Arbuscular mycorrhizal fungi (AMF) are widely present in heavy metal-polluted soils, but their effects on straw degradation and plant growth of rotated crops are poorly understood. In this study, a pot experiment was used to simulate the return of fore-rotating crop (Brassica napus L.) straw to farmland with a subsequent planting of maize in a lead–zinc mining area on the Yunnan Plateau, Southwest China, which included four treatments: control (CK), addition of rape straw (SR), inoculation of AMF (AMF), and both AMF inoculation and straw addition (AMF + SR). The effects of AMF on the degradation and nutrient release of the fore-rotating rape straw and the growth, mineral nutrition and the cadmium (Cd) and lead (Pb) contents of the subsequent maize were investigated. Compared with the CK treatment, AMF significantly promoted the degradation of rape straw and the release of mineral nutrients (nitrogen, phosphorus and potassium) as well as the Cd and Pb, increased the content of available nutrients in soil, and improved the mineral nutrient contents in the maize. AMF + SR significantly increased the maize height and biomass by 32–35% and decreased the available Cd and Pb contents in soil and the Cd and Pb contents in the maize by 20–30% and 18–25%, respectively. Moreover, the available Cd and Pb contents in the soil presented significant positive correlations with their contents in the maize but negative correlations with the height and biomass of the maize. Thus, AMF played an important regulatory role in the nutrient cycling and heavy metal accumulation of the crop rotation.

Field experiments were conducted in Dianchi basin to study the effects of straw mulching on the quantity of ammoniated bacteria, actinomycetes, and fungi in maize and broccoli soil, using dilution plate counting method. The results showed that: (1) Compared with bare soil and uncovered soil, plastic mulching and straw mulching could increase the number of microorganisms in Maize soil. Straw mulching could significantly increase the number of fungi in maize soil, reaching 6.5×104 CFU·g−1 dry soil, which was 2.0, 1.4 and 2.7 times as much as that of plastic mulching, uncovered and bare soil respectively. The effects of straw mulching and plastic mulching on the number of other types of microorganisms in maize soils were not significantly different. (2) Compared with bare soil, straw mulching could increase the number of fungi in broccoli soil by 83%, and plastic mulching could increase the number of actinomycetes and fungi. Straw mulching could increase the number of microorganisms in soils, which is of great significance to clarify the microbial mechanism of straw mulching to reduce non-point source pollution.

When preparing lightweight ceramsite using carbide slag, trace amounts of toxic elements are released into the atmosphere due to high-temperature calcination, posing a significant risk to the environment. The real-time monitoring of the released gases is challenging under laboratory conditions while preparing large quantities of ceramsite. Therefore, heating was simulated using experimental data and the FactSage 7.0 thermochemical database to study the release of harmful Al-, C-, H-, S-, and F-containing elements when using carbide slag to prepare lightweight ceramsite. The results indicated that no Al, C, H, S, or F elements were evident in the high-temperature liquid products obtained in a 50 °C to 1150 °C calcination temperature range. Al was present in a solid state with no gaseous products. When the temperature reached 450 °C, CO gas was released and its level increased as the temperature rose. H and S mainly combined into H2S gas, starting at 250 °C and reaching a peak at 1050 °C. H and F primarily combined into HF, starting at 400 °C. Other F-containing gases mainly included SiF4 and TiF3, which began to release at 800 °C and 900 °C, respectively. The release trends of HF, SiF4, and TiF3 were consistent with those of CO. This study aimed to conduct an environmental impact and management assessment for the preparation of lightweight ceramsite using carbide slag. The use of raw material carbide slag for the low-cost treatment of tail gas was proposed, which provides theoretical and up-to-date support for greening the application of the process.