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fractions to determine the organic carbon content of these two fractions of suspended material. Sample collection involved centrifugation to isolate the suspended particulate fraction and ultrafiltration to isolate the colloid fraction. For the first time, particulate and colloid concentrations and organic carbon and nitrogen content were investigated along the entire reach of the Mississippi River from above Minneapolis, Minnesota, to below New Orleans, Louisiana. Organic carbon content of the colloid (15.2 percent) was much higher than organic carbon content of the particulate material (4.8 percent). Carbon/nitrogen ratios of colloid and particulate phases were more similar to ratios for microorganisms than to ratios for soils, humic materials, or plants.

The fate of halogenated disinfection byproducts (DBPs) in treatment wetlands and the changes in the DBP formation potential as wastewater treatment plant (WWTP)-derived water moves through the wetlands were investigated. Wetland inlet and outlet samples were analyzed for total organic halide (TOX), trihalomethanes (THM), haloacetic acids (HAA), dissolved organic carbon (DOC), and UV absorbance. Removal of DBPs by the wetland ranged from 13 to 55% for TOX, from 78 to 97% for THM, and from 67 to 96% for HAA. The 24-h and 7-day nonpurgeable total organic halide (NPTOX), THM, and HAA formation potential yields were determined at the inlet and outlet of these wetlands. The effect of wetlands on the production of DBP precursors and their DBP-formation potential yield from wastewater was dramatic. The wetlands increased DBP yield up to a factor of almost 30. Specific changes in the DOC precursors were identified using 13C NMR spectroscopy.

Analysis of leachates from six U.S. municipal landfills revealed the presence of chlorinated 2-phenoxypropionic acid herbicides; however, none of the more widely used acetic acid analogues was present at quantifiable levels. All the leachates contained MCPP. 2,4-DP and silvex were detected in four of the six. The herbicide 2,4-DB was also found in four of the leachates. These compounds persisted in the leachates during 2-3 years of storage while significant depletion of total organic carbon (TOC) in general and of low molecular weight carboxylic acids in particular was observed. Since landfills and leachates are microbially active environments (as demonstrated here by the TOC depletion during storage), this unexpected lack of degradation of several phenoxy herbicides poses concerns for possible groundwater contamination. The concentrations of these herbicides present in the leachates (0-90 µg/L) are consistent with disposal of small quantities of household hazardous waste or disposal of plant materials which contain the herbicides.

A method was developed for the quantitation of the avicide 3-chloro-p-toluidine hydrochloride (CPTH) in pigeon breast muscle and gastrointestinal tract. Accuracy and precision were greatly improved by the use of CPTH-d 6 as a surrogate. CPTH-d 6 was synthesized by the nitration of toluene-d 8 followed by chlorination and reduction. The synthetic product provided mass fragments such that CPTH and the surrogate were differentiated by gas chromatography/mass spectrometry (GC/MS). A tissue extraction process used solid-phase extraction to concentrate the free base forms of CPTH and the surrogate from hexane extracts. These compounds were recovered from the SPE columns with n-butyl acetate and quantified by GC/MS. Validation data indicated (1) a linear relation between CPTH/CPTH-d 6 area ratios and CPTH concentration; (2) a method limit of detection of 30 ppb for both tissue matrices; (3) CPTH recoveries from fortified tissues ranging from 56.4 to 92.4%, whereas surrogate corrected recoveries ranged from 95.0 to 101%; and (4) identical extraction efficiencies of both compounds from each matrix. Keywords: 3-Chloro-p-toluidine hydrochloride; gas chromatography; quantitative analysis; tissue extraction; NMR spectroscopy