[Changes in Concentrations and Pollution Levels of Trace Elements of Floodplain Sediments of Poyang Lake Basin in Recent Twenty Years].

Investigating the pollution conditions of trace elements in the Poyang Lake basin, identifying the pollution sources, evaluating the ecological risks play an important part in formulating the effective strategies for protecting the basin ecosystem. To understand the concentration characteristics, pollution levels, and ecological risks of twelve trace elements (Cd, Hg, Pb, As, Cu, Zn, Cr, Ni, Mn, Sb, W, and Sn) in the floodplain sediments of the five main tributaries in Poyang Lake basin in the past twenty years, we used the enrichment factor (EF) and modified pollution index (MPI) to quantify the pollution levels of the trace elements, and analyzed and discussed the pollution sources in the areas with significant pollution level changes. The results indicated that the concentrations of cadmium, zinc, manganese, tungsten and lead in the floodplain sediments of the Poyang Lake basin during the past twenty years have increased by 134%, 26%, 41%, 25%, and 8%, respectively, and mercury, arsenic, chromium, nickel, antimony, and tin have decreased by 35%, 15%, 22%, 10%, 14%, and 13%, respectively, while copper has not changed significantly. The concentrations of cadmium in the Raohe River, Ganjiang River, and Xinjiang River basins have increased by 331%, 151%, and 107%, while mercury decreased in the Fuhe River, Ganjiang River, and Xiushui River basins by 87%, 41%, and 40%, respectively. The classification results based on the EF indicated that the changes in the pollution levels of trace elements in the Poyang Lake basin were characterized by the aggravation of cadmium pollution and the degradation of mercury pollution, the pollution level of cadmium in the Ganjiang River basin was upgraded to moderate and significant, the pollution level of cadmium in the Le'an River was upgraded to very high, and the pollution level of mercury in the Fuhe River basin was reduced to unpolluted or minimal. The MPI classification results established that the increase in the cadmium pollution had intensified the comprehensive pollution in the Poyang Lake basin, causing the proportion of severely and heavily polluted sites to be raised from 17% to 33%. The MRI classification results also demonstrated that the proportion of very high ecological risk sites have increased from 11% to 22%. The element with the highest MRI contribution rate changed from mercury to cadmium, which was caused by the reduction of the ecological risk level from very high to moderate. The results demonstrated that the significant pollution changes in the trace elements in the floodplain sediments of the Poyang Lake basin were primarily caused by human activities, such as mineral exploitation, smelting, and industrial and agricultural production. Our findings can provide scientific evidence for the prevention and control of river pollution and the optimal management of a watershed ecosystem.

[Geochemical Survey Method of Land Quality in Land Parcel Scale City: A Case Study of the Initial Area of the Xiong'an New District].

In order to evaluate the land quality geochemical survey achievement in the service of the accurate management of urban land resources, the initial area of the Xiong'an New District as urbanization pathfinder in China is chosen as the research subject. The sample points were set by differential classification, and the spatial interpolation accuracy of the soil elements at a plot scale and a quantitative assessment of the consistency of the land plot (pattern spot) prediction evaluation were studied under the conditions of different sampling densities. The regional geochemical variation values randomly distributed on the plane can be reflected quantitatively by differential classification sampling, which can meet the basic demand of the quality attribute of a single plot (map spot) by the accurate management of urban land resources. The spatial variability of soil elements is mostly middle to moderate, and Cd, Cu, Pb, Hg, Se, N, P, and other elements of high spatial variability are affected by human industrial and agricultural production activities. Under the same sampling density, the larger the element variation coefficient, the worse the spatial interpolation accuracy. Although the interpolation accuracy of the same element index is affected by the sampling density, the increase in the sampling density could not identify the continuous component on the structure of the soil element content. The soil environment is clean, and the heavy metal content is lower than the GB15618-2018 standard. The interpolation results are basically consistent with the grading results of the measured values, while the contents of N, P, and K of the nutrient indices vary greatly, and the predicted and measured geochemical grades of the plots (map spot) differ substantially under the influence of factors such as human disturbance and spatial variability. The quantitative evaluation of the six different sampling densities indicates that the 16 points·km-2 sampling density adopted in the geochemical survey and evaluation of urban land quality can satisfy the needs of an accurate control of urban land resources in the study area and similar areas. The research can provide key technologies to support and serve the accurate management of urban land resources for geochemical surveys and the evaluation of land quality in land parcel scale cities.

[Discussion on Key Issues of Geochemical Monitoring of Soil Heavy Metal in Xiong'an New District].

To build a soil environmental quality monitoring network and collect the systematic soil geochemical data of heavy metals before and after the construction of Xiong'an New District(XND), long-term variations in soil heavy metal levels during the XND construction were monitored based on the land quality geochemical survey monitoring data and the geochemical distribution of heavy metals. Parameters such as sampling density, sampling quantity, and sampling period were estimated to construct the geochemical monitoring network, which provides a reference for the future long-term monitoring of soil heavy metal geochemistry in XND. The results indicate that variations in the amount of heavy metals As, Cd, Cu, Hg, and Pb are greater than 36%, while the nugget coefficients of Cd, Cu, and Pb are greater than 75% because of the superposition of manmade sources on the high natural background levels. At the 95% and 90% confidence levels, while the allowable error Δ of the sample mean value is 5%, 10%, and 15% and heavy metals as As, Cd, Cu, Hg,Ni, Pb and Zn is monitored in soil environmental quality monitoring network, the proper numbers in the study area are 1077, 270, 120 and 767, 192, 86, respectively. The minimum detectable change(MDC)of each heavy metal species is between 0.0025 and 2.54 mg ·kg-1. Soil heavy metal monitoring requires different revisit intervals under different annual change rates, but in the study area, revisit intervals of soil monitoring are approximately two years under the current conditions of constant annual change rates.

[Trace Metals Pollution and Health Risks for Planning Area Soils of 193 Chinese Cities].

Urban soils are more easily subjected to modification, especially by contamination because of various human activities, and the environmental problems caused by urban soil pollution have become more prominent. To systematically investigate concentration characteristics, pollution levels, and exposure risks of 13 trace metals in urban soils of planning areas for 193 cities above the prefectural level, located in 31 provinces (autonomous regions and municipalities) of China, levels of pollution in urban soil were evaluated using the geoaccumulation index and integrated pollution index of trace metals, and health risks of residents exposed to urban soils were quantified using the health risk assessment method recommended by the US Environmental Protection Agency (USEPA). The results show that the median concentrations of As, Be, Cd, Co, Cr, Cu, Hg, Ni, Pb, Se, Tl, V, and Zn in topsoils of urban planning areas were 9.25, 2.14, 0.174, 12.4, 68.4, 28.2, 0.095, 27.7, 31.1, 0.29, 0.61, 82.7, and 82.2 mg·kg-1, respectively. Compared with the corresponding urban soil background values, the concentrations of Cd, Hg, and Se changed significantly. The geoaccumulation index (Igeo) values showed that Hg in urban soils of the planning area was the most severe pollutant, followed by Se and Cd, which caused pollution levels of uncontaminated to moderately contaminated levels, while other trace metals were uncontaminated. The Nemerow IPI (IPIN) revealed that the soils in 22 urban planning areas were heavily polluted and 16 urban planning areas were moderately polluted; in addition, the most polluted city in China was Zhuzhou in the Hunan province. The results of health risk assessment indicate that the soils in the five urban planning areas-Chenzhou City, Huangshi City, Zhuzhou City, Xiangtan City, and Longyan City-posed potential non-carcinogenic risks to children, and the major factor triggering risks was ingestion of Pb. To understand the soil pollution status and distribution of contaminated land parcel, it is suggested to carry out detailed investigation in cities with integrated moderate to heavy pollution to establish the list of contaminated land parcel and implement pollution control and restoration.

[Analysis of ecological risk and the content situation of polybrominated diphenyl ethers in sediments from Northeast China River Basin].

To investigate the polybrominated diphenyl ethers (PBDEs) pollution status, sediment samples were collected from major rivers in northeast China. Contents of 41 PBDEs congeners in sediments were measured using GC-NCI-MS. BDE209 was not detected, measured level of total PBDEs (excluding BDE209) ranged from 0.91 to 17.67 ng.g-1 dry weight, the highest concentrations of PBDEs were detected in the sediment samples from upstream and downstream of Jilin City in the Second Songhua River Basin, with 15.86 and 17.67 ng.g-1. BDE207 and BDE47 were the predominant PBDE congeners, with their concentrations accounting for 86. 5% and 76. 6% of the total PBDEs concentration measured in the samples. Each congener content difference was not obvious in other river sediments. PBDEs levels monitored in the present study were compared to those reported recently for districts located at home and abroad, and with ecological risk analysis. PBDEs content is at a low level in sediments of Northeast China River Basin and there is no ecological risk.

[Distribution, sources and ecological risk assessment of polychlorinated biphenyl in sediments from Songhua River Basin].

In order to find out the distribution, source and pollution situation of Polychlorinated Biphenyls (PCBs) in sediments of Songhua River basin, GC-ECD and GC-MS were used to determine the PCBs contents in sediments of Songhua River basin. Regulations of the United States Environmental Protection Agency (EPA), the Canadian Sediment Quality Guidelines (SQG) and the potential ecological risk index (Er) were utilized to evaluate the ecological risk of PCBs in the sediments. The results showed that 2-10 PCBs congeners were detected in the sediments. The total contents of PCBs varied from 0.83 ng x g(-1) to 125.53 ng x g(-1) in sediments of Songhua river basin, 0.83-4.44 ng x g(-1) for Nen River, 12.44-125.53 ng x g(-1) for Second Songhua River, and 1.74-6.25 ng x g(-1) for the mainstream of Songhua River. The highest level of PCBs was detected in sediments of Second Songhua River, which mainly came from pollution sources which are related with industrial products such as paint, insulation materials and the like, and were distributed along the river. While in other rivers, the dominant PCB was Dichlorobiphenyl, which mainly came from the atmospheric deposition. Risk assessment using three methods (EPA, SQG and Er) showed that PCBs in the sediment of the Second Songhua River has already reached the medium to high level of contamination, and PCBs in sediments of other rivers has no ecological risks at the moment.

Profile of organochlorine pesticides in soil cores from some hotspot areas of Beijing, China.

For the valid use of urban land and the safety of public health, an extensive contamination survey of organochlorine pesticides from five soil cores was conducted in the highly urbanized areas of Beijing in China. For topsoils in five soil cores, level of ∑HCHs and ∑DDTs varied from 0.174 to 4,783 ng g(-1) and 0.62 to 57,849 ng g(-1), respectively. The profile in topsoil of cores displayed that levels of pollutants in four soil cores from the urban areas with dense population are higher than that from outskirts. The depth characteristics of pollutants indicated that the level of ∑HCHs and ∑DDTs in BY and WU was close to/below the background value of soil in China (50 ng g(-1)), but those in some soil samples from A, B and ZX core, especially A and B, was above the threshold value for the soil safety (1,000 ng g(-1)). In views of the usage history of the land and profiles of contaminants, the source in A and B probably came from the dumped waste chemical materials in the old chemical factories. The study of soil cores sampled revealed the existence of chemical "time bomb" in urban regions of Beijing. Also, the finding indicated the absolute necessity of assessing the soil quality with the unprecedented land use changes in the big city community.

Mercury contamination in the topsoil and subsoil of urban areas of Beijing, China.

Mercury contamination is a serious problem in Chinese cities. In the present study, mercury contamination was evaluated in topsoil and subsoil samples collected in an urban area of Beijing. The level of total mercury in topsoil ranged from 12.1 to 8,487 ng g(-1), and a significant correlation (R = 0.58145, p < 0.0001) with polycyclic aromatic hydrocarbons was observed. Higher levels were generally observed in the suburbs and urban centers, with the highest levels being observed in the urban centers. The fraction of water soluble, ion exchangeable, Fe-Mn in the oxide-bound and organic phase was 0.78%, 0.18%, 0.25% and 3.42%, respectively. For subsoils, the level of total mercury ranged from 7.0 to 924.6 ng g(-1), and the higher levels were primarily located in the suburbs. This study showed that mercury has possibly affected the environmental quality of soil and groundwater in urban areas of Beijing.