Behavior of PCNs, PCDDs, PCDFs, and dioxin-like PCBs in the thermal destruction of wastes containing PCNs

In the first known study to characterize the emissions of polychlorinated naphthalenes (PCNs), polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and dioxin-like polychlorinated biphenyls (dl-PCBs) from the thermal treatment of wastes containing PCNs, the formation and decomposition behavior of these pollutants was investigated both at laboratory scale and at plant scale. Exhaust gas measurements from laboratory-scale combustion of rubber belts containing PCNs (FB belts) were used as the basis for calculations predicting that the incremental dioxin toxic equivalency (TEQ) emissions from municipal solid waste (MSW) incinerators would be less than 0.1 ng/m3 N. In order to directly examine co-incineration of FB belts with MSW and to address potential differences between the laboratory experiment and full-scale MSW incinerators, experiments were conducted using a larger scale thermal treatment test facility with sampling and analysis at several points in the thermal treatment process. Congener specific analysis of PCNs clearly showed that both destruction and synthesis simultaneously occurred during combustion in the kiln. Most of the PCNs were destroyed by secondary combustion, and almost all PCNs were removed after flue gas treatment. Almost all PCDDs/DFs were synthesized as by-products of kiln combustion, most of them were destroyed by the secondary combustion, and almost all dioxins (PCDDs/DFs and dl-PCBs) were removed after flue gas treatment. The TEQ emission levels were less than 0.1 ng/m3 N for all plant-scale tests, and differences in TEQ emission levels were very small. Adding wastes containing PCNs to MSW will not influence thermal treatment emissions to the environment from modern solid waste incinerators.     

Short-term alleviation of aluminum phytotoxicity by urea application in acid soils from south China

A laboratory experiment was conducted to study effects of urea fertilizer on the chemical composition of soil solutions over time, and to determine Al toxicity as a function of rates of urea application. The experiment revealed that addition of urea fertilizer to soils caused drastic changes in soil pH during the hydrolysis and nitrification stages of urea transformation in the experiment. These pH changes, depending on the N rate of urea application and time courses, had variable effects on soil exchangeable Al, extracted with artificial solutions containing 1 mol l(-1) KCl. The Al mobilization rate could be resolved into two phases: A declining phase for Al was attributed to the urea-induced hydrolysis while a second rising phase was dependent with the nitrification of added N fertilizer. The decreases in exchangeable Al reached the greatest in 4-7 days after fertilization, consistent with soil pH increase. Decreased Al availability had been observed as a consequence of increasing urea addition and soil pH when using Root elongation of maize seedlings as the estimators. Results from the present study demonstrate that urea fertilizer to the surface of soils may lead to a temporary immobilization of Al and, therefore, alleviated Al toxicity to plant seedlings.     

Congener profiles of PCDDs, PCDFs, and dioxin-like PCBs in the breast milk samples in Tokyo, Japan

Exposure to dioxins has raised much public concern recently. We determined the congeners' distribution of polychlorinated-dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (dl-PCBs) in the breast milk samples collected in Tokyo, Japan. Breast milk was taken from 240 mothers, 30 days after delivery in 1999 and 2000 in Tokyo, Japan. The actual concentration and TEQ concentration of PCDDs (14 congeners), PCDFs (15 congeners), and dl-PCBs (12 congeners), and each congener's contribution to the total TEQ level were calculated. Among all the samples, PCDDs accounted for 34.8%, PCDFs accounted for 23.5%, dl-PCBs accounted for 41.7%, which was also similar in the breast milk from the primiparae and secundiparae. The main contributors to the total TEQ with increasing percentages were 2,3,4,7,8-PeCDF, 1,2,3,7,8-PeCDD and 3,3',4,4',5-PCB (#126), and they accounted for more than 65% of the total TEQ. Detailed congener analysis in breast milk samples is effective to understand dioxin sources.     

Sequential UV-biological degradation of chlorophenols

The sequential UV-biological degradation of a mixture of 4-chlorophenol (CP), 2,4-dichlorophenol (DCP), 2,4,6-trichlorophenol (TCP), and pentachlorophenol (PCP) was first tested with each pollutant supplied at an initial concentration of 50 mg l(-1). Under these conditions, the chlorophenols were photodegraded in the following order of removal rate: PCP>TCP>DCP>CP with only CP and DCP remaining after 40 h of irradiation. The remaining CP (41 mg l(-1)) and DCP (13 mg l(-1)) were then completely removed by biological treatment with an activated sludge mixed culture. Biodegradation did not occur in similar tests conducted with a non-irradiated mixture due to the high microbial toxicity of the solution. UV treatment lead to a significant reduction of the phytotoxicity to Lipedium sativum but no further reduction of phytotoxicity was observed after biological treatment. Evidence was found that the pollutants were partially photodegraded into toxic and non-biodegradable products. When the pollutants were tested individually (initial concentration of 50 mg l(-1)), PCP, TCP, DCP, 4-CP were photodegraded according to first order kinetic model (r2>99) with half-lives of 2.2, 3.3, 5.7, and 54 h, respectively. The photoproducts were subsequently biodegraded. This study illustrates the potential of UV as pre-treatment for biological treatment in order to remove toxicity and enhance the biodegradability of organic contaminants. However, it also shows that UV treatment must be carefully optimized to avoid the formation of toxic and/or recalcitrant photoproducts and results from studies conducted on single contaminants cannot be extrapolated to mixtures.     

Concentrations of decabromodiphenyl ether in air from Southern Ontario: implications for particle-bound transport

Atmospheric concentrations are reported for the main component of the brominated flame retardant decaBDE (BDE-209) in air samples collected from Southern Ontario for the period January 23-June 06, 2002. Levels ranged from below detection to 105pgm(-3) with virtually all of BDE-209 being trapped by the filter and thus deduced to be sorbed to aerosol particles. Thus, it is likely that the long-range atmospheric transport (LRAT) of BDE-209 is controlled by the transport characteristics of the aerosols. This conclusion that BDE-209 does not have the same potential for LRAT as other more volatile PBDEs is subject to possible complications arising from the uncertainties about the LRAT potential of aerosols.     

Germination and seedling growth of the water cress Rorippa sp. exposed to the chelant [S,S]-EDDS

With the implementation of the new EU environmental framework directives, high tier risk assessments of chemicals will be increasingly needed. For high production chemicals, additional tests will complement the standard battery for aquatic toxicity assessments (daphnids, algae, and fish). In the context of a new chemical notification at the European Union level, we have developed a seed germination and root elongation toxicity test with the freshwater aquatic plant Rorippa nasturtium-aquaticum (water cress) to confirm the low environmental risk of the chelant [S,S]-EDDS. A 14 day semi-static growth inhibition test was conducted with daily renewal of the test solution. No concentration related inhibition was found on the basis of any of the criteria investigated, i.e., time and extent of germination, biomass, number of leaves, stalk and root lengths. The no-observed effect concentration was considered to be >or=387 mg SS-EDDS/l. Although germination was selected as an appropriate endpoint to assess the effect of a chelant on an aquatic plant (other endpoints would have been dependant on essential metals that are chelated in standard culture tests), the absence of dose related effects requires further tests with higher exposure concentrations and/or other toxicant(s) to assess the validity of the test as a general tool for aquatic risk assessment.     

Application of an ELISA for PCB 118 to the screening of dioxin-like PCBs in retail fish

A commercially available enzyme-linked immunosorbent assay (ELISA) kit was evaluated for the determination of toxic equivalents (TEQs) of dioxin-like polychlorinated biphenyls (PCBs) in retail fish. The ELISA was highly specific for 2,3',4,4',5-pentachlorobiphenyl (PCB 118), which is generally the most abundant dioxin-like PCB isomer found in fish. The quantitative limit of the ELISA (using 3,3',4'-trichloro-4-methoxybiphenyl as a surrogate standard for PCB 118) was 10 ng ml(-1) (125 pg assay(-1)) in the standard curve, corresponding to 50 pg PCB 118 g(-1) in the tested sample. Good recoveries of PCB 118 (78.7-112.3%) were obtained for spiked purified fish extracts according to the ELISA. Good linearity was also obtained in dilution tests using purified fish extracts. No significant interference of the matrix was observed in the ELISA when this purification procedure was used. Recovery tests in which PCB 118 was added to fish samples also resulted in acceptable recoveries (60.2-82.3%) in the ELISA following purification. The ELISA results for fish samples correlated well with the TEQ concentrations of dioxin-like PCBs obtained by high-resolution gas chromatography/high-resolution mass spectrometry (r = 0.92, n = 26). These data indicate that the ELISA kit is suitable for screening retail fish for the TEQs of dioxin-like PCBs.     

Applying adult emergence as an endpoint in a post-exposure laboratory test using two midge species (Diptera: Chironomidae)

Several approaches have been used to evaluate biological impairment in aquatic ecosystems which can be categorized as either laboratory or field. In the recent years, the laboratory toxicity test approach has been extended to field exposures where ambient factors are allowed to influence the test response. Field exposures of laboratory test organisms require method modifications. In this paper, a novel in situ method is described which measures growth, survival and emergence of sediment inhabiting insects (Diptera: Chironomidae) that are used in standardized laboratory toxicity testing. Two standard chironomid species (Chironomus riparius and Chironomus tentans) were used to test the suitability of the approach and to compare the performance of the species. The larvae were transferred to the laboratory for emergence after 7 days in situ exposure which was compared to laboratory responses. Growth, survival and emergence were significantly lower in the in situ pre-exposure than in the laboratory. Also, emergence success was significantly lower in one reference sediment (LMR) than in the other test sediments in both in situ and the laboratory treatment. These lower response levels likely resulted from sediment characteristics and artifacts related to the exposure in the in situ chamber. Feeding and water quality within the exposure chamber appear to be factors that may differ markedly from the laboratory exposure and may affect organism responses. C. riparius developed (growth, emergence time) faster than C. tentans in all treatments, otherwise the species responded similarly. C. riparius may be a better alternative for the chronic in situ exposures because of shorter exposure times and reduced feeding requirements.     

Input and fate of anthropogenic estrogens and gadolinium in surface water and␣sewage plants in the hydrological basin of Prague (Czech Republic)

The concentration of the estrogens 17β-estradiol, estriol, estrone, 17α-ethinylestradiol, mestranol and norethisterone and of the anthropogenic gadolinium (Gd_ant) has been determined in the creeks and rivers, sewage treatment plants and water works of the city of Prague. The rapid degradation of estrogens in surface water allows the estrogen concentration gradient to be used as a very precise and sensitive guideline by which to pin-point sewage leaks into surface run-off water. The rather conservative behavior of Gd_ant in surface and ground water documents in the present case the presence of sewage water in the surface water cycle.     

Carbon budgets for catchments across a managed landscape mosaic in southeast Sweden: contributing to the safety assessment of a nuclear waste repository

Ecosystem budgets of matter contribute to the assessment of transport and accumulation of bioavailable contaminants in a landscape, since flows of matter and energy ultimately determine the rates at which contaminants will be partitioned in the environment. This study compares ecosystem properties, such as net primary production (NPP), sequestration of matter and fluxes to food sources for humans, which are of potential interest to describe fluxes and accumulation of bioavailable radionuclides in 14 catchments within a larger catchment area in southeast Sweden. The carbon budgets, used as a proxy for organic matter, are mainly based on local estimates of pools and fluxes, which have been distributed across a landscape mosaic of different vegetation types and management regimes using a geographical information system (GIS). NPP varied by a factor close to two (432 - 709 g x Cx m(-2)x y(-1)), while net ecosystem production ranged between -124 and 159 gx C x m(-2) x y (-1) for the different catchments. Carbon sequestration mainly occurred in the vegetation while the soil organic carbon pool was mainly a source of carbon. Large herbivores consumed on average 4.5 % of the above-ground green tissue production. When arable land was present in the catchment, the flux of carbon to humans was highest from crops and, in decreasing order, milk and beef, followed by the flux from hunting and berry/fungus picking. The results can be used to estimate the potential assimilation of radionuclides in vegetation and the potential exposure to humans of bioavailable radionuclides.