| Summary: | 碩士 === 國立臺北科技大學 === 環境工程與管理研究所 === 99 === Methylmercury may exist in various media, including water, soil, sediment, and biological tissues. Quantification of methylmercury in trace amounts is an important task, which is based on different sample pretreatments that liberate methylmercury from its matrix into Mili-Q water and the methylmercury can be subsequently determined. Taiwan EPA in 2009 proposed standard aqueous methylmercury determination method (NIEA W540. 50B). This study examined the proposed method to quantify methylmercury in water sampled from contaminated sites. Experimental Results showed that the distillate pH was below 3 based on Taiwan EPA method. The low pH was suspected to cause a low recovery of 5–6%. A modified distillation process was performed, namely, distilling the sample in a closed vessel without purging gases. Results showed that the recovery of methylmercury can significantly increase to 88–102%.
To determine methylmercury in soils, methods established by Brooks Rand laboratory and US Geological surveys’ (USGS) were chosen and examined. The analytical results showed that the recovery obtained from Brooks Rand method was greater (91.37%) than that from the USGS method (56.70%). However, it takes two days to get analytical results with Brooks Rand method. We tried to combine the USGS and Brooks Rand method, results showed that it took about six hours to obtain reliable data. The modified combined method was evaluated by analyzing two certified reference materials (SQC-1238、ERM-CC580). The recovery was within 75.8–102% with an average of 91.03±8.47% (MDL = 13.2 pg g-1). The modified method was used to quantify methylmercury in contaminated sediments sampled from a chlor-alkali factory; methylmercury concentration ranged between 1.00 and 6.38 ng g-1. Blood methylmercury was measured followed the method proposed by Liang et al (2000) with minor modifications. The method was preliminary evaluated by analyzing the standard reference material (SRM 955c). Recovery was shown to be 122%. Methylmercury in the tested maternal blood and cord blood ranged between 4.11 and 7.14 ng g-1.
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