Acidification of a Small Stream on Kureha Hill Caused by Nitrate Leached from a Forested Watershed

Nitrate leakage to a stream from a small forested watershed on Kureha Hill in Toyama Prefecture, Japan was investigated in order to assess its acid-base chemistry. Kureha Hill, located in Toyama City, receives high nitrogen loading from the atmosphere. In this area, there are several small streams characterized by a high concentration of nitrate and low ANC. Hyakumakidani, one of the most acidic streams on that hill, the average pH and ANC were 5.2 and ?8 µeq/l, respectively. The weighted average nitrate concentration, which was 125 µeq/l, increased up to 370 µeq/l during high-discharge periods caused by heavy rainfall, while ANC decreased to ?24 µeq/l at the same time. Our preliminary study using a two-stage tank model simulating the flow paths in the soil indicated that during high-discharge periods, the increased subsurface flow containing a high concentration of nitrate contributed to the increased nitrate concentration. In this watershed, the annual nitrogen budget from Aug. 1998 to Aug. 1999 showed that the loss of nitrogen exceeded the bulk nitrogen deposition, indicating that this watershed is under condition of nitrogen saturation. However, no visible attenuation has been observed.     

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。     

Transport Characteristics of Tile-Drain Sediments from an Agricultural Watershed

The use of tile drains for subsurface drainage in agricultural watersheds It as created concern for the delivery of sediment to receiving waters and potential undesirable effects on surface and subsurface water quality. In this study, transport characteristics of sediment from the drains in an agricultural watershed of the Thames River, near Kintore, Ontario, Canada were tested in a 5 m diameter. rotating circular flume located at the National Water Research Institute in Burlington. Ontario. Tile drain sediments were collected and mixed with river water at different speeds in the flume to study transport processes such as deposition, erosion and flocculation as a function of bed shear stress. During deposition and erosion experiments. water samples were collected to detennine changes in the concentrations of rations, anions and dissolved organic carbon. The results show that tile drain sediments have a tendency to flocculate when subjected to a range of shear stresses. The median diameter (D₅₀) of the floc size distribution reached a maximum value at a shear stress of 0.169 Nn² which can be considered an optimum shear stress for flocculation for this sediment. The critical shear stress at which all of the initially suspended sediment deposited to the flume bed was measured as 0.056 Nm². The pH and cation concentrations remained relatively constant during erosion and deposition experiments. Anion concentrations were more variable, most likely due to the presence of bacteria which could have also played a role in the flocculation mechanism oftile drain sediment.     

Denitrification- and Nitrate Leaching-Losses in an Intensively Cropped Watershed

In continuation of former measurements about gaseous denitrification losses, these losses together with those by nitrate leaching were measured by different methods in a field cropped during two years by wheat. Furthermore, N-uptake by the plants of fertilizer- and soil-N as well as N-im-mobilization in soils during and after the cropping periods was determined by application of highly enriched¹⁵N-labeled fertilizer. Denitrification losses determined by the N₂O release from C₂H₂–treated undisturbed soil cores agreed reasonably well with losses obtained by ¹⁵N-balance measurements. They both amounted during the cropping periods 12–15 and 6–20 kg N ha^?1, respectively. Gaseous N-losses increased mainly during wet periods when the field was barren. Denitrifying enzyme activities and soil respiration (CO₂-release) was measured throughout one year. Leaching losses of NO₃ from soil-and fertilizer-N occurred only during fall until spring. Leached NO₃^? originated mostly from mineralized soil-N and very little from previously immobilized fertilizer-N.     

莆田市木兰溪流域水土流失综合整治对策

木兰溪是莆田人民的"母亲河",木兰溪流域是莆田市的重点水土流失区,也是流域最突出的生态环境问题之一.本文针对木兰溪流域存在的主要水土流失问题,提出上游保护、中游治理、下游清淤,加强水土保持监督和监测的防治对策,具有较强的现实性和可操作性.     

森林流域界面水分传输规律研究述评

探讨森林植被对水文过程物理机制的研究不可避免地要以森林生态系统为单元 ,以森林生态系统各个界面层次对水分传输和水量转换的影响为基础来进行 ,这也正是目前界面水文学研究的焦点问题。基于此 ,综合国内外界面水文学的大量文献 ,在垂直维上从水分在森林流域内林冠层、地被物层、土壤层各主要界面层间的水量转换和运行传输规律 ,在水平维上从界面产流理论及其研究动态等方面的研究进展进行了回顾与评述 ,以此为继续加强这方面的研究工作作一铺垫     

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。     

浦城县南浦溪流域水土保持问题探析

通过对浦城县南浦溪流域的水土保持调查分析与评价,针对流域水土流失逐渐恶化问题作深入探讨,并提出了该流域水土保持的主要措施与对策。     

Water Leachates of Nitrate Nitrogen and Cations from Poultry Manure Added to an Alfisol Udalf Soil

Water, Air, & Soil Pollution - The paper summarizes results of chemical analyses of fog and rime water samples. The samples were collected at Milesovka, the Czech meteorological observatory....     

魏家沟小流域农业水土资源高效利用障碍诊断

构建了农业水土资源开发利用评价指标体系,提出了量化评价方法.采用熵技术支持下的层次分析法(AHP)确定指标权重.通过指标的"障碍度"计算,确定区域水土资源高效利用影响因子的障碍排序.研究表明魏家沟小流域水土资源利用综合评价值为61.07,其农业水土资源高效利用影响因子的障碍排序依次是水土流失治理率、植被覆盖率、水分生产率、土壤侵蚀模数等.加强水土流失治理、发展节水灌溉和提高农业综合技术水平是该流域今后应优先采取的措施.     

A New Approach for Understanding Lead Transfer in Agricultural Soil

A multi-stage particle sampling instrument and a particle counter were operated at the ground monitoring site in Fukuoka where was directly exposed to the outflow of air masses from the Asian continent during the springtime of 2005. The bulk and individual dust particles were analyzed simultaneously by ICP-MS and micro-PIXE, respectively. The ground-based observation of dust storm by the Japan Meteorological Agency and by the NOAA HYSPLIT dispersion-trajectory model indicated that dust storm was driven from the Chinese continent including dust source area. The number concentration of gigantic particles (e.g., larger than 5 μm) was measured to be 10 times higher in an Asian dust storm (hereafter called “ADS”) period than in a non-ADS period. There is an outstanding increase of mass concentration in the range of 3.5–7.7 μm in ADS event. In ADS event, soil fraction accounts 57.9–70.1% of particle mass concentration in coarse particles larger than 3.5 μm. Micro-PIXE analysis enables us to classify individual dust particles into several types. The particles with 3.5–5.1, 5.1–7.7, and 7.7–10.9 μm experienced aging processes by 60.6, 69.2, and 77.2%, respectively. On the basis of the reconstructed elemental maps by micro-PIXE analysis, the chemical transformation of dust particles was also presumed.     

Regional Distribution of Natural Stream Nitrate in Central Japan

Over 60 natural streams with forested catchments were surveyed for nitrate (NO₃ ^?) concentration in central Japan. Stream NO₃ ^? concentrations showed a clear zonal gradient with a range nearly as large as 100-fold, where their small seasonal variations (av. CV = 27%) justified respective statuses. Elevated NO₃ ^? concentrations (more than 70 µM) described a distribution of N saturation along a course of polluted air advection in the Kanto Plain. The extent of NO₃ ^? leaching from forests was not proportional to atmospheric N deposition probably because of ecosystem N retention. A dependency of NO₃ ^? level on the watershed altitude and quite constant δ¹⁵N of stream NO₃ ^? over a wide NO₃ ^? range were observed, which could be also related to this cause.     

政和县乐溪流域梯级电站建设项目水土流失及其防治

梯级水电站在建设过程中如不采取有效的水土流失防治措施,势必造成严重的水土流失。本文通过计算预测政和县乐溪流域梯级电站建设过程中造成的水土流失量,分析了可能造成的水土流失危害,提出了切实可行的防治措施。     

典型黑土区农业流域土壤侵蚀-沉积对土壤养分和酶活性的影响

研究农业流域土壤侵蚀—沉积对土壤养分和酶活性的影响可为土壤侵蚀退化评价提供重要科学依据。选择典型薄层黑土区的宾州河流域为研究区,在流域上游、中游和下游各选取2个代表性坡面,基于¹³⁷Cs示踪技术估算土壤侵蚀—沉积速率,分析流域和坡面尺度土壤侵蚀—沉积对土壤养分(有机质、全氮和速效磷)和土壤酶活性(转化酶、脲酶和碱性磷酸酶)的影响。结果表明:(1)土壤侵蚀速率在流域上游最大,分别是流域中游和下游的1.9,11.2倍;坡面尺度上土壤侵蚀速率在坡中部最大,分别是坡上部和坡下部的1.3~2.6,2.8~12.2倍。(2)在流域尺度上,土壤有机质空间分布与土壤侵蚀速率空间分布呈相反的变化趋势,土壤全氮和速效磷含量在流域下游皆大于流域中游;坡面尺度上土壤有机质、速效磷含量、转化酶、脲酶和碱性磷酸酶活性均表现为坡下部>坡中部,说明农地土壤侵蚀降低土壤养分含量和酶活性。(3)流域沉积区土壤沉积速率对土壤有机质、速效磷含量、脲酶和碱性磷酸酶活性有显著影响。(4)土壤有机质和速效磷含量对土壤脲酶和碱性磷酸酶活性有显著影响,表明土壤侵蚀—沉积引起的土壤养分再分布是造成土壤酶活性空间分异的重要原因。     

黑河上游天老池流域不同植被类型土壤物理性质异质性研究

土壤物理性质在一定程度上决定了土壤层的水文特征,而不同植被类型对于土壤物理性质的改造会导致不同区域土壤层蓄水保土功能表现出较大差异.以祁连山黑河流域上游的天老池小流域为研究区域,研究青海云杉、祁连圆柏、亚高山草甸、灌木和干草原5种植被对于土壤物理性质的影响.结果表明:(1)青海云杉林土壤的容重最小,孔隙度最大,颗粒组成主要以粉粒为主.干草原和草甸草原土壤的容重最大,孔隙度最小;同一种植被类型在不同坡位的容重和总孔隙度大小具有较好的一致性,各植被类型上中下坡位均表现出随土壤深度的增加容重增大,总孔隙度减小的趋势.(2)研究区草甸草原0-20 cm的土壤物理性质具有相似性,20-50 cm土壤层的物理性质具有较高的一致性.     

稻田土壤上控释氮肥的氮素利用率与硝态氮的淋溶损失

在稻田土壤上对水稻的高量施用氮肥常常造成硝态氮(NO3--N)淋溶损失和肥料氮利用率低下的问题。本研究采用土壤渗漏器、微区和田间小区试验,研究了15N标记控释氮肥在稻田土壤上的氮素利用率和硝态氮的淋溶损失。在两年早稻种植期间,一次性全量作基肥施用控释氮肥与尿素分二次施用的相比,两年的早稻产量分别平均提高7.7%和11.6%。在N90 kg hm-2用量下,由差值法测得的肥料氮利用率,按平均计,控释氮肥的N利用率(平均76.3%)比尿素分次施用的(平均37.4%)高出38.9%1。5N同位素法测得的控释氮肥的N利用率(平均67.1%)比尿素分次施用的(平均31.2%)高出35.9%。在早稻种植季节,施用尿素和控释氮肥的NO3--N淋失量分别为9.19 kg hm-2和6.7 kg hm-2,占施尿素N和控释氮肥氮的10.2%和7.4%。控释氮肥的氮淋失量比尿素分2次施用的降低27.1%。本研究结果表明,在稻田土壤上施用控释氮肥能减少氮的淋失量,提高氮素利用率和水稻产量。     

Leachability of Nitrate from Sandy Soil using Waste Amendments

Environmental issues associated with intensive use of nitrogenous fertilizers have generated an interest in alternative management systems. An experiment was conducted to mitigate nitrate leaching from sandy soil using different waste materials such as charcoal, manure, sawdust, wood ash, and control (no amendment). Urea was applied at the rate of 300 kg nitrogen (N) ha^?1. Nitrate was determined during six leaching events. During an incubation experiment, nitrate release was also determined in soil amended with charcoal at the rates of 0, 10, 20, and 40 t ha^?1. Urea was applied at the rates of 0, 100, 200, 400, and 1000 ppm N. Results indicated that urea application increased nitrate (NO₃) concentration in leachate. Soil amendments substantially reduced NO₃ in leachates irrespective of the type of material used. Waste amendments differed for NO₃ leaching as follows: charcoal < wood ash < sawdust < manure. Leaching of NO₃ enhanced up to the fourth leaching event and thereafter reduced significantly. Nitrate retention in soil varied among material in the order of manure > charcoal > wood ash > sawdust. Nitrate accumulation occurred in the lower layer (25–50 cm) of soil column after the leaching process. Application of charcoal retained greater NO₃ level as compared to control soil during an incubation. Enhanced urea applications also enhanced NO₃ release. This experiment suggests that waste material can be viably recycled to mitigate NO₃ concentration in water.     

Mechanisms for Translocation of Heavy Metals from Soil to Epigeal Mosses

The mechanisms for translocation of heavy metals from soil to epigeal mosses were investigated. The first mechanism was demonstrated for ¹³⁷Cs and involved the uplifting of the pollutant-containing dust from the soil, followed by the local secondary deposition on surfaces of epigeal mosses and epiphytic lichens. The second mechanism involved the diffusion of metal cations from the soil through water wetting the moss into the gametophyte. The mechanism was demonstrated by measuring the electric conductance of wetted gametophytes with single ends immersed in solutions of Cu and Na salts. In addition, the concentrations of Cu and Cd were compared in moss samples exposed to the natural soil and to the soil contaminated with the metals. The exposition to the contaminated soil resulted in the statistically significant increase of metal concentrations in the gametophytes.     

GLEAMS模型在我国东南地区模拟硝氮淋失的检验

利用我国东南亚热带地区农业小流域不同土地利用方式的硝氮渗漏淋失实测数据检验了GLEAMS(Groundwater Loading Effects of Agricultural Management Systems)模型在该地区的适用性。通过现场试验和实地调查并结合模型手册,获取模型所需的水文和营养盐参数,参考模型参数的敏感性分析结果对模型进行调试。结果表明模型对水稻田除外的其它土地利用方式的硝氮渗漏淋失模拟效果较好。水稻田渗漏模拟效果差的主要原因在于模型的水分平衡方程不能反应水稻田长期淹水的实际情况。模型模拟结果的精度可以接受,从而验证了GLEAMS模型在该流域的适用性。