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Jatropha curcas biodiesel was taken as the research object, studied the single and compound effects of oxidation degree and temperature on kinematic viscosity of biodiesel, and established a mathematical model. The results indicate that the kinematic viscosity of biodiesel decreases gradually with the increase of temperature, and the mathematical model affected by the single factor of temperature is η = e(A + Bt + Ct2) . The kinematic viscosity of biodiesel increases with the increase of oxidation time. The regression equation between kinematic viscosity and conductivity is established as follows: η = A + Bμ. It is found that the influence of temperature on the kinematic viscosity of biodiesel is much greater than that of oxidation, and the higher the temperature, the lower the influence of oxidation on the kinematic viscosity of biodiesel. Through the analysis of the influence weight of two factors and the change rate of kinematic viscosity, it is found that with the increase of temperature, the effect of conductivity on the change rate of kinematic viscosity of biodiesel is positive, but the influence decreases gradually. The relationship between kinematic viscosity, temperature and oxidation

Dissolved organic matter (DOM) in soil is a key factor affecting the bioavailability of heavy metals, but very few studies have focused on the role of DOM in the use of soil amendments to mitigate heavy metal accumulation in crops. Here, eleven materials were added to cadmium (Cd)-contaminated paddy soil in greenhouse pot trials; rice was grown and harvested, the chemodiversity of post-harvest soil DOM was characterized using Fourier-Transform Ion Cyclotron Resonance Mass Spectrometry, and the specific associations between soil DOM traits and water-extractable soil Cd concentration were identified at the molecular level. The results showed that the endogenous release caused by altering soil pH had a greater effect on soil DOM concentration than did the exogenous chemical input due to the application of organic amendments, which in turn contributed to the chemodiversity of DOM. After one season of rice cultivation, soil DOM molecules were mainly dominated by relatively low molecular weight heteroatom-free lignins. C/N, C/H ratios of organic materials influenced DOM molecular fingerprint patterns, and soil pH and redox potential were the main driving forces affecting the chemodiversity of DOM. Furthermore, the low molecular weight, high saturation, low aromaticity, and heteroatom-free DOM molecules are more likely to dissolve Cd from the soil solid phase, thus increasing the potential risk of Cd to the environment. The results provide critical information about amendments-induced changes in DOM chemodiversity and will inform the selection of appropriate soil amendments.

Recently, enterprises and industries associated with intense pollution have been relocated in China, leaving behind abandoned polluted sites. Consequently, stabilization has attracted unprecedented attention and rapid development. However, too much focus has been placed on practicality and short-term effectiveness, whereas long-term effectiveness and sustainability concerns have been overlooked. The present study reports the findings of a national survey administered to stakeholders involved in soil stabilization projects over a decade to determine the pollution characteristics of industrial sites and current utilization status of stabilization technologies in China. One-hundred and fifty soil stabilization projects surveyed revealed that among 29% of chemical industry remained sites, 96.7% of the sites were heavily polluted with heavy metals and metalloids, mainly in the forms of lead, arsenic, and chromium. Our analyses of soil reuse methods revealed that landfilling was the primary strategy of soil disposal following stabilization and remediation. In addition, the reuse of treated soils is preferred to landfill waste treatment. Therefore, from the perspective of economy and reducing landfill loads, environmental management measures should be adopted based on the development objectives of different regions to avoid the failure of stabilization treatments and reapplication and over-repair problems, with the aim of establishing an evaluation method of "site-specific, analysis-specific" evaluation method.

Using diffusive gradients in thin films (DGT) is a recently developed alternative method of rapidly evaluating the bioavailability of metals in soil. However, the method has found only limited application in systematic assessment of the bioavailability of cadmium (Cd) in red limestone paddy soils treated with different soil amendments. Of the four methods compared for estimating Cd content of rice grains from plants grown in such soils of central China treated with eleven different soil amendments in pot culture, Cd content of DGT-labile soil was significantly correlated to Cd concentrations in brown rice (R = 0.447, p 0.01). The other three methods involved CaCl

Metal pollution in urban soils due to smelting and electroplating has become a severe problem in China. In this study, the concentration, chemical fraction, and leaching behavior of typical metals (Cu, Zn, Cd, and Pb) in soil samples from ten metallurgical sites were studied. The results show that some of the soils were polluted with Cu and most were heavily polluted with multiple metals, especially Zn, Cd, and Pb. The average concentration of Cu, Zn, Cd, and Pb was 498, 4145, 89, and 5091 mg/kg, respectively. Chemical fractionation revealed that Cu, Zn, Cd, and Pb were mainly present in the acid-soluble fraction in polluted soils, but predominated in the residual fraction in unpolluted soils, demonstrating that allogenic metals in the soils were mostly present in the more labile fractions. Toxicity characteristic leaching procedure results were in agreement with the chemical fractionation study, indicating that the higher the total metal content, the higher the leachability, mobility, bioavailability, and potential toxicity to the environment, especially groundwater. Use of chemical fractionation results instead of total metal concentrations would provide better insight into the distribution and binding forms of metals for better assessment of their mobility and bioavailability. The study would provide much more important information for developing better remediation strategies for contaminated sites.

The soil moisture regime can affect the release of heavy metals in soil. In the previous studies, slightly polluted soils or artificially contaminated soil samples were considered to investigate the effect of soil moisture. We used highly smelter-contaminated and aged soils to study the release of typical heavy metals (Cu, Zn, Cd and Pb) induced by water incubation in batch experiments with characterization via speciation and X-ray diffraction analyses (XRD). The results show that the leachable concentrations of the heavy metals increased slightly in the first 30 days, decreased drastically between 30 and 90 days, and immobilized relatively constant thereafter. The fluctuation was ascribed to the changes of soil Eh and pH, the reductive dissolution of crystalline iron oxides, the formation of new amorphous iron oxides, the absorption of dissolved organic matter and the precipitation of metal sulfide. Speciation analysis indicated that a proportion of the soil heavy metals was transformed from an exchangeable fraction to a less labile fraction after water incubation. And the presence of a lead iron oxide phase and the peak increasing of zinc sulfide were observed via XRD analyses. Finally, water incubation restrained the release of heavy metals after 180 days of incubation, and reduced the leachability of Cu, Zn, Cd and Pb by as much as 1.61%–7.21% for soil A and 0.43%–3.36% for soil B, respectively. The study findings have implications for the formulation of risk control and management strategies for heavy metals in smelter-contaminated soils.

Due to the long time in vehicular cabins, people have high exposure to the airborne volatile organic compounds (VOCS), which will lead to negative effects on human health. In order to analyze the influencing factors of in-car VOCS pollution concentrations, 38 taxis were investigated on the static and closed conditions. The interior air of taxis was collected through activated Tenax adsorption tubes, and the air samples were analyzed with thermally desorbed gas chromatograph. The average concentrations of in-car benzene, toluene, ethylbenzene, xylenes, styrene, butyl acetate, undecane, and total VOCS (TVOC) were 82.7, 212.3, 74.7, 182.3, 24.7, 33.5, 61.3, and 1,441.7 μg/m(3), respectively. Furthermore, the VOCS and TVOC concentrations increase with the rise of in-car temperature and relative humidity, and decrease with the increase of car age and total mileage. In addition, the VOCS and TVOC concentrations are higher in vehicles with small cabins than in ones with big cabins, and change with different sampling sites and various vehicular grades. Finally, according to the multiple linear regression analysis and hierarchical cluster analysis, car age is the most important factor influencing airborne VOCS and TVOC pollution concentrations in vehicular cabins, followed by interior temperature and total mileage.

Interior air environment and health problems of vehicles have attracted increasing attention, and benzene homologues (BHs) including benzene, toluene, ethylbenzene, xylenes, and styrene are primary hazardous gases in vehicular cabins. The BHs impact on the health of passengers and drivers in 38 taxis is assessed, and health risk equations of in-car BHs to different drivers and passengers are induced. The health risk of in-car BHs for male drivers is the highest among all different receptors and is 1.04, 6.67, and 6.94 times more than ones for female drivers, male passengers, and female passengers, respectively. In-car BHs could not lead to the non-cancer health risk to all passengers and drivers as for the maximal value of non-cancer indices is 0.41 and is less than the unacceptable value (1.00) of non-cancer health risk from USEPA. However, in-car BHs lead to cancer health risk to drivers as for the average value of cancer indices is 1.21E-04 which is 1.21 times more than the unacceptable value (1.00E-04) of cancer health risk from USEPA. Finally, for in-car airborne benzene concentration (X, μg/m(3)) to male drivers, female drivers, male passengers, and female passengers, the cancer health risk equations are Y = 1.48E-06X, Y = 1.42E-06X, Y = 2.22E-07X, and Y = 2.13E-07X, respectively, and the non-cancer health risk equations are Y = 1.70E-03X, Y = 1.63E-03X, Y = 2.55E-04X, and Y = 2.45E-04X, respectively.