Potentially Toxic Element Pollution Levels and Risk Assessment of Soils and Sediments in the Upstream River, Miyun Reservoir, China.

This study focused on the Chao River and Baimaguan River located upstream of the Miyun Reservoir in Miyun District (Beijing, China). Soil and sediment samples were collected from the river and drainage basin. Total nitrogen, total phosphorus, and six potentially toxic elements including cadmium, zinc, lead, chromium, arsenic, and copper, were analyzed in terms of concentration, potential ecological risk, and human health risk. The average concentrations of the six potentially toxic elements were all below the soil environmental quality standards for China. Cadmium was the most serious pollutant in both soils and sediments, at 2.58 and 3.40 times its background values. The contents of Cd and Pb were very closely related (p < 0.01) to total nitrogen concentrations in both soil and sediment samples. The potential ecological risks posed by Cd in the Chao and Baimaguan River soils were considerable and moderate, respectively. The historical iron ore mining and agricultural activity were identified as the primary sources of potentially toxic element pollution of soil and sediment in the Chao-Bai River in Miyun District. Human health risk assessment indicated that non-carcinogenic risks all fell below threshold values. The total carcinogenic risks due to Cr and As were within the acceptable range for both adults and children. This conclusion provides a scientific basis for the control of potentially toxic element pollution and environmental protection of the Miyun Reservoir in Beijing.

A review of heavy metal pollution levels and health risk assessment of urban soils in Chinese cities.

This study assessed literature-based data for the period 2006-2016 regarding heavy metal (As, Cd, Cr, Cu, Pb, Ni, Zn, and Hg) concentrations in soils from 32 Chinese cities and the associated human health risks. The mean concentrations of the eight metals were lower than the soil environmental quality standards in China, but were much higher than the background values for most cities. The enrichment factor (EF) and geoaccumulation index (I geo) values showed moderate pollution levels, possibly influenced by anthropogenic activity for Cd, Hg, Pb, and Zn. The pollution levels in eastern cities were much higher than those in western cities, and heavy metals concentrations in different types of cities followed the order: industrial based cities > more developed cities > metropoles > underdeveloped cities. The human health risk assessment for heavy metals in most cities indicated that non-carcinogenic risks were within threshold values (HI < 1). The total carcinogenic risk due to As, Cr, and Ni in most urban areas was in excess of 1 × 10-5, but was lower than 1 × 10-4. However, in some cities (e.g., Baoji City, Tiyuan City, and Xuzhou City), Ni and Cr have potential cancer risks for both adults and children. Compared to adults, children could be more seriously threatened by heavy metal contamination in soils. In general, we recommend that Cd, Hg, and Pb are selected as priority heavy metals pollutants that require control in Chinese cities.

Assessments of levels, potential ecological risk, and human health risk of heavy metals in the soils from a typical county in Shanxi Province, China.

A total of 128 surface soil samples were collected, and eight heavy metals, including As, Cd, Cr, Cu, Pb, Ni, Zn, and Hg, were analyzed for their concentrations, potential ecological risks, and human health risks. The mean concentrations of these eight metals were lower than the soil environmental quality standards in China, while they were slightly higher than the background values in Shanxi Province. The enrichment factor, coefficient variation, and potential ecological risk index were used to assess the pollution and eco-risk level of heavy metals, among which, Cd and Hg showed higher pollution levels and potential risks than the others in the studied area. Moreover, multivariate geostatistical analysis suggested that Hg originated mainly from point sources such as industrial emissions, while agricultural activity is the predominant factor for Cd. The human health risk assessment indicated that non-carcinogenic values were below the threshold values. The total carcinogenic risks due to As, Cr, and Ni were within the acceptable range for adults, while for children, they were higher than the threshold value (1.0E-04), indicating that children are facing higher threat to heavy metals in soils. These results provide basic information on heavy metal pollution control and human health risk assessment management in the study regions.

[Dynamic changes in vegetation NDVI from 1982 to 2012 and its responses to climate change and human activities in Xinjiang, China].

Vegetation plays an important role in regulating the terrestrial carbon balance and the climate system, and also overwhelmingly dominates the provisioning of ecosystem services. Therefore, it has significance to monitor the growth of vegetation. Based on AVHRR GIMMS NDVI and MODIS NDVI datasets, we analyzed the spatiotemporal patterns of change in NDVI and their linkage with climate change and human activity from 1982 to 2012 in the typical arid region, Xinjiang of northwestern China, at pixel and regional scales. At regional scale, although a statistically significant positive trend of growing season NDVI with a rate of 4.09 x 10⁻4· a⁻¹ was found during 1982-2012, there were two distinct periods with opposite trends in growing season NDVI before and after 1998, respectively. NDVI in growing season first significantly increased with a rate of 10 x 10⁻4· a⁻¹ from 1982 to 1998, and then decreased with a rate of -3 x 10⁻4· a⁻¹ from 1998 to 2012. The change in trend of NDVI from increase to decrease mainly occurred in summer, followed by autumn, and the reversal wasn't observed in spring. At pixel scale, the NDVI in farmland significantly increased; the NDVI changes in the growing season and all seasons showed polarization: Areas with significant change mostly increased in size as the NDVI record grown in length. The rate of increase in size of areas with significantly decreasing NDVI was larger than that with significantly increasing NDVI, which led to the NDVI increase obviously slowing down or stopping at regional scale. The vegetation growth in the study area was regulated by both climate change and human activity. Temperature was the most important driving factor in spring and autumn, whereas precipitation in summer. Extensive use of fertilizers and increased farmland irrigated area promoted the vegetation growth. However, the rapid increase in the proportion of cotton cultivation and use of drip irrigation might reduce spring NDVI in the part of farmlands, and the increase in stocking levels of livestock might lead to a decrease in NDVI in some grasslands.

[Ecological risk assessment of human activity of rapid economic development regions in southern Jiangsu, China: a case study of Dantu District of Zhenjiang City].

This article investigated the spatiotemporal variation of landscape ecological risk in Dantu District of Zhenjiang City with statistical method based on the ETM remote sensing data in 2000 and 2005, and the TM remote sensing data in 2010, and quantitative index of regional ecological risk assessment was established with the employment of landscape index, so as to enhance the ecosystem management, prevent and reduce the regional ecological risk in southern Jiangsu with rapid economic development. The results showed that the fragmentations, divergence, and ecological losses of natural landscape types, such as forestland, wetland, waters, etc., were deteriorated with the expansion of built-up lands from 2000 to 2010. The higher ecological risk zone took up 5.7%, 9.0%, and 10.2% of the whole region in 2000, 2005, and 2010, respectively, which mainly distributed in the plain hilly region. During the study period, the area aggravating to the higher ecological risk zone was approximately 296.2 km2, 48% of the whole region. The ecological risk rose up in most of the region. The interference of rapid economic development to landscape patterns was even more intensive, with obvious spatial differences in ecological risk distribution. The measures of exploiting resources near the port, utilizing natural wetlands, constructing industrial parks, and rapid urbanization, etc., intensified the ecological risk and accelerated the conversion rate. Prompt strategies should be established to manage the ecological risk of this region.