Source apportionment and spatial distribution of heavy metals in atmospheric settled dust of Ulaanbaatar, Mongolia.

Atmospheric settled dust study was conducted with the purpose of to determine the source of heavy metal elements (As, Co, Cr, Cu, Ni, Pb, and Zn) in airborne dust from Ulaanbaatar using the multivariate analysis and spatial distribution mapping by geographic information system (GIS) with the systematic grid. A total of 57 dust samples were collected from the impervious surfaces at 2-4 m above the ground in January of 2020. The mean concentrations of heavy metals were increasing order of Co-10.4 ± 1.3 mg/kg > As-16.5 ± 5.9 mg/kg > Ni-21.3 ± 3.3 mg/kg > Pb-51.7 ± 26.4 mg/kg > Cu-65.5 ± 23.6 mg/kg > Cr-70.2 ± 18.7 mg/kg > Zn-571.3 ± 422.8 mg/kg. In terms of multivariate analysis, we used Pearson's correlation, principal component analysis (PCA), and hierarchical cluster analysis (CA). Three principal components, which are eigenvalues higher than 1, were determined accounting for 70.5% of the total variance by PCA. As a result, PC1 38.5% (As, Cr, Cu, and Ni), PC2 17.3% (Pb and Zn), and PC3 14.7% (Co and Pb) are attributable to coal combustion, vehicle exhaust emission, and resuspension of soil particles, respectively. The results of correlation analysis and CA were fairly in agreement with PCA. The spatial distribution maps of heavy metals were revealed in the downtown in which 40 covered sampling sites with about 700m intervals. In the spatial distribution mappings, generally, the southern part of the mapping area was higher concentrations of heavy metals. An increment of heavy metals concentration was presented for As, Cr, Co, and Ni with their similar trend in the southwestern part of the mapping. Besides, another trend for the distribution of the high concentrations of Cu and Zn was observed in the south and southeast parts. In terms of Pb, it had no noticeable pattern of distribution; however, a high spot was presented in the southwest part of the map.

Contamination and Health Risk Assessment of Heavy Metals in the Soil of Major Cities in Mongolia.

Using the case of Ulaanbaatar, Erdenet, and Darkhan cities from Mongolia, the study aimed to assess the contamination level and health risk assessment of heavy metals (As, Cr, Pb, Ni, and Zn) in urban soil. A total of 78 samples was collected from a variety of functional areas. The geoaccumulation index (Igeo) and integrated pollution index (IPI) were used in pollution assessment, while the health risk was scored using a hazard quotient (HQ) and health index (HI) for non-carcinogenic heavy metals, as well as a lifetime average daily dose (LADD) for carcinogenic heavy metals. The results show that the concentration of heavy metals in the soil samples taken from Darkhan city, which presented "uncontaminated" values in terms of Igeo for all metals, was relatively lower than other cities within the contamination assessment. Furthermore, the Igeo value signified "uncontimated to heavily contaminated" soil in the Ulaanbaatar and Erdenet cities. Typically, as for the IPI that observed similar trends with Igeo, the mean IPI values in Ulaanbaatar, Erdenet, and Darkhan were 1.33 (moderate level of pollution), 1.83 (moderate level of pollution), and 0.94 (low level of pollution), respectively. In terms of the assessment of potential health risk, there was a particular or different level of ingestion, dermal contact, and inhalation exposure pathway for human health. Among these three different pathways, the ingestion was estimated by the main contributor for health risk. Each value of HQ and HI indicated that soil heavy metals of studied cities were at a safe level (<1) or had the absence of a significant health risk there. In addition, the potential health risk for children was greater than for adults, where heavy metal values of HI for children had a high value compared to adults. We estimated carcinogenic risks through the inhalation exposure, and as a result, there were no significant risks for human health in the studied cities from three elements (As, Cr, and Ni).