Tracing Atmospheric Nitrate Deposition in a Complex Semiarid Ecosystem Using △17{sup left}O

摘要

The isotopic composition of nitrate collected from aerosols, fog, and precipitation was measured and found to have a large 17{sup left}O anomaly with Δ17{sup left}O values ranging from 20‰ to 30‰ (Δ17{sup left}O = δ17{sup left}O - 0.52(δ18{sup left}O)). This 17{sup left}O anomaly was used to trace atmospheric deposition of nitrate to a semiarid ecosystem in southern California. We demonstrate that the Δ17{sup left}O signal is a conserved tracer of atmospheric nitrate deposition and is a more robust indicator of N deposition relative to standard δ18{sup left}O techniques. The data indicate that a substantial portion of nitrate found in the local soil, stream, and groundwater is of atmospheric origin and does not undergo biologic processing before being exported from the system.