可溶性有機碳對兩種土壤吸脫附銅鋅鎘之影響

The Effects of Dissolved Organic Carbon on Copper, Zinc, and Cadmium Sorption onto Two Soils

李家興(Chia-Hsing Lee)

指導教授 ： 陳尊賢

國立臺灣大學/生物資源暨農學院/農業化學研究所/博士(2011年)

https://doi.org/10.6342/NTU.2011.00937

摘要

畜牧廢棄物堆肥化及民生廢水污泥經處理後成為生物性固體 (biosolids) 是資源回收再利用的方式之一。這類堆肥富含氮、磷等營養元素，但堆肥中重金屬如銅、鋅之含量偏高，在田間施用這類堆肥時必需考慮農業生態環境中氮、磷、重金屬之累積、生物有效性改變及淋失。本研究目的為探討污泥堆肥、豬糞堆肥抽出之可溶性有機碳 (dissolved organic carbon; DOC) 的添加對人工製備孵育之銅、鋅、鎘污染土壤中，銅、鋅、鎘釋放之影響；並藉由探討兩種粘粒、兩種DOC與銅、鋅、鎘及可溶性有機碳的交互作用來解釋pH及DOC影響銅、鋅、鎘吸脫附的機制。結果顯示，在重金屬釋放的試驗裡，與pH 3之HClO4溶液比，以酸化至pH 3之DOC為萃取液可加速銅、鋅、鎘之釋放。但在相同的pH值下，DOC溶液釋出鎘之累積量與不含DOC之HClO4溶液處理下之累積量差異不大，顯示系統中鎘的釋放主要受到pH的支配。銅的累積釋放量在相同的pH值下，以DOC萃出之處理較HClO4溶液的處理高；表示DOC可直接影響銅之釋放。與Pu土系坋質黏壤土比較，Sk土系砂質壤土在初期即釋放較多之銅、鋅、鎘且總累積釋放量亦較高。在田間土壤溶液之pH範圍間 (pH 3-10)，藉由多種酸位置之解離模式來擬合溶液或懸浮液的酸鹼消耗，可將本研究中材料抽出之DOC及標準黏粒之表面歸類為3種酸位置。將材料的酸特性代入多種位置之吸持模式後，可求得重金屬與微粒之表觀錯合常數KS。黏粒與不同重金屬之穩定常數KS 大小依序約為銅 > 鋅 > 鎘；且高嶺石、蒙特石之表面位置對此三種重金屬的吸持主要受到pH之支配。銅、鋅、鎘與兩種堆肥抽出之DOC作用後發生的沉澱量不高，其中銅約在pH 6.5、鋅約在pH 8.0、鎘約在pH 9.9左右時有最大量之沉澱發生。內湖二級污泥堆肥及豬糞堆肥抽出之DOC溶液在高嶺石、蒙特石上之吸持量隨DOC濃度增加而增加，隨pH增高而降低。銅、DOC以及黏粒之混合試驗中，DOC可減少銅在黏粒上之吸附，且DOC在黏粒上之吸附因為銅存在而增加；DOC可能與懸液中的微粒競爭銅，或與銅競爭黏粒上之位置，使更多的銅留存於溶液中；本研究結果可作為解釋銅在土壤中釋放受到DOC促進之參考。由試驗的結果，施用含重金屬之豬糞堆肥與民生廢水污泥堆肥，應推廣在非強酸性以及非粗質地之土壤，且應注意土壤pH與DOC的管理。堆肥中DOC溶液，可作為促進金屬污染土壤洗提復育之天然物質，特別是對銅。土壤構造複雜，仍需要更深入的研究來探討其間的反應，並使模式更加完備。

關鍵字

高嶺石 ； 蒙特石 ； 污泥堆肥 ； 猪糞堆肥 ； 可溶性有機碳 ； 重金屬 ； 吸持 ； 釋放

並列摘要

Application of composted swine manure and municipal wastewater sludge is an important procedure for resource recycling as well as one of environment-friendly disposal of wastes. Moreover, instead of incineration by composting of green-wastes presumably reduce carbon dioxide emission, the principal component of greenhouse gases. Application of organic-matter-enriched composts can promote soil physical, chemical, and biological properties. However, science swine fecal content high level of Cu and Zn and municipal wastewater sludge content high level of various heavy metals generally, applying of swine manure compost (SMC) and municipal wastewater sludge compost (MWSC) may lead to heavy metal accumulation in soils, leaching into ground water, uptake by plants, and further, hazards to food chain. Thus, the heavy metal movement in soils is important issue while applying this kind of composts. The retention and release of heavy metals in compost-soil-water suspensions are mainly affected by pH, dissolved organic carbon (DOC) acidity, particulate surface properties, and reaction strength between specific heavy metal and function group. The acidity of particulate surface and DOM implicate acid site density and acidity strength. In this study, one commercial SMC, one prepared MWSC (composting of straw and secondary sludge from Nei-Hu municipal wastewater treatment plant; NH2SC), two soils (Sk sandy loam and Pu silty clay loam), and two source clays (kaolinite and montmorillonite) are investigated to determine the acidity and Cd, Cu, and Zn retention of each material with multi-bounding-site model, and the effects of compost-derived DOC on Cd, Cu, and Zn release from artificial contaminated soils. The results of release experiments show that Cu release from soils was slower than Zn and Cd. Addition of 0.01 M compost-derived DOC accelerated metal release and pH decrease because of the organic matter buffering. The lack consistency of pH effect on accumulated release within different DOC treatments shows that DOC reacted with Cu directly and kept more Cu in solution than water did while DOC increased more Zn retention by particulates. Additionally, heavy metal release from Sk sandy loam was faster than that from Pu silty clam loam. With alkalimetric titration results within field pH range, multi-acid site model fitting revealed that kaolinite, montmorillonite and DOC extracted from SMC and NH2SC content 3 acid sites (model describable). With acidity parameters from multi-acid-site model, multi-bounding site model fitting, incorporating effects of pH, revealed that two or more function group contributed heavy metal retention in the suspensions. Therefore, the model provided better description than the original Langmuir isotherm model did. Metal retentions by particulates were governed by pH. The Coprecipitation of metals and DOC were unapparent. Furthermore, the comparison of estimated stability constants (log KS) of metal-clay complex are described in order as fallow: Cu > Zn > Cd. The results of Cu sorption in Cu-DOC-Clay suspensions supported that DOC can eather compete surface sites with Cu or compete Cu with Clay, and hance, Cu sorption onto clays can be decreased (i.e. release more Cu) by DOC. The application of DOC to enhace soil washing process for metal contaiminated soils couled be considered.

並列關鍵字

swine manure compost ； municipal wastewater sludge compost ； kaolinite ； montmorillonite ； DOC ； heavy metals ； sorption ； release

參考文獻

李國欽、林浩潭。1997。農地污染及其防治。藥毒所專題報導。行政院農業委員會農業藥物毒物試驗所出版。第43期。

Adams, M. L., F. J. Zhao, S. P. McGrath, F. A. Nicholson, and B. J. Chambers. 2004. Predicting cadmium concentrations in wheat and barley grain using soil properties. J. Environ. Qual. 33:532-541.

Alloway, B. J. (ed.) 1995. Heavy metals in soils. Blackie Academic & Professional, Glasgow, UK.

Antoniadis, V., and B. J. Alloway. 2002a. Leaching of cadmium, nickel and zinc down the profile of sewage sludge-treated soil. Commun. Soil Sci. Plant Anal. 33:273-286.

Antoniadis, V., and B. J. Alloway. 2002b. The role of dissolved organic carbon in the mobility of Cd, Ni and Zn in sewage sludge-amended soils. Environ. Pollut. 117:515-521.