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.

The response of carbonate aquifer to climate changes and ground water exploitation was studied at Shentou Springs. The springs consist of about 100 spring points. The long-term (1958-1999) annual average discharge of the springs is 6.86m3/s. The discharge has diminished since the early 1960s. In 1993, the discharge (3.81m3/s) was the smallest during the period of record. Data of restored spring discharge and precipitation during 1958-1999 were analyzed using a seasonal decomposition method. The result of analysis shows that the discharge of Shentou Springs responds remarkably to precipitation change. Lowering of ground water table and attenuation of spring discharge at Shentou in the last several decades are largely a response of the ground water system to the deficiency in regional precipitation in northern China. As compared with the effect of climate, human activities (mostly in the form of ground water abstraction) are secondary in affecting spring discharge. When the volume of exploited Quaternary ground waters that are partly recharged by karst waters exceeds 6400

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)

Three types of zeolite (NaP1 zeolite, analcime and chabazite) were hydrothermally synthesized by reacting fly ash with NaOH solution. The maximum conversion rate from fly ash to single zeolite is about 40%-75%, and the total conversion rate 60%-80%. The synthesis experimental results indicate that factors including vortex, viscosity, temperature, reaction time, and NaOH concentration in the reaction system strongly affect the type and conversion rate of zeolites. The batch experiments of removing Cu2+, Pb2+ and Cd2+ from wastewaters show that the adsorption capacity of zeolites synthesized is higher than that of fly ash. Keywords: coal fly ash, hydrothermal synthesis, zeolite, heavy metal, wastewater, adsorption.