Dataset for seasonal and climatic drivers of wet deposition organic matter at the continental scale

Dissolved organic matter (DOM) concentrations and composition within wet deposition are rarely monitored despite contributing a large input of bioavailable dissolved organic carbon (DOC) and nitrogen (DON) to the earth’s surface. Lacking from the literature are spatially comprehensive assessments of simultaneous measurements of wet deposition DOC and DON chemistry and their dependencies on metrics of climate and environmental factors. Here, we use archived precipitation samples from the US National Atmospheric Deposition Program collected in 2017–2018 from 17 sites across ecoregions of the United States to investigate variability in the concentration and composition of depositional DOM. We hypothesize metrics of DOM chemistry vary with season, ecoregion, large-scale climate drivers, and precipitation geographic source. Findings indicate differences in DOC and DON concentrations among ecoregions with highest concentrations in the Northern Forests and lowest concentrations in Marine West Coast Forests. Summer and autumn samples contained the highest DOC concentrations and DON concentrations that were consistently above detection limit. DOC: DON ratios exhibit lower values on the west coast and higher ratios toward the east coast. Compositional trends suggest lighter DOM molecules in autumn and winter and heavier molecules in spring and summer. Climate drivers explain 62% of variation in DOM chemistry, revealing distinct influences on the concentrations of DOC versus DON. This study highlights the necessity of incorporating DOC and DON measurements into national deposition monitoring networks, and offers insights into the influence of climate change on wet deposition DOM.

尽管湿沉降可为地表输入大量可生物利用的溶解性有机碳（dissolved organic carbon, DOC）与溶解性有机氮（dissolved organic nitrogen, DON），但目前针对湿沉降中溶解性有机质（dissolved organic matter, DOM）的浓度与组成的监测仍较为匮乏。现有研究尚未针对湿沉降DOC与DON化学特征的同步监测开展空间全覆盖评估，亦未明确其与气候及环境因子指标的关联关系。本研究依托美国国家大气沉降计划（US National Atmospheric Deposition Program）2017-2018年间采集的存档降水样品，涵盖美国境内17个不同生态区的采样点位，旨在探究沉降性DOM的浓度与组成特征的空间变异性。本研究提出假设：DOM化学特征指标会随季节、生态区、大尺度气候驱动因子以及降水的地理来源发生变化。研究结果显示，不同生态区的DOC与DON浓度存在显著差异：北部森林生态区的浓度最高，海洋性西海岸森林生态区的浓度最低。夏季与秋季的降水样品中DOC浓度最高，且DON浓度均持续高于检出限。DOC:DON比值在西海岸较低，而东海岸地区该比值相对更高。组成特征的变化趋势表明，秋、冬季的DOM分子质量相对更轻，春、夏季的DOM分子质量相对更重。气候驱动因子可解释62%的DOM化学特征变异，且其对DOC与DON浓度的影响存在显著差异。本研究强调了将DOC与DON监测纳入国家沉降监测网络的必要性，并为理解气候变化对湿沉降DOM的影响提供了新的视角。