Impact of nitrogen cycling on stream water quality in a basin associated with forest, grassland, and animal husbandry, Hokkaido, Japan
Impact of nitrogen cycling on stream water quality in a basin associated with forest, grassland, and animal husbandry, Hokkaido, Japan
复制标题
DOI：
10.1016/j.ecoleng.2005.01.011
复制
发表时间：
2005-05
影响因子：
3.8
通讯作者：
R. Hatano;T. Nagumo;Hiroshi Hata;Kanta Kuramochi
中科院分区：
文献类型：
--
作者：
R. Hatano;T. Nagumo;Hiroshi Hata;Kanta Kuramochi
农田和牲畜饲养场废物的直接排放增加了溪流中氮 (N) 的浓度。本研究旨在确定农场氮预算对溪流水质的影响。 1999-2000年，我们对日本北海道南部静内市甲保川流域的一个占地457公顷的实验畜牧场进行了调查，其中草地和玉米田占农场总面积的33%。年氮流量是根据农场的土地管理记录计算的。农田为牲畜提供了 15.2tNyr−1，这使得农场 81% 能够自给自足。牲畜排泄物产生17.2tNyr−1，其中4tNyr−1 损失，可能是由于分解过程中氨的挥发。除粪便外，主要氮输入为化肥9.1tNyr−1、大气沉降6.4tNyr−1、生物固氮12.6tNyr−1。主要产出为森林植被吸收11.0tNyr−1、反硝化1.5tNyr−1 和牲畜饲料生产。因此，整个农场的年剩余氮估计为 12.7tNyr−1，相当于农田的 28kgNha−1。从农场到 Kepau 河的年氮负荷测量为 14.4tNyr−1。然而，百分之九十的负荷发生在降雨和春季融雪期间。在 2 周的融雪期内，排放量为 5.0 tN，相当于年负荷的 35%。尽管农场下方溪流的平均氮浓度为2.8mgNL−1，但融雪季节记录的最大浓度为13.5mgNL−1。随着水流流速的增加，水流中的 N 浓度增加，二氧化硅 (Si) 浓度降低。因此，Si/N 的摩尔比经常降至 2.7 以下，这是发生富营养化的临界水平。降雨和融雪期间的大量氮负荷可归因于露天沟渠，这些沟渠收集田地的排水和地表径流，绕过森林覆盖的河岸带直接排入河流。
The direct discharge of wastes from agricultural fields and livestock feedlots increases the concentration of nitrogen (N) in streams. This study was conducted to determine the impact of farm N budgets on stream water quality. In 1999–2000, we investigated an experimental livestock farm of 457ha in the Kepau River watershed in Shizunai, Southern Hokkaido, Japan, where grasslands and maize fields account for 33% of the farm's total area. Annual N flow was calculated on the basis of the farm's land management records. Livestock was supplied with 15.2tNyr−1from agricultural lands, which made the farm 81% self-sufficient. Livestock excreta produced 17.2tNyr−1, of which 4tNyr−1was lost, probably by ammonia volatilization during decomposition. Apart from manure, the major N inputs were 9.1tNyr−1of chemical fertilizers, 6.4tNyr−1of atmospheric deposition, and 12.6tNyr−1biological N fixation. The major outputs were uptake by forest vegetation of 11.0tNyr−1, denitrification of 1.5tNyr−1, and livestock feed production. Consequently, the annual surplus N on the whole farm was estimated to be 12.7tNyr−1, which corresponds to 28kgNha−1of agricultural land. The annual N load from the farm to the Kepau River was measured at 14.4tNyr−1. Ninety percent of this load, however, occurred during rainfall and spring snowmelt. Within one 2-week snowmelt period, 5.0tN was discharged, which corresponds to 35% of the annual load. Although the average N concentration of stream water below the farm was 2.8mgNL−1, the maximum concentration recorded during the snowmelt season was 13.5mgNL−1. The N concentration of the stream water increased and the silica (Si) concentration decreased as the stream flow rate increased. Consequently, the molar ratio of Si/N frequently dropped below 2.7, the critical level for the occurrence of eutrophication. The large N load during rainfall and snowmelt could be ascribed to open ditches, which collect tile drainage and surface runoff from the fields, discharging it directly to the river, bypassing the forested riparian zone.