Heterogeneous Atmospheric Nitrogen Deposition Effects Upon the Nitrate Concentration of Stream Waters in a Forested Mountain Area

Nitrogen compounds generated by anthropogenic combustion deposits in forest watersheds and induce nitrogen saturation of the area. Because excess nitrogen is derived from atmospheric deposition, this action is expected to uniformly affect a wide area of forest soils. Geographically, heterogeneous nitrate concentration of stream water within a small area has been attributed to the tree type, geological setting and tree cut. In this article, we hypothesized that the effect of the atmospheric nitrogen deposition in the forest watershed may vary within a small area, and that such variation is induced by the degree of air mass containing a high concentration of nitrogen deposition of combustion origin. We measured major ion concentrations, including nitrate, nitrite oxygen and nitrogen stable isotope of nitrate sampled at 24 water streams in the Chichibu region, which is 50?C100 km from the Tokyo metropolitan area. The nitrate concentration showed a wide range (25.6?C237 ??mol L^?1) within 300 km², which was explained sufficiently by the air mass advection path and its contact with the mountain??s surface. The nitrate concentration showed a significant positive correlation with chloride (r?=?0.73; p?<?0.001). As chloride originates outside of the Chichibu region, the positive correlation between two ions showed that the nitrate concentration of the stream water was affected by the nitrogen compound from the Tokyo Metropolitan area as a form of atmospheric deposition. Between the nitrate concentration and the stable isotope ratio of oxygen of nitrate, there was a positive correlation until nitrate concentration of 100 ??mol L^?1. When the nitrate is over 100 ??mol L^?1, ??¹⁸O shows a stable value of ca. 5.7??. This indicates that the nitrification proceeds when the nitrate concentration was low to middle, but the reaction slowed when the nitrate concentration became high. Oxygen stable isotope of nitrate along with a set of nitrate concentrations can be used as a good indicator of nitrogen saturation.     

Mechanisms of Nitrate Transfer from Soil to Stream in an Agricultural Watershed of French Brittany

In French Brittany, water pollution with nitrate due tointensive agriculture has become one of the major environmentalconcerns. In this article, the nitrate, sulfate and chlorideconcentrations from the groundwater and the stream of a first-order agricultural watershed, are analyzed to infer the mechanisms responsible for the distribution and transfer of nitrate within the watershed. The aquifer is constituted by three layers: the thin soil cover, the weathered shale and thefissured shale. The weathered shale groundwater appears to bea large reservoir of nitrate in the watershed. Indeed the amount of nitrate is estimated at about 450 kg N ha^-1, 5 to 9 times the total annual nitrate flux in the stream. In the upslope zones, this groundwater exhibited high nitrate concentrations (up to 138.4±10.5 mg NO₃ ^- L^-1), which decreased along the flow paths towards the stream (77.1±13.8 mg NO₃ ^- L^-1). Unlike nitrate, sulfate concentrations showed an increase from uphillto downhill (from 6.1±0.8 to 12.5±5.4 mg SO₄ ^2- L^-1) with little change in chloride concentrations. These patterns are presumed to result from upward flows from fissured shale groundwater where denitrification by oxidation of pyrite occurs with sulfate as end product. A scheme of nitrate transfer is proposed where stream discharge would result from the mixing of three end members which are: uphill weathered groundwater, deep groundwater and water in the uppermost soil horizons ofthe bottomlands. Temporal variability of nitrate concentrationsin base flow reflects changes in the relative contribution of each end member.     

宁化江溪小流域紫色土水土流失综合治理

紫色土水土流失严重的三明市宁化江溪小流域,致力用好国债资金,以小流域为单元,采取植物、工程与耕作措施相结合,山、水、田、林、路综合整治,并强化预防保护,依法监督管理,有效改善和保护生态环境,减少水土流失,促进经济发展,达到治理一片,成效一片。     

Effects of Nitrogen Fertilization on Stream Chemistry of Japanese Forested Watersheds

Steam chemistry was investigated from May 1991 through April 1992 for 13 Japanese forested watersheds and from May 1990 through August 1994 for two of these watersheds. Nine watersheds were treated over different periods (1983–1991) with different amounts of N (nitrogen) fertilizer as urea and ammonium salts. Total N additions ranged from 20 to 375 kg ha^-1. There were no distinct seasonal differences in stream NO₃ ^- concentrations in either the treated or untreated watersheds, but concentrations tended to be somewhat higher during periods of high discharge. The annual average NO₃ ^- concentrations in streams had a significant, positive (p < 0.001, r = 0.84) relationship to the total amount of N applied from 1985–1991. The application of 330 kg N ha^-1 raised annual average stream NO₃ ^- concentration to about 300 μeq L^-1 compared to less than 160 μeq L^-1 in untreated watersheds. The concentrations of K⁺, Ca²⁺, and Mg2+ in stream water also increased in those watersheds with high rates of N fertilizer as a result of nitrification that increased the generation of the mobile nitrate anion. The lack of seasonality in stream NO₃ ^- concentrations and the large rates of N loss with N addition both suggest that these watersheds were ‘nitrogen saturated’     

浅谈鸠坑溪小流域水土流失综合治理

南方红壤丘陵区山多地少,坡耕地水土流失非常严重,坡耕地治理是小流域治理和水土保持工作的一项重要任务。结合淳安县几年来小流域治理和鸠坑溪小流域水土流失综合治理的实践经验,对小流域水土流失治理尤其是坡耕地整治作了一些探讨。     

Long-Term Nitrate Export Pattern from Hubbard Brook Watershed 6 Driven by Climatic Variation

From 1964 through 1994, the pattern of nitrate (NO₃ ^?) export from Watershed 6 at Hubbard Brook Experimental Forest (HBEF) in New Hampshire, U.S.A., exhibited 10 years of high export (1968–1977) followed by 12 years of low export (1978–1989), with four ‘spikes’ in 1970, 1973, 1976, and 1990. Disruptions of N cycling by soil freezing, insect defoliation, or drought have been suggested to explain this pattern. We developed a model of nitrogen dynamics demonstrating that most of the long-term pattern can be reproduced without explicit consideration of these events. Comparisons of simulated N fluxes between high and low export years suggested that inorganic N input to the soil, from both atmospheric N deposition and N mineralization, was significantly higher during periods of high streamflow NO₃ ^? flux than in low periods. Simulated inorganic N pools (ammonium and nitrate) and fluxes (nitrification, plant uptake, denitrification, and ammonia volatilization) were also significantly higher in these periods. By swapping the time sequences of inorganic N input between high and low export years, it was shown that N mineralization, not atmospheric N deposition, drives the simulated long-term pattern. Although simulated nitrification showed a stronger relationship with measured streamflow NO₃ ^? flux than did N mineralization, nitrification rate depended upon availability of soil ammonium supplied from N mineralization. Because N mineralization in the model varies only with soil temperature and moisture, we conclude that shifts in the interaction of these two variables over time produced the shifts in NO₃ ^? stream exports.     

Element Budgets in a Forested Watershed in Southern China: Estimation of a Proton Budget

We evaluated the element budgets in a forested watershed in Jiulianshan, southern China. The element input in bulk precipitation was characterized by high depositions of H⁺, NH₄ ⁺, Ca²⁺, and SO₄ ^2?, i.e., 400, 351, 299, and 876 eq/ha/yr, respectively. The outputs of H⁺, NH₄ ⁺, and SO₄ ^2? from the watershed were very low, while those of Ca²⁺ and Mg²⁺ were high, 712 and 960 eq/ha/yr, respectively. The element budgets suggested that i) the net retentions of H⁺, NH₄ ⁺, and SO₄ ^2? in this watershed were high, and ii) the net release of Mg²⁺ from this watershed was high mainly due to weathering. The net release of Ca²⁺ was not so high because of the high atmospheric deposition, while atmospheric deposition of Mg²⁺ was not so high (130 eq/ha/yr). Decrease of acid neutralizing capacity in the soil, i.e., net soil acidification, was caused mainly by the net release of Mg²⁺. Moreover, the net retention of SO₄ ^2? also contributed to soil acidification.     

Effects of Feral Pig (Sus scrofa) Exclusion on Enterococci in Runoff from the Forested Headwaters of a Hawaiian Watershed

Water, Air, &; Soil Pollution - The role feral pigs (Sus scrofa) as a source of fecal contamination in Pacific Island ecosystems is not well understood. This study investigated the effects of...     

Atmospheric Inputs of Mercury and Organic Carbon into a Forested Upland/Bog Watershed

Inputs of mercury (Hg) and dissolved organic carbon (DOC) in throughfall and stemflow waters were measured for an upland/bog watershed in northern Minnesota, and were compared to the deposition in a nearby opening to determine the influence of tree canopies on Hg and DOC deposition. Twice as much Hg and seven times as much DOC was deposited in the forested watershed compared to the opening. Mass balance studies that are based on wet-only deposition in openings severely underestimate atmospheric deposition of Hg in forests. Conifer canopies are more efficient filters of airborne particulates than are deciduous canopies as indicated by much higher Hg concentrations and total deposition in throughfall and stemflow waters under conifers. Significant positive relationships existed between Hg and DOC in both throughfall (36–57% of the variation) and stemflow waters (55–88% of the variation). Hg complexation by DOC appears to be related to the contact time between precipitation and carbon sources.     

大山沟生态清洁型小流域建设的实践与探索

大山沟流域地处秦安县南部城郊,流域总面积11．88km2,是县城及周边村镇的重要水源地。经过2006～2008年间的生态清洁型小流域试点工程建设,以水资源保护为中心,以生产发展、生态清洁为目标,按照“生态修复、生态治理、生态保护”三道防线的布局思路,新增水土流失治理面积2．33km2,累计治理度达到79．2％,林草覆盖率达到44．2％,年均减少地表径流12．1万m3,减少土壤流失6．9万t。文章介绍了大山沟生态清洁型小流域建设的主要做法,并提出了有关建议。     

降水变化和人类活动对纸坊沟小流域年径流的影响

为在小流域尺度上深入认识并定量区分人类活动和降水变化对黄土高原年径流变化的影响,统计了甘肃省平凉市纸坊沟小流域49a间(1955—2003年)的年降水量和径流量实测数据。结果发现,年降水量虽无明显变化,但年径流深却呈显著减少趋势。从20世纪50年代的59.1 mm降到21世纪初的12.2mm,相对降幅高达72.4%。根据年降水量—年径流深双累积曲线,划分出了5个降水—径流关系变化时段(1955—1964,1965—1976,1977—1985,1986—1995,1996—2003年),然后以1955—1964时段为基准期,定量估算了各时段内人类活动和降水变化对年径流变化的贡献。结果表明,除在干旱时段内降水对年径流减少有明显贡献外,其他时段的径流变化主要是由人类活动引起的,并且其绝对贡献量呈逐渐增大趋势。合理规划人类活动是解决黄土高原水问题的重要途径。     

三峡库区典型小流域降雨因子对产流的影响分析

以三峡库区万州区陈家沟的2条支沟为研究对象,通过选取十几场典型次降雨和相对应的次洪水资料,首先对径流资料进行洪水场次的划分,然后采用灰色关联分析法和相关关系法分析了陈家沟2条支沟的径流深度和洪峰流量分别对降雨特征因子的响应。结果表明,(1)通过关联度排序,径流深度的主导因素是降雨量P和复合因子PI(即降雨量和平均降雨强度的复合因子);(2)对比2条邻近支沟的关联度排序,降雨特征因子对径流深度、洪峰流量的灰关联度不完全相同,但降雨特征因子对径流深度、洪峰流量的影响也具有一些共同的趋势,峰值降雨强度(I60)和降雨量的共同作用对三峡库区丘陵区的径流量的大小影响较明显,复合因子PI对洪峰流量的贡献较大。     

N Storage and Cycling in Vegetation of a Forested Wetland: Implications for Watershed N Processing

Pools and fluxes of N in wetland vegetation and soils were compared with an adjacent upland site to assess the relative importance of wetland versus upland landscapes in watershedN-retention in the Adirondack Mountains of New York (U.S.A.).The majority of N storage occurred in forest soils and wetlandpeat deposits (96 and 99% of total N in upland forests andwetlands, respectively). Annual N-uptake (49 kg N ha^-1yr^-1) was greater for wetland vegetation than that ofupland vegetation (30 kg N ha^-1 yr^-1). In the wetlandthe supply of N from mineralization (36 kg N ha^-1yr^-1) was less than N-uptake; in contrast, upland Nmineralization (76 kg N ha^-1 yr^-1) exceeded Nvegetation uptake. Annual N-storage in peat was small due to low peat accretion rates. Wetlands acted as a sink for N andstored a disproportionally high fraction (15%) of catchment Nin relation to their relatively small surface area (～4%)within the catchment.     

荫子沟小流域监测实践

荫子沟流域水土流失严重,平均侵蚀模数达7 700 t/(km2.a),强度以上侵蚀面积占水土流失面积的62.9%。2005年对流域坝系进行了监测,结果显示:在已建成的淤地坝中,只有上甘沟骨干坝产生了少量淤积,其他坝均无拦沙、输沙和蓄水情况发生;流域坝地利用及增产效益未出现;坝系工程安全性能良好。针对监测中发现的问题,提出了做好监测前的准备工作、收集整理有关资料、不可死搬教条、提高水土保持监测费用提取的比例等建议。     

Influence of Watershed Topography on the Chemistry of Stream Water in a Mountainous Area

Water, Air, & Soil Pollution - The relation among the mean slope angle of a watershed, the stream water quality, and the chemical composition of the plagioclase component of granite was...     

小流域生态经济系统优化模式研究

本文运用生态经济学的理论和方法,编制小流域综合治理开发规划,使经济建设和生态建设协调统一发展。采用多目标规划方法建立小流域生态经济系统的数学模型,进行动态模拟,可达到以较少的投资取得较大经济效益和生态效益的目标。规划的三个目标是:①建设以六个商品性生产小基地为支柱、近中远期效益兼顾的经济系统,以直接经济效益(净效益)最高为目标:②以林草植被建设为中心,恢复和建立良性生态系统,用相对价值量的方法定量计算和评价生态效益,以生态效益最大为第二目标;③以建立优化生态经济系统的投资量最少为第三目标。     

基于DEM的废弃矿山小流域地形特征分析

以北京市某废弃采石场的小流域地形为研究对象,对分辨率为0.3～7 m的栅格DEM分别进行小流域参数和地形参数的提取和分析.结果发现,利用不同分辨率DEM提取的河网形态结构有显著差异,网格尺寸7,4和3m的河网结构与2,1,0.7,0.5,0.4和0.3m的河网结构有显著差异,二者主河道位置变化明显,但流域面积、河道长度及比降、平均坡度和高程参数相差不大,而河道总长度和河网密度参数相差较大.根据分析结果确定DEM的比较适宜的分辨率为0.5m,在此基础上利用主成分分析法得出高程和坡度为主成分.对研究区设置20°,25°,30°和35°的4个不同坡度的标准径流小区,观测日降雨量、坡度、径流量和土壤侵蚀量并分析和计算它们之间关系式,计算出整个流域在不同坡度分级及不同雨量级的平均径流量和土壤侵蚀量.研究成果对于废弃矿山修复和生态重建具有参考价值.     

Ammonium Nitrogen Deposition as a Dominant Source of Nitrogen in a Forested Watershed Experiencing Acid Rain in Central Japan

To clarify nitrogen (N) sources, the overall N budget in a forested watershed in Kanagawa Prefecture, Central Japan was estimated by measuring dissolved inorganic N (DIN; NH₄ ⁺ + NO₃ ^– + NO₂ ^–) from Nov 2004 through Oct 2005. The estimated N budget (–1.43 kg N ha^–1 year^–1) showed that the N output rate (stream water N) was higher than the N input rate (bulk deposition N) in the watershed. The annual NO₂ ^– and NO₃ ^– input rates were 0.02 and 1.99 kg N ha^–1 year^–1, respectively. NH₄ ⁺ was the predominant source in this forested watershed, accounting for 71% (4.99 kg N ha^–1 year^–1) of DIN input rate. In addition, this study estimated rainfall pH, air temperature, and wind direction, which were considered as controlling factors related to the atmospheric deposition rate of NH₄ ⁺. This study showed that the rainfall NH₄ ⁺ was inversely proportional to the initial pH of the rainfall, which was calculated by adding the amount of H⁺ consumed by the dissociation process of NH_3(aq) to the measured rainfall pH. This result implies that acid rain can elevate the solubility of NH_3(g) and the dissociation capacity of NH₄ ⁺ throughout the process of precipitation. Also, this study provides strong evidence that the high NH₄ ⁺ deposition rate is mainly derived from NH_3(g) emitted from livestock wastes under the NH₃ transport condition of warm summer and favorable wind direction.     

Effects of Riparian Denitrification on Stream Nitrate-Evidence from Isotope Analysis and Extreme Nitrate Leaching during Rainfall-

The effects of riparian denitrification on stream nitrate were investigated by detailed soil water observations and isotope analysis at a small headwater catchment in an urban area near Tokyo, central Japan. In the base flow period, stream nitrate concentration (<100 µM) was comparable with that of riparian ground water which had less nitrate than unsaturated soil water. Nitrogen isotope analysis showed that the consumption of nitrate by denitrification took place in riparian ground water, suggesting that denitrification is an important process to control nitrate leaching to streams. During rainfall, the concentration of stream nitrate increased up to 400 µM, which was comparable with that of pre-event soil water. The fact that soil water nitrate directly leached to streams indicated that the riparian denitrification process did not work during rainfall because of the rapid discharge of water. A decrease of denitrification effects is a possible reason for high stream nitrate concentration during rainfall.     

东北低山丘陵区小流域水土流失防治措施的布设及效益评估——以黑龙江省宁安市和盛小流域为例

[目的]利用空间技术解析黑龙江省宁安市和盛小流域水土保持措施的布设,为低山丘陵区小流域水土流失综合治理提供技术支撑。[方法]在实地调查和现场踏查基础上,利用ArcGIS 9.3的空间分析功能,结合土地利用图和谷歌遥感影像分析小流域土地利用随地形的空间分布数量信息,并对水土流失治理效益进行评估。[结果]根据分析结果确定该流域防治措施主要包括地埂植物带、保土耕作、侵蚀沟防护林、谷坊、生态修复、五孔涵过水路面桥和涵洞等,治理效益显著。[结论]和盛小流域水土流失综合治理项目经济内部收益率大于社会折现率,经济净现值大于0,效益费用比大于1,工程采用的水土保持技术和方法符合国家和部门相关标准和技术规范,切合当地实际,可为同类地区水土流失治理借鉴。