Geospatial and statistical approaches to nitrate health risk and groundwater quality assessment of an alluvial aquifer in SE Nigeria for drinking and irrigation purposes

In agricultural districts, like Ogbaru in southeastern Nigeria, water supplies are under obvious threats from human activities. Therefore, continuous monitoring and assessment of water quality suitability for drinking, domestic, and irrigation purposes are encouraged to keep check of the effects of water contaminants. In this paper, several quality water assessment tools were integrated to determine the suitability of the groundwater in Ogbaru for drinking and irrigation uses and to assess the ingestion and dermal health risks of nitrate occurrence. The majority of the physicochemical parameters analyzed in this study were within their respective standard limits. However, groundwater quality index classified 52.63% of the groundwaters as excellent water and 47.37% as good water. Overall index of pollution, on the other hand, classified 84.21% as excellent water and 15.79% as acceptable water. The pH ranged from 5.4 to 6.8, indicating that the groundwater is acidic. Most irrigation water quality assessment indices (SAR, Na%, PS, KR, RCO, CAI-1 and 2) revealed that the groundwater samples are suitable for irrigation. However, magnesium hazard and permeability index grouped the majority of the water samples as unsuitable resources for irrigation uses. The nitrate health risk assessment (mean score = 1.371) indicated that children are exposed to higher non-carcinogenic health risk due to ingestion of contaminated groundwater than the other populations. It was observed that 21.05% of the groundwater samples had the highest concentrations of the analyzed chemical species. Multivariate statistical methods (hierarchical cluster analysis and factor analysis) efficiently aided the contaminant source apportionment. Based on the findings of this paper, it is advised that adequate regulatory strategies and water treatment techniques be adopted in the area to protect and sustain the groundwater quality and public health.     

抽水引起的含水层水平应变──地裂缝活动新机理

基于Darcy -Gersevanov广义渗流关系式 ,本文首先导出了单井定流量抽水引起的泰斯承压含水层水平运动和应变解析表达式 ,并据此提出了抽水诱发地裂缝活动的含水层水平应变新机理 ,其主要观点为 :受井栅的约束阻挡作用 ,抽水活动将在含水层内部形成近井径向挤压区和远井径向拉张区两个应变区域 ,随着抽水时间的增长 ,近井径向挤压区将逐渐向外扩展 ;当地裂缝及其下伏断层或裂隙位于抽水活动引起的径向拉张应变区域时 ,地裂缝将出现加速活动 ;反之 ,当地裂缝处于抽水活动引起的径向挤压应变区域时 ,地裂缝活动反而受到抑制。上述地裂缝活动机理通过大同机车工厂现场抽水实验得到了初步证实。     

红层区城镇地下水对建筑物基础腐蚀及防治研究——以天水市为例

地下水对建筑物基础腐蚀是发育广泛、速率缓慢的地质灾害,它对红层区城市基础工程危害尤显突出。以天水市的红层区为例,利用长期积累的大量地下水化学资料,探讨了腐蚀性地下水的成因,提出了防治地下水对建筑物基础腐蚀的对策。     

岩溶区土洞发育机制的分析

岩溶区地下水或地表水的活动 ,将对土层产生潜蚀作用及崩解作用 ,进而形成土洞。真空吸蚀作用 ,有利于土洞的发育扩大。地下水位的变化 ,将使土洞周围土体的应力状态发生改变 ,并有可能导致土洞周围土体产生塑性破坏 ,使土洞进一步扩大甚至塌陷.     

陕西泾阳南塬黄土滑坡灾害与引水灌溉的关系

陕西泾阳南塬塬边黄土滑坡频繁发生，造成的经济损失和人员伤亡极为惨重。本文讨论了区内黄土滑坡灾害形成的地貌地形及地质环境特征，着重分析了人类不合理的引用地表水灌溉，改变了地下水文条件，从而降低了土体的抗剪强度，导致黄土滑坡形成的过程和机制。通过研究认为，合理进行灌溉，控制地下水位是改善塬边地质环境和防治滑坡灾害的关键措施。     

Three-dimensional saltwater-freshwater fingering in porous media: contrast agent MRI as basis for numerical simulations

This study investigated miscible fingering phenomena in a saturated porous medium due solely to fluid density differences. The objective was to determine dissolved salt concentrations in the porous medium and, thus, local fluid density with high temporal resolution and covering substantial volume. A magnetic resonance imaging method, which can achieve this goal by adding Cu(II)SO(4) to salt solutions, has been developed. This method was applied here to observe and quantify three-dimensional miscible fingering for the initial unstable layering of saltwater above freshwater. Additionally, characteristic properties were defined and evaluated to facilitate a more meaningful comparison with numerical simulations.     

Exploring groundwater hydrochemistry of alluvial aquifers using multi-way modeling

A three-way data set pertaining to hydrochemistry of the groundwater of north Indo-Gangetic alluvial plains was analyzed using three-way component analysis method with the purpose of extracting the information on spatial and temporal variation trends in groundwater composition. Three-way data modeling was performed using PARAFAC and Tucker3 models. The models were tested for their stability and goodness of optimal fit using core consistency diagnostic and split-half analysis. Although, a two-component PARAFAC model, explaining 50.47% of data variance, yielded 100% core consistency, it failed to qualify the validation test. Tucker3 model (3, 3, 1) captured 55.18% of the data variance and yielded simple diagonal core with three significant elements, explaining 100% of the core variability. Interpretation of the information obtained through Tucker3 model revealed that the groundwater quality in Khar watershed is mainly dominated by water hardness and related variables, whereas, water composition of the dug wells is dominated by alkalinity and carbonate/bicarbonates. Moreover, shallow groundwater sources in the region are contaminated with nitrate derived from fertilizers application in the region. The shallow aquifers are relatively more contaminated during the post-monsoon season.     

Determination of five nitrobenzoic acids in groundwater by solid-phase extraction and liquid chromatography–mass spectrometry

A method involving solid-phase extraction (SPE) and reversed-phase liquid chromatography–mass spectrometry (LC–MS) has been developed for determination, in groundwater, of nitrobenzoic acids associated with 2,4,6-trinitrotoluene production. Pre-concentration on a co-polymer-based SPE cartridge enabled quantitative extraction of the analytes from water. Investigation of negative ion electrospray and atmospheric-pressure chemical ionization mass spectrometry indicated the sensitivity of APCI was more than twice that of ESI. An ¹⁵N-labeled internal standard was used to achieve more accurate quantitation and mass assignment. Recovery was better than 80% when 10 mL water was extracted with the SPE cartridge. Combination of SPE with LC–MS analysis resulted in method detection limits of less than 5 μg L⁻¹. The method has been used for analysis of groundwater samples collected from a site of a former ammunition plant. Contamination with nitrobenzoic acids was determined at μg L⁻¹ levels.