GIS Techniques for Mapping Groundwater Contamination Risk

The groundwater contamination risk map of a samplealluvial area was produced by using the IlwisGeographical Information System (GIS) to construct andto overlay thematic maps. The risk map has beenderived from the vulnerability map, the hazard map,where the potential contaminating sources wereidentified, and the socio-economic value of thegroundwater resource, represented by the wells. Thegroundwater quality map allowed thereliability of hazard and risk maps to be tested.The final map shows interesting results and stressesthe need for the GIS to test and improve on thegroundwater contamination risk assessment methods.     

A natural-gradient field tracer test for evaluation of pollutant-transport parameters in a porous-medium aquifer

This paper describes a natural-gradient field tracer test to characterise solute-transport properties in a sand and gravel aquifer in the Hebei Province, northern China. Some laboratory-scale column tests on aquifer material and a local-scale field borehole-dilution test have been conducted previously, but the field test reported herein represents the only large-scale tracer test in the aquifer, which is the sole water supply to the city of Shi Jiazhuang and which is threatened by urban pollution. The aim of the study was to quantify the transport behaviour of nonreactive pollutants in this aquifer. Little quantitative data are available concerning its solute-transport properties; thus, the results of the tracer test are significant and critical for understanding pollutant transport and fate. The in-situ tracer test was carried out in the aquifer using a slug injection of the geochemically conservative, radioactive iodine tracer ¹³¹I. The longitudinal (α _L ) and transverse (α _T ) hydrodynamic dispersivities for solute transport in the field are 1.72 and 0.0013 m, respectively. The ratio of longitudinal dispersivity α _L and the flow length at the field scale is 1:10. The ratio between α _L and α _T from the in-situ test (~1,300:1) demonstrates a dominant longitudinal dispersion in this fluvial sand and gravel aquifer. The tracer test further indicates a relatively short transit time for the aquifer (linear velocities ~13 m/d) under natural-gradient conditions. Electronic Publication     

Assessment of the impact of industrial effluents on water quality in Patancheru and environs, Medak district, Andhra Pradesh, India

The effects of multiple industrial-pollutant sources on the groundwater system were evaluated in the Industrial Development Areas (IDAs) of Medak district, Andhra Pradesh (AP), India. The quality of groundwater in the region has been affected negatively due to the discharge of effluents on open land and into ponds, tanks, and streams. Water samples from surface-water bodies, dug wells,and bore wells were analyzed for their major ion concentrations. The high values of electrical conductivity (EC) and concentrations of Na⁺, Ca²⁺, Cl^–, and HCO₃ ^– indicate the impact of industrial effluents. Based on the hydrochemistry, the groundwater is classified into various types, such as sodium-chloride, sodium-bicarbonate, calcium-chloride, and magnesium-chloride, and its suitability for drinking and irrigation has been assessed. The present studies made it possible to demarcate areas of contaminated groundwater and those prone to contamination in the near future. Water in the area has deteriorated all along Nakka Vagu up to a maximum distance of 500–700 m from the eastern bank. The groundwater quality in and around Patancheru (to a depth of 30 m) has become hazardous. Some possible remedial measures are suggested. Electronic Publication     

Pore-throat size distributions in Permo-Triassic sandstones from the United Kingdom and some implications for contaminant hydrogeology

Pore-throat size distributions (PSDs) from mercury injection capillary pressure (MICP) tests have been used to characterise 153 samples of Permo-Triassic sandstones from the United Kingdom. The PSDs have been parameterised using the Brooks-Corey and van Genuchten functions. Pore-throat sizes are in the range 0.01–427 μm, and dominant pore-throat sizes range from about 0.1–90 μm. Values of λ, the Brooks-Corey pore-size distribution index, range from 0.002–2.27, and values of m, the van Genuchten pore-size distribution index, range from 0.03–0.92. A number of classes of sandstone can be recognised on the basis of trends in the fitted parameters. The van Genuchten function provides the most effective method for classifying different sandstones. Additionally, a cross-plot of gas permeability against displacement pressure (derived from the van Genuchten function) shows that the data fall into two distinct sub-populations. The frequency distribution of a larger population of sandstone permeabilities can be modelled using the mean and standard deviation of the two sub-populations identified in the MICP study, assuming that the sub-populations are approximated by log-normal distributions. The distribution of sandstones with small pore-throat sizes is critical to the fate of pathogens and immiscible phase contaminants in the aquifer. Electronic Publication     

Large-scale aquifer sensitivity model

A 480-square-mile region within Will County, in northeastern Illinois, was used as a test region for the development of a methodology to map the sensitivity of aquifers to contamination. An aquifer sensitivity model was developed using a geographic information system (GIS) to overlay and combine several data layers. The components used for our model are: (1) depth to sand and gravel or bedrock, (2) thickness of the uppermost sand and gravel aquifer, (3) glacial drift thickness, and (4) bedrock geology. The model is an improvement over many previous aquifer sensitivity models because it combines specific information on depth to the uppermost aquifer with information on the thickness of the uppermost sand and gravel aquifer. This county-wide model results in an aquifer sensitivity map that can be a useful tool for making land-use planning decisions regarding aquifer protection and management of groundwater resources.     

Field observations on the variability of crude oil impact on indigenous hydrocarbon-degrading bacteria from sub-Antarctic intertidal sediments

Oil pollution of the oceans has been a problem ever since man began to use fossil fuels. Biodegradation by naturally occurring populations of micro-organisms is a major mechanism for the removal of petroleum from the environment. To examine the effects of crude oil pollution on intertidal bacteria, we repeated the same contamination experiments on nine different sub-Antarctic intertidal beaches using specifically built enclosures (PVC pipe, 15 cm in inner diameter and 30 cm in height). Despite the pristine environmental conditions, significant numbers of indigenous hydrocarbon-degrading bacteria were observed in all the studied beaches. Introduction of oil into these previously oil-free environments resulted in several orders of magnitude of increase in hydrocarbon-degrading micro-organisms within a few days in some of the studied sites but has no obvious effects on two others. The physical environment of the bacterial assemblage seems to play a major role in the biodegradation capacities. After 3 months of contamination, both remaining oil concentrations and biodegradation indexes differ strongly between the different stations. Thus, chemical and biological parameters reveal a strong heterogeneity of biodegradation capacities between the different sites.     

Identification of hydrogeochemical zones in postglacial buried valley aquifer (Wielkopolska Buried Valley aquifer,Poland)

This article presents the difficulty in identifying the hydrochemical zoning of a semi-confined aquifer, characterised by a relative small spatial differentiation of groundwater chemistry. It is shown that multivariate statistical methods can be used for the recognition and interpretation of the groundwater chemistry distribution in an aquifer. The hydrochemical zonation caused by both natural and anthropogenic processes was identified using factor analyses in combination with a classical interpretation of the hydrogeological material. The interpretation of the groundwater chemistry allows both identification of the aquifer recharge mechanism and verification of the groundwater-flow system.     

Heavy mineral distribution as related to environmental conditions for modern beach sediments from the Susanoglu (Atakent,Mersin, Turkey)

Geochemical works were conducted on anthropogenically effective lithologic unit exposing along the Susanoglu coast in Mersin, Turkey. For this purpose, beach sand sediments from 33 stations were collected and heavy metal and oxide concentrations were analyzed. To determine the source of heavy metals (natural and anthropogenic), simple and multivariate statistical analyses were applied. According to factor analysis, three factors were determined. The first factor consists of SiO₂, Al₂O₃, Na₂O, K₂O, TiO₂, Cr, Ni, Cu and Mo and total variance is explained with 27.502% and expressed as “natural process factor”. These elements (Cr, Ni, Cu, Mo) are closely associated with geogenic materials and came from same sources of ultrabasic rocks (ophiolite). The second factor consists of CaO, MgO, TiO₂, MnO, Ni, Pb, Zn and W and total variance is explained with 21.505% and expressed as “anthropogenic factor”. These elements (Pb, Zn, Cd, V, W) are anthropogenic and are mainly due to the effluent or industrial input/activities and came from different sources of pollution in the study area. The third factor consists of Pb, Cd and Sb and total variance is explained with 9.748% and expressed as “intermediate factor”. The factor analysis and the cluster analysis are in support of each other. Cr, Ni, Co, Cd, Hg and Mo concentrations are greater than Turkish acceptable values and they show toxic effect. Al, Cu, Pb, Cd and Mo concentrations in beach sand deposits in the Susanoglu coast are found as 1.44, 1.26, 1.21, 1.02 and 1.04 mg/kg and higher than those in Kızkalesi beach sands. However, all other heavy metal contents are determined in low concentrations.     

浅谈地下水硝酸盐污染

地下水不仅是水文循环的一个重要组成部分,还是人类的一种重要淡水资源,尤其是对于郊区和农村地区的用水.现在,地表水水源普遍受到污染,人类对地下水的依赖程度不断增加.目前我国的地下水资源污染严重.全国多数城市的地下水都不同程度的受到了点源和面源污染,多种元素超标,"三氮"污染最为严重[1].通过对地下水硝酸盐污染现状、危害和来源的分析,提出地下水硝酸盐污染的控制对策.     

The investigation of petrology and geodynamic mafic magmatism in Bijar area, west of Iran (Arabia- Eurasia collision zone)

In northeastern Sanandaj-Sirjan structural zone, the Takab-Ghorveh belt comprises a volcanic province which related to the collision between the Eurasian and Arabian continents. It contains almost Quaternary andesitic basalt to alkali basalt. These alkali basaltes show Strombolian type eruptions. The volcanic rocks in Bijar area represent a range of mafic magmas, re-vealed by mingling and mixing textures. A variety of features suggest that the lava flows before eruption from magma chambers, contaminated by continental crust.