The DBP exposome: Development of a new method to simultaneously quantify priority disinfection by-products and comprehensively identify unknowns.

Disinfected drinking water contains hundreds of disinfection by-products (DBPs) that are formed by the reaction of disinfectants with natural and anthropogenic organic matter, bromide, and iodide. Understanding what these DBPs are is important because millions of people worldwide consume drinking water every day, and human epidemiologic studies have reported cancer, miscarriage, and birth defects from consuming such waters. While more than 600 DBPs are reported in the literature, very few studies quantify complete classes of chlorinated, brominated, and iodinated DBPs. Also, very few studies conduct comprehensive non-target analyses of unknown DBPs to characterize the complete DBP exposure (the exposome). We developed a new gas chromatography (GC)-mass spectrometry (MS) method that simultaneously quantifies 39 priority unregulated DBPs from six different chemical classes (haloacetaldehydes, haloketones, haloacetamides, haloacetonitriles, halonitromethanes, and iodinated-trihalomethanes) and analyzes unknown DBPs with mass accuracy <600 ppm under full-scan conditions. Using a new type of time-of-flight (TOF) mass spectrometer, which combines selected ion monitoring (SIM)-level sensitivity with mass accuracy of ±0.05 Da, method detection limits of 3-61 ng/L were achieved. These levels were found to be quite comparable to those of a widely used single quadrupole mass spectrometer (2-90 ng/L) operated in SIM mode. However, analysis using this TOF mass spectrometer offers two additional advantages over traditional quadrupole-MS: (1) full-scan data, which provides additional confidence for target analytes, as well as complete mass spectra for unknown analysis, and (2) two decimal place mass accuracy, which allows additional confidence for target analytes and importantly, molecular formula indication for unknowns. High resolution accurate mass TOF was also used to validate identification of selected compounds. This new method was demonstrated on finished drinking waters from three different drinking water plants, where target quantification and non-target unknown analyses were performed simultaneously during the same run. This enabled the quantification of 39 DBPs, along with the non-target identification of many other drinking water contaminants, including two additional non-target DBPs: N,N-dimethylacetamide and N-nitrosodibutylamine.

Evaluation of multiple alternative instrument platforms for targeted and non-targeted dioxin and furan analysis.

The use of gas chromatography coupled to high-resolution magnetic sector mass spectrometers (GC-HRMS) is well established for dioxin and furan analysis. However, the use of gas chromatography coupled to triple quadrupole (MS/MS) and time of flight (TOF) mass spectrometers with atmospheric pressure ionization (API) and traditional electron ionization (EI) for dioxin and furan analysis is emerging as a viable alternative to GC-HRMS screening. These instruments offer greater versatility in the lab for a wider range of compound identification and quantification as well as improved ease of operation. The instruments utilized in this study included 2 API-MS/MS, 1 traditional EI-MS/MS, an API-quadrupole time of flight mass spectrometer (API-QTOF), and a EI-high-resolution TOF (EI-HRTOF). This study compared these 5 instruments to a GC-HRMS using method detection limit (MDLs) samples for dioxin and furan analysis. Each instrument demonstrated acceptable MDL values for the 17 chlorinated dioxin and furans studied. The API-MS/MS instruments provide the greatest overall improvement in MDL value over the GC-HRMS with a 1.5 to 2-fold improvement. The API-QTOF and EI-TOF demonstrate slight increases in MDL value as compared with the GC-HRMS with a 1.5-fold increase. The 5 instruments studied all demonstrate acceptable MDL values with no MDL for a single congener greater than 5 times that for the GC-HRMS. All 5 instruments offer a viable alternative to GC-HRMS for the analysis of dioxins and furans and should be considered when developing new validated methodologies.

Dioxin-like contaminants are no longer a risk to the American eel (Anguilla rostrata) in Lake Ontario.

The embryotoxicity of extracts of American eels (Anguilla rostrata) was measured to determine whether maternally derived contaminants contribute to the declining recruitment of eels to Lake Ontario. Sexually maturing, large yellow and silver eels were sampled in 2007 and 2008 from 5 locations in eastern Canada, including Lake Ontario; positive controls included eels from the Hudson River, United States, and Canal Dessel-Schoten, Belgium (European eel, Anguilla anguilla). Japanese medaka eggs were injected immediately after fertilization with 1 or 10 nL of eel extract and, after 12 d, scored for signs of toxicity. Eel extracts did not cause dioxin-like embryotoxicity, reflecting the low concentrations of total dioxin equivalents measured chemically in these same extracts. Embryo mortality and reduced hatching success at high doses of eel extracts may reflect the bioaccumulation of legacy or emerging chemicals of concern. The results were consistent with long-term trends of declining concentrations of persistent organic pollutants (POPs) in tissues of eels and other fish species from Lake Ontario, trends of declining embryotoxicity of eel tissue extracts, and recent increases of recruitment of juvenile eels to Lake Ontario. If dioxin-like compounds contributed in the past to the decline of recruitment and abundance of American eels in Lake Ontario, these data suggest that recruitment should recover, following the same trends as the recovery of lake trout reproduction in Lake Ontario. Environ Toxicol Chem 2018;37:1061-1070. © 2017 SETAC.

Maternal transfer of dioxin-like compounds in artificially matured European eels.

Several eel species of the genus Anguilla are considered endangered due to a severe decline in recruitment. Up to now, the reasons for this threatening development are not fully understood. The eel's highly specialized biology can lead to explicitly high accumulation of globally distributed organic lipophilic contaminants during its continental life. Because of this and due the particular toxicological sensitivity of early life stages of oviparous organisms towards dioxin-like compounds, it is crucial to improve our understanding concerning toxicokinetics and maternal transfer of organic contaminants in eels. This study presents analytical data on maternal transfer of dioxin-like (dl) compounds in relevant tissue samples taken from artificially matured and non-matured European silver eels (Anguilla anguilla) from German inland waters using gas chromatography coupled with mass spectrometry (GC/MS) and high-resolution mass spectrometry (GC/HRMS). Detected concentrations revealed a lipid-driven transfer of targeted compounds from muscle-fat-reserves to gonads and eggs respectively, with no distinct preferences concerning the chlorination degree of targeted compounds. Dl-PCBs were shown to contribute the major share of toxicity equivalents found in analysed eel tissues. Maternal muscle tissue to egg concentration ratios in wet weight-based samples had a mean of 6.95 ± 1.49 in accordance with the differences in total lipid content in the respective body matrices. Dioxins and furans in analysed samples were (from a toxicological point of view) of less relevance. Furthermore it was shown that muscle concentrations in silver eels could be used in future assessments to make conservative predictions for expected egg concentrations in female eels.

Distinguishing the C3 vs SH4 Mass Split by Comprehensive Two-Dimensional Gas Chromatography-High Resolution Time-of-Flight Mass Spectrometry.

The C3 vs SH4 (0.0034 Da) mass split is considered to be one of the most critical mass splits in petroleomics and is relevant because of the regulatory requirements for sulfur in petroleum fractions. To date, there are two ways to resolve mass splits such as C3 vs SH4: (a) ultrahigh resolution Fourier transform mass spectrometry (FT-MS); (b) high-resolution chromatography such as comprehensive two-dimensional gas chromatography (GC×GC). High-resolution chromatography minimizes the mass spectral resolution required to distinguish these key chemical constituents and provides additional sample characterization via isomer separation. High resolution mass spectrometry enables unambiguous chemical formulas determination and structural elucidation. In this paper, we demonstrate the combination of high resolution GC×GC with high resolution time-of-flight mass spectrometry to distinguish the C3 vs SH4 mass split and other common mass splits in a crude oil sample.

Progressive Increase in Disinfection Byproducts and Mutagenicity from Source to Tap to Swimming Pool and Spa Water: Impact of Human Inputs.

Pools and spas are enjoyed throughout the world for exercise and relaxation. However, there are no previous studies on mutagenicity of disinfected spa (hot tub) waters or comprehensive identification of disinfection byproducts (DBPs) formed in spas. Using 28 water samples from seven sites, we report the first integrated mutagenicity and comprehensive analytical chemistry of spas treated with chlorine, bromine, or ozone, along with pools treated with these same disinfectants. Gas chromatography (GC) with high-resolution mass spectrometry, membrane-introduction mass spectrometry, and GC-electron capture detection were used to comprehensively identify and quantify DBPs and other contaminants. Mutagenicity was assessed by the Salmonella mutagenicity assay. More than 100 DBPs were identified, including a new class of DBPs, bromoimidazoles. Organic extracts of brominated pool/spa waters were 1.8× more mutagenic than chlorinated ones; spa waters were 1.7× more mutagenic than pools. Pool and spa samples were 2.4 and 4.1× more mutagenic, respectively, than corresponding tap waters. The concentration of the sum of 21 DBPs measured quantitatively increased from finished to tap to pool to spa; and mutagenic potency increased from finished/tap to pools to spas. Mutagenic potencies of samples from a chlorinated site correlated best with brominated haloacetic acid concentrations (Br-HAAs) (r = 0.98) and nitrogen-containing DBPs (N-DBPs) (r = 0.97) and the least with Br-trihalomethanes (r = 0.29) and Br-N-DBPs (r = 0.04). The mutagenic potencies of samples from a brominated site correlated best (r = 0.82) with the concentrations of the nine HAAs, Br-HAAs, and Br-DBPs. Human use increased significantly the DBP concentrations and mutagenic potencies for most pools and spas. These data provide evidence that human precursors can increase mutagenic potencies of pools and spas and that this increase is associated with increased DBP concentrations.

Temporal variations in embryotoxicity of Lake Ontario American eel (Anguilla rostrata) extracts to developing Fundulus heteroclitus.

The recruitment of American eel (Anguilla rostrata) juveniles to Lake Ontario (LO), Canada has declined significantly since the 1980s. To investigate the possible contribution of maternally-transferred persistent organic pollutants (POPs) to this decline, this study measured temporal variations in the toxicity of complex organic mixtures extracted from LO American eels captured in 1988, 1998 and 2008 to developing Fundulus heteroclitus exposed by intravitelline (IVi) injection. The 1988 and 1998 eel extracts were most toxic, causing a pattern of sublethal embryotoxic responses similar to those previously reported in F. heteroclitus embryos exposed to single dioxin-like compounds (DLCs): stunted growth, craniofacial deformities, EROD activity induction, and reduced predatory capacities. The potency of extracts declined over time; the only significant effect of the 2008 eel extracts was EROD induction. The chemically-derived TCDD-TEQs of eel extracts, calculated using measured concentrations of some DLCs and their relative potencies for F. heteroclitus, overestimated their potency to induce EROD activity possibly due to interactions among POPs. Other POPs measured in eel extracts (non-dioxin-like PCBs, PBDEs and organochlorinated pesticides) did not appear to be important agonistic contributors to the observed toxicity. The toxicity of the complex mixtures of POPs measured in LO eels may have been underestimated as a result of several factors, including the loss of POPs during extracts preparation and a focus only on short-term effects. Based on the model species examined, our results support the hypothesis that contamination of LO with DLCs may have represented a threat to the American eel population through ecologically-relevant effects such as altered larval prey capture ability. These results prioritize the need to assess early life stage (ELS) toxicity of DLCs in Anguilla species, to investigate long-term effects of complex eel extracts to ELS of fish, and to develop biomarkers for potential effects in eel ELS sampled in the field.

Trends of persistent organic pollutants in American eel (Anguilla rostrata) from eastern Lake Ontario, Canada, and their potential effects on recruitment.

This study reports the history of contamination of American eels (Anguilla rostrata) from eastern Lake Ontario (LO) by persistent organic pollutants (POPs). Three groups of 10 large female eels captured in eastern LO in each of 1988, 1998, and 2008 were analysed for polychlorinated dibenzo-p-dioxins and furans, polychlorinated biphenyls, several organochlorine pesticides, and polybrominated diphenyl ethers. Mean concentrations were up to 3-fold lower in 2008 compared to previous years. When combined with the results of previous studies, these data show that concentrations of POPs in American eels have declined exponentially since the early 1980s by an average of 9.1±1.9% per year. Toxic equivalent (TEQ) concentrations of dioxin-like compounds (DLCs) were calculated from fish toxic equivalency factors. Assuming an efficient transfer of DLCs to their eggs, egg TEQs prior to 2000 exceeded the threshold for chronic toxicity to embryos of European eels (Anguilla anguilla) and lake trout (Salvelinus namaycush) (4-5 pg/g ww of TEQ). These results suggest that embryotoxicity of maternally-derived DLCs from LO eels, historically a major contributor to the spawning stock of American eels, could have impaired the reproductive and recruitment success of the species.

Trophic magnification of chlorinated flame retardants and their dechlorinated analogs in a fresh water food web.

Chlorinated flame retardants, particularly dechlorane plus (DP), were widely used in commercial applications and are ubiquitous in the environment. A total of seven species of aquatic organisms were collected concurrently from the region of a chemical production facility in Huai'an, China. DP and structurally related compounds including mirex, dechloranes 602, 603, 604, chlordene plus (CP), DP monoadduct (DPMA), and two dechlorinated breakdown products of DP, decachloropentacyclooctadecadiene (anti-Cl(10)-DP) and undecachloropentacyclooctadecadiene (anti-Cl(11)-DP), were detected in these aquatic organisms. Nitrogen stable isotope ratios were also measured to determine the trophic levels of the organisms. Trophic magnification factors (TMFs) for these chemicals were calculated with values ranging from 1.0 to 3.1. TMFs for CP, mirex, anti-DP, and ∑DP were statistically greater than 1, showing evidence of biomagnification in the food web. Concentration ratios of anti-Cl(11)-DP to anti-DP showed a significant relationship with trophic level, implying that anti-Cl(11)-DP had a higher food-web magnification potential than its precursor. The biota-sediment accumulation factors and TMFs for DP demonstrated stereoselectivity, with syn-DP having a greater bioaccumulation potential than anti-DP in the aquatic environment.

Qualitative analysis of halogenated organic contaminants in American eel by gas chromatography/time-of-flight mass spectrometry.

Target compound analysis with scanning mass spectrometers such as quadrupole or magnetic sector instruments is used extensively in environmental chemistry because of the selectivity, sensitivity, and robustness. Yet, target compound analysis selectively ignores the majority of compounds present in a sample, especially in complex matrices like fish. In this study, time-of-flight mass spectrometry was used to screen for and identify halogenated compounds in American eels (Anguilla rostrata). Individual and then pooled eel samples were analysed using electron ionization and electron capture negative ionization (ECNI) modes. Eels were differentiated by principal component analysis of chemical profiles and were grouped corresponding to their capture location, all with a single instrument injection per sample. Bromine containing compounds were further investigated by taking advantage of the selectivity of ECNI by utilizing the Br(-) ion m/z 79 and 81. A total of 51 brominated compounds were detected and their identities were attempted by authentic standards, library searching, and/or chemical formula prediction based on accurate mass measurements. Several PBDEs were identified in the samples, and the majority of the non-PBDEs identified were bromophenols, bromoanisoles, and bromobenzenes. These classes of compounds are synthesized for use in flame retardant production either as intermediates or as final products. However, their occurrence in eels was most likely the result of metabolism or break-down products of high production volume flame retardants like polybrominated diphenyl ethers and bromophenoxy compounds.

Brominated flame retardants and Dechloranes in European and American eels from glass to silver life stages.

The populations of American (Anguilla rostrata) and European eels (Anguilla anguilla) have been declining rapidly in the last decades. Organic contaminants are suspected to be one of the possible causes for the decline; however, so far there have been few investigations of the uptake of specific compounds by different life cycle stages (e.g. freshwater or marine stage) and how the contamination patterns develop throughout the eel's life cycle. In the present study we measured concentrations of polybrominated diphenylethers (PBDEs), alternate brominated flame retardants (alternate BFRs) and Dechloranes (Decs) in different life stages of European and American eels to compare the contamination patterns and their development throughout the eel's life cycle. In general, concentrations of flame retardants (FRs) were similar to or higher in American than in European eels, and a greater number of FRs were detected. PBDE congeners that are characteristic of the Penta-PBDE formulation were the most abundant FRs in all adult eels as well as American glass eels. In European glass eels the alternate BFR 2,3-dibromopropyl-2,4,6-tribromophenylether (DPTE) and Dechlorane Plus were the dominating FRs, with average concentrations of 1.1±0.31 ng g(-1) ww and up to 0.32 ng g(-1) ww respectively. Of the PBDEs BDE-183 was the most abundant congener in European glass eels. Low concentrations (less than 10% of the total contamination) of Tetra and Penta-PBDEs in juvenile European eels indicated that bans of technical Penta-PBDE in the European Union are effective. Enrichment of PBDEs was observed over the life stages of both European and American eels. However, a greater relative contribution of PBDEs to the sum FR contamination in American eels indicated an on-going exposure to these substances. High contributions of alternate BFRs in juvenile eels indicated an increased use of these substances in recent years. Concentrations seemed to be driven primarily by location, rather than life stage or age.

Spatial trends of dioxin-like compounds in Atlantic anguillid eels.

Several temperate freshwater eel stocks have experienced unsustainable declines, yet to be explained. The decline of lake trout (Salvelinus namaycush) in Lake Ontario has been linked to aryl-hydrocarbon receptor agonists such as polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs), dioxin-like polychlorinated biphenyls (dl-PCBs), and polychlorinated naphthalenes (PCNs), and the question remains whether eels are affected similarly by these compounds. Concentrations of PCDD/Fs, dl-PCBs, and PCNs were determined in eels collected at seven locations in eastern Canada including L. Ontario, one location in New York, USA, and one location in Flanders, Belgium. Concentrations varied greatly among origins, indicating dissimilar historic loadings to local areas. The risk to eel reproduction was evaluated with 2,3,7,8-TCDD toxic equivalents, and increased by 10-fold from the least to most contaminated site. The risk to eel recruitment from dioxin-like compounds in American eel using available guidelines is low. The development of a more comprehensive model for eel recruitment risk assessment due to dioxin-like compounds, using eel-specific guidelines, is recommended. Toxic equivalents were 5-fold higher when based on mammalian toxic equivalency factors compared to fish values. About half of the eels captured in L. Ontario exceeded the Canadian guideline for fish consumption (20pg TEQ g(-1) ww), but there were no other exceedances in Canada. The current risk to eel consumers in Canada is low overall, except for highly urbanized and industrialized areas.

Dechlorane plus monoadducts in a Lake Ontario (Canada) food web and biotransformation by lake trout (Salvelinus namaycush) liver microsomes.

Compounds related to the high-production-volume flame retardant Dechlorane Plus (DP) were measured in a Lake Ontario food web located downstream of a DP manufacturing plant. These compounds, 1,3- and 1,5-DP-monoadducts (DPMA), are positional isomers and are thought to arise from the incomplete reaction of DP or impurities in the DP starting material during its manufacture. The 1,3-DPMA isomer was measured (0.12-199 ng g(-1) lipid wt) in all trophic levels, whereas 1,5-DPMA was measured only sporadically in the food web and was not detectable in the apex predator, lake trout (Salvelinus namaycush). Concentrations of DPMA isomers when detected in Lake Ontario biota were greater than that of total DP for all trophic levels. The prevalence of 1,3-DPMA in the food web, and especially in lake trout, may be due to obstruction of the existing carbon double bond to enzyme attack, rendering it less readily metabolized. To examine this hypothesis, biotransformation kinetic experiments using in vitro lake trout liver microsomal exposures were performed. Zero-order depletion rate constants for 1,3- and 1,5-DPMA were 92.2 and 134.6 pmole h(-1) , respectively, with corresponding half-lives of 2.03 ± 0.14 h (1,3-DPMA) and 1.39 ± 0.09 h (1,5-DPMA). Furthermore, the 1,5-isomer was depleted to a greater extent than 1,3-DPMA. Specific biotransformation products were not identified. These data support the hypothesis that 1,5-DPMA is more readily metabolized than 1,3-DPMA by lake trout. The present study also shows that the concentrations of these isomers, which the authors speculate might be unintended impurities or byproducts in some technical DP formulations, exceed that of the intended product in biota.

Human health risk assessment of occupational and residential exposures to dechlorane plus in the manufacturing facility area in China and comparison with e-waste recycling site.

A screening level human health risk assessment based on the worst-case scenario was conducted on the occupational and residential exposures to dechlorane plus (DP) in the manufacturing facility region and an electronic-waste (e-waste) recycling site in China, which are two of the most polluted areas of DP in the world. Total estimated exposure doses (EEDs) via dietary intake, dermal contact, and inhalation was approximately 0.01 mg kg(-1) d(-1) for people living in the manufacturing facility region. In comparison, total EEDs (approximate 0.03 µg kg(-1), d(-1)) were 300-fold lower in people living near an e-waste recycling site in China. Chronic oral, dermal, and inhalation reference doses (RfDs) were estimated to be 5.0, 2.0, and 0.01 mg kg(-1)d (-1), respectively. The oral RfD was markedly greater than Mirex (2×10(-4) mg kg(-1) d(-1)) and decabromodiphenyl ether (BDE-209; 7×10(-3) mg kg(-1) d(-1)), which have been or might be replaced by DP as a flame retardant with less toxicity. Monte Carlo simulation was used to generate the probability densities and functions for the hazard index which was calculated from the EEDs and RfDs to assess the human health risk. The hazard index was three orders of magnitude lower than 1, suggesting that occupational and residential exposures were relatively safe in the manufacturing facility region and e-waste recycling site.

Spatial trends of organochlorinated pesticides, polychlorinated biphenyls, and polybrominated diphenyl ethers in Atlantic Anguillid eels.

The bioaccumulation of lipophilic contaminants such as polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), and polybrominated diphenyl ethers (PBDEs) can result in a reduction in fitness and spawner quality in eels and may be a factor in Anguillid sp. population declines. Contaminant concentrations in eels have been studied extensively in Europe, but data for American eels are severely lacking. Concentrations of PCBs, OCPs, and PBDEs were determined in American eel from eastern Canada and New York, USA, along with European eel from Belgium. Principal component analysis revealed that eels captured in the St. Lawrence estuary were a mixture of upstream migrants from the St. Lawrence River watershed, and fish captured in local tributaries. Contaminant concentrations were dependent on origin, related to the local environment, and were lower than historic values. In Canada, concentrations of OCPs and PCBs in eel tissues were below the Canadian human consumption guidelines for contaminants in fish, indicating that the current risk to consumers is low. However, concentrations of PCBs, total DDT, and mirex in eels from L. Ontario and the upper St. Lawrence R. were above Great Lakes guidelines for the protection of piscivorous predators. Concentrations of penta-BDE homologs exceeded the Canadian guideline for environmental quality in over half of the eels in this study, but concentrations of the other homolog groups were below the guideline.

Review of recent advances in research on the toxicity, detection, occurrence and fate of cyclic volatile methyl siloxanes in the environment.

The fate and behavior of cyclic volatile methylsiloxanes (cVMS) octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) in the environment were reviewed. We evaluated their usage data and patterns, physico-chemical properties, toxicology, partitioning and degradation, methods of detection, and concentrations. The use of cVMS as an intermediate in the formation of silicone polymers, personal care and household products has resulted in their widespread environmental exposure; they have been detected in biogas, air, water, soil, biosolid, sediment, and biota samples. Modeled and experimental results suggest that cVMS may be subject to long-range atmospheric transport, but have low potential to contaminate the Arctic. For D4 and D5, there was no evidence of trophic biomagnification in aquatic food webs, while some aquatic organisms demonstrated a high degree of bioconcentration and bioaccumulation. High concentrations of cVMS observed in indoor air and biosolids resulted from point sources. Concentrations of cVMS in water, sediment, and soil were all below their no-observed-effect-concentrations.

Analysis of synthetic canine training aids by comprehensive two-dimensional gas chromatography-time of flight mass spectrometry.

Cadaver dogs are trained on a variety of materials, including artificial or pseudo scents. The chemical components of commercially available pseudo scents are not known, so their accuracy as a decomposition odour mimic and their effectiveness as a canine training aid have not been evaluated. Two pseudo scents that are commercially available and used for training cadaver dogs were analysed using comprehensive two-dimensional gas chromatography-time of flight mass spectrometry (GC×GC-TOFMS). The two formulations were determined to be simplistic in their composition, compared to real cadaveric volatile organic compound (VOC) mixtures, with only a few major components. The enhanced GC×GC-TOFMS peak capacity was nevertheless useful to discriminate less intense peaks from large overloaded peaks. The availability of both dimension retention times combined with the peak finding and deconvolution algorithm, enabled the chemical characterization of the two formulations. Additionally, high resolution (HR) TOFMS was used to extract molecular formulae and confirm identities of analytes. The seven compounds identified by this work have not been reported previously as volatile products of decomposition, indicating that these pseudo scents are not to be considered as an accurate representation of cadaveric decomposition odour. Further research on the olfaction of scent detection canines and the chemical composition of their target odourants needs to be conducted to develop improved canine training aids.

Fugacity approach to evaluate the sediment-water diffusion of polycyclic aromatic hydrocarbons.

Diffusion is an important process for sediment-water exchange and plays a vital role in controlling water quality. Fugacity fraction (ff) was used to estimate the sediment-water diffusion of polycyclic aromatic hydrocarbons (PAHs) between seawater and surficial sediment. A total of 33 surface sediment and sea water samples were collected concurrently from the northeast coastal area in China and 25 PAHs were analyzed including the alkylated and chlorated PAHs. Fugacity fraction was calculated based on the PAH concentrations in water and sediment, octanol-water partition coefficient of PAHs, organic matter content in sediment, and density of sediment. The calculated results showed that ff increased with decreasing molecular weight of PAHs. The low molecular weight PAHs (2-3 rings) transferred from sediment to water and the sediment acted as a secondary source to the water. The medium molecular weight PAHs (4-5 rings) were close to the sediment-water equilibrium and the transfer tendency shifted between sediment and water. The high molecular weight PAHs (5-6 rings) transferred from water into sediment and the sediment acted as a sink. Soot carbon and the difference of PAH concentrations between sediment and water were found to be important factors affecting the sediment-water diffusion. This study provided new insight into the process of sediment-water diffusion, which has a great influence on the quality of water, especially in severely-polluted sediment areas.

Spatial and seasonal variations in atrazine and metolachlor surface water concentrations in Ontario (Canada) using ELISA.

Concerns regarding the impacts of pesticides on aquatic species and drinking water sources have increased demands on water quality monitoring programs; however the costs of sample analysis can be prohibitive. In this study we investigated enzyme-linked immunosorbent assay (ELISA) as a cost-effective, high through-put method for measuring pesticide concentrations in surface waters. Seven hundred and thirty-nine samples from 158 locations throughout Ontario were analysed for atrazine and metolachlor from April to October 2007. Concentrations ranged from <0.1 to 3.91 µg L(-1) (median=0.12 µg L(-1)) for atrazine and from <0.1 to 1.83 µg L(-1) (median=0.09 µg L(-1)) for metolachlor. Peak concentrations occurred in late spring/early summer, in rural agricultural locations, and decreased over the remainder of the growing season for both herbicides. About 3% of the samples that had ELISA results occurring above the limit of quantification (0.10 µg L(-1)) were evaluated against gas chromatography-mass spectrometry (GC-MS). Linear regression analysis revealed a R(2) value of 0.88 and 0.39, for atrazine and metolachlor, respectively. ELISA tended to overestimate concentrations for atrazine and metolachlor, most likely because the ELISA kits also detect their metabolites. Atrazine data suggest that ELISA may be used complementary with GC-MS analysis to enhance the spatial and temporal resolution of a water quality monitoring study. The commercially available metolachlor ELISA kit requires further investigation. ELISA may be used to detect atrazine and metolachlor in surface water samples, but it is not recommended as a quantitative replacement for traditional analytical methods.

Low cost monitoring of glyphosate in surface waters using the ELISA method: an evaluation.

Concerns have been raised in the scientific community regarding the environmental implications of a dramatic increase in corn-based ethanol production and associated increases in pesticide use. The use of glyphosate, a broad-spectrum herbicide, for corn production has increased considerably in recent years in Canada and the United States. The cost of measuring concentrations of organic contaminants in the environment using traditional wet chemistry methods can be prohibitive; especiallywhen large numbers of samples are required to quantify the spatial and temporal variability in contaminant concentrations. The goal of our study was to evaluate a cost-effective method to measure glyphosate concentrations in surface waters. The reliability of enzyme-linked immunosorbent assay (ELISA) results was evaluated against liquid chromatography tandem mass spectrometry, and linear regression results for 30 water samples from urban watersheds revealed a strong relationship (R2 = 0.88). These results suggest that ELISA methods, used in conjunction with traditional methods, represent a cost-effective approach to enhance the spatial and temporal resolution of a water quality monitoring study. Additionally, we measured a total of 739 surface water samples from over 150 sampling locations throughout Ontario using ELISA from April to October 2007. Concentrations exceeded the method detection limit of 0.1 microg/L in 33% of the samples, with a maximum concentration of 12.0 microg/L. Glyphosate showed a bimodal temporal distribution with peak concentrations occurring in late spring/early summer and fall, and did not exceed the Canadian Council of Ministers of the Environment (CCME) guideline for the protection of aquatic life (65 microg/L) in any of the samples.