil enzymatic activities.9.
Hongbiao Cui Yuchao Fan Lei Xu Jing Zhou Dongmei Zhou Jingdong Mao Guodong Fang Long Cang Zhenqiu Zhu 《Journal of Soils and Sediments》2016,16(5):1498-1508
Purpose
In situ immobilization of heavy metal-contaminated soils with the repeated incorporation of amendments can effectively reduce the bioavailability of soil heavy metals. However, the long-term application of amendments would lead to the destruction of soil structure and accumulation of soil toxic elements, ultimately affecting food security and quality. Thus, the sustainability of the amendments in a heavy metal-contaminated soil was evaluated from 2010 to 2012.Materials and methods
Batch field experiments were conducted in the soils, which were amended with apatite (22.3 t ha?1), lime (4.45 t ha?1), and charcoal (66.8 t ha?1), respectively. The amendments were applied only one time in 2009, and ryegrass was sown each year. Ryegrass and setaria glauca (a kind of weed) were harvested each year. Concentrations of copper (Cu) and cadmium (Cd) were determined by batch experiments. Five fractions of Cu and Cd were evaluated by a sequential extraction procedure.Results and discussion
Ryegrass grew well in the amended soils in the first year, but it failed to grow in all the soils in the third year. However, setaria glauca could grow with higher biomass in all the amended soils. The treatment of apatite combined with plants was more effective than lime and charcoal treatments in removing Cu and Cd from the contaminated soils by taking biomass into account. Apatite had the best sustainable effect on alleviating soil acidification. The Cu and Cd concentrations of CaCl2-extractable and exchangeable fractions decreased with the application of amendments. Moreover, apatite and lime could effectively maintain the bioavailability of Cu and Cd low.Conclusions
Apatite had a better sustainable effect on the remediation of heavy metal-contaminated soils than lime and charcoal. Although all the amendment treated soils did not reduce soil total concentrations of Cu and Cd, they could effectively reduce the environmental risk of the contaminated soils. The findings could be effectively used for in situ remediation of heavy metal-contaminated soils.10.
Borui Liu Qing Huang Yuefeng Su Mengyuan Wang Yufei Ma Ryan M. Kelly 《Journal of Soils and Sediments》2018,18(3):669-679
Purpose
Cobalt (Co) is a toxic metal to the environment and human’s health. The purpose of the study is to achieve an investigation into the efficacy of calcium carbonate and cow dung for Co immobilization in fluvo-aquic soil, as well as their effects on the antioxidant system in plants.Materials and methods
Calcium carbonate and cow dung were incorporated with the Co-polluted fluvo-aquic soil where pakchois (Brassica chinensis L.) were grown. Co concentration, superoxide dismutase (SOD) activity, catalase (CAT) activity, and malondialdehyde (MDA) concentration in the shoots of the mature plants were inspected.Results and discussion
As calcium carbonate concentration rose (0 to 12 g kg?1), Co concentration in shoots of the plants decreased firstly and then increased again (P < 0.05), while the accumulation level of Co kept decreasing with cow dung concentration rising (P < 0.05). Under the amendment treatments, the SOD activity, CAT activity, and MDA concentration in the shoots were all positively correlated to the Co concentration in the plant tissue (r = 0.792, 0.904, and 0.807, P < 0.01), indicating the antioxidant system receptivity to the Co accumulation. The amendments in soil can alleviate the oxidative stress in pakchois owing to Co pollution. As calcium carbonate concentration ranged from 5.64 to 7.86 g kg?1, the parameters reached a maxima (minimum), respectfully.Conclusions
Calcium carbonate and cow dung in fluvo-aquic soil are effective for Co immobilization and mitigating any pertinent oxidative stress in pakchoi plants. Calcium carbonate concentration within a range of 5.64 to 7.86 g·kg?1 will achieve optimum efficacy.11.
Bioavailability of Cd and Zn in soils treated with biochars derived from tobacco stalk and dead pigs
Xing Yang Kouping Lu Kim McGrouther Lei Che Guotao Hu Qiuyue Wang Xingyuan Liu Leilei Shen Huagang Huang Zhengqian Ye Hailong Wang 《Journal of Soils and Sediments》2017,17(3):751-762
Purpose
Previous studies show that application of biochar can reduce the bioavailability of heavy metals in soil. A plant growth experiment was carried out to evaluate the effect of tobacco stalk- and dead pig-derived biochars on the extractability and redistribution of cadmium (Cd) and zinc (Zn) in contaminated soil, and the impact on tobacco (Nicotiana tabacum L.) plant growth.Materials and methods
The top 20 cm of a soil contaminated with Cd and Zn was used in this study. Biochars derived from tobacco stalk and dead pig were applied to the soil at four application rates (0, 1, 2.5, and 5 %), and tobacco plants were grown. After 80-days growth, the pH, electrical conductivity (EC), CaCl2-extractable heavy metals and fractions of heavy metals in soil samples, as well as the plant biomass and the concentrations of heavy metals in the plant were determined.Results and discussion
The plant growth experiment demonstrated that tobacco stalk biochar and dead pig biochar significantly (P?<?0.05) increased the pH, but had no significant effect on the electrical conductivity (EC) of the soil. The CaCl2-extractable Cd and Zn content decreased as the application rates increased. The concentration of extractable Cd and Zn decreased by 64.2 and 94.9 %, respectively, for the tobacco stalk biochar treatment, and 45.8 and 61.8 %, respectively, for the dead pig biochar treatment at 5 % application rate. After biochar addition, the exchangeable Cd was mainly transformed to fractions bound to carbonates and Fe-Mn oxides, while the Zn was immobilized mainly in the fraction bound to Fe-Mn oxides. Tobacco stalk biochar increased the tobacco plant biomass by 30.3 and 36.2 % for shoot and root, respectively at the 5 % application rate. Dead pig biochar increased the tobacco plant biomass by 43.5 and 40.9 % for shoot and root, respectively, at the 2.5 % application rate. Both biochars significantly (P?<?0.05) decreased the Cd and Zn accumulation by tobacco plant.Conclusions
As a soil amendment, tobacco stalk biochar was more effective at removing Cd, whereas dead pig biochar was more effective at removing Zn, and a higher application rate was more effective than a lower application rate. Overall, biochar derived from tobacco stalk was more effective, than dead pig biochar, at remediating soil contaminated with Cd and Zn, as well as promoting tobacco growth.12.
Xinyu Mao Fengxiang X. Han Xiaohou Shao Zikri Arslan Jacqueline McComb Tingting Chang Kai Guo Ahmet Celik 《Journal of Soils and Sediments》2016,16(10):2344-2353
Purpose
Extensive deposition of Pb, As, and Cs in soils may damage ecosystems and human’s health. Soil washing is the most conventional remediation method, and its efficiency depends on metal solubility in soil. This study aims to optimize operating variables of electro-kinetic field (EKF)-enhanced soil washing procedures.Materials and methods
Soil samples from a Mississippi River Delta rice field were homogeneously spiked with Pb, As, and Cs, and contaminated soil was aged for 3 months. The remediation involved a first stage electro-kinetic process, followed by a soil washing procedure. Soil pH changes under EKF were studied. Effects of citric acid and reversed EKF were investigated for alleviating possible alkaline precipitation. In the washing procedure, soil washing time and cycles with different extractants were examined. The overall EKF-enhanced soil washing efficiencies were discussed as well.Results and discussion
The implement of EKF offered an acidic soil environment around the anode areas for solubilizing metal(loid)s. Combined with EKF, citric acid was more conductive to desorb metal(loid)s. In addition, the reversed EKF effectively alleviated metal(loid) precipitation caused by alkalization in the first stage cathode areas. The EKF significantly enhanced metal(loid) extractions in the anode area of soils using Na2EDTA, CaCl2, and citric acid at pH of 2. The most preferable removal of Pb (80–98 %), As (48–63 %), and Cs (10–13 %) was achieved with three extractants. CaCl2 and citric acid were proved to be suitable alternatives to Na2EDTA for Pb extraction. A washing process of 2 h extraction with double washing cycles was optimized.Conclusions
Soil washing time and cycles were major factors governing the metal(loid) removal from soil. Washing process of 2 h extraction with double cycles was optimized for further extraction based on higher washing efficiency. The EKF effectively improved washing efficiency while some electrical parameters need further studies for cost performance consideration.13.
Manhattan Lebrun Florie Miard Romain Nandillon Gabriella S. Scippa Sylvain Bourgerie Domenico Morabito 《Journal of Soils and Sediments》2018,18(6):2188-2202
Purpose
Anthropic activities induce severe metal(loid)s contamination of many sites, which is a threat to the environment and to public health. Indeed metal(loid)s cannot be degraded, and thus accumulate in soils. Furthermore, they can contaminate surrounding ecosystems through run-off or wind erosion. This study aims to evaluate the phytostabilization capacity of Salix viminalis to remediate As and Pb highly contaminated mine site, in a biochar-assisted phytoremediation context and to assess biochar particle size and dose application effects.Materials and methods
To achieve this, mesocosm experiments were conducted using the contaminated technosol and four different size fraction of one biochar as amendment, at two application rates (2 and 5%). Non-rooted cuttings of Salix viminalis were planted in the different mixtures. In order to characterize the mixtures, soil pore waters were sampled at the beginning and at the end of the experiment and analyzed for pH, electrical conductivity, and metal(loid) concentrations. After 46 days of Salix growth, roots, stems, and leaves were harvested and weighed, and As and Pb concentrations and distributions were measured.Results and discussion
Soil fertility improved (acidity decrease, electrical conductivity increase) following biochar addition, whatever the particle size, and the Pb concentration in soil pore water decreased. Salix viminalis did not grow on the non-amended contaminated soil while the biochar amendment permitted its growth, with a better growth with the finest biochars. The metal(loid)s accumulated preferentially in roots.Conclusions
Fine biochar particles allowed S. viminalis growth on the contaminated soil, allowing this species to be used for technosol phytostabilization.14.
Wei Liu Shutao Wang Peng Lin Hanwen Sun Juan Hou Qingqing Zuo Rong Huo 《Journal of Soils and Sediments》2016,16(2):476-485
Purpose
Biochar can be used to reduce the bioavailability and leachability of heavy metals, as well as organic pollutants in soils through adsorption and other physicochemical reactions. The objective of the study was to determine the response of microbial communities to biochar amendment and its influence on heavy metal mobility and PCBs (PCB52, 44, 101, 149, 118, 153, 138, 180, 170, and 194) concentration in application of biochar as soil amendment.Materials and methods
A pot (macrocosm) incubation experiment was carried out with different biochar amendment (0, 3, and 6 % w/w) for 112 days. The CaCl2-extractable concentration of metals, microbial activities, and bacterial community were evaluated during the incubation period.Results and discussion
The concentrations of 0.01 M CaCl2-extractable metals decreased (p?>?0.05) by 12.7 and 20.5 % for Cu, 5.0 and 15.6 % for Zn, 0.2 and 0.5 % for Pb, and 1.1 and 8.9 % for Cd, in the presence of 3 and 6 % of biochar, respectively, following 1 day of incubation. Meanwhile, the total PCB concentrations decreased from 1.23 mg kg?1 at 1 day to 0.24 mg kg?1 at 112 days after 6 % biochar addition, representing a more than 60 % decrease relative to untreated soil. It was also found out that biochar addition increased the biological activities of catalase, phosphatase, and urease activity as compared with the controls at the same time point. Importantly, the Shannon diversity index of bacteria in control soils was 3.41, whereas it was 3.69 and 3.88 in soils treated with 3 and 6 % biochar soil. In particular, an increase in the number of populations with the putative ability to absorb PCB was noted in the biochar-amended soils.Conclusions
The application of biochar to contaminated soils decreased the concentrations of heavy metals and PCBs. Application of biochar stimulated Proteobacteria and Bacteroides, which may function to absorb soil PCB and alleviate their toxicity.15.
Yasser Mahmoud Awad Sang Soo Lee Yong Sik Ok Yakov Kuzyakov 《Journal of Soils and Sediments》2017,17(3):611-620
Purpose
Various soil conditioners, such as biochar (BC) and anionic polyacrylamide (PAM), improve soil fertility and susceptibility to erosion, and may alter microbial accessibility and decomposition of soil organic matter (SOM) and plant residues. To date, no attempts have been made to study the effects of BC in combination with PAM on the decomposition of soil SOM and plant residues. The objective of this study was to evaluate the effects of BC, PAM, and their combination on the decomposition of SOM and alfalfa residues.Materials and methods
An 80-day incubation experiment was carried out to investigate the effects of oak wood biochar (BC; 10 Mg ha?1), PAM (80 kg ha?1), and their combination (BC?+?PAM) on decomposition of SOM and 14C-labeled alfalfa (Medicago sativa L.) residues by measuring CO2 efflux, microbial biomass, and specific respiration activity.Results and discussion
No conditioner exerted a significant effect on SOM decomposition over the 80 days of incubation. PAM increased cumulative CO2 efflux at 55–80 days of incubation on average of 6.7 % compared to the soil with plant residue. This was confirmed by the increased MBN and MB14C at 80 days of incubation in PAM-treated soil with plant residue compared to the control. In contrast, BC and BC?+?PAM decreased plant residue decomposition compared to that in PAM-treated soil and the respective control soil during the 80 days. BC and BC?+?PAM decreased MBC in soil at 2 days of incubation indicated that BC suppressed soil microorganisms and, therefore, decreased the decomposition of plant residue.Conclusions
The addition of oak wood BC alone or in combination with PAM to soil decreased the decomposition of plant residue.16.
Tingru Chen Xiaoyan Liu Xinying Zhang Yunyun Hou Xiao Chen Kaiyun Tao 《Journal of Soils and Sediments》2016,16(8):2090-2096
Purpose
This study aimed to evaluate the effect of combination of alkyl polyglucoside (APG) and nitrilotriacetic acid (NTA) on improving the efficiency of phytoremediation for pyrene and lead (Pb) co-contaminated soil by Scirpus triqueter.Materials and methods
Seedlings of S. triqueter with a similar size and biomass (3 g/pot) were grown on 2-month aged soil contaminated with 184.5 mg kg?1of pyrene and 454.3 mg kg?1 of Pb at pH?=?8.3. After growth for 10 days, different doses of APG and NTA were added into the soil. After 60 days, the height of plants, Pb concentrations in plants, and pyrene amounts in soil were determined.Results and discussion
Combined application of NTA and APG with lower dosage (1 + 1 g kg?1 soil and 1 + 2 g kg?1 soil) had no notable negative influence on the growth of S. triqueter. Moreover, significant synergy on Pb accumulation in S. triqueter was achieved with APG and NTA combined application. Besides, the dissipation of pyrene from soil after 60-day planting was increased in APG and NTA treatments when compared with the control treatments. Application of APG alone or combined with NTA had greater effect on enhancing dissipation of pyrene from soil than NTA alone.Conclusions
This study demonstrated that the remediation of Pb and pyrene co-contaminated soil by S. triqueter can be enhanced by combined application of APG and NTA. Long-term evaluation of this strategy is needed in co-contaminated field sites.17.
Purpose
Alpine ecosystems on the Qinghai-Tibetan Plateau are sensitive to global climatic changes. However, the effects of temperature change resulting from global warming or seasonal variation on soil N availability in those ecosystems are largely unknown.Materials and methods
We therefore conducted a 15N tracing study to investigate the effects of various temperatures (5–35 °C) on soil gross N transformation rates in an alpine meadow (AM) soil on the Qinghai-Tibetan Plateau. A natural secondary coniferous forest (CF) soil from the subtropical region was chosen as a reference to compare the temperature sensitivity of soil gross N transformation rates between alpine meadow and coniferous forest.Results and discussion
Our results showed that increasing temperature increased gross N mineralization and NH4 + immobilization rates and overall enhanced N availability for plants in both soils. However, both rates in the CF soil were less sensitive to a temperature change from 5 to 15 °C compared to the AM soil. In both soils, different N retention mechanisms could have been operating with respect to changing temperatures in the different climatic regions. In the CF soil, the absence of NO3 ? production at all incubation temperatures suggests that in the subtropical soil which is characterized by high rainfall, an increase in N availability due to increasing temperature could be completely retained in soils. In contrast, the AM soil may be vulnerable to N losses with respect to temperature changes, in particular at 35 °C, in which higher nitrification rates were coupled with lower NH4 + and NO3 ? immobilization rates.Conclusions
Our results suggest that increased soil temperature arising from global warming and seasonal variations will most likely enhance soil N availability for plants and probably increase the risk of N losses in the alpine meadow on the Qinghai-Tibetan Plateau.18.
Purpose
The study aimed at comparing the effects of different water managements on soil Cd immobilization using palygorskite, which was significant for the selection of reasonable water condition.Materials and methods
Field experiment was taken to discuss the in situ remediation effects of palygorskite on Cd-polluted paddy soils, under different water managements, using a series of variables, including pH and extractable Cd in soils, plant Cd, enzyme activity, and microorganism number in soils.Results and discussion
In control group, the pH in continuous flooding was the highest under three water conditions, and compared to conventional irrigation, continuous flooding reduced brown rice Cd by 37.9%, and brown rice Cd in wetting irrigation increased by 31.0%. In palygorskite treated soils, at concentrations of 5, 10, and 15 g kg?1, brown rice Cd reduced by 16.7, 44.4, and 55.6%; 13.8, 34.5, and 44.8%; and 13.1, 36.8, and 47.3% under continuous flooding, conventional irrigation, and wetting irrigation (p < 0.05), respectively. The enzyme activity and microbial number increased after applying palygorskite to paddy soils.Conclusions
Continuous flooding was a good candidate as water management for soil Cd stabilization using palygorskite. Rise in soil enzyme activity and microbial number proved that ecological function regained after palygorskite application.19.
Stefania Romeo Alessandra Francini Luca Sebastiani Domenico Morabito 《Journal of Soils and Sediments》2017,17(5):1394-1402
Purpose
Evaluate the efficiency of Populus alba clone Villafranca in the uptake and translocation of Zn from contaminated soils.Materials and methods
The effects of 48 days of zinc treatment (Zn t ) on the growth and the photosynthetic activities of P. alba L. clone Villafranca were studied using ZnSO4 (375 ppm per unit of soil dry weight) added in sand and peat moss substrate at the beginning of the treatment (T 0) and again after 30 days (T 1) in order to reach a target Zn concentration of 375 ppm at T 0 and 750 ppm at T 1 per unit of soil dry weight.Results and discussion
Zn uptake in the different organs was analyzed after 30 (T 1) and 48 days (T 2) from the beginning of treatment, showing the following order: root ? leaves ≥ woody cutting = stem. The leaf area increased by 12 % in comparison to control plants at the end of second treatment (48 days). Cutting radial growth showed a high synchronicity in the growth rate fluctuation among control and Zn t plants, but a higher increase in radial diameter of Zn t cutting was observed starting from day 38 (after 8 days of second Zn t ) reaching after 48 days 38 % higher than control plants.Conclusions
Although our data of leaf Zn concentration were in the range usually reported as toxic for plants, Villafranca clone in Zn t substrate were unaffected in terms of net CO2 assimilation and stomatal conductance to water vapor.20.
Xi-En Long Ju-Pei Shen Jun-Tao Wang Li-Mei Zhang Hongjie Di Ji-Zheng He 《Journal of Soils and Sediments》2017,17(2):384-392