Multimedia modeling of the fate of triclosan and triclocarban in the Dongjiang River Basin, South China and comparison with field data.

Triclosan (TCS) and triclocarban (TCC) are two active ingredients widely used in many home and personal care products. Multimedia fate of TCS and TCC in the Dongjiang River basin, South China were addressed by the developed level III fugacity model based on their usage. Under the assumption of steady state, the concentrations in air, water, soil, sediment, suspended particulate matter (SPM) and fish as well as transfer flux across the interface between the compartments were simulated. The measured concentrations for the two compounds in water, SPM, and sediment from field monitoring campaigns were then compared to validate the model. The results showed that the model predicted reasonably accurate concentrations and the differences between the measured and modeled concentrations were all less than 0.7 log units. TCS and TCC had a tendency to distribute into the sediment phase, which accounted for more than 66.3% and 90.3% of the total masses, respectively. Wastewater discharge was the main source for the occurrence of the two compounds in the aquatic environment, while degradation was the primary process for the loss in the study area, followed by the advection export. Sensitivity analysis showed that the most influential parameters for the fate of the target chemicals were source term, degradation rates and adsorption coefficients. Monte Carlo simulation could well describe the modeling uncertainty and variability.

Hexachlorocyclohexane and dichlorodiphenyltrichloroethane residues in the dustfall of Tianjin, China.

Heating and nonheating season dustfall samples were collected from 23 sites in Tianjin, China during 2002-2003 to determine residues of hexachlorocyclohexane isomers (a-HCH, beta-HCH, gamma-HCH, and beta-HCH) and dichlorodiphenyltrichloroethane and metabolites (p,p'-DDE, p,p'-DDD, and p,p'-DDT). Concentrations of sumHCH (sum of alpha-, beta-, gamma-, and delta-HCH) and sumDDT (sum of p,p'-DDE, p,p'-DDD, and p,p'-DDT) varied in ranges of 10.9-3.16 x 10(3) and 37.9-1.53 x 10(3) ng g(-1) dry weight in heating season and in ranges of 6.9-1.12 x 10(3) and 18.6-626 ng g(-1) dry weight in nonheating season, respectively. It was found that HCHs and DDTs concentrations of the most heating season samples were higher than those of nonheating season samples collected from the same sites. Among studied compounds of the HCH family, beta-HCH prevailed in most samples, suggesting a possible volatilization or resuspension from contaminated topsoil. As for DDTs, p,p'-DDT and p,p'-DDE prevailed in most samples, indicating a possible "fresh" input. Correlations between HCHs/DDTs and total organic carbon and particle size are discussed. Atmospheric deposition fluxes were calculated for the heating and nonheating seasons, and the results showed that the annual input of particulate sumHCH and sumDDT from air to surface in the studied area of 1.19 x 10(4) km2 were 89 t and 80 t, respectively.

[Population exposure to HCH in Tianjin area].

The population exposure to HCH in Tianjin area is estimated based on field data on media concentration and other data from the literature. A multimedia /multipathway human exposure model is employed to calculate the population' s Chronic Daily Intake (CDI) of HCH. The population's lifetime CDI was 0.05microg x (kg x d)-1, and the daily exposures of child, youth and adult were 0.10, 0.06, and 0.04microg x (kg x d)-1, respectively. The result indicates that diet exposure was the most important route, accounting for 87% of total dose. Respiration ranked second and contributed 5% - 10% of the total dose.

[PAHs in airborne particles from Tianjin in winter season].

Total suspended particles (TSP) samples from 13 stations in Tianjin were collected and analyzed for polycyclic aromatic hydrocarbons (PAHs) during 2002 winter. There was significant difference in total PAH concentration among 13 samples. TSP samples from the east Economic Development Area and mid-north districts had the highest contents of PAHs, while Dagang Oil Field had the lowest PAH content. The urban area, south district, and Jixian county had the moderate contents of PAHs. Based on the measured concentration of the PAHs, BaP equivalent (BaPeq) were derived based on Toxicity Equivalent Factors (TEFs) of the PAHs. The total BaPeq values were similar among the samples. The contribution of PAHs with five or six rings contributed 90% of the total toxicity, while they accounted for only 50% of the total concentration.

System-level responses of lake ecosystems to chemical stresses using exergy and structural exergy as ecological indicators.

This paper presents the system-level responses of experimental lake ecosystems to three chemical stresses (acidification, copper and pesticide contamination) using exergy and structural exergy as ecological indicators. The results indicate that the doses or toxicity of the three chemical stressors contributed to changes in both exergy and structural exergy. Remarkable changes in exergy and structural exergy occurred under acidic conditions and in the presence of Dursban, 24D-DMA, permethrin, bifenthrin, Carbaryl, TCP, PCP, trichlorethylene, benzene, and high doses of Cu, oil, and hexazinone. This seemed to indicate that the subject ecosystems were seriously contaminated by these chemical stressors. For low doses of Cu, oil, atrazine, HCBP, and hexazinone, exergy and structural exergy were either unchanged or only slightly changed, suggesting that the lake ecosystems were not significantly impacted by these chemical stressors. Discussion of the relationships between ecosystem-level changes and structural and functional changes in stressed lake ecosystems indicates that the above-mentioned ecosystem-level changes were in accordance with the changes in structure and function. The observed changes in exergy and structural exergy were also consistent with Odum's predictions of shortened food chains, reduced resource use efficiency, poor stability, low information, and high entropy in stressed aquatic ecosystems. The findings lead the authors to conclude that it is feasible for exergy and structural exergy to serve as ecological indicators when characterizing the system-level responses of experimental lake ecosystems to chemical stress. These results for experimental lake ecosystems would be extrapolated to actual lakes.