| Summary: | 碩士 === 大仁科技大學 === 環境管理研究所 === 104 === The study was based on groundwater quality monitoring data collected by Environmental Protection Administration, in the second half of 2015. Electric conductivity (EC), total dissolved solids, chloride, sulfate, Na, K, Ca and Mg were selected as indexes to evaluate the current situation, characteristics and long-term trend of groundwater salinization in Pingtung Plain. Further study of groundwater in salinized areas was also conducted through comparison of salinization conditions in Yunlin and Changhua of Choshui River Alluvial Fan.
Results showed that the groundwater salinization areas were mainly distributed along coastal areas and east bank of Gaoping River, and decreasing progressively from coast to the inland part of Pingtung Plain. The area of EC surpassing the monitoring standard of 750 μmho/cm ranged from coast to 7 km inland. The correlation coefficients of the 8 salinity indexes were higher than 0.97 except Ca. This phenomenon was conspicuous in coastal areas, which indicated that marine pollution was the major cause of the highly saline groundwater, and over pumping of the groundwater by aquaculture was the main culprit of the pollution.
In terms of measurements in EC over time, more than a third of groundwater has been contaminated. The maximal EC values lay in Xinlong Community Park, Haiou Park in Fangliau Township and Jhongyun Elememtary School in Linyuan District. The first measurements after well drilling exceeded the monitoring standard 15 ~ 53.7 times. Although the measurements varied in the following decade, the long-term high EC indicated serious groundwater salinization.
Further comparison of Pingtung Plain and Choshui River Alluvial Fan showed the standard exceeding rate was in descending order of Yunlin, Changhua and Pingtung Plain. This result indicated that the proportion of groundwater salinization in both counties was higher than that in Pingtung Plain. However, in terms of the degree of salinization, Yunlin was the highest, followed by Pingtung Plain and Changhua County.
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