Identification of Growth-promoting Bacteria from Rhizosphere of Pastures and Their Effects on Growth of Lotus corniculatus L.

[Objectives] This study was conducted to explore the interaction between nitrogen-fixing and phosphate-solubilizing strains and the optimal combination of different functional strains,in order to provide a theoretical basis for the development of PGPR compound fertilizers suitable for local environment.[Methods] In this study,16S rDNA gene sequence analysis was used to identify fast-growing and competitive strains from pasture nodules and rhizosphere soils in Guizhou Province,and three representative Rhizobia and phosphorus-solubilizing bacteria were chosen for the test of bacterial combination when reducing 50% of nitrogen and 30% of phosphorus.The effects of different strain combinations on the plant height,root length,aboveground and underground biomass of Lotus corniculatus L.were investigated,and the total nitrogen and total phosphorus contents of the plants were determined.[Results] The mixed bacterial agents could promote the increase of root biomass,and the effects of A1,A3,B3 and C3 were the most obvious.The fresh weight and dry weight of the roots of L.corniculatus increased by 30.35%-168.45% and 26.43%-180.00%,respectively,and A3,B3,B2 and C3 had the best effects.The total phosphorus content of the plants increased by 12.79%-55.25% compared with the CK2;and most of the bacterial agents with significant growth-promoting effects showed decreased total nitrogen contents,while those with non-significant growth-promoting effects showed significantly-increased total nitrogen contents,which were not as much as the CK1.Comprehensively,the most productive combination was C3,namely R27-2 Rhinohizobium fredii and P33-3 Stenotrophomonas rhizophila.[Conclusions] This study can provide a theoretical basis for the production and promotion of bacterial fertilizers.

Migration and fate of polycyclic aromatic hydrocarbons in bioretention systems with different media:experiments and simulations

Polycyclic aromatic hydrocarbons(PAHs)present significant risks to human health owing to their carcinogenic,teratogenic,and mutagenic properties.The contamination of surface water with PAHs via runoff has become a prominent source of water pollution.While the capacity of bioretention systems to remove PAHs from runoff is recognized,the dynamics of PAH migration and degradation in these systems are not well-understood.This study aims to explain the migration and fate of PAHs in bioretention systems through a series of experiments and model simulations.This study constructed bioretention systems with three different media types and found that these systems achieved PAH load reductions exceeding 92%.Notably,naphthalene(NAP),fluoranthene(FLT),and pyrene(PYR)tended to accumulate in the media’s upper layer,at depths of 10 to 40 cm.To further analyze the migration and fate of PAHs during multi-site rainfall events and across prolonged operation,we applied the HYDRUS-1D model under three distinct scenarios.The findings of this study indicated that NAP degraded in 40 d,whereas FLT and PYR showed incomplete degradation after 120 d.During continuous rainfall events,there was no clear pattern of PAH accumulation;however,FLT and PYR persisted in the bioretention systems.The combination of experimental and simulation findings highlights the inevitable accumulation of PAHs during extended use of bioretention systems.This research provides a theoretical basis for improving operational efficiency,advancing PAH degradation in bioretention systems,and reducing their toxicity.

在线论坛中高质量数字化读写实践何以实现?——师生交互作用质性比较分析的启示

数字素养是人们适应数字时代必不可少的能力素质,在基础教育阶段以数字化读写实践的方式开展数字素养教育具有必要性和紧迫性。虽然已有研究表明,教师角色和学生个体差异影响着学生的数字化读写实践,但对于教师和学生这两个维度交互作用的影响机制还缺少必要的关注。研究基于一门高中生数字素养在线课程,以质性比较分析方法为主线,综合采用开放性编码、关联性编码、内容分析等分析技术,考察教师的教学支持和教学反馈对不同性格特质、数字技能和读写能力的学生基于在线论坛的自主表达和人际互动两类数字化读写实践的影响。研究结果表明:第一,高质量的数字化读写实践是教师和学生维度多因素共同作用的结果,这些因素交互作用形成了不同的组态;第二,外向型性格、较高数字技能、较高读写能力的学生在基于在线论坛的数字化读写实践中具有明显优势;第三,教师在学生的数字化读写实践中具有辅助性影响,而非关键性影响,且这种辅助性影响主要体现在“促优”,而非“扶弱”。研究从微观层面上识别了教师和学生维度的多个因素作用于数字化读写实践的多重并发路径,对基础教育阶段数字素养在线教学中如何进行教学干预提供了基于证据的策略支持。