Degradation of the persistent organic pollutant [14C]heptachlor in Japanese field soils.

The fate of [(14)C]heptachlor in Saitama soil and the degradation of [(14)C]heptachlor in four Japanese field soils over 112 d after application were investigated. Heptachlor was degraded mainly to cis-heptachlor epoxide by a biotic process and to 1-hydroxychlordene by an abiotic process in the field soils. Volatilization of heptachlor and cis-heptachlor epoxide from the soil was observed over the experimental period. The amount of 1-hydroxychlordene produced in the soils appeared to be related to the soil water contents. Because heptachlor and heptachlor epoxides are predicted to volatilize to the atmosphere and to persist in soils, these compounds are thought to spread among Japanese environmental compartments even after a ban on their use.

Residues of 18 organochlorine pesticides in 30 traditional Chinese medicines.

We analyzed 30 different traditional Chinese medicines (TCMs) to determine levels of contamination with organochlorine pesticides (OCPs). We tested for 18 pesticides: benzene hexachloride (BHC, including alpha-BHC, beta-BHC, gamma-BHC, delta-BHC), heptachlor, heptachlor epoxide, tecnazene, pentachloronitrobenzene (PCNB), hexachlorobenzene, aldrin, methyl pentachlorophenyl sulphide (MPCPS), alpha-endosulfan, trans-chlorodane, cis-chlorodane, p,p'-DDE, o,p'-DDT, p,p'-DDD, and p,p'-DDT. The sample extracts were analyzed by GC-ECD. A total of 280 samples of 30 different TCMs were analyzed. Our results showed that 75.8% of samples contained at least one of the above pesticides. The pesticides detected were tecnazene, hexachlorobenzene, PCNB, heptachlor, aldrin, alpha-BHC, beta-BHC, gamma-BHC, delta-BHC, p,p'-DDE, o,p'-DDT, p,p'-DDD p,p'-DDT. More than 50% of samples contained alpha-BHC (55.8%) and PCNB (55.8%); hexachlorobenzene was detected in 40.9% of samples, tecnazene in 19.5%, gamma-BHC in 16.7% and p,p'-DDE in 16.0%. Less than 10% of samples contained beta-BHC, delta-BHC, heptachlor, aldrin, o,p'-DDT, p,p'-DDT and p,p'-DDD. None of the 280 samples contained heptachlor epoxide, MPCPS, alpha-endosulfan, trans-chlorodane, or cis-chlorodane. Concentrations of OCPs in four samples exceeded the maximum allowable residue limits (MRLs) specified in the PRC Pharmacopoeia 2005. The results indicate that the most common contaminants among the 280 samples were alpha-BHC, PCNB, hexachlorobenzene, and tecnazene. Our results suggest that contamination of TCMs with OCPs is widespread. The MRLs for other OCPs commonly found in TCMs (e.g. hexachlorobenzene and tecnazene) should be set as quickly as possible, and the MRLs of OCPs in other TCMs should be established.

Removal of aldrin, dieldrin, heptachlor, and heptachlor epoxide using activated carbon and/or Pseudomonas fluorescens free cell cultures.

Degradation of aldrin (1,2,3,4,10,10-Hexachloro-1,4,4a,5,8,8a-hexahydro-1,4:5-8-dimethanonaphthalene), heptachlor (1H-1,4,5,6,7,8,8-heptachloro-3a,4,7,7a-tetrahydro-4,7-methano indene), dieldrin (1aalpha,2beta,2aalpha,3beta,6beta,6aalpha,7beta,7aalpha)-3,4,5,6,9,9-Hexachloro-1a,2,2a,3,6,6a,7,7a-octahydro-2,7:3,6-d-methanonaphtha[2,3-b]oxirene, and heptachlor epoxide (1aalpha, 1bbeta,2alpha,5alpha,5alphabeta,6beta,6aalpha-2,3,4,5,6,7,7-Heptachloro-1a,1b,5,5a,6,6a-hexahydro-2,5-methano-2H-inden[1,2-b]-oxirene) was tested using free cultures of Pseudomonas fluorescens under controlled conditions. Pesticide concentrations were monitored by gas chromatography during 120 h. Percentages of degradation and biodegradation rates (BDR) were calculated. Data showed a trend suggesting a relation between chemical structure and degradability. Degradation kinetics for each pesticide tested showed that the highest degradation rates were found in the first 24 h. Kinetics data were adjusted to an empirical equation in order to predict their behavior, and the correlation coefficients obtained were satisfactory. Gas chromatography/mass spectrometry (GC/MS) analysis of the final extracts allowed the identification of chlordene and monodechlorodieldrin, which have been reported as final metabolite produced in the biodegradation of this kind of compounds. Regarding adsorption of pesticides on activated vegetal carbon, we concluded that removal efficiencies between 95.45 and 97.18% can be reached, depending on the pesticide and the carbon dose applied. The values for K from the Freundlich equation were quite similar for the four pesticides (between 1.0001 and 1.04), whereas the n values were quite different for each pesticide in the following order of affinity: dieldrin > aldrin > heptachlor epoxide > heptachlor. Equilibrium times, very important for scaling up the process, were between 43 min and 1 h, for the heptachlor epoxide and the heptachlor, respectively.

Enantiomeric enrichment of chiral pesticides in the environment.

Enantiomer fractions (EFs) of chiral compounds have been used to explain the mechanisms of enantiomer enrichment in air, soil, water, and biota. The EFs were calculated from enantiomeric ratios (ERs) of chiral compounds measured by researchers during the past 10 years. Six compounds were selected from different abiotic and biotic compartments: alpha-hexachlorocyclohexane (alpha-HCH), mecoprop, cis-chlordane (CC), trans-chlordane (TC), heptachlor exo-epoxide (HEPX), and oxychlordane (OXY). The EF was used as a general descriptor for enantiomer enrichment. In environmental compartments the EFs of chiral pesticides deviated from those of the racemic composition (EF = 0.5). The deviations from EF = 0.5 in the different compartments show similar patterns for several compounds, i.e., air < water < soil < biota. In biota the order was lower trophic level < higher trophic level and liver or kidney tissue < brain tissue. Explanations for stereoselective behavior were found in pharmacology and brain research. The enantiomeric enrichments in environmental compartments were visualized in a general scheme applicable to other persistent chiral compounds. The mechanisms of enantiomer enrichment were conceptualized by a hypothetical model of a chiral machine (enzymatic degradation) and a chiral guard (stereospecific efflux). Environmental regulation authorities should treat chiral pesticides as a composition of enantiomers because biotic processes handle enantiomers as separate chemical entities.