Yinma River is a typical river in the major Phaeozems zone of Northeast China. It has been suffering an increasing environmental pressure from heavy metal contamination due to the rapid development of population, social-economy and urbanization as well as long term over cultivation. This study investigated the spatial distribution, chemical fraction of heavy metals (Cu, Pb, Zn, Cr, Cd, Ni, As, and Hg) in sediments of Yinma River based on BCR procedure, assessed the contamination level, and identified their sources via multivariate statistical analysis. The chemical fraction results indicated that Cd, Pb, Ni, and Zn exhibited higher mobility susceptibility and bioavailability with a significant and late anthropogenic origin. Hg and Cd might exert a potential hazardous influence on aquatic biota according to the geo-accumulation index (I_geo). The pollution load index (PLI) assessment suggested that all of the sediment samples have been contaminated. Multivariate statistical analysis revealed that Zn, Cu, Hg, Cd, and Pb reflected the anthropogenic sources with a close correlation with TOC and socio-economic development; Ni, As and Cr tended to represent the geochemical background. Furthermore, Changchun City and Shitoukoumen Reservoir as the major drinking water source may be hotspots of the heavy metal contamination in the watershed.

The electrode played an essential role in the operation of CW-MFC system due to its synergistic effect, and the development of electrode strategy has promoted the application of CW-MFC since 2012. In this paper, according to the material and the quantity, the electrode types in CW-MFC were distinctly divided into unified model, composited model, modified model, and multi-electrodes model combined with non-conductive or conductive particle. Different electrode strategies were provided to improve the performance of CW-MFC towards electricity generation, removal of pollutants, and control of greenhouse gas emission, and the coordination mechanism was further reviewed. Furthermore, the development process of the electrode strategy was summarized, and the low-cost, sustainable, and innovated electrode materials were emphatically recommended. For the scale-up application, multi-electrode model was systematically reviewed based on the optimizing of the material, shape, spacing distance, and connection type of electrode. This review may provide guidance to maximize the advantages of CW-MFC applications. Graphical Abstract

Heavy metals are the primary pollutants in agricultural soil and have hindered the sustainable development of agriculture. To control heavy metal pollution, it is essential to identify the pollution sources, particularly the prior source, in agricultural soils. In the current study, Qianguo Irrigation District, a typical agricultural region in Northeast China, was selected to be investigated for the source apportionment of soil heavy metals and identify the prior pollution source. The results showed that the study area was at a moderate pollution level with considerable ecological risk, while Hg and Cd were the main pollutants. Human-health risk assessment indicated that the non-carcinogenic risk for all populations was acceptable (HI < 1), and the carcinogenic risk was not negligible (10⁻⁶ < TCR < 10⁻⁴). The main pollution sources were concluded to be of lithogenic origin (35.5%), livestock manure (25.4%), coal combustion (21.5%), and chemical fertilizers (17.7%). Coal combustion was identified as the prior pollution source, accounting for 47.69% of the RI contribution. This study can provide scientific support for environmental management and pollution control of soil heavy metals in agricultural regions.