威廉腔环蚓（Metaphire guillelmi）对~（14）C-土壤有机质转化的研究

土壤有机碳是全球碳循环的重要组成部分,而大型土壤动物对土壤碳库的稳定性起着重要的决定作用。利用14C示踪技术,以14C-葡萄糖制备微生物源的土壤有机质（Soil organic matter,SOM）,以蚯蚓威廉腔环蚓（Metaphire guillelmi）为代表,研究了14C-SOM在含有蚯蚓的两种土壤、不含蚯蚓的对照土壤和不含蚯蚓的蚓粪中的矿化、残留物在土壤和蚓粪中分布以及蚯蚓对14C-SOM的吸收。结果显示,15 d的培育期内蚯蚓显著加快了14C-SOM的矿化,在土壤中的矿化量是不含蚯蚓的对照土壤中矿化量的1.5～1.7倍,然而当移出蚯蚓后,残留14C-SOM在两种土壤中40 d内的矿化都比对照土壤中低。大约有4.2%～4.8%的14C-SOM被蚯蚓吸收利用。在有蚯蚓存在的土壤中,14C-SOM残留物在胡敏素中的含量有所增高,而在溶解有机物（DOM）中的含量显著降低。14C-SOM在不含蚯蚓的蚓粪中55 d内的矿化量和矿化动力学以及残留分布与在对照土壤中均没有显著区别。这些结果表明,蚯蚓对微生物源14C-SOM转化的影响主要是蚯蚓的肠道作用,这种作用可表现在两个方面,即初期对14C-SOM矿化的促进作用以及后期对14C-SOM残留物的稳定化作用。后续工作中应进一步研究蚯蚓对其它来源SOM降解和转化的作用,阐明蚯蚓对SOM稳定性的控制机理,对揭示全球碳循环规律具有重要的意义。     

河流中有机碳的环境效应及其研究方法概述

有机碳是地表各种环境介质中的重要化学组分,是生态系统中能量与物质循环的重要介质。有机碳作为河流榆移的主要物质,榆运过程中对周围环境产生的效应不容忽视。本文结合近年来国内外研究动态,探讨并总结了河流作为碳源／汇角色的作用,有机碳对重金属迁移过程和水体生产力产生的影响;指出随着人类活动影响的加剧,河流有机碳正发生着显著变化,并影响到我们自身的生活;总结了传统的研究有机碳的方法,并对正在发展的研究方法做一下探讨。     

Flow and flame visualization near the upper flammability limits of methane/air and propane/air mixtures at elevated pressures

In this study, direct visualization of flow and flame from the ignition of methane/air and propane/air mixtures near the UFL at elevated pressures of up to 2.0 MPa were obtained with a test cell comprised of double-sided plexiglass and a containment vessel with double-sided glass. These visualizations allowed direct observations of ignition and flame near UFL at elevated pressures. Two distinctive features were observed in ignition at elevated pressures that differ from those under ambient pressure: the hot igniter formed a convective plume, rather than a convection cell; and the flame initiated from the top of the test cell and propagated downwards, rather than directly from the igniter. Both these distinctive features are characteristics of convection at high Rayleigh number accompanied with increased gas density at elevated pressures. Our study also shows that visualization of the formation of planar flame provides the most objective criterion for defining flammability limits at elevated pressures.     

客运专线桥梁的地震能量响应分析

在依据能量平衡原理建立的客运专线桥梁地震能量方程的基础上,考虑柔性地基效应和地震动特性的影响,利用大型有限元分析(FEA)软件ANSYS建立某客运专线双柱式桥墩的FEA模型。研究了考虑土-结构相互作用效应的客运专线桥梁进入非弹性状态后的地震能量响应以及各类能量在结构整体系统中的分配规律。分析结果表明:结构滞回耗能和阻尼耗能是客运专线桥梁消耗地震能量的主要方式,而土-结构相互作用和地震动峰值加速度(PGA)对客运专线桥梁的地震总输入能、滞回耗能、阻尼耗能有显著影响,不容忽视。     

餐厨废水中解磷菌、固氮菌及解钾菌的互作效应研究

针对餐厨垃圾无害化和资源化处理过程中产生的餐厨垃圾废水处理难题,探讨餐厨垃圾废水用作发酵基制备复合液态菌肥过程中菌株间的互作效应。将解磷菌、固氮菌及解钾菌在餐厨废水中单独和混合接种,通过测定菌悬液细胞密度的变化来研究它们之间的互作效应。研究表明,在餐厨垃圾废水中解磷巨大芽孢杆菌对圆褐固氮菌有促进作用,与解钾芽孢杆菌之间存在拮抗作用,同时圆褐固氮菌与解钾芽孢杆菌之间亦存在拮抗作用,3个菌株的混合培养中解磷巨大芽孢杆菌为优势菌种。研究结果同时显示,利用餐厨垃圾废水可以制备合格的复合菌肥。     

Halogen-specific total organic halogen analysis: Assessment by recovery of total bromine

Determination of halogen-specific total organic halogen(TOX) is vital for studies of disinfection of waters containing bromide, since total organic bromine(TOBr) is likely to be more problematic than total organic chlorine. Here, we present further halogen-specific TOX method optimisation and validation, focusing on measurement of TOBr. The optimised halogen-specific TOX method was validated based on the recovery of model compounds covering different classes of disinfection by-products(haloacetic acids, haloacetonitriles,halophenols and halogenated benzenes) and the recovery of total bromine(mass balance of TOBr and bromide concentrations) during disinfection of waters containing dissolved organic matter and bromide. The validation of a halogen-specific TOX method based on the mass balance of total bromine has not previously been reported. Very good recoveries of organic halogen from all model compounds were obtained, indicating high or complete conversion of all organic halogen in the model compound solution through to halide in the absorber solution for ion chromatography analysis. The method was also successfully applied to monitor conversion of bromide to TOBr in a groundwater treatment plant. An excellent recovery(101%)of total bromine was observed from the raw water to the post-chlorination stage. Excellent recoveries of total bromine(92%–95%) were also obtained from chlorination of a synthetic water containing dissolved organic matter and bromide, demonstrating the validity of the halogen-specific TOX method for TOBr measurement. The halogen-specific TOX method is an important tool to monitor and better understand the formation of halogenated organic compounds, in particular brominated organic compounds, in drinking water systems.     

良种补贴政策的环境效应研究

以小麦良种补贴政策为例,将单位面积化肥施用量作为环境效应评估的代理变量,基于市级农业数据构建了双重差分模型,量化了政策实施导致的单位面积化肥施用量的变化,进而评估化肥施用量变化导致的农户种植成本、温室气体排放和社会碳成本的变化.结果表明,该政策实施使单位面积化肥施用量下降了5.9%,农户种植成本减少了139.42元/hm²,温室气体排放减少了822.06kg CO₂e/hm²,社会碳成本减少了301.91元/hm²,充分补偿了良种补贴的财政支出.建议未来农业补贴政策的制定、改进及推广应充分考虑其潜在的环境影响,以加强农业增产和环境效益的协同.     

The antiestrogen-like activity and reproductive toxicity of 2,6-DCBQ on female zebrafish upon sub-chronic exposure

2,6-Dichloro-1,4-benzoquinone (2,6-DCBQ), an emerging water disinfection by-product, is widely detected in water resources. However, its potential effects on the reproductive system are largely unknown. Here, we investigated the long-term effects of 2,6-DCBQ on gonadal development by exposing zebrafish from 15 to 180 days postfertilization (dpf). Following exposure to 2,6-DCBQ (20 and 100 µg/L), female-specific effects including delayed puberty onset, retarded ovarian growth and breakdown of the zona radiata were observed, resulting in subfertility in adult females. Adverse effects in folliculogenesis disappeared two months after cessation of 2,6-DCBQ administration. In contrast, no adverse impacts were noted in male testes. The effects on females were associated with significant reduction in 17β-estradiol (E2) level, suggesting a role for 2,6-DCBQ in anti-estrogenic activity. E2 level change in blood was further supported by dysregulated expression of genes (cyp19a1a, fshb, kiss3, esr2b, vtg1, and vtg3) related to the hypothalamic-pituitary-gonad-liver (HPGL) axis. The present study demonstrates for the first time that 2,6-DCBQ induces reproductive impairments in female zebrafish through disrupting 17β-estradiol level.     

Sources of ambient non-methane hydrocarbon compounds and their impacts on O3 formation during autumn, Beijing

The field observation of 54 non-methane hydrocarbon compounds (NMHCs) was conducted from September 1 to October 20 in 2020 during autumn in Haidian District, Beijing. The mean concentration of total NMHCs was 29.81 ± 11.39 ppbv during this period, and alkanes were the major components. There were typical festival effects of NMHCs with lower concentration during the National Day. Alkenes and aromatics were the dominant groups in ozone formation potential (OFP) and OH radical loss rate (L_OH). The positive matrix factorization (PMF) running results revealed that vehicular exhaust became the biggest source in urban areas, followed by liquefied petroleum gas (LPG) usage, solvent usage, and fuel evaporation. The box model coupled with master chemical mechanism (MCM) was applied to study the impacts of different NMHCs sources on ozone (O₃) formation in an O₃ episode. The simulation results indicated that reducing NMHCs concentration could effectively suppress O₃ formation. Moreover, reducing traffic-related emissions of NMHCs was an effective way to control O₃ pollution at an urban site in Beijing.     

Investigating Potential for Depensation in Marine Turtles: How Low Can You Go?

Abstract:  Where mechanisms inherent within the biology of a species affect individual fitness at low density, demographic-scale depensation may occur, hastening further decline and leading ultimately to population extirpation and species extinction. Reduction in fertility at low population densities has been identified in marine and terrestrial species. Using data on hatch success and hatchling-emergence success as proxies for fertilization success, we conducted a global meta-analysis of data from breeding aggregations of green turtles ( Chelonia mydas ) and loggerhead turtles ( Caretta caretta ). We found that there has been no reduction in fertility in small nesting aggregations in either of these species worldwide. We considered mechanisms within the mating strategies and reproductive biology of marine turtles that may allow for novel genetic input and facilitate enhanced gene flow among rookeries. Behavioral reproductive mechanisms, such as natal philopatry and polyandry, may mitigate potential impacts of depensation and contribute to the resilience of these species.