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Colocalization of low-methylesterified pectins and Pb deposits in the apoplast of aspen roots exposed to lead
2015
Rabęda, Irena | Bilski, Henryk | Mellerowicz, Ewa J. | Napieralska, Anna | Suski, Szymon | Woźny, Adam | Krzesłowska, Magdalena
Low-methylesterified homogalacturonans have been suggested to play a role in the binding and immobilization of Pb in CW. Using root apices of hybrid aspen, a plant with a high phytoremediation potential, as a model, we demonstrated that the in situ distribution pattern of low-methylesterified homogalacturonan, pectin epitope (JIM5-P), reflects the pattern of Pb occurrence. The region which indicated high JIM5-P level corresponded with “Pb accumulation zone”. Moreover, JIM5-P was especially abundant in cell junctions, CWs lining the intercellular spaces and the corners of intercellular spaces indicating the highest accumulation of Pb. Furthermore, JIM5-P and Pb commonly co-localized.The observations indicate that low-methylesterified homogalacturonan is the CW polymer that determines the capacity of CW for Pb sequestration. Our results suggest a promising directions for CW modification for enhancing the efficiency of plant roots in Pb accumulation, an important aspect in the phytoremediation of soils contaminated with trace metals.
Show more [+] Less [-]Effects of PAHs and dioxins on the earthworm Eisenia andrei: A multivariate approach for biomarker interpretation
2015
Sforzini, Susanna | Moore, Michael N. | Boeri, Marta | Bencivenga, Mauro | Viarengo, Aldo
In this study, a battery of biomarkers was utilised to evaluate the stress syndrome induced in the earthworm Eisenia andrei by exposure to environmentally realistic concentrations of benzo[a]pyrene (B[a]P) and 2,3,7,8-tetrachlorodibenzo-para-dioxin (TCDD) in OECD soil. The set of tests was then employed to assess the toxicity of field soils contaminated with organic xenobiotic compounds (such as PAHs, dioxins and PCBs). The results highlighted an impairment of immune and metabolic functions and genotoxic damage in worms exposed also to lower bioavailable concentrations of toxic chemicals. Multivariate analysis of biomarker data showed that all different contaminated soils had a detrimental effect on the earthworms. A separation between temporal and concentration factors was also evident for B[a]P and TCDD treatments; and field contaminated soils were further differentiated reflecting a diverse contamination. Multivariate analysis also demonstrated that lysosomal membrane stability can be considered a prognostic indicator for worm health status.
Show more [+] Less [-]Evaluating potential non-point source loading of PAHs from contaminated soils: A fugacity-based modeling approach
2015
Luo, Xiaolin | Zheng, Yi | Lin, Zhongrong | Wu, Bin | Han, Feng | Tian, Yong | Zhang, Wei | Wang, Xuejun
Soils contaminated by Polycyclic Aromatic Hydrocarbons (PAHs) are subject to significant non-point source (NPS) pollution during rainfall events. Recent studies revealed that the classic enrichment ratio (ER) approach may not be applicable to PAHs. This study developed a model to estimate the ER of PAHs which innovatively applies the fugacity concept. The ER model has been validated with experimental data, which suggested that the transport of PAHs not only depends on their physicochemical properties, but on the sediment composition and how the composition evolves during the event. The modeling uncertainty was systematically examined, and found to be highly compound-dependent. Based on the ER model, a strategy was proposed to practically evaluate the potential NPS loading of PAHs in watersheds with heterogeneous soils. The study results have important implications to modeling and managing the NPS pollution of PAHs (or other chemicals alike) at a watershed scale.
Show more [+] Less [-]Tenax as sorption sink for in vitro bioaccessibility measurement of polycyclic aromatic hydrocarbons in soils
2015
Li, Chao | Cui, Xin−Yi | Fan, Ying−Ying | Teng, Ying | Nan, Zhong−Ren | Ma, Lena Q.
Physiologically based in vitro methods have been developed to measure bioaccessibility of organic contaminants in soils. However, bioaccessibility of hydrophobic organic contaminants (HOCs) can be underestimated by in vitro tests if gastrointestinal (GI) solution fails to provide sufficient sorption sink for HOCs. To circumvent this drawback, Tenax was included in GI solution as sorption sink to trap mobilized HOCs and maintain the desorption gradient between soil and GI solution. Polycyclic aromatic hydrocarbons (PAHs) were selected as target HOCs, and physiologically based extraction test (PBET) was selected as the in vitro method. Inclusion of Tenax in GI solution increased bioaccessibility of PAHs in five spiked soils from 8.25–20.8% to 55.7–65.9% and the bioaccessibility of PAHs in a field contaminated soil from 3.70–6.92% to 16.3–31.0%. Our results demonstrated the effectiveness of Tenax as sorption sink to enhance PAH mobilization in bioaccessibility measurement in soils.
Show more [+] Less [-]Transcriptional responses of earthworm (Eisenia fetida) exposed to naphthenic acids in soil
2015
Wang, Jie | Cao, Xiaofeng | Sun, Jinhua | Chai, Liwei | Huang, Yi | Tang, Xiaoyan
In this study, earthworms (Eisenia fetida) were exposed to commercial NAs contaminated soil, and changes in the levels of reactive oxygen species (ROS) and gene expressions of their defense system were monitored. The effects on the gene expression involved in reproduction and carcinogenesis were also evaluated. Significant increases in ROS levels was observed in NAs exposure groups, and the superoxide dismutase (SOD) and catalase (CAT) genes were both up-regulated at low and medium exposure doses, which implied NAs might exert toxicity by oxidative stress. The transcription of CRT and HSP70 coincided with oxidative stress, which implied both chaperones perform important functions in the protection against oxidative toxicity. The upregulation of TCTP gene indicated a potential adverse effect of NAs to terrestrial organisms through induction of carcinogenesis, and the downregulation of ANN gene indicated that NAs might potentially result in deleterious reproduction effects.
Show more [+] Less [-]Genotypic variations in the dynamics of metal concentrations in poplar leaves: A field study with a perspective on phytoremediation
2015
Pottier, Mathieu | García de la Torre, Vanesa S. | Victor, Cindy | David, Laure C. | Chalot, Michel | Thomine, Sébastien
Poplar is commonly used for phytoremediation of metal polluted soils. However, the high concentrations of trace elements present in leaves may return to soil upon leaf abscission.To investigate the mechanisms controlling leaf metal content, metal concentrations and expression levels of genes involved in metal transport were monitored at different developmental stages on leaves from different poplar genotypes growing on a contaminated field.Large differences in leaf metal concentrations were observed among genotypes. Whereas Mg was remobilized during senescence, Zn and Cd accumulation continued until leaf abscission in all genotypes. A positive correlation between Natural Resistance Associated Macrophage Protein 1 (NRAMP1) expression levels and Zn bio-concentration factors was observed. Principal component analyses of metal concentrations and gene expression levels clearly discriminated poplar genotypes.This study highlights a general absence of trace element remobilization from poplar leaves despite genotype specificities in the control of leaf metal homeostasis.
Show more [+] Less [-]Influence of feeding and earthworm density on compound bioaccumulation in earthworms Eisenia andrei
2015
Šmídová, Klára | Šerá, Jana | Bielská, Lucie | Hofman, Jakub
Earthworm density and feeding during exposure to contaminated soil have been used inconsistently in bioaccumulation studies, which may lead to possible errors in risk assessment and modeling. Hydrophobic organic pollutants with a wide range of environmental properties (phenanthrene, pyrene, lindane, p,p′-DDT, and PCB 153) were used to study the effect of different earthworm densities in combination with the presence or absence of feeding on bioaccumulation factors (BAFs). Similar BAFs were found at various soil-to-worm ratios, with the exception of phenanthrene. We recommend using at least 15 gsoil dw per earthworm. The absence of feeding doubled the BAFs and, thus, using no food ration can be considered as “the worst case scenario”. Whenever food is to be applied (i.e. to ensure the validity of the test in earthworm mass loss), we suggest feeding depending on the organic carbon content of the studied soil.
Show more [+] Less [-]Slash-and-char: An ancient agricultural technique holds new promise for management of soils contaminated by Cd, Pb and Zn
2015
Niu, Li-qin | Jia, Pu | Li, Shao-peng | Kuang, Jia-liang | He, Xiao-xin | Zhou, Wen-hua | Liao, Bin | Shu, Wen-sheng | Li, Jin-tian
Heavy metal contamination of agricultural soils is of worldwide concern. Unfortunately, there are currently no efficient and sustainable approaches for addressing this concern. In this study, we conducted a field experiment in which an agricultural soil highly contaminated by cadmium (Cd), lead (Pb) and zinc (Zn) was treated on-site by an ancient agricultural technique, ‘slash-and-char’, that was able to convert the biomass feedstock (rice straw) into biochar in only one day. We found evidence that in comparison to the untreated soil, the treated soil was associated with decreased bioavailability of the heavy metals and increased vegetable yields. Most importantly, the treatment was also coupled with dramatic reductions in concentrations of the heavy metals in vegetables, which made it possible to produce safe crops in this highly contaminated soil. Collectively, our results support the idea that slash-and-char offers new promise for management of soils contaminated by Cd, Pb and Zn.
Show more [+] Less [-]Soil Pollution Due to Irrigation with Arsenic-Contaminated Groundwater: Current State of Science
2015
Gillispie, Elizabeth C. | Sowers, Tyler D. | Duckworth, Owen W. | Polizzotto, Matthew L.
Food with elevated arsenic concentrations is becoming widely recognized as a global threat to human health. This review describes the current state of knowledge of soil pollution derived from irrigation with arsenic-contaminated groundwater, highlighting processes controlling arsenic cycling in soils and resulting arsenic impacts on crop and human health. Irrigation practices utilized for both flooded and upland crops have the potential to load arsenic to soils, with a host of environmental and anthropogenic factors ultimately determining the fate of arsenic. Continual use of contaminated groundwater for irrigation may result in soils with concentrations sufficient to create dangerous arsenic concentrations in the edible portions of crops. Recent advances in low-cost water and soil management options show promise for mitigating arsenic impacts of polluted soils. Better understanding of arsenic transfer from soil to crops and the controls on long-term soil arsenic accumulation is needed to establish effective arsenic mitigation strategies within vulnerable agronomic systems.
Show more [+] Less [-]Application of Stabilized Nanoparticles for In Situ Remediation of Metal-Contaminated Soil and Groundwater: a Critical Review
2015
Liu, Wen | Tian, Shuting | Zhao, Xiao | Xie, Wenbo | Gong, Yanyan | Zhao, Dongye
Remediation of soil and groundwater contaminated with toxic metals has been a major environmental challenge for decades. Yet, cost-effective and sustainable in situ remediation technologies remain lacking. Over the last 15 years or so, an innovative in situ remediation strategy has shown promising by means of stabilized nanoparticles. Stabilized nanoparticles are prepared using novel stabilizers that facilitate the deliverability and transport of nanoparticles in the subsurface. This study reviews synthesis and characterization of some model stabilized nanoparticles and their application for remediation of metal-contaminated soil and water. Fate and transport of these stabilized nanoparticles in groundwater and soil are also examined. Lastly, this review identifies the key knowledge gaps such as lack of field data pertaining to the long-term effectiveness of the immobilized metals and impacts of the delivered nanoparticles on the biogeochemical conditions in the subsurface. The information may facilitate further development of this promising remediation technology.
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