1 research outputs found
Concentrations of DDTs and Enantiomeric Fractions of Chiral DDTs in Agricultural Soils from Zhejiang Province, China, and Correlations with Total Organic Carbon and pH
Dichlorodiphenyltrichloroethanes (DDTs) are persistent
organic
pollutants that were widely used in China, especially eastern China,
as insecticides. This work investigated the concentration, dissipation,
and volatilization of DDTs and enantiomeric fractions (EFs) of <i>o</i>,<i>p</i>′-DDD and <i>o</i>,<i>p</i>′-DDT in agricultural soils collected in 2006 from
58 sites in Zhejiang province. Correlations between DDT residues and
soil properties were assessed to determine the effect of soil properties
on the environmental attenuation of DDTs. High concentrations and
detection frequencies were found for DDTs in agricultural soils in
the region even though large-scale use of DDTs was banned over 20
years ago. The amount of DDTs was about 485 tons in the upper 20 cm
of the soil column of cropland in the province in 2010, with a dissipation
half-life of ∼9 years. The mass flux of DDTs was 43 ng m<sup>–2</sup> h<sup>–1</sup>, which corresponds to emissions
of 7.6 tons with an emission factor of 1.6% in 2006. The low <i>p</i>,<i>p</i>′-DDT/<i>p</i>,<i>p</i>′-DDE ratios and high <i>o</i>,<i>p</i>′-DDT/<i>p</i>,<i>p</i>′-DDT
ratios suggest that there were no recent inputs of DDTs but fresh
application of dicofol, which contains DDT (<i>o</i>,<i>p</i>′-DDT in particular) impurities. The significant
positive correlation between concentrations of DDTs and total organic
carbon content (TOC) indicates the distribution of DDTs fit a typical
“secondary distribution” pattern. DEVrac of <i>o</i>,<i>p</i>′-DDD, which is defined as the
absolute value of EFs subtracted from 0.5, was significantly related
with most of the physicochemical and microbial soil properties. The
most significant correlation is that between DEVrac of <i>o</i>,<i>p</i>′-DDD and soil pH (<i>p</i> <
0.001), indicating that the soil pH plays a key role in enantioselective
residues of DDTs