Mercury is a global pollutant that has attracted widespread attention due to its persistence, concealment, and ease of migration. As the main setting for human production and life, urban ecosystems play significant roles in the global mercury cycle. Urban vegetation also plays an important role in regional mercury cycles. In this study, several common tree species in the green vegetation of Changchun were used as research objects to examine the mercury pollution characteristics of leaf litter and the surrounding soil. In this investigation, 100 sampling sites were set up in Changchun City to collect leaf litter and the surrounding topsoil. An RA-915⁺ Hg analyzer was used to determine the total mercury concentration levels. The results showed that content levels of mercury in plants ranged between 0.0133 and 0.1945 mg/kg, and different species displayed varying levels of mercury accumulation. For example, the content of mercury in Pyrus ussuriensis Maxim. was found to be 0.0755 mg/kg higher than that in the other examined subjects. It was also determined that the plant mercury concentration levels were the highest in the older industrial zones, while the lowest mercury levels were found in the new economic development zones. Furthermore, the plant mercury levels of the roadside areas were higher due to vehicle pollution discharge. Regarding the mercury pollution levels of the surface-layer soil, the soil of old industrial zones’ surface layers had higher levels of mercury pollution than the other tested sites. However, no notable connection was observed between the mercury concentration levels of the vegetation and those of the soil. This study’s results revealed that the mercury pollution of plants in Changchun City is not severe. The mercury levels in the industrial zones were graded as moderate, and those in the other regions were graded as low.

Among human activities, coal mining and the combustion of fossil fuels are important sources of mercury in the environment. Research on mercury pollution in coal mining areas and surrounding cities, especially in densely populated areas, has always been at the forefront of this research field. In order to study the characteristics of environmental mercury pollution in small and medium-sized coal mining areas and surrounding towns in China, this study selected the main urban area of Jiutai District, a typical mining town in the Changchun City circle industrial base in northeast China, as the research object. In this study, the geo-accumulation index (I_geo) was used to study the soil mercury pollution degree in Jiutai District, the potential ecological risk index (Er) was used to evaluate the potential ecological risk of soil mercury in the study area, and the human exposure risk assessment model was used to evaluate the non-carcinogenic risk of soil mercury to the human body. The results showed that 32% of the soil samples in the study area had a higher mercury content than the regional soil background value of Jilin Province (0.04 mg·kg⁻¹). According to the I_geo, 19% of the sample sites in the study area were polluted (index > 0). In general, the soil mercury pollution level in Jiutai District is low, and the polluted areas are mainly concentrated in the northeast of the study area. The Er of the soil mercury in the study area ranged from 7.2 to 522.0, with 32% of the sampling sites having a moderate or above potential ecological risk (Er > 40), and the potential ecological risk level of the soil mercury was higher in the northeast of the study area. The non-carcinogenic risk index (HQ) and total non-carcinogenic risk value (HI) of the soil mercury were all far less than 1, indicating that soil mercury pollution in the study area did not harm the health of local adults. The oral ingestion of soil mercury is the main form of human exposure to mercury.

As a typical industrial city in northeastern China, the environmental conditions of the soil in Changchun City face high ecological risks. In the present study, in order to more fully understand the characteristics of the soil mercury content and its related health risks in the main urban areas of Changchun City, the pollution degrees were evaluated using the data of land accumulation indexes (Igeo), potential ecological risk indexes (Er), and health risk assessment methods. The mercury content (TSM) levels in the urban soil, along with the atmospheric mercury content (TGM) levels, were analyzed. The results showed that the mean value of the mercury content in the soil in Changchun City was 0.0569±0.103 mg/kg, and the concentration range was between 0.0052 and 1.3240 mg/kg. It was found that the mercury content levels in nearly 70% of the soil samples exceeded the background value of soil (0.040 mg/kg). In addition, the atmospheric mercury concentration at 0 cm was determined to be directly related to soil mercury content (P = 0.000532). In addition, the atmospheric mercury content of 0 cm was observed to be positively correlated with the distribution of the atmospheric mercury content at 100 cm (P = 0.000524). The mercury content levels in the soil were found to vary from different directions, with the mercury content found to be the highest in the southeastern section of the city. However, there were no significant differences in the mercury content of any direction. The Igeo showed that 25.0% of the sample points were polluted. The unsanitary areas were mainly concentrated in the southwestern and southeastern sections of the city. The mercury content levels in the soil of Changchun City ranged from pollution-free to moderate pollution levels overall. The Er indicated that the potential ecological risk level was high in the northwestern and southeastern sections of Changchun City. However, the soil mercury levels in Changchun City presented a low level of ecological risk overall. The average values of the non-carcinogenic risks (HQ) and the total non-carcinogenic risk assessment indexes (HI) in all directions within Changchun City were determined to be far less than 1. Therefore, it was concluded that the soil mercury levels were not potentially harmful to human health.

The mercury that is released from the centralized treatment of municipal solid waste is an important source of atmospheric mercury. We chose the main urban area of Changchun as a representative area. Environmental factors such as total mercury content, temperature, wind speed, and other factors were measured in samples from the trash cans of two types of collection points (trash cans and garbage stations), the topsoil under the selected trash cans, and the ambient air above the selected trash cans. The potential ecological risks of mercury pollution were evaluated. The results showed that the mercury content levels of all sample types in the refuse transfer station were higher than the garbage cans and there were no significant differences observed between soil surface mercury and garbage cans. The mercury content levels in the atmosphere and the surface soil at the garbage collection points were found to increase along the cascade relationship of the garbage collection. However, there were no correlations observed between the atmospheric mercury content levels and the surface soil mercury content levels with the attachments and the sum of the former two. There were no correlations observed between surface soil and the attachments, or among the attachments, surface soil, and the atmospheric mercury content levels. The mercury content levels in the attachments, surface soil, and atmosphere of the garbage collection points in the study area were negatively correlated with the loop lines. Meanwhile, the potential ecological risk indexes of the garbage cans and garbage stations were found to be high. The chronic non-carcinogenic risks of mercury to children and adults were determined to be very low. The risks of mercury to children were higher when compared with adults. The highest non-carcinogenic risks of mercury pollution were determined to be within the central area of Changchun.