Cl, N, C isotopic analysis of common agro-chemicals for identifying non-point source agricultural contaminants

• Published in: Applied geochemistry 2007-07, Vol.22 (7), p.1530-1536
• Main Authors: Annable, W K, Frape, S K, Shouakar-Stash, O, Shanoff, T, Drimmie, R J, Harvey, F E
• Format: Article
• Language: English
• ISSN: 0883-2927
• DOI: 10.1016/j.apgeochem.2007.03.049

The isotopic compositions of commercially available herbicides were analyzed to determine their respective 15N, 13C and 37Cl signatures for the purposes of developing a discrete tool for tracing and identifying non-point source contaminants in agricultural watersheds. Findings demonstrate that of the agrochemicals evaluated, chlorine stable isotopes signatures range between delta 37Cl=-4.55 and +3.40, whereas most naturally occurring chlorine stable isotopes signatures, including those of road salt, sewage sludge and fertilizers, vary in a narrow range about the Standard Mean Ocean Chloride (SMOC) between -2.00 and +1.00. Nitrogen stable isotope values varied widely from delta 15N=-10.86 to +1.44 and carbon stable isotope analysis gave an observed range between delta 13C=-37.13 and -21.35 for the entire suite of agro-chemicals analyzed. When nitrogen, carbon and chlorine stable isotope analyses were compared in a cross-correlation analysis, statistically independent isotopic signatures exist suggesting a new potential tracer tool for identifying herbicides in the environment.