中国北方表沙无机碳储量及次生碳酸盐固碳潜力研究

This paper selected the Taklamakan Desert and the Badain Jaran Desert as the research areas, tested the carbonate content of surface-sand samples of dunes using Eijkelkamp carbonate goniophotometer, and analyzed the spatial-distribution characteristics of carbonate and estimated the carbonate-stock and secondary carbonate-stock in 1m depth of surface sand in the Taklamakan Desert and the Badain Jaran Desert. In addition, the paper test XRD, SEM, TDA, stable carbon isotope and radioactive strontium isotope of lacustrine deposits in the Taklamakan Desert and carbonates, such as kunkar, root canal, lacustrine deposits, sinter and calcrete, in the Badain Jaran Desert. Resting on the achievements by our predecessors, it analyzed the mineral-composition differences of the carbonates, calculated the contents of secondary carbonate and, furthermore, evaluated their potential of sequestration of CO2 in the atmosphere. The overall goal of this study was to increase our understanding of soil carbonate in the context of carbon sequestration in the arid region in China. That is, to advance our understanding about whether or not secondary carbonate in desert is a sink for atmospheric CO2. The following viewpoints were obtained: 1 Carbonate contents of surface-sand samples decend from the south to the north of the Taklamakan Desert. The minimum lies in the south and the maxmum in the mid. Carbonate content of surface-sand of megadunes in the Badain Jaran Desert has low value generally in the dune-crest and the base of slope, and large value in the mid. The average of Carbonate contents of all sorts of collected samples in the same area of the Taklamakan Desert has small diffetences. The average is about 9%. 2 Using carbonate contents as key parameters, calculate the carbon-stock of carbonates in 1m depth of surface sand in the Taklamakan Desert and the Badain Jaran Deser.They are 1.13Pg and 0.19 Pg respectively. There are 0.53Pg and 0.088Pg carbon-stock of secondary-carbonates in 1m depth of surface sand in the Taklamakan Desert and the Badain Jaran Desert. 3 Through testing data from XRD （X-ray diffraction）and TAD ( Thermal Analysis Data), the most significant conclusion derived from is that the main mineral ingredient is calcite in different carbonate substances in arid regions, From the SEM(Scanning electron microscopy ) images, can obtains the information about the micro environment of different carbonate forms in which they can grow. 4 Selected gas by termal cracking and traditional phosphoric acid method, their δ13C show that δ13C is a good parameter to indicate the micro environment in which different secondary carbonate forms. From the δ13C of the same type samples, if the redeposit degree is hard, theδ13C is light, the redeposit degree is weak, the δ13C is heave. and the δ13C of the different type samples, δ13C is mainly controlled by the micro environment in which secondary formed. if the procedure is characterized by redeposit and dissolve of marine facies carbonate, δ13C is heavy, it is characterized by CO2 which produced by plant respiration,δ13C is light. 5 From the δ13C of lacustrine deposit in the different grain size, there exsit certain differences in their micro environment and secondary degree among different grain size in the same grade. 6 The secondary carbonate content of lacustrine deposits in Taklimakan Desert is 47.26%. And those of root canal, sinter, calcrete, kunkar, lacustrine deposit and surface sand in Badain Jaran Desert are 91.74%, 78.46%, 76.26%, 87.87%, 85.37%and 46.49%, respectively. Of different grain size samples, the secondary carbonate contents of coarse fraction (20-63μm), sub-coarse fraction (5-20μm) and fine fraction (<5μm) are 80.10%, 47.2%and 50.07%, respectively. 7 There is no obvious relevance betweenδ13C of secondary carbonate and the content of secondary carbonate,theδ13C of secondary carbonate mainly reflects the parameters of secondary process, the content of secondary carbonate reflects difference of secondary degree.. 8 Silicates potentially supply 3.4 pencent calcium source during forming process of lacustrine deposits in Taklimakan Desert. If calcium source is mainly supplied by goundwater, it can be calculated that about 5.18 %, 6.13%, 5.68%, 5.64 % and 6.82% silicates supply calcium source respectively for root canal, kunkar, lacustrine deposit, calcrete and sinter, during the forming process of different kinds of carbonates in Badain Jaran Desert.

Root zone microbial populations, urease activities, and purification efficiency for a constructed wetland

In order to investigate the effects of microorganisms and their urease activities in macrophytic root zones on pollutant removal, four small-scale plots (SSPs) of vertical/reverse-vertical flow wetlands were set up to determine: a) the relationship between the abundance of microorganisms in the root zones and water purification efficiency; and b) the relationship between urease activities in the root zones and pollutant removal in a constructed wetland system. Total numbers of the microbial population (bacteria, fungi, and actinomyces) along with urease activities in the macrophytic root zones were determined. In addition, the relationships between microbial populations and urease activities as well as the wastewater purification efficiencies of total phosphorus (TP), total Kjeldahl nitrogen (TKN), biochemical oxygen demand in 5 days (BOD5), and chemical oxygen demand (COD) were also analyzed. The results showed that there was a highly significant positive correlation (r = 0.9772, P < 0.01) between the number of bacteria in the root zones and BOD5 removal efficiency and a significant negative correlation (r = -0.9092, P < 0.05) between the number of fungi and the removal efficiency of TKN. Meanwhile, there was a significant positive correlation (r = 0.8830, P < 0.05) between urease activities in the root zones and the removal efficiency of TKN. Thus, during wastewater treatment in a constructed wetland system, microorganism and urease activities in the root zones were very important factors.