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Soil polycyclic aromatic hydrocarbon (PAH) pollution is a major concern due to its negative impact on soil quality around the world. In China, accurate data on soil PAHs and information on the relationship with anthropogenic activities are limited. In this study, about 30,800 samples from 1833 soil sample sites were reviewed from 306 published reports to build a soil PAHs database. Based on the data obtained, the results demonstrated that 24.11% of surface soils in China are heavily contaminated. Meanwhile, the concentration of soil PAHs varied, in the order of independent mining and industrial areas (IMIA) > urban areas > suburban areas > rural areas, and the spatial distribution in China demonstrated a descending trend from north to south. Moreover, the characteristic ratio and PCA-MLR (principal component analysis-multiple linear regression) analysis demonstrated that coal combustion and vehicular exhaust emissions were the main sources of soil PAH pollution in China. On the other hand, provincial total Σ16PAHs in surface soil were significantly correlated with the per square kilometer GDP (gross domestic product) of industrial land, the per capita GDP, as well as the production and consumption of energy. These results indicate that anthropogenic factors have greatly affected the levels of soil PAHs in China. This study improves our understanding on the status and sources of soil PAH contamination in China, thereby facilitating the implementation of strategies of prevention, control, and remediation of soils.

Since the year 2000, China has implemented large-scale land consolidation, which was used to reduce land fragmentation, enhance grain yield capability, facilitate land tenure transfer, and promote agricultural operational scale. However, the impacts of land consolidation on agricultural technical efficiency of producers in practice is not yet clear. A field survey was executed at two points of time during July 2010 and July 2016. A total of 900 producers were chosen from 30 land consolidation projects at random in the Jiangsu Province. The agricultural technical efficiency caused by land consolidation was calculated by using a stochastic frontier analysis method. The results of a stochastic frontier production function reveal that land tenure transfer, land fragmentation, non-agricultural income, and crop diversity has undergone significant changes after land consolidation. The overall agricultural technical efficiency of producers had also increased considerably and the average technical efficiency was estimated at 0.924 after land consolidation. Land consolidation directly promotes land tenure transfer while indirectly encouraging non-agricultural employment, which could improve agricultural technical efficiency of producers. Non-agricultural income and crop diversity had a significant correlation with agricultural technical efficiency, but land fragmentation after land consolidation does not significantly improve technical efficiency. These conclusions are helpful in understanding the impacts of land consolidation, which enriches the academic literature in related fields and improves the policy of land consolidation in China and other developing countries.

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