Cong-Qiang Liu

Soil Heavy Metal Pollution Around the Dabaoshan Mine, Guangdong Province, China

Soil contamination in the vicinity of the Dabaoshan Mine, Guangdong Province, China, was studied through determination of total concentrations and chemical speciation of the toxic metals, Cu, Zn, Cd, and Pb, using inductively coupled plasma mass spectrometry. The results showed that over the past decades, the environmental pollution was caused by a combination of Cu, Zn, Cd, and Pb, with tailings and acid mine drainage being the main pollution sources affecting soils. Significantly higher levels (P ≤ 0.05) of Cu, Zn, Cd, and Pb were found in the tailings as compared with paddy, garden, and control soils, with averages of 1 486, 2 516, 6.42, and 429 mg kg−1, respectively. These metals were continuously dispersed downstream from the tailings and waste waters, and therefore their concentrations in the paddy soils were as high as 567, 1 140, 2.48, and 191 mg kg−1, respectively, being significantly higher (P ≤ 0.05) as compared with those in the garden soils. The results of sequential extraction of the above metals from all the soil types showed that the residual fraction was the dominant form. However, the amounts of metals that were bound to Fe-Mn oxides and organic matter were relatively higher than those bound to carbonates or those that existed in exchangeable forms. As metals could be transformed from an inert state to an active state, the potential environmental risk due to these metals would increase with time.

Major- and trace-element compositions of Cenozoic basalts in eastern China: Petrogenesis and mantle source

The studied Cenozoic basalts from eastern China have SiO2 contents ranging from 38.63 to 55.24 wt%, and Na2O + K2O from 3.1 to 9.4 wt%. They may be divided into three main types — tholeiitic, alkalic and potassic magmas. Variable trace-element abundances, together with the diverse major-element compositions, suggest that their origins involve both partial melting of mantle rocks at different depths, and subsequent fractional crystallization of clinopyroxene and olivine. Variations in the ratios of highly incompatible elements of the basalts in eastern China demonstrate two mantle components. The enriched mantle component, primarily represented by the basalts in NE China, show high LILE/Nb, Ba/Th, Ba/U, Th/U and low La/Ba ratios, typical of the Walvis Bay Ridge, Gough and Tristan da Cunha oceanic island basalts (OIB). These trace-element features support the identification of EM1 in their mantle source previously made by G.H. Xie and coworkers using Sr, Nd and Pb isotopes. This Dupal mantle source is inferred to be lithospheric and related to metasomatism during subduction, rather than due to the direct incorporation of continental crustal material into the mantle. The second component is represented by basalts from SE China which have the trace-element signatures of normal OIB, i.e. they do not have a Dupal anomaly. It appears most likely that upwelling of the asthenosphere and magma ascent induced the melting of overlying heterogeneous mantle lithosphere to generate the Cenozoic basalts of eastern China.

Environmental concerns related to high thallium levels in soils and thallium uptake by plants in southwest Guizhou, China

Thallium (Tl) contamination in soils poses a significant threat to human health due to the high toxicity of Tl and its ready assimilation by crops. This study is focused on high concentrations of Tl in soils in the Lanmuchang area of southwest Guizhou, China, which is related to natural processes of Tl-rich sulfide mineralization. Thallium contents range from 40 to 124 mg/kg in soils originating from the mining area, from 20 to 28 mg/kg in slope wash materials, from 14 to 62 mg/kg in alluvial deposits downstream, from 1.5 to 6.9 mg/kg in undisturbed natural soils and <0.2 to 0.5 mg/kg Tl in soils from the background area. These values indicate that both the erosion of natural soils from the Tl mineralized area and the mining activity are responsible for the distribution of high Tl concentrations in soils. Two other important toxic metals of interest, mercury and arsenic, also show high contents in soils, and are generally higher than Tl concentrations. Thallium concentration in plants exhibit species-dependent preferences. Thus, the enrichment of Tl in the edible parts of crop species decreases in the following order: green cabbage>carrot>chili>Chinese cabbage>rice>corn. The highest level of Tl in green cabbage is up to 500 mg/kg as dry wt., surpassing the values of Tl in the soils in which the green cabbages grow. In contrast, Hg and As are relatively less concentrated in local plants. The average daily uptake of Tl by the villagers of the Lanmuchang area through consumption of locally planted crops has been estimated to be 1.9 mg/person, which is 50 times the daily ingestion of individuals from the Tl-free background area. The daily ingestion of As and Hg from the study area are 0.03 and 0.01 mg, respectively. This indicates that Tl in the contaminated soils related to the natural Tl mineralization is being readily transferred to the human body through the food chain, and poses a significant threat to the health of the local villagers. Arsenic may pose a lesser health hazard, but mercury has an insignificant health risk. This study illustrates a real environmental concern related to land use and human health in areas containing high contents of Tl in soils associated with the natural occurrence of Tl-rich sulfides and coals, with or without mining activities. Thallium contamination in soils should be a critical parameter for proper land use and health related environmental planning and regulations.

A geochemical study of loess and desert sand in northern China: Implications for continental crust weathering and composition

Abstract Chemical compositional variations of desert sands and loess, loess-like deposits, river deposits and saline lacustrine deposits collected mostly from the southern margin of the Taklimakan Desert, China, provide strong constraints on the chemical weathering processes of continental crust, and also on the provenance compositions of these Quaternary deposits. Constant but lower concentrations of Al relative to the average upper continental crust (UCC) in these Quaternary deposits could be attributed to chemical weathering of Al-rich minerals such as feldspar and mica, and removal of clay minerals by wind and water. Large variations of mobile Na, Ca, Mg and Sr compared to relatively immobile Al, K and Ba resulted from the chemical weathering of plagioclase and carbonate minerals, salinization and carbonation of the arid lands. Most trace elements are not significantly fractionated. Their variations in absolute concentration are caused by the dilution of quartz, evaporates and carbonate minerals. Variations in Sn concentrations probably depend on relative contents of some heavy minerals. High Sr/Ba, low Th/U, K/Cs ratios of the saline lake deposits suggest differences in aqueous chemistry of these elements. The occurrence of the M-type tetrad effect (a REE pattern with four convex curves) of REE compositions, found mainly in the river deposits, is considered the result of water-particle interaction during chemical weathering of crustal materials. Y/Ho ratios of these samples are significantly higher than those of chondrite and the UCC. This suggests different chemical behavior of these two elements, and possibly the enrichment of carbonate materials. The low LREE/HREE feature of the saline lake deposits can be interpreted as due to the different aqueous chemical behavior of the REEs. However, it can also be reasonably considered as the result of inheritance from their provenance, since LREE and LREE/HREE variations may be related to the geological setting of the source. According to some elements that are not significantly fractionated, the average provenance composition of these Quaternary deposits are probably characterized by enrichments of Ni, Cr and V over Fe, higher La/Th, lower La/Sc and Th/Sc, and lower Ta/W and Nb/W ratios, compared with the UCC composition.

Isotope geochemistry of Quaternary deposits from the arid lands in northern China

Abstract Quaternary deposits of various types (lacustrine, desert sand, river, loess and loess-like deposits) from the southwestern Tarim Basin, North Tianshan, northeast China and the central Loess Plateau exhibit an ϵNd(0) range from −5 to −12.8 and a 147 Sm 144 Nd range from 0.110 to 0.140. Their Nd-depleted mantle model ages are between 1.50 and 1.92 Ga, with a mean value of 1.7 Ga. Th Sc ratios vary over a wide range from 0.1 to 2. Comparison of these geochemical signatures with those of the old Australian shales and modern Pacific Ocean dust suggests a continuous input of mantle-derived material into the crust over geological time. The deposits from the North Tianshan show clearly different chemical and isotopic features, with significantly higher Sm Nd , high 143 Nd 144 Nd , low 87 Sr 86 Sr , and low La Lu and Th Sc ratios relative to those in the deposits from the other areas. This indicates a geological control on the local source, which has an overall young age and an enrichment of basic components. The ϵCe(0) values of two loess samples from the central Loess Plateau are +1.8 and 3.9, corresponding to depleted mantle model ages of 2.2 and 3.4 Ga. Like the RbSr system, the evolution of the LaCe isotopic system in the crust may be to some extent decoupled from the SmNd system, due to La Ce fractionation by sedimentary processes. The loess deposits and the desert sand are not distinguishable in isotopic composition, but show somewhat different chemical compositions. We conclude that the loess can have originated from desert processes, since the difference in the chemistry of the desert sand and loess may result from mineral sorting during desert processes and aeolian transportation. The loess deposits on the central Loess Plateau chemically and isotopically resemble the desert loess deposits in the southwestern Tarim Basin but do not resemble those of the North Tianshan. Accordingly, the loess on the plateau may have a source region in the Tarim Basin but clearly not in the North Tianshan.

Mobility of heavy metals associated with the natural weathering of coal mine spoils

Knowledge of chemical mobility of heavy metals is fundamental to understanding their toxicity, bioavailability, and geochemical behavior. In this paper, two different methods, i.e. mineralogical means and sequential extractions, were employed to analyze the total contents, existing states, and chemical forms of heavy metals in coal mine spoils. The results demonstrate that the mobility of heavy metals in coal mine spoils depends not only on their existing states and the stability of their host minerals but also on the properties of the coal mine spoils. In the process of coal mine spoils-water interaction, sulfides that contain heavy metals first break down and release metals, which are then adsorbed and complexed by the iron oxyhydroxide colloid resulting from pyrite oxidization and organic matter. During the natural weathering of coal mine spoils, only a small fraction of these metals are released to the environment, and most of them still remains in the residual material.

Chronic toxicity of rare-earth elements on human beings: implications of blood biochemical indices in REE-high regions, South Jiangxi.

Blood analyses for rare-earth element (REE)-high background regions in South Jiangxi show that the population averages of many of the biochemical indices deviate markedly from normal values in the normal region. These deviations are thought to be caused by prolonged intake of REE through food chains in view of that the toxicity of other harmful metals such as Pb and Cd can be neglected because of their insignificant amounts in the environment. In comparison with the normal region, blood biochemical indices abnormal in the REE-high regions are manifested as low total serum protein (TSP), albumin, β-globulin, glutamic pyruvic transitanase, serium triglycerides, and immunoglobulin, but high cholesterol. These deviations may be related to the REE concentration and composition of food chains, and are sex dependent. Certain blood indices (such as TSP) of different age groups in the LREE-high region indicate that the influence of REE on males is a one-way irreversible process, whereas females show a strong ability of restoration.

The occurrence of chloramphenicol and tetracyclines in municipal sewage and the Nanming River, Guiyang City, China

The occurrence of antibiotics including chloramphenciol (CAP), oxytetracycline (OTC) and tetracycline (TC) was studied in municipal sewage, river water and sediment. Temporal and spatial variations of antibiotic concentrations in municipal sewage, river water and sediment were evaluated. In municipal sewage, CAP, OTC and TC concentrations were in the range of 5.8-47.4, 0.16-5.7 and 0.7-65.2 microg L(-1), respectively, and showed a temporal variation with high antibiotic concentrations appearing in the cold season. Untreated municipal sewage can seriously influence both river water and sediment. Generally, high antibiotic concentrations in river water appeared in winter owing to the low flow condition as well as the high antibiotic concentration in the sewage. However, high CAP and OTC concentrations in sediment were observed in summer most likely because runoff in high flow season can carry wastes from some origins (e.g. livestock farms in the countryside) into the river. The partitioning of antibiotics in river water and sediment suggests a lower sorption of TCs to the sediment compared to previous studies, which is believed to be caused by the high Ca2+ and Mg2+ concentrations, ionic strength and pH of the river water in the carbonate area.

Fluorescence and amino acid characteristics of molecular size fractions of DOM in the waters of Lake Biwa

Dissolved organic matter (DOM) in the waters from Lake Biwa, Japan was fractionated using tangential flow ultrafiltration, and subsequently characterized by fluorescence properties and amino acids. While major dissolved organic carbon (DOC), UV absorbance (Abs), humic-like fluorescence (Flu) and total hydrolyzed amino acids (THAA) occurred in the less than 5 kDa molecular size fraction, they were not evenly distributed among various molecular size fractions. Flu/Abs ratios increased, and THAA/DOC ratios decreased with decreasing molecular size. Humic-like fluorescence occurred in all molecular size fractions, but protein-like fluorescence only occurred in the 0.1 μm-GF/F fraction. Subtle differences in amino acid compositions (both individuals and functional groups) were observed between various molecular size fractions, this may indicate the occurrence of DOM degradation from higher to lower molecular weight. The results reported here have significance for further understanding the sources and nature of DOM in aquatic environments.

Removal of cadmium(II) from aqueous solution by corn stalk graft copolymers

Corn stalk was modified using graft copolymerization to produce absorbent (AGCS), which was characterized by elemental analysis, fourier transform infrared, X-ray diffraction, solid-state CP/MAS (13)C NMR spectra, thermogravimetric analysis and differential scanning calorimeter. AGCS, having cyano group (-CN) after grafted successfully, exhibits more high adsorption potential for Cd(II) than unmodified forms. The efficiency of AGCS for removal of cadmium ions was evaluated. Factors affecting Cd(II) adsorption such as pH value and adsorbent dosage were investigated. More than 90% removal was achieved at pH 3.0-7.0 and the adsorption increased from 16.0% to 99.2% with increase of adsorbent dose. In addition, two isotherm models, namely, Langmuir and Freunlich were also analyzed to determine the best fit equation for adsorption of Cd(II) on AGCS.