Semi-volatile Organochlorine Compounds Research Articles

Analysis of hepatic deiodinase 2 mRNA levels in natural fish lake populations exposed to different levels of putative thyroid disrupters

Hepatic mRNA levels of the dio2 gene (deiodinase 2), implicated in thyroid hormone homeostasis, were analyzed in trout from six remote lakes in the Pyrenees (Spain) and the Tatra Mountains (Slovakia). Highest levels corresponded to fish from the two coldest lakes in Pyrenees, whereas relatively low levels were found in the Tatra lakes. These values correlated with the presence of highly-brominated polybrominated diphenyl ethers (PBDE) congeners in the muscle of the same animals, reflecting the distribution of these compounds across European mountain ranges. In contrast, cyp1a expression levels, diagnostic for the presence of dioxin-like pollutants, mirrored the distribution of semi-volatile organochlorine compounds, indicating the specificity of the two types of biological responses. Exposure to PDBEs is known to increase transcription of dio2 and other thyroid-related genes in laboratory experiments; we propose that our data reflects the same phenomenon in natural populations, driven by anthropogenic pollutants at the environmental concentrations.

Determination of semi-volatile organochlorine compounds in the atmosphere of Singapore using accelerated solvent extraction

Accelerated solvent extraction (ASE) has been applied to the quantitative extraction of organochlorine compounds (OCs), including organochlorine pesticides (HCHs, DDXs) and polychlorinated biphenyls (PCBs) present in both atmospheric particulate and gaseous phase. Extraction parameters such as the combination of solvents, extraction temperature, and static extraction time were investigated and optimized. Effective extraction can be carried out using a 3:1 mixture of n-hexane and acetone as extraction solvents at 100°C in 20min for all the compounds studied. The entire analytical procedure developed in this study proves to be reliable as evident from the analysis of specific surrogate standards with the mean recoveries per sample being greater than 82%. The optimized method was validated using NIST-certified SRM 1649a. Semi-volatile OCs, in the atmosphere of Singapore were quantified using the optimized ASE method together with GC–MS. Total average concentrations of ΣHCHs, ΣDDXs, and ΣPCBs in air samples were 244.9±88.5pgm−3, 7.7±4.1pgm−3, and 34.1±19.7pgm−3, respectively. The distribution of these compounds between the gas and particulate phase is discussed. Possible sources of atmospheric OCs are evaluated based on the molecular ratio of specific compounds and backward air trajectory analysis.

Organochlorine compounds in soils and sediments of the mountain Andean Lakes

Semi-volatile organochlorine compounds (OC) were analyzed in remote Andean soils and lake sediments. The sampling sites covered a wide latitudinal gradient from 18°S to 46°S along Chile and an altitudinal gradient (10–4500 m). The concentrations were in the order of background levels, involving absence of major pollution sources in the high mountain areas. Significant correlations were found between log-transformed concentrations of hexachlorobenzene, α- and γ-hexachlorocyclohexane in soils and total organic content (TOC). In addition, TOC-normalized concentrations of the most volatile OC showed a significant linear dependence with air temperature. This good agreement points to temperature as a significant factor for the retention of long range transported OC in remote ecosystems such as the Andean mountains, although other variables should not be totally excluded. The highest concentrations of OCs were achieved in the sites located at highest altitude and lowest temperature of the dataset.

Atmospheric semivolatile organochlorine compounds in European high-mountain areas (central Pyrenees and high Tatras).

Atmospheric samples from two European high-mountain areas showed similar composition of semivolatile organochlorine compounds (SOC), such as polychlorobiphenyls (PCBs), DDTs, endosulfans, hexachlorobenzene (HCB), and hexachlorocyclohexanes (HCHs). Nearly all compounds were predominantly found in the gas phase and only the less volatile such as some PCBs (e.g., 149, 118, 153, 138, and 180) were found in higher abundance in the particulate phase. HCB, 49-85 pg m(-3), is the dominant SOC. This compound is only found in the gas phase exhibiting uniform concentrations irrespective of season and air mass origin. SOC of present use, like HCHs and endosulfans, were found in higher concentrations in the warm periods, 32-46 and 4-10 pg m(-3) in the gas + particulate phases, respectively, reflecting their seasonal pattern of use in many European countries. PCB and 4,4'-DDE, 39-42 and 4-6 pg m(-3) in the gas + particulate phases, respectively, also showed a seasonal trend despite neither the former nor the precursor of the latter (4,4'-DDT) being manufactured with their use drastically restricted since the 1980s. The seasonal differences are mainly due to a higher occurrence of air masses with strong continental inputs in the warm than in the cold periods. In this respect, samples whose air masses traveled at the high troposphere (backward air mass trajectories >6000 m) have been observed to carry considerably smaller PCB and 4,4'-DDE loads (9.3 +/- 2.8 and 0.4 +/- 0.05 pg m(-3), respectively) than overall average.

Concentrations of organochlorine pesticides and polychlorinated biphenyls in amphipods (Gammarus lacustris) along an elevation gradient in mountain lakes of western Canada.

Populations of the amphipod Gammarus lacustris were examined for their concentrations of organochlorine pesticides and polychlorinated biphenyls (PCBs) from seven lakes spanning a 1,300-m elevation gradient in Alberta, Canada. The concentrations of several of the semivolatile organochlorine compounds ([SVOCs], vapor pressure > 0.03 Pa at 20 degrees C) increased at higher altitudes. This pattern was generally not observed among the less volatile organochlorines ([LVOCs]. vapor pressure < 0.03 Pa at 20 degrees C). These same SVOC compounds have been previously shown to increase at high latitudes as a result of their long-range transport and preferential deposition in cold climates. We also show that populations of G. lacustris at high elevations have slower growth rates and store more lipids than populations at lower elevations. To resolve the colinearity of independent variables, we used multiple regression to identify patterns of contaminant concentrations in this data set. Multiple regressions showed that the effect of elevation, lipid content, and temperature on contaminant concentrations was no longer significant once the growth rate of Gammarus was included as an independent variable. This study shows that enrichment of SVOCs occurs in Gammarus at high altitudes in Alberta, Canada, and that growth rate (biodilution) appears to be the primary influence. Because Gammarus is an important trophic link in aquatic foodwebs in these environments, enhanced concentrations of toxicants in prey may increase their biomagnification in top predators of high-altitude lakes.

Semivolatile organochlorine compounds in the free troposphere of the Northeastern Atlantic.

Polychlorobiphenyls (PCBs), hexachlorobenzene (HCB), hexachlorocyclohexanes, and DOTs were analyzed over 1 entire year period in the air of a high altitude remote site (2367 m above sea level) located in Teide (Tenerife, Canary Islands, 28 degrees N16 degrees W) in the Eastern North Atlantic region. Twenty samples were collected providing information on the concentrations of these semivolatile organochlorine compounds (SOCs) in the free troposphere since the stable and persistenttemperature inversion in the subtropics defines a clear separation from the marine boundary layer. More than 80% of total SOCs were in the gas phase. HCB was the individual SOC in higher concentration, 51 pg m(-3), well above than the other SOCs identified, 1-11 pg m(-3). Sum PCB concentrations were 78 pg m(-3). These concentrations range among the lowest described in atmospheric samples. The collected air originated from four main sectors, high and middle latitudes in the north Atlantic, Europe, and Africa, as determined from isentropic backward air mass trajectories. No significant differences were observed for the concentrations of these compounds between air masses showing a high uniform SOC composition of the free troposphere. Only the more volatile PCB congeners, #18 and #28, exhibited significant differences between air masses from northern and southern latitudes. A seasonal temperature dependence for the less volatile PCB congeners, five or more chlorine subtituents, was also observed. Free tropospheric concentrations of all SOCs except HCB were lower than those measured near sea level for reference. PCB concentrations at the two altitudes exhibited consistent differences according to degree of chlorination. The stronger decrease of the more volatile compounds with altitude might reflect higher photodegradation.

Stable chlorine and carbon isotopic compositions of selected semi-volatile organochlorine compounds

To assess whether the isotopic composition of semi-volatile organochlorine compounds (SVOCs) may be a useful tool, we measured the bulk δ 37Cl and δ 13C values of several pesticides and Aroclor mixtures from different suppliers. Overall, the δ 37Cl and δ 13C values ranged from −5.10 to +1.22‰ and −31.63 to −22.39‰, respectively. These values are narrower than the ranges observed previously for volatile organic contaminants (VOCs). In particular, the isotopic compositions of the Aroclor mixtures were very tightly constrained for both chlorine and carbon. We also observed that SVOCs synthesized from hexachlorocyclopentadiene had the most enriched δ 37Cl values. These data provide a baseline for future work employing isotope ratios to study the environmental fate of SVOCs.

Fluxes of semivolatile organochlorine compounds in Bow Lake, a high‐altitude, glacier‐fed, subalpine lake in the Canadian Rocky Mountains

The fluxes of several organochlorine compounds (OCs) to and from a high‐altitude lake were calculated to determine the relative contributions of rainfall, snowfall, runoff, gas absorption and volatilization, sedimentation, and outflow. Runoff inputs, particularly from a glaciated catchment, and gas absorption were major sources of many OCs. Losses by volatilization, outflow, and sedimentation were also important transport pathways for most OCs. We observed a net deposition of hexachlorocyclohexanes (HCHs) and DDT to Bow Lake by gas exchange, whereas hexachlorobenzene, chlordanes, and most polychlorinated biphenyls were seen to volatilize to the air. The insecticide lindane (γHCH), widely applied across Canada as a seed dressing in early spring, was absorbed by Bow Lake in early summer but gradually equilibrated with water as the summer progressed. This was the result of lower concentrations of γHCH in air and rising air temperatures in late summer. Results indicate that glacially derived tributary inputs are dominant sources of persistent organic pollutants to these glacier‐fed mountain lakes and that smaller contributions may derive from air‐water gas exchange. This study highlights the importance of glacial sources of OCs to mountain lakes and corroborates recent evidence of OC contamination in glacially derived aquatic systems.

Deposition of Semi-Volatile Organochlorine Compounds in the Free Troposphere of the Eastern North Atlantic Ocean

Deposition samples were taken at a height of 2367 m above sea level (m.a.s.l.) on the Island of Tenerife from May 1999 until July 2000 and analysed for 19 polychlorinated biphenyl (PCB) congeners, hexachlorobenzene (HCB), hexachlorocyclohexanes (HCH) and DDTs. This site is located above the inversion layer, so samples represent background concentrations of the free troposphere. The average deposition fluxes of HCB, total HCH, DDTs and PCBs were 86, 400, 110 and 780 ng m −2 yr −1 , respectively, being lower than those reported at sea level in continental or marine areas. All compounds are generally found in higher abundance in the wet precipitation samples. However, these samples only represent a fraction, e.g. 33%, of the total deposition load. Annual mass balance calculations show that wet precipitation is essentially responsible for the deposition of the low molecular weight OC whereas dry deposition accounts for more than 50% of the higher molecular weight PCBs.

Accumulation of persistent organochlorine compounds in mountains of western Canada

Persistent, semi-volatile organochlorine compounds, including toxic industrial pollutants and agricultural pesticides, are found everywhere on Earth, including in pristine polar and near-polar locations1,2,3,4. Higher than expected occurrences of these compounds in remote regions are the result of long-range transport in the atmosphere, precipitation and ‘cold condensation’ — the progressive volatilization in relatively warm locations and subsequent condensation in cooler environments3,4 which leads to enhanced concentrations at high latitudes. The upper reaches of high mountains are similar to high-latitude regions in that they too are characterized by relatively low average temperatures, but the accumulation of organochlorine compounds as a function of altitude has not yet been documented. Here we repororganochlorine deposition in snow from mountain ranges in western Canada that show a 10- to 100-fold increase between 770 and 3,100 m altitude. In the case of less-volatile compounds, the observed increase by a factor of 10 is simply due to a 10-fold increase in snowfall over the altitude range of the sampling sites. In the case of the more-volatile organochlorines, cold-condensation effects further enhance the concentration of these compounds with increasing altitude. These findings demonstrate that temperate-zone mountain regions, which tend to receive high levels of precipitation while being close to pollutant sources, are particularly susceptible to the accumulation of semivolatile organochlorine compounds.

Volatile and semi-volatile organochlorine compounds in tap and riverine waters in the area of influence of a chlorinated organic solvent factory

The study of volatile and semi-volatile organochlorinated compounds, VOC and SVOC, respectively, in the river and tap water of an area under the influence of a chlorinated organic solvent factory has shown that the industrial activities are reflected in the composition of the river waters, namely by the presence of chloroform, carbon tetrachloride, trichloroethylene, tetrachloroethylene, penta and hexachlorobenzene and octachlorostyrene as major pollutants, but that the tap waters are free from products which can be related to this origin. However, the potable water contains significant concentrations of species derived from chlorination, namely chloroform, bromodichloromethane, dibromochloromethane and bromoform, as well as pesticides of wide use in agriculture, α- and γ-hexachlorocyclohexane. The VOC and SVOC compositions in these tap waters are very similar to that found in the waters of Barcelona, a reference urban area which is not under the influence of large organochlorine solvent factories.

Observations on long-term air-soil exchange of organic contaminants

Evidence for long-term changes in the soil composition of selected organic compounds, brought about by exchanges with the atmosphere, is briefly reviewed. In the case of some compounds - such as benzo(a)pyrene and octachlorodibenzo-p-dioxin, soils may be significant long-term environmental sinks for atmospherically-derived material. In other cases - such as phenanthrene and some of the lighter PCBs, de-gassing or volatilisation from soil back to the air can occur under certain conditions. Hence the soil may act as a "short-term" sink, and a potential source to atmosphere. Indeed, for some 'semi-volatile' compounds used in large quantities in the past - such as PCBs, soil outgassing may actually be an extremely important source to contemporary air. Furthermore, soil outgassing from areas of former high use may provide an important driving mechanism for continued "global cycling" of a range of semi-volatile organochlorine compounds.

Initial development of a solid-phase fugacity meter for semivolatile organic compounds

A method to determine the fugacity of semivolatile organochlorine compounds on solid surfaces is presented. The method was developed and tested using spruce needles. Needle surface fugacities were determined indirectly, using the concentration of the compound in a gas phase which had been equilibrated with the needle surface. Measurements with both artificially contaminated and natural spruce needles showed good agreement between the fugacities on the needle surfaces and the air fugacities of the chosen compounds in the needles'habitat.

Studies of the global baseline pollution XIII

High-volume air sampling by adsorption on silica gel on the island Reunion (21°S, 56°E) in the southern Indian Ocean was done for analyzing typical southern hemisphere air for semivolatile organohalogens such as α-hexachlorocyclohexane (13) and g-hexachlorocyclohexane (406), hexachlorobenzene (7), polychlorobiphenyls [PCB 28 (3.2); PCB 52 (4.9) PCB 101 (6.0); PCB 138 (5.0); PCB 153 (5.0); PCB 180 (1.5)], 4,4′-DDT (8), 4,4′-DDE (19), cis- (4) and trans-chlordane (9), trans-nonachlor (3) and heptachloroepoxide (6) in the lower troposphere. The values in parenthesis are mean concentrations in picogram per m3 air. Local input and long range transport could be distinguished in most cases. The 2,4-, 2,6-, 2,4,5-, 2,4,6-, the tetra- and pentachloro-congeners of the chloroanisoles (phenylmethyl-ethers) were detected. 2,3,5,6-Tetrachloro-1,4-dimethoxy-benzene was found in the 100–280 pg/m3 range, while 2,4,6-tribromoanisol was detected in the 8–30 pg/m3 range together with traces of 2,4- and 2,6-dibromoanisole. The sources and the fate of the latter compounds are not yet understood, since both anthropogenic emissions and biogenic origin are possible. The ratios of the concentrations in the southern and northern hemisphere (south/north ratio) of the semivolatile organochlorine compounds are discussed. The south/north ratio ranges from 0.05 to 0.09 for HCB and α-HCH, respectively, to 0.74 for the PCBs and 0.9 for g-HCH, to 3 for 4,4′-DDE and up to 8 for 4,4′-DDT. This indicates that there is no significant interhemispheric exchange for compounds such as HCB and α-HCH in the atmosphere, and as a consequence the same must be true for other semivolatile compounds.

Rapid Gas Chromatographic Method for the Determination of Volatile and Semivolatile Organochlorine Compounds in Soil and Chemical Waste Disposal Site Samples

Rapid Gas Chromatographic Method for the Determination of Volatile and Semivolatile Organochlorine Compounds in Soil and Chemical Waste Disposal Site Samples