Investigation on the chemical structure of nonextractable residues of the fungicide cyprodinil in spring wheat using 13C-C1-phenyl-cyprodinil on 13C-depleted plants-an alternative approach to investigate nonextractable residues

13C-labelled cyprodinil was applied on 13C-depleted wheat plants with 27-fold field application rate. A control experiment applying same amounts of 14C-cyprodinil showed that main portions of the residues were detected in the cellulose (15% NER), hemicellulose (28.3% NER), and lignin fraction (23.3% NER). 16.7% were detected in water soluble polymers, 6% in both, pectin and protein fraction, and 4% in the starch containing fraction. Free cyprodinil was detectable by TLC in all fractions except lignin. A direct characterization of the residues in vivo by CP-MAS was not successful. Cell wall fractions were further analysed by liquid state NMR to determine the structure of the mobilized highly polymer/polar residues: Within lignin, where most of the residues were located at field application rate, neither intact cyprodinil nor its metabolites could not be detected. The 13C-label introduced was probably incorporated in the polymer as natural lignin monomers and thus are not considered as bound residues according to IUPAC definition.     

Biodegradation of low aqueous concentration pentachlorophenol (PCP) contaminated groundwater

Bioremedial treatment to remove low level organic contamination to regulatory standards has met with limited success. In this study source water from a contaminated surficial aquifer at a former wood treatment facility was used to evaluate the potential for indigenous microorganisms to degrade low level (< 1.0 mg) pentachlorophenol (PCP) to a regulatory drinking water standard of 0.001 mg/L. PCP degradation was evaluated in series of batch reactors in a two phase study to (a) determine the rate and extent of PCP removal and (b) evaluate the impact of nutrient amendment (N and P) on removal rate. All reactors with the exception of the abiotic control demonstrated PCP removal to a level < 0.002 mg/L within a maximum period of 32 d with and without nutrient amendment. A regression analysis of reactive phosphate (ortho-P) concentration versus removal rate produced an R2 of 0.94 (p = 0.006) indicating a significant correlation between the level of available phosphate and PCP degradation rate. Selective bacterial enumeration (for PCP degrading bacteria) revealed PCP-degrading bacteria increased in abundance prior to and in conjunction with the degradation phase to a density of between 10(3) to 10(4) CFU/ml. Isolates were also analyzed for total fatty acids using Fatty Acid Methyl Ester (FAME) methodology and the results indicated that PCP degrading bacteria were present in the aquifer and consisted of predominately fluorescent, oxidase positive Pseudomonas species. Overall, data indicate that autochthonous microbes are capable of removing low level PCP (< 1.0 mg/L) to approach if not reach the regulatory standard of 0.001 mg/L with the addition of oxygen, with or without nutrient amendment. Results of this research can be applied to full-scale implementation of in-situ or ex-situ bioremediation of groundwater at former wood treatment facilities.