本研究是以整治方法之化學處理技術中的萃取法為研究方法，採集兩種污染土分別為來自台北萬芳之砷污染土，以王水消化法分析得砷污染土濃度為 8089 mg/Kg，台南永康鉻污染土總鉻濃度為 639 mg/Kg，以鹼性消化法測得污染土中六價鉻濃度為 378 mg/Kg，佔鉻污染土濃度的 59 %。 選用一般常用的螯合劑EDTA以及生物可分解的藻酸鈉為萃取劑，對砷及鉻污染土進行萃取試驗及Tessier連續萃取，結果顯示EDTA及藻酸鈉對鉻污染土的去除率為 73 % 和 70 % ，對砷污染土去除率只有 16 % 和 11 %。針對砷污染土萃取效果不佳探討其原因，以XRF及XRD進行測定發現砷的型態為As2O3，由比對的方式確認其污染源之ㄧ為煙道底渣，此污染土為固相污染固相之型態，所以並不適合以萃取法處理。 最後在EDTA/藻酸鈉混合液萃取試驗中，發現藻酸鈉：EDTA為 2：8 時不論在砷或鉻污染土均發生加乘作用，而在 5：5 時兩者亦同時產生抑制作用，所以其競爭性作用是發生在藻酸鈉與EDTA兩者間與污染物種類是無關的。 Ethylenediaminetetraacetic acid (EDTA) has been used to extract heavy metals from contaminated soils; however, EDTA is not biodegradable and the treated soils might not be suitable for various uses. The objective of this thesis is to study the feasibility of using biodegradable sodium alginate as an extraction agent. The contaminated soil obtained from Taipei contained arsenic of 8089 mg/kg soil, and that obtained from Tainan contained chromium of 639 mg/kg with chromate of 378 mg/kg (about 59% of the total). Removal efficiency of chromium and arsenic by EDTA and sodium alginate were compared. The results showed the chromium removal efficiencies were 73 % and 70 % by EDTA and sodium alginate, respectively, and the arsenic removal efficiencies were 16 % and 11 % by EDTA and sodium alginate, respectively. The low removal efficiency of arsenic might be because that the arsenic was in form of As2O3(s), which was deposited from a exhausted gas stream as solid and was not suitable for chemical extraction. The extraction of metals by the mixture of EDTA and sodium alginate were also investigated. It was found that extraction of metal ions was most effective when sodium alginate/EDTA was 1/4.