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The Study of the Heavy Metals Content in Compostable Fraction of Municipal Solid Waste
研究結果顯示，都市垃圾經過兩個有的醱酵分解之後，各醱酵槽可堆肥成份中之重金屬量均呈現增加的趨勢，其中未經分類處理之Ⅰ號槽中重金屬總量升高為原來的2.16~3.69倍，僅含可堆肥成份之Ⅱ號槽其各金屬總量則升高為原來的1.72~2.30倍，而不含金屬類之Ⅲ號槽則升高為原來的2.00~2.58倍，顯示除了有機物被分解減少產生之濃縮效應外，堆積垃圾組成的復雜性也會影響其中重金屬之含量。由水溶性及0.1N HCI萃取實驗結果得知，各槽中水溶性重金屬之含量在經過兩個月的醱酵後，除了銅呈現出增加的趨勢外（由1.20-1.73mg/g增加至3.75-6.49mg/g，其中以Ⅰ號槽的增加量為最大），鉛、鎳的溶出量並沒有太大的變化，而鋅則呈現出下降的變化（由6.59-9.77mg/g下降至3.49-5.99mg/g）。而各金屬在0.1N HCI溶液中的萃取量，除Ⅰ號槽因受堆積垃圾組成的影響，呈現增加（除了鋅）的變化外，Ⅱ、Ⅲ號槽中各金屬的萃取量均呈現下降之趨勢。此外，連續萃取的結果顯示，都市垃圾可堆肥成份在醱酵前，鉛主要分佈在殘餘態（34.11-46.98%）中；鋅主要係以沈澱的形態存在，主要分佈在氣化物聯結態（39.31-40.32%）及碳酸鹽聯結態（28.92-32.90%）；銅、鎳則以有機物聯結態為主（銅46.69-54.16%;鎳26.24-36.42%）。經過兩個月的醱酵後，可堆肥成份中各金屬之有機物聯結態及氧化物聯結態均較醱酵前增加；而可交換性形態的變化與水溶性重金屬的萃取結果有相同之變化趨勢，鋅在碳酸鹽聯結的含量明顯較其他金屬增加。
Three different composition of the municipal solid waste (MSW) were made up to study the influence of the composting processes on the total content, water soluble content, 0.1N HCI-extractable content, and metal species of Pb, Zn, Cu, Cd, Ni during composting. The aim of this study was focused to comprehend the variation of the heavy metal pollutant in the view of composting, and to evaluate the potential of heavy metal pollution from the composts produced from MSW. The results revealed that the concentration of total content for the five heavy metals in compostable fraction increased in each compos (Ⅰ,Ⅱand Ⅲ) were respectively 2.16-3.69, 0.72-1.30, 1.00-1.58 times at the end of the composting process. The increased was due not only to mineralization of the organic matter as in compost Ⅱand Ⅲ,but also to that some of the heavy metals which at the beginning of the composting process were not contained in the compostable fraction which have been dissolved and became incorporated into the compostable fraction as in compost Ⅰ by the end of the composting process. The water soluble content of Cu increased and Zn decreased in two months of composting, and that of Pb and Ni add not change during the composting period. In 0.1N HCI extraction experiment, the results showed that the content variation of extracted for composting Ⅰincreased, expect Zn. But the content extracted from both Composting Ⅱand Ⅲ were decreased during the composting period. Before composting the species of Pb was mainly distributed over the residue fraction(34.11-46.98%); and the most of Zn was precipitated as the oxids(39.31-40.32%) and carbonates (28.92-32.90%) species; the major forms of Cu,Ni were in organically spcies (Cu, 46.69-54.16%, Ni,26.24-36.42%). After two months of composting, the fraction of the species that bound to organic matter and oxides were increased for the five tested metals, and the variation for the exchangeable species was similar to that of the water soluble contents. Beside that, the carbonate Zn increased significantly more than others.
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