[Bioaccumulation and Translocation Characteristics of Heavy Metals in a Soil-Maize System in Reclaimed Land and Surrounding Areas of Typical Vanadium-Titanium Magnetite Tailings].

A total of 86 soil samples, 86 corn kernel samples, 50 tailings samples, and 33 ore rock samples were collected in reclaimed land and surrounding areas of typical vanadium-titanium magnetite tailings located in the Chengde Central Region and analyzed for 14 elements (P, Fe, Cu, Ni, Cd, Cr, Pb, Zn, Hg, Ti, Mn, and Mo) and speciation of heavy metals. This study investigated the bioaccumulation and translocation characteristics of heavy metals in a soil-maize system based on a descriptive statistical analysis, a geological accumulative index, bioconcentration factors, and a redundancy analysis. The results showed that the average accumulation index of surface soil followed an order of P > Cu > Fe2O3 > Cr > Ti > V > Ni > Mn > Cd > Zn > Mo > As > Pb > Hg, while the accumulation level of heavy metals was generally categorized as either no accumulation or moderate accumulation. Compared to China's soil environmental quality standard risk screening values (GB15618-2018), the over-standard rates of Cr and Cu were 2.32% and 1.16%, respectively. The content of Fe, Ti, As, Pb, and Mn in the corn kernels of the tailings and surrounding areas was relatively high, and the content of Mo, Ni, Cu, Zn, Cd, and Cr in the control area was relatively high. The over-standard rates of Ni, Zn, and Cu in the corn kernels were 13.61%, 13.23%, and 5.17% respectively, according to China's national food safety standard limits for contaminants in food (GB 2762-2017). The bioconcentration factors of Fe, Ti, As, Pb, and Mn in the corn kernels of the tailings and the surrounding areas were relatively higher, while the bioconcentration factors of Mo, Ni, Cu, Zn, Cd, and Cr were lower than in control area. The bioactive components of Cd accounted for 50.17%, which was the highest, followed by Ni, Zn, and Cu with average ratios of 13.61%, 13.23%, and 5.17%, respectively. Compared to the control area, the Pb, As and Hg elements in the soil samples of the reclaimed land showed a lower total amount but a higher bioavailability content and soil pH value, while the Cu and Hg elements showed a higher total amount but lower bioavailability content and soil pH value. These differences in total heavy metal concentrations, bioavailability amounts, and soil pH values made the bioconcentration intensity of As and Pb in the tailings reservoir and surrounding area relatively higher. When studying the ecological risk of heavy metal pollution or determining the remediation target value of reclaimed land in a mine tailings reservoir and the soil around the mine area, the bioavailable state limit of heavy metals should be should be taken into account as the evaluation standard.

[Source of Groundwater Nitrate in Luanping Basin Based on Multi-environment Media Nitrogen Cycle and Isotopes].

The multi-environment media of water, surface soil and vadose zone soil samples were collected in the upstream of Miyun Reservoir, in the Luanping Basin of Chengde City, Hebei Province. The aim was to identify the pollution source, ratio, spatial distribution, migration, and transformation characteristics of nitrogen in groundwater. Hydrogeochemistry, soil total nitrogen, and dissolved nitrate nitrogen of vadose zone soil analysis and a multi isotope tracer technique of δ15 N-NO3 and δ18O-NO3, δ34S-SO4 and δ18O-SO4, δ14 C, combined with land-use type analysis and geostatistics, were used in the study. The results showed that nitrate was the main form of nitrogen in the groundwater of the Luanping Basin. The NO3- concentration of groundwater was significantly correlated with the land-use types of residential land and cultivated land where the nitrate pollution of shallow groundwater was mainly distributed. Of the groundwater samples, 13.79% exceeded the National Standard Ⅲ for Groundwater (GB/T 14848-2017) of NO3- concentration value, while the excess multiple was 1.04-3.86, and 37.93% of the groundwater samples exceeded the World Health Organization NO3- concentration standard value. The excess multiple was 1.08-6.83. The spatial variation of groundwater NO3- concentration, soil total nitrogen and surface soil dissolved nitrate nitrogen of vadose zone was affected by the combination of natural structural factors and anthropogenic factors. The source of groundwater nitrate was mainly from livestock manure and domestic sewage, followed by chemical fertilizer leaching. The nitrogen cycle in the aeration zone-groundwater-dominated nitrogen circulation in the groundwater runoff area of the piedmont basin was nitrification. These findings are highly significant for the prevention and remediation of groundwater pollution when viewing the basin system as an independent unit, and for studying the sources and fate of nitrate pollution in the water environment.

[Determination of Heavy Metal Geochemical Baseline Values and Its Accumulation in Soils of the Luanhe River Basin, Chengde].

A total of 351 surface soil samples (0-20 cm) were collected from the Luanhe River Basin in Chengde City (a typical area of concentrated mineral resources) and analyzed for 12 heavy metals (Cu, Ni, Cd, Cr, Pb, Zn, Hg, V, Ti, Mn, As, and Co). The geochemical baseline values of the heavy metals were determined using the reference element method and the cumulative frequency curve method. Furthermore, the spatial structure and distribution characteristics of the heavy metals were assessed based on PCA and geostatistical analysis. The accumulation of heavy metal pollution in different types of soil and in association with different land use patterns was also evaluated using a geological accumulative index. The results showed that the geochemical baseline values of V, Ti, Cd, Pb, Mn, and Co in the surface soils of the Luanhe River Basin were higher than their background values for Hebei Province. In contrast, the geochemical baseline values of As, Zn, Cr, Cu, Ni, and Hg were lower than their background values. The average accumulation index of the surface soils followed the order of Cd > Pb > Cu > Ti > Mn > Zn > Cr > Ni > Co > V > Hg > As. More than 80% of the soil samples were categorized as having no accumulation or moderate accumulation of Pb, Ti, V, As, and Co, while over 70% of the soil samples were categorized as having no accumulation or moderate accumulation of Hg, Mn, Ni, Cu, As, Cd, and Cr. With respect to different soil types, the average accumulation index of heavy metals followed the order of fluvo-aquic soil>cinnamon soil>brown soil. With respect to land use types, the accumulation index of heavy metals followed the order of industrial and mining land > shrub forest land > agricultural land > woodland and grassland. The accumulation of Pb and Cd in the surface soils of agricultural land was relatively high in comparison to the other elements, with 27.69% and 25.38% of the samples being above the moderate accumulation level, respectively. The iron group elements Ti, V, Co, Ni, and Cr are likely to derive from naturally high geological background sources, while the spatial patterns of Cd, Pb, Zn, Mn, Cu, and As were associated with the combination of parent material and anthropogenic inputs. The accumulation of Hg was mainly influenced by human activities.