Southwestern Guizhou Research Articles

Washability and Distribution Behaviors of Trace Elements of a High-Sulfur Coal, SW Guizhou, China

The float-sink test is a commonly used technology for the study of coal washability, which determines optimal separation density for coal washing based on the desired sulfur and ash yield of the cleaned coal. In this study, the float-sink test is adopted for a high-sulfur Late Permian coal from Hongfa coalmine (No.26), southwestern Guizhou, China, to investigate its washability, and to analyze the organic affinities and distribution behaviors of some toxic and valuable trace elements. Results show that the coal is difficult to separate in terms of desulfurization. A cleaned coal could theoretically be obtained with a yield of 75.50%, sulfur 2.50%, and ash yield 11.33% when the separation density is 1.57 g/cm3. Trace elements’ distribution behaviors during the gravity separation were evaluated by correlation analysis and calculation. It was found that Cs, Ga, Ta, Th, Rb, Sb, Nb, Hf, Ba, Pb, In, Cu, and Zr are of significant inorganic affinity; while Sn, Co, Re, U, Mo, V, Cr, Ni, and Be are of relatively strong organic affinity. LREE (Light rare earth elements), however, seem to have weaker organic affinity than HREE (Heavy rare earth elements), which can probably be attributed to lanthanide contraction. When the separation density is 1.60 g/cm3, a large proportion of Sn, Be, Cr, U, V, Mo, Ni, Cd, Pb, and Cu migrate to the cleaned coal, but most of Mn, Sb and Th stay in the gangue. Coal preparation provides alternativity for either toxic elements removal or valuable elements preconcentration in addition to desulfurization and deashing. The enrichment of trace elements in the cleaned coal depends on the predetermined separation density which will influence the yields and ash yields of the cleaned coal.

Predictive distribution and planting GAP of Cyathula officinalis in China based on 3S technology and MaxEnt modelling

Research on predictive distribution and planting GAP of Cyathula officinalis in China is helpful to provide scientific basis for its protection and planting popularization. According to the data in 63 distribution sites and 49 ecological variables, using MaxEnt ecological niche model and 3S technology, we performed a quantitative analysis of suitable distribution and planting GAP of C. officinalis in China. Our results show that: ① the area of suitable distribution of C. officinalis is about 634 385.80 km² in total, and mainly in Northeastern and Southeastern Sichuan, Northern and Southeastern Yunnan, Western and Southwestern Guizhou, Southwestern and Northeastern Chongqing, Southwestern Shaanxi, Southeastern Gansu, Western Guangxi, Southeastern Tibet. ② The main ecological factors determining the potential distribution are precipitation, altitude, minimum temperature of coldest month, soil type, monthly mean temperature. ③ The planting GAP region are mainly in Guangyuan, Mianyang, Ya'an, Leshan, Liangshan, Panzhihua of Sichuan province, Hanzhong of Shaanxi province, Dali, Nujiang, Chuxiong, Baoshan, Qujing, Wenshan of Yunnan province, southwestern autonomous prefecture in Guizhou province. The results are of great significance for realizing the growth environment, predicting the potential distribution and promoting planting popularization for C. officinalis.

A new species of Paris (Melanthiaceae) from Yunnan, China

Paris Linnaeus (Linnaeus 1753: 367) is the largest genus within Melanthiaceae, with more than 27 species (The Plant List 2013, Wang et al. 2017). It is widely distributed in the regions of southwestern China, especially Yunnan, Guizhou and other plateau provinces (Li 1998, Wu et al. 2004, Zhang et al. 2007, Huang et al. 2012). The genus Paris has 22 species in China, of which 14 are distributed in Yunnan (Li 1998) and five species are endemic to Yunnan; therefore, their species diversity ranks first in China (Zhao et al. 2016). Most species of Paris with a thick rhizome have been widely used in China for a long time to treat tumors, chronic bronchitis, for traumatic injuries, and as antimicrobial agent, achieving significant effect (Wu et al. 2004).

Basin-scale structure control of Carlin-style gold deposits in central Southwestern Guizhou, China: Insights from seismic reflection profiles and gravity data

Carlin-style gold deposits are widely distributed in Southwestern Guizhou, China. Research has dominantly focused on deposit-scale geology and structural control of mineralization. The relationship between the gold deposits and regional structures, in particular their control on the formation and distribution of those deposits is less well understood. Here we use seismic survey and gravity data to reveal the basin-scale structure control of the gold deposits in central Southwestern Guizhou. The seismic reflection profiles show strong reflection horizons including Upper Permian coal measures, and Dongwu and Guangxi unconformities. The seismic data provide important evidence of the basinal structural style and the relationship between fault-related folding and the Carlin-style gold deposits. Regional gravity data also revealed several paleo-uplifts, which appear to control the distribution of Carlin-style gold deposits.The Carlin-style gold deposits are spatially and temporally associated with fault-related folds. Based on their location, we classify the gold deposits into two types, (1) low-angle thrust-controlled deposits; and (2) high-angle reverse fault-related deposits. In the low-angle thrust-controlled deposits, main thrusts are listric, strike NW-SE and dip southwest. These thrusts detach into coal measures, tuffs and volcanic rocks and are bedding-parallel in the vicinity of the Dongwu unconformity. Gold ore bodies are found in the thrusts and characterized by cutting-layer veins near the surface and bedding-parallel veins at depth. The high-angle reverse fault-related deposits are located in the hinge of northeast-southwest-striking fault-related folds, with high-angle reverse faults near the hinge of folds crosscutting the Upper Permian coal measures, volcanic rocks and Dongwu unconformity, and then into the limestone of Middle Permian Maokou Formation. Ore bodies are bedding-parallel in anticline culminations where interlayer fracture zones in Upper Permian coal measures and volcanic rocks are generated by high-angle reverse faulting.We consider that the formation of the gold deposits is part of the tectonic evolution in the area. The two sets of NW-SE- and NE-SW-striking fault-related folds were successively formed during the closure of eastern Tethys Ocean in Late Triassic, and major gold deposits formed in the fault-related folds. The Dongwu unconformity and faults provided conduits for ore fluid flow, and the coal measures and the tuffs of Dachang Member acted as detachment layers and hosts for ore deposition.

Carbon-oxygen isotopes and rare earth elements as an exploration vector for Carlin-type gold deposits: A case study of the Shuiyindong gold deposit, Guizhou Province, SW China

The Shuiyindong gold deposit is a deeply concealed strata-bound Carlin-type deposit in southwestern Guizhou Province, China. The deposit lies on the eastern limb of the Huijiabao anticline with ores mainly along the anticline axis and hosted in bioclastic limestone, containing calcite veins, of the Permian Longtan Formation units. In this study, we measured carbon and oxygen isotopic ratios and rare earth element (REE) concentrations of the host rocks and calcite veins along a profile across the Shuiyindong deposit. Orebodies in the upper unit of the Longtan Formation have higher δ18O values (20.6–22.4‰) and lower δ13C values (−3.7 to −0.5‰) than the country rocks (δ18O: 18.8–21.4‰; δ13C: −0.7 to 0.8‰). However, there are no obvious trends of δ18O and δ13C values from the country rocks to the orebodies in the middle unit of the Longtan Formation. The spatial distribution of the calcite veins displays distinct halos of δ13C and δ18O values and REE concentrations. Calcite veins along the anticlinal axis and major reverse fault are enriched in Middle REE (Sm, Eu, Gd, and Tb) and 18O and depleted in 13C. Surficial veining calcite-filled fractures/faults that connect to deep concealed strata-bound gold mineralization systems can be vectors toward deep ores in southwestern Guizhou Province, China.

Geochemical characteristics of dissolved rare earth elements in acid mine drainage from abandoned high-As coal mining area, southwestern China.

Acid mine drainage (AMD) represents a major source of water pollution in the small watershed of Xingren coalfield in southwestern Guizhou Province. A detailed geochemical study was performed to investigate the origin, distribution, and migration of REEs by determining the concentrations of REEs and major solutes in AMD samples, concentrations of REEs in coal, bedrocks, and sediment samples, and modeling REEs aqueous species. The results highlighted that all water samples collected in the mining area are identified as low pH, high concentrations of Fe, Al, SO42- and distinctive As and REEs. The spatial distributions of REEs showed a peak in where it is nearby the location of discharging of AMD, and then decrease significantly with distance away from the mining areas. Lots of labile REEs have an origin of coal and bedrocks, whereas the acid produced by the oxidation of pyrite is a prerequisite to cause the dissolution of coal and bedrocks, and then promoting REEs release in AMD. The North American Shale Composite (NASC)-normalized REE patterns of coal and bedrocks are enriched in light REEs (LREEs) and middle REEs (MREEs) relative to heavy REEs (HREEs). Contrary to these solid samples, AMD samples showed slightly enrichment of MREEs compared with LREEs and HREEs. This behavior implied that REEs probably fractionate during acid leaching, dissolution of bedrocks, and subsequent transport, so that the MREEs is primarily enriched in AMD samples. Calculation of REEs inorganic species for AMD demonstrated that sulfate complexes (Ln(SO4)+and Ln(SO4)2-) predominate in these species, accounting for most of proportions for the total REEs species. The high concentrations of dissolved SO42- and low pH play a decisive role in controlling the presence of REEs in AMD, as these conditions are necessary for formation of stable REEs-sulfate complexes in current study. The migration and transportation of REEs in AMD are more likely constrained by adsorption and co-precipitation of Fe-Al hydroxides/hydroxysulfate. In addition, the MREEs is preferentially captured by poorly crystalline Fe-Al hydroxides/hydroxysulfate, which favors that sediments also preserve NASC-normalized patterns with MREEs enrichment in the stream.

The Au-Hosting Minerals and Process of Formation of the Carlin-Type Bojitian Deposit, Southwestern China

The recently discovered middle-sized Bojitian Carlin-type Au deposit is located in southwestern Guizhou Province, China, near the well-known Shuiyindong super-large-sized deposit. To improve the understanding on this deposit, here we investigate the minerals that host Au and the occurrence of Au in the deposit, using a combination of microscopic work and electron probe microanalysis (EPMA). Based on the results, the formation of the deposit was addressed. Results indicate that the dominant minerals that host Au include arsenian pyrite and arsenopyrite. Au in the cores of zoned pyrite exists mainly as natural nanoscale Au (Au0), while Au in the rims exists mainly as solid solution Au (Au+), but it likely also exists in the rims as natural nanoscale Au. The framboidal, coarse-grained, and banded pyrite types contain both natural nanoscale Au0 and solid solution Au+. The arsenopyrite is of hydrothermal origin, and Au within the arsenopyrite exists as gold solution Au+. The Bojitian deposit was formed from As-bearing, H2S-rich, low-to-medium-temperature fluids that migrated along faults and other channels. Au that was already present in the strata or source beds migrated with the fluids in the form of Au(HS)− and ore-forming fluids were then formed in the reducing environment. The ore-forming fluids interacted with Fe-rich carbonates to form an abundance of Au-hosting arsenian sulfides.

Variation inAselliscus stoliczkanusbased on morphology and molecular sequence data, with a new record of the genusAselliscusin China

The taxonomic status of the subspecies of Aselliscus stoliczkanus (Mammalia: Chiroptera: Hipposideridae) in China has yet to reach a consensus. To explore the variation and differentiation among populations of A. stoliczkanus from different regions of China, we conducted a series of bat surveys from 2012 to 2015. We performed multivariate morphological analyses using 16 external and 18 skull measurements and compared the sequence divergences of 2 mitochondrial genes (cytochrome b [ Cytb ] and cytochrome oxidase I [COI]). There were significant differences in external and skull measurements, particularly in the upper and lower canines, in the specimens from Guangxi compared with those from southwestern Yunnan and Guizhou. Sequence variation of the Cytb and COI genes was 11.0–13.2% and 12.4–14.0%, respectively, which represents differentiation at the species level. The samples from Guangxi were clustered with A. dongbacana from Vietnam in the phylogenetic trees based on COI sequences, and their sequence divergence was less than 3.2%. Based on the morphological and molecular results, we inferred that the samples from Guangxi were A. dongbacana , which represents a new record in China. Skull measurements of A. stoliczkanus from southwestern Yunnan exhibited significant morphological differences compared with those from Anlong County of Guizhou, and the sequence divergences of the Cytb and COI genes were 5.7–6.3% and 6.4–6.7%, respectively. Therefore, A. stoliczkanus from southwestern Yunnan and Anlong County of Guizhou might represent different subspecies. Finally, the phylogenetic analyses and minimal Cytb divergences of 0.2–0.9% indicated that specimens from southwestern and central Yunnan should be considered the same subspecies. Samples from Anlong County of Guizhou, Sichuan, and South Yunnan, with low Cytb divergences of 0.1–0.7%, represent another subspecies. A greater COI gene divergence was found between Libo and Anlong County of Guizhou; thus, the samples from Libo might represent yet another subspecies.

Geochemical characteristics of the giant Nibao Carlin-type gold deposit (Guizhou, China) and their geological implications

A large gold orebody controlled by Fault F1 was newly discovered in the giant Nibao Carlin-type gold deposit from southwestern Guizhou, China. Ore or rock samples were collected and studied to reveal the relationship among various orebodies which distributed in Fault F1 and its upper and lower plates, and to figure out the possible origin of ore-forming material. Tuff or tufaceous material was considered to be basic volcanic rocks in terms of their characteristic values of Al2O3/TiO2. Positive correlation was found between Au and As, and the correlation coefficient is particularly high within the fault fracture zone of the F1. Analysis shows that As can be regarded as a preferentially indicative element in gold prospection, while minerals of hydrothermal origin such as pyrite and arsenopyrite can be used as mineralogical indicative for gold prospection. Geochemical characteristics of trace elements and rare earth elements (REE) show that mantle source materials might have been involved in gold mineralization of different ore bodies. Large-scale Emei mantle plume eruption in the Early Permian resulted in thick volcanic sedimentary rock positioned between the karst unconformity surface at the top of the Maokou Formation and the bottom of the Longtan Formation. The Yanshanian tectonic activities played a significant role in driving gold-rich fluids to pressure-release spaces such as fault fracture zone and structure-controlling alteration zone (abbreviated to Sbt, according to Chinese). Those fluids reacted with ore-hosting rocks through water–rock interactions and resulted in the formation of gold-rich arsenian pyrite and arsenopyrite. Gold mineralization might have resulted from reactions between Fe-poor and gold-rich ore-forming fluids and tuffs which was relatively rich in iron, during which Fault F1 was considered to be the key to the formation of this giant gold orebody.

Two new cave-dwelling species of the millipede genus Paracortina Wang & Zhang, 1993 from southern China (Diplopoda, Callipodida, Paracortinidae).

Two new species of the millipede genus Paracortina Wang & Zhang, 1993 are described. Both are presumed troglophiles: Paracortina zhangi sp. n. from a cave in Ceheng County, southwestern Guizhou Province and Paracortina yinae sp. n. from a cave in Longlin County, western Guangxi Zhuang Autonomous Region. A distribution map and a key to all 12 Paracortina species are also provided.

Source Areas for the Early Immigration of Sogatella furcifera (Homoptera: Delphacidae) at Xiushan in the Middle Reach of Yangtze River of China.

The spatiotemporal distribution of source areas for the early immigration of the white-backed planthopper, Sogatella furcifera (Horvάth), at Xiushan in the middle reach of Yangtze River of China, was analyzed with HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory) and ArcGIS 10.0. The analysis was based on light trap data collected during April-July in 2000-2012. The synoptic meteorology backgrounds during the immigration periods were analyzed by GrADS (Grid Analysis and Display System). The light trap catches of S. furcifera varied monthly and annually. S. furcifera started immigration in Xiushan in early April to early May, whereas the main immigration period was in July. The distribution of the source areas varied monthly, and the core was moved from the south to the north gradually. The main source areas of S. furcifera in May were in southwestern Guangxi and northern Vietnam. The source areas of S. furcifera in June were located in southwestern Guangxi and western Hunan. Additionally, some of the pests were from southeastern Yunnan. The source areas in July were in northwestern Guangxi, southwestern Guizhou, eastern Yunnan, and the transitional parts of Guangxi, Guizhou, and Yunnan. The sum frequencies of southwest and south winds on the 850 hPa isobaric surface of Xiushan of May-July in heavy occurrence years were more than the light occurrence years. The key meteorological factors were suggested to be vertical perturbation, precipitation, and wind shear during S. furcifera immigration periods.

Heavy metal(loid) pollution in mine wastes of a Carlin-type gold mine in southwestern Guizhou, China and its environmental impacts

Mercury pollution resulting from artisanal gold mining is a serious environmental problem in many developing countries. In this study, we analyzed heavy metal(loid) contamination in mine wastes from a Carlin-type gold mine in southwestern Guizhou, China. Highly elevated levels of As, Hg, Tl, Sb, and Cd—up to 5844, 28, 29, 581 and 3.0 mg/kg, respectively—were observed in the mine wastes, but no significant accumulation of Cr, Ni, Cu, Zn, and Pb was found. The smelting process of gold ores had significant impacts on the enrichment of As, Tl, and Hg in the mine wastes. Due to the significant metal(loid) pollution in this gold mine, the ecological risks are classified as “very high.” Hg and As are the major pollutants with a relative contribution of 55.9 % and 24.2 % to the risk index, respectively. Phytoremediation could be used to reduce heavy metal contamination and recycle the gold simultaneously. Hg–As–Tl pollution should be considered in gold extraction at Carlin-type gold mines.

Comparative epidemiology and virology of fatal and nonfatal cases of hand, foot and mouth disease in mainland China from 2008 to 2014.

This study aimed to analyze the epidemiology and virology of fatal and nonfatal hand, foot, and mouth disease (HFMD) cases in Mainland China. A total of 10,714,237 survivors and 3046 deaths were reported from 2008 to 2014 June, with a case fatality rate of 0.03%. The morbidity of the survivors increased from 37.6/100,000 in 2008 to 139.6/100,000 in 2013 and peaked in 2012 at 166.8/100,000. However, the mortality varied around 0.03-0.04/100,000 across the time. Most of the survivors were distributed in the southern and eastern China, predominantly in the Guangxi and Hainan Province, whereas deaths were dominant in southern (Guangxi) and southwestern (Guizhou) China. The two groups showed similar seasonal fluctuations from 2008 to 2014, peaking in spring and early summer. Of the total cases, 93.97% were children less than 5 years of age, with those ≤ 2 years old accounting for 60.08% versus 84.02% in the survivor and death groups, respectively. Boys were at higher risk of infection than girls in both groups. Five years of virological surveillance showed that 43.73%, 22.04%, and 34.22% of HFMD cases were due to EV71, CoxA16 and other enteroviruses, respectively. EV71 was encountered in most deaths, with no substantial effect of age, gender, month, and year on incidence. Subgenotype C4a was the prevalent EV71 strain in Mainland China, with no significant difference in the VP1 gene related to virulence between the two groups. In conclusion, based on the largest population study, fatal and nonfatal HFMD cases, mainly caused by C4a of EV71, are circulating in Mainland China with a low-cause fatality rate.

Ore-forming process of the Huijiabao gold district, southwestern Guizhou Province, China: Evidence from fluid inclusions and stable isotopes

The Huijiabao gold district is one of the major producers for Carlin-type gold deposits in southwestern Guizhou Province, China, including Taipingdong, Zimudang, Shuiyindong, Bojitian and other gold deposits/occurrences. Petrographic observation, microthermometric study and Laser Raman spectroscopy were carried out on the fluid inclusions within representative minerals in various mineralization stages from these four gold deposits. Five types of fluid inclusions have been recognized in hydrothermal minerals of different ore-forming stages: aqueous inclusions, CO2 inclusions, CO2–H2O inclusions, hydrocarbon inclusions, and hydrocarbon–H2O inclusions. The ore-forming fluids are characterized by a H2O+CO2+CH4±N2 system with medium to low temperature and low salinity. From early mineralization stage to later ones, the compositions of the ore-forming fluids experienced an evolution of H2O+NaCl→H2O+NaCl+CO2+CH4±N2→H2O+NaCl±CH4±CO2 with a slight decrease in homogenization temperature and salinity. The δ18O values of the main-stage quartz vary from 15.2‰ to 24.1‰, while the δDH2O and calculated δ18OH2O values of the ore-forming fluids range from −56.9 to −116.3‰ and from 2.12‰ to 12.7‰, respectively. The δ13CPDB and δ18OSMOW values of hydrothermal calcite change in the range of −9.1‰ to −0.5‰ and 11.1–23.2‰, respectively. Stable isotopic characteristics indicate that the ore-forming fluid was mainly composed of ore- and hydrocarbon-bearing basinal fluid. The dynamic fractionation of the sulfur in the diagenetic pyrite is controlled by bacterial reduction of marine sulfates. The hydrothermal sulfides and the diagenetic pyrite from the host rocks are very similar in their sulfur isotopic composition, suggesting that the sulfur in the ore-forming fluids was mainly derived from dissolution of diagenetic pyrite. The study of fluid inclusions indicates that immiscibility of H2O–NaCl–CO2 fluids took place during the main mineralization stage and caused the precipitation and enrichment of gold.

Restudy of conodont biostratigraphy of the Permian–Triassic boundary section in Zhongzhai, southwestern Guizhou Province, South China

New conodont samples have been systematically collected at high stratigraphic resolution from the upper part of the Longtan Formation through to the lower part of the Yelang Formation at the Zhongzhai section, southwestern Guizhou Province, South China, in an effort to verify the first local occurrence of Hindeodus parvus in relation to the Permian–Triassic boundary at this section. The resampled conodont fauna from the Permian–Triassic boundary interval comprises five identified species and two undetermined species in Hindeodus and Clarkina. Most importantly, the first local occurrence of Hindeodus parvus is found for the first time from the bottom of Bed 28a, 18cm lower than the previously reported first local occurrence of this species at this section. Considering the previously accepted PTB at the Zhongzhai section, well calibrated by conodont biostratigraphy, geochronology and carbon isotope chemostratigraphy, this lower (earlier) occurrence of H. parvus suggests that this critical species could occur below the Permian–Triassic boundary. As such, this paper provides evidence that (1) the first local occurrences of H. parvus are diachronous in different sections with respect to the PTB defined by the First Appearance Datum (FAD) of this species at its GSSP section in Meishan, China and that (2) the lower stratigraphic range of H. parvus should now be extended to latest Permian.

A new Changhsingian (Late Permian) Rugosochonetidae (Brachiopoda) fauna from the Zhongzhai section, southwestern Guizhou Province, South China

Zhang, Y., He, W.-H., Shi, G.R. & Zhang, K.-X., 2013. A new Changhsingian (Late Permian) Rugosochonetidae (Brachiopoda) fauna from the Zhongzhai section, southwestern Guizhou Province, South China. Alcheringa 37, 221–245. ISSN 0311-5518. This paper describes 20 species (including three undetermined species) of Rugosochonetidae (Brachiopoda) in an upper offshore fauna from the Permian–Triassic Boundary Zhongzhai section, southwestern Guizhou Province, South China. New taxa are Tethyochonetes sheni, Tethyochonetes cheni, Neochonetes (Huangichonetes) archboldi, Neochonetes (Sommeriella) waterhousei, Neochonetes (Sommeriella) rectangularis and Neochonetes semicircularis. Yang Zhang [zyan@deakin.edu.au] and G.R. Shi [guang.shi@deakin.edu.au] (corresponding author), School of Life and Environmental Sciences, Deakin University, Melbourne Burwood Campus, 221 Burwood Highway, Burwood, Victoria 3125, Australia; Weihong He [whzhang@cug.edu.cn] (corresponding author) and Kexin Zhang [kx_zhang@cug.edu.cn], State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, 388 Lumo Road, Hongshan, Wuhan 430074, PR China. Received 8.6.2012; revised 19.9.2012; accepted 7.10.2012.

Thallium at the interface of soil and green cabbage (Brassica oleracea L. var. capitata L.): Soil–plant transfer and influencing factors

Thallium (Tl) is a non-essential and toxic trace metal found in many plants, but it can accumulate at particularly high concentration in green cabbage (Brassica oleracea L. var. capitata L.). The aim of this study is to explore the transfer and accumulation of Tl at the interface of rhizospheric soil and green cabbage from a long-term Tl contaminated site in southwestern Guizhou Province, China. Influencing factors such as Tl distribution in various soil fractions and physical–chemical characteristics of rhizospheric soil were also investigated. Our results demonstrated that green cabbage had high accumulation of Tl, with most bioconcentration factor (BF) values exceeding 1, and up to a maximum level of 11. The enrichment of Tl in the green cabbage tissues followed a descending order, i.e. old leaves>fresh leaves>stems≈roots. The stems functioned as a channel for Tl transportation to the leaves, where most of the Tl (greater than 80%) was found to accumulate. In the rhizospheric soils, 62–95% of Tl existed in the residual fraction, while lower concentrations of Tl (on average, 1.7% of total T1 in rhizospheric soil) were found in the water and acid soluble fractions. The major fraction of labile Tl was located in the reducible fraction (9%). Our results also suggested that the uptake and enrichment of Tl in green cabbage were affected by Tl concentrations, soil water content, soil pH, soil organic material (SOM) and cation exchange capacity (CEC) in rhizospheric soil.

喀斯特山区土地利用对土壤团聚体有机碳和活性有机碳特征的影响

Soil organic carbon is a dynamic medium of carbon transfer and is a main pathway for the circulation of carbon through soils in Karst systems.Karst systems are typically ecologically fragile areas with limited environmental capacity and resistivity.In addition,the implementation of a state policy encouraging the return of farmland to woodland(grass) and labor output in recent years has led to considerable change in land use patterns over a short period in these areas,which is bound to have far-reaching impacts on the spatial distribution pattern of soil organic carbon.Extensive previous research has investigated the response characteristics of soil organic carbon under different land use patterns.However in general,most of these studies have only investigated the total soil organic carbon in whole soils,and have rarely studied the organic carbon and labile organic carbon in soil aggregates.Organic carbon and labile organic carbon in aggregates are largely isolated from microbial activity because of the physical protection of the aggregates,and this may have a major impact on their function as soil carbon sinks.Therefore,the purpose of this study was to explore the distribution and accumulation characteristics of organic carbon and labile organic carbon in aggregates through survey,sampling,and analysis of soils in selected Karst mountain areas in China. The experiment was conducted in a small watershed in Huajiang Karst areas in southwestern Guizhou(25° 38.988′—25° 41.322′N latitude and 105° 38.031′—106° 40.505′E longitude).Samples of topsoils(0—15 cm) were collected from five kinds of typical land use patterns(Pitaya orchard,grassland,Chinese prickly ash orchard,forest and shrub-grassland).Soil aggregates were separated by dry sieving.Aggregate composition was dominated by particles 0.5 mm which accounted for 82.57% to 94.79% of the whole soil under the different land use patterns.In all size classes of aggregate particles,forest had the highest values of organic carbon and labile organic carbon,followed by Chinese prickly ash orchard,while grassland and shrub-grassland were relatively lower.With decreasing aggregate particle size,the peak of organic carbon and labile organic carbon basically appeared in particles 0.25 mm in size.However,these aggregate particles contributed less than 6% and 4%,respectively,to the contents of soil organic carbon and soil labile organic carbon.The accumulation of soil organic carbon and soil labile organic carbon were influenced by increasing aggregate size,with 5—1 mm aggregates contributing 28.70%—49.47% and 34.13%—47.47% of the organic carbon and labile organic carbon contents,respectively.Therefore,it can be assumed that particles of aggregate size 5—1 mm hold the majority of soil carbon fixed in Karst mountain areas.In addition,the labile organic carbon content and total organic carbon content in soil aggregates were highly significantly positively correlated(r=0.8768),which suggests that labile organic carbon may be a sensitive index for measuring the dynamics of organic carbon in soil aggregates in Karst mountain areas.Our results will help to reveal the regional soil organic carbon sequestration in Karst mountain areas in China.

A new eosauropterygian (Diapsida, Sauropterygia) from the Triassic of China

ABSTRACT A new Middle Triassic sauropterygian, Qianxisaurus chajiangensis, gen. et sp. nov., is described on the basis of a skeleton from the Zhuganpo Member (Ladinian) of the Falang Formation, Xingyi, southwestern Guizhou Province, China. It is primarily characterized by a premaxilla with eight teeth, marginal teeth with a slightly constricted peduncle and short conical crown, snout longer than the rest of skull, postorbital with a truncated dorsal process and forked posterior process, a very small supratemporal fenestra, a short retroarticular process posteriorly truncated and lacking a dorsal concavity, an elongate trunk with 28 vertebrae, a stout sacrum with four vertebrae, a longitudinal groove on proximodorsal surface of the dorsal ribs, and a coracoid with a narrow lateral portion and a foot-shaped medial portion. Q. chajiangensis appears similar to the European pachypleurosaurs, but a global phylogenetic analysis failed to support close relationships with these taxa. Instead, Q. chajiangensis is an eosauropterygian and most probably the sister group of a clade consisting of the European pachypleurosaurs and the Nothosauroidea. The discovery of Q. chajiangensis certainly enriches our knowledge of the early history of the Eosauropterygia and leads to a better understanding of the phylogenetic relationships among known eosauropterygians.

Wetland changes and droughts in southwestern China

The five provinces of southwestern China, Sichuan, Chongqing, Guizhou, Yunnan and Guangxi, frequently suffer from droughts, especially the recent severe drought of five consecutive months from autumn 2009 to spring 2010, which caused serious water shortages, huge economic losses and adverse social consequences. With increasing human activity in the last 200 years, the wetland areas have decreased and their ecological functions such as water conservation, climate regulation have declined, which has a direct impact on climate and the ecological environment. Using satellite images, changes in wetland areas of the five provinces of southwestern China have been mapped from 1970 to 2008. Our detailed analysis shows that the wetland area in the 1970s, 1990, 2000 and 2008 occupy an area of 20822.9, 18386.16, 19904.22 and 17269.72 km2, respectively, which indicate that the wetland areas have a downtrend, at an accelerating rate, from 2000 to 2008. Considering the complexity between wetland change and drought, the correlation between spatial and temporal wetland change and drought have been analysed using monthly ground meteorological data from 1971 to 2009, obtained from the China Meteorological Data Sharing Service Network. The analysed results show that the decrease of the wetland area, damage to biological resources and decline in climate regulation function are closely related to serious drought problems in the five provinces of southwestern China. Finally the corresponding solutions are discussed by analysing the problems faced by the wetland ecological system.