The temporal distribution of organochlorine pesticides (OCPs) was examined in the (210)Pb dated sediment core from the Beibu Gulf, South China Sea. The total OCPs concentrations were in the range of 0.93-26.6 ng g(-1) dry weight. Dichlorodiphenyltrichloroethanes (DDTs) (0.17-24.8 ng g(-1)), Hexachlorocyclohexanes (HCHs) (0.04-0.51 ng g(-1)), Chlordane related compounds (CHLs) (0.22-1.72 ng g(-1)) and endosulfan (n.d.-0.91 ng g(-1)) were the predominant compounds. Similar to most Chinese coastal areas, the levels of DDTs in the Beibu Gulf became elevated since the early 1990s, especially since 2000 despite the ban in 1983 in China. This suggests that the concentrations of DDTs were controlled by several processes, such as land reclamation and soil runoff. The isomer ratios of (p,p'-DDE + p,p'-DDD)/p,p'-DDT, p,p'-DDT/DDTs along with construction land expansion indicated that economic activities, land reclamation, soil runoff and the use of DDT-containing antifouling paints might be responsible for the input of DDT. The ratios of α-HCH/γ-HCH (and γ-HCH/HCHs) and trans-chlordane/cis-chlordane (TC/CC) indicated fresh inputs of lindane and chlordane, respectively. In addition, CC was found to be degraded faster than TC under anaerobic conditions in sediments from the Beibu Gulf.
Organochlorine pesticides (OCPs) including HCH, DDT, chlordane, endosulfan, and endosulfan sulfate were analyzed in surface soil of the Dayan Cave to investigate their source and concentration levels in September 2006. Generally, the data showed that outside soil of the cave had much higher concentrations than inside soil for the most detected OCPs in the cave and both inside soil and outside soil showed much lower concentration levels (basically, the levels of OCPs were less than 0.7 ng/g) than those observed in other regions within and outside China other than TC (ranging from 3.22 to 5.00 ng/g) and CC (ranging from 3.89 to 5.08 ng/g) in the soil outside. The ratios of α-/γ-HCH ranged from 0.88 to 1.20 in the soil of the cave, together with the averaged percentages of β-HCH and δ-HCH among the total HCH isomers (accounting for 39.0% and 14.2%, respectively), implied that a historical residue of local technical HCH contamination was likely to be dominant in the soil of the cave. Based on (1) the accordance of TC/CC ratios (ranging from 0.83 to 0.98) between the values observed in the outside soil and the potentially available chlordane products in the markets, and (2) the high concentrations of TC and CC observed in the outside soil, it appeared that the illegal usage of technical chlordane was done in Guilin. The low concentrations of TC (0.02 to 0.56 ng/g) and CC (0.10 to 1.71 ng/g) in the inside soil, together with the significant distinctions of TC/CC ratios between the inside soil (ranging from 0.03 to 0.33) and the outside soil, implied that the chlordane in the inside soil of the cave was a historical residue of local technical chlordane contamination. The similar ratios of DDT isomers (o, p (')-DDT/p, p (')-DDT and p, p (')-DDE+DDD/DDT) between the outside soil and the inside soil of the cave suggested that they may have the similar DDT source. The ratios of p, p (')-DDE+DDD/DDT (ranging from 3 to 8) indicated that DDT was relatively aged. The values of o, p (')-DDT/p, p (')-DDT ratios (ranging from 3 to 7.5 with a mean value of 5.45) were found to be much higher than that of technical DDT, and very similar to that of dicofol products, implied that the primary source of DDT in the soil of the cave was most probably from dicofol-type DDT products. The low concentration levels of endosulfan and the higher levels of metabolite endosulfan sulfate indicated that the residue from historical usage of technical endosulfan was likely to be dominant in the soil of the cave.
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