In this paper, the calculation formula proposed by Han Bing and Bond is adopted, but the natural attenuation of carbon tetrachloride is not considered here, and only the residual ratio TF of treated carbon tetrachloride is considered. The daily average exposure dose per unit weight of CDI in drinking water route can be expressed by the following formula: (12. 1 1), (12. 13).
CDI water = tcre+tcrb (12.11)
Among them: CDI water is the daily average exposure of drinking water, mg/(kg d); TCRe is the daily average exposure of drinking water, mg/(kg d); TCRb is the daily average exposure of skin washing route, mg/(kg d).
Calculation of exposure of drinking water route:
Study on the protection and sustainable utilization of water resources under changing environmental conditions
See table 12.39 for the meaning of each factor in the formula.
Calculation of exposure through skin contact route:
Study on the protection and sustainable utilization of water resources under changing environmental conditions
See table 12.39 for the meaning of each factor in the formula.
Study on the protection and sustainable utilization of water resources under changing environmental conditions
See table 12.38 for the meaning of each factor in the formula.
Table 12.38 Parameter Table of Groundwater Pollution Health Risk Assessment Model
Exposure period refers to the time when human body may be exposed to soil characteristic pollutants under a specific land use mode. Referring to the relevant reference values formulated by the national environmental protection departments of the United States and Canada, the exposure period in residential land mode is defined as 70 years, and the exposure frequency in industrial and residential land mode is defined as 365 d/a. For industrial and residential land, it should be ensured that there will be no major health risks after lifetime (70 years) exposure to soil pollutants. Considering that different behavior patterns of children and adults may lead to different exposures to contaminated soil, the exposure amounts of children during exposure period (1 ~ 6a) and adults during exposure period (7 ~ 70a) were calculated respectively. Daily soil oral intake of children and adults refers to the default values of US Environmental Protection Agency and relevant states (USEPA,1996; NMED, 2004). Because the carcinogenic effect of human exposure to characteristic pollutants in soil is lifelong cumulative effect, the exposure dose in a certain exposure period is average in the life span, and the average life span is defined as 70a(25550 d). According to the existing research and data in China, the average weight of children aged 0-6 in China is 13.6kg, and the average height is 93cm. The average weight of adults is 60kg and the average height is 163cm.
12.6.2.2 evaluation coefficient
The selection of groundwater pollution risk assessment factors in this work refers to the initial value specified in Appendix A of Technical Guidelines for Risk Assessment of Contaminated Sites (draft for approval) and the factors detected in this work, namely methyl tert-butyl ether, benzene, toluene, ethylbenzene, m-p-xylene, o-xylene, naphthalene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene and acenaphthene.
12.6.2.3 Analysis of evaluation results
Input the key parameter values into the mmSOILS model, and calculate the health risk value of groundwater pollution in the site (Table 12.39, Table 12.40).
Table 12.39 Health Risk Assessment Results of Deep Groundwater Pollution in Investigation Area
Table 12.40 Health Risk Assessment Results of Shallow Groundwater Pollution in Investigation Area
(1) Analysis of Groundwater Pollution Risk Assessment Results
As can be seen from the above table, the total health risk value of groundwater at different monitoring points in the investigation area is between 0 ~ 3. 17× 10-4, which is higher than the recommended value of human health risk of the US Environmental Protection Agency (EPA) and the upper limit of the risk level that the EPA thinks can be tolerated when repairing contaminated sites. Therefore, the groundwater in some areas of the investigation area needs to be repaired and treated immediately.
At the same time, in-depth analysis shows that the total health risk value of deep groundwater in the investigation area is between 0 ~1.03x10-7, which is less than the recommended value of human health risk of the US Environmental Protection Agency 10-6. Therefore, it is not necessary to repair and treat the deep groundwater in the investigation area.
The total health risk of shallow groundwater in the investigation area is between 8.2/kloc-0 /×10-10 ~ 3.17×10-4. Among them, QS- 1 and QS-2 are located in the gas station area, which is greater than the recommended value of human health risk of the US Environmental Protection Agency (10-6). In addition, QS-3, which is greater than the upper limit of the risk level of contaminated site remediation considered by the US Environmental Protection Agency 10-4, is also located in the gas station area. All points outside the gas station site are less than the recommended value of human health risk of the US Environmental Protection Agency (10-6). To sum up, the shallow groundwater in the gas station area in the investigation area needs to be repaired urgently.
(2) Risk analysis of groundwater pollution.
Comprehensive analysis of the groundwater pollution risk assessment results of five water samples from three monitoring points in the gas station site (Figure 12.55 ~ Figure 12.59) shows that the groundwater pollution risk in the gas station site can be divided into two characteristics:
Figure 12.55 QS Pie Diagram of Groundwater Pollution Risk Structure-Gas Station 1 Monitoring Hole (water sample SYQS-0 10)
Figure 12.56 Pie Diagram of Groundwater Pollution Risk Structure in QS-2 Monitoring Hole of Gas Station (water sample SYQS-009)
The first one is represented by QS- 1 and QS-2, and its main pollution risks are as follows: the pollution risks of groundwater are mainly methyl tert-butyl ether (25.2% ~ 48.6%) and benzene series (5 1.4% ~ 74.8%), and its polycyclic aromatic hydrocarbons are polluted.
The second type is represented by QS-3, and its main pollution risk feature is now. The pollution risks of groundwater are mainly manifested in methyl tert-butyl ether (pollution risk accounts for 37.6% ~ 42.9%), benzene series (pollution risk accounts for 12.4% ~ 24.5%) and polycyclic aromatic hydrocarbons (pollution risk accounts for 37.9% ~ 24.5%).
Figure 12.57 Pie chart of groundwater pollution risk structure of QS-2 monitoring hole in gas station (water sample SYQS-0 19)
Figure 12.58 Pie Diagram of Groundwater Pollution Risk Structure in QS-3 Monitoring Hole of Gas Station (water sample SYQS-008)
Figure 12.59 Pie chart of groundwater pollution risk structure of QS-3 monitoring hole in gas station (water sample SYQS-0 18)