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Purpose: Excessive application of nitrogen fertilizers on farmland widely occurs in China, which has been recognized as one of the main sources of non-point pollution. To reduce the nitrogen loss in agricultural soils, some specific biochar can be introduced to increase the water-holding capacity of soils and to reserve soil nutrition. The effects and mechanisms of biochar application on decreasing nutrient losses after fertilization were systematically evaluated and understood through both pot and field experiments. Materials and methods: This study was objected to investigate the effects of neutral biochar (NBC, pH 6.6–7.1) and its combination with urease inhibitor (UI) on nitrogen mitigation and reservation in farmland soil, and the interactions among the mixed soils (biochar, nitrogen fertilizer, and soil) under both pot and field experiments. Results and discussion: The application of straw biochar could reduce the amount of ammonia volatilization in soil. The maximum inhibition of ammonia volatilization loss accounted for 27.67% of fertilizer applications. In field experiments, neutral biochar could reduce the leaching of soil NH4+-N and NO3—-N, and this effect was more evident for NO3—-N (68 mg/kg) compared to no fertilization in the soil layer 20–40 cm. With the addition of neutral biochar and urease inhibitors, the content of soil total nitrogen increased greatly with 1.70 g/kg. Conclusion: Neutral biochar from waste agricultural straw and commercial urease inhibitors were applied for nitrogen reservation in pot and field experiments. The application of neutral biochar played a positive role in lower volatile ammonia loss and higher nitrate content compared to urease inhibitor application only. These findings reveal the potential of neutral biochar for the improvement of agricultural soil. [ABSTRACT FROM AUTHOR]

Pickled mustard tuber, a worldwide condiment, is increasing at a fast growth rate. Its production generates a considerable amount of hypersaline wastewater containing NaCl of 7 wt.%, COD of 30,000 mg L−1, NH3-N of 400 mg L−1, and TP of 300 mg L−1. Pickled mustard tuber wastewater (PMTW) has severe effects on crops, deterioration of water quality, soil infertility and ecological systems. Due to the technic difficulties and insufficient support from the local governments; however, PMTW has not yet been widely investigated and well summarized. Therefore, this manuscript reviewed the relatively latest advances in PMTW. Physicochemical and biological hybrid processes mainly treat PMTW and the corresponding cost is 6.00 US dollars per ton. In the context of double carbon capture capacity in China and the development of the pickled mustard industry, PMTW sauce and sustainable reuse such as nutrient recovery, acid and alkaline regeneration and renewable energy may be bright prospects. [ABSTRACT FROM AUTHOR]

Landfill leachate concentrate (LLC) is a concentrated waste stream from landfill leachate treatment systems and has been recognized as a key challenge due to its high concentration of salts, heavy metals, organic matters, etc. Improper management of LLC (e.g. reinjection) would exacerbate the performance of upstream treatment processes and pose risks to the surrounding environments near landfill sites. Addressing the challenge and recovering resources from LLC have thus been attracting considerable attention. Although many LLC treatment technologies have been developed, a comprehensive discussion about the challenges still lacks. This review critically evaluates mainstream LLC treatment technologies, namely incineration, coagulation, advanced oxidation, evaporation and solidification/stabilization. We then introduce a geopolymer-based solidification (GS) process as a promising technology owning to its simple casting process and reusable final product and summarize engineering applications in China. Finally, we suggest investigating hybrid systems to minimize LLC production and achieve the on-site reuse of LLC. Collectively, this review provides useful information to guide the selection of LLC treatment technologies and suggests a sustainable alternative for large-scale application, while also highlighting the need of joint efforts in the industry to achieve efficient, ecofriendly and economical on-site management of landfill waste streams. [ABSTRACT FROM AUTHOR]