為了瞭解臺南地區農地重金屬影響之可能原因，本研究自行政院環保署收集台南市農地重金屬污染場址資料，並應用地理資訊系統(GIS)與平均最近鄰分析(Average Nearest Neighbor Analysis，簡稱ANNA)，將污染場址位置分佈與周圍工業區、河川及違章工廠進行農地重金屬污染特性分析。
污染場址與違章工廠分析結果顯示，南區、仁德區及麻豆區之重金屬污染農地與周圍違章工廠之ANNA分數(Z值)分別為-15.88、-18.13及-13.58，經判斷屬於群集分佈，顯示該區農地受重金屬污染與違章工廠可能存在某種程度之相關性。污染場址與工業區之分析結果顯示，南區及仁德區之污染場址與周圍工業區之ANNA分數(Z值)分別為+12.80及+14.86，皆屬於分散分佈，顯示該二區域農地受重金屬污染與工業區較無直接關係。污染場址與河川流域之分析結果顯示，南區及仁德區與二仁溪及三爺宮溪之Z值分別為-8.24與-8.21，係屬於群聚分佈，顯示農地受重金屬污染與附近水體有相關性。麻豆區所有污染場址資料與曾文溪之平均最近鄰分析所得Z分數為-6.07，係屬群集分佈；在排除距離曾文溪較遠之污染場址後再進行分析後，平均最近鄰分析所得Z分數為+1.59，顯示為分散分佈，上述二種分析結果有明顯的差異，平均最近鄰分析法中若有部分點位偏離整個群集或點位過於集中時，其分析結果容易產生判斷上的誤差。
本論文嘗試以GIS與ANNA進行臺南地區重金屬農地污染之特性分析，初步可瞭解大量的污染點位與場址特性間之相關性，然受限於ANNA方法的限制，目前尚無法獲取確切之結論。ANNA採用直線距離作為統計依據，並未考量地下水流向及分佈等因素作為分析項目，未來可以ANNA搭配不同可能參數進一步探討。 In order to understand the possible reasons for the impact of heavy metals in farmland in Tainan, this study collected data on heavy metal pollution sites from the Environmental Protection Agency of the Executive Yuan. The aim was to evaluate the correlation analysis between distribution of contaminated sites and industrial zones, rivers and illegal factories in Tainan City by Geographic Information System (GIS) and the Average Nearest Neighbor Analysis (ANNA).
The analysis of the pollution sites and illegal factories was shown that the ANNA scores (Z value) of heavy metal-contaminated farmland and surrounding illegal factories in the Southern District, Rende District and Madou District were -15.88, -18.13 and -13.58, respectively, which were belonging to cluster distribution. It revealed that there is a certain correlation between heavy metal pollution in farmland and illegal factories in this area. The analysis of the contaminated sites and the industrial zone showed that the ANNA scores (Z values) of the contaminated sites in the Southern District and Rende District and the surrounding industrial zones are +12.80 and +14.86, respectively, which were belonging to discrete distribution. It implied that the heavy metal pollution in the two regions is not directly related to the industrial area. The analysis results of the pollution site and the river basin showed that the Z values of the Southern District and Rende District and Erren River and Sanyegong Creek are -8.24 and -8.21, respectively, which were belonging to the cluster distribution. It showed that pollution of heavy metals in farmlands was related to nearby water bodies. The Z score of all the contaminated site data of the Madou District and the average nearest neighbor analysis of Zengwun River is -6.07, and as a cluster distribution. After elimination of the pollution site far away from Zengwun River, the Z score of the average nearest neighbor analysis is + 1.59 and as a distributed distribution, There were significant differences between the above two analysis results. If some sites falling off the entire cluster or if the sites are too concentrated, the results are prone to to misjudge.
The results showed that the characteristics of heavy metals contamination of farmland in Tainan by GIS and ANNA. The correlation between a large number of pollution data and site characteristics could be available. However, the exact conclusion is still not available due to the limitations of the ANNA method. The results of ANNA in this study only refer to distance between contaminated cites and possible pollutant resources but not consider the other potential conditions such as groundwater flowing direction and distribution. This study could apply different parameters for further results.
