Chemistry Department, Faculty of Science, University of Malaya, Kuala Lumpur, Malaysia.
Department of Environmental Science and Technology, University of Maryland, College Park, MD, United States of America.
PLoS One. 2020 Feb 28;15(2):e0229715. doi: 10.1371/journal.pone.0229715. eCollection 2020.
Stormwater runoff is a leading cause of nitrogen (N) transport to water bodies and hence one means of water quality deterioration. Stormwater runoff was monitored in an urban residential catchment (drainage area: 3.89 hectares) in Florida, United States to investigate the concentrations, forms, and sources of N. Runoff samples were collected over 22 storm events (May to September 2016) at the end of a stormwater pipe that delivers runoff from the catchment to the stormwater pond. Various N forms such as ammonium (NH4-N), nitrate (NOx-N), dissolved organic nitrogen (DON), and particulate organic nitrogen (PON) were determined and isotopic characterization tools were used to infer sources of NO3-N and PON in collected runoff samples. The DON was the dominant N form in runoff (47%) followed by PON (22%), NOx-N (17%), and NH4-N (14%). Three N forms (NOx-N, NH4-N, and PON) were positively correlated with total rainfall and antecedent dry period, suggesting longer dry periods and higher rainfall amounts are significant drivers for transport of these N forms. Whereas DON was positively correlated to only rainfall intensity indicating that higher intensity rain may flush out DON from soils and cause leaching of DON from particulates present in the residential catchment. We discovered, using stable isotopes of NO3-, a shifting pattern of NO3- sources from atmospheric deposition to inorganic N fertilizers in events with higher and longer duration of rainfall. The stable isotopes of PON confirmed that plant material (oak detritus, grass clippings) were the primary sources of PON in stormwater runoff. Our results demonstrate that practices targeting both inorganic and organic N are needed to control N transport from residential catchments to receiving waters.
雨水径流是氮（N）向水体输送的主要原因，也是水质恶化的一种手段。在美国佛罗里达州的一个城市居民区（排水面积：3.89 公顷）进行了雨水径流监测，以研究 N 的浓度、形态和来源。在雨水管道末端收集了 22 场暴雨事件（2016 年 5 月至 9 月）的径流样本，这些雨水从集水区输送到雨水池。测定了各种 N 形态，如铵（NH4-N）、硝酸盐（NOx-N）、溶解有机氮（DON）和颗粒有机氮（PON），并使用同位素特征工具推断了收集到的径流样品中 NO3-N 和 PON 的来源。DON 是径流中主要的 N 形态（占 47%），其次是 PON（22%）、NOx-N（17%）和 NH4-N（14%）。三种 N 形态（NOx-N、NH4-N 和 PON）与总降雨量和前干期呈正相关，表明较长的干期和较高的降雨量是这些 N 形态迁移的重要驱动因素。而 DON 仅与降雨量强度呈正相关，表明高强度降雨可能会将 DON 从土壤中冲刷出来，并导致存在于居民区集水区中的 DON 从颗粒中浸出。我们发现，利用硝酸盐的稳定同位素，在降雨量更高、持续时间更长的事件中，硝酸盐的来源从大气沉降转变为无机氮肥。PON 的稳定同位素证实，植物材料（橡树枝屑、草屑）是雨水径流中 PON 的主要来源。我们的研究结果表明，需要针对无机氮和有机氮采取措施，以控制居民区集水区向受纳水体的 N 迁移。
