Biodegradation of NTA and m‐cresol in coastal environments

Abstract

AbstractThe biodegradation of m‐cresol and nitrilotriacetic acid (NTA) by nonadapted natural populations of aerobic heterotrophic bacteria was examined in a coastal environment near Beaufort, North Carolina, over an 18‐month period and in synoptic samples from the Mississippi River, its plume and adjacent coastal waters. The uptake kinetics of radiolabeled m‐cresol and NTA were measured at a freshwater site, an estuarine site and a high‐salinity offshore site. Uptake of both compounds was greatest in the summer, and half‐saturation constants and maximum uptake velocities were greater for NTA than for m‐cresol. m‐Cresol uptake was greatest in the freshwater environment, and NTA uptake was greatest in the estuary where bacterial numbers and activity were also highest. The uptake of both compounds was lowest in the offshore environment where biological activity was lowest. It appears from the spatial patterns in the Newport River estuary and in areas off the Mississippi that m‐cresol biodegradation is substantially reduced at increasing salinity but that NTA uptake is not. Only at extremely low concentrations (less than 1 to 10 μg L−1) and only during the warmer portions of the year is biodegradation of m‐cresol in freshwater and estuarine environments important in determining its fate. At higher concentrations and in the marine environment, biodegradation by nonadapted populations is slow and other processes, such as adaptation, dilution and mixing, may be more significant in determining the fate of both compounds.