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Abstract Biochar has been used as an amendment to improve soil fertility and increase crop yield. However, the effects of biochar on soil properties and rapeseed yield in upland red soil have not been thoroughly investigated, and the factors crucial for rapeseed yield are not yet clear. A five-year field trial was conducted to investigate the effects the of biochar (biochar application rates of 0, 2.5, 5, 10, 20, 30, and 40 t ha−1, respectively) on soil physicochemical and microbial properties as well as rapeseed yield in upland red soil in Jiangxi Province, China. Results showed that biochar can significantly increase soil pH, available phosphorus, organic carbon, K s, and water retention, however, the influences of biochar on these indexes declined over time. Soil total nitrogen increased significantly when the dose of biochar exceeded 5 t ha−1, and the content of total nitrogen in the 40 t ha−1 biochar treatment increased each year. While the application of biochar gradually increased the contents of NH 4 +-N, NO 3 −-N and enhanced the soil microorganism and enzymatic activities during the first three years, they had returned nearly to their starting values by the end of this study. Rapeseed yield and yield components were significantly improved relative to the control for all biochar amendments in the first year, but the rapeseed yield in all biochar treatments decreased steadily after 2012. According to the principal components analysis and path analysis, the most responsive parameters in the upland red soil were soil acidity and hydraulic properties, meanwhile, soil acidity and hydraulic properties had greater impacts on rapeseed yield than did other indexes. Taken together, these results suggest that biochar can significantly improve soil fertility and rapeseed yield, but the improvements are not permanent. Soil acidity and hydraulic properties were the crucial factors that determined soil fertility and rapeseed yield in upland red soil. Graphical abstract Unlabelled Image Highlights • The effects of 7 rates of biochar in an upland red soil were studied over 5 years. • Soil pH and hydraulic property are major influences on upland red soil fertility. • Biochar can improve rape yield by raising soil pH and water percolation and retention. [ABSTRACT FROM AUTHOR]

A multiscale analysis of meteorological trends was carried out to investigate the impacts of the large-scale circulation types as well as the local-scale key weather elements on the complex air pollutants, i.e., PM 2.5 and O 3 in China. Following accompanying papers on synoptic circulation impact and key weather elements and emission contributions (Gong et al., 2022a; Gong et al., 2022b), an emission-driven Observation-based Box Model (e-OBM) was developed to study the impact mechanisms on O 3 trend and quantitatively assess the effects of variation in the emissions control over 2013-2020 for Beijing, Chengdu, Guangzhou and Shanghai. Compared with the original OBM, the e-OBM not only improves the performance to simulate the hourly O 3 peak concentration in daytime, but also reasonably reproduces the maximum daily 8-hour average (MDA8) O 3 concentrations in the four cities. Based upon the sensitivity experiments, it is found that the meteorology is the dominant driver for the MDA8 O 3 trend, contributing from about 32 % to 139 % to the variations. From the mechanistic point of view, the variations of meteorology lead to the enhancement of atmospheric oxidation capacity and the acceleration of O 3 production. Further evaluation to the emission changes in four cities shows that the O 3 -precursors relationships of the four cities have been changed from the VOC-limited regime in 2013 to the transition regime or near-transition regime in 2020. Though the NO x /VOCs ratios have been obviously decreased, the emission reductions up to 2020 were still not enough to mitigate O 3 pollution in these cities. It is emphasized in this study that the strengthened control measures with maintaining a certain ratio of NO x and VOCs should be implemented to further curb the increasing trend of O 3 in urban areas., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

The PM 2.5 were sampled in three different urban environments: (city of) Chengdu, Leshan, and Dazhou, which are located in Sichuan Basin. 8 types of water-soluble ion and 25 types of metal element were measured in each PM 2.5 sample across the seasons of 2017. The study results suggest that the joint PM 2.5 pollution among the three cities mainly occurred in autumn and winter, and the air quality of Chengdu and Leshan was largely affected by Dazhou. Overall, the mass concentrations of PM 2.5 of these three cities exhibited no statistically significant differences. However, Leshan had the highest level of ionic pollution, and the dominant form of inorganic compound in ambient PM 2.5 was NH 4 NO 3 , and a competitive relationship between form of NH 4 NO 3 and (NH 4 ) 2 SO 4 (NH 4 HSO 4 ) was found as well. High homology between SO 4 2 - and NO 3 - has been observed in all the three cities, and the ratio between [SO 4 2 - ] and [NO 3 - ] indicated that the stationary source contributed the most to ambient PM 2.5 in Dazhou. The mass concentrations of the total metal elements from the three cities exhibited similar levels, nevertheless, Dazhou had the highest mass fraction of total metal elements in PM 2.5 . The enrichment factor of each element indicated that the natural source was highly contributory to the crustal elements in PM 2.5 of all the three cities, whereas Cr, Cu, Se, Mo, Cd, Tl and Bi were primarily originated from anthropogenic source. In addition, the source apportionment of PM 2.5 suggest that Dazhou had the different factors and factor-contributions comparing with Chengdu and Leshan., (Copyright © 2019. Published by Elsevier B.V.)

Domestic trade flourishes with economic development and the spatial separation of production and consumption. Therefore, the prosperity of trade is accompanied by the transfer of pollution from the demand side to the supply side, which could potentially worsen the environmental quality of the supply side. Despite a large number of studies on the pollution haven hypothesis in international trade, little attention has been paid to testing the hypothesis in domestic trade. Here, combining a multiregional input-output analysis and a gravity model of trade in China, we provide an empirical test to address this problem for the first time. We also assess the factors affecting the SO 2 emissions embodied in trade, including population, economic development, coal consumption, distance, and environmental regulations. We found that domestic trade contributed approximate one third of the total SO 2 emissions in China, and interprovincial transfers of SO 2 embodied in trade were significantly determined by the population, economic development, coal consumption of the trade pairs, as well as their distance. SO 2 emission mitigation policies, such as emission reduction target and sulfur dioxide control zone, has a more significant influence on the direct transfer of SO 2 emission via direct bilateral trade, while their effects were largely offset by indirect trade (through third-party transfers). Our results do not support the pollution haven hypothesis existed in domestic trade in China during 2007-2012. Our paper sets an example and provides a reference for the domestic pollution transfer problem from an econometric perspective. Further attempts on testing pollution haven hypothesis in consideration of various pollutants are still needed to arrive at a robust conclusion., (Copyright © 2019 Elsevier B.V. All rights reserved.)