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Maintaining crop outputs to feed its large population with limited resources while simultaneously mitigating carbon emissions are great challenges for China. Improving the efficiency of resource use in crop production is important in reducing carbon emissions. This paper constructs a methodological framework combining emergy-based indicator accounting and a nonseparable undesirable output slack-based measurement (SBM) data envelopment analysis (DEA) model. This framework is used to explore the efficiency of inputs and outputs and the greenhouse gas (GHG) emissions reduction potential for crop production systems, using Zhejiang province, China, as a case study. It is found that an emergy synthesis and a nonseparable undesirable output SBM-DEA framework is compatible with the case study. Crop production in Zhejiang province has relied heavily on an increase in agrochemical inputs to maintain agricultural output. Energy and chemical fertilizer use are determined as the province’s major carbon emissions sources. Although carbon emissions per unit of monetary output has decreased sharply, the carbon emissions per unit emergy output has increased, demonstrating a high carbon intensity reality. The DEA highlighted the differences in crop production efficiency, resource factor redundancy and carbon mitigation potential in the different prefectures of the province. To conclude this research, policies to support low carbon agriculture development, including subsidizing low carbon agriculture technology development and expansion and the cancellation of subsidies to high carbon production factors, such as chemical fertilizer production and sales, are discussed to conclude the research. [ABSTRACT FROM AUTHOR]

In the context of China's dual carbon target, Beijing, as the capital of China, should play an exemplary role in carbon emission reduction. On the premise of optimizing high-emission sectors such as coal and industry, Beijing is still a certain distance from the goal of carbon neutrality. Therefore, on the basis of Beijing's energy resource endowment, considering Beijing's economic development and carbon neutrality goals and scientifically and reasonably planning Beijing's carbon emission reduction path are important tasks. We construct an energy structure optimization model to achieve the goal of carbon neutrality by 2050. The model analysis concludes that the residents and transportation sectors will account for a large proportion of Beijing's total carbon emissions in the future. To achieve the goal of carbon neutrality, the electricity substitution of fossil energy and the high proportion of external power are two necessary measures, and the optimal path of carbon emission reduction is proposed. [ABSTRACT FROM AUTHOR]

The spatial and seasonal distribution of organochlorine pesticides (OCPs) in the sediments of the Yangtze Estuary was investigated. The total concentration of 19 OCPs (∑OCPs), including α-HCH, β-HCH, γ-HCH, δ-HCH, o, p′-DDE, p, p′-DDE, o, p′-DDD, p, p′-DDD, o, p′-DDT, p, p′-DDT, heptachlor, aldrin, heptachlor epoxide (Isomer B, Isomer A), endosulfan I, dieldrin, endrin, endosulfan II and methoxychlor, in the surface sediments ranged from 0.4 to 82.1ngg−1 d.w. The mean values of the ∑OCPs were 8.5±8.3ngg−1 d.w., 26.7±12.1ngg−1 d.w., 40.5±18.2ngg−1 d.w., and 13.0±11.2ngg−1 d.w. for August 2010, November 2010, February 2011 and May 2011, respectively. The highest concentration of OCPs was detected at the river-sea boundary because of the intense resuspension and redeposition of sediments in this area. The OCPs preferred to accumulate in the inner estuary, rather than in the offshore area in the dry season, whereas the opposite occurred in the flood season. This phenomenon was related to the seasonal changes of the Changjiang diluted water (CDW). OCPs in the offshore area were controlled by the ocean currents and the monsoon. There was a southward increase for the OCP deposition in the offshore area in the winter. This increase resulted from the influences of the southward Yellow Sea coastal current and the East China Sea coastal current, as well as the northwest wind in winter. The Three Gorges Dam had an impact on HCH composition by changing the sediment redistribution during the deposition process. [ABSTRACT FROM AUTHOR]