Grain transportation and consumption reshapes the α-HCH exposure picture of China.

Socio-economic activities like food trade can increase the uncertainty of human risk of persistent organic pollutants (POPs). We compared the change in model predicted α-hexachlorocyclohexane (α-HCH) cancer risk (CR) with and without grain trade in mainland China. In scenario without grain logistics, α-HCH moved fast away from southern and southeastern China via northward atmospheric transport. However, the grain logistics from northeastern China delivers the α-HCH previously accumulated in northeastern sink back to densely populated areas in recent years, which enhance CR by >50 % in the southern seaboard of China. The northward movement of grain production center and recent grain deficiency in southern provinces induced by dietary pattern changes is identified as the major driving factors of the reversed transport of α-HCH. The finding highlights the potential of socio-economic activities that can otherwise offset the risk reduction effect of the geochemical cycle of POPs.

Pesticides in surface water of the Ondas river watershed, western Bahia, Brazil: Spatial-seasonal distribution and risk assessment.

This study investigated the occurrence and seasonal distribution of different classes of pesticides in surface waters of the Ondas River Watershed, as well as potential risks to the aquatic health and human water consumption in the western region of Bahia state, Brazil. Two gas chromatography-mass spectrometry analytical methods were applied to monitor 34 pesticides in water samples collected during both the dry and rainy seasons at 17 sites. Upon individual analysis, only γ-HCH, methoxychlor, demeton-S, methyl parathion, fenitrothion, chlorpyrifos, and azoxystrobin exhibited statistically significant differences between seasons. During rainy season, concentration medians of residues were higher for γ-HCH (74.7 ng L-1), methoxychlor (25.1 ng L-1), and azoxystrobin (47.2 ng L-1), potentially linked to historical contamination or illegal use. Conversely, pesticides like methyl parathion, fenitrothion, and chlorpyrifos, belonging to the organophosphate class, showed higher concentration medians in the dry period, measuring 75.1, 5.50, and 10.8 ng L-1, respectively, probably due to region crop activities. The risk quotient (RQ) assessment for aquatic life indicated that 59.0% of the samples in the dry season and 76.0% in the rainy season had RQ values greater than one, signifying a critical scenario for species conservation. Regarding human consumption, elevated risks were observed for heptachlor in both sampling periods and for azoxystrobin during the rainy season, surpassing RQ levels above 1, indicating danger in untreated water ingestion. Additionally, 24.0% and 53.0% of the samples in the dry and rainy seasons, respectively, contained at least one pesticide exceeding the EU resolution limit (100 ng L-1). Therefore, considering this information, implementing mitigation measures to avoid the river's contamination becomes imperative.

Chemical analysis of wetland plants to evaluate the bioaccumulation and metabolism of hexachlorocyclohexane (HCH).

Hexachlorocyclohexanes (HCH) belong to the banned pesticides with short-time production and use during the last century. However, the consequences of this short period are still present as persistent environmental contamination. This study represents the large lab-scale experiment focused on the HCH accumulation and metabolism in selected wetland plants (Juncus effuses, Typha latifolia, Phragmites australis) and trees (Alnus glutinosa) after the exposure to the technical mix of HCH isomers (t-HCH) or δ-HCH at three different concentration. During the three-month exposure, morphological (biomass, height, relative chlorophyll content) and physiological (photosynthetic measurements - photosynthetic rate, stomatal conductance, transpiration and dark transpiration) parameters were measured to assess the HCH effect on plant's growth. The results showed that all selected plant species supported HCH removal from the soil. The total removal efficiency was lower for the t-HCH than for δ-HCH exposure, and the best results were provided by Alnus glutinosa tree. Also, no isomer preference was observed in plants exposed to t-HCH. Most HCH remained accumulated in the root biomass, and mainly α-HCH and δ-HCH were transported to the above-ground parts due to their physicochemical properties. Simultaneously, HCH uptake and metabolization to chlorobenzenes (CB) and chlorophenols (CP) occur. Non-targeted analysis showed that CP could be conjugated to glucose and malonyl in plant tissue, and secondary plant metabolism is affected positively and negatively after exposure to t-HCH depending on plant species and chemical concentration. Luteolin, quercetin and quercetin-3-O-glucoside found common to all species showed quantitative changes due to HCH. Nevertheless, most morphological and physiological parameters were adversely affected without statistical significance. This large-scale study provides information on the fate of HCH in the soil-plant system, the suitability of selected plants and their adaptation to chemical stress for use in the phytoremediation process.

Assessing HCH isomer uptake in Alnus glutinosa: implications for phytoremediation and microbial response.

Although the pesticide hexachlorocyclohexane (HCH) and its isomers have long been banned, their presence in the environment is still reported worldwide. In this study, we investigated the bioaccumulation potential of α, ß, and δ hexachlorocyclohexane (HCH) isomers in black alder saplings (Alnus glutinosa) to assess their environmental impact. Each isomer, at a concentration of 50 mg/kg, was individually mixed with soil, and triplicate setups, including a control without HCH, were monitored for three months with access to water. Gas chromatography-mass spectrometry revealed the highest concentrations of HCH isomers in roots, decreasing towards branches and leaves, with δ-HCH exhibiting the highest uptake (roots-14.7 µg/g, trunk-7.2 µg/g, branches-1.53 µg/g, leaves-1.88 µg/g). Interestingly, α-HCH was detected in high concentrations in ß-HCH polluted soil. Phytohormone analysis indicated altered cytokinin, jasmonate, abscisate, and gibberellin levels in A. glutinosa in response to HCH contamination. In addition, amplicon 16S rRNA sequencing was used to study the rhizosphere and soil microbial community. While rhizosphere microbial populations were generally similar in all HCH isomer samples, Pseudomonas spp. decreased across all HCH-amended samples, and Tomentella dominated in ß-HCH and control rhizosphere samples but was lowest in δ-HCH samples.

Placental concentrations of xenoestrogenic organochlorine pesticides and polychlorinated biphenyls and assessment of their xenoestrogenicity in the PA-MAMI mother-child cohort.

BACKGROUND: Organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCB), they have contributed to the exposure of women to persistent organic pollutants (POPs). These compounds can cross the placental barrier and interfere with the hormonal system of newborns. AIM: To determine concentrations of OCPs and PCBs and their xenoestrogenic activity in placentas of women from the PA-MAMI cohort of Panama. METHODS: Thirty-nine placenta samples from women in the Azuero peninsula (Panama) were analyzed. Five OCPs [p-p'-dichlorodiphenyldichloroethylene (p-p'-DDE), beta-hexachlorohexane (ß-HCH), γ-hexachlorohexane (lindane), hexachlorobenzene (HCB) and mirex] and three PCB congeners (PCB-138, PCB-153 and PCB-180) were quantified in placenta extracts. The xenoestrogenic activity of extracts was assessed with the E-Screen bioassay to estimate the total effective xenoestrogen burden (TEXB). RESULTS: All placental samples were positive for at least three POP residues and >70% for at least six. The frequencies of quantified OCPs ranged from 100% for p,p'-DDE and HCB to 30.8% for ß-HCH. The highest median concentration was for lindane (380.0 pg/g placenta), followed by p,p'-DDE (280.0 pg/g placenta), and HCB (90.0 pg/g placenta). Exposure to p,p'-DDE was associated with greater meat consumption, suggesting that animal fat is a major source of exposure to DDT metabolites. The frequency of detected PCBs ranged between 70 and 90%; the highest median concentration was for PCB 138 (17.0 pg/g placenta), followed by PCB 153 (16.0 pg/g placenta). All placentas were positive in the estrogenicity bioassay with a median TEXB-α of 0.91 pM Eeq/g of placenta. Exposure to lindane was positively associated with the xenoestrogenicity of TEXB- α, whereas this association was negative in the case of exposure to PCB 153. CONCLUSIONS: To our best knowledge, this study contributes the first evidence on the presence of POPs and xenoestrogenic burden in placentas from Latin-American women. Given concerns about the consequences of prenatal exposure to these compounds on children's health, preventive measures are highly recommended to eliminate or minimize the risk of OCP exposure during pregnancy.

Selected pesticidal POPs and metabolites in the soil of five Vietnamese cities: Sources, fate, and health risk implications.

Large quantities of organochlorine pesticides (OCPs) have been used in tropical regions. The fate processes and risks of these legacy contaminants in the tropics are poorly understood. Herein, we investigated the occurrence of three classes of widely used OCPs and their metabolites in surface and core soil from five cities across Vietnam with a prevalent tropical monsoon climate and a long history of OCP application. We aimed to elucidate migration potentials, degradation conditions, and transformation pathways and assess current health risks of these contaminants. Generally, the concentrations of OCPs and metabolites in the soil core were slightly lower than those in surface soil except for hexachlorocyclohexane (HCH) isomers. 2,2-bis(4-chlorophenyl)-1,1,1-trichloroethane (p,p'-DDT), 2,2-bis(4-chlorophenyl)-1,1-dichloroethylene (p,p'-DDE), the sum of dicofol and 4,4'-dichlorobenzophenone (p,p'-DBP), and 2,2-bis(4-chlorophenyl)-1,1-dichloroethane (p,p'-DDD) were the most abundant compounds in both surface and core soils. A uniform distribution of HCHs (the sum of α-, ß-, γ-, and δ-HCH) at trace levels was found in almost all soils, serving as evidence of the lack of recent use of HCH pesticides. Higher concentrations of DDTs (the sum of DDT, DDD, and DDE) were observed in north-central Vietnamese soil, whereas appreciable concentrations of ENDs (the sum of α- and ß-endosulfan and endosulfan sulfate) were only found in southern Vietnamese soils. Empirical diagnostic ratios indicated residuals of DDTs were mainly from technical DDT rather than dicofol, whereas aged HCHs could be explained by the mixture of lindane and technical HCH. Both historical applications and recent input explain DDTs and ENDs in Vietnamese soil. Total organic carbon performs well in preventing vertical migration of more hydrophobic DDTs and ENDs. The dominant transformation pathway of DDT in surface soil followed p,p'-DDE→2,2-bis(4-chlorophenyl)-1-chloroethylene or p,p'-DDMU→1,1-bis(4-chlorophenyl)ethylene or p,p'-DDNU→p,p'-DBP, whereas the amount of p,p'-DDMU converted from p,p'-DDD and p,p'-DDE is similar in soil core. Non-cancer risks of OCPs and metabolites in all soils and cancer risks of those chemicals in core soils were below the safety threshold, whereas a small proportion of surface soil exhibited potential cancer risk after considering the exposure pathway of vegetable intake. This study implied that organic matter in non-rainforest tropical deep soils still could hinder the leaching of hydrophobic organic contaminants as in subtropical and temperate soils. When lands with a history of OCP application are used for agricultural purposes, dietary-related risks need to be carefully assessed.

Reduced attention on restricted organochlorine pesticides, whereas still noteworthy of the impact on the deep soil and groundwater: a historical site study in southern China.

The use of hexachlorocyclohexanes (HCHs) in pesticides has been prohibited for decades in China. Since then, there have been urbanization and transformation of the functional areas of many sites, which were formerly involved in the HCH industry. However, it is possible that, unless properly managed, these sites may still contain HCH residues in the soil and thus pose a threat to the surrounding environment and the quality of groundwater. This study aimed to characterize soil residues in a typical site that was historically involved in HCH production in southern China, by analyzing the α-HCH, ß-HCH, and γ-HCH contents of the soil. The results suggested that HCHs persist in the environment and can have long-term effects. It was found that α-HCH and ß-HCH were present in many samples in concentrations that were comparable or higher than those specified by China's Class 1 screening values. The distribution of residues was significantly correlated with the historical HCH production activities in the areas. The characteristic ratios of α-HCH/γ-HCH and ß-HCH/(α + γ)-HCH at different soil depths were 1.4-3.7 and 0.21-1.04, respectively, which indicated the presence of significant localized residues of HCHs. The presence of HCHs in the soil suggested a downward migration, with concentrations rapidly decreasing in the upper layer soil (0-5 m), but a gradual increase in the deeper soil (5-14 m). HCHs were detected at depths exceeding 24 m, indicating heavy penetration. The proportions of γ-HCH and ß-HCH changed with increasing soil depth, which was related to their relatively volatile and stable molecular structures, respectively. The results strongly suggested that there is widespread contamination of both soil and groundwater by HCHs even after decades. The likelihood of residual HCHs in the soil should therefore be taken into full consideration during urban planning to limit risks to human and environmental health.

Bioaccumulation of pesticide residue in earthworms collected from the agricultural soils of Kuttanad-a unique agroecosystem in India.

Earthworms encompass significant soil faunal biomass and have tremendous potential to provide vital ecosystem services. Earthworms are considered bioindicators of chemical contaminants and can provide early warnings of ecosystem deterioration. Studies pertaining to the accumulation of pesticide residues in earthworm in biomass in agrarian ecosystems are scarce. The Kuttanad agroecosystem (KAE), situated on the southwest coast of India, is one of the few regions globally supporting farming on land below the mean sea level. This investigation was conducted to assess the bioaccumulation of pesticide residues in earthworms from the KAE. The earthworms species Glyphidrilus annandalei collected from agricultural soils of the study area were analyzed for the presence of pesticides residues such as α-BHC, γ-BHC, atrazine, heptachlor, α-chlordane, γ-chlordane, 4,4-DDE, 4,4-DDD, 4,4-DDT, ß-endosulfan, and endrin ketone in their biomass. Analysis of the earthworm samples using a gas chromatograph revealed the presence of ten pesticide residues with notable concentrations (α-BHC, 0.36 ng/g; γ-BHC, 0.41 ng/g; heptachlor, 0.10 ng/g; atrazine, 0.89 ng/g; α-chlordane, 0.07 ng/g; γ-chlordane, 0.10 ng/g; 4,4-DDE, 0.05 ng/g; 4,4-DDD, 0.11 ng/g; 4,4-DDT, 0.31 ng/g; ß-endosulfan, 0.19 ng/g; and endrin ketone, 0.13 ng/g). Six groups of pesticide residues are ΣBHC, ΣDDT, atrazine, Σchlordane, endrin ketone, and ß-endosulfan were observed during bioaccumulation factor analysis, and the results show the following trend: atrazine > ΣBHC > ΣDDT > Σchlordane > Σendosulfan > Σendrin. As earthworms are a crucial component of this region's food chains, bioaccumulation of pesticide residues in earthworms can pause adverse consequences. Increasing trends in pesticide application in the KAE and bioaccumulation of pesticide residues in earthworm biomass can affect the entire food web.

Monitoring of some organochlorine residues in raw bovine milk in the west Delta area, Egypt.

Background: For decades, the use of organochlorine (OC) pesticides has had a detrimental effect on the environment and human health. Contamination of soil, water, and air has also resulted in contaminated milk. Aim: The purpose of this study was to investigate if any OC residues dichlorodiphenyltrichloroethane (DDT, Dieldrin, Endrin, and Lindane) were present in raw bovine milk from West Delta, Egypt. Methods: 200 fresh raw cow milk samples (500 ml of each sample) collected from three different governorates, west Delta, Egypt, for determination of OC pesticides residues using gas chromatography with an Agilent 6890A model gas chromatograph equipped with a 63Ni microelectron capture detector. Results: The obtained results revealed that åDDT, dieldrin, endrin, and lindane were detected in Alexandria, Behera, and Matrouh at incidence levels (22.7%, 30.7%, and 10%), (20%, 20%, and 16%), (9.33%, 13.3%, and 16%), and (12%, 10.7%, and 14%) with mean values of 232.2 ± 163.6, 156.4 ± 134.6 and 100.4 ± 85.9; 91.3 ± 61.2, 95.3 ± 59.8 and 57.6 ± 3.33; 15.7± 3.86, 15.1 ± 3.96 and 20.1 ± 7.33; 33.7 ± 10.6, 36.9 ± 5.51 and 52.2 ± 21.8 ng/g fat, respectively. El-Behera was the most contaminated province with an incidence level of 53.3% with a mean value of 136.8 ± 128.0 ng/g fat, followed by Alexandria at 44% with a mean value of 173.7 ± 155.5 ng/g fat, and finally, Matrouh 40% with a mean value of 74.5 ± 56.5 ng/g fat. Conclusion: This research demonstrated that milk samples contain varying levels of OC pesticide residues, which can be hazardous to consumer health. Therefore, to safeguard consumers, especially children, and the elderly, OC pesticide residues in milk must be closely monitored.

Microplastic-sorbed persistent organic pollutants in coastal Mediterranean Sea areas of Tunisia.

Microplastics (MPs) are emerging pollutants of global concern due to their pervasiveness, high sorption ability for persistent organic pollutants (POPs) and direct and indirect toxicity to marine organisms, ecosystems, as well as humans. As one of the major coastal interfaces, beaches are considered among the most affected ecosystems by MPs pollution. The morphological characteristics of MPs (pellets and fragments) collected from four beaches along the Tunisian coast and sorbed POPs, including polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs), were investigated in this study. The results showed that the MPs varied greatly in color, polymer composition and degradation degree. The color varied from colored to transparent and the most prevalent polymer identified using Raman spectroscopy was polyethylene. Scanning electron microscope (SEM) images exhibited various surface degradation features including cavities, cracks, attached diatom remains, etc. The concentrations of Σ12PCBs over all beaches ranged from 14 to 632 ng g-1 and 26 to 112 ng g-1 in the pellets and fragments, respectively, with a notable presence and dominance of highly-chlorinated PCBs such as CB-153 and -138. Among the OCPs, γ-HCH is the only compound detected with concentrations ranging from 0.4 to 9.7 ng g-1 and 0.7 to 4.2 ng g-1 in the pellets and fragments, respectively. Our findings indicate that MPs found on the Tunisian coast may pose a chemical risk to marine organisms as the concentrations of PCBs and γ-HCH in most of the analysed samples exceeded the sediment-quality guidelines (SQG), especially the effects range medium (ERM) and the probable effects level (PEL). As the first report of its kind, the information gathered in this study can serve as the baseline and starting point for future monitoring work for Tunisia and neighbouring countries, as well as for stakeholders and coastal managers in decision-making processes.

Effective degradation of lindane and its isomers by dielectric barrier discharge (DBD) plasma: Synergistic effects of various reactive species.

Lindane is a broad-spectrum organochlorine insecticide which has been included in the persistent organic pollutants (POPs) list together with its two hexachlorocyclohexane (HCH) isomers. Due to its continuous use in the past decades, the environmental impacts of HCHs are still severe now. Therefore, in the present study, dielectric barrier discharge (DBD) plasma was used as an advanced oxidation process for the destruction of HCHs in water. The result indicated that in air-DBD system, over 95.4% of the initial 5 mg L-1 lindane was degraded within 60 min. Moreover, DBD plasma displayed high degradation efficiencies of other HCH isomers including α, ß, and δ-HCH. Electron spin resonance spectra, scavenging experiments and theoretical calculations revealed that the synergistic effects of various reactive species were the main reason for the high efficiency of DBD plasma. For instance, both hydroxyl radicals (•OH) and electrons (e-) could initiate the degradation of HCHs, while other reactive species such as 1O2 and ONOOH played important roles in the decomposition of intermediates. Therefore, the present study not only provided an effective approach for the treatment of HCHs, but also revealed the underlying mechanism based on in-depth experimental investigation and theoretical calculation.

Spatial redistribution and enantiomeric signatures of hexachlorocyclohexanes in Chinese forest soils: Implications to environmental behavior and influencing factors.

Hexachlorocyclohexanes (HCHs) are a group of highly persistent pesticides. The concentrations of HCHs and the enantiomeric fractions of α-HCH in the O- and A-horizons from 30 mountains across China were analyzed in this study. The concentrations of total HCHs ranged from 0.061 to 46.9 ng/g (mean 2.12 ng/g) and 0.046 to 16.1 ng/g (mean 0.792 ng/g) in the O- and A-horizons, respectively. The HCH residues were mainly derived from the historical applications of technical HCH and lindane. Higher concentrations of HCHs were typically found in northern China, and no significant correlations were found between historical technical HCH usage and HCH isomer concentrations in either the O- or A-horizons (p > 0.05). Conversely, the concentrations of HCH isomers were significantly correlated with the environmental parameters (temperature and precipitation), thus indicating a typical secondary distribution pattern. Some HCH isomers tended to be transported northward under the long-term effect of monsoon. Chiral α-HCH was non-racemic in soils and showed preferential degradation of (-) α-HCH in both the O- and A-horizons. The transformation from γ-HCH to α-HCH might alter the enantiomeric signatures of α-HCH in soils. Moreover, the deviation from racemic of α-HCH was positively correlated with the C/N ratio in the A-horizon (p < 0.01), thus suggesting that the C/N ratio could alter the microbial activity and significantly affect the enantioselective degradation extent of α-HCH in soils.

Effects of irrigation with HCH-contaminated water on crop performance and HCH accumulation in plant and soil.

Lindane production is very ineffective since, for each ton of lindane obtained, between 6 and 10 tons of hexachlorocyclohexane (HCH) isomers and other toxic compounds are produced. Due to the disposal of these residues, contaminated zones still exist, and many dumpsites are close to rivers and water reservoirs. The current study examines the consequences of irrigating pea, maize, and alfalfa, with water containing different HCH concentrations on the accumulation of HCH in plant material and soils. The experiments were conducted on pots under controlled conditions using drinking water (as reference) and water with several HCH concentrations: 0.5 µg L-1 (the maximum threshold allowed for human consumption), 2.5 µg L-1, 5 µg L-1, and 20 µg L-1. Results showed that both surface and overhead irrigation with these HCH concentrations did not cause any toxicity effects on the considered crops. However, under overhead irrigation with HCH concentrations higher than 5 µgL-1 HCH is absorbed by maize leaves and its concentration in plant biomass surpassed the EU maximum residue level of 10 µg kg-1. In the case of fodder maize, an HCH concentration of 0.84 µg L-1 in irrigation water produced an HCH concentration in plant above 20 µg kg-1 dry matter, the upper threshold established in the Spanish legislation, that limits the use for animal feeding. In the case of alfalfa, HCH was detected in treatments with the highest HCH concentration (13 µg L-1) under surface irrigation, but concentration was below the EU maximum residue level. In conclusion, in overhead irrigated systems, water with HCH concentrations below 5 µg L-1 does not produce HCH accumulation in pea and maize grain above the maximum residue levels; however, for fodder maize, the HCH concentration in irrigation water should be controlled to avoid HCH accumulation in plants above the limit for animal feeding.

Distribution of organochlorine pesticides in surface and deep waters of the Southern Indian Ocean and coastal Antarctic waters.

Antarctica is a remote and pristine region. Yet it plays a vital role in biogeochemical cycles of global anthropogenic contaminants, such as persistent organic pollution (POPs). This work reports the distribution of legacy and new POPs in surface and depth profiles/deeper water of the Southern Indian Ocean (SIO) and the coast of Antarctica (COA). Samples were collected during the 10th Indian Southern Ocean expedition (SOE-10) in the year 2017. Concentrations of ∑HCH (hexachlorocyclohexane), ∑DDT (dichlorodiphenyltrichloroethane), and ∑ENDO (endosulfan) in surface seawater from the SIO region ranged between not detected (ND) to 1.21 pg/Liter (pg L-1) (average. ± s.d.: 0.35 ± 0.42 pg L-1), ND to 1.83 pg L-1 (0.69 ± 84 pg L-1), and ND - to 2.06 pg L-1 (0.56 ± 0., 88 pg L-1), respectively. The concentrations of ∑HCH, ∑DDT, and ∑ENDO in COA ranged from ND to 0.98 pg L-1 (0.25 ± 0.27 pg L-1), ND to 3.61 pg L-1(0.50 ± 1.08 pg L-1), and ND to 2.09 pg L-1 (0.45 ± 0.84 pg L-1), respectively. Concentrations of isomers of endosulfan, and largely of HCHs, suggested an aged source. Some concentration ratios of α-to γ-HCH were close to 1, indicating a contribution from ongoing sources. Results indicate the important role of ocean currents in mediating the transport and detection of OCPs. As such, OCPs dynamics in deeper oceans may play an important role in OCPs cycling in the marine environment.

Good News: Some Insecticides Have Been Virtually Eliminated in Air near the Great Lakes.

Persistent insecticides have been classic environmental problems for 60-70 years─perhaps starting with Rachel Carson's indictment of DDT. Both national and international regulations have been put in place over the last 20-30 years to eventually eliminate these compounds from the environment. One focus is the atmosphere, which acts as a major long-range transport route of these pollutants from their numerous sources to many ecosystems. This paper will ask, "Have we have made any progress in eliminating insecticides from the atmosphere?" We will focus only on the atmosphere around the North American Great Lakes and only on concentration measurements made once every 12 days since about 1990 for six classic insecticides. The answer is that some of these compounds (lindane, α-HCH, and endosulfans) are well on their way to being virtually eliminated, while the concentrations of others (DDT, chlordane, and hexachlorobenzene) have not changed much. We speculate that this difference in elimination is a result of soil compaction in cities (DDT, etc.) versus soil mixing in rural areas (lindane, etc.).

Compound-specific stable isotope analysis for characterization of the transformation of γ-HCH induced by biochar.

The role of biochar as the redox catalyst in the removal of reductive pollutants from soil and water system has been extensively studied recently, but there is still a lack of qualitative description of its specific mechanisms in redox processes. In this study, the mechanism of biochar in the transformation process of γ-HCH under anoxic condition was revealed by the compound-specific isotope analysis. The concentration and carbon isotopic composition (δ13C) of γ-HCH were detected in the treatments with different initial concentrations of γ-HCH and biochar materials with different redox properties and varied doses. The surface functional groups and electrochemical properties of biochar before and after the reaction were also characterized. The addition amount of biochar could affect the reduction of γ-HCH concentration, which were 59.1%, 34.6% and 22.4% in treatments with the addition of 5%, 1% and 0.2% biochar, respectively. Meanwhile, the δ13C value of γ-HCH also increased from -26.6 ± 0.2‰ to -23.8 ± 0.2‰ with the addition amount of biochar, especially in the treatment with 5% biochar. As evidenced by X-ray diffraction analysis and electrochemical analysis, biochar promoted the adsorption and transformation of γ-HCH simultaneously, and the oxygen-containing functional groups on the surface of biochar played an important role in the redox process. The isotopic fractionation value (εC) of γ-HCH transformation by biochar was first reported as -3.4 ± 0.4‰. The results will enable the quantitative description of the transformation degree of organic pollutants induced by biochar, and provide a new approach for evaluating the in-situ remediation effects of biochar in a complex environment.

Mycelial nutrient transfer promotes bacterial co-metabolic organochlorine pesticide degradation in nutrient-deprived environments.

Biotransformation of soil organochlorine pesticides (OCP) is often impeded by a lack of nutrients relevant for bacterial growth and/or co-metabolic OCP biotransformation. By providing space-filling mycelia, fungi promote contaminant biodegradation by facilitating bacterial dispersal and the mobilization and release of nutrients in the mycosphere. We here tested whether mycelial nutrient transfer from nutrient-rich to nutrient-deprived areas facilitates bacterial OCP degradation in a nutrient-deficient habitat. The legacy pesticide hexachlorocyclohexane (HCH), a non-HCH-degrading fungus (Fusarium equiseti K3), and a co-metabolically HCH-degrading bacterium (Sphingobium sp. S8) isolated from the same HCH-contaminated soil were used in spatially structured model ecosystems. Using 13C-labeled fungal biomass and protein-based stable isotope probing (protein-SIP), we traced the incorporation of 13C fungal metabolites into bacterial proteins while simultaneously determining the biotransformation of the HCH isomers. The relative isotope abundance (RIA, 7.1-14.2%), labeling ratio (LR, 0.13-0.35), and the shape of isotopic mass distribution profiles of bacterial peptides indicated the transfer of 13C-labeled fungal metabolites into bacterial proteins. Distinct 13C incorporation into the haloalkane dehalogenase (linB) and 2,5-dichloro-2,5-cyclohexadiene-1,4-diol dehydrogenase (LinC), as key enzymes in metabolic HCH degradation, underpin the role of mycelial nutrient transport and fungal-bacterial interactions for co-metabolic bacterial HCH degradation in heterogeneous habitats. Nutrient uptake from mycelia increased HCH removal by twofold as compared to bacterial monocultures. Fungal-bacterial interactions hence may play an important role in the co-metabolic biotransformation of OCP or recalcitrant micropollutants (MPs).

Removal of lindane in liquid culture using soil bacteria and toxicity assessment in human skin fibroblast and HCT116 cell lines.

The development of effective measures for the remediation of lindane contaminated sites is the need of the hour. In this study, a potent lindane degrading bacteria, identified as Rhodococcus rhodochrous NITDBS9 was isolated from an agricultural field of Odisha that could utilize up to 87% of 100 mg L-1 lindane when grown under liquid culture conditions in mineral salt media in 10 days. The bacteria could produce biofilm in lindane-containing media. Rhodococcus rhodochrous NITDBS9 was further characterized for its plant growth-promoting properties and it was found that the bacteria showed abilities for phytohormone, ammonia and biosurfactant production, etc. This could be beneficial for the bioremediation and improvement of crop production in contaminated sites. Ecotoxicity studies carried out for lindane, and its degradation products in mung bean and mustard seeds showed a reduction in toxicity of lindane after treatment with NITDBS9. NITDBS9 was used with a previously isolated potent lindane degrading strain Paracoccus sp. NITDBR1 in a dual mixed culture for the enhanced removal of lindane in the liquid system i.e. up to 93% in 10 days. Cytotoxicity studies were conducted with lindane before and after treatment with the single and dual mixed cultures on human skin fibroblast and HCT116 cell lines. They revealed a significant reduction in toxicity of lindane after it was bioremediated with the single and dual mixed cultures. Therefore, our proposed strategy could be efficiently used for the detoxification of the lindane-contaminated system, and further work should be done to study the use of these cultures in the contaminated soil system.

Comprehensive study of acute toxicity using Microtox® bioassay in soils contaminated by lindane wastes.

This research studies the acute toxicity of real contaminated soils (topsoil and subsoil) with hazardous chlorinated organic compounds (COCs) from lindane manufacturing wastes. The Microtox® bioassay was used to determine the toxicity of soils (modified Basic Solid Phase Test), soil elutriates (Basic Test), and organic extracts (adapted Organic Solvent Sample Solubilization Test), in which hydrophobic organic compounds are soluble. The acute toxicity of these persistent contaminants (hexachlorocyclohexanes, HCH isomers, as particulate matter in topsoil, and COCs, from dense non-aqueous phase liquid, DNAPL, in subsoil) and the commercial compounds were also measured. Soils tested showed different contaminant levels (topsoil: 0.9-1149 mg/kg and subsoil: 20-9528 mg/kg). Soil contaminants distribution, concentration and acute toxicity were highly related to the contamination source (HCHs or DNAPL). Soils, organic extracts, and subsoil elutriates presented high toxicity, highlighting the need for remediation of these sites. EC50 was calculated in the three-test applied for the soils tested. EC50 vs. COCs concentration in soils and soil elutriates showed an asymptotic trend, explained by the low pollutants solubility in the aqueous phase. Contrarily, EC50 vs. soil COCs concentration was more linear in the case of the organic extracts. This test was the most reliable from statistical analysis. The three methods reveal interesting and complementary information and are necessary for a complete overview of the acute toxicity of contaminated soils.

Theoretical Exploitation of 1,2,3,4,5,6-Hexachloro- and 1,2,3,4,5,6-Hexafluorocyclohexane Isomers as Biologically Active Compounds.

Hexachlorocyclohexanes (HCHs) have been widely explored as biological compounds during the last century. However, most of them were banned due to their potential toxicity in humans, animals, and the environment. Revisiting HCHs to explore their biological activity while improving key features is valuable and may lead to a new class of pesticides that utilizes the biological response of HCHs without their toxic characteristics. In this sense, the fluorine atom can be a possible alternative since a large number of therapeutics and agrochemicals have been developed with this halogen in their structure. We have evaluated herein the conformational behavior of HCHs and their bioisosteric fluorinated compounds, namely, hexafluorocyclohexanes (HFHs), through quantum-chemical calculations. We also explored the potential of the HCH and HFH isomers as biological compounds by docking them inside three possible targets. It was demonstrated that HCH and HFH have similar ligand-protein interactions with three pockets: the picrotoxin and barbiturate sites of the GABAA receptor and the ryanodine receptor. The results support HFHs as possible alternatives for HCHs since the replacement of Cl with F does not forfeit the main ligand-protein interactions. Finally, we demonstrated that HFHs have a lower log P than HCHs by almost two logarithmic units. This result highlights the role of fluorine in distribution and bioaccumulation.