| Summary: | 博士 === 國立屏東科技大學 === 環境工程與科學系所 === 99 === Many contaminated sites were caused by illegal dumping hazardous wastes in Taiwan. These sites were potentially harmful to human health and the environment. In the past, the remediation goal of soil contaminated site was based on the control standard, which resulted in a great deal of manpower, material and financial resources consumption. Therefore, the domestic and international were actively developed a tiered approach of human health risk assessment model to establish an effective and economic "contaminated sites management strategy". A series of standard guides of RBCA have been developed by American Society for Testing and Materials (ASTM). The Risk-Based Corrective Action (RBCA) is rapidly becoming an accepted approach for the remediation of contaminated sites.
This study based on RBCA mathematical model investigated a heavy metal contaminated sites, the exposure risk assessment was conducted with a tiered approach to estimate the carcinogenic risk and the non-carcinogenic risk. Both exposure scenarios assumed the sites as the residential and the industrial areas, and both receptors of adults and children were considered with seven exposure pathways into the approach.
The results showed that the first tier of the carcinogenic risk and the non-carcinogenic risk were 2.26×10-4 – 3.14×10-4 and 68.2 - 117, respectively. The risk was clearly higher than the acceptable standard. Results of the second tier calculation showed that the carcinogenic risk and the non-carcinogenic risk ranged from 5.71×10-5 to 1.23×10-4 and from 6.19 to 7.97 respectively, which were a great threat for human health.
The third tiered risk analysis was performed by using @ RISK Palisade Monte Carlo simulation, the normal distribution was adopted for both exposure parameters and concerned pollutants. The simulation results showed that 95% percentile of the risk distribution value was between the first and second tiered risk. The carcinogenic risk and the non-carcinogenic risk ranged from 1.09×10-4 to 1.95×10-4 and 10.1 to 65.6, respectively. The risks were also demonstrated that the contaminated site was an unacceptable risk level.
However, sensitivity analysis indicated that the major parameters in adult’s carcinogenic risk were the receptor weight, the average time for carcinogenic, exposure period, exposure frequency, concentration of arsenic in groundwater, drinking water rate, concentration of arsenic in soil, soil ingestion rate, skin absorption fraction, sorption coefficient of skin, exposed surface area ratio, and height of the top sources of air mixing zone. The major sensitivity parameters in adult’s non-carcinogenic risk were the average time for non-carcinogenic, the receptor weight, exposure period, exposure frequency, event of shower frequency, concentration of chromium in soil, body surface area, fraction of the skin absorption of chromium, sorption coefficient of skin, drinking water rate, and concentration of arsenic in groundwater.
Tired approach of health risk assessment can be used not only as standards for contaminated sites remediation, but also an important way to assess the contamination degree. This study provides a streamlined process and guidelines of developing the risk-based decision-making strategy for contaminated sites in Taiwan.
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