No abstract

No abstract

Wetlands play an important role in regulating the atmospheric carbon dioxide (CO ) concentrations and thus affecting the climate. However, there is still lack of quantitative evaluation of such a role across different wetland types, especially at the global scale. Here, we conducted a meta-analysis to compare ecosystem CO fluxes among various types of wetlands using a global database compiled from the literature. This database consists of 143 site-years of eddy covariance data from 22 inland wetland and 21 coastal wetland sites across the globe. Coastal wetlands had higher annual gross primary productivity (GPP), ecosystem respiration (R ), and net ecosystem productivity (NEP) than inland wetlands. On a per unit area basis, coastal wetlands provided large CO sinks, while inland wetlands provided small CO sinks or were nearly CO neutral. The annual CO sink strength was 93.15 and 208.37 g C m for inland and coastal wetlands, respectively. Annual CO fluxes were mainly regulated by mean annual temperature (MAT) and mean annual precipitation (MAP). For coastal and inland wetlands combined, MAT and MAP explained 71%, 54%, and 57% of the variations in GPP, R , and NEP, respectively. The CO fluxes of wetlands were also related to leaf area index (LAI). The CO fluxes also varied with water table depth (WTD), although the effects of WTD were not statistically significant. NEP was jointly determined by GPP and R for both inland and coastal wetlands. However, the NEP/R and NEP/GPP ratios exhibited little variability for inland wetlands and decreased for coastal wetlands with increasing latitude. The contrasting of CO fluxes between inland and coastal wetlands globally can improve our understanding of the roles of wetlands in the global C cycle. Our results also have implications for informing wetland management and climate change policymaking, for example, the efforts being made by international organizations and enterprises to restore coastal wetlands for enhancing blue carbon sinks.

A new route to synthesize V-doped and V−N codoped titania nanocatalysts using a novel two-phase hydrothermal method applied in hazardous PCP−Na decomposition was reported. The physicochemical properties were characterized, indicating that the crystallite surface area increased after both first hydrothermal (FH) V impregnation and second hydrothermal (SH) N implantation, whereas mesoporous framework shrinkage and enlargement resulted from FH and SH, respectively. ICP and EPR demonstrated that SH did not alter V content, but rather it induced paramagnetic V4+ increase. The V species was enhanced from the inner to the catalyst surface with V5+ as the dominant mode and the N dopant existed with substitutional nitrogen as the main structure. The optical red shift by low vanadium implantation was ascribed to the V2p state, mainly from V4+ species in the matrix. After SH incorporation, the substitutional N1s state, interstitial N−O state, and concomitant NOx were responsible for the strong visible absorption of V−N−TiO2. The photodegradation rates of PCP−Na by the remodified catalysts after SH were much larger than that of the mono-V-TiO2 precursors fabricated in FH. SHNV02, SHNV05, and SHNV10 exhibited 2.4, 1.6, and 3.1 times promotion toward PCP−Na decomposition, respectively. Moreover, other variations and the synergetic effects after two-phase treatments were adequately discussed and proven to be useful in facilitating photocatalytic promotion. This work provided a strategy for obtaining further enhancement of the synthesized catalyst by second-step modification to achieve the deep removal effect of contaminants.

No abstract