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To investigate the characteristics of elements in selenium and cadmium rich soil and the ecological risk of local agricultural products in the typical heavy metal high background area of Chongqing,Taking the Se and Cd enriched soil in study area as a research object, The effects of Cd and Se on agricultural products were studied by collecting and analyzing the element contents and available contents of soil and agricultural products samples, The results showed that The pH value of soil in the study area is 6.89 ~ 8.22, which is alkaline and rich in organic matter; The study area belongs to the typical high background area of heavy metals. The content of Cd in the soil is 0.52 ~ 1.84 mg·kg-1, the average value is 1.26 mg·kg-1, the content of se is 0.41 ~ 0.77 mg·kg-1, the average value is 0.64 mg·kg-1, and its element characteristics are rich in selenium and cadmium; The activation rates of Cd and Se were 6.63 ~ 28.26% and 0.17 ~ 1.58% respectively; The concentration of Cd and Se in the soil of the study area may be mainly from the parent material of soil, and it is closely related to the content of organic matter in the soil. The local agricultural products are less affected by the high background value of heavy metals in the soil, and there is no excessive Cd in the agricultural products, among which potatoes and sweet potatoes have reached the standard of selenium enrichment. The research suggests that the soil rich in selenium and cadmium in the study area may come from the soil parent material, which is caused by the natural geological background and closely related to the content of organic matter in the soil. The activation rate of Cd and Se in the soil is low, which has little impact on the ecological risk of local agricultural products. This paper has important guiding significance for the development and utilization of selenium-rich soil resources in typical heavy metal high background areas.

Carbon sequestration refers to the technology of capturing carbon and storing it safely instead of directly discharging CO2 into the atmosphere. Rock salt is a promising CO2 reservoir, and the underground rock salt structure formed by salt cavern reservoirs in geological history has a natural sealing function. Storing carbon dioxide in salt caves can ensure that carbon dioxide is stably stored underground for a long time. However, at present, there are few studies on carbon sequestration in abandoned salt caves. This study analyses the characteristics of carbonate-evaporite strata in the high fold zone of eastern Sichuan and qualitatively evaluates Triassic carbonate-evaporite layers formed in the depth range of 800-3000 m in various sedimentary basins in Chongqing. A large set of carbonates-evaporites are developed in Chongqing, and the carbonate rocks near evaporites have low porosity and permeability, which can be used as CO2 storage caprock in salt cavities. Thick evaporated strata can also provide a good cover for CO2 storage in abandoned salt caves, which has great potential space resources.

A large area of soil in China is deficient in selenium (Se) and zinc (Zn)，meanwhile, Se and Zn are essential trace elements for human body, so it is of great significance to find Se and Zn rich soil to cultivate crops. Based on the data of Se and Zn in topsoil, crops and root soil obtained from 1:50000 land quality geochemical survey, this paper taking the western area of Fuling in Chongqing as the research area, studies the content and spatial distribution characteristics of Se and Zn in soil and crops, and analyzes the enrichment law of Se and Zn in agricultural crops. The results show that the average values of Se and Zn in the topsoil of the study area are 0.265mg/kg and 77.56mg/kg respectively. There are some differences in the contents of Se and Zn in different geological backgrounds, soil parent materials and soil types. The high value areas of Se and Zn are mainly distributed in the exposed areas of Triassic carbonate; in the study area, the average contents of Se and Zn in maize seeds are 0.029mg/kg and 20.752mg/kg respectively, and the enrichment rates are 96% and 82% respectively. The average contents of Se and Zn in rice seeds are 0.032mg/kg and 11.463mg/kg respectively, and the enrichment rates are 13.3% and 5% respectively. The bioaccumulation coefficients of Se and Zn in maize are higher than that in rice, and the availability of Se and Zn elements in maize root soil is higher.The results can provide geochemical basis for developing characteristic land resources, functional agriculture and promoting rural revitalization in Fuling District.

The mineralogical and geochemical compositions of the Lopingian coals from an exploratory drill core (ZK4-1) in the Zhongliangshan Coalfield, southwestern China are reported in this paper. The Zhongliangshan coals are medium volatile bituminous in rank (random vitrinite reflectance, average 1.38%), characterized by a medium-ash yield (26.84%) and high sulfur content (3.38%). Minerals in the Zhongliangshan coals are mainly composed of clay assemblages (kaolinite, the illite/smectite mixed layer (I/S) and chamosite), pyrite, quartz, carbonate minerals (calcite, marcasite, ankerite, and dolomite), and anatase, followed by rutile, jarosite, natrojarosite, bassanite, gypsum and K-feldspar, with traces of apatite, rhabdophane and barite. Compared with the average concentrations of the world hard coals, some trace elements including Li, V, Co, Cu, Se, Y, Zr, Nb, rare earth elements (REE), Cd, Ta, Hf and Hg, are enriched in the Zhongliangshan coals. The modes of occurrence of chamosite, barite, rhabdophane, quartz and calcite in the Zhongliangshan coals indicate that the coals have probably been affected by the injection of low-temperature hydrothermal fluids. Based on the concentrations of Sc, V, Cr, Co, Ni, Cu and Zn, the ratios of Al2O3/TiO2 and the upper continental crust-normalized rare earth element and yttrium (REY) distribution patterns of the Zhongliangshan coals, the dominant sediment source regions are the Leshan-Longnvsi Uplift, Hannan Upland, and Dabashan Uplift, with a small proportion of terrigenous materials from the Kangdian Upland. The K7 and the upper portion of K1 coals have the potential as raw materials for the recovery of REY. [ABSTRACT FROM AUTHOR]

Coal and coal by-products are considered as the potential raw materials for critical elements (e.g., rare earth elements, Li, Ga, Ge, etc.), which have attracted much attention in recent years. The purpose of this study is to investigate the mineralogical and geochemical characteristics, and controlling geological factors of lithium and rare earth elements in the Lopingian (Wujiaping Formation) coal from the Donggou Mine, southeastern Chongqing Coalfield, China. Results indicate that lithium and rare earth elements are significantly enriched in the Donggou coals, which could be new potential alternative sources for critical elements. Concentrations of lithium and rare earth elements in the Donggou coals gradually increase from top to bottom. Lithium is mainly associated with kaolinite, while rhabdophane, florencite, goyazite, and xenotime are the main hosts of rare earth elements. The controlling geological factor is the groundwater leaching of underlying tuff, and to a lesser extent, the terrigenous clastic materials input from the top layer of the Kangdian Upland. This study provides mineralization information for lithium and rare earth elements exploration in coal measures. [ABSTRACT FROM AUTHOR]

Abstract: Aluminum-hydroxide (boehmite)-rich Pennsylvanian coals of high volatile A bituminous rank were found previously in the Jungar Coalfield, Inner Mongolia, China. This paper reports new results on 48 bench samples of the CP2 coal from the adjacent Adaohai Mine, Daqingshan Coalfield, Inner Mongolia, and provides new insights into the origin and modes of occurrence of the minerals and elements present in the CP2 coal. Compared to the same coal in the adjacent mines, the CP2 coal in the Adaohai Mine has a higher rank (Ro, ran =1.58%), which is attributed to igneous intrusions during the Late Jurassic and Early Cretaceous Epochs. The proportion of inertinite (35.3%) in the coal is higher than that in other Late Paleozoic coals in northern China but lower than that in the Jungar coals. Minerals in the CP2 coal include diaspore, boehmite, gorceixite, calcite, dolomite, siderite, clay minerals (kaolinite and ammonian illite), and trace amounts of anatase, fluorapatite, quartz, and pyrite. Based on mineral proportions in the coal bench samples, the CP2 coal may be divided into four Zones (I to IV) from bottom to top. The major mineral in Zones I and IV is kaolinite. Zones II and III are mainly composed of ammonian illite, diaspore, boehmite, gorceixite, calcite, dolomite, and siderite. Diaspore-, boehmite-, and gorceixite-forming materials were derived from oxidized bauxite in the weathered crust of the Benxi Formation in the sediment-source region during peat accumulation. However, gorceixite may have formed earlier than diaspore; the diaspore was derived from gibbsite that was subjected to dehydration by the heat of the igneous intrusions. The ammonian illite may have been formed at a relatively high temperature by interaction of kaolinite with nitrogen released from the organic matter in the coal during metamorphism caused by the igneous intrusion. The calcite and dolomite occur as epigenetic cell- and fracture-fillings and were probably derived from the igneous fluids. Compared to the common Chinese and world coals, the CP2 coal is enriched in CaO (1.69%), MgO (0.32%), P2O5 (0.214%), F (207μg/g), Ga (16.3μg/g), Zr (446μg/g), Ba (276μg/g), Hg (0.33μg/g), and Th (12.4μg/g), but has a lower SiO2/Al2O3 ratio due to the higher proportions of diaspore, boehmite, and gorceixite in the coal. The F occurs mainly in gorceixite and fluorapatite. The major carriers of Ga are diaspore and kaolinite but not gorceixite. Barium mainly occurs in gorceixite and barite. Mercury was probably derived from the igneous intrusion and is distributed in both the organic matter and the minerals. The elements are classified into five associations by cluster analysis, Groups A, B, C, D, and E. Group A represents a REE-Be-Y-Se-Ga-Ge-Sc-In-Pb-Bi-Nb-Ta-TiO2-W-Hg-Sb-Zr-Hf-Th-U association. Most of the elements in Group A are lithophile elements that occur in aluminosilicate minerals. Group B (Sn-Te-Zn-Cd-V-As-Cr-Cu-Mo-Ni-Re) is weakly correlated with ash yield and is associated with unidentified trace sulfide minerals. Elements in Group C (Ad-Na2O-Al2O3-SiO2- Li-K2O-Rb-Cs-Tl association) probably occur in the clay minerals and diaspore. Group D consists of P2O5, Ba, F, Sr, S, and Cl, and with the exception of S, they occur in minerals (gorceixite and fluorapatite). Oxides of Fe2O3-MnO-CaO-MgO make up Group E and mainly occur in the carbonate minerals. The coals are enriched in light REEs and the LREEs–HREEs have been highly fractionated, with an average (La/Yb) N of 8.71. The heavy REEs in the coals have a stronger organic affinity than the LREEs. [Copyright &y& Elsevier]