Distribution Characteristics and Source Apportionment of DDTs and HCHs in Soils from Apple Orchards in Yantai, Shandong Province

In order to study characteristics of residues, levels of degradation and sources of organochlorine pesticides (OCPs), Gas Chromatography-Electron Capture Detector (GC-ECD) was used to determine concentrations of DDTs and HCHs in 9 different types of root system soil and soil profiles from apple orchards in Yantai, Shangdong Province. None of the DDTs and HCHs in the soil samples exceeded the guidelines of 500 ng/g in the Chinese environmental quality standard for soils. The mean concentration of DDTs and HCHs were 71.7 ng/g and 7.9 ng/g, respectively. The detection rate of DDTs was 100%, while only 19.7% of soil samples contained HCHs. The mean levels of DDTs isomers hosted in the root system soil decreased in the following orders: p,p'-DDT> p,p'-DDE> o,p'-DDT > p,p'-DDD, while HCHs isomers were mainly α-HCH with minor β-HCH and γ-HCH. Distribution of OCPs varied in different types of soil: highest concentration of DDTs occurred in brunisolic soil (Zangjiazhuang, 145.5 ng/g) and lowest occurred in medium-grained sandy soil (Wuning, 24.1 ng/g). The highest concentration of HCHs occurred in fine sandy loam (Shewo, 27.9 ng/g). DDTs in soil profiles accumulated in depths within 20 cm. The results of source apportionment of DDTs and HCHs indicated all soil from the research area was aerobic. There were new sources of DDTs for linen sandy brunisolic soil (Guandao and Taocun), fine loam (Muping), fine sandy loam (Shewo) and brunisolic soil (Zangjiazhuang). No new sources of HCHs for most root system soil were apparent, but lindane may still have been used in linen sandy brunisolic soil (Taocun) after HCHs were restricted in China.