A two-column limestone reactor has been designed to reduce fluoride concentrations from wastewaters to below the maximum contaminant level (MCL limit) of 4mg/L. The reactor functions by forcing calcite (CaCO3) to dissolve and fluorite (CaF2) to precipitate in the first column. The second column is not necessary to remove fluoride but is used to precipitate the calcite dissolved in the first column. This returns the treated water to its approximate initial composition. In laboratory experiments, the fluoride concentration of the effluent from feedwaters containing initial F amounts of up to 109mg/L were brought below the MCL limit of 4mg/L with a porewater residence time within the column of 2h. Profile sampling shows that fluoride is reduced from 109 to 8mg/L after only 35min within the reactor. The major advantage of this potential technology over existing liming and ion exchange methods is that system monitoring is minimal, regular column regeneration is not required, and chemicals are not permanently added to the water. Because the CaCO3 dissolved in the first column is precipitated in the second, the reactor has potential application to reduce the concentrations from wastewaters of contaminants similar in charge and size to Ca2+ and CO32- through coprecipitation reactions. In a pilot experiment where fly ash leachate was spiked with mg/L levels of Cd, As, Cr, and Se and directed through the reactor, reductions in all elements except Cr occurred. Cd was the most notable. Influent concentrations from 2 to 30mg/L were reduced to below detection (<0.01mg/L)

In Shanyin, Shanxi province, China, As concentration in shallow groundwater exceeds guide concentrations, set internationally and nationally at 10-50mg/L, and may reach 1932.0mg/L, which has resulted in severe clinical symptoms of arsenic toxity. In this article, chemical characteristics of groundwaters containing anomalous As and mechanisms of arsenic release to shallow groundwaters were studied. Groundwaters containing anomalous As in the study area were characterized by higher pH, higher concentration of phosphate, higher concentration of naphthenic acid, and lower concentrations of sulfate and nitrate. Microbial metabolism of sedimentary organic matter, which is present as high as 1.0% organic C, results in the lower concentrations of sulfate and nitrate. The reactions decrease Eh and produce CO2, which promotes the dissolution of carbonates and increases pH. The clay minerals and colloids including organic matters scavenging arsenic would release arsenic to groundwater in higher pH and lower Eh environment. In addition, the competitive absorption between As and anions (such as phosphate and fluoride) contributes to the release of As from kaolinite, montmorillonite, illite, and Fe oxyhydroxides. Naphthenic acid also promotes mobilization and translocation of As in groundwater systems.

水文地质学在解决人类面临的众多资源-环境问题中发挥着关键作用，近40年得到快速发展。水文地质研究中带共性的关键科学问题包括：地下水系统中的物理-化学过程、场地评价方法和耦合模拟方法。为加快水文地质研究的创新进程，应当建立三种类型的研究项目平衡资助机制：小型的单个研究者主持的研究项目，多学科项目和多机构项目。

Groundwater is the most important source of water supply in Datong city. However, the levels of shallow Quaternary groundwaters from urbanized areas have been declining continuously and groundwater quality deteriorating in recent years. Understanding the geochemical evolution of groundwater is important for sustainable development of the water resources in Datong. Mineral hydrolysis of alumino-silicate minerals such as plagioclase and clinopyroxene, is the primary process controlling the concentration of H4SiO4 in the study area. Speciation calculations using the geochemical modeling code PHREEQC indicated that hydrolysis of bedrock, mainly composed of asalt and metamorphic rocks, is the major hydrogeochemical process controlling groundwater chemistry. The study area can be divided into 3 hydrogeochemical zones: A. Recharge (unimpacted) zone, B. Intermediate (industry-impacted) zone, and C. Discharge (agriculture-impacted) zone. Ion exchange and industrial and/or agricultural contamination contribute to the increase of Na+ from Zone A to Zone C, where the concentration of NO3-is up to 461.5mg/l with a mean value of 101.5mg/l, indicating that agricultural practice seriously affects groundwater. Sulfate concentration in groundwaters in an alluvial fan at Datong is extremely high, up to 1172.9mg/l, and shows a close relationship with the concentrations of trace elements, especially Ni and Co, indicating that coal mining is the main contamination source for groundwater from the alluvial fan, in addition to agricultural activities.