State of rare earth elements in different environmental components in mining areas of China

China has relatively abundant rare earth elements (REEs) reserves and will continue to be one of the major producers of REEs for the world market in the foreseeable future. However, due to the large scale of mining and refining activities, large amounts of REEs have been released to the surrounding environment and caused harmful effects on local residents. This paper summarizes the data about the contents and translocation of REEs in soils, waters, atmosphere, and plants in REE mining areas of China and discusses the characteristics of their forms, distribution, fractionation, and influencing factors. Obviously high concentrations of REEs with active and bioavailable forms are observed in all environmental media. The mobility and bioavailability of REEs are enhanced. The distribution patterns of REEs in soils and water bodies are all in line with their parent rocks. Significant fractionation phenomenon among individual members of REEs was found in soil–plant systems. However, limited knowledge was available for REEs in atmosphere. More studies focusing on the behavior of REEs in ambient air of REE mining areas in China are highly suggested. In addition, systematic study on the translocation and circulation of REEs in various media in REEs mining areas and their health risk assessment should be carried out. Standard analytical methods of REEs in environments need to be established, and more specific guideline values of REEs in foods should also be developed.     

Using ecological memory as an indicator to monitor the ecological restoration of four forest plantations in subtropical China

A large area of plantations has been established worldwide and especially in China. Evaluating the restoration status of these plantations is essential for their long-term management. Based on our previous work, we used an ecological memory (EM) approach to evaluate four 26-year-old plantations that represent four common kinds of plantations in subtropical China, i.e., mixed broad-leaved plantation (MBP), mixed coniferous plantation (MCP), eucalyptus plantation (EP), and mixed legume plantation (MLP). Comparing them with the regional climax community, i.e., monsoon evergreen broad-leaved forest (BF), all four plantations accumulated nearly the same pattern of EM during succession. EM was >50 % for soil minerals, light conditions, soil age, soil animals, and soil microbes. EM was about 25 % for soil pollen and 10 % for birds, soil seed bank, and plant species. The total EM value of the four plantations ranged from 50.96 to 52.54, which indicated that all four plantations were in the regional, natural trajectory of succession and between the early and medium successional stages. The results indicated that natural succession processes are unlikely to be accelerated by planting late-stage tree species without sufficient EM. The results also demonstrated that all four plantations were in positive successional trajectories, and the positive succession dynamics were greater in the MLP and MCP. We suggest that the entire natural succession trajectory be used to evaluate the restoration of a site and that the ultimate restoration target be divided into several milestones along the reference trajectory to monitor progress. Forest restoration may be accelerated by starting with a minimum dynamic unit supporting sufficient EM.     

Improving artificial forest biomass estimates using afforestation age information from time series Landsat stacks

China maintains the largest artificial forest area in the world. Studying the dynamic variation of forest biomass and carbon stock is important to the sustainable use of forest resources and understanding of the artificial forest carbon budget in China. In this study, we investigated the potential of Landsat time series stacks for aboveground biomass (AGB) estimation in Yulin District, a key region of the Three-North Shelter region of China. Firstly, the afforestation age was successfully retrieved from the Landsat time series stacks in the last 40 years (from 1974 to 2013) and shown to be consistent with the surveyed tree ages, with a root-mean-square error (RMSE) value of 4.32 years and a determination coefficient (R ²) of 0.824. Then, the AGB regression models were successfully developed by integrating vegetation indices and tree age. The simple ratio vegetation index (SR) is the best candidate of the commonly used vegetation indices for estimating forest AGB, and the forest AGB model was significantly improved using the combination of SR and tree age, with R ² values from 0.50 to 0.727. Finally, the forest AGB images were mapped at eight epochs from 1985 to 2013 using SR and afforestation age. The total forest AGB in seven counties of Yulin District increased by 20.8 G kg, from 5.8 G kg in 1986 to 26.6 G kg in 2013, a total increase of 360 %. For the persistent forest area since 1974, the forest AGB density increased from 15.72 t/ha in 1986 to 44.53 t/ha in 2013, with an annual rate of about 0.98 t/ha. For the artificial forest planted after 1974, the AGB density increased about 1.03 t/ha a year from 1974 to 2013. The results present a noticeable carbon increment for the planted artificial forest in Yulin District over the last four decades.     

Molecular detection of three gastroenteritis viruses in urban surface waters in Beijing and correlation with levels of fecal indicator bacteria

To assess the presence of three gastroenteritis viruses responsible for human acute gastroenteritis in surface water, a 1-year study was carried out in the city of Beijing, China. A total of 108 urban surface water samples were collected from nine collection sites which were defined with a global positioning system in rivers or lakes from September 2006 to August 2007. The water samples were subjected to virus concentration using an HA electronegative filter, followed by polymerase chain reaction (PCR) for rotavirus (RV) astrovirus (AV), and norovirus (NV). It showed that the number of viruses detected in water samples from different sites was variable, totaling 63 virus strains, with rotavirus (48.1%) verified as the most prevalent detected, followed by astrovirus (AV, 5.6%), and norovirus (NV, 4.6%). RV was also quantified by real-time PCR and the concentration of RV ranged from 0 to 18.27 genome copies·L(-1). And the distributions of RV in surface water were abundant in cold weather (from September to February) while less prevailing in warm weather (from March to August). The high detection rate of RV we encountered in this study provided convincing evidence that RV circulated at a certain frequency in the Beijing population. There was no statistically significant correlation between RV levels and both fecal coliform (R (2)?=?0.02) and Enterococcus faecalis (R (2)?=?0.02) densities. Our study suggests prolonged virus persistence in aquatic environments and emphasizes the enteric virus group as the most reliable for environmental monitoring.     

A novel approach to rapid detection of acute water toxicity and its policy implications for grassroots sustainable environmental monitoring

Unknown chemicals, emerging contaminants, and the resulting reactions among them make early detection and warning of acute water toxicity extremely challenging. The conventional approach using small fish for toxicity monitoring normally requires a designated species of fish and over a week's time to complete, including dilution of the wastewater, a pre-test, and a full test. It often increases chances for error and delays emergency management. This paper reports a novel approach, based on grassroots knowledge and field and lab experience in Jilin, China. This approach uses a combination of different species of aquarium fish to achieve fast and reliable monitoring. It tests the original source water directly without going through the dilution procedure, while paying attention to the time factor. The approach does not require a pre-test and may shorten the time needed for detecting acute toxicity to a few minutes, using a new classification of aquatic toxicity levels. It is inexpensive to use and may be easily adopted by grassroots organizations. The approach is "greener" and more financially and socially sustainable than traditional approaches. The wide use of the approach has the potential to encourage policy innovations for making toxicity monitoring grassroots based and more effective in reducing acute contamination emergencies.     

Baseline values for metals in soils on Fildes Peninsula, King George Island, Antarctica: the extent of anthropogenic pollution

Metal contents (Al, Ca, Cd, Cr, Cu, Fe, Hg, Mg, Mn, Ni, Pb, Ti, and Zn) have been measured in 30 surface soils on Fildes Peninsula, King George Island, Antarctica, yielding values (in milligrams kilogram(-1)) of 41.57-80.65 (Zn), 2.76-60.52 (Pb), 0.04-0.34 (Cd), 7.18-25.03 (Ni), 43,255-70,534 (Fe), 449-1,401 (Mn), 17.10-64.90 (Cr), 1,440-25,684 (Mg), 10,941-49,354 (Ca), 51.10-176.50 (Cu), 4,388-12,707 (Ti), 28,038-83,849 (Al), and for Hg (in nanograms gram(-1)) 0.01-0.06. Relative cumulative frequency analysis was used to determine the baseline values for the 13 metals. Compared with adjacent areas in Antarctica, Mg and Ni are significantly lower, but Cu is significantly higher than that of McMurdo Station. Enrichment factor analysis and the geo-accumulation index method were applied in order to determine the extent of anthropogenic contamination, and both show that Pb, Cd, and Hg have been significantly increased by human activities. Principal component analysis was used to identify the sources of metals in these soil samples.     

Characteristic, composition, and sources of TSP investigated by HRTEM/EDS and ESEM/EDS

Total suspended particle (TSP) collected at the fifth floor of House Dust in Hunan University, China, was analyzed in terms of microscopic morphology and chemical composition. The fine particles (50?nm-2?μm) in the TSP were analyzed by a high-resolution transmission electron microscope equipped with an energy-dispersive X-ray analyzer (HRTEM/EDS). Results showed that the particles were in shapes of plate, irregular and agglomerate. Based on EDS results, these fine particulate matter was primarily composed of Fe-rich (35.82-61.29%), Ca-rich (30.18-36.77%) and Si-rich (18.95-32.28%) particles. Other elements mainly including Mg (0.47-4.97%), Al (0.45-14.57%), S (0.45-4.73%), K (1.13-2.13%) and Zn (0.67-3.85%) were also observed. The sources analysis indicated that the HRTEM particles mainly originated from coal combustion, traffic emission, vehicles exhaust emission and fugitive soil or cement particulate matter. The coarse particles (4-50?μm) were detected by environmental scanning electron microscopy coupled with energy-dispersive X-ray detector (ESEM/EDS). Based on a simple algorithm, ESEM particles were categorized into five groups: C-bearing (46.15%, 67% and 86.98%), Si + Ca-bearing (21.48?+?11.80%, 16.51?+?10.81% and 16.32?+?10.62%), Si + Al-bearing (20.06?+?12.40%, 20.16?+?11.22% and 15.31?+?11.25%), Si-bearing (34.40%, 26.92% and 27.15%) particles and aggregates, most of which exhibit obvious crystalline structure, and these ESEM particles mainly derived from vehicles exhaust emission, coal combustion, soil, and biomass burning, while the aggregates are indicative of atmospheric reaction progress. HRTEM/EDS and ESEM/EDS are mutual complementary in analyzing the characteristic and determining the sources of TSP.     

Dynamics of the lakes in the middle and lower reaches of the Yangtze River basin, China, since late nineteenth century

The middle and lower reaches of the Yangtze River basin have the most representative and largest concentration of freshwater lakes in China. However, the size and number of these lakes have changed considerably over the past century due to the natural and anthropogenic impact. The lakes, larger than 10 km² in size, were chosen from relief maps and remotely sensed images in 1875, 1950, 1970, 1990, 2000, and 2008 to study the dynamics of lakes in the middle and lower reaches of the Yangtze River basin and to examine the causes and consequences of these changes. Results indicated that there was a dramatic reduction in lake areas, which decreased by 7,841.2 km² (42.64 %) during the study period (1875–2008), and the number of lakes in this region changed moderately. Meanwhile, a large number of lakes in the middle and lower reaches of the Yangtze River basin were directly converted into paddy fields, ponds, building lands, or other land-use types over the study period. Therefore, all kinds of lake reclamation should be identified as the major driving factors for the loss of lake in this region. Furthermore, flooding, soil erosion, and sedimentation were also the main factors which triggered lake changes in different periods. Some wetland conservation and restoration projects have been implemented since the 1970s, but they have not reversed the lake degradation. These findings were of great importance to managers involved in making policy for the conservation of lake ecosystems and the utilization of lake resources.