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Accumulating heavy metal contamination in soils caused by industrial waste, fertilizer, and wastewater irrigation is a matter of grave concern for the environment and food safety. In recent years, remediation agents with the characteristics of economy, high efficiency, and simple operation have become a popular choice for remediation of heavy metal contaminated soil. By far, there are relatively few studies evaluating the effects on remediation agents for their both heavy metal passivation and soil fertility promotion. This study investigated the effects of a remediation agent on Cd passivation, soil pH, and heavy metal uptake by rice crops. Eight treatments were used to evaluate the effect of Cd immobilization in soil. Changes in soil pH and soil Cd fractions were monitored during incubation for 30 days. The field study was conducted during the whole growth stages of rice crops, samples of rice plants and soil at the tillering, booting, and harvesting stages were collected and tested. Cd fractions were extracted from soil at different stages to investigate the effects of various treatments on Cd uptake and bioaccumulation in rice plants. The results show that composite mineral remediation agents composed of mineral fertilizer and synthetic zeolite could effectively improve the pH of soil in incubation experiments and field experiments. Composite mineral remediation agents were effective in stabilizing Cd and increasing rice yield. Mineral fertilizer and Synthetic zeolite played an important role in the tillering stage and harvesting stage of rice growth in field, respectively. Group A4 (mineral fertilizer: synthetic zeolite at mass ration of 10:6) had the best results. Compared with control experiment (CK), HOAc extractable Cd of A4 group decreased by 6%, oxidizable Cd of A4 group increased by 2%, and the residue Cd of A4 group increased by 4%. [ABSTRACT FROM AUTHOR]

The 87Sr/86Sr minimum of the Capitanian seawater is one of the most significant features in the Phanerozoic seawater 87Sr/86Sr history. In order to assess possible contribution of the Emeishan large igneous provinces (LIPs) to strontium isotope evolution of the Capitanian seawater, 87Sr/86Sr ratios were measured from the Capitanian limestones which are locally interlayered with the Emeishan basalts. The limestones underlying the Emeishan basalts have high 87Sr/86Sr ratios (0.7070–0.7074). However, extremely low 87Sr/86Sr ratios (0.7068–0.7070) were identified in the late Capitanian Jinogondolella prexuanhanensis–J. xuanhanensis zones, which correspond to the eruption time of the Emeishan LIP. The temporal coincidence of these two phenomena supports the idea of a potential linkage between Capitanian 87Sr/86Sr minimum and eruption of this igneous province. The strong submarine hydrothermal activity and erosion of the Emeishan LIP could have released large amounts of non-radiogenic Sr to the oceans and play an important role in strontium isotope evolution of the seawater. [ABSTRACT FROM AUTHOR]

In this study, the loaded diatomite was prepared with Changbai Mountain diatomite as the carrier according to different Fe/Al molar ratios. The structure and adsorption of the above materials were characterized by XRD, SEM, and ICP-OES. The effects of Fe/Al molar ratio, adsorption time, initial concentration of V(V), and the initial pH value of the solution on the adsorption performance of loaded diatomite were explored. The diatomite loaded with Fe/Al compounds could significantly improve the removal efficiency of V(V), and the removal efficiency of loaded diatomite prepared according to a Fe/Al molar ratio of 1:3 was better. Reaction equilibrium time is 24 h and the pseudo second-order kinetic equation can better describe the adsorption kinetic behavior of V(V) on loaded diatomite. When the initial concentration of V(V) increased from 15.85 mg/L to 122.5 mg/L, the unit adsorption capacity and removal rate of V(V) by loaded diatomite increased continuously. The adsorption behavior of V(V) on loaded diatomaceous earth belongs to the chemical adsorption via the multi-molecular layer, which is consistent with the Freundlich isotherm adsorption model. A weak acid environment is beneficial to the adsorption behavior of V(V) on loaded diatomaceous earth and the strong alkaline environment should be avoided. [ABSTRACT FROM AUTHOR]

The nanoakaganeite (β-FeOOH) was synthesized by the hydrothermal method in the study. The structural characterization and adsorption investigation of the produced materials were performed with powder X-ray diffractometer (XRD), scanning electron microscope (SEM), and inductively coupled plasma optical emission spectrometer (ICP-OES). Moreover, the influences of hydrothermal time, Fe3+ concentration, and hydrothermal temperature on the product structure and chromium adsorption were investigated. In addition, the influence of initial Cr(VI) concentration on chromium adsorption was investigated. The investigation results confirmed the optimal synthesis conditions of β-FeOOH as follows: 72 h hydrothermal reaction, 0.20 M Fe3+, and hydrothermal temperature at 70 °C. The as-synthesized β-FeOOH was spindle-shaped akaganeite. When the initial Cr(VI) concentration increased from 9.91 mg/L to 99.47 mg/L, the adsorption capacity increased and Cr(VI) removal rate decreased. Cr(VI) adsorption on β-FeOOH was a single-molecule layer chemical adsorption, conforming to the Langmuir adsorption model. The maximum saturation adsorption was 16.35 mg/g. [ABSTRACT FROM AUTHOR]

The Maoniuping rare earth elements deposit is the second largest rare earth elements deposit in China, and the third largest in the world. A sediment core was collected from the river floodplain downstream from the Maoniuping rare earth elements mining area (Sichuan Province, China) to reconstruct the cadmium contamination history and trace its contamination source. Based on lead-210 (210Pb) dating by gamma ray spectrometry and elements determination with inductively coupled plasma mass spectrometry of the sediment core, it was found that the cadmium accumulation rate of the flood plain increased from 0.16 to 2.22 µg cm−2yr−1over the past 100 years. Combining aspects of time, space, and element composition information, it is proved that the exploitation of Maoniuping rare earth elements deposit was the main reason for the increase. Moreover, to evaluate the mobility and availability of cadmium in the sediment core, the modified European Communities Bureau of Reference sequential extraction procedure in combination with inductively coupled plasma mass spectrometry was applied. Risk assessment code was used to further assess the environmental risk of cadmium in the sediment. It was found that the environmental risk from cadmium was high in the surface of the sediments. The results from gamma ray spectrometric and mass spectrometric methods may provide important information for the control and remedy of cadmium-related pollution areas. [ABSTRACT FROM PUBLISHER]

Metal contamination in sediment of the Mianyuan River (one of the major upper reaches of the Yangtze River) in Longmenshan Region (China) was investigated in 2012. Means of metal concentrations in sediment (<74μm) were Cr: 59.93 ± 19.8% mg/kg; As: 7.21 ± 50.2% mg/kg; Se: 0.45 ± 66.3% mg/kg; Pb: 19.89 ± 29.3% mg/kg; Zn: 78.98 ± 31.9% mg/kg; Cd: 0.69 ± 28.3% mg/kg; Ba: 0.71 ± 34.0% g/kg; Mn: 0.55 ± 62.2% g/kg. This study suggested: (1) concentrations of Cd, As, Cr, and Pb in Mianyuan River sediment were lower than those of the middle and lower reaches of the Yangtze River; (2) the increase of metals during the period from 2006 to 2009 was probably related to the destruction of tailings piles by the Wen Chun earthquake in 2008; (3) organic materials decided the distribution of Cd, Se, As, Ba, and Mn in the upstream sediment, while the iron and manganese minerals controlled the distribution of Ba, Cr, and Zn in the downstream sediment; (4) sources of Cd, Se, and As were geogenic, while sources of Cr, Zn, Ba, and Mn were anthropogenic; (5) the source of Pb in the upstream sediment was probably automobile exhaust, but that of Pb in the downstream sediment was geogenic. [ABSTRACT FROM AUTHOR]