Distribution and isotope composition of nitrogen in Bay of Quinte (Lake Ontario) sediments

The concentrations and isotopic compositions of the various forms of nitrogen in silty clay sediments from the Bay of Quinte (Lake Ontario) have been determined. The total organic-N content is high throughout the sediment profiles and generally decreases with depth. On the contrary, exchangeable NH4+-N concentration is quite low and tends to increase with depth in two out of three sediment cores examined. The concentration of non-exchangeable NH4+-N and the 6 N HCl hydrolyzable NH4+-N are relatively constant with depth. Among the N fractions analyzed, the exchangeable NH4+ is most enriched in 15N. In most cases, the delta15N values of the N fractions remain relatively constant with sediment depth. There is no apparent correlation of delta15N values with the N concentration for any of the individual N fractions. The observed ranges in the delta15N values are: exchangeable NH4+, +5-+10%; 6 N HCl hydrolyzable total N and 6 N HCl hydrolyzable NH4+-N, +3.5-+5.5%