Anaerobic digestion of sludge by different pretreatments: Changes of amino acids and microbial community

•Tryptophan protein, and aromatic protein I/II were the key identified proteins. •Cysteine was more correlated with methane production than other amino acids. •The presence of cysteine can promote methane production and degradation of VFAs. •The presence of cysteine can lower ORP and increase biomass activity. •Predominant Tissierella and Proteiniphilum were noted in pretreated sludge samples. Many studies have investigated the effects of different pretreatments on the performance of anaerobic digestion of sludge. However, the detailed changes of dissolved organic nitrogen, particularly the release behavior of proteins and the byproducts of protein hydrolysis-amino acids, are rarely known during anaerobic digestion of sludge by different pretreatments. Here we quantified the changes of three types of proteins and 17 types of amino acids in sludge samples solubilized by ultrasonic, thermal, and acid/alkaline pretreatments and their transformation during anaerobic digestion of sludge. Tryptophan protein, aromatic protein I, aromatic protein II, and cysteine were identified as the key dissolved organic nitrogen responsible for methane production during anaerobic digestion of sludge, regardless of the different pretreatment methods. Different from the depletion of other amino acids, cysteine was resistant to degradation after an incubation period of 30 days in all sludge samples. Meanwhile, the “cysteine and methionine metabolism (K00270)” was absent in all sludge samples by identifying 6755 Kyoto Encyclopedia of Genes and Genomes assignments of genes hits. Cysteine contributed to the generation of methane and the degradation of acetic, propionic, and n-butyric acids through decreasing oxidation-reduction potential and enhancing biomass activity. This study provided an alternative strategy to enhance anaerobic digestion of sludge through in situ production of cysteine.     

Long-chain alkanes in the atmosphere: A review

As a representative species of intermediate volatile organic compounds (IVOCs), long-chain alkanes are considered to be important precursors of secondary organic aerosols (SOA) in the atmosphere. This work reviews the previous studies on long-chain alkanes in the atmosphere: (1) the detection methods and filed observations of long-chain alkanes in both gas and particle phases are summarized briefly; (2) the laboratory studies of long chain alkanes are reviewed, the kinetic data, reaction mechanism, SOA yields, and physicochemical properties of SOA are included in detail; (3) the research progress related to model simulations of long-chain alkanes are also discussed. In addition, based on available research results, several perspective contents are proposed that can be used as a guideline for future research plans.     

延安“乡村振兴南沟模式”的内涵与启示

农业农村优先发展是中共二十大提出的重要目标,乡村振兴是农业农村优先发展的标志性成果形式。黄土高原丘陵沟壑区既是严重水土流失区,也是我国经济社会相对落后的贫困区。如何实现生态效益、经济效益和社会效益三者有机协同发展是该区域亟待解决的问题。延安市安塞区高桥镇南沟村率先优化南沟村生态景观格局,历经八载把原来的贫困村打造成为全国乡村振兴的典范,探索出了一条生态建设与乡村振兴有机耦合发展之路。本文从科学与社会的综合视角分析了延安市安塞区高桥镇南沟村的“化蝶”经验,梳理发现“南沟模式”的内涵可以归纳为“景观多元化、生态经济化、农业现代化、人民福祉化”。南沟村的蝶变为黄土高原丘陵沟壑区乡村振兴提供借鉴案例,但是借鉴不等于照搬照抄,必须根据自然禀赋实事求是地推进乡村振兴。     

基于航班运行规律的典型机场NOx浓度临近预测方法研究

针对天津机场区域考虑航班运行影响,应用广义加性模型（Generalized Additive Model,GAM）建立污染物浓度预测模型,对因子间的共线性问题和交互作用进行改进,得到最优的NO_x浓度预测模型.选取天津机场区域2019年11月—2020年3月环境、气象及航班数据,建立改进的GAM.结果显示：（1）改进的GAM预测效果优,可以更加准确地预测浓度峰值及变化趋势;（2）样本量会影响模型选择的因子数量及模型性能;（3）改进模型adj-R²为0.940,实测和预测NO_x浓度的相关系数为0.975,预测效果好;（4）航班活动对机场区域污染物浓度影响较大.改进的GAM考虑污染物浓度与影响因子之间的复杂非线性关系及影响因子之间交互作用对污染物浓度变化的影响,使模型精度进一步提升. GAM对污染物浓度的准确预测可为机场区域污染防治提供依据.     

城市污水处理厂优化设计研究

对城市污水处理厂优化设计理论的发展历史作了回顾，对不同时期的几个系统模型作了介绍，提出了城市污水处理厂优化设计理论研究中几有待进一步研究的问题。     

小型砂滤池在废水处理中的应用

本文通过湿式除尘后的废水治理及工程实例,探讨了小型砂滤池在废水处 理中应用的可行性。     

影响活性污泥沉降因素及设计沉淀池应注意问题的探讨

通过理论和实验，对影响活性污泥沉降的多方面因素，进行了详细分析；并对设计沉淀池应注意的问题进行了探讨．     

选矿废水过滤性能的实验研究

通过实验得出 ,不经加药处理的选矿废水 ,污泥比阻 r=33.1× 1 0 1 1 cm/g太大 ,较难过滤 ;加药处理后 ,污泥比阻r=0 .0 6× 1 0 1 1 cm/g变小 ,可以采用较先进的机械脱水处理。     

苏州市与温州市不同经济模式下流动人口的空间特征比较

我国正经历着一个巨大的人口流动潮，其主要流向是中西部向东部发达地区流动，农村地区向城镇密集的大中城市地区流动。发达地区的经济模式不尽相同。不同模式下地区流动人口的流向也存在着一定差异。分析比较不同发达地区的流动人口特征，对当地经济政策、产业定位、管理制度等方面均有着非常重要的指导作用。以发达地区流动人口的空间特征为研究目标，以最具代表性的“苏南模式”的苏州市和“温州模式”的温州市两个城市作为研究对象，比较总结两城市的流动人口空间特征与差异，可以看出：苏州市以人口流入为主，温州市流入流出人口数量持平；苏州市吸引外来人口的范围不如温州市广；苏州市城市中流动人口所占比例高过温州市。此外，还对不同经济模式下流动人口空间特征对地区经济发展产生的影响进行了总结，并且给出结论，以期能够对地区的经济发展起到一定的指导和促进作用。     

港口生态工程管理系统及评价方法研究

提出了建立港口生态工程管理的模式及指标体系，探讨了港口生态工程评价方法。