Enantioselective Carbon Stable Isotope Fractionation of Hexachlorocyclohexane during Aerobic Biodegradation by <i>Sphingobium</i> spp.

Carbon isotope fractionation was investigated for the biotransformation of γ- and α- hexachlorocyclohexane (HCH) as well as enantiomers of α-HCH using two aerobic bacterial strains: <i>Sphingobium indicum</i> strain B90A and <i>Sphingobium japonicum</i> strain UT26. Carbon isotope enrichment factors (ε_c) for γ-HCH (ε_c = −1.5 ± 0.1‰ and −1.7 ± 0.2‰) and α-HCH (ε_c = −1.0 ± 0.2‰ and −1.6 ± 0.3‰) were similar for both aerobic strains, but lower in comparison with previously reported values for anaerobic γ- and α-HCH degradation. Isotope fractionation of α-HCH enantiomers was higher for (+) α-HCH (ε_c = −2.4 ± 0.8 ‰ and −3.3 ± 0.8 ‰) in comparison to (−) α-HCH (ε_c = −0.7 ± 0.2‰ and −1.0 ± 0.6‰). The microbial fractionation between the α-HCH enantiomers was quantified by the Rayleigh equation and enantiomeric fractionation factors (ε_e) for <i>S. indicum</i> strain B90A and <i>S. japonicum</i> strain UT26 were −42 ± 16% and −22 ± 6%, respectively. The extent and range of isomer and enantiomeric carbon isotope fractionation of HCHs with <i>Sphingobium</i> spp. suggests that aerobic biodegradation of HCHs can be monitored in situ by compound-specific stable isotope analysis (CSIA) and enantiomer-specific isotope analysis (ESIA). In addition, enantiomeric fractionation has the potential as a complementary approach to CSIA and ESIA for assessing the biodegradation of α-HCH at contaminated field sites

Compound Specific and Enantioselective Stable Isotope Analysis as Tools To Monitor Transformation of Hexachlorocyclohexane (HCH) in a Complex Aquifer System

Technical hexachlorocyclohexane (HCH) mixtures and Lindane (γ-HCH) have been produced in Bitterfeld-Wolfen, Germany, for about 30 years until 1982. In the vicinity of the former dump sites and production facilities, large plumes of HCHs persist within two aquifer systems. We studied the natural attenuation of HCH in these groundwater systems through a combination of enantiomeric and carbon isotope fractionation to characterize the degradation of α-HCH in the areas downstream of a former disposal and production site in Bitterfeld-Wolfen. The concentration and isotope composition of α-HCH from the Quaternary and Tertiary aquifers were analyzed. The carbon isotope compositions were compared to the source signal of waste deposits for the dumpsite and highly contaminated areas. The average value of δ¹³C at dumpsite was −29.7 ± 0.3 ‰ and −29.0 ± 0.1 ‰ for (−) and (+)­α-HCH, respectively, while those for the β-, γ-, δ-HCH isomers were −29.0 ± 0.3 ‰, −29.5 ± 0.4 ‰, and −28.2 ± 0.2 ‰, respectively. In the plume, the enantiomer fraction shifted up to 0.35, from 0.50 at source area to 0.15 (well T1), and was found accompanied by a carbon isotope enrichment of 5 ‰ and 2.9 ‰ for (−) and (+)­α-HCH, respectively. The established model for interpreting isotope and enantiomer fractionation patterns showed potential for analyzing the degradation process at a field site with a complex history with respect to contamination and fluctuating geochemical conditions

Glyphosate in the environment: interactions and fate in complex soil and water settings, and (phyto) remediation strategies

Glyphosate (Gly) and its formulations are broad-spectrum herbicides globally used for pre- and post-emergent weed control. Glyphosate has been applied to terrestrial and aquatic ecosystems. Critics have claimed that Gly-treated plants have altered mineral nutrition and increased susceptibility to plant pathogens because of Gly ability to chelate divalent metal cations. Still, the complete resistance of Gly indicates that chelation of metal cations does not play a role in herbicidal efficacy or have a substantial impact on mineral nutrition. Due to its extensive and inadequate use, this herbicide has been frequently detected in soil (2 mg kg−1, European Union) and in stream water (328 µg L−1, USA), mostly in surface (7.6 µg L−1, USA) and groundwater (2.5 µg L−1, Denmark). International Agency for Research on Cancer (IARC) already classified Gly as a category 2 A carcinogen in 2016. Therefore, it is necessary to find the best degradation techniques to remediate soil and aquatic environments polluted with Gly. This review elucidates the effects of Gly on humans, soil microbiota, plants, algae, and water. This review develops deeper insight toward the advances in Gly biodegradation using microbial communities. This review provides a thorough understanding of Gly interaction with mineral elements and its limitations by interfering with the plants biochemical and morphological attributes. Glyphosate (Gly) contamination in water, soil, and crops is an eminent threat globally. Various advanced and integrated approaches have been reported to remediate Gly contamination from the water-soil-crop system. This review elucidates the effects of Gly on human health, soil microbial communities, plants, algae, and water. This review develops deeper insight into the advances in Gly biodegradation using microbial communities, particularly soil microbiota. This review provides a brief understanding of Gly interaction with mineral elements and its limitations in interfering with the plants biochemical and morphological attributes.</p

Phosphate-assisted phytoremediation of arsenic by <i>Brassica napus</i> and <i>Brassica juncea</i>: Morphological and physiological response

<p>In this study, we examined the potential role of phosphate (P; 0, 50, 100 mg kg⁻¹) on growth, gas exchange attributes, and photosynthetic pigments of <i>Brassica napus</i> and <i>Brassica juncea</i> under arsenic (As) stress (0, 25, 50, 75 mg kg⁻¹) in a pot experiment. Results revealed that phosphate supplementation (P100) to As-stressed plants significantly increased shoot As concentration, dry biomass yield, and As uptake, in addition to the improved morphological and gas exchange attributes and photosynthetic pigments over P0. However, phosphate-assisted increase in As uptake was substantially (up to two times) greater for <i>B. napus</i>, notably due to higher shoot As concentration and dry biomass yield, compared to <i>B. juncea</i> at the P100 level. While phosphate addition in soil (P100) led to enhanced shoot As concentration in <i>B. juncea</i>, it reduced shoot dry biomass, primarily after 50 and 75 mg kg⁻¹ As treatments. The translocation factor and bioconcentration factor values of <i>B. napus</i> were higher than <i>B. juncea</i> for all As levels in the presence of phosphate. This study demonstrates that phosphate supplementation has a potential to improve As phytoextraction efficiency, predominantly for <i>B. napus</i>, by minimizing As-induced damage to plant growth, as well as by improving the physiological and photosynthetic attributes.</p