Abstract:Comparable studies were conducted between chemical oxidation and microbial oxidation of ferrous sulfate by a mixed culture of Acidithiobacillus ferrooxidans in the presence of different concentrations of As(Ⅴ). Eh, pH and Fe2+ concentration were monitored periodically and the final precipitation was analyzed by X_ray diffraction (XRD) and SEM. The data obtained showed and chemical oxidation of Fe2+ was very slow with a final oxidizing ratio of <8% and As(Ⅴ) had no effect on Fe2+ oxidation chemically. Slight enhancement of Fe2+ oxidation was observed by 100 mg/ L As(Ⅴ) in the microbial system. Complete oxidation of Fe2+ could be reached in about 60 hours in the presence of A. ferrooxidans with 500 mg～1g/L As(Ⅴ). However, microbial Fe2+ oxidation was greatly inhibited by 4g/L As(Ⅴ) and about 106 hours were needed for complete oxidation. Initial mole ratios of 100 As/(As+S) affected the final solid phase and the crystallization of the precipitation. In the microbial system, typical symmetric peaks of jarostie were clearly distinguished in the precipitates with ≤ 1g/L As(Ⅴ) but the crystallization was decreasing with the increase of As(Ⅴ) concentration. Only amorphous solid was observed in the precipitate with 4g/L As(Ⅴ). Elemental mapping indicated that As was evenly distributed in the precipitates either by adsorption or by structural incorporation during the iron oxidation. These results provide important information for the treatment of As contamination in AMD regions.

Abstract:Three bacteria strains resistant to arsenic(Ⅲ), named WK_21, WK_31 and WK_32, were enriched with 2×10-3 mol/L NaAsO2 and isolated on plates from the three pieces of rock (or soil) samples from Yangshancdhong mine tailing dumps of Tonglin in Anhui Province. These strains are all aerobiotic and have a high resistance to arsenic(Ⅲ), and are respectively resistant to the most arsenic(Ⅲ) of 32, 56 and 50 mmol/L after being cultivated for 48 hours on the solid LB medium. Through a study of their growth in different concentrations of arsenic(Ⅲ), the authors found that the arsenic of low concentration made a small impact on or even slightly promoted the bacteria's growth and that, when the concentration of arsenic(Ⅲ) increased, the suppression of the growth was clearly enhanced. Based on a careful observation of the three strains' morphological characteristics, physiological and biochemical characteristics and 16S rDNA sequences, the authors identified the three strains as Arthrobacter sp., Rhodococcus equi and Paenibacillus sp., respectively. Since these arsenic_resisting strains were isolated from the soil samples of mine tailing dumps, the data obtained are likely to provide valuable materials for further studies of the environmental microbial remediation in the same kind of areas polluted by heavy metals and the mechanism for microbial resistance to heavy metals.

Abstract:Bacteria strains with Cr (Ⅵ) tolerant capacity were isolated from chromium_contaminated tannery sludge and the Cr (Ⅵ) removal characteristics of these isolates were studied. Twenty strains with the Cr (Ⅵ) removal efficiency greater than 50% under the condition of 50 mg/L Cr (Ⅵ) were obtained. These strains were closely related to species in the genera Acinetobacter, Microbacterium, Leucobacter, Ochrobactrum and Brachymonas by their 16S rRNA gene sequences. The effects of growth phase, pH and Cr (Ⅵ) concentration on the Cr (Ⅵ) reducing capacity for seven isolates were investigated. Cells with high activity showed higher Cr (Ⅵ) removal efficiency. pH affected the Cr (Ⅵ) removal capacity of these strains remarkably. The Cr (Ⅵ) removal efficiencies of strain No. 16 and No. 21, closely related to the species in the genus Microbacterium, were over 80% at the pH of 7～8 under the condition of 50 mg/L of Cr (Ⅵ). High concentration of Cr (Ⅵ) repressed the Cr (Ⅵ) removal capacity. However, strain No.21 showed a removal efficiency of about 80% when the initial Cr (Ⅵ) concentration was 110 mg/L.

Abstract:The energy exchange between natural semiconductor minerals and chemoautotroph microbes was investigated in details in this paper. Photo_electrochemical experiments indicate that the photoelectrons generated by natural semiconductor minerals in solar light can reduce ferric ion to ferrous ion. The reduction efficiency of natural rutile is 12.5% and that of natural sphalerite is 7.86%. This process, which is driven by the photo_catalysis of natural semiconductor minerals, realizes the energy transformation from solar energy to electric energy and finally to chemical energy as stored in the form of ferrous ion. The potential control experiment shows a linear relationship between the amounts of cell growth (A.f.) and the electrons needed for ferrous reduction. Meanwhile the amount of A.f. with electrons flowing in is 4.41 times greater than that of the control group. This process realizes the energy transform from chemical energy to biomass energy by microbe metabolism. Further experiments, which integrate the two processes by an electrochemical cell, indicate that the logarithm growth period of A.f. is extended from 36 h under the dark condition to 72 h under the light condition. Meanwhile, an obvious improvement of cell growth is observed. The concentration of A.f. under the light condition is 1.90 times higher than that under the dark condition when the mineral is sphalerite, while the number is 1.69 times higher when the mineral is rutile. The results demonstrate that the growth of chemoautotroph microbes can be favored by an indirect utilization of solar energy under the assistance of semiconductor photo_catalysis, thus realizing the energy transformation from solar energy to electric energy, chemical energy and finally to biomass energy.

Abstract:The effect of natural limonite on the growth of Acidithiobacillus ferrooxidans was studied through control experiments. The main phases of the natural limonite sample used in the experiments were identified as the mixture of goethite and hematite by X_ray diffraction analysis (XRD). UV_vis diffuse reflectance spectra and time_current curve under different irradiation conditions indicate that natural limonite has a good photoelectrochemical response. Dual_chambered system reactions were carried out with an “H"_type device. The results of three sets of control experiments show that A.f. grows better when external electrons are supplied by the photocatalysis of semiconductor minerals. Within 96 h, the cell density increases by 12 times. The variation of Fe2+ concentration is consistent with the growth curve of A.f. in control experiments, which reveals that natural limonite indirectly improves the growth of A.f. The mechanism can be interpreted as follows: Natural limonite can produce photo_generated electron_hole pairs under the visible light. The photo_generated hole is captured by the electron donor of ascorbic acid, while the separated photo_generated electrons transfer into cathode chamber to reduce Fe3+ to Fe2+. The process achieves the electrochemical regeneration of Fe2+, which provides adequate electron energy for the growth of A.f.

Abstract:The reductive decolorization of azo dye wastewater was investigated by using a dual_chambered bioelectrochemical cell equipped with different cathode materials (graphite and rutile_coated graphite). The experimental data show the feasibility of electricity generation by utilizing the model azo dye of methyl orange (MO) as the cathodic electron acceptor along with the color removal. Compared with MO reduction in traditional microbial fuel cell (MFC), an increase of the efficiency for MO reduction as well as the electricity production was successfully achieved in the irradiated rutile_cathode system. Quantification of the internal resistance by fitting the electrochemical impedance spectra (EIS) data to an equivalent circuit showed that the polarization resistance (Rp) of rutile_cathode significantly decreased from 1378 Ω (dark control) to 443.4 (light control) Ω. The results demonstrate that the cathodic electron transfer process in the irradiated rutile_cathode system is driven by the photocatalysis of rutile. The photoreduction of MO at different initial concentrations obeys the pseudo_first_order kinetics, and the reaction constant increases with the decrease of the initial concentration of the dye. Based on an analysis of decolorization products, the authors put forward a possible cathodic reaction mechanism for the photoreductive decolorization of MO, i.e., the azo bond of MO is cleaved by photoelectrons at the irradiated rutile_cathode, resulting in the formation of colorless hydrazine derivative.

Abstract:Seven bacteria strains were isolated from the samples of an acid mine drainage stream in the Shizishan sulfide mine, Tongling, by using the overlay technique with four selective media of YE, Feo, FeSo and FeTo. The 16S rRNA gene sequences were amplified from total DNA of bacteria strains and were then sequenced and analyzed．The phylogenetic tree analysis with 16S rRNA gene sequences of isolated bacteria strains was carried out. The results show that every isolated bacteria strain can be divided into three microbial communities, namely heterotrophic acidophiles, autotrophic acidophiles and moderately acidophilic iron_oxidizing bacteria. The function of heterotrophic acidophiles lies in the dissimilatory ferric iron reduction and the creation of an oligotrophic environment. Autotrophic acidophiles can oxidize iron and sulfur elements in acid mine drainage, being producers of the acid mine drainage ecological system. Moderately acidophilic iron_oxidizing bacteria can oxidize ferrous iron and generate some insoluble minerals to realize the dynamic balance of iron element between the acid mine drainage and the sediments.

Abstract:Extracellular polymeric substances (EPS) seem to play an important role in bioleaching. Generally, EPS consist of neutral sugars, lipids, a small amount of amino acid and some metabolites such as organic acid. In this paper, glucose, arginine, glucuronic acid and citric acid were used to study the effects of different components of EPS on the leaching of pyrite and indicate the facilitation of the direct contact between microbes and minerals on bioleaching. The iron contents of the experimental solution were measured in order to determine the dissolving rate of pyrite, and scanning electronic microscopy was employed to observe the changes of the surface characteristics of the pyrite. Some preliminary data obtained indicate that some kinds of components of EPS, such as glucuronic acid and citric acid, can promote the dissolution, while sugars and arginine suppress the decomposition, which may be attributed to their surface coating on the pyrite surfaces.

Abstract:The adsorption of heavy metals on bacteria is often employed in the remediation of various contaminations. Nevertheless, the difference in the adsorption behaviors of the bacteria of different growth stages has not yet been systematically studied. Based on the adsorption experiments of Cu2+on Acidothiobacillus ferrooxidans at different growth stages, it is found that the adsorption capacity of the bacteria at the logarithmic stage is slightly higher than that of the stationary stage. The adsorption on the bacteria at the logarithmic stage and at the stationary stage can be described by Freundlich equations, implying its high surface heterogeneity. In addition, a negative correlation between the adsorption amount of bacteria and the pH of solution can be observed. Therefore, the displacement reaction between Cu2+ and surface proton of the bacteria may constitute the adsorption mechanism. The changes in surface chemistry of the bacteria at different growth stages are considered to be responsible for the difference in adsorption behaviors.

Abstract:Employing the dialysis method, the authors designed experiments to probe into the effect of adhered Paenibacillus polymyxa on the dissolution of minerals within basalt as well as the effect of temperature on such adhesion_mediated dissolution. The results of ten days' experiment show that the dissolution of basalt is highly promoted by P. polymyxa and its metabolites at 30 ℃, with Fe, Mg and Mn being released mainly from olivine and Ca and Al from augite and feldspar. At 5 ℃, however, the promotion is very insignificant. Adhered bacteria and metabolites are advantageous to the release of Mg, Fe and Mn but disadvantageous to that of Ca. The reason is that these two groups of elements are released through different mechanisms which are diversely affected by adhered bacteria. The release of Al is insignificantly affected by the adhesion of bacteria. At 5 ℃, the adhered bacteria have no effect on element release.

Abstract:Schwertmannite, characterized by small particle size, high specific surface area and strong surface adsorption energy, is a common secondary mineral formed during the supergene oxidation of sulfides. Due to its adsorption capacity, it can affect geochemical behaviors of heavy metals and microorganism. This study has focused on the adsorption of Cu2+ and Acidothiobacillus ferrooxidans cells on the chemically synthesized schwertmannite. It is observed that the adsorption of Cu2+ and Acidothiobacillus ferrooxidans on schwertmannite is remarkable, and the biosorption process of Cu2+ is well consistentwith the Langmuir model. The biosorption process of Acidothiobacillus ferrooxidans, however, is consistent with the Freundlich model instead of with the Langmuir model. It is deduced that the formation of schwertmannite in the ore_formaing environment can strongly affect geochemical behaviors of heavy metals and microorganism and may also affect the decomposing rate of metal sulfides.

Abstract:During the preparation of ferric hydroxide with acid leaching filtrate of tailings, schwertmannite is formed because of the formation of a high SO2-4 and high Fe environment with pH values from 2.8 to 3.8 resulting from the gradual dropping of the lye into the filtrate. Schwertmanntie is a metastable mineral, which is transformed into a more stable goethite (iron hydroxide) with the variation of time and system environment. The influence of pH value, temperature and time on the transformation was investigated, and the results show that, under the condition of 60℃, the transformation process in the solution with pH value of 12 for 36 hours can fully convert the schwertmannite into Fe(OH)3.

Abstract:The bio_desulfurization of coal technology is one of the important research topics both at present and in future. In this study, the silicate bacteria growing in media that contained high_sulfur coal were used to remove sulfur in coal. The results show that the silicate bacteria could be used to desulfurize high_sulfur coal. Total sulfur content was reduced from 5.45％ to 3.45％ after the treatment. The total sulfur removal rate reached 36.70％, in which the effective removal rate reached 9.91％. Compared with the static cultivation manner for silicate bacteria, the shake cultivation manner shows much better desulfurizing effect on coal. The silicate bacteria cultured in nitrogen_containing culture media show better desulfurization effect than those cultured in nitrogen_free media. Preliminary data obtained indicate that the silicate bacteria not only cause oxidation of sulfide iron_sulfur in coal, but also result in absorption and metabolism of the organic sulfur and inorganic sulfur in coal. It is suggested that there exist two mechanisms for coal desulfurization by the silicate bacteria: ① silicate bacteria and their metabolites result in sulfur oxidation in coal; ② the sulfur in coal experiences absorption and metabolic conversion by the silicate bacteria. There are two kinds of mechanisms which have the effect on all forms of sulfur in the coal sample. The study also implies that silicate bacteria have the latent application potential in the study of coal desulfurization.

Abstract:The proteins in lapillu and asteriscu of wild carp from the Miyun Reservoir in Beijing were extracted. According to the difference in solubility, the proteins can be classified into three groups, namely, water soluble protein(WSP), acid soluble protein(ASP) and acid insoluble protein(AIP). Using high performance liquid chromatography (HPLC), X-ray diffraction(XRD) and Fourier transformation infrared spectra（FTIR）, the authors characterized the sorted proteins from different otoliths. It is found that the three types of proteins in lapillus and asteriscus have different characteristics, and such differences may be responsible for different kinds of crystalline state in calcium carbonate.

Abstract:Micro_CT technology and LA_ICP_MS were applied to studying the response relationship between carp otolith and heavy metals in waters. The LA_ICP_MS analysis has revealed that the contents of Cu and Pb of otoliths in Baiyangdian are higher than the contents of corresponding elements of otoliths in the Miyun reservoir, and the Micro_CT data show that the Micro_CT value of otolith from the Baiyangdian is higher than that from the Miyun Reservoir. The authors consider that the contents of Cu and Pb seem to be the main factors responsible for the difference of Micro_CT values of otolith from different waters. Elements in otolith show similar trend and enrichment to the corresponding elements in the water. It is thus inferred that there exists a coupling relationship between heavy metals in water and Micro_CT data, which can be used as a typomorphic characteristic to indicate the information of heavy metals in water.

Abstract:Freshwater pearls (aragonite pearls) were selected as the main experimental materials to study the biomineralization of calcium carbonate. Two kinds of soluble matrix proteins, i.e., acid soluble protein (ASM) and water soluble protein (WSM), were extracted from aragonite pearls to prepare a series of aqueous solutions with different concentrations. In vitro study was carried out by using the above_mentioned aqueous solutions with different concentrations in the diffusion method. The effects of concentrations of ASM and WSM aqueous solutions were discussed in the controlled crystallization of calcium carbonate. Scanning electron microscopy (SEM) and Raman spectroscopy were used to observe and analyze the results of in vitro biomineralization of calcium carbonate. The results show some differences in regulation and controlled crystallization of CaCO3 between ASM and WSM aqueous solutions. The concentration of ASM aqueous solutions seems to play an important role in controlling the crystal morphology and size of calcium carbonate but it has no effect on polymorphism, while the polymorph, morphology and size of crystals are obviously influenced by the concentration of WSM aqueous solutions.

Abstract:Both mineral granules and microorganism individuals are important components of atmospheric particulate matter (PM), having high relationship in morphology, association and aerodynamic behaviors. This paper has expounded the granule characteristics, free radical and biological activity as well as the effect of interaction between IP, IMG and microorganisms and pointed out the importance of the interaction between atmospheric particles and microorganisms. In future, the emphasis of the study should be placed on environmental chemistry and microorganism behaviors, the size effect and boundary film effect in the near size effect system of the IMG_microorganism system on surface morphology, surface electrical property, surface group and free radical of mineral particles, the relationship of the secretion of protein to the phase transition, the element variable valence and the solution (complexation) as well as the diversification of particle activity and biological toxicity caused by these factors.

Abstract:Ovarian cancer is one of the common malignant tumors in female reproductive organs. Psammoma bodies occurring in cell population is considered to be a phenomenon of ovarian serous carcer. In this paper, psammoma bodies from ovarian serous carcinomas were investigated by using SEM, EDAX, XRD, FTIR and HRTEM. The results show that the mineralized matter of the psammoma bodies with the concentric lamellated structure is composed of nano_size whewellite and carbonate hydroxylapatite. The former is deposited in the inner part of the psammoma body in a relatively high crystallinity, whereas the latter in the outer part in a low crystallinity.

Abstract:The mineralization of the psammoma body has a high specificity in diagnosing papillary thyroid carcinoma, and an analysis of its mineral composition may provide some support information on the origin and development of the disease. Focusing on the concentric lamellated calcified bodies in papillary thyroid carcinoma, the authors used ESEM, EDAX, EPMA, FTIR and HRTEM to investigate the morphology, structure and mineral composition of the sample. The results show that the concentric lamellated structure has genetic characteristics of micromicellae, and that the psammoma bodies are composed of nano_size carbon hydroxyapatite and some amorphous calcium phosphates with relatively low values of Ca/P（At%）. The Ca, P and Ca/P（At%）in the psammoma body have an increasing tendency inwards.

Abstract:The micro_structure of natural rutile heated and annealed under argon atmosphere was studied by means of X_ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). The results indicate that the lattice of heated rutile specimens was expanded, and ilmenite appeared when the heating temperature reached 900℃ and 1000℃. Like rutile, ilmenite is a kind of natural semiconductor mineral. It grew in the direction at a 31°angle with rutile's (010) planes and formed dual coupled semiconductor with rutile. The results of the UV_vis test indicate that the appearance of ilmenite in the rutile sample can effectively enhance the photocatalytic activity of the specimens.

Abstract:In this study, the natural vanadiferous and ferruginous rutile was modified by heat treatment with the temperatures ranging from 500～1000℃ under the condition of argon atmosphere. XRD patterns of treated samples have revealed that there exist different levels of cell expansion with the increasing temperature, and a new phase, ilmenite, is formed above 900℃. The UV_vis diffuse reflection spectra show that the visible absorption is distinctly improved after argon heat treatment. Compared with the previous modification under air atmosphere, the heat treatment under argon atmosphere proves to be more efficient in raising the visible light response.

Abstract:An experimental study of the adsorption of clay minerals such as montmorillonite, illite, kaolinite and sepiolite for Cd2+ was conducted. The results indicate that acidity and ion intensity are factors affecting adsorption,that the adsorption reaction is rapid, and that adsorption kinetics is fitted well with the Lagergren quasi_second reaction rate model. Under the optional conditions, the adsorption of kaolinite for cadmium is weak, and the saturated adsorption capacities of montmorillonite, illite and sepiolite for cadmium are 2.88，1.08 and 2.82mg/g respectively. The behaviors of adsorption of Cd2+ on montmorillonite are fitted to Freundlich Model, while the behaviors of adsorption of Cd2+ on illite and sepiolite are fitted to Langmuir Model. Correlation analysis shows that the saturated adsorption capacity of cadmium on silicate clay minerals is related to its physical and chemical properties, and the correlation between manganese oxides and the saturated adsorption capacity of cadmium is extremely significant.

Abstract:The adsorption of organic contaminants in soil is one of the most important factors affecting the migration and transformation process of these organic contaminants. Using batch experiments, this paper studied the adsorption behaviors of Trichloroethylene (TCE) in soil samples with different contents of organic carbon. The results indicate that the adsorption capacity is significantly correlated with different contents of organic carbon. There exist critical threshold values （foc*） of organic carbon contents. The minimum foc* and the maximum foc* are equal to 0.702% and 1.831%, respectively. The TCE adsorption capacity does not vary greatly with the increasing of organic carbon contents when foc is lower than 0.702%. Nevertheless, the TCE adsorption capacity varies considerably with the increasing of organic carbon contents when 0.702%

Abstract:With the aid of the N2 isothermal adsorption technology, the authors calculated the specific surface area and the pore radius distribution of sepiolite, zeolite diatomite and attapulgite by using the BET method, and the results showed that the specific surface areas were 81.56, 2.46, 1.68 and 187.70 m2/g, whereas the pore radius distribution values were 8.53, 18.20, 31.57 and 11.79 nm, respectively. Their maximal absorbing moisture values were 5.6%, 2.2%, 1.8%and 6.0%, respectively, at 25℃ and 75% relative humidity. After the saturation of the absorbing moisture, the samples of these four kinds of minerals were put in the environment of 25℃ and 35% RH to make moisture discharge. The capacities of desorbing moisture were 4.4%, 1.8%, 1.6% and 5.0%, respectively. A comparison of the specific surface area and pore radius distribution of the four inorganic porous minerals with their capacities of absorbing and desorbing moisture in the air demonstrates that the sample whose specific surface area is relatively large and whose pore radius distribution is consistent with the computation result of Kelvin formula, such as sepiolite, has comparatively strong absorbing and desorbing moisture capacity in the air.

Abstract:The adsorption isotherms of such organic dyes as methylene blue, crystal violet and aniline blue in water on palygorskite based on the purification of Jingyuan palygorskite clay were studied through static adsorption experiments, with a discussion on the thermodynamic characteristics. The results show that the equilibrium of the three kinds of dyes can be reached in about 30 minutes in the range of experiment temperatures, the adsorption isotherms of these three dyes on purified palygorskite fit Langmuir model fairly well, and the saturated adsorption capacities from Langmuir models are in order of crystal violet＞methyleneblue＞aniline blue. The adsorptions of the three dyes are all endothermic processes, the adsorption enthalpies of methylene blue, crystal violet and aniline blue are 15.52, 9.26 and 2.59 kJ/mol, respectively; the adsorption Gibbs functions vary in the range of -35～-30kJ/mol and the adsorption entropies are all positive values. The adsorption processes are spontaneous.

Abstract:Aqueous suspension rheology of three kinds of palygorskite clays from Jiangsu and Anhui was investigated as a function of the composition of clays, and different concentrations of NaCl solution，pH, different electrolyte solutions, dosages of dispersant, and linear methods were applied for fitting the rheological parameters to Casson model. The results show that small amounts of other impure minerals do not affect the rheological properties seriously, and that the samples subjected to crushing from the original clays are in line with the Casson model. The sizes of clays, pH values, different electrolyte solutions, and the addition of dispersant can affect the rheological properties, and the addition of dispersant is the most important affecting factor. Nevertheless, the effect of the concentrations of NaCl solution is not significant.

Abstract:Potassium acetate/metakaolinite intercalated composites were successfully prepared by mechanical grinding at the room temperature. The structure of me takaolinite before and after the intercalation was studied by XRD, FTIR and TEM.It was found that potassium acetate was first coordinated with water molecules and then moved into the interlayer of metakaolinite by mechanical grinding, resulting in the expansion of metakaolinite layers. During the heat treatment, water volatilization also led to the expansion of metakaolinite layers. In intercalated composites, acetate ions were coordinated with the gibbsite_type layers through water molecules bridging. Besides, the hydrated K+ cation stayed near the silica-type layers with the negative charge so as to keep charge balance.

Abstract:The aluminate cement clinker was successfully synthesized from starting materials of barium carbonate, alumina and calcium carbonate by designing mineral phase composition sintered at different temperatures. The formation mechanism of cement clinker was investigated by XRD and SEM. The results show that BaAl2O4 is mainly formed at relatively low temperatures, and then CaAl2O4 obviously increases with the increase of temperature in forming solid solution of BaAl2O4 and CaAl2O4. In addition, there exists a small amount of Ca12Al14O33, CaAl2O4 and Ca3Al2O6 .in cement clinker. BaAl2O4 is mostly present in the shape of puncheon, and solid solution of BaAl2O4 and CaAl2O4 is developed into hexagon and round crystals.

Abstract:Based on an analysis and study of the development of medical geology and geoheritage, the authors put forward for the first time the concept of medical geoheritage. Medical geoheritages in China are mainly distributed along the zone from Northeast China through Taihang Mountain, Loess plateau, Wuling Mountainand Sichuan basin to Yunnan-Guizhou plateau, with complex topographic characteristics and fault tectonic belts. Medical geoheritages can be classified into five types on the basis of pathogenic elements, namely, selenium deficiency (Keshandisease, Kaschin_beck disease), selenosis, iodine deficiency disorders (endemicgoiter), endemic fluorosis and carcinogenic geochemical elements. With natural geological attributes and scientific values as the main evaluation factors, the authors built the assessment system of medical geoheritage. The assessment of the selenosis medical geoheritage in Enshi indicates that this assessment system is practicable and operable

Abstract:This paper deals with the composition, structure and some other features of rectorite and gives a detailed account of the research progress in such aspects of rectorite modification as Na modification, organic modification and inorganic modification. Some suggestions are also made for further researches on rectorite modification.