Advanced Materials Research Vols. 1010-1012

Abstract: Soil profiles from 0 to 80 cm depth were collected at five typical zones (including permanently flooded floodplain (B), 1-year floodplain (O), 5-year floodplain (F), 10-year floodplain (T), and 100-year floodplain (H)) which are divided by different flooding frequencies along the direction penperdicular to the river channel in different floodplain wetlands of Xianghai National Nature Reserve of China. A 14-day incubation experiment was carried out at 25°C in the dark to reveal the effects of different flooding frequencies on nitrogen mineralization rates. Our results showed that nitrogen mineralization rates showed an alternative tend of “increasing and decreasing”in the soil profiles at five sampling zones except the 1-year floodplain and permanent floodplain. The nitrogen mineralization rates were lower in permanently flooded floodplain soils compared to another four floodplain wetlands with different flooding frequencies. Additionally, nitrogen mineralization rates were significantly correlated with electrical conductivity, total soluble salt, pH values and salinity.

Abstract: The article applied 2008-2012 hourly mass concentrations of PM₁₀ , SO₂ and NO₂ and air pollution index (API) data to discuss the temporal variation of urban air quality in Nanchong, a big southwest city in China. The results showed that the annual mean PM_10, SO₂ and NO₂ concentrations during 5 years were 61±1μg.m^-3, 45±4μg.m^-3, 35±5μg.m^-3, respectively. And the annual mean concentrations and API values presented decreasing tendency, which were less than the annual second-level air quality limit except for NO₂ in 2008. In addition, the monthly mean values in spring and winter were higher than those in summer and fall, which the maximum appeared in December, and January, the minimum appeared in July and August.

Abstract: Using statistical methods,the hydrochemical characteristics of underground brine was studied in the littoral plain along the south of Laizhou Bay. The results demonstrate that: the main chemistry types of underground brine is Na-Cl and Na-Mg-Cl,and its hydrochemical characteristics consist well with seawater; the coefficients namely rNa/rCl、k/br、rMg/rCa, indicate the underground brines, with greater concentration and weaker metamorphism, originated from seawater.

Abstract: The impact of purity of raw material on the accuracy of gas standard is studied. The R142b with purity of 99.6% and N₂ with purity of 99.996% was used to prepare R142b in N₂ gas standard based on gravimetric method. Results showed that if the impurity in R142b raw material was not dectected, it would cause 0.20-0.23% deviation relative to the reference value; if the uncertainty for impurity in R142b reach to 100%, the uncertainty in each step of dilution was amplified for almost 66.9%-144%, seriously reducing the reliability of the gas standard. Conversely, the neglect of 4.85×10^-5 mol/mol Ar in dilutent gas N₂ would neither significantly affect the mole fraction nor its uncertainty value. These results clarified the importance of purity analysis on standard gas mixture preparation.

Abstract: This paper mainly focuses on the temporal and spatial variation of nutrients in the Yangtze River Estuary. Observations show that the high level of nitrate concentration appears in the coast waters and gradually decreases toward the continental shelf both in summer and in winter; while the ammonium and phosphate concentrations show the relatively high level in the bottom layer of the water column in summer, since ammonium and phosphate can be regenerated on the sediments and reenter the bottom layer of the water column to make up their contents. In winter, the nutrients are well-distributed in the vertical due to the strong mixing mechanism. The further examination of the nutrient limitation, according to the Redfield theory, shows that the phosphorus limitation dominates in the river mouth and then shift to the nitrogen limitation toward the continental shelf gradually. The variation of the nutrient limitation may be dependent on the relative strength between the Changjiang Diluted Water and the Intrusion Branch of the Kuroshio Current.

Abstract: Zhushan Bay watershed to the northwest of Lake Taihu was selected as the research area. Taking the close connection of water quality and quantity of river-lake system into consideration, we constructed a water environmental coupling model of 1-D river network and 2-D lake to simulate hydrodynamic and water quality of river-lake system. Based on the results of field measured data, the constructed model was calibrated and validated. According to results of calibration, the range of river roughness was 0.02~0.028, the degradation coefficient of COD, NH₃-N and TP degradation coefficient was 0.09~0.11 d^-1, 0.05~0.07 d^-1 and 0.04 d^-1, respectively; the lake bottom roughness was 0.025, the wind stress coefficient was 0.0013, the degradation coefficient of COD, NH₃-N and TP degradation coefficient was 0.06、0.04 and 0.02 d^-1, respectively. The calculated results fit well with the experimental results, indicating that the model has good practicality.

Abstract: Carbon dioxide plays important role in various spheres of the Earth system (lithosphere, soil, hydrosphere, atmosphere and biosphere) for material of storage, transformation, transfer and interaction. In the research, two approached to measure CO₂ flux at soil surface and in profiles was carried out in situ in arid area. The background CO₂ concentration was 323.49 ± 21.36 × 10-6(volume fraction) in the surface of the atmosphere, and there are seasonal and diurnal change in the carbon dioxide concentration. For CO₂ flux between soil and atmosphere, the average CO₂ flux was 230.05 μmol·m-2·h-1 from the four kind soils, and CO₂ flux exhibited seasonal and diurnal variations too. For CO₂ flux from soil (the chestnut soil, sierozem soil, fragmental soil, and gray-cinnamon soil) that was exposed to air, CO₂ flux increased when soil from 0–60 cm depth was exposed but decreased when soil at 61–70 cm depth was exposed. The results show that 1) vegetation characteristics and temperature greatly affect CO₂concentrationat the soil surface; 2) CO₂ may be released from the soil into the atmosphere at 254.6 t·km^-2·yr^-1 if the soil at 0–70 cm depth is exposed to the air because of a change in land use or land cover; 3) the soil may absorbed CO₂ when plants were not growing in northern hemisphere; 4) The differences in the distribution of heat energy on the Earth's surface indicate a mechanism by which soil can regulate the concentration of CO₂ in the atmosphere of temperate-arid regions in northern hemisphere.

Abstract: The latest technical progress in pretreatment and analysis method of inorganic elements of electroplating sludge was briefly reviewed. Some pretreatment methods were summarized, including exposure system digestion, high-pressure tank digestion, microwave digestion and dry ash digestion as well as some analysis methods, such as spectrophotometry, atomic absorption spectrometry, inductively coupled plasma spectrometry and inductively coupled plasma mass spectrometry. Finally, the trend for future technical development in inorganic elements determination of electroplating sludge was prospected.

Abstract: The aim of this work was to evaluate the microemulsification after incomplete digestion as sample preparation procedure for determination of Ca in leisure foods by high resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS). Microemulsions were prepared with digestive liquor and n-butyl alcohol as an auxiliary emulsifier after incomplete digestion treatment. The appropriate fuel flow, 70 L/h, and the optimum burner height, 5 mm, were obtained by single factor experimental design. The results showed that the correlation coefficient was better than 0.999, the characteristic concentration was 0.086 mg/L, the precision (RSD) for 6 replicate measurements of Ca was 1.7% and the average of recoveries was 102.1%. F-test and t-test (95% confidence level) in between the proposed method and the comparative method, using microwave digestion-HR-CS FAAS, had no significant difference. Therefore, the proposed method was accurate and stable with a high practical value. It provided scientific basis for determination of metal elements in food.

Abstract: The soil bacteria diversity in different concentrations of CO₂ was investigated in the simulation test area, by using PCR (Polymerase Chain Reaction) -DGGE (Denaturing Gradient Gel Electrophoresis) and 16Sr-DNA library technology. The results showed that the bacteria diversity coefficient (P) got down to 0.8710, 0.8710 and 0.7742 from 0.9032 (from control area) when the concentration of CO₂ in soil reached 20000ppm, 40000ppm, 60000ppm respectively. With the increasing concentration of CO₂ in soil, the abundance of the original low-density bacteria such as Asticcacaulis excentricus, etc. increased, while the abundance of unclassified_Rhizobiales reduced significantly. Dominant bacteria such as Brucella melitensis etc. had the higher homology. It can be revealed that high concentration of CO₂ had a significant impact on the soil bacteria community diversity, while a weak influence on main bacterial species. Azotobacter was sensitive to the increasing of the CO₂ concentration. Great reducing of their abundance had an adverse effect on nitrogen-fixing capability of soil.