Modelling nitrogen fluxes at the landscape scale

The distribution and impacts of different nitrogen pollutants are inextricably linked. To understand the problem fully, the interactions between the different pollutants need to be taken into account. This is particularly important when it comes to abatement techniques, since measures to reduce emissions of one nitrogen pollutant can often lead to an increase in another. This project represents a step towards greater understanding of these issues by linking together new and existing nitrogen flux models into a larger framework. The modelling framework has been constructed and some of the nitrogen flows between fields, farms and the atmosphere have been modelled for a UK study area for typical farm management scenarios.     

Rapid amino acid cycling in arctic and antarctic soils

Amino acids constitute one of the largest inputs of organic nitrogen (N) to most polar soils and have been hypothesized to be important in regulating vegetational succession and productivity in Arctic ecosystems. Our understanding of amino acid cycling in these soils, however, is poor. The aim of this study was to investigate the size and rate of turnover of the amino acid pool in a range of Arctic and Antarctic soils. Our results indicate that in polar soils with either high or low ornithogenic inputs the amino acid pool is small in comparison to the inorganic N pool (NO^–₃ and NH⁺₄). The free amino acid pool constituted only a small proportion of the total dissolved organic nitrogen (DON) pool in these soils. Here we show that these low concentrations may be due to rapid use by the soil microbial community in both Arctic and Antarctic soils. The turnover of the amino acid pool in soil was extremely rapid, with a half-life ranging from 2 to 24 h, indicating that this N pool can be turned over many hundred times each summer when polar soils are frequently unfrozen. The implications of amino acids in N cycling and plant and microbial nutrition are discussed.     

Applying metabolic fingerprinting to ecology: The use of Fourier-transform infrared spectroscopy for the rapid screening of plant responses to N deposition

The potential for metabolic fingerprinting via Fourier-transform infrared (FT-IR) spectroscopy to provide a novel approach for the detection of plant biochemical responses to N deposition is examined. An example of spectral analysis using shoot samples taken from an open top chamber (OTC) experiment simulating wet ammonium deposition is given. Sample preparation involved oven drying and homogenisation via mill grinding. Slurries of a consistent dilution were then prepared prior to FT-IR analysis. Spectra from control, 8 and 16 kg N ha^–1 yr^–1 treatments were then subjected to cross-validated discriminant function analysis. Ordination diagrams showed clear separation between the three N treatments examined. The potential for using Calluna vulgaris (L.) Hull as a bioindicator of N deposition is further evident from these results. The results also clearly demonstrate the power of FT-IR in discriminating between subtle phenotypic alterations in overall plant biochemistry as affected by ammonium pollution.     

旧路改造工程路堤稳定性安全监测方案设计

本文从旧路改造工程的特点出发,通过室内实验获取土力学参数并对沉降量进行预测计算.利用沉降仪、测斜管、孔隙水压力计、土压力盒等多种测试仪器,选取有代表性的观测断面,对经过土工格栅加筋处理的软土地基进行了高路堤施工期间的沉降与稳定观测,并提出适合工程特点的控制标准.从而达到控制路堤稳定、检验填筑质量、控制差异沉降、为路面施工提供技术支持的目的.     

液固比对含重金属水泥熟料制品中重金属释放的影响

通过模拟煅烧试验制取水泥熟料,参照JGJ 55-2000（《普通混凝土配比设计规程》）制取混凝土样品,参考SR003.1和NEN 7375浸出试验,分别研究液固比对粒状及块状混凝土样品中重金属（Cr、Ni和As）释放的影响。结果表明,在不同液固比条件下粒状混凝土中的重金属浸出浓度为Cr>Ni>As,Cr、As浸出浓度基本保持不变,分别为2 500 μg/L左右和5～6 μg/L,Ni在液固比（L∶S）<6时,浸出浓度随着液固比的增加而降低,在L∶S>6时,浸出浓度较稳定,为35.7～41.5 μg/L;浸出量均随着液固比的增加而增大。液固比（L∶S）<10时,块状混凝土中重金属累积释放量及扩散系数均随液固比的增加而增大,当L∶S>10时两者基本保持不变。     

水中安替比林的紫外光降解研究

以波长为254 nm的紫外杀菌灯为光源,研究了水溶液中消炎镇痛药物安替比林（PZ）的光降解行为;考察了初始pH值及水中其他物质对PZ光降解的影响,探讨了PZ光解机制,并分析其降解产物及光解途径。结果表明,安替比林的光降解遵循拟一级反应动力学规律,pH值变化对光解速率基本没有影响。安替比林直接光降解占主导作用,活性氧类物种（ROS）对安替比林间接光解基本没有贡献。腐殖酸对安替比林光降解有抑制作用,而NO^-₃,HCO^-₃,Cl^-对安替比林光降解没有明显作用。GC-MS分析表明安替比林在紫外辐射下生成甲酰胺,乙酰胺,2-羟基吲哚-3-酮,2,4（1氢,3甲基）-喹唑啉二酮,1-甲基-2-羟基苯并咪唑,2-羟基苯并恶唑等一系列具有安替比林母体苯环结构的化合物,表明安替比林侧链上N—N键断裂导致其最终降解。     

四川青衣江上游若壁小沟泥石流及其防治对策

若壁小沟为四川青衣江上游左岸的一级支沟,该沟处于深切割高山峡谷区,地形坡度陡,构造发育,岩石破碎,加之较为丰富的降雨,使该沟具备泥石流暴发的条件。该沟如果暴发泥石流,将对某电站拟建厂房产生威胁。该沟泥石流具有成灾快、危害严重、松散固体物质以坡面崩塌补给为主、活动频率中等等特征。通过野外考察和取样分析,该沟泥石流的性质和类型为中频率—中~大规模—低~高粘度泥石质泥石流。分析预测了该沟泥石流在强烈地震条件下、近期出现不同频率暴雨情况下及人类活动影响下的发展趋势。在此基础上,提出了该沟泥石流减灾工程规划方案。     

东北地区降水年内分配的不均匀性

利用东北地区93个台站1961-2005年的逐日降水资料,通过降水集中度和降水集中期,讨论了该地区降水的年内分配不均匀分布特征.结果表明,东北地区的降水集中度自东南向西北逐渐递减;集中期具有南北高中问低的变化特点.从长期趋势上看,降水集中度的减小趋势显著,在该地区的东北部和西北部各有一个趋势明显的区域(通过0.05的显著性检验),但集中期的减小趋势不显著,只有2个台站通过显著性检验.年降水量与降水集中度和降水集中期的相关系数表明:东北地区年降水量与降水集中度呈显著的正相关,即年降水量越多(少)的地区,年内降水越集中(均匀);年降水量与降水集中期的关系并不显著.     

环境污染事故风险预测评估模式研究

从环境风险到环境污染事故演变的一般规律入手,提出了环境污染事故风险预测评估模式,为环境污染事故风险评估、预防与应急响应提供科学手段。环境污染事故风险预测评估模式的提出,一方面丰富和发展了环境安全与应急响应理论;另一方面,对公共安全、企业安全管理与应急响应等工作具有一定指导意义。     

人工神经网络在预测深基坑周边地表沉降变形中的应用研究

深基坑开挖引起的周边地表变形预测是一个复杂非线性问题,引起地表沉降的影响因素很多,各因素之间呈高度的非线性关系。传统的基坑用边地表沉降变形预测方法存在着一定的局限性,其预测精度有待提高,而人工神经网络是一种多元非线性动力学系统,可以灵活方便地对多成因的复杂未知系统进行高度建模,实现全面考虑各种主要影响因素的深基坑周边地表沉降变形预测。本文介绍了误差反向传播(BP)网络模型的结构、学习过程及其算法的改进,径向基函数(RBF)网络模型的结构及其学习过程;分析了影响深基坑开挖周边土体沉降变形的主要影响因素;以25个基坑工程的地表沉降实测资料为训练样本,建立了11个输入影响因素的BP神经网络模型和RBF神经网络模型,通过对样本的学习训练过程及对5个检验样本的预测精度,说明了人工神经网络用于预测基坑周边地表沉降的可行性和准确性。