Calcium(Ca),phosphorus(P),and chitin are the main components of the exoskeleton of krill.Defluoridation of a solution of sodium fluoride(NaF) using calcium phosphate(Ca3(PO4)2) and chitin as defluoridation agents was studied.Orthogonal experiments were designed to find the optimum reaction conditions for defluoridation,to obtain the maximum defluoridation efficiency and fluoride removal capacity of calcium phosphate and chitin.At the same time,a comparison of the capacity of the two defluoridation agents was made.The results suggest that calcium phosphate has a far greater capability than chitin for the removal of fluoride(F) from water under similar reaction conditions.It is also suggested that Antarctic krill is likely to adsorb fluoride via compounds such as calcium phosphate,hydroxyapatite,and other compounds of Ca and P with the general form(Ca,X) x(PO4,HPO4,Y) y(OH,Z) z,in addition to chitin.
Three-year summertime surface atmospheric N2O concentrations were observed for the first time on the Fildes Peninsula, maritime Antarctica, and the relationships among the N2O concentration, total atmospheric O3 amount, and sunspot number were analyzed. Solar activity had an important effect on surface N2O concentration and total O3 amount, and increases of sunspot number were followed by decreases in the N2O concentration and total O3 amount. A corresponding relationship exists between the N2O concentration and total atmospheric O3, and ozone destruction was preceded by N2O reduction.We propose that the extended solar activity in the Antarctic summer reduces the stratospheric N2O by converting it into NOx, increases the diffusion of N2O from the troposphere to the stratosphere, decreases the surface atmospheric N2O, and depletes O3 via the chemical reaction between O3 and NOx. Our observation results are consistent with the theory of solar activity regarding the formation of the Antarctic O3 hole.
Methane flux from the ornithogenic soils was preliminarily measured by closed chamber method on Xi-sha atoll, South China Sea during March 10 to April 11, 2003 for the first time. The CH4 flux ranged from -226.7 μg/（m2·h） to 226.3 μg/（m2·h） at the observation sites on Dong Island. High atmospheric CH4 consumption was observed from the ornithogenic soils on sunny days. CH4 uptake rates showed the highest value after the midday and they had a strong positive correlation with soil temperatures. Under the same weather conditions, the CH4 fluxes were also observed from the intact and disturbed soils on Yongxing Island. Results showed that the intact soils with natural vegetation also showed high atmospheric CH4 consumption and the average flux was -141.8 μg/（m2·h）. However, disturbed soils via anthropogenic reclamation showed CH4 emissions and the average flux was 441.7 μg/（m2·h）. Therefore land use changes may have an important effect on the CH4 fluxes from the tropical ornithogenic soils. In addition, different observation sites show a high spatial variation in CH4 fluxes. The wetland in salt marsh showed the CH4 emission on Dong Island, and the dry soil sites all showed high atmospheric CH4 consumption, suggesting that CH4 fluxes were predominantly controlled by soil water regime. The effects of soil chemical properties on CH4 fluxes were also analyzed and discussed in this paper.
