銅(II)與鎘(II)在不同分子量土壤腐殖質錯合探討

Complexation of Cu(II)and Cd(II) with size fractioned soil humic substances

戴伯宇(Tai Po-Yu)

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(2020年)

https://doi.org/10.6346/NPUST202000389

摘要

土壤腐殖質 (soil humus substance SHS) 廣泛存在於土讓環境，SHS是一種複雜、質異、多態的混合物，具有高至低分子量。SHS與金屬離子相互作用形成金屬有機配合物影響金屬之生物毒性與可用性。
本研究採用四場址土壤，土壤前後處後利用鹼液(NaoH)萃取土壤腐殖質(SHS)溶液，SHS濾液(MW-O)藉由掃流式濃縮設備物理性分離出不同分子量SHS溶液。分別為MW-A、MW-B、MW-C、MW-D與MW-E。SHS分析光學特性，利用螢光衰減法(FQ)以Stern-Volmer方程式探討Cu、Cd與各分子量SHS之錯合常數(Log K)。
SHS之EEM(螢光激發/發射光矩陣)有5個顯著的波峰，分別定義為Peak-A(Ex/Em=320-330/400-420 nm屬類腐殖酸)、Peak-B(Ex/Em=270-280/400-410 nm屬類腐殖酸)、Peak-C(Ex/Em=220-230/400-420 nm屬類黃酸)、Peak-D(Ex/Em=220-230/330-350 nm屬類蛋白色胺酸)、Peak-E(Ex/Em=220-230/300-320 nm屬類蛋白酪胺酸)。5個波峰與CuII有顯著的錯合效果，共360個FQ試驗CuII得到211個有效試驗，Log K介於3.40至6.55 L/mol-C，平均5.06±0.41 L/mol-C。5個波峰之Log K分別為4.84±0.32，5.10±0.48，4.95±0.38，5.27±0.31與5.17±0.47 L/mol-C。SHS-CdII錯合試驗，共360個FQ試驗CdII得到171個有效試驗，Log K介於3.18至5.15 L/mol-C，平均4.43±0.37 L/mol-C。其中Peak-C與Peak-D波峰與CdII錯合效果最顯著，72個FQ試驗中有效試驗個數分別為68與50個，Log K分別為4.19±0.33與4.60±0.26 L/mol-C。
SHS-CuII之Log K與指標A250正相關，SHS-CdII之Log K與指標A250為負相關。表示CuII與SHS溶液極性分子豐富錯合Log K增加，CdII之 Log K降低。SHS-CuII與SHS-CdII與螢光指標HIX皆呈負相關性，表示錯合效果會受SHS腐殖化程度增加而Log K降低。

關鍵字

土壤腐殖質(SHS) ； 銅與鎘 ； 光學指標 ； 不同分子量 ； 螢光衰減 ； 錯和係數(Log K)

並列摘要

Soil humic substances (SHS) exist widely in the soil environment. SHS is a complex and heterogeneous organic mixture with various molecular weights. SHS interacts with metal ions to form metal-organic substance complexes that affect the biotoxicity and availability of metals.
In this study, soil was taken from four sites. After soil pre-treatment, the SHS was extracted with an alkaline solution (NaOH). An ultrafiltration system was used to separate the SHS filtrate (MW-O) into five size-fractioned SHS solutions, which were designated as MW-A, MW-B, MW-C, MW-D and MW-E solutions. SHS solutions were analyzed for optical properties. The fluorescence quenching (FQ) method was used to investigate the binding stability constants (log K) of Cu, and Cd with size-fractioned SHS solutions and the log K was fitted with the Stern-Volmer equation.
The SHS fluorescence EEM (Excitation/Emission Matrix) has five significant peaks, which were defined as Peak-A (Ex/Em= 320-330/400-420 nm, attributed to humic acid-like substances), Peak-B (Ex /Em = 270-280/400-410 nm, attributed to humic acid-like substances), Peak-C (Ex/Em = 220-230/400-420 nm, attributed to fulvic acid-like substances), Peak-D (Ex/Em=220- 230/330-350 nm, attributed to protein tryptophan) and Peak-E (Ex/Em = 220-230/300-320 nm, attributed protein tyrosine-like substances). CuII had significant quenching effects when binding with SHS, producing five significant fluorescent peaks. In a total of 360 CuII-SHS FQ tests, 211 valid tests were obtained, with log K ranging from 3.40 to 6.55 L/mol-C; the average was 5.06±0.41 L/mol-C. The log K were 4.84±0.32, 5.10±0.48, 4.95±0.38, 5.27±0.31 and 5.17±0.47 L/mol-C for Peak-A, Peak-B, Peak-C, Peak-D, and Peak-E, respectively. In the SHS-CdII quenching test, a total of 360 FQ tests were run; 171 valid tests were obtained. The log K ranged from 3.18 to 5.15 L/mol-C; the average was 4.43±0.37 L/mol-C. In CdII-SHS tests, Peak-C and Peak-D had the most significant quenching effect. The effective FQ test number were 68 and 50, respectively for 72 tests per each peak, and the average log K were 4.19±0.33 and 4.60±0.26 L/mol-C, respectively.
The log K of SHS-CuII was positively correlated with the index A250, but the log K of SHS-CdII was negatively correlated with the index A250. That data suggested that the abundance of polar organic substances in SHS solution increased the CuII log K, but decreased the CdII log K. Both log K of SHS-CuII and SHS-CdII were negatively correlated with the fluorescence index HIX, which suggested the extent of humification of SHS decreased the log K.

並列關鍵字

Soil humic substances (SHS) ； copper (Cu) and cadmium (Cd) ； optical index ； size-fractioned ； fluorescence quenching method ； binding stability constants (log K)

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