Zhibiao Chen

A human health risk assessment of rare earth elements in soil and vegetables from a mining area in Fujian Province, Southeast China

Contaminated food through dietary intake has become the main potential risk impacts on human health. This study investigated concentrations of rare earth elements (REEs) in soil, vegetables, human hair and blood, and assessed human health risk through vegetables consumption in the vicinity of a large-scale mining area located in Hetian Town of Changting County, Fujian Province, Southeast China. The results of the study included the following mean concentrations for total and bio-available REEs of 242.92 ± 68.98 (135.85-327.56)μg g(-1) and 118.59 ± 38.49 (57.89-158.96)μg g(-1) dry weight (dw) in agricultural soil, respectively, and total REEs of 3.58 ± 5.28 (0.07-64.42)μg g(-1) dw in vegetable samples. Concentrations of total REEs in blood and hair collected from the local residents ranged from 424.76 to 1274.80 μg L(-1) with an average of 689.74 ± 254.25 μg L(-1) and from 0.06 to 1.59 μg g(-1) with an average of 0.48 ± 0.59 μg g(-1) of the study, respectively. In addition, a significant correlation was observed between REEs in blood and corresponding soil samples (R(2)=0.6556, p<0.05), however there was no correlation between REEs in hair and corresponding soils (p>0.05). Mean concentrations of REEs of 2.85 (0.59-10.24)μg L(-1) in well water from the local households was 53-fold than that in the drinking water of Fuzhou city (0.054 μg L(-1)). The health risk assessment indicated that vegetable consumption would not result in exceeding the safe values of estimate daily intake (EDI) REEs (100-110 μg kg(-1)d(-1)) for adults and children, but attention should be paid to monitoring human beings health in such rare earth mining areas due to long-term exposure to high dose REEs from food consumptions.

Distribution and fractionation of rare earth elements in soil–water system and human blood and hair from a mining area in southwest Fujian Province, China

Accumulations of rare earth elements (REEs) in human body through multiple pathways including food ingestion, air inhalation and dermal absorption have received considerable attention due to their chronic toxicity to human health. The distribution and fractionation of 14 REEs were conducted in soil, well water, human blood and hair in the vicinity of a large-scale mining site in southwest Fujian Province, China. The LREEs/HREEs ratios were 9.17 for soil, 2.18 for water, 36.93 for human blood and 7.24 for human hair, respectively. The distribution patterns of REEs in soil, human blood and hair samples were characterized by LREEs enrichment and HREEs depletion, but LREEs depletion and HREEs enrichment in water sample. LaN/YbN values of these samples ranged from 0.41 to 1.83, LaN/SmN values from 0.43 to 4.92, and GdN/YbN values from 0.81 to 4.71. Soil and human blood showed enrichments of Ce, Gd and Er, but water showed a depletion of Ce. In addition, the normalized patterns showed a weak negative anomaly of Eu in soil and a weak negative anomaly of Nd in human blood and hair. Consequently, enrichment and depletion of REEs differ significantly among soil, water and human blood and hair, thus the REEs after entering into human body can undergo fractionation effects.

Stoichiometric mechanisms of Dicranopteris dichotoma growth and resistance to nutrient limitation in the Zhuxi watershed in the red soil hilly region of China

AimsLittle is known about why Dicranopteris dichotoma can succeed in a nutrient-limited environment. This study investigated the stoichiometric mechanisms of D. dichotoma growth and resistance to nutrient limitation in the red soil hilly region of China.MethodsWe examined D. dichotoma growth, soil nutrients, and stoichiometric variables in the early ecological restoration stage and across the ecological restoration chronosequence.ResultsMost of the D. dichotoma growth factors rapidly increased with the arbor-bush-herb mixed plantation and maintained a high level. Soil P was a main factor influencing D. dichotoma growth across the ecological restoration chronosequence, whereas its role is unclear in the early ecological restoration stage. D. dichotoma demanded low C and P and possessed high N and P utilization rates, and N and P distribution was ranked as leaf > root and rhizome > stem. The stoichiometry of D. dichotoma is a relatively weak stoichiometric homeostasis across the whole ecological restoration chronosequence with relatively strong stoichiometric homeostasis in the early ecological restoration stage.ConclusionsStoichiometry can be used to explore the underlying mechanisms that allow D. dichotoma to succeed to a great extent. D. dichotoma can play an important role in ecological restoration, and microtopography, especially valleys, should be created to trigger the succession of D. dichotoma in the red soil hilly region of China.

Soil Fertility Self-development Under Ecological Restoration in the Zhuxi Watershed in the Red Soil Hilly Region of China

Current methods that utilize simple data or models to judge whether soil fertility can self-develop are not sufficiently rigorous. A new framework has been set up using catastrophe theory, laboratory experiment, field work, and 3S (Geographic information system, Global positioning system, and Remote sensing) to explore soil fertility catastrophe under ecological restoration, discriminate whether soil fertility can self-develop, and propose adjustment of ecological restoration measures in the Zhuxi watershed of Changting County, Fujian Province, China, which is a typical representative of the red soil hilly region of China. The results show that: 1) the soil fertility is obviously improved through the four ecological restoration measures, which impels soil fertility catastrophe. Among 89 soil samples, catastrophic soil samples and stable soil samples account for 26 (29.21%) and 63 (70.79%) of the samples, respectively. The four ecological restoration measures are listed in the order low-quality forest improvement > arbor-bush-herb mixed plantation > orchard improvement > closing measures according to the proportions of catastrophic soil samples. A typical soil sample in Bashilihe that can self-develop is selected as the criterion to judge the upper lobe and lower lobe of soil fertility in the process surface of the Cusp catastrophe model. Twenty-six (29.21%) were in the middle lobe, 10 (11.24%) were in the upper lobe, and 53 (70.79%) were in the lower lobe. The catastrophic direction of 26 catastrophic soil samples is to the upper lobe according to soil and water loss change as well as fieldwork. There is a significant positive correlation of Δ with soil and water loss change, and the lower soil and water loss relates to higher catastrophic probability. 2) Soil fertility self-development could be regionalized as “Soil fertility can self-develop” whose area was 12.74 km2 (28.33%) distributed mainly in the leftmost and rightmost parts, “Soil fertility tends to self-develop” whose area was 11.63 km2 (25.89%) distributed mainly in the middle part, and “Soil fertility cannot self-develop” whose area was 20.58 km2 (45.78%) distributed mainly between the above two types. 3) There is no need to take ecological restoration measures and excessive human interference should be avoided in the future in regions of “Soil fertility can self-develop” and “Soil fertility tends to self-develop,” and ecological restoration measures should be taken in region of “Soil fertility cannot self-develop.” 4) We suggest withdrawal and implementation of ecological restoration measures should be incorporated into the evaluation criteria of ecological restoration to avoid misuse of funds.

Rare earth element migration in gullies with different Dicranopteris dichotoma covers in the Huangnikeng gully group, Changting County, Southeast China.

Little is known about rare earth element (REE) migration in gullies in Southeast China. We examine the concentration and distribution of REE, soil variables, and correlations among REE and soil variables field investigation, laboratory measurement, and statistical analysis in the three gullies with different Dicranopteris dichotoma covers in the Huangnikeng gully group, Changting County, Southeast China. We show that the REE pattern in gullies is typical of red soil in Southeast China. REE migrate severely in gullies with low vegetation cover, REE migrate from higher sites to lower sites under the influence of water flow and gravity, and gullies can be considered an important REE source. Dicranopteris dichotoma can succeed in gullies and affect part of soil variables, organic C and pH can play an important role in REE migration in gullies, and Dicranopteris dichotoma is a recommended plant for effectively controlling REE migration and gully erosion. The critical vegetation cover of gullies should be further studied to control REE migration and gully erosion.

Changes of eroded landscape pattern based on optimum scale

Spatial pattern heterogeneity exhibits various patterns at different scales; therefore different observed scales affect the results of spatial analysis. Effects of changing scale on spatial analysis have been studied for decades in geography and ecology, but few previous studies expounded the quantitative approach about the optimum grain. Some studies describe the eroded landscape pattern neglecting the grain effects, which may lead to the difference deviation. The main goal of this study was to set the optimum grain and study the pattern change under this grain, and the dynamic features of eroded landscape pattern in Zhuxi small watershed were researched by 3S and FRAGSTATS3.3. In order to get the optimum grain, 14 metrics were calculated in 19 different multiple grain sizes, and 10 m is finally defined as the optimum grain by characteristic curves of landscape metrics corresponding to grain sizes. Based on the optimum grain, a series of metrics in both class level and landscape level were chosen to describe the pattern change of Zhuxi small watershed. During 1999–2007, erosion types with higher intensity were largely transformed into micro-degree erosion and light erosion; small eroded patches of micro-degree erosion and light erosion had expanded to form large continuous ones with less fragmented, more regular and concentrated; patches of moderate, intensive, very intensive erosion types were becoming smaller, isolated and disconnected; the figures were becoming more regular and less complicated. At the landscape level, SHDI, SHEI, SHAPE_MN, FRAC_MN and AI decreased while PD, ED and CONTAG increased, which leaded to decreased landscape heterogeneity, more discrete and complex spatial distribution of patches, more regular shape and landscape fragmentation increase.

A Catastrophe Model to Assess Soil Restoration Under Ecological Restoration in the Red Soil Hilly Region of China

Abstract Current methods that utilize simple data or models to evaluate soil restoration under ecological restoration are not sufficiently rigorous. Soil restoration under ecological restoration measures was evaluated in the red soil hilly region of China by applying the catastrophe model. Among 89 soil sites selected, 26 (29.21%) were in the middle lobe, 10 (11.24%) in the upper lobe, and 53 (70.79%) in the lower lobe of the process surface in the Cusp catastrophe model. The catastrophic direction of the 26 unstable soil sites was to the upper lobe of the process surface according to vegetation cover change and fieldwork. There was a significant negative correlation of the variation in bifurcation set (Δ value) with vegetation cover increase, and a higher vegetation cover increase was related to higher unstable probability. The four ecological restoration measures were listed in the order: low-quality forest improvement (LQFI) > arbor-bush-herb mixed plantation (ABHMP) > orchard improvement (OI) > closing measures (CM) according to the proportions of unstable soil sites, which were all higher than no restoration measure, while they were in the order: LQFI

Spatial distribution of soil erosion risk in red eroded area of South China

As an ecological process, soil erosion which endangers human existence and development has been one of environmental problem around the world for a long time. Affected by various environmental factors, soil erosion risk has obvious spatial distributions. Taked the Zhu River small watershed of red eroded area of South China as an example, selected the five risk factors of rainfall erosion, terrain slope, soil type, vegetation cover and land use, used spatial analysis and geo-statistics methods of ArcGIS, studied the soil erosion risk. The results indicate that: moderate risk, high risk and extreme risk area proportion accounted for 63.82% of the whole watershed. Light and moderate risk area is mainly distributed along the river valley, throughout the steep and acute slopes of the hilly. High risk area mainly distributed in thin woodland around the red reservoir, the transportation land, blut mountain, collapse post. Extreme risk area is distributed in the quarry. Soil erosion risk has anisotropic characteristics, including the direction of risk is the NE-SW and NEE-SWW, direction of high risk and extreme risk is E-W and SE-NW. The risk of soil erosion escalates gradually from west to east, and emerges “U” from north to south.

Evaluation of Soil Fertility in Red Soil Eroded Watershed Based on GIS and Geostatistics

The evaluation of soil fertility in Zhuxi watershed was studied based on the methods of Geostatistics and GIS. The results showed that the higher soil fertility area was distributed on farmland in the downstream, the lowest soil fertility area was distributed in the central part of the watershed where soil was eroded seriously. The overall of soil fertility was low, the percentage of area was less than 10% in grade 1 and grade 2 which fertility were better, the area of grade 4 taken more than 50%, the area of grade 5 which fertility was lowest still more than 20%. It was indicated that although soil erosion was controlled for years in this watershed, soil fertility was still poor, restoration was a long-term process. The evaluation of soil fertility based on Geostatistics and GIS, which demonstrated that the soil fertility rapidly and intuitive, and give practical application for the results of Geostatistics.

Notice of Retraction Risk assessment of soil erosion and effects on soil nutrients in red eroded soil of south China

Soil erosion which endangers the human survival and development has been an important environmental problem around the world for a long time. The complexity and diversity presents in Zhuxi Small Watershed which is one of the thirty typical monitoring watersheds in China. The information which include rainfall, slope, soil, vegetation and land use, was obtained by combining 3S techniques with field investigation and the evaluation model on soil erosion risk was established by using these data. The soil erosion risk was divided by 5 types, including micro-degree risk, light risk, moderate risk, high risk and violent risk, and the distribution map of soil erosion risk was compiled also. The results showed that: Light risk and moderate risk were the main types and their area proportion was above 90%, areas of high risk and violent risk accounted for only 6.72% and 0.2% respectively, it could be inferred that ecosystem was not very vulnerable and unreasonable human activities could be the main reasons for the strong soil erosion in this region. Soil erosion risk type was the dominant factor affecting the contents of soil nutrients which could decrease soil nutrient contents Comparisons with field investigation showed that the result was in conformity with actual conditions proving the reasonability and applicability of the evaluation model.