EPA-102-GA13-03-A281

102

23,843 千元

2013/01/09

2014/07/08

賴宣婷

土污基管會

詹萬芳

美商傑明工程顧問(股)台灣分公司

土壤及地下水

農地;鉛;糙米;空氣;土壤;盆栽試驗;序列萃取;鉛穩定同位素

agricultural land;lead;rice;soil;air;pot experiment;sequential extraction;stable lead isotopes

張尊國;王智澤

張元馨

02-23252100#816

sheena.chang@mwhglobal.com

為瞭解農地食用作物受到鉛污染之暴露途徑，遂執行「農地鉛污染對食用作物影響試驗計畫」（以下簡稱為本計畫），希冀透過環境介質與稻作試驗，以釐清農地食用作物鉛污染相關途徑，探討食用作物吸收重金屬鉛之影響因子，建立水稻吸收土壤重金屬鉛評估模式，評析國際土壤鉛管制值管理特性，並研擬全國農地土壤重金屬鉛之調查規劃。 本計畫之環境介質與稻作試驗工作包含102年第1期作先導試驗與第2期作雙重鉛源吸收試驗，並選定臺中市烏日區同安厝段農地作為雙重鉛源吸收試驗中現地試驗區農地試驗之試驗範圍。葉面吸收鉛盆栽試驗結果顯示土壤及葉面（空氣）雙重鉛源可能皆會影響糙米之重金屬鉛吸收情形，並且當土壤鉛濃度為背景值，糙米的重金屬鉛吸收量約有接近一半之比例（45 %）係來自葉面所貢獻，而土壤鉛濃度接近土壤污染管制標準時，葉面吸收仍至少有約35 %的貢獻比例，顯示出葉面（空氣）之鉛源是糙米吸收之重金屬鉛的重要途徑。現地試驗區農地試驗結果則指出由於臺中市烏日區同安厝段農地之土壤pH值普遍偏酸，再加上土壤質地又是以砂粒為主，皆符合相關文獻與本計畫歸納之鉛污染土壤中水稻容易吸收重金屬的土壤條件，因此推測這些土壤因子的複合影響加上過去遺留鉛污染的加成導致當地成為鉛米的高風險區。 依據本計畫建立之水稻吸收鉛預測模式可歸納出各項土壤因子與糙米鉛濃度之關係，利用水稻吸收重金屬鉛預測模式依據歷次計畫樣品數據歸納出之土壤pH值臨界值為6.28，表示當存在鉛污染之土壤pH值小於6.28係較容易種植出鉛米的土壤臨界條件。 應用鉛穩定同位素判釋各試驗成果則顯示，接受葉面噴灑硫酸鉛液體之試驗組，其稻葉同位素特徵趨近硫酸鉛特徵，可判定葉面（即空氣暴露）亦為水稻的鉛源吸收途徑之一。由歷年針對臺中市烏日區同安厝段高濃度土壤鉛之同位素調查與比對，背景以外之鉛同位素特徵僅有一種，代表該區域污染特徵已獲初步鑑定。 本計畫更蒐集美國、日本、荷蘭、加拿大等國之農地土壤鉛管制值管理特色、管制值訂定依據或原則，結果顯示多數國家土壤鉛管制策略係採行分區管理之形式，而其管制值之訂立，原則上亦多是以風險評估為基礎。以上資料顯示，目前國際環境管理趨勢為針對不同使用分區訂定對應之標準值，該值係依據健康風險評估並綜合經濟、行政考量等因素，此亦可作為我國環保署修正土壤污染管制標準值之重要參考。 綜前所述，糙米吸收重金屬鉛亦可能來自空氣之鉛源，後續若面臨農地鉛污染且其周圍有明確空氣污染排放源存在或大型空氣污染事件發生，建議可於發現污染事件之農地坵塊執行總懸浮微粒採樣作業並檢測樣品之鉛濃度，如空氣鉛濃度超出空氣品質標準則表示當地之空氣品質係為異常之狀態，再針對鄰近工廠進行現場勘查並執行排放管道採樣及檢測作業或是執行周界空氣測定作業，以掌握鄰近工廠的煙道排放與粒狀污染物逸散情形。透過排放管道或是周界空氣檢測結果可與土壤及作物檢測結果互相連結，藉此追查污染來源並且釐清污染責任，作為後續污染求償的重要依據。 環保署透過歷年計畫已逐步建立多項環境介質鉛同位素檢測技術與分析方法，依據本計畫應用鉛穩定同位素的經驗與成果顯示所需檢測技術與分析方法已臻成熟，可作為一般分析方法難以區別、辨識污染來源時，進一步之環境鑑識輔助工具，惟鉛同位素鑑識技術門檻較高且成本昂貴，需注意僅適用於無機物理性環境介質，但若檢測分析對象為有機生物體，可能會有分化機制而影響同位素研析數值之應用性，亦即若欲藉此做為釐清重金屬鉛在生物體內傳輸機制工具恐會受限，建議後續應用時必須考量適用場合、時機與對象。

農地;鉛;糙米;空氣;土壤;盆栽試驗;序列萃取;鉛穩定同位素

EPA102GA1303A281.pdf

22MB

2014/12/1 上午 12:00:00

The purpose of this project is to clarify the routes of exposure to lead contamination in farmland food crops. The lead content in the air was measured and environmental media such as soil, water bodies, sediments, pesticides, and fertilizers were also sampled. In addition, stable lead isotope analysis, sequential extraction analysis, laser ablation inductively coupled plasma mass spectrometry, and statistical analysis methods were adopted to test environmental media and rice crops. Additionally, we explored the pathways of lead into food crops by investigating the factors influencing heavy metal uptake, establishing a model for assessing lead uptake in rice from paddy soil, and assessing the international regulatory soil standards for lead. Furthermore, a nationwide investigation plan for lead in farmland soil was formulated. The results of foliar uptake experiment revealed that lead sources in both soil and foliage influenced lead uptake in the brown rice. In a saturated concentration of experimentally designed lead solution (PbSO4, 40 mg/L), the foliage accounted for the greatest uptake (45%). The results from the farmland experiment in the Tongancuo Section of Wuri District, Taichung indicated that under the influence of lead sources in both soil and air, the foliage uptake of lead was primarily from the air. The results indicated that the lead content in brown rice increased with decreased pH and increased sand content in soil. In summary, the analysis of lead in the plant tissues showed that, besides uptake by roots, foliar route is of similar importance to the soil-root pathway as a route of transport to the exposed parts of the plants. In this project, the results also showed that the sum of soluble fraction, exchangeable fraction, and carbonate fraction from sequential extraction, DTPA extraction, and total lead content were all positively related to lead content in brown rice. A predictive model and a discriminant model were established for assessing the uptake of lead in brown rice from paddy soil. Results of the modeling analysis showed similar results, i.e., the lead content in brown rice increased with increased lead concentration in soil and decreased pH, suggesting that the abovementioned factors may have caused contaminated brown rice in Tongancuo Section of Wuri District, Taichung. The interpretation results of applying stable lead isotope analysis indicated that Tongancuo exhibited characteristics of farmland pollution. Rice crops that were cultivated on soil with high concentrations of lead displayed consistency in isotopic characteristics between each portion of the rice plants and the source of lead in the polluted soil. This indicates that the lead uptake from soil crucially influenced the increase in lead concentration in each portion of the rice plants. Thus, stable lead isotope analysis continues to be a vital tool for identifying sources of contamination. This project examined the management and formulation bases or principles of farmland regulatory standards of the United States, Japan, the Netherlands, and Canada. In principle, the majority of regulatory standards were established based on risk assessments. The aforementioned data revealed that the general process of current international environmental management involves formulating corresponding standards based on factors such as health risk assessments, economic integration, and administrative considerations. Therefore, the findings of this study can be used as a crucial basis for Taiwan EPA in amending soil contamination regulatory standards. In summary, lead uptake that occurred in brown rice can be partially attributed to lead content in the air. Future studies on cases of lead contamination in rice can consider procedures for monitoring lead concentration in the air in conjunction with related administrative units. Through a series of past projects, the EPA has gradually established multiple lead isotope detection techniques and analytical methods for environmental media. Conducting relevant projects to apply lead isotope analysis as a support tool for identifying environmental pollution and thereby promote its application is recommended.

agricultural land;lead;rice;soil;air;pot experiment;sequential extraction;stable lead isotopes