宁夏中部干旱带天然草地土壤颗粒空间分布特征

以宁夏中部干旱带(清水河以东)区域天然草地为对象,采用经典统计学和地质统计学相结合的方法,对研究区内37个采样点不同土层(0～10、10～30 cm)的74个土壤样品的空间变异和分布规律进行研究,结果表明:研究区土壤砂粒含量随土层深度的增加而减少,变异性增大;各土层土壤颗粒多数具有强烈的空间相关性,主要是由结构性因素决...     

河溪近自然治理的基本模式与应用界限

河溪系统是流域管理中最基本和最重要的单元。在分析传统河溪治理的基础上,简要地介绍了河溪近自然治理的概念、发展和特征,提出了河溪近自然治理的原则,并对河溪近自然治理的基本模式进行了探讨。     

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.     

我国中南地区生态农业工程类型及其区域分布特点研究

从中南地区全国生态农业试点县建设的实际出发,将生态农业工程分成７种基本类型,统计分析了不同区域生态农业工程分布情况。结果表明：中南地区各试点县生态农业工程建设的平均项目数为９．５项,平均工程类型覆盖度为７７．９％,农田种植业为主的工程所占的比重最大,乡镇企业工程所占比重最小。并以不同类型生态农业工程所占的比重为聚类指标,将该地区１１个全国生态农业试点县分为６种类别,进而分析了不同类别自然资源和环境条件的区域分布特点,提出了各区域生态农业工程的建设重点。     

Vertical Distribution of Trace Metals in Natural Soil Horizons from Japan Part 2: Effects of Organic Components in Soil

The association of Al, Mn, Fe, Ba, Zn, Cr, Ni, Co and Pb withsoil organic matter (SOM) was investigated in three Japanesesoils. Organically bound metals were assayed by elementalanalysis of a fraction extracted with acidified hydrogenperoxide (H₂O₂) and the humic acid extracted withalkaline reagent, from soil sampled at various depths of solums.A Dystric Cambisol showed higher extractability with acidifiedH₂O₂ for most of the metals than a Humic Andosol and an Orthic Acrisol. A Humic Andosol had more metals associated with humicacid than the other two soils.Cu showed high extractability with acidified H₂O₂ andalso significant association with humic acid, while Pb showedhigh extractability with acidified H₂O₂ but itsassociation with humic acid was relatively low among the metalsinvestigated. As humic acid is highly resistant to weathering,retention of Cu with SOM may last longer than that of Pb.The binding of metals with SOM probably has contributed to theaccumulation of some metals in organic-rich shallow horizons of soil. Such metals were Zn, Cu, Ni and Pb in a Dystric Cambisol,Cu in a Humic Andosol, and Pb and Cu in an Orthic Arisol.     

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.     

天津市水体硝酸盐污染调查与空间分布研究

通过现场采样及室内分析,对天津地区的201个水样进行了硝酸盐污染现状调查研究。结果表明,各类型水体之间硝酸盐浓度存在明显差异。其中,主要水库、河流未发生硝酸盐污染。少部分排污河与农田排灌沟渠水体有硝酸盐污染倾向。地下水硝酸盐浓度较高,平均值达到15.56mg·L^-1,随着地下水深度的加深,地下水硝酸盐浓度呈明显的下降趋势。0～100m的浅层地下水硝酸盐污染状况比较严重,而大于100m的地下水尚未发生硝酸盐的污染。浅层地下水硝酸盐污染程度又与农区种植类型密切相关,大部分蔬菜种植区浅层地下水硝酸盐污染状况十分严重。运用Kriging法绘制了地下水硝酸盐浓度的空间分布图,表明天津市地下水硝酸盐污染存在明显的地区差异性。地下水硝酸盐浓度较高的区域主要分布在武清、西青、静海及宝坻等地区的蔬菜种植区。     

Sulfate and Nitrate Loads on a Forest Ecosystem in Kochi in Southwest of Japan

To assess the influence of acidic deposition on the forest ecosystem, it is necessary to evaluate the gross amount of acidic deposition. In this paper, we discuss the variation of sulfate (SO₄ ^2?) and nitrate (NO₃ ^?) loads as well as related concentration from 1991 to 1999 in the Hinoki (Chamaecyparis obtusa) plantation in Kochi, southwest Japan. The annual precipitation varied significantly from 1,700 to 3,900 mm during the study period. The annual sulfate concentration of rainfall was about 15 µmol L^?1, including about 80% non sea salt sulfate, while the annual nitrate concentration of rainfall was increased. The sulfate and nitrate concentrations of the through fall and the nitrate concentration of the stem flow were equal to or slightly higher than those of rainfall. However, the sulfate concentration of the stem flow was higher than that of rainfall, 21 to 55 µmol L^?1. The sulfate and nitrate loads of rainfall were measured to be 27 to 46 and 14 to 43 mmol m^?2 y^?1, respectively. The sulfate and nitrate loads of the through fall were the same or slightly higher than those of rainfall. In contrast, the sulfate and nitrate loads of the stem flow were less than those of rainfall. Combined sulfate loads of the through fall and the stem flow reached about 1.5 times that of the sulfate load of rainfall.     

河道公路绿化植物毛白杨对重金属元素的吸收与分布

对保定市河道公路不同年龄毛白杨Pb,Cd,Cu,Zn,Cr,Ni含量进行了研究,并测定了毛白杨根际土壤重金属含量.结果表明:土壤Cd污染严重.整体上3 a生的毛白杨吸收重金属的能力大于5 a生和10 a生的毛白杨,并且重金属含量呈现Zn>Cu>CA>Cr>Pb>Ni的规律.毛白杨吸收的重金属表现为叶、根部和树皮较大,枝和树干较小的基本趋势.Pb,Cr,Zn,Ni重金属转移能力随着年龄的增加而降低.Cd的转移系数随着年龄的增加呈现增加的趋势.年龄较小的毛白杨具有较高的富集系数.毛白杨富集Pb,Cu,Zn,Cr,Ni的能力较差,但具有较强的Cd富集能力.Pb,Cd,Cu,Zn富集系数叶部较大,但Cr,Ni富集系数树皮较大.     

Mercury Cycling in an Urbanized Watershed: The Influence of Wind Distribution and Regional Subwatershed Geometry in Central Indiana,USA

The global cycle of mercury (Hg) is reasonably well-understood, as are some of the natural and anthropogenic sources of Hg to the atmosphere. Less well understood are the regional and local characteristics of Hg deposition and subsequent watershed-scale transport, important parameters for assessing human risk to various avenues of Hg exposure. This study employed a two-part strategy for understanding coupled deposition and transport processes in central Indiana (USA), including Indianapolis, a typical large city with multiple coal-fired electric utilities and other Hg emission sources. A spatial analysis of Hg concentrations in surface soils revealed elevated Hg proximal to many of the large emission sources, with a distribution aligned along a southwest-northeast axis corresponding to the mean wind direction in this region. This soil distribution suggests some local depositional impact from local utilities, with wind modification affecting the regional pattern. Post-depositional transport of Hg was assessed using a series of streambank sampling arrays as the White River and various tributaries travelled through the urban core of Indianapolis. Streambank sediments had peak Hg concentrations in the urban core, where several local sources are present and where a number of subwatersheds join the main trunk of the White River, suggesting local emission and/or rapid Hg transport from urban subwatersheds due to their relatively high proportion of impervious surfaces. High Hg values persist in White River sediments into rural areas tens of kilometers south of Indianapolis, raising concerns for anglers collecting fish in this apparently “pristine” environment.     

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.     

河溪近自然治理评价指标体系探讨以及应用

河溪近自然治理从河溪生态系统的生态特征、地貌特征和水体特征三个方面入手,针对我国特殊的经济情况和复杂的水域特点,提出了由11个因子组成的河溪近自然评价指标体系,包括：（1）河流的平面形态：（2）河流的横断面形态：⑶河流的水深：（4）水体宽度：（5）岸坡的结构：（6）水流的流速：（7）缓冲带植被宽：⑻水体与河床的接触情况：（9）河道粗木质情况：（10）水质：（11）底栖大型动物。再根据评价结果将河溪生态系统健康划分为四个等级,并对北京市怀柔区的典型河溪——怀九河进行河溪近自然治理评价,发现其处于河溪受到微小的人类活动的侵扰阶段,需要利用河溪近自然治理加以调控。     

Acidity neutralization mechanism in a forested watershed in Central Japan

The contributions of cation exchange and mineral weathering to the neutralization of acidity in the Jingahata watershed in central Japan were estimated through a laboratory weathering experiment and runoff chemistry measurements. The laboratory experiment was conducted in a stirred-flow reactor for a whole soil sample collected from the C horizon in the watershed. The concentration ratios of base cations (Ca²⁺, Mg²⁺, K⁺ and Na⁺) to Si (BC/Si) released during the steady-state stage of the laboratory experiment were in good agreement with the ratios of the net flux of base cations to the flux of Si in the streamwater (BC _{N ET}/Si _L).This result suggests that the acidity in the watershed is neutralized primarily by mineral weathering without causing a net loss of base cations from exchange sites. The alkalinity/acidity balance estimated for the watershed shows that the total weathering rate of base cations is approximately 3.26 keq ha^?1 yr^?1. Weathering of plagioclase (An₄₁) contributes 83% of the total weathering rate. The dominant acidity source is CO₂ released within the soil horizons, accounting for roughly 85% of the total acidity flux (3.20 keq ha^?1 yr^?1). This high internal production of acidity suppresses the relative importance of atmospheric acidity inputs (0.3 keq ha^?1 yr^?1).     

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.     

Geochemical Distribution of Selected Heavy Metals in Stream Sediments Affected by Tannery Activities

Bayesian regularized back-propagation neural network (BRBPNN) was developed for trend analysis, acidity and chemical composition of precipitation in North Carolina using precipitation chemistry data in NADP. This study included two BRBPNN application problems: (i) the relationship between precipitation acidity (pH) and other ions (NH₄ ⁺, NO₃ ^?, SO₄ ^2?, Ca²⁺, Mg²⁺, K⁺, Cl^? and Na⁺) was performed by BRBPNN and the achieved optimal network structure was 8-15-1. Then the relative importance index, obtained through the sum of square weights between each input neuron and the hidden layer of BRBPNN(8-15-1), indicated that the ions' contribution to the acidity declined in the order of NH₄ ⁺ > SO₄ ^2? > NO₃ ^?; and (ii) investigations were also carried out using BRBPNN with respect to temporal variation of monthly mean NH₄ ⁺, SO₄ ^2? and NO₃ ^? concentrations and their optimal architectures for the 1990–2003 data were 4-6-1, 4-6-1 and 4-4-1, respectively. All the estimated results of the optimal BRBPNNs showed that the relationship between the acidity and other ions or that between NH₄ ⁺, SO₄ ^2?, NO₃ ^? concentrations with regard to precipitation amount and time variable was obviously nonlinear, since in contrast to multiple linear regression (MLR), BRBPNN was clearly better with less error in prediction and of higher correlation coefficients. Meanwhile, results also exhibited that BRBPNN was of automated regularization parameter selection capability and may ensure the excellent fitting and robustness. Thus, this study laid the foundation for the application of BRBPNN in the analysis of acid precipitation.     

Geochemical Comparison of Stream Water, Rain Water, and Watershed Geology in Central Korea

A hilly to mountainous watershed in Chonju in central Korea does not receive acid rain (average pH: 6.2); however, the stream water in the granite watershed is slightly acidic (6.4–6.7) and contains a low concentration of Ca compared to the stream water in sedimentary and volcanic rock watersheds (6.8–7.6). Although the concentrations of Ca and Sr and the ⁸⁷Sr/⁸⁶Sr ratio in the stream water change in accordance with the watershed geology, the stream ⁸⁷Sr/⁸⁶Sr ratios are closer to the ⁸⁷Sr/⁸⁶Sr ratios of rain than to those of the substrate rocks, suggesting the selective but sluggish weathering of Ca-containing minerals neutralizes acid. The concentrations of trace metals (As, Cr, Cu, Mo, Ni, Pb) in the water are lower than those in rain and less dependent on the watershed geology, indicating that they originated dominantly from the atmosphere. This result is consistent with the stream water having Pb isotope ratios close to that of rain but distinct from that of the rocks. We assume that the soil pool of exchangeable ions dominantly contains atmospherically derived heavy metals, which are subsequently discharged into streams. It is likely that the poor acid-neutralizing capacity of granite makes the aquatic systems in the granite watershed in Chonju sensitive to atmospheric acidification.     

Corn Monoculture Yield Response to Fertilization and Nitrate Nitrogen Distribution

The objectives of this study were to determine the effects of fertilization system, nitrate (NO₃)– nitrogen (N) distribution along soil profile, and their interaction on corn yield. The study was conducted at the experimental field of Institute of Field and Vegetable Crops in Novi Sad (Serbia) during 2001–2004. Corn monoculture included four fertilization variants: control (Ø), nitrogen–phosphorus–potassium (NPK) mineral fertilizers, mineral fertilizer + corn stalks (NPK + S), and mineral fertilizers + manure (NPK + M). The greatest yield was found in the variant NPK + M (9.25 t ha^?1). Path coefficients showed that greatest direct positive effects on corn yield were exhibited by NO₃-N levels at soil depths of 60–90 cm and 30–60 cm. The path analysis showed that winter precipitation (WP) had a direct negative effect on yield performance. However, the effect of the downward movement of NO₃-N from the topsoil to deeper soil layers of WP on yield was positive.     

Long-term Persistence of Stream Nitrate Concentrations (Memory Effect) Inferred from Spectral Analysis and Detrended Fluctuation Analysis

Previous research in agricultural catchments showed that past inputs of nitrate continue to influence present observations and future characteristics of nitrate concentrations in stream water for a long period of time. This persistence manifests itself as a “memory effect” with a prolonged response of stream water nitrate levels to reductions of nitrate inputs on the catchment scale. The question we attempt to resolve is whether such a memory effect also exists in mountainous catchments with a snowmelt-dominated runoff regime. We analyzed long-term records (∼20 years) of nitrate-nitrogen concentrations measured in stream at three stations on the upper Váh River (Slovakia). Applying spectral analysis and detrended fluctuation analysis, we found a varying degree of persistence between the three analyzed sites. With increasing catchment area, the fluctuation scaling exponents generally increased from 0.77 to 0.93 (fluctuation exponents above 0.5 are usually considered as a proof of persistence while values close to 0.5 indicate “white” uncorrelated noise). The nitrate-nitrogen signals temporally scaled as a power-low function of frequency (1/f noise) with a strong annual seasonality. This increase in persistence might be attributable to the catchment areas upstream the sampling sites. These results have important implications for water quality management. In areas where reduction of nitrate in surface waters is imposed by legislation and regulatory measures, two catchments with different persistence properties may not respond to the same reduction of sources of nitrogen at the same rate.     

区域尺度的城市灰尘重金属分布

根据47个城市的灰尘重金属Cd,Cr,Cu,Hg,Pb,Zn,Ni的监测资料,分析了重金属在区域尺度的分布规律。结果表明,灰尘重金属浓度分为5个等级,并在1～4倍的标准差内变化,在空间上呈西高东低,南高北低,自西南向东北减少的特征。各地区灰尘重金属含量依次呈：西南〉西北〉华南〉华东〉华北〉华中〉东北,且某些元素的空间分布还与我国阶梯地势相吻合。自然背景和人类活动都是重要的影响因素,前者对华北、华中和东北地区影响较大,后者对西北、西南和华南地区作用程度较高。另外,各重金属元素受人类活动的作用强度也不同,受影响强度依次呈：Cd〉Hg〉Zn〉Pb〉Cu〉Ni〉Cr。