The aim of this paper is to isolate pure cultures that are capable of degrading paraquat (PQ) anaerobically with humic substances (humus) as the sole electron acceptor. Three facultative anaerobic bacteria (PQ-1, PQ-2, and PQ-3) were successively isolated from vegetable soil in Sanya city, China, via enrichment procedure with PQ and anthraquinone-2,6-disulphonate (AQDS) under anaerobic conditions. Batch experiments were conducted to investigate isolates PQ anaerobic degradation activity. Results showed that three strains were all capable of degrading PQ directly with AQDS as the sole electron acceptor (18.6% removal within 48h), and the microbial process might be AQDS dependent. The addition of low molecular weight organic substrate, such as sucrose, could enhance the anaerobic degradation of PQ from 18.6% to 34.2%, and the degradation rate reached 100% after 5-day incubation. This study was the first paper reporting that pure cultures have the ability to anaerobically degrade PQ with AQDS as the sole electron acceptor.
The aim of this paper is to analyze the characteristics of organochlorine pesticides (OCPs) residues in vegetable soils from the middle of Yuanmou. 12 surface soil (0~20 cm) samples of vegetable fields soil were collected and 18 types of OCPs in soil were analyzed by gas chromatography Results show that excepting for α-endosulfan, endrin, aldrin, o,p’-DDT and p,p’-DDT, other 13 types of OCPs was found with different degree in all the samples. The detection rate of 18 types of OCPs was nd~100%, the residue level was nd~11.76 μg•kg-1, OCPs residues were main chlorthiepin sulfate, HCHs and dieldrin. Residues of endosulfan, HCHs and dieldrin in the soils might come from the old usage and residues of heptachlor might come from the recent usage. Contamination of OCPs in soils from the middle of Yuanmou were relative lower than most areas in south of China.
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