Jiaquan Zhang

Organochlorine pesticides (OCPs) in soils and sediments, southeast China: A case study in Xinghua Bay

This study evaluated the contamination status and distribution of organochlorine pesticides (OCPs) between Xinghua Bay and adjacent watersheds in Putian region, southeast China. Twenty-five surface soil samples and two sediment cores were collected from two watersheds and the Xinghua Bay, respectively. Results showed that the concentrations of OCPs in samples of the Mulan River Watershed (MRW), the Qiulu River Watershed (QRW), the inner bay core (IBC) and the open bay core (OBC) were in the range of 4.96-38.20ng/g, 4.62-22.80ng/g, 1.84-80.46ng/g and 1.87-23.43ng/g, respectively. The mean concentration of OCPs was in an order: IBC>MRW>QRW>OBC. The higher concentration of OCPs in recent periods may suggest that a certain amount of OCPs were still input to this area.

Residues of Organochlorine Pesticides (OCPs) in Agricultural Soils of Zhangzhou City, China

A soil survey was conducted in Zhangzhou City, an important agricultural region in south of the Fujian Province, China. 93 surface soil samples were collected in the paddy fields, vegetable lands, orchards and tea plantations from Zhangzhou City. An additional soil profile was sampled in a paddy field as previous research had indicated high concentrations of organochlorine pesticides (OCPs) in the paddy fields. Dichlorodiphenyltrichloroethanes (DDTs) ranged from 0.64–78.07 ng g −1 dry weight and hexachlorocyclohexanes (HCHs) ranged from 0.72–30.16 ng g −1 dry weight in the surface soil of the whole study region. Ratios of α-HCH/γ-HCH 1 in all soil samples suggested that lindane and dicofol were widely applied in this region in the past. Concentrations of HCHs and DDTs in soils from the four land use types followed the orders: paddy fields > vegetable lands > tea plantations > orchards and tea plantations > orchards > paddy fields > vegetable lands, respectively. Analyses of the data showed no correlation ( r< 0.1) between elevation and OCPs contents in paddy fields, orchards and vegetable lands, indicated no significantly different features in distribution of HCHs and DDTs in the soils from low lying plains and mountains and the unsystematic usage of OCPs, and highlighted the fragmented nature of agricultural production in Zhangzhou, as well as the reemission of OCPs from the soils, where high OCPs concentrations were found, in Longhai of Zhangzhou. In addition, no obvious relationship between the OCPs and total organic carbon (TOC) ( r< 0.3) was observed in the soil profile. The mean contribution of dicofol in total DDTs was 66% in the whole Zhangzhou region. The approximate burdens of HCHs and DDTs in the surface layer of 0–20 cm were 0.44 and 1.55 t, respectively. The storage of both HCHs and DDTs in soil surface layer (0–20 cm) accounts for 40% burden of the soil layer of 0–50 cm (1.10 t HCHs and 3.87 t DDTs), in which the highest concentrations of OCPs were observed in soil profile.

Concentrations and classification of HCHs and DDTs in soil from the lower reaches of the Jiulong River, China

Soil is an important source to other environmental media and organisms for organochlorine pesticides (OCPs) bioaccumulation. Twenty-four representative surface soil samples were collected from the lower reaches of the Jiulong River, China, in 2009. The concentrations of hexachlorocyclohexane isomers (HCHs) ranged from 0.38 to 39.52 ng·g−1, with a mean value of 9.51 ng·g−1. The concentrations of dichlorodiphenyltrichloroethanes (DDTs) and their metabolites were within the ranges of 0.94–700.99 ng·g−1, with a mean value of 71.17 ng·g−1. The concentrations of HCHs and DDTs in the soil were lower than the first grade level (50 ng·g−1) of the Chinese Environmental Quality Standard (GB15618-1995). Hierarchical Cluster Analysis (HCA) and Pearson’s bivariate Correlations Analysis (PCA) were used to analyse the distribution and contamination levels of OCPs in this region. The results showed that DDTs were the major contaminants and there were no significant correlations between various OCPs concentrations and the total organic carbon (TOC) contents. A significant positive correlation was observed between HCHs and DDTs (p<0.01), which indicates that HCHs and DDTs may have similar sources and fate in the study area.

Spatial distribution of HCH and DDT in soil from the Wuyi Mountains southern, Fujian, Southeast China

In order to study the levels and spatial distribution of organochlorine pesticides in soil samples from the Wuyi Mountains southern. The 30 soil samples were collected from the study area. The concentrations of OCPs in the samples were determined by GC-ECD with the internal standard method. The results showed that HCHs and DDTs were found widely in all samples and the concentrations of HCHs, DDTs in soils of the Wuyi Mountains were in the ranges of 1.14 – 30.62 ng g⁻¹ (with a mean 5.04 ng g⁻¹), 0.96 – 9.62 ng g⁻¹ (with a mean 3.99 ng g⁻¹), respectively. Compared to the reference data of Antarctic and Tebat area, the status of this area can be called “low pollution”. Through source analysis, β-HCH and o,p-DDT was the major source of HCHs, DDTs, respectively. The results indicated that HCHs in this area were historical application. But, new DDTs (dicofol) could be used recently in this area.