Spatial distribution of nitrate sources of rivers in the Lake Biwa watershed, Japan: Controlling factors revealed by nitrogen and oxygen isotope values
Spatial distribution of nitrate sources of rivers in the Lake Biwa watershed, Japan: Controlling factors revealed by nitrogen and oxygen isotope values
复制标题
DOI：
10.1029/2009wr007871
复制
发表时间：
2010-07
影响因子：
5.4
通讯作者：
N. Ohte;I. Tayasu;A. Kohzu;C. Yoshimizu;K. Osaka;Akiko Makabe;K. Koba;N. Yoshida;T. Nagata
中科院分区：
文献类型：
--
作者：
N. Ohte;I. Tayasu;A. Kohzu;C. Yoshimizu;K. Osaka;Akiko Makabe;K. Koba;N. Yoshida;T. Nagata
为了弄清流入日本琵琶湖的河流中溶解的硝酸盐（NO3−）的路径和来源，对NO3−的浓度和同位素组成进行了三种类型的协调调查：（1）对32条代表性流入河流进行天气河流采样，（2）在不同土地利用的集水区的两条河流，以及（3）源头集水区采样。本文使用的数据集是亚洲大型流域河流中NO3-同位素组成的第一个全面收集。虽然NO3−的空间浓度模式显示出显著的季节变化，但溶解NO3−的δ 15 N的空间模式全年都比较一致。与各流域的种群密度呈显著正相关。建立了一个假定反应器内温度和污水流量的质量平衡模型.该模型模拟的人口密度和之间的关系，合理的好，这表明，占主导地位的来源是污水排放量的增加。的时空分布表明，通过降水增加大气来源的NO3-的可能性，并表示在不同的土地利用的NO3-出口的水文途径。在森林占主导地位的集水区与自然排水系统，略高的δ 18 ONO 3信号仍然在溪流中，即使在基流条件。这项研究表明，多尺度，多同位素调查是一个很有前途的战略，描述的空间分布的NO3−源天气和土地利用变化的影响是有用的。
To clarify the pathways and origins of dissolved nitrate (NO3−) in rivers flowing into Lake Biwa, Japan, three types of coordinated surveys of concentrations and isotope compositions of NO3− were conducted: (1) synoptic river sampling of 32 representative inflow rivers, (2) two rivers in catchments with different land uses, and (3) headwater catchment samplings. The data set used in this paper is the first comprehensive collection of isotopic composition of NO3− in rivers of a large‐scale basin in Asia. While the NO3− spatial concentration pattern showed significant seasonal variation, the spatial pattern of the δ15N of dissolved NO3− was more consistent throughout the year. The was significantly positively correlated with the population density of each catchment. A mass balance model assuming the and the flow rate of sewage effluent was developed. The model simulated the relationship between the population density and the reasonably well, suggesting that the dominant source contributing to the increase in was the sewage effluent. The spatiotemporal distribution of suggested the possibility of the addition of atmospherically derived NO3− through precipitation and was indicated by the hydrological pathways for NO3− exports in different land uses. In forest‐dominated catchments with natural drainage systems, a slightly elevated δ18ONO3 signal remained in the stream water even during base flow conditions. This study demonstrated that multiscale, multi‐isotopic investigation is a promising strategy for describing the spatial distribution of NO3− sources synoptically and is useful for evaluating the influences of land use change.