[Pollution Characteristics and Risk Assessment of Heavy Metals in Surface Dusts and Surrounding Green Land Soils from Yellow River Custom Tourist Line in Lanzhou].

In order to investigate the contamination levels of dust and its surrounding green land soil heavy metal pollution and potential ecological and health risks in the scenic areas of urban waterfront parks, the gardens, squares, and theme parks of the Yellow River Custom Tourist Line in Lanzhou were selected as the research area, using 27 dust samples and 26 soil samples from its surrounding green lands. The contamination characteristics and potential ecological risks of eight heavy metals (Cr, Ni, Cu, Zn, As, Cd, Hg, and Pb) were evaluated using the geo-accumulation index (Igeo), single-factor pollution index (Pi), Nemerow integrated pollution index (PN), and improved potential ecological risk index (RI). The human health risk assessment was also evaluated using the exposure risk model. The results showed that the average concentrations of the other heavy metals in the surface dusts were higher than the background values of Gansu Province and Lanzhou City, except that the As mean concentrations in the surface dusts and the surrounding green land soils were slightly lower than the Gansu Province background values. For its surrounding green land soils, the mean concentrations of the other heavy metals (Cu, Zn, Cd, Hg, and Pb) exceeded the soil background values of Gansu Province and Lanzhou City, whereas the Cr and Ni mean concentrations were lower than their corresponding soil background values of Gansu Province and Lanzhou City. The geo-accumulation and single-factor pollution indices demonstrated that a slight to moderate pollution of Cr, Cu, Zn, Cd, Hg, and Pb occurred in surface dusts, and Cu, Zn, Cd, Hg, and Pb appeared in varying degrees of contamination levels in its surrounding green land soils. The Nemerow integrated pollution index analysis manifested that the overall contamination status of the study areas was between slightly and heavily polluted. The potential ecological risk index suggested that Cd and Hg were recognized as significant pollutant elements and that the RI of the other heavy metals were all below 40, presenting slight ecological risk. The health risk assessment indicated that ingestion was the dominant exposure pathway for heavy metals from the surface dusts and the surrounding green land soils, and no carcinogenic and noncarcinogenic risks posed threats to adults and children.

The trade-offs and synergies of the ecological-production-living functions of grassland in the Qilian mountains by ecological priority.

Grassland degradation has caused increasingly prominent conflict between ecological environment conservation and socioeconomic development in the Qilian Mountains, China. How to effectively trade-offs and synergies to ecological and socioeconomic is essential to achieving the sustainable development of the grassland ecosystem. However, few studies have addressed the trade-offs and synergies of grassland ecosystem services in terms of coupling the natural ecosystem and the socioeconomic system. Therefore, we constructed an index of the analyzed trade-offs and synergies of grassland ecosystem services from the perspective of "ecological-production-living" functions (EPLFs) and analyzed the spatial-temporal characteristics of grassland EPLF trade-off and synergy relationships based on the data from the implementation of three conservation policies in the Qilian Mountains from 2003 to 2020. The results showed evident spatial and temporal differentiation of the grassland EPLFs. The ecological function was consistent with the production function, trending upward initially and then decreasing. The living function showed a trend of continuous increase. The spatial pattern of grassland EPLFs showed that the northwest and southeast were more active than the middle of the Qilian Mountains, and the regional gradient difference was apparent. The trade-off and synergy relationships of grassland EPLFs have obvious spatial correlations as well; spatial differences were evident under different conservation policies. With national park construction, the synergistic relationship gradually weakened and the trade-off relationship gradually strengthened. These results suggest that the policy of ecological priority increased trade-offs and reduced synergies among EPLFs was not conducive to coupling and coordinating grassland EPLFs for development in the Qilian Mountains. Our study also demonstrates that maintaining moderate grassland grazing pressure and the appropriate number of herdsmen is crucial to sustainably develop the grassland ecosystem in the Qilian Mountains, and further research into coupling mechanisms for grassland EPLFs is needed to reduce trade-offs and increase synergies with grassland ecosystem services.

Accumulation, fractionation and health risk assessment of fluoride and heavy metals in soil-crop systems in northwest China.

Untreated industrial sewage and domestic wastewater irrigation has led to agricultural soil-crop system contamination by heavy metals and fluoride in Dongdagou and Xidagou stream basins, Baiyin city, China. A total of 36 pairs of soil and wheat samples (roots, stalks, leaves, husks, and grains) and 42 pairs of soil and maize samples (roots, stalk1, stalk2, stalk3, leaves, husks, corncobs and grains) were collected from Dongdagou and Xidagou stream basins to examine the accumulation, fractionation, correlation of heavy metals and F in soil-crop systems. Risks posed by heavy metals and F in this system to human health was also assessed. The total contents of F and heavy metals (Cd, Cu, Pb, Mn Zn, Cr and Ni), as well as the fraction distribution in soil, were determined. The total contents of F and heavy metals in crop tissues were also determined. The results indicated that the average contents of Cd, Cu, Pb, Mn Zn, F and Cr in Dongdagou and Xidagou stream basins exceeded the soil background value. Heavy metals and F more easily accumulated in the male inflorescence of maize. Correlation analysis showed that content of water soluble F positively were correlated with the contents of Cd, Cu, Pb, Mn Zn, Cr and Ni in exchangeable and carbonate fractions (P < 0.05). Stepwise discriminant analysis showed that the combined stresses of soil total Cu and Ni accounts for 100% effect on water soluble F accumulation in soil and crop roots. The hazard index indicated that noncancerous risk is likely to occur through maize grains and wheat grains consumption by children and adults.

Accumulation, fractionation, and risk assessment of mercury and arsenic in the soil-wheat system from the wastewater-irrigated soil in Baiyin, northwest China.

Wastewater irrigation can increase metal concentrations in soil and wheat, thereby posing metal-associated health risk via food ingestion. We investigated levels of mercury (Hg) and arsenic (As) in roots, husks, stems, leaves, and grains of wheat and their fractionations in farmland soil from Baiyin City, an industrial and mining city, northwest China. Results show that the mean concentrations of Hg in soils from Dongdagou and Xidagou stream in Baiyin were 8.5 times and three times higher than local soil background values, respectively. Those of As were 4.5 times and 1.6 times higher, respectively. Most Hg and As were mainly accumulated in wheat leaves. The spatial distributions of As in soils and grains exhibit a very similar pattern, which suggest that As pollution in soils might be predicted by its level in wheat grains. Residual fractions for Hg (RES-Hg) and As (RES-As) are the highest compared to other fractions, indicating weak mobility of Hg and As in soil. The crop oral intake hazard quotients of both Hg and As for children were approximately two times higher than that for adults, indicating that children have higher exposure risks to Hg- and As-contaminated wheat. The crop oral intake was the main route of exposure causing non-carcinogenic and carcinogenic risk for local residents.

[Speciation distribution and risk assessment of heavy metals in sediments in suburban outfall of industrial oasis region].

The speciation distribution and potential environmental risk of Cu, Zn, Cd, Pb, Ni, Cr in sediments in suburban outfall of industrial oasis region, Baiyin City were studied by Tessier sequential extraction method, correlation analysis, enrichment factor (EF) and risk assessment code (RAC). The results indicated that, the average concentration of heavy metals in sediments samples of Dongdagou and Xidagou streams exceeded the background levels in Gansu Province, with Cr, as an exception. The enrichment factor suggested that the enrichment of Cd in sediments of Dongdagou and Xidagou streams were very serious, which posed a strong pollution level. Furthermore, the analysis of chemical speciation indicated that Zn, Ni, and Cr in sediments of Dongdagou stream were mainly dominated by the fraction of residual, the existence of Cu and Cd was mainly in organic forms, while Pb was composed mostly by its Fe-Mn oxides fraction; Pb in sediments of Xidagou stream existed by Fe-Mn oxides fraction, other metals mainly appeared with the residual fraction. The risk assessment code (RAC) showed that the risk level of heavy metals in sediments of Dongdagou stream descended in the order: Ni > Cd > Pb > Cu > Zn > Cr, Ni posed a highest risk level. The risk level of heavy metals in sediments of Xidagou stream decreased in the order: Pb > Cd > Ni > Cu > Zn > Cr, Cd, Pb and Ni posed a highest risk level.