Bioelectrochemical removal of tetracycline from four typical soils in China: A performance assessment.

Exposure to tetracycline in soil causes microbial mutations. Soil microbial fuel cells (MFCs) can promote the degradation efficiency of contaminants while generating bioelectricity under anaerobic conditions. MFC performance varies amongst different types of soils due to distinctive soil properties. This study assesses the performance of soil MFCs filled with four typical Chinese soils and explores key factors regulating bioelectricity generation and tetracycline degradation. Except for the MFCs filled with black soil, tetracycline degradation rates improved in soil MFCs, particularly in those filled with Chao soil, which enhanced the degradation rate by 39% relative to the corresponding control. Additionally, soil MFCs filled with Chao soil exhibited the highest charge output of 1347 ±â€¯357C, which was 100-499% higher than that of MFCs with other soils. According to redundancy analysis, soil particle size, pH, conductivity and dissolved organic carbon content showed positive association with tetracycline degradation and charge output, while the adsorption of tetracycline had a negative association with degradation rate. Thus, the adsorption of tetracycline restricted its removal efficiency in soil MFCs, and high soil conductivity and large particle size promoted electron transfer, enhancing biocurrent intensity, which increased tetracycline degradation efficiency.

Row Ratios of Intercropping Maize and Soybean Can Affect Agronomic Efficiency of the System and Subsequent Wheat.

Intercropping is regarded as an important agricultural practice to improve crop production and environmental quality in the regions with intensive agricultural production, e.g., northern China. To optimize agronomic advantage of maize (Zea mays L.) and soybean (Glycine max L.) intercropping system compared to monoculture of maize, two sequential experiments were conducted. Experiment 1 was to screening the optimal cropping system in summer that had the highest yields and economic benefits, and Experiment 2 was to identify the optimum row ratio of the intercrops selected from Experiment 1. Results of Experiment 1 showed that maize intercropping with soybean (maize || soybean) was the optimal cropping system in summer. Compared to conventional monoculture of maize, maize || soybean had significant advantage in yield, economy, land utilization ratio and reducing soil nitrate nitrogen (N) accumulation, as well as better residual effect on the subsequent wheat (Triticum aestivum L.) crop. Experiment 2 showed that intercropping systems reduced use of N fertilizer per unit land area and increased relative biomass of intercropped maize, due to promoted photosynthetic efficiency of border rows and N utilization during symbiotic period. Intercropping advantage began to emerge at tasseling stage after N topdressing for maize. Among all treatments with different row ratios, alternating four maize rows with six soybean rows (4M:6S) had the largest land equivalent ratio (1.30), total N accumulation in crops (258 kg ha(-1)), and economic benefit (3,408 USD ha(-1)). Compared to maize monoculture, 4M:6S had significantly lower nitrate-N accumulation in soil both after harvest of maize and after harvest of the subsequent wheat, but it did not decrease yield of wheat. The most important advantage of 4M:6S was to increase biomass of intercropped maize and soybean, which further led to the increase of total N accumulation by crops as well as economic benefit. In conclusion, alternating four maize rows with six soybean rows was the optimum row ratio in maize || soybean system, though this needs to be further confirmed by pluri-annual trials.