Global methane and nitrous oxide emissions from terrestrial ecosystems due to multiple environmental changes

Greenhouse gas(GHG)-induced climate change is among the most pressing sustainability challenges facing humanity today,posing serious risks for ecosystem health.Methane(CH_(4))and nitrous oxide(N_(2)O)are the two most important GHGs after carbon dioxide(CO_(2)),but their regional and global budgets are not well known.In this study,we applied a process-based coupled biogeochemical model to concurrently estimate the magnitude and spatial and temporal patterns of CH_(4)and N_(2)O fluxes as driven by multiple environmental changes,including climate variability,rising atmospheric CO_(2),increasing nitrogen deposition,tropospheric ozone pollution,land use change,and nitrogen fertilizer use.The estimated CH_(4)and N_(2)O emissions from global land ecosystems during 1981-2010 were 144.39±12.90 Tg C/yr(mean 62 SE;1 Tg=1012 g)and 12.52±0.74 Tg N/yr,respectively.Our simulations indicated a significant(P,0.01)annually increasing trend for CH_(4)(0.43±0.06 Tg C/yr)and N_(2)O(0.14±0.02 Tg N/yr)in the study period.CH_(4)and N_(2)O emissions increased significantly in most climatic zones and continents,especially in the tropical regions and Asia.The most rapid increase in CH_(4)emission was found in natural wetlands and rice fields due to increased rice cultivation area and climate warming.N_(2)O emission increased substantially in all the biome types and the largest increase occurred in upland crops due to increasing air temperature and nitrogen fertilizer use.Clearly,the three major GHGs(CH_(4),N_(2)O,and CO_(2))should be simultaneously considered when evaluating if a policy is effective to mitigate climate change.

Enhancing the power conversion efficiency of PCDTBT:PC_(71)BM polymer solar cells using a mixture of solvents

Organic polymer solar materials are shown to exhibit better solubility in mixed solvents than in pure ones,which affects the performance of their solar cells.In this article,poly[N-9-hepta-decanyl-2,7-carbazole-alt-5,5-(4.7-di-2-thienyI-2,l,3-benzothiadiazole)(PCDTBT0)and[6,6]-phenyl-C71-butyric acid methyl ester(PC_(71)BM)are used as active layer materials in solar cells.To optimize the performance of these active materials,the ratio of chloroform(CF)to chlorobenzene used as solvents to dissolve PCDTBT,and PC_(71)BM is varied,which is shown to affect power conversion efficiency(PCE).The solar cell that shows the best performance with a PCE as high as 6.82%is produced using a volume ratio of CF to chlorobenzene of1:1.