Abstract In the main grain producing areas of China, there are still problems of agricultural non-point source pollution and eutrophication of surrounding surface water caused by excessive application of chemical fertilizers. In order to change the unreasonable traditional fertilization habits of farmers and minimize agricultural non-point source pollution, a fertilizer reduction fertilization project was carried out in Jiangshan City to study the effects of 10%~30% fertilizer reduction on the yield of rice Yongyou 15 and the loss of nutrients (total nitrogen, total phosphorus and total potassium) in surface runoff of paddy fields on the basis of farmers' conventional fertilization. The results showed that there was no significant change in rice yield by reducing the amount of conventional fertilizer by 10%~20%, and the yield by reducing 10% was the highest. The nutrient concentration in the drainage of paddy field quickly rose to the highest value 1h after fertilization, and then nitrogen, phosphorus and potassium quickly decreased by 25.9%~66.0%, 70.1%~88.3% and 25.0%~52.5% after 24h. After that, all nutrients decreased slowly until the end of the experiment. This shows that if the paddy field irrigation water outflow is caused by heavy rain or artificial drainage, the nutrient diversion loss risk period (also a high risk period of non-point source pollution) is within a few days after fertilization. The reduction of chemical fertilizer has a significant impact on the nutrient content in the drainage of paddy field, and the amount of conventional fertilization is reduced by 10%~30%\u one hour after fertilization, the contents of total nitrogen, total phosphorus and total potassium in the drainage decreased by 3.7%~68.2%, 26.3%~64.8% and 5.8%~57.5% respectively. It is of great significance to improve economic benefits and protect the ecological environment in rice production.

Abstract Petroleum hydrocarbon is a kind of global pollutant that is difficult to degrade. The remediation of petroleum hydrocarbon contaminated soil has always been a challenging subject for environmentalists. Microbial immobilization technology (MIT) has the advantages of high efficiency, stability, low cost and environmental friendliness. It shows great application potential in soil remediation. In recent years, the study of microbial immobilization technology for remediation of petroleum hydrocarbon contaminated soil is in the ascendant. Microbial immobilization technology has become an effective way to improve microbial degradation of petroleum hydrocarbons in soil. This paper discusses the research progress of microbial immobilization technology, summarizes the different characteristics of carrier materials, microorganisms, immobilization methods and influencing factors in the immobilization process and their effects on the immobilization effect, and expounds the research status and development trend of immobilization technology for the remediation of petroleum hydrocarbon contaminated soil.

Abstract Bioremediation technology is a low-cost and environment-friendly sustainable remediation technology, but it requires a longer time to repair. In this study, the method of chemical oxidation-enhanced bioreactor remediation of petroleum-contaminated soil was used to explore its remediation effect. Furthermore, biolog ECO board and high-throughput sequencing technology were used to explore the response mechanism of microbial communities. The results showed that after 240 days of biological remediation, bioremediation (NP) and oxidant-enhanced bioremediation (NP_O) treatments reduced the total petroleum hydrocarbons in the soil from 30 649 mg·g-1 to 5 889 mg·g-1 and 2 351 mg·g-1, respectively. The concentration of petroleum hydrocarbons in the soil after oxidation-enhanced bioremediation is lower than that of the national risk control value (GB 36600–2018). The results of BIOLOG ECO micropore analysis and high-throughput sequencing further showed that the microbial activity in the soil treated with oxidants was quickly restored. Genus Microbacterium, paracoccus, pseudomonas, stenotrophomonas, and Porticoccaceae_ C1. B045 were the potential bacterial marker for petroleum hydrocarbon degradation in the chemical oxidation-enhanced bioremediation treatment.

Abstract A graphite electrode was inserted at both ends of the oil-contaminated soil, and a 24 V DC voltage was applied to reduce the potential of the soil between the electrodes to 1 V/cm. The effects of electrokinetic and microbial combined remediation on ph value, soil temperature, organic carbon content, available N, available P, available K and other indexes of petroleum-contaminated soil were studied. The results showed that the optimal degradation rate of the simulated contaminated soil with 2% petroleum concentration was 67.5% after electrokinetic and microbial combined treatment. The effective N, effective P and effective K increased by 1.5, 1.4 and 1.2 times, respectively. At the same time, the addition of electric remediation proved that the ph value and temperature of the soil could be kept in a relatively constant range, providing a stable environment for the life activities of microorganisms, and improving the oil degradation rate.