1. As shown by the project executed in 2012 for the investigation and verification of soil and groundwater pollution in Chiayi City, certain farmland areas located in Shapi section of Chiayi City were contaminated by heavy metals. In order to determine pollution levels and to locate pollution sources, as well as to protect the farmland from further pollution, this present project was carried out by focusing on investigating the quality of the topsoil near the Shapi farmland control site. The major tasks and execution results of the present phase were summarized as follows:
2. This project completed the on-site survey of 247 farmland blocks, which are located in an area of about 50 hectares of farmland. According to the changed contract contents of August 6, 2013, the surface area of the farmland to be investigated is 8.7 hectares. As the investigation results showed, among the 51 farmland blocks which were examined, one block of 1425 m2 (that is, 2% of the all farmland blocks) exceeded soil (for food crops growing) pollution control standards, its pollutant being arsenic; 5 blocks, which covered a surface area of 3827 m2 and comprised 9.8% of the farmland under investigation, exceeded soil (for food crops growing) monitoring standards, their major pollutant being arsenic; the rest of the farmland blocks (45 blocks; 88.2% of the blocks under investigation) met monitoring standards.
3. An analysis of bottom sediments showed that the heavy metal pollutants sampled from earthen ditch outlets were different from those gathered from Chiayi Irrigation Canal. Examination of bottom sediments in earthen ditch outlets showed chromium and zinc as major pollutants (S1 exceeding chrome control standards), and arsenic and nickel as minor pollutants (a part of the samples exceeding monitoring standards). The examination of bottom sediments flowing from Chiayi Canal to converge with those of earthen ditches showed traces of cadmium and mercury concentrations. The quality analysis of Chiayi Canal water samples showed that their eight heavy-metal concentrations were lower than relevant standards, though their pH values, conductivity, and the levels of chloride and ammonia containments were higher and sampling sites W1, W2 and W3 were detected as containing arsenic and zinc.
4. In addition to the completion of planned tasks, the team also accomplished the extra work of 2 groundwater samplings, the soil drilling of 2 controlled pieces of farmland, and the continued monitoring of water quality. The research results of this project was used to screen the industries in the neighborhood. Among the 12 industries screened, the samples of bottom sediments gathered from 3 of them contained high concentrations of chromium and zinc and these industries had been listed as suspected sources of pollution. Another industry used underground irrigation wells; as the main pollutant of the farmland block was arsenic and the content of arsenic on the underground well walls was also high, it could be inferred that the arsenic pollution in the farmland block was caused by underground irrigation water.
5. Suggestions for the construction of future early-warning system for the area under investigation were proposed, and the present research findings would be included in “Soil and Underground Water Pollution Sites Information System.”