Zhijin County Research Articles

The impact of green and low carbon agricultural production on farmers’ income in minority areas: a case study of Y Town, Zhijin County, Guizhou Province

Developing green and low-carbon agriculture is an important and effective way to promote farmers’ income growth. Given the country’s “dual carbon” goal, the study of the impact of green and low-carbon agriculture on the income of farmers in ethnic minority areas is crucial for China to achieve the goals of socialist modernization and common prosperity. Taking Y Town, Zhijin County, Guizhou Province as an example, this paper uses the OLS regression method to empirically study the impact of green and low-carbon agricultural production methods on the income of farmers in ethnic minority mountainous agricultural areas based on the field survey data of 881 farmers. The regression results indicate that there is a positive correlation between green and low-carbon agricultural production and the household income levels of farmers; adopting green and low-carbon agricultural production technologies can effectively promote the growth of farmers’ household income. In addition, education level, health status, and the new rural social pension insurance have all had a significant effect on the income of rural households, however, due to the difficulty in establishing trust relationships, agricultural service outsourcing has reduced the household income level of farmers. As an example, the land transfer behavior in Y Town has no significant effect on increasing farmers’ incomes. Finally, it is recommended to increase fiscal and financial support as well as effectively enhancing farmers’ policy awareness and perception of green and low-carbon agricultural production technologies by improving farmers’ general trust and institutional trust by strengthening farmers’ agricultural education and skills training while cultivating technology-based farming. At the same time, it is necessary to break the geographical restrictions on land transfer scale and achieve moderate-scale land management while promoting the use and adoption of green and low-carbon agricultural production technologies, thereby improving agricultural production efficiency and product quality, and increasing the sustainable growth of farmers’ income. The main contribution of this study is to expand the research scope of green and low-carbon agriculture to ethnic minorities and mountainous agricultural areas.

Impact Assessment of the Implementation Effect of the Post-Relocation Support Policies of Rural Reservoir Resettlers’ Livelihoods in Energy Transition

Energy transition is a major structural change in the whole social system, and the energy system must be changed globally to replace fossil fuels. Hydropower is one of the largest sources of renewable energy in the world. However, owing to the construction of hydropower projects, involuntary resettlers are suffering from being far away from their native land, losing the land cultivated for generations and the houses they live in, and losing the social relationship network based on geography and blood ties. Based on the system evaluation theory of reservoir resettlement and referring to relevant research findings, this paper constructs a comprehensive evaluation index framework for assessing the implementation effect of the Post-Relocation Support (PReS) policy. The research region is located in Zhijin County, Bijie City, Guizhou Province, China. Accordingly, a combined method of a structural equation model and a fuzzy comprehensive evaluation model is used in this paper to analyze the implementation of the PReS policy. The results show that the total score of implementing effects of the PReS policy is 4.4, with dramatic significance. The subindex scores of the resettlers’ family income, living conditions, and production conditions; the local economy; and social stability are 4.3, 4.6, 4.4, 4.6, and 4.3, respectively, with dramatic significance. This paper has analyzed and summarized the successful practices of implementing the PReS policy for reservoir resettlers in three dimensions: poverty alleviation, beautiful home construction, and accelerating rural revitalization. Research shows that China’s rural reservoir resettlers’ PReS policy has been more effective in restoring the livelihoods of reservoir resettlers.

Risk assessment, spatial distribution, and source identification of heavy metals in surface soils in Zhijin County, Guizhou Province, China.

Zhijin County is a typical mineral resource-based city in Southwest China. The problem of heavy metals (HM) in the soil in Zhijin County must be considered during regional economic and ecological development. A total of 2436 soil samples (0‒20cm depth) were collected to analyze the soil pH, organic matter content, and HM spatial distribution and sources. The HM concentrations in the surface soil were found to be higher than the national surface soil background values. Absolute principal component sore-multivariate linear regression (APCS-MLR) showed that the HM sources in the surface soil of Zhijin County were industrial and agricultural activities (48.09%), natural sources (34.47%), and atmospheric deposition (17.43%); 65.53% of HM were produced by anthropogenic activities, which were mainly associated with the mineral industry. The impact of anthropogenic pollution decreased in the following order: paddy field (66.45%) > rainfed cropland (65.91%) > barren land (61.98%) > garden land (61.82%) > forest land (59.11%) > grassland (53.31%). The potential ecological risk of surface soil is moderate, while low-risk areas were mainly distributed in mountainous regions in the north, southwest, and east. The study emphasizes the source and risk assessment of HM in the surface soil of Zhijin County. The results can be used for environmental management planning, decision-making, and risk assessment.

Experimental Study on the Porosity and Permeability Change of High-Rank Coal under Cyclic Loading and Unloading.

It is of great significance to study the evolution law and change characteristics of the porosity and permeability of coal under cyclic disturbance to efficiently exploit coal-bed methane (CBM). In this paper, the GCTS rock mechanics experimental system is applied, the unsteady gas seepage test under cyclic loading and unloading is carried out with high-grade coal samples from Zhijin County, Guizhou Province, as the research object, and the mathematical formula of the dynamic change of porosity during loading and unloading is established. The results show that (1) the porosity and permeability parameters of coal are negatively correlated with confining pressure, and all decrease with the increase in confining pressure; (2) the change rate of the porosity and permeability of bedding coal decreases gradually with the increase in stress, and the porosity and permeability under high stress decrease gradually with the increase in cycle times; (3) during cyclic loading and unloading, the permeability loss (Dk) of coal mainly occurs in the first loading (>90%), and Dk gradually decreases with the increase in cyclic times; (4) under the same test conditions, the evolution law of the porosity and permeability of parallel bedding coal and vertical bedding coal is similar but the stress sensitivity of vertical bedding coal is higher; (5) the circumferential strain of parallel bedding coal is higher than that of vertical bedding coal, and the porosity change and permeability loss show a specific bedding effect; and (6) under the action of cyclic stress, the change of strain–permeability of coal is abnormal after it is destroyed. With the increase in strain before the sample is destroyed, the permeability drops sharply, and after the sample is destroyed, the strain decreases and the permeability never recovers. The research results can provide favorable theoretical guidance and technical support for pressure relief exploitation of coal-bed methane, such as multibranch horizontal wells.

Study on Mechanical Properties and Crack Propagation of Raw Coal with Different Bedding Angles based on CT Scanning.

The deformation and damage characteristics of coal are the important foundation that affects the fracturing potential of coal reservoirs and the development plan of coalbed methane (CBM). To reveal the influence regulation of primary fractures and the bedding angle of coal on its failure and provide theoretical basis for CBM development, raw coal samples of no 16 coal seam in Wenjiaba Coal Mine, Zhijin County, Bijie City with different bedding angles were selected as the research object, and uniaxial compression tests were carried out on them, and CT scanning and crack reconstruction before and after sample failure were carried out. The results show that (1) the compressive strength, elastic modulus, and Poisson’s ratio of coal show a strong bedding angle effect, and the changing trend of each index is basically the same. The coal samples with bedding angles of 0 and 90° are the highest, while the coal samples with bedding angles of 30° are the lowest, and the overall distribution is an approximate “U” with the increase in bedding angle. With the increase in bedding angle of 0–90°, the failure modes of coal samples are tension-shear combined failure, shear-slip failure, and splitting tension failure in turn. (2) The observation of raw coal and CT scanning show that the primary cracks in coal samples are well developed, especially in the lower part of 0° samples, the cracks in 30° samples, 60° samples, and 90° samples are evenly distributed and develop at a certain angle with the weak bedding surface, and microcracks parallel to and nearly perpendicular to the weak bedding surface are developed in 45° samples. At the same time, banded minerals in coal and rock samples are also well developed. (3) The characteristics of crack propagation and evolution in coal samples with different bedding dip angles are significantly different. The bedding dip angles and primary cracks of coal seam have a great influence on crack propagation. With different bedding angles, the propagation modes are different. The crack propagation mainly includes two ways: forming a certain angle with bedding and extending along the bedding plane. (4) The fracture characteristic parameters of coal in the primary state and after failure have the same law with the bedding dip angle, showing a trend of high at both ends and low in the middle, which is an irregular “U”-shaped distribution and has a similar law with mechanical characteristic parameters.

Analysis of the Influence of Forests on Landslides in the Bijie Area of Guizhou

Forests are an important part of the ecological environment, and changes in forests not only affect the ecological environment of the region but are also an important factor causing landslide disasters. In order to correctly evaluate the impact of forest cover on landslide susceptibility, in this paper, we build an evaluation model for the contribution of forests to the landslide susceptibility of different grades based on survey data for forest land change in Bijie City and landslide susceptibility data, and discuss the effects of forest land type, origin, age group, and dominant tree species on landslide susceptibility. We find that forests play a certain role in regulating landslide susceptibility: compared with woodland, the landslide protection ability of shrubland is stronger. Furthermore, natural forests have a greater inhibitory effect on landslides than artificial forests, and compared with young forest, mature forest and over-mature forest, middle-aged forest and near-mature forest have stronger landslide protection abilities. In addition, the dominant tree species in different regions have different impacts on landslides. Coniferous forests such as Chinese fir and Cryptomeria fortunei in Qixingguan and Dafang County have a low ability to prevent landslides. Moreover, the soft broad tree species found in Qianxi County, Zhijin County, Nayong County and Jinsha County are likely to cause landslides and deserve further research attention. Additionally, a greater focus should be placed on the landslide protection of walnut economic forests in Hezhang County and Weining County. Simultaneously, greater attention should be paid to the Cyclobalanopsis glauca tree species in Weining County because the area where this tree species is located is prone to landslides. Aiming at addressing the landslide susceptibility existing in different forests, we propose forest management strategies for the ecological prevention and control of landslides in Bijie City, which can be used as a reference for landslide susceptibility prevention and control.

Association Between Antioxidant Nutrients, Oxidative Stress-Related Gene Polymorphism and Skeletal Fluorosis in Guizhou, China.

BackgroundOxidative stress plays an important role in the pathogenesis of endemic fluorosis. We analyzed associations between oxidative stress-related gene polymorphisms (PON1 rs662, CAT rs769217, rs2300182, and SOD2 rs11968525) and skeletal fluorosis, and examined potential gene–environment interactions with dietary vitamin C, vitamin E, zinc, and selenium intake.MethodsA cross-sectional study was conducted in the Zhijin County, Guizhou Province of China. Skeletal fluorosis was identified according to the Chinese Diagnostic Criteria of Endemic Skeletal Fluorosis. Dietary information was assessed through face-to-face interviews by trained interviewers using a 75-item food frequency questionnaire. The genotype was detected by high throughput TaqMan-MGB RT-PCR technology. Odds ratios (ORs) and 95% CIs were calculated using an unconditional logistic regression model.ResultsIntake of vitamin E, zinc, and selenium was found to be inversely associated with the risk of skeletal fluorosis. The multivariable-adjusted ORs were 0.438 (95% CI: 0.268 to 0.715, P-trend < 0.001) for vitamin E, 0.490 (95% CI: 0.298 to 0.805, P-trend = 0.001) for zinc, and 0.532 (95% CI: 0.324 to 0.873, P-trend = 0.010) for selenium when comparing the highest with the lowest quartile. The relationship for vitamin C was not observed after adjustment for risk factors. Furthermore, participants with PON1 rs662 AA genotype had a significantly decreased risk of skeletal fluorosis compared with those with the GG genotype (OR = 0.438, 95% CI: 0.231 to 0.830). GG + AG genotype carriers were 2.212 times more likely to have skeletal fluorosis than AA carriers (OR = 2.212, 95% CI: 1.197 to 4.090). Compared with AA carriers, AG carriers had a 2.182 times higher risk of skeletal fluorosis (OR = 2.182, 95% CI: 1.143 to 4.163). Although we observed the risk of skeletal fluorosis was higher with a lower intake of antioxidant nutrients, the potential interactions between nutrient intake and genetic polymorphisms were not observed.ConclusionParticipants with a higher intake of vitamin E, zinc, and selenium have a lower likelihood of skeletal fluorosis. In addition, the PON1 rs662 polymorphism is related to skeletal fluorosis.

Spatial–temporal variations and multi-statistical analysis of contaminants in the waters affected by acid-mining drainage in Karst area: a case of coal-mining area in Zhijin County

Due to the adverse effects of coal-mining activities in Karst areas, it is necessary to monitor the contaminants, analyze their fate in the transport and identify the sources. Therefore, concentrations of contaminants were measured in both groundwater and surface water samples collected from coal-mining area in Karst, located in Zhijin County, Guizhou Province (China). The analysis of spatial–temporal variations of contaminants indicates that (1) the concentrations of metal elements (except Ba) and SO42− tend to decrease along the water flow direction, while the concentrations of Ba and nitrate still show an upward trend and (2) the concentrations of metal elements and SO42− have seasonal variations. Furthermore, the results of multi-statistical analysis which combine Pearson correlation coefficients (PCC) with the principal component analysis (PCA), identify five factors for the data structure of contaminants. What is more, the assessment of the water quality was evaluated by Nemerow index method to better understand the status. The results indicate that water quality in the area was poor, while 52.6% of water samples were identified into Grade IV and 16.7% were identified into Grade V by the Nemerow index method.

Regional Cooperation Action of Poverty Alleviation by Education in China: Documentary of Pairing Assistance Action in Changxing County, Zhejiang Province

Poverty alleviation by education is the soul of reshaping the development of impoverished areas. In the implementation of poverty alleviation, the collaborative model of impoverished areas driven by developed regions is essential for China’s poverty alleviation work. In 2016, Changxing County, Huzhou City, Zhejiang Province, and Zhijin County, Bijie City, Guizhou Province, established a counterpart support relationship. According to Zhijin County’s education assistance needs, Changxing County has gathered its strength to implement management input, demonstration guidance, and training guidance for its weak schools. With vocational education as the starting point, Zhijin County has been “remodeled” and “implanted” education assistance and has achieved a win-win situation. This article takes the education counterpart support activities of Changxing County and Zhijin County as an example to explore the path and methods of regional education assistance in China under the vision of collaboration.

Epidemiological Investigation and Etiological Analysis of a Cutaneous Anthrax Epidemic Caused by Butchering Sick Cattle in Guizhou, China.

A suspected human cutaneous anthrax epidemic caused by butchering sick cattle occurred in Zhijin County of Guizhou Province, Southwest of China, in 2016. Epidemiological investigation and etiological analysis were performed to provide a scientific basis for the source tracking of the epidemic. The epidemic was epidemiologically investigated, and skin blister samples collected from patients and soil samples collected from the butchering spots were used for Bacillus anthracis isolation. The suspicious B. anthracis isolates were identified using conventional methods and PCR, followed by genotyping using multiple-locus variable-number tandem repeats (VNTRs) analysis (MLVA-15) and canonical single-nucleotide polymorphism (canSNP). The genetic relationship of epidemic strains and isolates collected from other regions was analyzed. Epidemiological investigation results showed that the patients may be infected by B. anthracis during butchering sick cattle. Two suspected B. anthracis strains were isolated from blood samples and blister fluids, respectively. Conventional methods identified the two suspected isolates as B. anthracis, while PCR results showed that anti-protective antigen (PA) and capsule (CAP) gene were positive in the two isolates. MLVA-15 showed that the MLVA profiles of the two isolates were 9-20-12-53-16-2-8-8-8-4-4-4-4-10-4, which is different from the MLVA profiles of representative strains from other regions. CanSNP analysis showed that the two strains belonged to cluster A.Br.001/002. Clustering analysis and minimum spanning tree (MST) demonstrated that the two isolates were clustered with strains previously isolated from Guizhou Province. The results indicated that B. anthracis was the pathogen for this epidemic, and the patients were infected during butchering the sick. The genetic characteristics and the relationship of the B. anthracis isolates to strains from other regions indicated that the epidemic was a local occurrence.

Association Between Dietary Patterns and Fluorosis in Guizhou, China.

Objective: Many studies have explored the effects of individual foods or nutrients on fluorosis, but no studies have focused on dietary patterns. This study examined the relationship between dietary patterns and coal-burning fluorosis in Guizhou, China.Methods: This 1:1 matched case-control study was conducted in Zhijin County of Guizhou province with a sample size of 200 cases of fluorosis and 200 age and gender matched controls. Habitual dietary intake was assessed by face-to-face interviews, using a validated 75-item food frequency questionnaire (FFQ) and various covariates using structured questionnaires. The dietary patterns were identified by factor analysis.Results: The factor analysis identified three major dietary patterns which were labeled healthy, easy-to-roast and high protein. After adjusting for various confounding factors, a decreased risk for fluorosis was observed in the highest tertile of the healthy dietary pattern relative to the lowest tertile (OR = 0.47, 95% CI = 0.27–0.84, P-trend = 0.003) and a positive association was observed between the easy-to-roast dietary pattern and fluorosis risk (OR = 2.05, 95% CI = 1.15–3.66), with a significant linear trend (P = 0.017). We did not find an association between fluorosis risk and the high protein dietary pattern. The relationships remained significant when the analyses were stratified by gender and fluorosis subtypes.Conclusion: The healthy dietary pattern may lower coal-burning fluorosis risk; in contrast, the easy-to-roast dietary pattern significantly increases the risk of coal-burning fluorosis.

Relationship between fluoride exposure, orthopedic injuries and bone formation markers in patients with coal-burning fluorosis

Chronic exposure to fluoride is a public health problem worldwide. We explored the relationship between fluoride exposure, orthopedic injuries and bone formation markers alkaline phosphatase (ALP), bone Gla protein (BGP) in participants with coal-burning fluorosis in Hehua Village (coal-burning fluorosis endemic area) in Zhijin County of Guizhou Province and Zhangguan Village (non-fluoride contaminated area) in Anshun City of Guizhou Province. Environmental samples were collected and fluoride contents were examined using a fluoride ion-selective electrode. Dental fluorosis and skeletal fluorosis of 295 participants from Hehua Village and 85 participants from Zhangguan Village were diagnosed with informed consent. Urinary samples and peripheral blood samples were collected from the participants to determine urinary fluoride (UF), ALP acti-vity, and BGP content. The results showed that fluoride contents in rice, pepper, corn, drinking water, clay, vegetable-grown soil, coal and indoor and outdoor air were significantly higher than those in the control area, but lower than the previously reported values. With the increases of UF concentration, the ALP activity and BGP content significantly increased, the severity of skeletal fluorosis was greater, but with no significant changes in dental fluorosis. There was positive correlation between the severity of skeletal fluorosis and ALP activity, BGP content. These results indicated that low fluoride exposure could cause orthopedic injuries. ALP and BGP could be used to eva-luate the bone turnover in patients with skeletal fluorosis, which would be useful in the auxiliary diagnosis and therapeutic evaluation of skeletal fluorosis.

Morphometric analysis of sinkholes using a semi-automatic approach in Zhijin County, China

Efficient detection and analysis of natural sinkholes is essential for human sustainability in karst area. In this work, two methodologies were applied to detect and quantify natural sinkholes in southwest China, using of DEMs derived from ASTER and SRTM remote sensing images and topographic maps. The methodologies were a semi-automatic approach and a field-based approach. The first identifies the sinkholes based on DEM. The latter integrates the field survey, visual interpretation of high-resolution aerial photographs and topographic maps. The comparison between the semi-automatic approach and field-based approach generated the threshold values of the sinkhole shape, area, and TPI (topographic position index), which were used to distinguish true sinkholes and improve the identification accuracy. The result indicated that the semi-automatic approach produced the best accuracy by using the thresholds area > 60 m2, ellipticity > 0.2, and TPI ≤ 0 with the DEM from the topographic maps. With these realistic thresholds, the semi-automatic model shows well performance that model accuracy ranges from 0.78 to 0.95 for DEM resolutions from 3 to 75 m. The morphometric analysis was then obtained by using parameters derived from the semi-automatic approach and field-based approach. The sinkhole morphometric parameters are area, perimeter, diameter, shape, orientation, and volume. The results demonstrate (1) morphometric characteristics of sinkholes derived from the semi-automatic approach are coincident with those from the field-based approach. (2) Sinkholes in the region are relatively old and skewed to irregular or elliptical shape. (3) Sinkhole diameter and spatial alignments are highly controlled by faults. (4) Sinkholes argue about solution-only origin in the region.

Re–Os geochronology of the Cambrian stage-2 and -3 boundary in Zhijin County, Guizhou Province, China

The black shale series that formed in the Ediacaran–Cambrian transition are important stratigraphic records of the co-evolution of the paleo-ocean, -climate, and -biology. In this study, we measured Re–Os isotopic compositions of the black shale in the Niutitang Formation from the Gezhongwu section in Zhijin, Guizhou Province. The samples had high Re and Os contents, with Re ranging from 21.27 to 312.78 ng/g and Os ranging from 0.455 to 7.789 ng/g. The Re–Os isotope isochron age of 522.9 ± 8.6 Ma implies deposition of the Niutitang black shale predated the Chengjiang Fauna, providing an age constraint for the expansion of oceanic anoxia in the study area. The initial 187Os/188Os ratio of 0.826 ± 0.026 indicates that enhanced continental weathering might have triggered the expansion of the oceanic anoxia.

Sources, distributions of fluoride in waters and its influencing factors from an endemic fluorosis region in central Guizhou, China

The use of high fluoride-content coal caused the severe coal-burning endemic fluorosis in Zhijin County, Guizhou Province, China. The long-term mine exploitation in this region is as an important source of acid mine drainage (AMD) and leads to the release of potential fluoride (F−) into the surrounding waters. Aiming to investigate the source, hydrogeochemical characteristics and influencing factors of fluoride in waters of this area, a hydrogeological and geochemical research has been conducted in this study. Samples of various types of waters were collected and analyzed for major cations, major anions and TFe, Al; selected coal and gangue samples were analyzed for fluoride contents. The F− concentration in AMD or AMD-affected waters ranged from 0.27 to 4.94 mg/L, and F− was mainly enriched in Na–SO4 and Mg–SO4 waters, but a relatively low F− concentration was found in the Ca–SO4 water. The F− concentration in the Ca–HCO3 water without being affected by AMD ranged from 0.01 to 0.20 mg/L. The elevated F− contents were found in the AMD, which is mainly influenced by the local coal mining activities, and it is resulted from the dissolution of fluoride-bearing minerals in coal-bearing clastic rocks, as well as the low pH values, high Al and Fe concentrations, high total dissolved solids and high Al/F ratio of the AMD. In addition, the dissolution/precipitation of carbonate rocks and special hydrogeological conditions determined the F− concentration in surface water. Meanwhile, the climate is also an influencing factor that cannot be ignored to affect the F− concentrations of surface water and groundwater.

Sulphation of Topsoil in Hehua Village, Zhijin County, Guizhou Province

The endemic fluorosis in western Guizhou Province,southwest China was confirmed to be collected with high-content fluorine in topsoil (clay for coal-burning) of Hehua Village, Zhijin County,Guizhou Province ,which was considered to be closely associated with the long-term occurrence of endemic fluorosis. The new discovery in this article confirms that the mean value of apparent acidity of topsoil (pHa) in this village is 4.92;The measured average value of total sulfate radical was 4465μg/g. In addition, the apparent acidity and the content of total sulfate were positively correlated (correlation coefficient:0.7920).The result shows that the topsoil in this village is acidic and may belong to sulphation.

Study on the Rare Earth Containing Phosphate Rock in Guizhou and the Way to Concentrate Phosphate and Rare Earth Metal Thereof

Guizhou province is one of the main phosphate resources base in China, characterized with the co-existence of rare earth in the phosphate rock. In this work, the phosphate rock samples in Zhijin County, Guizhou province have been collected and analyzed using ICP, X-Ray diffraction, Scanning microscope, Infrared spectra and X-ray photoelectron spectroscope. It is found that the total content of rare earth elements in the phosphate rock is about 0.1 wt%, amongst which Y, La, Ce, Pr, Nd and Sm are the main rare-earth components and co-sit the lattice of the apatite. The phosphate content in the as-collected rock is more than 20 wt%, and impurities such as quartz, calcite and clay are also present. The raw phosphate rock physically was treated with flotation to remove the impurities such as quartz and calcite; a refined phosphate with rare earth elements of more than 0.1 wt%. The refined phosphate rock is then treated with excessive H3PO4 to dissolve the apatite; the residue from the dissolution gives an earth enriched precipitation, which contains up to 2 wt% rare earth elements. Compared to the conventional way to use H2SO4 to extract phosphate, the treatment of the refined phosphate with phosphoric acid leads to significantly improved rare earth oxide extraction.

Climate and environmental changes during the past millennium in central western Guizhou, China as recorded by Stalagmite ZJD-21

Stalagmite ZJD-21 (12.3-cm long) was collected from Zhijin Cave in Zhijin County, Guizhou, China. Its 210Pb profile and seven 230Th/ 234U dates indicate that the stalagmite has grown continuously for the past 1100 years. The δ 18O record of ZJD-21 indicates that δ 18O in the stalagmite was mainly influenced by rainfall amount and/or summer/winter rain ratio, with lighter values corresponding to wetter climatic conditions and/or more summer monsoonal rains. The ZJD-21 δ 18O record suggests: (1) dry/warm climates during AD 950-1100 (overlapping with most of the Medieval Warm Period, MWP, in Europe); (2) strengthening of the summer monsoon from the MWP toward the beginning of the Little Ice Age (LIA) at AD 1250; (3) relatively wet/cold conditions occurred between AD 1250 and 1500, shown by relatively light δ 18O values; (4) the summer monsoon intensity strongly declined referred by the increase δ 18O trend from AD 1500 to AD 1600, perhaps resulting in dry/cold conditions; and (5) a strongly enhancement of the summer monsoon intensity appeared from AD 1700 to 1950, reflecting wet/cold conditions during the late period of the LIA. On decadal scales the monsoonal climate of central western Guizhou can be either warm/wet and cold/dry, or warm/dry and cold/wet. The δ 13C variations in ZJD-21 on decadal-to-centennial scales respond mainly to vegetation changes with heavier values reflecting lesser amount of forest coverage. Prior to AD 1700, the δ 13C generally co-varied with δ 18O reflecting the expected more extensive vegetation growth (lighter δ 13C) under wetter climate (lighter δ 18O). However, during the past 300 years the δ 13C increased sharply showing an opposite trend to that of δ 18O. This observation strongly suggests that a decline of surface vegetation due to an artificial deforestation might have occurred – an occurrence coincident with the large-scale immigration into central western Guizhou in connection with copper-mining activities during the reign of Emperor Yongzheng of Qing Dynasty. Since the late 1890s, especially in the past 50 years, population surge has led to serious karst rocky desertification in the area.

Analysis on REE geochemical characteristics of three types of REE-rich soil in Guizhou Province, China

The three kinds of soil formed by the weathering of the basalt in Yema village, Weining county of Guizhou province, the carbonate rock in Guiyang district and the phosphorite in the REE-bearing phosphate mining area in Zhijin county of Guizhou province were all rich in REE. The contents of LREE in these three soil were higher than that of HREE, which was caused by the different properties of LREE and HREE complexes. Since light REE could be easily absorbed by kaolinite grains, LREE was fully enriched in the process of desorption, migration and re-absorption, which formed a typical LREE soil. The chondrite normalized distribution models of those three types of REE-enriched soil are basically similar, which belong to the right deviation type, namely, rich in light rare earth element but short of heavy rare earth element, and showing Ce negative anomalies. Eu showed intense negative anomalies in the REE in the soil formed by the weathering of the sedimentary parent rocks (such as carbonate rock and phosphorite), while no pronounced Eu anomaly was found in the REE in the soil formed by the weathering of volcanic rocks (such as basalt). It is clear that though there were intense migration and enrichment of REE during the weathering process of rocks, no obvious differentiation of REE occurred and some features of the parent rocks were retained. That is why REE is of value in analyzing the source of materials.

Child Skeletal Fluorosis from Indoor Burning of Coal in Southwestern China

Objectives. We assess the prevalence and pathogenic stage of skeletal fluorosis among children and adolescents residing in a severe coal-burning endemic fluorosis area of southwest China. Methods. We used a cross-sectional design. A total of 1,616 students aged between 7 and 16 years in Zhijin County, Guizhou, China in late 2004 were selected via a cluster sampling of all 9-year compulsory education schools to complete the study questionnaire. Any student lived in a household that burned coal, used an open-burning stove, or baked foodstuffs over a coal stove was deemed high-risk for skeletal fluorosis. About 23% (370) of students (188 boys, 182 girls) were identified as high-risk and further examined by X-ray. Results. One-third of the 370 high-risk participants were diagnosed with skeletal fluorosis. Overall prevalence of child skeletal fluorosis due to indoor burning of coal was 7.5%. Children aged 12–16 years were significantly more likely to be diagnosed with skeletal fluorosis than children aged 7–11 years (OR = 1.84, 95% CI: 1.17–2.90; P = .0082). Four types of skeletal fluorosis were identified: constrictive (60.7%), raritas (15.6%), mixed (16.4%), and soft (7.4%). Most diagnosed cases (91%) were mild or moderate in severity. In addition, about 97% of 370 high-risk children were identified with dental fluorosis. Dental fluorosis was highly correlated with skeletal fluorosis in this study. Conclusions. Skeletal fluorosis among children may contribute to poor health and reduced productivity when they reach adulthood. Further efforts to reduce fluoride exposure among children in southwestern of China where coal is burned indoors are desperately needed.