ABSTRACT
Sixteen surface sediment samples were collected from the estuary of the Suixi river to the mouth of Zhanjiang Bay and then analyzed for organochlorine pesticides (OCPs) by GC-MS to investigate their distribution and ecological risk. The results showed that the concentrations of OCPs in the sediments ranged from nd to 189.52 ng·g-1 (mean 32.17 ng·g-1), including HCHs (mean 5.81 ng·g-1) and DDTs (mean 26.90 ng·g-1). The distribution characteristics showed that the highest OCPs concentrations were found in the estuary and the main shipping lane areas, and the concentration in the nearshore area was higher than that offshore. Source analysis indicated that the HCHs mainly originated from agricultural applications, while no industrial input was observed. Some "hot-spots" areas occurred in harbors and shipping channels, likely as a result of the presence of paint flakes. Additionally, the concentrations of DDTs were found to be higher than the limits of Chinese Marine sediment quality criteria, and p,p'-DDT was the main type of DDT, presenting inevitable adverse biological effects and high ecological risk. Compared with other bays in China, the concentrations of OCPs in this study were in the upper-median pollution level, especially in harbors and boat maintenance facility areas. High OCPs inputs may occur, and thereby represent a certain ecological risk in Zhanjiang Bay.
ABSTRACT
The light absorption and fluorescence characteristics of atmospheric water-soluble organic compounds (WSOC) and humic-like substances (HULIS) during the winter season in Guangzhou were examined using UV-vis spectroscopy and excitation-emission matrix spectroscopy combined with parallel factor analysis (EEM-PARAFAC). The results showed that the SUVA254, HIX, and MAE365 values of HULIS were higher than those of WSOC, suggesting that the former had higher aromaticity, humification, and light-absorption capacity in winter atmospheric PM2.5 in Guangzhou. EEM-PARAFAC analysis identified three fluorescence components, including fulvic-like acid (C1), humic-like acid (C2), and protein-like (C3) components. The total humic-like components (C1+C2) accounted for 78% and 85% for WSOC and HULIS, respectively, which indicated that humic-like fluorescence components were the major components for both WSOC and HULIS and that HULIS were enriched with the dominant humic-like fluorophores. In addition, the aromaticity, humification, light-absorbing capacity, and C2 levels of WSOC and HULIS during the haze episode were significantly higher than those in the non-haze episode. This suggested that the water-soluble organics with higher molecular weights and stronger light-absorption capacities tended to form during the haze episode. The correlations analysis revealed strong negative correlations between C1 levels of WSOC and HULIS and HIX, MAE365, OCsec, K+, SO42-, and NH4+. Additionally, strong positive correlations were observed between C2 levels and the same factors. These results implied that the decrease in C1 and increase in C2 might lead to increased humification and light-absorption in WSOC and HULIS, and biomass burning and secondary organic aerosols might contribute to the C2 component.
ABSTRACT
Free and bound residues are the main form of organochlorine pesticides (OCPs) in soils/sediments. Four surface soil/sediments from the Pearl River Delta, China, were selected to characterize free and bound OCPs in different fractions of organic matters in the samples through alka-extraction, HCl/HF demineralization and organic solvent extraction. Total OCPs concentrations of samples were 20.96-134.22 microg x kg(-1), total HCHs concentrations were 5.66-22.87 microg x kg(-1), and total DDTs concentrations were 1.51-11.70 microg x kg(-1). beta-HCH, heptachlor, aldrin, endrin, endosulfan sulfate and methoxychlor were the dominate compounds which took 53.56%-77.26% of total OCPs. Concentrations of free OCPs were 8.46-88.45 microg x kg(-1) and took 40.37%-65.90% of total OCPs while concentrations of bound OCPs were 11.46-45.77 microg x kg(-1) and took 34.10%-59.63% of total OCPs. Most of bound OCPs were in the humic acid and humin fractions of the samples which shows the significantly occurrence of bound OCPs in environment. Distributions of free DDTs and HCHs showed that there were no fresh HCHs poured into these samples but there were fresh DDTs poured into some of the samples. The distribution of OCPs in these two fractions were associated with the organic C content of the fractions, and 94.78%-97.48% of bound OCPs were in humin fraction which took 57.71%-80.55% of total organic C in the samples. Environmental risk estimate showed that some free OCPs such as gamma-HCH, aldrin, endrin and DDTs may have risk to environment and total of free and bound concentration of each compound were 1-30 times higher than free concentration of each compound. Therefore bound OCPs should be considered while making the environmental risk estimate and establishing environmental criteria.
