Soil microorganisms promote the recovery of contaminated soil by influencing the cyclic transformation of various substances. In this study, we investigated the impact of mercury pollution on the structure, composition, and main populations of soil microbial communities using a high-throughput sequencing method and observed that mercury pollution significantly influenced the diversity, structure, and distribution pattern of microbial communities. Furthermore, during mercury pollution, the Shannon and Chao indices decreased for the bacterial communities and increased for the fungal communities. Mercury pollution mainly reduced the relative abundances of Proteobacteria (16.2–30.6%), Actinomycetes (24.7–40.8%), and other dominant bacterial phyla. The relative abundance of Ascomycota decreased by 17.4% and 16.7% in alkaline and neutral soils, respectively, whereas the relative abundance of unclassified_k_Fungi increased by 26.1% and 28.6%, respectively. In acidic soil, Ascomycota increased by 106.3% and unclassified_k_Fungi decreased by 71.2%. The results of redundancy and correlation analyses suggested that soil microbial diversity was significantly correlated with soil properties such as pH, cation exchange capacity, soil organic carbon, and total nitrogen (p < 0.05) under different treatments. Our findings highlight the impact of Hg pollution on soil microbial communities, thereby providing a theoretical foundation for the bioremediation of soil Hg pollution.

Replacing chemical fertilizers with human waste for vegetable planting is a traditional, economical, and environmentally friendly waste resource utilization strategy. However, whether the human waste substitute strategy can improve soil fertility and increase crop yield and quality compared to the simple application of chemical fertilizers is still unclear, especially under acidic and alkaline soil conditions. In this study, we studied the effects of different ratios of human waste (urine and feces) to chemical fertilizer on the crop yield, crop quality, soil fertility, and soil chemical parameters in alkaline Cambisols and acidic Alisols cultivated with water spinach (Ipomoea aquatica Forssk.). The application variants of human waste and chemical fertilizer were as follows: (i) Control, no fertilization (CK), (ii) human waste application (HW), (iii) chemical fertilizer application (CF), (iv) 1/3 human waste to chemical fertilizer (P1), and (v) 2/3 human waste to chemical fertilizer (P2). Human waste application increased the total nitrogen, available phosphorus, available potassium, organic matter, NO₃⁻-N, and conductivity in soil, enhanced soil enzyme activity, slowed down soil acidification, and increased the yield, soluble sugar, and vitamin C contents of the water spinach while reducing its nitrate content. Our findings indicate that human waste substitution improved soil fertility while reducing the potential risks of soil acidification, salinization, and human exposure to nitrates. These findings may be applied to increase vegetable production and quality, improve the soil environment, and increase the utilization of human waste as a valuable resource.

The sustainability of intensification of rice production is a prime concern for China. Application of organic amendments, changes in crop rotation system, ducklings’ introduction, and construction of vegetated drainage ditches are some of the original management strategies to mitigate environmental pollution from paddy fields. Although these practices affect the rice culturing system through different mechanisms, there is limited investigation on their effectiveness on nutrient pollution alleviation. Therefore, a field study was carried out with the assessment of soil physico-chemical properties, greenhouse gas emissions, nitrogen removal efficiency, grain yield, and economic benefits by comparing the eco-rice culturing system (ER) to the local single rice cultivation system (CK). Results showed that the ER system can significantly improve soil fertility by increasing the pH in acidic soil, organic matter, total nitrogen (TN), and available potassium (K) content by 5.2%, 25.7%, 19.1%, and 19.4% in relation to CK, respectively. Meanwhile, about 10% of the total fertilizer N was removed from the harvesting of the plant species (Myriophyllum elatinoides and Pennisetum purpureum) in the vegetated drainage ditches. However, the ER system decreased the plant height (1.1%) and the number of tillers (9.6%), resulting in a reduction of the total grain yield (6.0%). Moreover, compared with the CK system, the ER system increased CH₄ cumulative emission, global warming potential (GWP), and greenhouse gas intensity (GHGI) by 11.1%, 8.1%, and 14.3%, respectively, and decreased N₂O by 27.2%, but not statistical significantly (p < 0.05). Even so, by taking the costs of farm operations and carbon costs of greenhouse gas emissions, the net economic benefits by applying the ER system were higher relative to the CK system. Thus, our study provides further understanding of the technology which has the potential to transform sustainable rice production to a more profitable, income generating, and environmentally friendly industry in China.

Rural toilet reform in cold areas is the focus and difficulty of China’s toilet revolution. In this paper, by carrying out the septic tank gradient burial depth test and regular seasonal monitoring of the operation effect of rural septic tanks in cold areas, the frost protection effect and treatment effect of rural toilets in cold areas are clarified, which provide important references for the rural toilet revolution and its practical significance in cold areas of China. Based on controlled tests and correlation analysis methods, different gradient burial depths of septic tanks (40, 60, and 80 cm) and different seasonal operation effects (spring, summer, autumn, and winter) were studied to analyze the influence of factors such as burial depths and temperatures on the effectiveness of anti-freezing and treatment of septic tanks. The results found that the septic tank effluent indexes of the six cold-zone test households could not meet requirements of Class Ⅰ-B in the discharge standard of pollutants for municipal wastewater treatment plants (GB 18918-2002). (The criteria for Class I-B are as follows: COD emission limit of 60 mg/L; SS emission limit of 20 mg/L; TN emission limit of 20 mg/L; TP emission limit of 1 mg/L; NH₃-N emission limit of 8 mg/L); The average removal of suspended solids (SSs), chemical oxygen demand (COD), total nitrogen (TN), total phosphorus (TP), NH₃-N, and NO₃-N by septic tanks was 79.7%, 21.8%, 10.5%, 13.5%, 9.76%, and 2.38%, respectively; the water temperature was significantly positively correlated with SS, TN, and TP; the double-layer insulated septic tank with medium burial depth (60 cm) could operate normally in cold areas in winter. The treatment effect of septic tanks on various indicators basically shows that summer > autumn > spring > winter. Temperature is the main limiting factor affecting the treatment effect of septic tanks.