河川重金屬液相與固相(懸浮固體)分佈與風險評估

Heavy metal distribution and risk assessment of suspended particulate matter-water in rivers.

許善惟(Hu Shan-Wei)

指導教授 ： 陳庭堅

國立屏東科技大學/工學院/環境工程與科學系所/碩士(2019年)

https://doi.org/10.6346/NPUST201900368

摘要

重金屬是環境中常見污染之一，而重金屬在環境的濃度與分配影響重金屬在環境中的宿命，生物毒性與傳輸。河川的溶解性有機質(DOM)與顆粒性有機質(POM)通常扮演著水體污染物的吸收者。重金屬進入水體環境會吸附於POM與DOM。本研究收集武洛溪上、中、下游水樣與SPM以及萃取SPM之腐植質，探討金屬於顆粒性固體、膠體、真溶解相之濃度與分配。藉由風險評估了解重金屬危害性。

將通過0.45 μm濾膜的濾液(定義為O原液)、10 kDa-0.45 μm溶液(MW-A)、1-10 kDa (MW-B)、及< 1 kDa(MW-C)。樣品分別測量重金屬及溶解性有機碳濃度(DOC)。懸浮顆粒物量測重金屬全量濃度以王水消化法測量，藉序列萃取方法了解金屬型態分佈評估金屬移動性及生物可利用性。結果顯示DOM(液相)與POM(懸浮固體)重金屬濃度皆以Fe>Cu>Mn>Ni>Cr。DOM中之Fe、Cu、Ni與DOM MW-C結合，POM則是Fe、Cu、Mn與DOM MW-A結合。DOM經由DOC標準化Mn MW-B最大；Fe、Cu與Ni之MW-C最大。POM之Fe、Mn MW-A最大；Cu MW-B最大，而Ni MW-C最大，Cr在DOM或POM中皆無一致性。

序列萃取結果顯示各金屬之移動性組成百分比依序為Pb(90.3 %)> Zn(88.8 %)> Mn(87.4 %)>Cu(82.2 %)>Ni(55.9 %)>Cr(43.9 %)>Fe(17.4 %)。SPM重金屬除了Fe、Cr、Ni外，可能約有82 %以上的金屬具有移動性。
經風險評估之重金屬富集因子(Enrichment factor，EF)之結果顯示，Zn與Cd在武洛溪皆為輕度污染(EF=1.54~2.96)。而Cu、Mn、Cr與Ni皆為無低富集程度(EF<1)。潛在生態風險指數(Potential ecological risk index，PERI)評估結果顯示武洛溪具有高度嚴重的潛在風險等級，而Cd金屬是造成此風險的主要金屬。

關鍵字：重金屬、顆粒懸浮固體、序列萃取、分配係數、生態風險評估

關鍵字

重金屬 ； 顆粒懸浮固體 ； 序列萃取 ； 分配係數 ； 生態風險評估

並列摘要

Heavy metals are one of the common pollutions in the environment. The concentration and distribution of heavy metals in the environment affects the fate, biotoxicity and transport of heavy metals. In aquatic environment, heavy metals commonly adsorb to Dissolved organic matter (DOM) and particulate organic matter (POM). This study collected the water samples and suspended particulate matter (SPM) from upper, middle and lower sites of WuLu Creek. Humic substances were extracted from SPM. The concentration and distribution of metals in SPM, colloids, and true dissolved phases were examined to understand the distribution and risk of heavy metals in aquatic environment.
The filtrate solutions (defined as O, <0.45 μm) of DOM and POM were separated into three different molecular weight solutions: MW-A (10 kDa-0.45 μm), MW-B (1-10 kDa) and MW-C (< 1 kDa). The solutions were measured concentrations of heavy metals and dissolved organic carbon (DOC). The total concentration of heavy metals in suspended particulate matter was measured by aqua regia digestion method. The metal types were evaluated by sequence extraction method to evaluate metal mobility and bioavailability. The results shown that the concentrations of heavy metal in DOM and POM were Fe > Cu > Mn > Ni > Cr. In DOM, Fe, Cu, and Ni were majorly distributed in MW-C, while in POM, Fe, Cu, and Mn were majorly distributed in MW-A. In DOM, DOC normalized Mn concentration was highest in MW-B and Fe, Cu and Ni concentrations were highest in MW-C. In POM, Fe and Mn concentrations were highest in MW-A, Cu concentration was highest in MW-B, and Ni concentration was highest in MW-C. However, Cr was not consistent in DOM and POM.
The results of sequence extraction showed that the mobility percentage of each metal was Pb (90.3 %) > Zn (88.8 %) > Mn (87.4 %) > Cu (82.2 %) > Ni (55.9 %) > Cr (43.9 %) > Fe (17.4%). In addition, the percentages of Fe, Cr, and Ni in SPM may have higher than 82% mobility potential.
The results of the heavy metal enrichment factor (EF) shown that both Zn and Cd were slightly polluted in WuLu Creek (EF=1.54~2.96). Cu, Mn, Cr and Ni were low enrichment factor (EF<1). The potential ecological risk index (PERI) assessment shown that WuLu Creek had a highly potential risk, and Cd was the main metal causing this risk.

Keywords: Heavy metals, Suspended particulate matters, Sequence extraction, Distribution coefficient, Ecological risk assessment

並列關鍵字

Heavy metals ； Suspended particulate matters ； Sequence extraction ； Distribution coefficient ； Ecological risk assessment

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