Improvement in municipal wastewater treatment alters lake nitrogen to phosphorus ratios in populated regions
Improvement in municipal wastewater treatment alters lake nitrogen to phosphorus ratios in populated regions
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DOI：
10.1073/pnas.1920759117
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发表时间：
2020-05-26
影响因子：
11.1
通讯作者：
Lin, Yan
中科院分区：
文献类型：
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作者：
Tong, Yindong;Wang, Mengzhu;Lin, Yan
废水处理的大规模和迅速改进是发展中国家的普遍做法，但很少从广泛的空间和时间尺度来考察这种对接收水体营养状况的影响。在这里，我们提出了一项研究，将湖泊的十年营养监测数据与相应的估计值联系起来，估计随着时间的推移，周围流域的五大人为营养物质排放。在一个从2008年到2017年的连续监测数据集中，我们发现，由于TN和TP浓度的变化速度不同，在46个湖泊中，有24个湖泊的TN/TP质量比上升，只有3个湖泊的TN/TP质量比下降。湖泊营养盐浓度(及其比值)与周围流域人为营养盐排放的定量关系表明，湖泊TN/TP比值的增加与城市污水处理的迅速改善有关。由于TP的去除效率高于TN，TN/TP在城市污水排放总量中的质量比从2008年的中位数10.7(95%可信区间7.6至15.1)继续上升至2017年的17.7(95%可信区间13.2至27.2)。改善全世界的城市污水收集和处理是联合国确定的17个可持续发展目标中的一项重要目标。考虑到污水排放中养分比例变化对生物多样性和生态系统功能的潜在生态影响，我们的结果表明，生活污水管理的长期战略不应只关注养分排放的总量减少，还应考虑其化学计量平衡。
Large-scale and rapid improvement in wastewater treatment is common practice in developing countries, yet this influence on nutrient regimes in receiving waterbodies is rarely examined at broad spatial and temporal scales. Here, we present a study linking decadal nutrient monitoring data in lakes with the corresponding estimates of five major anthropogenic nutrient discharges in their surrounding watersheds over time. Within a continuous monitoring dataset covering the period 2008 to 2017, we find that due to different rates of change in TN and TP concentrations, 24 of 46 lakes, mostly located in China's populated regions, showed increasing TN/TP mass ratios; only 3 lakes showed a decrease. Quantitative relationships between in-lake nutrient concentrations (and their ratios) and anthropogenic nutrient discharges in the surrounding watersheds indicate that increase of lake TN/TP ratios is associated with the rapid improvement in municipal wastewater treatment. Due to the higher removal efficiency of TP compared with TN, TN/TP mass ratios in total municipal wastewater discharge have continued to increase from a median of 10.7 (95% confidence interval, 7.6 to 15.1) in 2008 to 17.7 (95% confidence interval, 13.2 to 27.2) in 2017. Improving municipal wastewater collection and treatment worldwide is an important target within the 17 sustainable development goals set by the United Nations. Given potential ecological impacts on biodiversity and ecosystem function of altered nutrient ratios in wastewater discharge, our results suggest that long-term strategies for domestic wastewater management should not merely focus on total reductions of nutrient discharges but also consider their stoichiometric balance.