Analysis Of Organic Contaminants Research Articles

Bioclogging in porous media: influence in reduction of hydraulic conductivity and organic contaminants during synthetic leachate permeation.

In this study the concept of biofilm accumulation in the sand column was promoted to assess the changes in hydraulic conductivity and concentration of organic contaminants of the synthetic leachate. Four different combinations of column study were carried out using synthetic leachate as a substrate solution. Mixed and stratified mode of experiments with two different sizes (0.3 mm and 0.6 mm) of sand grains were used for column filling. Two columns were acting as a blank, the remaining two columns amended with mixed microbial cultures which were isolated from leachate. The column was operated with continuous synthetic leachate supply for 45 days. The results indicated that the highest hydraulic conductivity reduction occurred in the mixed sand microbial column with 98.8% when compared to stratified sand microbial column. The analysis of organic contaminants of the effluent leachate was also clearly shown that the mixed sand amended with microbes poses a suitable remedial measure when compared to natural and synthetic liners for controlling the leachate migration in the subsurface environment.

Freeze drying reduces the extractability of organochlorine pesticides in fish muscle tissue by microwave-assisted method

Samples of animal origin are usually dried before solvent extraction for analysis of organic contaminants. The freeze drying technique is preferred for hydrophobic organic compounds in practice. In this study, it was shown that the concentration of organochlorine pesticides (OCPs) extracted from fish muscle tissue significantly decreased after the samples were freeze dried. And the reason for this reduced extractability seemed to be the resistance of OCPs associated with freeze-dried muscle protein to solvent extraction. The extractability can be recovered by adding water prior to extraction. It suggests that the dietary exposure risk of OCPs from fish might be underestimated if freeze-dried samples are used.

Isolation of estrogen receptor subtypes and vitellogenin genes: expression in female Chalcalburnus tarichi.

Reproductively arrested gonadal development has been previously described in the teleost pearl mullet (Chalcalburnus tarichi, Cyprinidae) from Van Edremit Gulf of Lake Van, Turkey. Oocyte development in some females was arrested at the previtellogenic stage, while gonadosomatic index (GSI) and plasma 17β-estradiol (E2) level were low. A subset of the females was found to have normal ovaries and relatively higher plasma E2 and GSI. These two groups were termed reproductively arrested (RA) and reproductively non-arrested (RN) females. In this study, we cloned estrogen receptor (ER) isoforms (ERα, ERβ1 and ERβ2) and vitellogenin (Vtg), and their mRNA levels were measured in RA and RN fish tissues. C. tarichi ERs fell in the same clade with other fish ERs and ERα and ERβ1 had 97% and 98% identity with the roach (Rutilus rutilus) ERs, respectively. Both Vtg and ER isoforms' mRNA abundance were higher in the liver than in the ovary and hypothalamus (liver>ovary>hypothalamus). The level of ERα mRNA was significantly lower in the liver, ovary and brain of RA fish than in the RN fish tissues. ERβ1 mRNA levels were not different in the liver and ovary from RA and RN fish while ERβ2 expression significantly increased in the liver and ovary from RA fish. All ER subtype expression was found to be lower in the brain from RA fish than RN fish. The level of Vtg mRNA was significantly lower in the liver and ovary from RA fish than RN fish tissue. These results suggest that ER subtypes are differentially regulated by E2, and their functions are also different in vitellogenesis. Analysis of organic contaminants in sediments revealed that C. tarichi living in Van Edremit Gulf of Lake Van are exposed to the contaminants bis(2-ethylhexyl) phthalate and 4,4(') DDT. We suggest that the RA fish represent a segment of the population that is more sensitive to exposure to endocrine disrupting compounds.

Analysis of Organic and Inorganic Contaminants in Dried Sewage Sludge and By-Products of Dried Sewage Sludge Gasification

Organic and inorganic contaminants in sewage sludge may cause their presence also in the by-products formed during gasification processes. Thus, this paper presents multidirectional chemical instrumental activation analyses of dried sewage sludge as well as both solid (ash, char coal) and liquid (tar) by-products formed during sewage gasification in a fixed bed reactor which was carried out to assess the extent of that phenomenon. Significant differences were observed in the type of contaminants present in the solid and liquid by-products from the dried sewage sludge gasification. Except for heavy metals, the characteristics of the contaminants in the by-products, irrespective of their form (solid and liquid), were different from those initially determined in the sewage sludge. It has been found that gasification promotes the migration of certain valuable inorganic compounds from sewage sludge into solid by-products which might be recovered. On the other hand, the liquid by-products resulting from sewage sludge gasification require a separate process for their treatment or disposal due to their considerable loading with toxic and hazardous organic compounds (phenols and their derivatives).

Magnetically mixed hemimicelles solid-phase extraction based on ionic liquid-coated Fe3O4 nanoparticles for the analysis of trace organic contaminants in water

Magnetically mixed hemimicelles formed by ionic liquid-coated Fe3O4 magnetic nanoparticles (IL-coated Fe3O4 NPs) as an adsorbent of solid-phase extraction are proposed for the preconcentration of five organic contaminants.

A purge and trap integrated microGC platform for chemical identification in aqueous samples.

The majority of current micro-scale gas chromatography (μGC) systems focus on air sampling to detect volatile organic compounds (VOCs). However, purging the VOCs from a water sample using microsystems is an unchartered territory. Various organic compounds used in everyday life find their way to water bodies. Some of these water organic compounds (WOCs) persist or degrade slowly, threatening not just human existence but also aquatic life. This article reports the first micro-purge extractor (μPE) chip and its integration with a micro-scale gas chromatography (μGC) system for the extraction and analysis of water organic compounds (WOCs) from aqueous samples. The 2 cm × 3 cm μPE chip contains two inlet and outlet ports and an etched cavity sealed with a Pyrex cover. The aqueous sample is introduced from the top inlet port while a pure inert gas is supplied from the side inlet to purge WOCs from the μPE chip. The outlets are assigned for draining water from the chip and for directing purged WOCs to the micro-thermal preconcentrator (μTPC). The trapped compounds are desorbed from the μTPC by resistive heating using the on-chip heater and temperature sensor, are separated by a 2 m long, 80 μm wide, and 250 μm deep polydimethylsiloxane (OV-1) coated μGC separation column, and are identified using a micro-thermal conductivity detector (μTCD) monolithically integrated with the column. Our experiments indicate that the combined system is capable of providing rapid chromatographic separation (<1.5 min) for quaternary WOCs namely toluene, tetrachloroethylene (PCE), chlorobenzene and ethylbenzene with a minimum detection concentration of 500 parts-per-billion (ppb) in aqueous samples. The proposed method is a promising development towards the future realization of a miniaturized system for sensitive, on-site and real-time field analysis of organic contaminants in water.

Evaluating the efficiency of advanced wastewater treatment: Target analysis of organic contaminants and (geno-)toxicity assessment tell a different story

At a pilot scale wastewater treatment plant ozonation and powdered activated carbon filtration were assessed for their efficacy to remove trace organic contaminants from secondary treated effluents. A chemical analysis of 16 organic compounds was accompanied by a comprehensive suite of in vitro and in vivo bioassays with the focus on genotoxicity to account for the potential formation of reactive oxidation products. In vitro experiments were performed with solid phase extracted water samples, in vivo experiments with native wastewater in a flow through test system on site at the treatment plant. The chemical evaluation revealed an efficient oxidation of about half of the selected compounds by more than 90% at an ozone dose of 0.7 g/g DOC. A lower oxidizing efficiency was observed for the iodinated X-ray contrast media (49–55%). Activated carbon treatment (20 mg/L) was less effective for the removal of most pharmaceuticals monitored. The umuC assay on genotoxicity delivered results with about 90% decrease of the effects by ozonation and slightly lower efficiency for PAC treatment. However, the Ames test on mutagenicity with the strain YG7108 revealed a consistent and ozone-dose dependent increase of mutagenicity after wastewater ozonation compared to secondary treatment. Sand filtration as post treatment step reduced the ozone induced mutagenicity only partly. Also the fish early life stage toxicity test revealed an increase in mortality after ozonation and a reduced effect after sand filtration. Only activated carbon treatment reduced the fish mortality compared to conventional treatment on control level. Likewise the in vivo genotoxicity detected with the comet assay using fish erythrocytes confirmed an increased (geno-)toxicity after ozonation, an effect decrease after sand-filtration and no toxic effects after activated carbon treatment.This study demonstrates the need for a cautious selection of methods for the evaluation of advanced (oxidative) treatment technologies and of the effectiveness of post-treatments for elimination of adverse effects caused by oxidative treatments case by case.

Online microchannel preconcentrator for carbofuran detection

A simple and rapid online microchannel preconcentrator coupled with an amperometric detection for the analysis of carbofuran using polyethylene glycol coated onto magnetic particle (PEG-magnetic particles) sorbents was developed. This simple-to-prepare microchannel preconcentrator used an external magnet to retain the PEG-magnetic particle sorbents inside the microchannel. Under optimum conditions, the system provided two linear ranges, from 0.01 to 10.0 mg L−1 and from 10.0 to 130.0 mg L−1 with a limit of detection of 8.7 ± 0.1 μg L−1. The microchannel preconcentrator provided very good stability; it can be used for up to 326 consecutive injections of 5.0 mg L−1 carbofuran with a relative standard deviation of less than 3%. The developed system provided a good microchannel-to-microchannel and a good electrode-to-electrode reproducibility (n = 6, %RSD < 1). It also provided an excellent selectivity when it was tested with two other carbamate pesticides, carbaryl and methomyl, with a 43 and 256 times higher detection sensitivity for carbofuran, respectively. The developed system was successfully applied to detect carbofuran in surface water samples obtained near vegetable plantation areas. The concentrations of carbofuran in these samples were found to be in the range of non-detectable to 0.047 ± 0.001 mg L−1. The developed system is easy to operate and easy to couple with other analytical instruments and it could be easily adapted for the analysis of other polar organic contaminants.

Ultra high performance liquid chromatography tandem mass spectrometry for rapid analysis of trace organic contaminants in water

BackgroundThe widespread utilization of organic compounds in modern society and their dispersion through wastewater have resulted in extensive contamination of source and drinking waters. The vast majority of these compounds are not regulated in wastewater outfalls or in drinking water while trace amounts of certain compounds can impact aquatic wildlife. Hence it is prudent to monitor these contaminants in water sources until sufficient toxicological data relevant to humans becomes available. A method was developed for the analysis of 36 trace organic contaminants (TOrCs) including pharmaceuticals, pesticides, steroid hormones (androgens, progestins, and glucocorticoids), personal care products and polyfluorinated compounds (PFCs) using a single solid phase extraction (SPE) technique with ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS). The method was applied to a variety of water matrices to demonstrate method performance and reliability.ResultsUHPLC-MS/MS in both positive and negative electrospray ionization (ESI) modes was employed to achieve optimum sensitivity while reducing sample analysis time (<20 min) compared with previously published methods. The detection limits for most compounds was lower than 1.0 picogram on the column while reporting limits in water ranged from 0.1 to 15 ng/L based on the extraction of a 1 L sample and concentration to 1 mL. Recoveries in ultrapure water for most compounds were between 90-110%, while recoveries in surface water and wastewater were in the range of 39-121% and 38-141% respectively. The analytical method was successfully applied to analyze samples across several different water matrices including wastewater, groundwater, surface water and drinking water at different stages of the treatment. Among several compounds detected in wastewater, sucralose and TCPP showed the highest concentrations.ConclusionThe proposed method is sensitive, rapid and robust; hence it can be used to analyze a large variety of trace organic compounds in different water matrixes.

Analysis of polar organic contaminants in surface water of the northern Adriatic Sea by solid-phase extraction followed by ultrahigh-pressure liquid chromatography–QTRAP® MS using a hybrid triple-quadrupole linear ion trap instrument

Water-soluble polar organic contaminants are discharged by rivers, cities, and ships into the oceans. Little is known on the fate, pollution effects, and thresholds of toxic chemical mixtures in the marine environment. A new trace analytical method was developed for the multi-compound analysis of polar organic chemical contaminants in marine waters. The method is based on automated solid-phase extraction (SPE) of one-liter water samples followed by ultrahigh-pressure liquid chromatography triple-quadrupole linear ion-trap mass spectrometry (UHPLC-QTRAP(®) MS). Marine water samples from the open Adriatic Sea taken 16km offshore from Venice (Italy) were analyzed. Method limits of quantification (LOQs) in the low picogram per liter (pg/l) concentration range were achieved. Among the 67 target chemicals analyzed, 45 substances could be detected above the LOQ. The chemicals detected at the highest concentrations were caffeine (up to 367ng/l), nitrophenol (36ng/l), 2,4-dinitrophenol (34ng/l), 5-methyl-1H-benzotriazole (18.5ng/l), sucralose (11ng/l), 1H-benzotriazole (9.2ng/l), terbuthylazine (9ng/l), alachlor (7.7ng/l), atrazine-desisopropyl (6.6ng/l), diethyltoluamide (DEET) (5.0ng/l), terbuthylazine-desethyl (4.3ng/l), metolachlor (2.8ng/l), perfluorooctanoic acid (PFOA) (2.5ng/l), perfluoropentanoic acid (PFPeA) (2.3ng/l), linuron (2.3ng/l), perfluorohexanoic acid (PFHxA) (2.2ng/l), diuron (2.0ng/l), perfluorohexane sulfonate (PFHxS) (1.6ng/l), simazine (1.6ng/l), atrazine (1.5ng/l), and perfluorooctane sulfonate (PFOS) (1.3ng/l). Higher concentrations were detected during summer due to increased levels of tourist activity during this period.

Trace elements and organic contaminants in tissues of minke whale (Balaenoptera acutorotstrata) and its feed from Icelandic waters

In a research project by Iceland under the auspice of the Marine Research Institute Iceland in 2003-2007, 200 minke whales (Balaenoptera acutorostrata) were caught in Icelandic waters. Within this research effort of Iceland, a comprehensive research activites were devoted to analysis of trace elements and organic contaminants in both different tissues of the minke whale and its possible prey species as revealed by stomach content. The scientific questions asked by these studies were the following: 1. What are the characteristics of the Icelandic minke whale stock as regards environmental contaminants compared to other stocks of minke whale worldwide? 2. Can inorganic and organic contaminants provide answers regarding the prey species of the minke whales? 3. Is it possible to estimate the feed consumption of the minke whale by way of contaminants in its tissues and its prey species? 4. Do biopsies provide information on the level and behaviour of contaminants in the organs of the minke whale? 5. Are the levels of environmental contaminants in tissues of minke whales detrimental to the health of the animals? 6. Do the levels of contaminants restrict the human consumption of minke whale products? For this purpose the trace elements Hg, Cd, Zn, Cu, Pb, Se, As, Ni, Cr, and Mn were analysed in skin, muscle, liver, kidneys, ovaries and testes of 25 minke whales selected with respect to size, sex, and location around Iceland. PCBs, DDTs, HCB, HCHs, toxaphenes, chlordanes, dieldrin and PBDEs were analysed in blubber (biopsy and cross section), muscle, and liver while dioxins and dioxinlike PCBs were analysed in the ventral grooves of five animals. All these contaminants were also analysed in 50 samples of probable prey species: whole animals of cod, haddock, pollock, herring, capelin, sandeel, and krill. The results are described and discussed with respect to the scientific objectives above with due consideration of the biological factors that may affect the levels, e.g. age, sex, nutritional status and trophic level (δ15N and δ13C).

Current challenges in compound-specific stable isotope analysis of environmental organic contaminants

Compound-specific stable-isotope analysis (CSIA) has greatly facilitated assessment of sources and transformation processes of organic pollutants. Multielement isotope analysis is one of the most promising applications of CSIA because it even enables distinction of different transformation pathways. This review introduces the essential features of continuous-flow isotope-ratio mass spectrometry (IRMS) and highlights current challenges in environmental analysis as exemplified for the isotopes of nitrogen, hydrogen, chlorine, and oxygen. Strategies and recent advances to enable isotopic measurements of polar contaminants, for example pesticides or pharmaceuticals, are discussed with special emphasis on possible solutions for analysis of low concentrations of contaminants in environmental matrices. Finally, we discuss different levels of calibration and referencing and point out the urgent need for compound-specific isotope standards for gas chromatography-isotope-ratio mass spectrometry (GC-IRMS) of organic pollutants.

Natural dissolved organic matter affects electrospray ionization during analysis of emerging contaminants by mass spectrometry

Dissolved organic matter (DOM), present in many forms in water, can interfere with analysis of organic contaminants by atmospheric pressure ionization–mass spectrometry. A quantitative analysis of this interference, or matrix effect, on organic contaminant target analyte measurements was carried out using un-fractionated and fractionated dissolved natural organic matter from the Suwannee River, GA (SROM), a standard reference material, that was directly infused into the tandem mass spectrometer during multiple reaction monitoring (MRM) of a suite of endocrine disrupting compounds–pharmaceuticals and personal care products (EDC/PPCPs). Most target analytes suffered signal suppression in the presence of both fractionated and un-fractionated SROM, however greater interferences were measured with fractionated relative to bulk SROM. This finding is consistent with the view of organic matter as a supramolecular association of low molecular mass components having separate charged and structural features revealed only after dissociation.

Characterization of organic chemical contaminants in sediments from Jobos Bay, Puerto Rico

Jobos Bay, located on the southeastern coast of Puerto Rico, contains a variety of habitats including mangroves, seagrass meadows, and coral reefs. The watershed surrounding the bay includes a number of towns, agricultural areas, and the Jobos Bay National Estuarine Research Reserve (NERR). Jobos Bay and the surrounding watershed are part of a Conservation Effects Assessment Project (CEAP), involving the Jobos Bay NERR, the US Department of Agriculture, and the National Oceanic and Atmospheric Administration (NOAA) to assess the benefits of agricultural best management practices (BMPs) on the terrestrial and marine environments. As part of the Jobos Bay CEAP, NOAA collected sediment samples in May 2008 to characterize over 130 organic chemical contaminants. This paper presents the results of the organic contaminant analysis. The organic contaminants detected in the sediments included polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls, and the pesticide DDT. PAHs at one site in the inner bay near a boat yard were significantly elevated; however, all organic contaminant classes measured were below NOAA sediment quality guidelines that would have indicated that impacts were likely. The results of this work provide an important baseline assessment of the marine environment that will assist in understanding the benefits of implementing BMPs on water quality in Jobos Bay.

EPA 525.2 for the Analysis of Organic Contaminants in Drinking Water, Groundwater, and Raw Source Water in any Treatment Phase

EPA 525.2 for the Analysis of Organic Contaminants in Drinking Water, Groundwater, and Raw Source Water in any Treatment Phase

Chlorine Isotope Analysis of Organic Contaminants Using GC–qMS: Method Optimization and Comparison of Different Evaluation Schemes

Compound-specific online chlorine isotope analysis of chlorinated hydrocarbons was evaluated and validated using gas chromatography coupled to a regular quadrupole mass spectrometer (GC-qMS). This technique avoids tedious off-line sample pretreatments, but requires mathematical data analysis to derive chlorine isotope ratios from mass spectra. We compared existing evaluation schemes to calculate chlorine isotope ratios with those that we modified or newly proposed. We also tested systematically important experimental procedures such as external vs. internal referencing schemes, and instrumental settings including split ratio, ionization energy, and dwell times. To this end, headspace samples of tetrachloroethene (PCE), trichloroethene (TCE), and cis-dichloroethene (cDCE) at aqueous concentrations in the range of 20-500 μg/L (amount on-column range: 3.2-115 pmol) were analyzed using GC-qMS. The results (³⁷Cl/³⁵Cl ratios) showed satisfying to good precisions with relative standard deviations (n = 5) between 0.4‰ and 2.1‰. However, we found that the achievable precision considerably varies depending on the applied data evaluation scheme, the instrumental settings, and the analyte. A systematic evaluation of these factors allowed us to optimize the GC-qMS technique to determine chlorine isotope ratios of chlorinated organic contaminants.

Tandem MS for environmental and food analysis

This special issue contains selected papers presented at the sixth annual LC/MS/MS Workshop on Environmental Applications and Food Safety. Focus on Emerging Substances held on 25–26 February 2010 in Barcelona, Spain. Following the success of the previous five annual workshops on liquid chromatography–tandem mass spectrometry (LC-MS/MS) for screening and trace-level quantitation in environmental and food samples (Barcelona, June 2005; Barcelona, September 2006; Guelph, April 2007; Barcelona, February 2008; Toronto, April 2009), this sixth workshop was jointly organized by CSIC—Consejo Superior de Investigaciones Cientificas (Barcelona, Spain), Waters Corporation (Manchester, UK), Environment Canada and the Institut d'Estudis Catalans (Barcelona, Spain) in collaboration with the Spanish Society for Mass Spectrometry (SEEM) and the Catalan Institute for Water Studies (ICRA). In the course of the workshop, 25 keynote lectures and 37 poster presentations were presented. The principal topics were practical aspects of the usefulness of tandem massspectrometric techniques for screening and quantitation of organic contaminants in the environmental and food samples. This year, the focus was on the analysis of emerging substances, such as nanoparticles, siloxanes, perfluorinated compounds, pharmaceuticals, drugs of abuse and polar pesticides. Over the last 20 years, liquid chromatography–mass spectrometry techniques have advanced dramatically in their sensitivity, specificity and reliability. Detection of sub-parts per trillion concentrations is becoming routine for many organic analytes and methods achieving detection of a few hundred femtograms of some analytes have been reported. Such progress is mostly due to development of LC–MS/MS techniques, which are today the methods of choice for the determination of trace organic analytes in environmental and food samples. Swift growth in the use of LC-MS/MS for the analysis of organic contaminants in environmental and food matrices has been compelled by the need for high-quality data on their occurrence in such complex matrices at very low concentrations. At the workshop and in this special issue, some of the most recent trends in the LC-MS/MS analysis of emerging contaminants in environmental and food matrices were covered, such as:

High concentrations of persistent organic pollutants including PCBs, DDT, PBDEs and PFOS in little brown bats with white-nose syndrome in New York, USA

White-nose syndrome (WNS) is a condition associated with white fungal growth on ears, wings, and nose of hibernating bats; this condition has recently resulted in high bat mortality in the northeastern United States. Nevertheless, the pathogenesis of morbidity and mortality are still unknown. Elevated exposure to toxic contaminants could be a contributing factor via the consequent immunosuppression and endocrine disruption. In this study, diseased little brown bats ( Myotis lucifugus) were collected from several hibernacula in eastern New York State in 2008. Fat tissues of bats were analyzed for polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), polybrominated biphenyls (PBBs), and organochlorine pesticides (OCPs; DDT, chlordanes, HCB, and HCH), and liver was analyzed for perfluorinated compounds (PFCs). A reference population of little brown bats, not affected by WNS, was also collected from a cave in Kentucky for the analysis of trace organic contaminants. Concentration of PCBs in fat tissues of bats from New York ranged from 1900 ng g −1 to 35 000 ng g −1, lipid wt, with the highest concentrations found in bats collected from caves in Albany County. High concentrations of PCBs were also found in bats from Kentucky (17 100–18 400 ng g −1, lipid wt). Total PBDE concentrations in fat tissues ranged from 520 ng g −1 to 10 900 ng g −1, lipid wt, in bats from New York and from 4300 ng g −1 to 13 000 ng g −1, lipid wt, in bats from Kentucky. High concentrations of DDT (26 900 ng g −1, lipid wt), chlordanes (6350 ng g −1, lipid wt), and HCB (260 ng g −1, lipid wt) were found in bats from New York. Concentrations of hexabromobiphenyl congener 153 (PBB 153) in bats from New York ranged from 8.6 ng g −1 to 12 4000 ng g −1, lipid wt. Concentrations of PFCs were on the order of a few tens to a few hundreds of nanograms per gram liver, on a wet weight basis. Overall, high concentrations of PCBs, PBDEs, DDT, and chlordanes were found in fat tissues of diseased bats from New York, although the concentrations in bats from non-diseased, reference population, from Kentucky were also high.

Screening analysis of volatile organic contaminants in commercial inorganic coagulants used for drinking water treatment

A method for quality screening is suggested to detect volatile impurities in inorganic coagulants that are used for drinking water treatment. Static headspace gas chromatography with mass spectrometry detection (HS–GCMS) is sensitive and selective to detect volatiles in low concentrations. This study has discovered that volatile organic impurities are detectable in ferric and aluminium-based coagulants which are used for drinking water treatment. For ferric chloride, 2-propanol was detected at a level of 17–24 μg ml −1, acetone at 0.7–1.7 μg ml −1, 1,1,1-trichloroacetone at 0.02–0.04 μg ml −1, trichloromethane at 0.01–0.02 μg ml −1 and toluene at 0.01–0.12 μg ml −1. For ferric chloride sulfate, acetone was detected at a level of 0.12 μg ml −1, 1,1,1-trichloroacetone at 0.06–0.08 μg ml −1, trichloromethane at 0.13–0.23 μg ml −1, bromodichloromethane at 0.04–0.06 μg ml −1 and dibromochloromethane at 0.04–0.05 μg ml −1. For aluminium hydroxide chloride, only trichloromethane was detectable, but below the method detection limits (MDL). Although the concentrations of these impurities in commercial coagulants are low, this observation is important and should have impact on water industries for them to pay attention to the chemicals they are using for drinking water production.

Quantitative analysis of toxic halogenated contaminants in Oluyoro stream of Nigeria

Analysis of organic contaminants is reported for the Oluyoro stream located in the South-Western Nigeria. Using gas chromatography methods with flame ionization, electron capture and mass spectrometer detectors, alarming levels of organic pollutants including alkanes, alkenes, alcohols and alkyl halides were detected. Remarkably, toxic halogenated organic substances such as 4,4′-dichlorodiphenyltrichloroethane (4,4′-DDT), 4,4′-dichlorodiphenyldichloroethane (4,4′-DDD), beta-benzenehexachloride (beta-BHC), heptachlor epoxide, endrin aldehyde and endrin ketone are found to be at 15,820, 6,176, 1,155, 336, 24 and 13 times, respectively, more than the permitted levels of the United States Environmental Protection Agency (US-EPA). Furthermore, 4,4′-DDD, a probable human carcinogen, and methoxychlor are detected for the first time when compared to the last report published in 1992. Activities such as high influx of domestic and industrial wastes to the stream have drastically increased the concentrations of these halogenated contaminants. Results presented in this article provide important information for potential future effects of these contaminants on human health and the integrated environment in the region.