飛灰固化物掩埋場中鉛與鉻滲漏之健康風險評估

The Health Risk Assessment for Pb and Cr Leachated from Fly-Ash Monolithic Landfill

吳聲燿(Sheng-Yao Wu)

指導教授 ： 於幼華

國立臺灣大學/工學院/環境工程學研究所/碩士(2006年)

https://doi.org/10.6342/NTU.2006.01422

摘要

至2004年底，台灣每年透過水泥固化法產生之飛灰固化物平均掩埋量近20萬公噸，其中大量重金屬危害物質主要以物理匣限方法限制其被雨水溶出；然而掩埋作業不慎造成固化物粉碎、不透水布鋪設品質不佳或用地取得困難而超限掩埋等因素所造成之嚴重地下水污染問題，屢見不鮮。

故此，本研究特由人體健康風險面向切入，評估飛灰固化物掩埋場中兩種重金屬物質鉛與鉻，自底層滲漏後，造成之地下水污染，並選擇五種掩埋情境結構，兩種重金屬溶出方式，以HELP模式搭配MMSOILs模式模擬位在400格網格點上的風險分布情形，進行人體健康風險評估，期望能藉此估算出人體健康風險值以作為固化物掩埋場風險管理與污染防治之策略。

研究結果顯示，當不透水布為最差鋪設品質時，所產生之滲漏水量最多，最佳鋪設品質時滲漏水量最少，顯示出不透水布品質之重要性。鉛與鉻最主要的暴露途徑與風險貢獻量，皆來自直接飲用地下水，佔總風險98%以上。若以地下水作為飲用水時，鉛平均僅有14.25%的地區符合飲用水法規濃度，鉻有96.5%以上的地區地下水濃度是在法規範圍內，顯示重金屬鉛的危害性遠大於鉻。

未考慮參數的不確定性時，衛生掩埋的鉛致癌風險約4.23E-07，非致癌風險0.63，屬安全範圍內，但考慮參數所造成之不確定性時，鉛於衛生掩埋的非致癌風險則為1.43，但封閉掩埋仍然為1以下，顯示衛生掩埋時，鉛風險變異較大，原因可能來自於固化物中鉛含量變異性較大所造成。

關鍵字

飛灰固化物 ； 衛生掩埋 ； 人體健康風險評估 ； 不確定性

並列摘要

As of 2004, nearly 200 thousand tons of fly ash monolith are created by Portland cement each year in Taiwan. The main purpose is to confine heavy metals to reduce the quantity leachated by precipitation. However, due to abnormal monolith fracture and poorly liner quality or exceeding usage than designed landfill capacity, serious groundwater pollution has been observed.

Therefore, this research focused on Pb and Cr leachated from monolithic landfill to assess the risk of groundwater pollution in the vicinity. The methodology combined water budget simulations using HELP model with fate and risk simulations using MMSOILs model for 5 kinds of landfill structures and 2 types of leaching models, and calculated the risk distribution over 400 grids in the down gradient direction of groundwater.

The results demonstrated that the worst liner quality will cause the largest leaching, but with the best quality liner the least leaching will be generated. The most significant exposure pathway is groundwater intake, which accounted for 98% of the total risk. Comparing Pb and Cr concentrations in the groundwater with the drinking water standards, only 14.25% of the total grids were found to be under 0.05mg/L of Pb, and over 96.5% of the total grids were in the safety range of Cr. The results indicated that we should pay greater attention to Pb leaching from fly ash monolithic landfills.

Without consideration of the parameters uncertainty, the cancer and non-cancer risk of Pb with the sanitary landfill method was 4.23E-07 and 0.63, respectively, both under acceptable levels. However, by considering the parameters uncertainty, the non-carcinogenic risk of Pb became 1.43, exceeding the acceptable level. Only under closed landfill method was the HQ below 1. The reason may be due to that there was high variability in the Pb concentration in the fly-ash monolith.

並列關鍵字

Fly-ash monolith ； Sanitary landfill ； Human health risk assessment ； Uncertainty

參考文獻

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