RECTIFYING TREE RING AND LAKE SEDIMENT NITROGEN ISOTOPE BASED CHRONOLOGIES OF POLLUTION IN THE BIG MOOSE LAKE WATERSHED, NY

The long term terrestrial nitrogen cycle has been affected by anthropogenic nitrogen pollution. Nitrogen isotopes in both tree rings and lake sediments have been used with increasing frequency to reconstruct these changes in the nitrogen cycle. Nitrogen isotopes in both lake sediments and tree rings can be affected by isotopic fractionations within the terrestrial or aquatic environment. These fractionations can confound their interpretation as temporal records. To examine the effect of this on nitrogen cycle reconstruction, tree core, lake sediments and soil samples were taken from the Big Moose Lake watershed (NY). The acid deposition history of this watershed has been well documented. Given the common long term pollution input function to both terrestrial and aquatic components of the watershed, we anticipate that within-soil and within-lake isotopic fractionations will be resolved. These results will contribute to developing a framework for interpreting nitrogen isotope based lake sediment and tree ring chronologies of changes in the nitrogen cycle.