Arsenic mobilization in shallow aquifers of Datong Basin: Hydrochemical and mineralogical evidences

To better understand the sources and mobilization processes responsible for arsenic enrichment in groundwater in the central part of Datong Basin where serious arsenic poisoning cases have been reported, hydrochemical characteristics of the groundwater and the geochemical and mineralogical features of the aquifer sediments were studied. The aqueous arsenic levels are strongly depth-dependent in the study area and the high arsenic concentrations are found at depths between 15 m and 60 m, with a maximum up to 1820 μg/L. The hydrochemical characteristics of high arsenic groundwater from the Datong Basin indicate that the mobilization of arsenic is related to reductive dissolution of Fe oxides/oxyhydroxides and/or desorption from the Fe oxides/oxyhydroxides at high pH (above 8.0). The bulk chemical results of sediments show the arsenic and iron are moderately correlated, suggesting that arsenic is associated with iron-bearing minerals. Results of sequential-extraction experiment show that solid-phase arsenic is similarly distributed among the different pools of reservoir in the aquifer sediments. Strongly adsorbed arsenic and co-precipitated arsenic are its dominant species in the solid-phase. Geochemical studies using chemical analysis, X-ray diffraction and scanning electron microscopy on magnetically separated fractions demonstrate that iron oxides/oxyhydroxides with residual magnetite and chlorite, illite, iron oxides/oxyhydroxides-coated quartz and feldspar, and ankerite are the dominant carriers of arsenic in the sediments. The major processes of arsenic mobilization are probably linked to desorption of As from Fe oxides/oxyhydroxides and reductive dissolution of Fe-rich phases in the aquifer sediments under reducing and alkaline conditions.     

A dynamic programming model for optimal planning of aquifer storage and recovery facility operations

Aquifer storage recovery (ASR) is an innovative technology with the potential to augment dwindling water resources in regions experiencing rapid growth and development. Planning and design of ASR systems requires quantifying how much water should be stored and appropriate times for storage and withdrawals within a planning period. A monthly scale planning model has been developed in this study to derive optimal (least cost) long-term policies for operating ASR systems and is solved using a recursive deterministic dynamic programming approach. The outputs of the model include annual costs of operation, the amount of water to be imported each month as well as the schedule for storage and extraction. A case study modeled after a proposed ASR system for Mustang Island and Padre Island service areas of the city of Corpus Christi is used to illustrate the utility of the developed model. The results indicate that for the assumed baseline demands, the ASR system is to be kept operational for a period of 4 months starting from May through August. Model sensitivity analysis indicated that increased seasonal shortages can be met using ASR with little additional costs. For the assumed cost structure, a 16% shortage increased the costs by 1.6%. However, the operation time of ASR increased from 4 to 8 months. The developed dynamic programming model is a useful tool to assess the feasibility of evaluating the use of ASR systems during regional-scale water resources planning endeavors.     

河北矾山磷矿采空塌陷、地裂缝和含水层破坏评估与防治

矾山磷矿是华北地区大型磷矿生产矿山,为第四系孔隙水及基岩裂隙水充水矿区。本文在分析地质采矿条件基础上,对采空塌陷、地裂缝地质灾害和含水层破坏的成因进行了分析与评估,并提出了相应的防治措施。     

Groundwater vulnerability assessment of the SW Trans-Danubian Central Range, Hungary

 The most important karst water reservoir of Hungary is found in the SW Trans-Danubian Central Range, selected as test area for the proposed "system approach" and the application of GIS/ARC-INFO to vulnerability mapping. In addition, a case-study exemplifies the particularities of regional karst-aquifer vulnerability, and moreover the interpretation of data and maps from the very same point of view. The work has resulted in plotting an atlas to be a useful tool in the hands of land-users and waste-disposal managers, helping them to prevent groundwater deterioration. Received: 22 July 1996 · Accepted: 12 September 1997     

Surface and groundwater quality in the northeastern region of Buenos Aires Province, Argentina

This work studies the water quality of the Pergamino–Arrecifes River zone in the Rolling Pampa, northeast Buenos Aires Province, Argentina. Temperature, pH, specific conductivity, Na, K, Mg, Ca, , Cl⁻, , , Si, Ag, Al, As, B, Ba, Be, Br, Cd, Co, Cr, Cu, Fe, Hg, Li, Mn, Mo, Ni, P, Pb, Se, Tl, U, V, Zn, and the environmental stable δ¹⁸O and δ²H isotope ratios were determined in 18 sampling stations. Natural and anthropogenic features influence surface and groundwater quality. Point pollution sources (septic wells and other domestic and farming effluents) increase the nitrate concentration. The values of pH, , Al, As, B, Fe, and Mn exceed the respective Argentine reference thresholds in different sampling stations for human drinking water; B, Mo, U, and V for irrigation; and V and Zn for cattle consumption.     

Interpretation of pumping test data from large diameter wells on an oceanic island

 Estimation of aquifer parameters is vital for the assessment of groundwater potential and groundwater flow regime. On an oceanic island where fresh water lens is fragile and sensitive to various stresses, it is even more essential that in order to assess the potential of fresh water lens and the effect of various stresses on the fresh groundwater regime the parameters should be representative to the field hydrogeological set up. Pumping tests conducted on existing large diameter wells on an oceanic island have been analyzed. A finite difference method has been used to take into account the well storage, partial penetration and upconing effect into the aquifer. Forward modeling has been carried out to estimate aquifer parameters from the pumping test data. Field examples are described. Received: 15 June 1998 · Accepted: 25 August 1998     

The fluoride in the groundwater of Guarani Aquifer System: the origin associated with black shales of Paraná Basin

This work presents petrological and geochemical results of the black shales interval from Permian and Devonian strata of the Paraná Basin, Brazil and its relationships with fluoride of groundwater from Guarani Aquifer System. The Guarani Aquifer, located in South Brazil, Uruguay, Paraguay and Argentine, presents contents of fluoride higher than the Brazilian accepted potability limits. Several hypotheses have been presented for the origin of the fluoride in the groundwater of the Guarani Aquifer. Microcrystalline fluorite was registered in black shales of Ponta Grossa and Irati formations from Paraná Basin. The results shown in this work suggest that fluoride present in groundwater of Guarani Aquifer can be originated in deeper groundwater that circulates in Ponta Grossa and Irati formations. The interaction of the groundwater coming from deeper black shales with the groundwater-bearing Aquifer Guarani System occurs through regional fragile structures (faults and fractures) that constitute excellent hydraulic connectors between the two sedimentary packages. The microcrystalline fluorite registered in Ponta Grossa and Irati Formations can be dissolved promoting fluoride enrichment in groundwater of these black shales and Guarani Aquifer System.     

云南鹤庆北衙铁金矿区矿坑涌水量预测

北衙金矿区是以溶蚀裂隙岩溶含水层为主的矿床,大部份矿体位于当地侵蚀基准面1694米(W123泉)以下,水文地质勘探的程度为以溶蚀裂隙含水层充水为主的复杂类型,标高1734米以上为简单类型。以抽水试验取得成果,介绍矿区矿坑涌水量预测采用的主要预测方法。通过矿山后续排水疏干的实际情况,对预测的方法和矿坑涌水量进行论证。