National Risk Management Research Laboratory, Office of Research and Development, US Environmental Protection Agency, 26 West Martin Luther King Drive, Cincinnati, Ohio 45268, USA.
Environ Sci Technol. 2010 Oct 1;44(19):7527-33. doi: 10.1021/es1016735.
Models suggest that microbial activity in streams and rivers is a globally significant source of anthropogenic nitrous oxide (N(2)O), a potent greenhouse gas, and the leading cause of stratospheric ozone destruction. However, model estimates of N(2)O emissions are poorly constrained due to a lack of direct measurements of microbial N(2)O production and consequent emissions, particularly from large rivers. We report the first N(2)O budget for a large, nitrogen enriched river, based on direct measurements of N(2)O emissions from the water surface and N(2)O production in the sediments and water column. Maximum N(2)O emissions occurred downstream from Cincinnati, Ohio, a major urban center on the river, due to direct inputs of N(2)O from wastewater treatment plant effluent and higher rates of in situ production. Microbial activity in the water column and sediments was a source of N(2)O, and water column production rates were nearly double those of the sediments. Emissions exhibited strong seasonality with the highest rates observed during the summer and lowest during the winter. Our results indicate N(2)O dynamics in large temperate rivers may be characterized by strong seasonal cycles and production in the pelagic zone.
模型表明，溪流和河流中的微生物活动是人为氧化亚氮（N2O）的重要全球来源，N2O 是一种强效温室气体，也是平流层臭氧破坏的主要原因。然而，由于缺乏对微生物 N2O 产生和随之产生的排放的直接测量，模型对 N2O 排放的估计受到严重限制，特别是对于大型河流。我们根据从水面直接测量的 N2O 排放和沉积物和水柱中的 N2O 生产，报告了第一个大型富氮河流的 N2O 预算。由于来自污水处理厂废水的 N2O 的直接输入以及原位生产速率较高，俄亥俄州辛辛那提市下游的 N2O 排放最大，俄亥俄州辛辛那提市是这条河上的一个主要城市中心。水柱状和沉积物中的微生物活性是 N2O 的来源，水柱状的生产速率几乎是沉积物的两倍。排放表现出强烈的季节性，夏季最高，冬季最低。我们的结果表明，大型温带河流中的 N2O 动态可能以强烈的季节性循环和浮游区的生产为特征。
