Kinetics and Extent of Mineralization of Organic Chemicals at Trace Levels in Freshwater and Sewage

Abstract

A sensitive and rapid method was developed to measure the mineralization of 14 C-labeled organic compounds at picogram-per-milliliter or lower levels in samples of natural waters and sewage. Mineralization was considered to be equivalent to the loss of radioactivity from solutions. From 93 to 98% of benzoate, benzylamine, aniline, phenol, and 2,4-dichlorophenoxyacetate at one or more concentrations below 300 ng/ml was mineralized in samples of lake waters and sewage, indicating little or no incorporation of carbon into microbial cells. Assimilation of 14 C by the cells mineralizing benzylamine in lake water was not detected. Mineralization in lake waters was linear with time for aniline at 5.7 pg to 500 ng/ml, benzylamine at 310 ng/ml, phenol at 102 fg to 10 mg/ml, 2,4-dichlorophenoxyacetate at 1.5 pg/ml, and di-(2-ethylhexyl) phthalate at 21 pg to 200 ng/ml, but it was exponential at several p -nitrophenol concentrations. The rate of mineralization of 50 and 500 ng of aniline per ml and 200 pg and 2.0 ng of the phthalate per ml increased with time in lake waters. The phthalate and 2,4-dichlorophenoxyacetate were mineralized in samples from a eutrophic but not an oligotrophic lake. Addition to eutrophic lake water of a benzoate-utilizing bacterium did not increase the rate of benzoate mineralization at 34 and 350 pg/ml but did so at 5 and 50 ng/ml. Glucose and phenol reduced the percentage of p -nitrophenol mineralized at p -nitrophenol concentrations of 200 ng/ml but not at 22.6 pg/ml and inhibited the rates of mineralization at both concentrations. These results show that the kinetics of mineralization, the capacity of the aquatic community to assimilate carbon from the substrate or the extent of assimilation, and the sensitivity of the mineralizing populations to organic compounds are different at trace levels than at higher concentrations of organic compounds.

Aerobic Biodegradation of Natural and Xenobiotic Organic Compounds by Subsurface Microbial Communities

“…Comparisons of uptake and C 0 2 evolution rates for the compounds used in this study suggest that measuring only mineralization as a means of estimating the amount of substrate metabolized by aquifer solids communities may result in significant underestimation of total metabolism. It has been observed in surface waters that up to 90% of the added xenobiotic substrate is converted to COz [31,32]. With naturally occurring substrates, we observed a range of responses, with mineralization representing from 40 to 75% of total metabolism.…”

Effect of aroclor 1248 concentration on the rate and extent of polychlorinated biphenyl dechlorination

“…This limitation was due to the inherent limit in microbial competence in dechlorinating congeners with certain Cl substitution patterns [2,10]. It is unclear whether this limit is also affected by PCB concentrations, because the microbial population or activity is often determined by substrate concentrations [11][12][13][14].…”

Degradation of Organochlorine Pesticides, Particularly Endosulfan, by Trichoderma Harzianum

“…The current address of A. Katayama is School of Agriculture, Nagoya University, Chikusa, 464-01 Nagoya, Japan. tion of pesticide-degrading enzyme [5] requiring very specific nutritional balance [ 6 ] .…”