Clean-energy substitution technology for existing residential buildings in cities is an inevitable choice for sustainable development and low-carbon ecological city construction. In this paper, the current status of energy-saving renovation and renewable-energy applications for existing residential buildings in various cities in China was summarized by using statistical methods. The geographical distribution of clean-energy power generation in primary energy production in China was explored in depth. According to different climatic divisions for existing urban residences, clean-energy production and consumption were analyzed and predicted based on the STIRPAT model. The results show that the energy consumption of urban residential buildings in 2016 increased by 43.6% compared with 2009, and the percentage of clean energy also increased from 7.9% to 13.4%. Different climatic regions have different advantages regarding clean energy: nuclear power generation leads in the region that experiences hot summers and warm winters, whereas wind and solar power generation lead in the cold and severely cold regions. The present results provide basic data support for the planning and implementation of clean-energy upgrading and transformation systems in existing urban residences in China.

The crucial role of the fluorescent components of dissolved organic matter (DOM) in controlling antimony (Sb) mobilization in groundwater has been confirmed. However, the molecular signatures contributing to Sb enrichment in DOM remain unknown. This study aims to investigate the origins and molecular compositions of DOM in different high-Sb aquifers (Sb-mining and no-Sb-mining aquifer), as well as compare different molecular signatures of DOM and mechanisms for Sb migration. The findings showed that Sb concentrations in Sb-mining aquifer exhibited a positive correlation with lignin- and tannin-like molecules characterized by high O/C and low H/C ratios, indicating an increased abundance of aromatic components with higher Humification Index and SUV-absorbance at 254 nm, compared to no-Sb-mining aquifer. Correspondingly, the complexation and competitive adsorption were considered as the predominate formation mechanisms on Sb enrichment in Sb-mining aquifer. In addition, high abundances of bioreactivity DOM may facilitated the migration of Sb via electron transfer and competitive adsorption in native no-Sb-mining aquifer. The outcomes of this investigation offer novel insights into the mechanism on Sb enrichment influenced by DOM at the molecule level.

The molecular weight is a fundamental property of dissolved organic matter (DOM) that affects the fate of arsenic (As) in groundwater. However, there is limited knowledge regarding the various molecular weights on the geochemical transformation mechanisms of DOM with respect to antimony (Sb) migration in groundwater. A total of 20 samples were collected from high- and low-Sb D3x4 waters in the world’s largest antimony mine to evaluate the effects of different molecular weights of DOM on Sb mobilization using a sequential ultrafiltration technique. Dissolved Sb occurred mainly in the <1kDa fraction, while total Fe (TFe) colloids and DOM mostly existed in <0.45-μm and <100-kDa fractions, respectively. A protein-like component with a higher biological index (BIX), lower humification index (HIX), and specific ultraviolet absorbance (SUVA254) demonstrated a higher binding potential to Sb. Owing to the lower values of δ13CDIC a nd t he d ifference b etween δ13CDIC and δ13CDOC, the microbial degradation of DOM had a substantial contribution to Sb mobility in the D3x4 water. The results obtained from this research contribute to our comprehension of the biogeochemical behavior of antimony in shallow groundwater.

Groundwater pollution in chemical industrial parks is typically concealed, delayed in onset, and difficult to remediate. Moreover, the long-term migration of typical pollutants in aquifers may threaten the safety of surrounding water sources and river water environments. In this study, a numerical subsurface flow model was constructed for a chemical industrial park in a mining area of Inner Mongolia by generalizing the Quaternary loose-rock pore aquifer system, based on hydrogeological surveys and groundwater monitoring data, using MODFLOW. A solute transport model was then established through coupling with MT3DMS to predict the spatiotemporal evolution of ammonia nitrogen and 1,2-dichloroethane in the absence of new pollution sources, and the influence of subsurface flow velocity on pollutant diffusion was further analyzed. The results show that the contaminant plume area gradually increases over the simulation period: the ammonia nitrogen plume expands from 1.84 km² to 3.98 km², and the 1,2-dichloroethane plume expands from 1.47 km² to 3.05 km². Contaminant concentrations in individual wells generally exhibit a downward trend; nonetheless, long-term exceedance risks persist at specific sites. These findings provide a scientific basis for groundwater pollution risk management, water source protection, and subsequent remediation decisions for chemical industrial parks in arid and semi-arid regions.

Carbon peak and carbon neutrality have been incorporated into the ecological civilization construction and social development strategy in China. At the same time, the implementation of clean energy transformation in urban settlements only relies on the mandatory provisions in the transformation design standards for a long time, and the transformation effect is inconsistent with the actual transformation demands of residents, which is contrary to the original intention of improving the living environment. A clean energy transformation investigation was conducted in the existing urban settlements in China from July to August 2020 in order to study the influencing factors and demands of residents' transformation intention in the clean energy transformation. The influencing factors and demand of urban residents' clean energy transformation intention were analyzed according to different climate zones, multivariate logistic regression and binary logistic regression. Taking Shandong Province as a case, a specific analysis of residential energy consumption data in cold climate zones is carried out, and the peak of residential carbon dioxide is predicted under the condition of different annual replacement rates of clean energy power generation. The results show that the residents' intention index of clean energy transformation is the highest in hot summer and cold winter area. The low motivation of clean energy transformation intention mainly comes from low annual income and high cost of living energy consumption considering the influencing factors of urban residents' clean energy transformation intention. In contrast, the high motivation of clean energy transformation intention is mainly from the not popular user of clean energy. For the demand of clean energy transformation, residents in cold regions have clear demand for energy-saving transformation of external walls and air conditioning, etc. residents consumption can be achieved the carbon peak by 2030 only when the annual growth rate of clean electricity reaches more than 5%.