To study the temporal and spatial distribution and its influence factors of diatoms in the middle and lower reaches of Hanjiang River, diatom in water and sediment were sampled from 5 monitoring sites in Spring and Fall, 2014. Based on 18S rRNA Illumina Miseq high-throughput sequencing technology, 160 species belonging to 111 genuses, 49 families, 28 orders and 3 classes were identified, of which sediment diatom genuses accounted for 98.6%. The species abundance was higher than that of the previous studies, suggesting the significant advantage of high-throughput sequencing technology in diatom identification. The community composition and dominant species in water and sediment were remarkably different, i.e., Pinnularia, Cyclotella and Nitzschia were the dominant species in water, while the dominant species in sediment were Pinnularia, Nitzschia and Navicula. Meanwhile, there exists obvious difference in temporal and spatial distribution of diatom community, due to the fact that Shannon diversity index displayed apparent spatial heterogeneity and diatom species in sediment were higher than that in water; from the view of season changes, the Shannon diversity index in fall were higher than that in spring. Furthermore, total nitorgen, ammonia nitrogen, nitrate and total phosphorus displayed great impact on diatom community composition. As results, controlling nitrogen and phosphorus concentration in the middle and lower reaches of Hanjiang River will be of great importance to avoid diatom blooms.

The authors use CHINAGEM, a computable general equilibrium model to investigate the economic effect and pollution reduction impacts of improved auto fuel economy standard in China. The policy change is modelled as shocks to production tax rate of two industries — petrol refine and motor vehicle parts. The results show that the shocks lead to higher labor cost, slightly decreased GDP and improved terms of trade. The majority of industries, such as motor vehicle manufacturing, will undergo downsizing because of new standards and substitution of imported motor vehicles for domestic ones. However, with improved emission standard and slowdown of vehicle production growth, air pollution problem will be alleviated. Based on the model prediction, the annual emission reductions of carbon monoxide, hydrocarbons, nitrogen oxides and total particulate matter amount to 39.52, 37.51, 11.63 and 1.66 million tons respectively, which are 32, 36, 63, and 87 percentage reduction from the respective business-as-usual levels.