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Soil and Groundwater Baseline Investigation of Drinking Water Source Quality Protection Area.

The project aims at establishing the baseline concentration of soil and groundwater in the drinking water source quality protection area (DWPA) and evaluating the soil quality for agricultural usage. In addition, in order to evaluate the increasing quantity of atmospheric depositing in soil, the project investigated concentrations of mercury in atmosphere, precipitation, and soil. On the other hand, the project used Simplified Bioaccessibility Extraction Test (SBET) to evaluate the bioaccessibility of heavy metal in soil. Finally, the collected data will be applied to the reference of the standard concentrations for contaminated soil and groundwater or other related management. The details of the performance are as follows: 1.In order to calculate the background value of heavy metal concentration in the soil from DWPA, the project investigated concentrations of heavy metal in 97 parent rock and 901 soil samples from DWPA. In accordance with the results of above-mentioned investigations as well as current regulations and using the calculation method abroad, we proposed the suggested upper limit for heavy metal background concentration such as As: 30 mg/kg; Hg: 1 mg/kg; Cd: 0.4 mg/kg; Cr: 100 mg/kg; Cu: 75 mg/kg; Ni: 55 mg/kg; Pb: 65 mg/kg; Zn: 200 mg/kg. 2.The project collected 106 soil samples from farmland in the DWPA, which investigated concentrations of heavy metal and pesticide. The results indicate that the heavy metal and pesticide concentration of some soil samples were higher than natural background soils, which means the long-term agricultural behaviours have influenced the soil quality in the DWPA. 3.The auto-monitoring of atmospheric mercury results from Shimen Reservoir collected from November 2015 through August 2016 exhibited that the average values of gaseous elemental mercury (GEM) was 2.15 ng/m3; particulate-bound mercury (PHg2.5) was 9.09 pg/m3; reactive gaseous mercury (RGM) was 2.60 pg/m3, which were all in the range of the atmospheric mercury background value. Additionally, the average mercury concentration of 42 precipitation samples collected in Shimen Reservoir from August 2015 through July 2016 ranged from 3.50 to 75.3 ng/L, and weighted-average concentration was 11.7 ng/L. Those values are not significantly higher than the mercury survey in other countries. Also, annual dry and wet atmospheric depositions were found 7.01 µg/m2 and 32.5 µg/m2. The project investigated concentrations of total mercury and methyl mercury in 40 surface soil samples from the DWPA. Total mercury concentration ranged from 0.038 to 0.445 mg/kg and methylmercury concentration ranged from 0.049 to 7.939 µg/kg, so we could evaluate the methylation rate of mercury in soils ranged from 0.04 to 1.78%. In accordance with the results of above-mentioned investigations, annual wet and dry atmospheric deposition contributed 0.88~7.90% to total mercury flux to the surface soil. 4.This project used SBET to evaluate the bioaccessibility of heavy metal in 50 soil samples. Lower bioaccessibility concentrations and the ratio of Hg and Cr were found among these items; furthermore, the bioaccessibility of As, Cd, Cu, Ni, Pb, and Zn in contaminated soils were higher than natural background soils. 5.This project surveyed 25 groundwater samples in total and found some items exceeding the groundwater monitoring standard values such as total hardness, total dissolved solids, chloride, ammonia nitrogen, sulfate, Fe, and Mn. The results could be related to the usage of surroundings and the distribution of the stratums.
Soil and groundwater background concentration, Wet and dry deposition of mercury, Bioaccessibility