中国环境中氮循环的动态模式

对中国960万km~2范围内氮的生物地球化学循环作了初步探讨。该工作建立在对大气、土、生物及水圈界面氮的流通量的研究基础上,以数学方式模拟氮的生物地球化学循环规律,并预测各圈中氮的库存量和流通量的变化趋势。经过验证,模式的收敛性、稳定性及可信度均是好的。     

中国农业土壤N2O排放量估算

采用针对农业土壤痕量气体排放估算开发的、基于N2O的产生、传输和消耗机理的反硝化分解模型(DNDC模型),在建立的有关中国气候、农业土壤和农业生产的分县数据库基础上,估计了我国目前农业土壤N2O的排放量,并分析了气候变化和农业耕作措施对全国N2O排放的影响.结果表明,中国农田土壤的N2O排放总量为0.31(0.18-0.44)Tg(N)·a-1,化肥使用量的变化对N2O排放量的影响最大.     

硫循环的酶促反应机制及湖泊环境效应

在湖泊沉积物表层存在着强烈的生物作用 ,使SO2 -4 转变成S2 -,然后和Fe2 + 结合而固定在沉积物中 ,这种SO2 -4 的清除机制具有重要的环境意义。本文论述了H2 S的产生和各种形态硫转变成SO2 -4 的酶促反应机制 ,并阐述了不同微生物电子传递载体、最终电子受体和电子进入传递链的部位的差异以及生成ATP的数目和环境效应的差异。     

空间环境下碳纤维/双马树脂基复合材料的性能演化及损伤机理

目的基于碳纤维/双马树脂基(CF/BMI)复合材料在航天结构材料中广泛的应用前景,研究其性能演化及损伤机理,为评估与预测其在空间环境下的服役性能及寿命提供理论依据。方法利用地面试验装置模拟不同的空间环境因素包括真空热循环、质子辐照和电子辐照,利用动态力学分析(DMA)、热重分析(TGA)、X射线光电子能谱(XPS)、热膨胀分析、原子力显微镜(AFM)和力学性能测试等手段系统地研究CF/BMI复合材料在空间环境下的性能变化及损伤行为。结果真空热循环能够引发复合材料产生脱气行为与界面脱粘效应,使其横向拉伸强度退化,弯曲强度和层间剪切强度受到热循环初期固化交联作用的影响,呈现先升高后降低的变化趋势。质子辐照导致材料表面层化学键断裂及碳化,使力学性能及热性能受到一定程度的损伤。电子辐照能够引发辐照交联和辐照降解作用,在较高束流量辐照下降解作用占据主导地位成为复合材料力、热性能退化的决定性因素。结论预期研究成果为CF/BMI复合材料在空间环境下的服役性能及寿命的评估与预测提供了必要的理论依据。     

Are calcareous soils in uplands less prone to damage from road salting than acidic soils?

Previous studies of upland roadside soils in Cumbria, that would normally be naturally acidic, have highlighted that (a) runoff from roads subjected to long-term road salting can dramatically raise soil pH down slope in upland areas; (b) the soil pH increase dramatically changes N cycling in soils down slope, increasing mineralisation of organic matter, ammonification, ammonium leaching down slope and nitrification and nitrate leaching; (c) the increase in nitrification substantially increases nitrate leaching to down-slope rivers, and this is readily detectable in field studies; and (d) loss of soil organic matter over decades of salting is so great that organic matter is no longer substantially solubilised by high salt concentrations found in soil solution below road drains. This paper tests and supports the hypothesis that such effects are minimal for more calcareous soil ecosystems. It examines the soil and soil solution chemistry on another Cumbrian upland highway, the A686 near Leadgate, Alston. Sodium % of soil CEC values for soil transects affected by spray containing road salt are similar at both the A6 and A686 sites. However, spatial trends in calcium, magnesium, ammonium, and nitrate concentrations as well as pH differ, as a direct result of the higher weathering rate of parent material and possibly also the presence of limestone walls above both spray-affected and control transects at the A686 site.     

Cycling Skill Inventory: Assessment of motor–tactical skills and safety motives

Abstract

Objective: It is well established within the traffic psychology literature that a distinction can be made between driving skill and driving style. The majority of self-report questionnaires have been developed for car drivers, whereas only limited knowledge exists on the riding skill and style of cyclists. Individual differences in cycling skills need to be understood in order to apply targeted interventions.

Methods: This study reports on a psychometric analysis of the Cycling Skill Inventory (CSI), a self-report questionnaire that asks cyclists to rate themselves from definitely weak to definitely strong on 17 items. Herein, we administered the CSI using an online crowdsourcing method, complemented with respondents who answered the questionnaire using paper and pencil (n?=?1,138 in total). Our analysis focuses on understanding the major sources of variance of the CSI and its correlates with gender, age, exposure, and self-reported accident involvement as a cyclist.

Results: The results showed that 2 components underlie the item data: Motor–tactical skills and safety motives. Correlational analyses indicated that participants with a higher safety motives score were involved in fewer self-reported cycling accidents in the past 3 years. The analysis also confirmed well-established gender differences, with male cyclists having lower safety motives but higher motor–tactical skills than female cyclists.

Conclusions: The nomological network of the CSI for cyclists is similar to that of the Driving Skill Inventory for car drivers. Safety motives are a predictor of self-reported accident involvement among cyclists.     

广东和海南红树林的生物地球化学特征

本文研究了广东和海南红树林的土壤,植物叶子和死地被物的化学成分以及它们之间的相互关系，并与相同地区的一些植物群落进行比较，从而探讨红树林的生物地球化学特征。结果表明，红树林的土壤和植物的某些化学成分含量较高，尤其是Na和Ca的含量较为突出。另外，虽然海岸带海水的pH＞8，土壤都呈酸性。红树林的养分利用率只有N较高，其余大多数元素都较低。红树林的生物吸收率和生物归还率通常也较低，但其大多数元素的生物分解率则较高。     

潮间带湿地碳循环及其环境控制机制研究进展

有高等植被覆盖的潮间带湿地（红树林沼泽、盐沼）植被生产力高,有机碳分解速率低,CH4排放较弱,碳沉积速度快,是单位面积碳封存速率最高的生态系统之一。作为全球“蓝色碳汇”的主要贡献者,潮间带湿地在减缓含碳温室气体排放,降低全球温室效应方面具有重要潜力。潮间带湿地大多地处经济发达和人口密集的河口海岸地区,近年来其碳汇功能受到了越来越多人为干扰的威胁,正在发生着的气候变化则更增加了这种碳汇功能的不确定性。在全球变化背景下,对潮间带湿地碳循环及其环境控制机制的深入了解可以帮助更好地管理这种具有重要碳减排潜力的生态系统。文章综述国内外的相关研究,分析了潮间带湿地碳循环的基本过程和环境影响因素,探讨了多种人为干扰和气候变化要素对潮间带湿地碳循环的影响。潮间带湿地碳循环的基本过程主要包括垂直方向土壤（水）-大气界面和植被-大气界面CO2、CH4交换和沉积过程驱动的碳封存,以及水平方向与近海的碳交换。潮间带湿地的碳循环主要受潮汐/流、光合有效辐射、温度、盐度、水位、植物群落特征等非生物和生物因素的影响。围垦、富营养化、放牧很可能削弱潮间带湿地的碳汇功能,而外来植物入侵却可能在一定程度上增加其碳汇潜能。海平面上升、气温升高会增加潮间带湿地碳汇功能的脆弱性,CO2浓度升高的作用依赖于优势植物群落的光合作用途径,而多种并存气候变化要素的作用则更为复杂。全球范围内大量潮间带湿地已经遭受破坏甚至丧失,水文调控是对受损潮间带湿地碳汇功能进行修复和重建的有效措施。未来的研究需要更好的理解多种并存气候变化要素,及人为干扰和气候变化同时存在对潮间带湿地碳循环的交互效应,利用过程模型预测不同人为干扰和气候变化情境下潮间带湿地碳收支变化规律,并完善受损潮间带湿地碳汇功能修复的基础理论和实施方法。     

Influences of sediment dessication on phosphorus transformations in an intertidal marsh: formation and release of phosphine

This study investigated the effects of sediment dewatering on the phosphorus transformations concerning about the production and emission of phosphine in the intertidal marsh of the Yangtze Estuary. The concentrations of matrix-bound phosphine ranged from 18.62-72.53 ng kg⁻¹ and 31.14-61.22 ng kg⁻¹ within the August and January exposure incubations, respectively. The responses of matrix-bound phosphine concentrations to sediment dessication demonstrate that the production (or accumulation) of matrix-bound phosphine significantly increased with water loss at the start of the emersion incubations. However, further dehydration inhibited the formation of matrix-bound phosphine in sediments. The significant correlations of matrix-bound phosphine with the organic-P bacteria abundance and alkaline phosphatase activities implicate that the production of matrix-bound phosphine within the dessication incubations was linked closely to the microbial decomposition of organic P. The emissions of phosphine generally decreased with sediment dewatering, with the fluxes of 7.51-96.73 ng m⁻² h⁻¹ and 5.34-77.74 ng m⁻² h⁻¹ over the exposure incubations of both August and January, respectively. Also, it is observed that the releases of phosphine during the entire exposure periods were affected not only by its production but also by sediment water and redox conditions.