Health Risk Assessment Of Pollution Sites Based In Specific Residential Land Scenarios

Environmental investigation and risk assessment should be conducted when contaminated sites in cities are developed and used again.According to the the Technical Guidelines for Soil Contamination Risk Assessment of Construction Sites(HJ 25.3-2019)(the Guidelines),the health risk assessment process of contaminated sites is mainly based on the exposure routes of pollutants that may act on the human body,and model calculations were conducted to obtain the impact of site pollutants on human health hazards.Currently,in the assessment process,the programmatic assessment was only carried out for environmental pollution characteristics and site categories,such as concentration and spatial distribution of pollutants,and the exposure routes of pollutants in soil were analyzed to assess the hazards of pollutants to humans.The assessment conducted in this context fails to fully integrate the actual building characteristics and population served under various land use types in China,which often leads to inconsistencies in the selection of exposure routes and exposure parameters,and ultimately leads to deviations in the calculated wind assessment results.For example,under specific residential uses such as villas,the scenario of residents consuming homegrown crops occurs,and pollutants may be exposed through crop absorption or attachment,which directly affects the results of site health risk assessment,remediation goals and costs,and may lead to the risk of non-safe use even after programmatic assessment according to the guidelines.This thesis mainly discusses the activity patterns,exposure scenarios,assessment models of edible self-produced crops,and soil health risk assessment of contaminated sites in specific residential land scenarios.The main research contents and achievements are as follows:(1)This thesis takes Hunan as an example and selects four freestanding residential buildings and three high-rise residential communities in Changsha with a time span for field investigation.Through the investigation,the differences in planting sites,methods,soil sources,and crop types among residents in different living environments were summarized.Due to the limited planting conditions of high-rise buildings,pollutants are not easily exposed.The behavior of the residents of detached houses to grow crops is more likely to cause pollutants to enter the human body through the crops and endanger health,and thus establishes the exposure scenario under that particular type of residential planning.(2)According to the building structure characteristics and population characteristics of specific residential land use planning,the exposure model suitable for the route of consuming home-grown crops was established by comparing and selecting the international models for calculating the exposure amount considering the consumption of contaminated home-grown crops,combining the latest progress of relevant domestic research and the arithmetic form of the Guidelines,some parameters were modified locally to construct the research and assessment model.(3)The contaminated sites containing heavy metals,SVOCs and VOCs in soil were selected as representative research objects,and site investigation and pollutant distribution characteristics analysis were conducted.Based on the results of the contamination survey of the site,the risk assessment was conducted separately using the Guideline model and the research model,and it was found that the carcinogenic risk of pollutants had increased to different degrees,among which α-HCH and γ-HCH were the most significant,which is about 80.1 times and 3.1 times that of the evaluation results of the Guidelines,respectively.(4)In the evaluation of the guideline model,oral intake is the main source of the carcinogenic risk of arsenic to residents,with the contribution rates reaching 86%,8%and 5% respectively;the carcinogenic risk of benzene mainly comes from the inhalation of indoor air from the lower soil.The contribution rate is as high as 96%;the carcinogenic risk of organochlorine pesticides to residents mainly comes from direct exposure routes,including oral intake and skin contact routes,of which oral intake is the most critical.After the evaluation by the research model,the contribution rate of the exposure route of edible self-produced crops to the carcinogenic risk of different pollutants of concern varies.The main source of exposure to the carcinogenic risk of HCHs to residents has changed from oral intake to consumption of self-produced crops.The change in the contribution rate of the hazard quotient is consistent with the change in the contribution rate of the carcinogenic risk.The main exposure route is the consumption of self-produced crops,and its safety risk cannot be ignored.(5)Comparing different pollutants,there is a big difference in the calculated amount of site pollution remediation using the research model and the guideline model to obtain the site remediation target value.If the restoration target value calculated according to the guideline standard,the result is too conservative,and there is still the risk of unsafe use of the contaminated site.