Tracing the fate of atmospheric nitrate deposited onto the ecosystem using the triple oxygen isotopes as tracers

测定了日本利尻岛降水（湿沉降）和地下水（泉水、湖水和溪水）中硝酸盐的稳定同位素组成，以利用δ ^<17>O异常（Δ^<17>O）追踪沉积到该岛生态系统（东亚典型的森林生态系统背景）上的大气硝酸盐的去向。沉积硝酸盐具有较大的^<17>O异常，Δ^<17>O值为+26.2 ‰，为年平均值。另一方面，地下水中硝酸盐的Δ^<17>O值较小，范围为+0.9‰至3.2‰，相当于大气硝酸盐与总硝酸盐的平均混合比为7%。因此，我们估计，直接排水占沉积在岛上的大气硝酸盐的10.5 ± 5.2%，剩余部分在从森林生态系统输出之前经过生物处理。硝酸盐的稳定同位素组成的测定在贫营养的水柱的日本马首湖，以及。然后，这些数据被用来量化硝酸盐在湖泊的地球化学动力学，通过使用大气硝酸盐的沉积速率到整个集水区的湖泊。

The stable isotopic compositions of nitrate in precipitation (wet deposition) and groundwater (spring, lake, and stream water) were determined for the island of Rishiri, Japan, so as to use the ^<17>O anomalies (Δ^<17>O) to trace the fate of atmospheric nitrate that had deposited onto the island ecosystem, which is a representative background forest ecosystem for eastern Asia. The deposited nitrate had large ^<17>O anomalies with Δ^<17>O values with +26.2 ‰ being the annual average. On the other hand, nitrate in groundwater had small Δ^<17>O values ranging from +0.9‰ to 3.2‰, which corresponds to an average mixing ratio of atmospheric nitrate to total nitrate of 7%. Thus, we estimated that the direct drainage accounts for 10.5 ± 5.2% of atmospheric nitrate that has deposited on the island and that the residual portion has undergone biological processing before being exported from the forest ecosystem. The stable isotopic compositions of nitrate were determined in the oligotrophic water column of Lake Mashu, Japan, as well. These data were then used to quantify the geochemical dynamics of nitrate in the lake, by using the deposition rate of the atmospheric nitrate onto the entire catchment area of the lake.