Evaluation on the risk controlling value of urban soil organic pollutants based on land-use planning in China

Land left after urban industrial enterprises relocate is usually planned for various land-use types that can influence human health risks. In China, urban development consists of at least eight land uses: urban residential (UR), public administration/service (PA/S), commercial/service (C/S), industrial, logistics storage, transportation (TR), public utility, and park green space. The (PA/S) type has two classes: PA/S1 includes administrative, cultural relics and historic, foreign affairs, and religious facility lands, with adults the sensitive recipients. Class PA/S2 includes lands related to cultural facilities, education and scientific research, sports, medical, and social welfare facilities, in which children are the sensitive recipients. The UR type has UR 1 and UR 2 classes with and without underground space, respectively. The C/S type has C/S1 and C/S2 classes with and without underground space, respectively. The TR type has TR1, TR2, and TR3 classes which indicate urban road, subway, and traffic hub land, respectively. To the above, we applied conceptual models and exposure pathways of volatile organic compounds and semi-volatile organic compounds. Exposure parameters were investigated for six regions and above eight land uses featuring different soil, climate, and population behavior characteristics: north, east, south, northwest, northeast, and southwest (covering China entirely). Risk controlling values (RCVs) corresponding to a lifetime cancer risk of 10^-6 in this paper were calculated using the C-GAC model introduced by 'Chinese Technical Guidelines for Risk Assessment of Contaminated Sites' with above exposure parameters to determine whether it has potentially significant levels of contamination that may warrant further investigation. Our results revealed two main patterns: (1) our soil risk controlling values for the six regions-north, east, south, northwest, northeast, and southwest-revealed some between-region variability (up to 28%). Hence, for urban contaminated sites in different regions of China, different RCVs should be considered when evaluating possible health risks. (2) The results for the organic pollutants tested across the eight types of land use showed maximum values up to 90 times the minimum value. The greater the risk controlling value of the same pollutant, the less sensitive the site is to that pollutant. Urban road land, traffic hub land, and park green space land are not sensitive to volatile organic pollutants.