Microcosm studies on the air–soil exchange of hexachlorobenzene and polychlorinated biphenyls.

Soils have an important role to play in supplying and receiving contaminants from the atmosphere, and in the global cycling of certain persistent organic pollutants (POPs). A microcosm study was conducted, in which some aspects of air–soil exchange likely to be important for the global cycling of POPs were simulated. HCB and PCBs were introduced into a sealed chamber, which contained soils of varying organic matter content, and in which soil mixing was a variable. Uptake of these compounds on to the soils was monitored over time. Subsequently, the primary chemical source was removed and further changes in the residues retained on the soils were monitored. The rates of uptake onto the different soil treatments are compared and the influence of the soil organic matter content and mixing evaluated. The implications for the global cycling of POPs are discussed

Chiral organochlorine pesticide signatures in global background soils.

Chiral pesticides frequently undergo enantioselective degradation in soils. Prior studies to characterize chiral signatures have focused on treated agricultural soils, rather than background (untreated) soils, and tracking signatures in the atmosphere for source apportionment purposes. In this study, we investigated the chiral signatures in 65 background soils collected from different locations across the world. The soils were taken from different ecosystems (e.g., grasslands, forests), and the enantiomeric fractions (EFs) of chiral chlordanes, α-hexachlorocyclohexane (α-HCH), and o,p‘-DDT were determined. Chlordanes in most of the soils showed the usual pattern of enantioselective degradation seen in agricultural soils, depletion of (+)-trans-chlordane (TC) and (−)-cis-chlordane (CC). However, some samples showed opposite enantiomer degradation patterns for TC, CC, and chlordane compound MC5. Correlations were tested between the deviation of EFs from racemic (DEVrac = absolute value of 0.500 − EF), the percent soil organic matter (% SOM), annual mean temperature, and the ratio of TC to the more stable compound trans-nonachlor (TN). Significant positive correlations were found between DEVrac and % SOM for TC and CC (p = 0.0022 and 0.0031), but not for the other OCPs. No significant correlations were found between DEVrac and annual mean temperature for any of the OCPs. DEVrac for TC was negatively correlated with the TC/TN ratio, but the regression was driven by two points with high ratios of TC/CC. Removing these two points resulted in a nonsignificant regression. The range of EFs for TC, CC, and α-HCH in soils was greater than in ambient air, providing evidence of in situ degradation after atmospheric deposition in some cases. Variable EFs in soil suggest that caution is needed when considering the enantiomer signatures in air as a marker of volatilization of weathered soil-derived organochlorines

Fate of Brominated Flame Retardants and Organochlorine Pesticides in Urban Soil: Volatility and Degradation

As the uses of polybrominated diphenyl ethers (BDEs) are being phased out in many countries, soils could become a secondary emission source to the atmosphere. It is also anticipated that the demand for alternative brominated flame retardants (BFRs) will grow, but little is known about their environmental fate in soils. In this study, the volatility and degradation of BFRs and organochlorine pesticides (OCPs) in soil was investigated. A low organic carbon (5.6%) urban soil was spiked with a suite of BFRs and OCPs, followed by incubation under laboratory condition for 360 days. These included BDE- 17, -28, -47, -99; α- and β-1,2-dibromo-4-(1,2-dibromoethyl)­cyclohexane (TBECH), β-1,2,5,6-tetrabromocyclooctane (TBCO), and 2,3-dibromopropyl-2,4,6-tribromophenyl ether (DPTE), OCPs: α-hexachlorocyclohexane (α-HCH) and ¹³C₆-α-HCH, <i>trans</i>-chlordane (TC), and ¹³C₁₀-TC. The volatility of spiked chemicals was investigated using a fugacity meter to measure the soil-air partition coefficient (<i>K</i>_SA). <i>K</i>_SA of some spiked BFRs and OCPs increased from Day 10 to 60 or 90 and leveled off afterward. This suggests that the volatility of BFRs and OCPs decreases over time as the chemicals become more strongly bound to the soil. Degradation of alternative BFRs (α- and β-TBECH, β-TBCO, DPTE), BDE-17, and α-HCH (¹³C-labeled and nonlabeled) was evident in soils over 360 days, but no degradation was observed for the BDE-28, -47, -99, and TC (¹³C-labeled and nonlabeled). A method to separate the enantiomers of α-TBECH and β-TBCO was developed and their degradation, along with α-HCH (¹³C-labeled and nonlabeled) was enantioselective. This is the first study which reports the enantioselective degradation of chiral BFRs in soils. Discrepancies between the enantiomer fraction (EF) of chemicals extracted from the soil by dichloromethane (DCM) and air were found. It is suggested that DCM removes both the sequestered and loosely bound fractions of chemicals in soil, whereas air accesses only the loosely bound fraction, and these two pools are subject to different degrees of enantioselective degradation. This calls for caution when interpreting EFs obtained from DCM extraction of soil with EFs in ambient air

Organophosphate ester (OPEs) flame retardants and plasticizers in air and soil from a highly industrialized city in Turkey.

Passive air samples were collected at eight sites in Bursa, Turkey during five sampling periods between February–December 2014. Locations encompassed urban, suburban, industrial, rural and background environments. Soil samples (n = 8) were collected at each site during February 2014. Six OPEs were detected in samples: tris(2-chloroethyl) phosphate (TCEP), tris(chloropropyl) phosphate (TCPP), triphenyl phosphate (TPHP), tris(2-butoxyethyl) phosphate (TBOEP), tris(2-ethylhexyl) phosphate (TEHP), and tris(2-isopropylphenyl) phosphate (T2iPPP). Frequency of detection in air samples was TCPP and TPHP (100%) \u3e TBOEP (88%) \u3e TCEP (85%) \u3e TEHP (78%) \u3e T2iPPP (20%). Total OPEs in air per site by sampling period (excluding non-detects) ranged from 529 to 19,139 pg/m3. In soil, total OPEs ranged from 38 to 468 ng/g dw. In air, alkylated OPEs dominated followed by halogenated and aryl OPEs. In air, annual mean concentrations were TBOEP \u3e TCPP \u3e TPHP \u3e T2iPPP \u3e TEHP \u3e TCEP. In soils, alkylated OPEs were dominant at six sites and chlorinated OPEs at two sites. A comparison of OPE profiles between air and soil suggests that soils may be partly a source of OPEs to air. Mean concentrations in air were not directly proportional to temperature, and there were differences between alkylated compared to halogenated and aryl OPEs. In air, total and alkylated OPEs levels were fairly uniform, whereas more variability was found for the halogenated and aryl compounds. The relative contribution to total OPEs decreases for alkylated OPEs and increases for halogenated OPEs in samples going from background to suburban to urban and industrial sites. Levels of individual OPEs were all positively correlated between air and soils. In air, correlations between individual compounds were weak to moderate and were only statistically significant for TBOEP and TPHP. In soils, correlations were generally stronger and statistically significant only for TPHP and T2iPPP

Bioaccumulation and biomagnification of potential toxic elements (PTEs): An Avicennia germinans–Uca rapax trophic transfer story from Jobos Bay, Puerto Rico

In southern Puerto Rico along the coastline bordering the Jobos Bay National Estuarine Research Reserve, environmental encroachment has exposed mangrove forest to different sources of pollution. Potentially toxic element concentrations from the F1Tess (exchangeable), F4Tess (oxidizable), mangrove leaf litter (MLL), and fiddler crab whole body soft tissue were analyzed to assess the fate and transport of pollutants from the environment and its transition into flora-fauna via trophic transfer. Geo-accumulation factor values suggest the bay has experienced limited to no pollution when combining the concentrations of potentially toxic elements extracted from the F1Tess and F4Tess sediment fractions. These geochemical sedimentary compartments are considered “bioavailable” to flora-fauna as evidenced by the bioaccumulated Cd-Ba-V-Cu-Zn-As-Se in the leaf litter of the black mangrove Avicennia germinans and in the fiddler crab Uca rapax. The biota-sediment accumulation factor (F1Tess + F4Tess) demonstrated that Uca rapax behave like a de-concentrator for most pollutants and as a macro-concentrator for Cu-As, while the bioconcentration factors identified only Cu-As-Se as being actively bioaccumulated in the fiddler crabs. Of all the potentially toxic elements studied, As is the only one to be biomagnified via sediment-Avicennia germinans leaf litter-Uca rapax food chain. An unexpected find of this study was that the excavated sediment “pellets” by Uca rapax contained up to 4x the concentrations of Cd-Ba-V-Cr-Co-Ni-Cu-Zn-As-Se when compared to the F1Tess sediment fraction from the surface, thus suggesting a variable redox boundary within the fiddler crab\u27s burrow. © 202

Relationships between organic matter, black carbon and persistent organic pollutants in European background soils : implications for sources and environmental fate.

Black carbon (BC) and total organic carbon (TOC) contents of UK and Norwegian background soils were determined and their relationships with persistent organic pollutants (HCB, PAHs, PCBs, co-planar PCBs, PBDEs and PCDD/Fs) investigated by correlation and regression analyses, to assess their roles in influencing compound partitioning/retention in soils. The 52 soils used were high in TOC (range 54–460 mg/g (mean 256)), while BC only constituted 0.24–1.8% (0.88%) of the TOC. TOC was strongly correlated (p < 0.001) with HCB, PCBs, co-PCBs and PBDEs, but less so with PCDD/Fs (p < 0.05) and PAHs. TOC explained variability in soil content, as follows: HCB, 80%; PCBs, 44%; co-PCBs, 40%; PBDEs, 27%. BC also gave statistically significant correlations with PBDEs (p < 0.001), co-PCBs (p < 0.01) and PCBs, HCB, PCDD/F (p < 0.05); TOC and BC were correlated with each other (p < 0.01). Inferences are made about possible combustion-derived sources, atmospheric transport and air–surface exchange processes for these compounds. Total organic carbon and black carbon fractions can play an important role in the storage and cycling of persistent organic pollutants in background soils

Contamination of Soil by Obsolete Pesticide Stockpiles: A Case Study of Derince Province, Turkey

The areal distributions of the soil organochlorine pesticide (OCP) levels were investigated at adjacent and surrounding sites of the obsolete pesticide stockpile warehouse in Kocaeli, Turkiye. OCP levels in soil at neighboring sampling locations (positioned at 0.4 to 3 km from the stockpile) varied from 0.4 to 9 mu g/kg and 4.2 to 2226 mu g/kg (dry weight) for sigma HCHs and sigma DDXs, respectively. Levels at adjacent locations (positioned within 20 m from the stockpile) were considerably higher, varying from 74 to 39,619 mu g/kg and 1592 to 30,419 mu g/kg for sigma HCHs and sigma DDXs, respectively. Levels of OCPs dropped abruptly with the horizontal distance from the stockpile and had different transect profiles. The enantiomer fractions (EFs) near the stockpile range from 0.494 to 0.521, 0.454 to 0.515, and 0.483 to 0.533 for alpha-HCH, o,p '-DDT, and o,p '-DDD, respectively. These near-racemic EFs suggested that observed soil OCP levels were mainly influenced by recent emissions from the stockpile. A comparison of OCP compositions observed in the soil at the present study with the technical HCHs and DDTs revealed that the material in the stockpile primarily contains byproducts that were discarded during DDT and Lindane production at the adjacent plant instead of their technical mixtures