Bedrock weathering rates, reactive nitrogen influxes and effluxes, and nitrous oxide emissions rates from the Pumphouse Hillslope, East River Watershed, Colorado

Atmospheric nitrous oxide contributes directly to global warming, yet models of the nitrogen cycle do not account for bedrock, the largest pool of terrestrial nitrogen, as a source of nitrous oxide. Although it is known that release rates of nitrogen from bedrock are large, there is an incomplete understanding of the connection between bedrock-hosted nitrogen and atmospheric nitrous oxide. Here, we quantify nitrogen fluxes and mass balances at a hillslope underlain by marine shale. We found that at this site bedrock weathering contributes 78% of the subsurface reactive nitrogen, while atmospheric sources (commonly regarded as the sole sources of reactive nitrogen in pristine environments) account for only the remaining 22%. About 56% of the total subsurface reactive nitrogen denitrifies, including 14% emitted as nitrous oxide. The remaining reactive nitrogen discharges in porewaters to a floodplain where additional denitrification likely occurs. We also found that the release of bedrock nitrogen occurs primarily within the zone of the seasonally fluctuating water table and suggest that the accumulation of nitrate in the vadoes zone, often attributed to fertilization and soil leaching, may also include contributions from weathered nitrogen-rich bedrock. Our hillslope study suggests that under oxygenated and moisture-rich conditions, weathering of deep, nitrogen-rich bedrock makes an important contribution to the nitrogen cycle. The data files are in Excel, which can be accessed using Microsoft Office, and consist of many data sets from the Pumphouse Hillslope PLM (Pumphouse Lower Montane) 1, 2, 3, and 4. They include soil to rock (0-10 meters) solid phase minerals and elements compositions; time- and depth-resolved pore-water chemistry and pore-gas compositions; time- and depth-resolved water table depths and water fluxes; subsurface weathering rates; nitrogen influxes and effluxes and mass balance. The attached paper is in a Word document, which can be accessed using Microsoft Office, and in pdf format.

大气中的一氧化二氮（nitrous oxide）直接加剧全球变暖，然而当前的氮循环模型并未将基岩（bedrock）——陆地最大的氮储库——视为一氧化二氮的来源。尽管已知基岩释放的氮通量可观，但学界对基岩赋存氮与大气一氧化二氮之间的关联仍缺乏完整认知。
本研究以海相页岩为基底的山坡为研究对象，量化了其中的氮通量与质量平衡。研究发现，该点位的基岩风化贡献了78%的地下活性氮，而大气来源（通常被认为是原生环境中活性氮的唯一来源）仅占剩余的22%。约56%的地下活性氮发生反硝化作用，其中14%以一氧化二氮的形式排放。剩余活性氮随孔隙水排入泛滥平原，该区域大概率会发生额外的反硝化过程。
本研究还发现，基岩氮的释放主要发生在季节波动水位带内，并提出：通常被归因于施肥与土壤淋溶的包气带（vadose zone）硝酸盐积累，或许也包含富氮风化基岩的贡献。
本山坡研究表明，在富氧且湿度充足的条件下，深部富氮基岩的风化对氮循环具有重要贡献。
本研究的数据集以Excel格式存储，可通过Microsoft Office打开，包含来自Pumphouse Hillslope PLM (Pumphouse Lower Montane) 1、2、3、4号样地的多组数据，具体包括：岩土界面（0~10米）的固相矿物与元素组成；时间与深度分辨率的孔隙水化学、孔隙气体组成；时间与深度分辨率的地下水位深度与水通量；地下风化速率；氮输入输出通量与质量平衡。
附带的研究论文以Word文档格式存储，可通过Microsoft Office打开，同时提供PDF格式版本。