Soil organic matter in industrial and mining lands and its impact on health risk assessment results of volatile organic compounds (VOCs) in China.
Authors: Gong Yiwei , Yang Kaiming , Quan Weici , Ai Yadi , Cheng Hongguang , Yang Kai 
Published: March 2024

In China, the escalation of the need to redevelop contaminated land has emerged as a significant ecological predicament owing to the likelihood of human exposure to contaminations, specifically volatile organic compounds (VOCs). The US Toxic Substances and Disease Registry have identified ten VOCs compounds among the top 100 priority controlled toxic substances. The identification of potential exposure issues and subsequent on-site assessment are critical considerations in determining Soil Screening Levels (SSLs) for VOCs based on health risks. In 2018, the Ministry of Ecology and Environment of the People&#8217;s Republic of China established Nationally unified health-based Soil Screening Levels (NSSLs) and Control Levels (NSCLs) to screen and control land contamination risks (GB/T 36600-2018).
The SSLs for various VOCs were found to be unique for most contaminated sites. Soil remediation initiatives have been implemented in economically developed regions worldwide, particularly for VOCs sites contaminated. However, SSLs are frequently established at levels that are either inadequate or excessive, resulting in incomplete or excessive soil remediation. Health risk-based SSLs are typically derived through models that integrate default exposure assumptions and toxicity data. Related models algorithm employ three categories of parameters: scientific, regulatory, and geographic parameters (soil physical and chemical properties, and building parameters).&#160;The variability in SSLs across different areas can be attributed to discrepancies in vapor intrusion algorithms and alert/child exposure duration. Additionally, there exists a degree of uncertainty in the predict on of VOC concentrations in soil vapor, which may be influenced by various parameters such as soil organic matter (SOM) content, soil type, soil moisture content, soil particle density, and soil bulk density. These factors can potentially impact the results of health risk assessments and the determination of SSL values for VOCs.
Soil undergoes chemical decomposition, microbial utilization and degradation that can alter the composition and content of SOM. Anthropogenic factors can also trigger the release of diverse types of VOCs from soil. The characteristics and content of SOM in contaminated sites are subject to modification by a range of factors, including natural phenomena such as temperature, humidity, and leaf litter, as well as anthropogenic activities such as artificial fertilization, land management practices, and the presence of contaminations. Given China&#8217;s extensive land area and diverse soil types, the determination of SOM content in contaminated sites can serve as an effective means of supporting regional soil environmental risk management and control.
We hypothesized that SOM content varies considerably across regions, soil depths, and industries. With a negative correlation observed between SOM content and economic development, sampling soil depth, and chemical industry density, respectively. The present study aimed to optimize the value of SOM in the risk assessment model, thereby facilitating the refined risk assessment of VOCs among the population. The study obtained site-specific SSLs for main VOCs based on health risk. Specifically, the study sought to (1) investigate the temporal and spatial variations of SOM in industrial and mining lands in China, and (2) explore the impact of SOM on VOCs health risk assessment and calculating SSLs values.&#160;