Elemental hydrochemistry assessment on its variation and quality status in Langat River, Western Peninsular Malaysia

This paper discusses the hydrochemistry variation and its quality status in Langat River, based on the chemistry of major ions, metal concentrations and suitability for drinking purposes. Water samples were collected from 30 different stations to assess their hydrochemical characteristics. The physico-chemical parameters selected were temperature, electrical conductivity, total dissolved solids (TDS), salinity, dissolved oxygen , pH, redox potential, HCO₃, Cl, SO₄, NO₃, Ca, Na, K, Mg, ²⁷Al, ¹³⁸Ba, ⁹Be, ¹¹¹Cd, ⁵⁹Co, ⁶³Cu, ⁵²Cr, ⁵⁷Fe, ⁵⁵Mn, ⁶⁰Ni, ²⁰⁸Pb, ⁸⁰Se and ⁶⁶Zn to investigate the variation of the constituents in the river water. Most of the parameters comply with the Drinking Water Quality Standard of the World Health Organization and the Malaysian National Standard for Drinking Water Quality by the Malaysia Ministry of Health except for EC, TDS, Cl, HCO₃, SO₄, Na, Mg, Al, Fe and Se. The results show that the Langat River is unsuitable for drinking purposes directly without treatment.     

Phytoplankton community composition and size distribution in the Langat River estuary,Malaysia

Phytoplankton patchiness, as expressed by community composition and size distribution, during the rainy season in the Langat River estuary (Malaysia) is described. Four sites in the estuary were sampled on two different occasions. The sampling area covered a stretch of the river from upstream to downstream of aquaculture activities (shrimp farms). Water samples from a shrimp farm outlet were also analyzed for nutrient and phytoplankton content. Differences in community structure between stations were found by means of multivariate procedures. Genera composition and total biomass were related to environmental factors, revealing salinity, light, and nutrients as important explaining factors. Elevated phytoplankton biomass and total phosphorus concentration, as well as lower inorganic nitrogen: phosphorus ratios, were found downstream of the shrimp farming activities. The size distribution spectrum of the phytoplankton population downstream of the shrimp farms was significantly different from that at the other stations but not different than that found in the sampled effluent from the shrimp farms, where phytoplankton biomass was also high. Twenty-two of the 24 recorded genera from the shrimp farm outlet were also found downstream of the farming activities. A number of different environmental factors potentially alter conditions for phytoplankton in the lower reaches of the estuary as compared to the upper regions. A cause and effect relationship explaining the differences noted between the upper and lower reaches of the estuary cannot be established. This study suggests that nutrient enrichment from the shrimp farming activities is of a magnitude that may contribute to the phytoplankton community changes observed in the lower reaches of the estuary.     

Identification of sources affecting water chemistry in the Nakdong River,South Korea

The sources impacting the water chemistry of the Nakdong River (NR) in South Korea were investigated in order to examine the pollution mechanism including the fate and transport of the contaminants and how much such sources may affect its main channel of water resource. Water samples were collected between 2007 and 2008 from 8 sites along a 510 km downstream transect of the NR, and chemical and isotopic compositions of the water samples were evaluated to identify natural and anthropogenic sources contributing to the water chemistry of the NR. The results showed that the major ion concentrations were mainly controlled by chemical weathering that occurred in the watershed, in which a silicate weathering is more dominant than a carbonate weathering. The ⁸⁷Sr/⁸⁶Sr ratios of the water samples were in a range from 0.71043 to 0.71520 within those of the Mesozoic volcanogenic sedimentary rocks long developed in the watershed, thereby supporting the fact that the water chemistry is governed by a chemical weathering. The δ³⁴S values varied in a narrow range of 1.8–3.1‰, regardless of spatial and seasonal variations. Mass balance calculations indicated that the contributions of chemical weathering and anthropogenic sources during summer time increased along a downstream transect, from 67.3 ± 1.3 to 73.6 ± 0.5% and from 6.0 to 15.7%, respectively. In contrast, the contribution of chemical weathering during winter time decreased from 82.7 ± 0.8 to 72.5 ± 0.3%, while anthropogenic contribution increased up to 22.2%. These results indicated that the water chemistry of the NR was mainly caused by a chemical weathering, followed by anthropogenic inputs and rainwater. This study will provide baseline information for comparing the water quality issue before and after the implementation of the Four Rivers Restoration Project of South Korea.     

Seasonal and spatial variations in water chemistry and nitrate sources in six major Korean rivers

Seasonal and spatial variations in water chemistry and contaminant sources were investigated in six major rivers in South Korea that vary widely in drainage area and length. The dissolved-load content of the rivers varied seasonally, and some dissolved ions such as Cl^? and NO₃ ^? showed large spatial differences in all of the rivers. The water type changed from Ca–HCO₃ in the upper reaches to Na–Cl–NO₃ in the lower reaches, indicating anthropogenic contamination in the lower reaches. Compared with two relatively pristine rivers (the Sumjin and Mankyung rivers), the other four rivers, which flow through agricultural and urban areas, registered much higher Cl^? and NO₃ ^? concentrations. Statistical analysis showed that seasonal and spatial variations in water chemistry occurred in all the rivers. The nitrogen and oxygen isotopes of dissolved nitrate indicated that the rivers flowing through urban and agricultural areas were significantly affected by manure, sewage, or both.     

Comparison of recorded rainfall with quantitative precipitation forecast in a rainfall-runoff simulation for the Langat River Basin, Malaysia

Observed rainfall is used for runoff modeling in flood forecasting where possible, however in cases where the response time of the watershed is too short for flood warning activities, a deterministic quantitative precipitation forecast (QPF) can be used. This is based on a limited-area meteorological model and can provide a forecasting horizon in the order of six hours or less. This study applies the results of a previously developed QPF based on a 1D cloud model using hourly NOAA-AVHRR (Advanced Very High Resolution Radiometer) and GMS (Geostationary Meteorological Satellite) datasets. Rainfall intensity values in the range of 3–12 mm/hr were extracted from these datasets based on the relation between cloud top temperature (CTT), cloud reflectance (CTR) and cloud height (CTH) using defined thresholds. The QPF, prepared for the rainstorm event of 27 September to 8 October 2000 was tested for rainfall runoff on the Langat River Basin, Malaysia, using a suitable NAM rainfall-runoff model. The response of the basin both to the rainfall-runoff simulation using the QPF estimate and the recorded observed rainfall is compared here, based on their corresponding discharge hydrographs. The comparison of the QPF and recorded rainfall showed R² = 0.9028 for the entire basin. The runoff hydrograph for the recorded rainfall in the Kajang sub-catchment showed R² = 0.9263 between the observed and the simulated, while that of the QPF rainfall was R² = 0.819. This similarity in runoff suggests there is a high level of accuracy shown in the improved QPF, and that significant improvement of flood forecasting can be achieved through ‘Nowcasting’, thus increasing the response time for flood early warnings.     

Characteristics and sources of microplastic pollution in the water and sediments of the Jinjiang River Basin,Fujian Province,China

Microplastic pollution is widely distributed from surface water to sediments to groundwater vertically and from land to the ocean horizontally. This study collected samples from surface water, groundwater, and sediments from upper to lower reaches and then to the estuary in 16 typical areas in the Jinjiang River Basin, Fujian Province, China. Afterward, it determined the components and abundance of the microplastics and analyzed the possible microplastic sources through principal component analysis (PCA). As a result, seven main components of microplastics were detected, i.e., polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polyformaldehyde (POM), nylon 6 (PA6), and polystyrene (PS). Among them, PE and PP were found to have the highest proportion in the surface water and sediments and in the groundwater, respectively. The surface water, groundwater, and sediments had average microplastic abundance of 1.6 n/L, 2.7 n/L and 33.8 n/kg, respectively. The microplastics in the sediments had the largest particle size, while those in the groundwater had the smallest particle size. Compared with water bodies and sediments in other areas, those in the study area generally have medium-low-level microplastic abundance. Three pollution sources were determined according to PCA, i.e., the dominant agriculture-forestry-fishery source, domestic wastewater, and industrial production. This study can provide a scientific basis for the control of microplastics in rivers.©2022 China Geology Editorial Office.     

Assessment of water quality and identification of pollution sources of three lakes in Kashmir, India, using multivariate analysis

Multivariate statistical techniques, such as cluster analysis, principal component analysis (PCA) and factor analysis (FA) were applied to evaluate and interpret the water quality data set for 13 parameters at 10 different sites of the three lakes in Kashmir, India. Physicochemical parameters varied significantly (p?<?0.05) among the sampling sites. Hierarchical cluster analysis grouped 10 sampling sites into three clusters of less polluted, moderately polluted and highly polluted sites, based on similarity of water quality characteristics. FA/PCA applied to data sets resulted in three principal components accounting for a cumulative variance of 69.84, 65.05 and 71.76% for Anchar Lake, Khushalsar Lake and Dal Lake, respectively. Factor analysis obtained from principal components (PCs) indicated that factors responsible for accelerated eutrophication of the three lakes are domestic waste waters, agricultural runoff and to some extent catchment geology. This study assesses water quality of three lakes through multivariate statistical analysis of data sets for effective management of these lakes.     

Surface water chemistry and nitrate pollution in Shimabara,Nagasaki, Japan

Groundwater is a finite resource that is threatened by pollution all over the world. Shimabara City, Nagasaki, Japan, uses groundwater for its main water supply. During recent years, the city has experienced severe nitrate pollution in its groundwater. For better understanding of origin and impact of the pollution, chemical effects and surface–groundwater interactions need to be examined. For this purpose, we developed a methodology that builds on joint geochemical analyses and advanced statistical treatment. Water samples were collected at 42 sampling points in Shimabara including a part of Unzen City. Spatial distribution of water chemistry constituents was assessed by describing Stiff and Piper diagrams using major ions concentrations. The nitrate (NO₃?+?NO₂–N) concentration in 45% of water samples exceeded permissible Japanese drinking level of 10 mg L^??1. Most of the samples showed Ca–HCO₃ or Ca–(NO₃?+?SO₄) water types. Some samples were classified into characteristic water types such as Na–Cl, (Na?+?K)–HCO₃, (Na?+?K)–(SO₄?+?NO₃), and Ca–Cl. Thus, results indicated salt water intrusion from the sea and anthropogenic pollution. At the upstream of Nishi River, although water chemistry was characterized as Ca–HCO₃, ion concentrations were higher than those of other rivers. This is probably an effect of disinfection in livestock farming using slaked lime. Positive correlation between NO₃^? and SO₄^2?, Mg²⁺, Ca²⁺, Na⁺, K⁺, and Cl^? (r?=?0.32–0.64) is evidence that nitrate pollution sources are chemical fertilizers and livestock waste. Principal component analysis showed that chemistry of water samples can be explained by three main components (PCs). PC1 depicts general ion concentration. PC2 and PC3 share influence from chemical fertilizer and livestock waste. Cluster analyses grouped water samples into four main clusters. One of these is the general river chemistry mainly affected by PC1. The others reflect anthropogenic activities and are identified by the combination of the three PCs.     

Factorial and indicator kriging methods using a geographic information system to delineate spatial variation and pollution sources of soil heavy metals

This study uses factorial and indicator kriging methods with a geographic information system (GIS), to overlay and delineate the variation and pollution sources of soil heavy metals in fields in the north of Changhua County, Taiwan. Accordingly, the spatial variation and pollution probability patterns of soil cadmium, chromium and copper are estimated to support further environmental monitoring, remediation and planning. The overlay maps of industrial plants, irrigation channels and kriging estimates, constitute a GIS. This reveals that the short- and long-range variations and soil pollution by Cd, Cr and Cu strongly corresponded to the locations of irrigation systems and industrial plants in the area of study. The maps also verify most locations of suspected pollution sources from the GIS database. Moreover, the probability spatial patterns estimated by indicator kriging, based on the pollution thresholds of Cd, Cr and Cu, were also highly correlated with irrigation channels and industrial plants. The GIS, with factorial and indicator kriging under different combinations of variations and pollution probabilities of soil Cd, Cr and Cu, provide alternative scenarios for delineating the areas that contain high variation and high pollution probability of these heavy metals, to enable decision makers to identify pollution sources, and to further investigate and remedy soil pollution.     

Assessment of pollution status of Dalianhu water sources in Shanghai,China and its pollution biological characteristics

The present study was undertaken aiming to assess the water quality state of different parts (i.e. external river, aquaculture ponds, lake area, water forests, internal river and swampland) of Dalianhu water sources in Shanghai (China), by investigating the community structure characteristics of zooplankton and benthos along with some water quality parameters (TN, TP, COD, etc.). Some diversity indices were calculated, including Shannon–Wiener index (H) for both zooplankton and benthos, Margalef’s diversity index (D) for zooplankton and Goodnight modified index (G) and Biological pollution index (BPI) for benthos. The obtained results shows that in Dalianhu water sources, the Shannon–Wiener index of zooplankton (H _z) is 0.3–1.83, the Margalef’s diversity index of zooplankton (D) is 1.0–10.4. The Shannon–Wiener index of benthos (H _b) is 0.81–1.26, the Goodnight modified index of benthos (G) is 0.30–0.88, the Biological pollution index (BPI) is 1.1. These findings determine the water quality in Dalianhu water sources which belong to the moderate pollution. By comprehensive analysis together with zooplankton, benthos indices and water physicochemical parameters, the pollution level of Dalianhu water sources is in turn water forest, inner river, aquaculture ponds, external river and lake area, showing that the pollution of the Dalianhu water sources is mainly internal. It was suggested that the further work departments should be carried out to strengthen the necessary consolidate management and ecological repair.     

Tracing the sources of nitrate in karstic groundwater in Zunyi,Southwest China: a combined nitrogen isotope and water chemistry approach

Nitrate (NO₃ ⁻) is major pollutant in groundwater worldwide. Karst aquifers are particularly vulnerable to nitrate contamination from anthropogenic sources due to the rapid movement of water in their conduit networks. In this study, the isotopic compositions (δ¹⁵N–NO₃ ⁻, δ¹⁵N–NH₄ ⁺) and chemical compositions(e.g., NO₃ ⁻, NH₄ ⁺, NO₂ ⁻, K⁺) were measured in groundwater in the Zunyi area of Southwest China during summer and winter to identify the primary sources of contamination and characterize the processes affecting nitrate in the groundwater. It was found that nitrate was the dominant species of nitrogen in most of the water samples. In addition, the δ¹⁵N–NO₃ ⁻ values of water samples collected in summer were lower than those collected in winter, suggesting that the groundwater received a significant contribution of NO₃ ⁻ from agricultural fertilizer during the summer. Furthermore, the spatial variation in the concentration of nitrate and the δ¹⁵N–NO₃ ⁻ value indicated that some of the urban groundwater was contaminated with pollution from point sources. In addition, the distribution of δ¹⁵N–NO₃ ⁻ values and the relationship between ions in the groundwater indicated that synthetic and organic fertilizers (cattle manure) were the two primary sources of nitrate in the study area, except in a few cases where the water had been contaminated by urban anthropogenic inputs. Finally, the temporal and spatial variation of the water chemistry and isotopic data indicated that denitrification has no significant effect on the nitrogen isotopic values in Zunyi groundwater.     

珠江河口水环境时空变异对河口生态系统的影响

分析近20年来珠江河口水环境变异的特征,探讨珠江河口水环境与水生物相互联系和相互作用的关系。结果表明,珠江河口形态、地貌、水文情势和入河污染物等变异改变了珠江河口水生物的栖息条件,削弱了河口生态系统的自动调节修复能力和稳定性,对河口生态系统的物质循环、能量流动和发育演化平衡构成了重大影响。     

济南市大气降尘地球化学特征及污染端元研究

在济南市城区对大气降尘及不同污染端元样品进行采集,系统分析了大气降尘和污染端元元素含量特征,并对大气降尘空间分布及污染来源进行研究。结果表明:不同污染端元中元素含量差别明显,燃煤尘中As、Cd、F、Pb是汽车尾气尘的3倍以上,是交通尘、冶炼尘、建筑尘等其他端元尘的1.26~2.35倍,对环境影响较大;汽车尾气尘中Cr、Ni、S、Zn含量最高,冶炼尘中Co、Ni、Pb、F含量偏高,而建筑尘中多数元素含量为所有端元尘中最低。与土壤背景值相比,济南市大气降尘中Cr、Cu、Pb、Zn、Cd、F、S富集程度较高,受到不同程度人为污染;相关分析和因子分析结果表明,Cd、Cu、Hg、Pb、As主要来源于企业燃煤,大气降尘中这些元素高含量区与热电厂、冶炼厂、化工厂等燃煤污染源空间分布相一致;F、S可能与汽车尾气排放有关,而As、Cr主源于交通污染,这3种污染源是济南市大气降尘污染的主要来源,对降尘的贡献约占60.42%。研究表明,工业燃煤排放已逐渐代替汽车尾气成为大气降尘中Pb元素的主要来源。     

Applying spatial regression to evaluate risk factors for microbiological contamination of urban groundwater sources in Juba,South Sudan

This study developed methodology for statistically assessing groundwater contamination mechanisms. It focused on microbial water pollution in low-income regions. Risk factors for faecal contamination of groundwater-fed drinking-water sources were evaluated in a case study in Juba, South Sudan. The study was based on counts of thermotolerant coliforms in water samples from 129 sources, collected by the humanitarian aid organisation Médecins Sans Frontières in 2010. The factors included hydrogeological settings, land use and socio-economic characteristics. The results showed that the residuals of a conventional probit regression model had a significant positive spatial autocorrelation (Moran’s I?=?3.05, I-stat?=?9.28); therefore, a spatial model was developed that had better goodness-of-fit to the observations. The most significant factor in this model (p-value 0.005) was the distance from a water source to the nearest Tukul area, an area with informal settlements that lack sanitation services. It is thus recommended that future remediation and monitoring efforts in the city be concentrated in such low-income regions. The spatial model differed from the conventional approach: in contrast with the latter case, lowland topography was not significant at the 5% level, as the p-value was 0.074 in the spatial model and 0.040 in the traditional model. This study showed that statistical risk-factor assessments of groundwater contamination need to consider spatial interactions when the water sources are located close to each other. Future studies might further investigate the cut-off distance that reflects spatial autocorrelation. Particularly, these results advise research on urban groundwater quality.     

Using regression model to identify and evaluate heavy metal pollution sources in an open pit coal mine area,Eastern Junggar,China

This study aims at identifying multi-source heavy metal pollution from natural and anthropogenic sources using a regression model, principal component analysis, and five different indices (geo-accumulation index (I _geo), the modified degree of contamination, pollution load index (PLI), enrichment factor, and ecological risk factor. Results revealed that: (1) although the average concentrations of soil heavy metals (Cu, Cr, Pb, Hg, As, Zn) were generally low, Hg, As, and Cr concentrations exceeded national standard values by approximately 0.91, 1.84, and 0.91 times with maximum concentrations up to 0.41, 78.6, and 175.2 μg/g, respectively; (2) PLI results showed that the industrial park and Wucaiwan open coal mining area were the most polluted (PLI of 1.98, 1.71). The potential ecological hazards index indicated that the E _i ^r of three heavy metals (Cu, Hg, As) in the soil were relatively high, presenting potential ecological risk factors of 74.89, 16.71, 4.15%, respectively; (3) stepwise regression model and principal component analysis suggest that Cu and Zn were primarily effected by the natural geological condition and atmospheric dust fall. Cr, Hg, Pb are mainly derived from anthropogenic sources, particularly coal mining activities and industrial sources. Results of this research have some significant implications for heavy metal pollution prevention and the sustainable development of the economy and ecology of arid regions in China.     

地下水“三氮”污染来源及其识别方法研究进展

近年来随着人类活动增加、工业废水的大量排放以及农业氮肥过量施用,使得地下水中“三氮”（即硝酸盐氮、氨氮、亚硝酸盐氮）污染问题愈加严重,对人体带来潜在健康风险。通过地下水“三氮”污染分布及来源作出解析,对于开展污染源头防控具有重要的现实意义。本文以黑龙江省海伦地区浅层地下水作为研究对象,采用气相分子吸收光谱法（GMA）及电感耦合等离子体质谱法（ICP-MS）测定了地下水中“三氮”及其他金属元素的检出情况,应用内梅罗综合污染指数法对地下水中“三氮”划分水质污染等级,综合运用Pearson相关性分析、正定矩阵因子分析法（PMF）等方法,识别和定量解析污染源及贡献。结果表明：①研究区地下水中硝酸盐氮含量范围在0.021～123.05mg/L之间,平均浓度为15.27mg/L;氨氮含量范围在 ND～3.91mg/L之间,平均浓度为0.33mg/L;亚硝酸盐含量范围在ND～0.65mg/L之间。与《地下水质量标准》（GB/T 14848—2017）Ⅲ类水指标对比,硝酸盐氮超标率为20.0%,氨氮超标率为12.5%。②内梅罗综合污染指数评价结果表明,研究区地下水水质污染等级一级至三级中度污染地下水占比为92.5%,整体上水质“三氮”污染较轻。海伦地区“三氮”空间分布整体上呈现出氨氮、硝酸盐氮流域中心区近端含量高、远端含量低的趋势。硝酸盐氮及氨氮超标点主要分布在研究区中部的人类活动密集区域。亚硝酸盐氮在空间分布上沿海伦河流向呈现出北高南低的趋势。③正定矩阵因子分析模型（PMF）源解析结果表明,硝酸盐氮主要来源于生活与工业复合源;亚硝酸盐氮主要来源于自然源;氨氮主要来源于生活与农业复合源。与中南部长三角武进地区太湖平原、西南部成都平原及东南部广花盆地地下水相比,海伦地区氨氮含量偏低,硝酸盐氮均值则均高于中南部地区。“三氮”的源解析结果呼应了东三省尤其是黑龙江部分地区“三氮”含量较高的分布特征。海伦地区地下水“三氮”污染程度整体上相对较轻,人类活动对地下水中“三氮”分布的影响较大。

     

Heavy metals pollution and the identification of their sources in soil over Xiaoqinling gold-mining region,Shaanxi, China

In order to determine the characteristics of heavy metals’ pollution and identify their sources in the soil over the Xiaoqinling gold-mining region, Shaanxi, China, 133 soil samples were collected over the region, one sample was from a close point as background, and concentrations of Hg, Pb, Cu, and As in all samples were analyzed. Results indicated that the soil was polluted by these heavy metals, as their concentrations in the soil over the studied region were higher than that in the background zone. In addition, the result indicated that these metals had their specific spatial characteristics. Among the samples, those with higher concentrations of Hg, Pb, and Cu were mainly collected from the Shuangqiao river alluvial terrace area, the loess ravine tableland, and the piedmont alluvial–pluvial inclined tableland, which are the areas of gold-mining activities. Meanwhile, the samples with higher concentrations of As were distributed over the loess ravine tableland around Tongguan County, where agricultural activities were conducted intensively. Furthermore, the sources for all the heavy metals Hg, Pb, Cu, and As in the soil over each landscape were determined through analyzing the concentration correlation of these metals and comparing the maps of metal concentration distribution and land-use types. In Yellow river–Weihe river alluvial plain area, these heavy metals were mainly from agricultural activities. In the other landscapes, As was also mainly from agricultural activities; the other metals were contrarily from the gold-related activities. Interestingly, the correlation coefficients of As concentrations with Hg, Pb or Cu concentrations were positive in the samples from Yellow river–Weihe river alluvial plain area, and on the contrary, they were negative in the samples from the other landscapes. This result showed that the correlation can be used as an index to indicate properly the effect of the gold-related or agricultural activities on the heavy metals in the soil and identify their main sources over each landscape. As human activities resulted in the site-specific characteristics in the concentrations and sources of the heavy metals in each landscape, site-specific control strategies should be selected intensively to remedy landscape soil pollution. In Yellow river–Weihe river plain area, effective control strategies should be aimed at remedying As pollution caused by agricultural activities; in the other landscapes, Hg, Pb and Cu pollution caused by gold-mining activities should be considered.     

Response of groundwater chemistry to water deliveries in the lower reaches of Tarim River,Northwest China

In this paper, we analysed the monitored data from nine groundwater-monitoring transects in the lower reaches of Tarim River during the five times of stream water deliveries to the river transect where the stream flow ceased. The results showed that the groundwater depth in the lower reaches of Tarim River rose from −9.30 m before the conveyances to −8.17 and −6.50 m after the first and second conveyances, −5.81 and −6.00 m after the third and fourth the conveyance, and −4.73 m after the fifth. The horizontal extent of groundwater recharge was gradually enlarged along both sides of the channel of conveyance, i.e., from 250 m in width after the first conveyance to 1,050 m away from the channel after the fourth delivery. With the rising groundwater level, the concentrations of major anions Cl⁻, SO₄²⁻ and cations Ca²⁺, Mg²⁺, Na⁺, as well as total dissolved solids (TDS) in groundwater underwent a significant change. The spatial variations in groundwater chemistry indicated that the groundwater chemistry at the transect near Daxihaizi Reservoir changed earlier than that farther from it. In the same transect, the chemical variations were earlier in the monitoring well close to watercourse than that farther away from the stream. In general, the concentration of the major ions and TDS at each monitoring well increased remarkably when the water delivery started, and decreased with the continued water delivery, and then increased once again at the end of the study period. Hence, the whole study period may be divided into three stages: the initial stage, the intermediate stage and the later stage. According to the three stages of groundwater chemistry reaction to water delivery and the relationships between groundwater chemical properties and groundwater depths, we educe that under the situation of water delivery, the optimum groundwater depth in the lower reaches of the Tarim River should be −5 m.     

农田土壤水分和盐分空间分布的指示克立格分析评价

运用非参数地质统计学的多元指示克立格法,结合单元指示克立格法,对黄河河套灌区55hm2的盐渍化土地上两个比较关键时期的土壤水分和盐分进行空间分布的分析,给出了同一时期土壤水盐和不同时期土壤盐分满足一定标准的综合概率图,并借助该案例详细介绍了多元指示克立格的原理、步骤及应用范围。指示克立格方法为不同尺度(从农田到区域)上水土资源质量的评价提供了新的方法,能为水土资源的现代决策管理提供指导。