Carbonic anhydrase (CA) catalyzing CO 2 hydration has an important application in carbon capture, and its immobilization is very significant. Here, CA was covalently linked by glutaraldehyde (GA) to the surface of poly(vinylidene fluoride) (PVDF) and polyethylene (PE) membranes, which were previously modified via a simple codeposition of polyethyleneimine (PEI) and dopamine (DA). The effects of the modification conditions were investigated, and the membranes were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. The immobilization process was optimized, and the catalytic properties of immobilized CA were studied. The results show that the optimal mass ratio of PEI and DA was 1:1 and the deposition time was 10-12 h, at which the surface amino group density could reach 1.278 × 10 −7 and 1.397 × 10 −7 mol/cm 2 for PVDF and PE, respectively. For enzyme immobilization, the optimal CA and GA concentrations were 0.2 mg/mL and 0.1 wt %, and a maximum activity recovery of about 53% and 76% could be achieved for PVDF-attached CA and PE-attached CA, respectively. Their K m values were 10.62 mM and 8.6 mM, and the corresponding K cat /K m values were 132.2 M −1 s −1 and 312.9 M −1 s −1 . After immobilization, the storage stability and reusability of CA were much improved.

No abstract

Sandy range land refers to a major component of grassland area types in the semi-arid area of northern China. Monitoring of vegetation and land surface temperature (LST) using remote sensing technology can help determine the degree of desertification in a regional and/or sub regional scale, as in the Horqin Sandy Land selected in this study. Correlation analysis was performed to examine the relationship between the fractional vegetation coverage (FVC) and the LST within one growing season (from May to August 2017), at different spatial scales. The results showed that the FVC increased from 0.12 in May to 0.29 in August, and the LST increased first and then declined. The highest LST was 41.68 °C in July, while the lowest was 28.62 °C in August. At the grid scale, the LST increased first and then declined with the increase of the FVC on 25 May, 10 June, and 29 August; the FVC ranged from 0.29–0.38, 0.27–0.32, and 0.29–0.38 with the preference of the ‘turning point’, respectively. A negative correlation was identified between the FVC and the LST and without any ‘turning point’ in the fitting curve on 28 July. The correlation between FVC and LST complied with the grid scale at the sample area scale. The coupling analysis of landscape pattern expressed by FVC and LST showed that, the landscape evenness, Euclidean nearest neighbor distance, and landscape splitting degree all showed strong coupling correlation in any study period (P). The landscape aggregation of FVC and LST showed a good coupling at the relatively high and low air temperature conditions of P1 and P3. Landscape contagion showed a good coupling between FVC and LST at relatively moderate air temperature condition of P1 and P4. Air temperature conditions and characteristics of vegetation coverage should be considered for a more targeted analysis when analyzing the relationship between FVC and LST and attention should be paid to the timing and type of study area in practical application.

No abstract

The oasis-desert transition zone, the boundary between the desert and oasis, has special significance in maintaining oasis stability and indicating ecosystem health. The width of the boundary is one of the critical indicators to determine the sampling design and restrict findings scaling in the study of the desert oasis transition zone. Buffer analyze and focal analyze were conducted to determine the width among oasis-desert transition zone and oasis artificial sand fixation zone in Hexi corridor China. Focal analyses indicate that TCImax and TCImin can constrain NDVI of trend variation, and the effect increases with the analysis scale. On the same spatial scale, NDVI and TCI have opposite trends and have intersections. The intersection of the sandy desert transition zone is between 30–90 m, and the oasis artificial sand-fixaion zone is between 90–150 m. The width of the sandy desert transition zone is between 220–300 m, and the width increases with the increase of analysis scale. The oasis artificial sand-fixation zone is between 420 and 540 m, which decreases with the increase of the analysis scale. NDVI shows a trend of decreasing from the oasis boundary to the desert, the trend of TCI is different from that of NDVI, showing an increase from the edge of oasis to the interior of desert. The differences in the spatial distribution of NDVI and TCI can be clearly expressed, and different types of transition zones and analysis scales have their own characteristics.