外源铅在西北干旱区绿洲灌淤土-小麦中的迁移及其生物效应

以干旱区绿洲灌淤土为供试土壤,采用盆栽模拟试验和室内分析研究了铅(Pb)对小麦生长的影响及其在小麦体内的迁移富集规律,以期为Pb污染土壤的管理提供一定的科学依据。结果表明：Pb在添加低质量分数下能促进小麦生长,但达到临界值150 mg kg-1后,就会出现明显的毒害作用。随着Pb添加质量分数的增加,各器官中Pb含量也呈增长趋势。小麦根对Pb的富集能力最强,籽粒对Pb的富集能力最弱。随着Pb添加质量分数的增加,土壤中可交换态Pb和碳酸盐结合态Pb所占比例呈增加趋势。在绿洲灌淤土—小麦系统中,可交换态Pb具有很大的生物有效性。     

不同阈值下土壤盐分的空间变异特征研究

指示克里格法(Indicator Kriging,IK)应用的关键是阈值的合理选择。本文以黄淮海平原盐渍土改良区典型县域禹城市为研究区域,在1.0 g kg-1、2.0 g kg-1、3.0 g kg-1等3个盐分阈值下,对0～20 cm耕地土壤盐分的变异函数、预测概率、预测概率空间分布的变化规律进行了研究。结果表明,(1)不同阈值下土壤盐分含量均具有中等强度的自相关性,随着阈值的减小,土壤盐分的空间结构性增强,变异函数的模型精度增大,因此从指示变异函数模型精度考虑,1.0 g kg-1盐分含量为研究区域盐渍化风险评价的最佳阈值;(2)土壤盐分的预测概率最大值和预测概率均值随盐分阈值的减小而增大,可为不同土壤盐渍化风险评价目标下的阈值选择提供参考;(3)不同阈值下土壤盐分的概率预测分布存在空间上的规律性与相似性,高概率区域主要集中在研究区域的西部,低概率区域主要集中在研究区域的东部。研究区域土壤盐分含量的概率分布与地形地貌特征和河流的分布状况有着密切的关系。     

用电导频散法研究Cl-、SO42-和H2PO4-阴离子与土壤的相互作用

本文介绍了采用电导频散装置测量分别含有10^-4mol/LHCl、5×10^-5mol/L H₂SO₄和10^-4mol/L H₃PO₄的黄棕壤、棕壤、黑土和砖红壤悬液(20-30g/kg)的电导频散曲线,频散曲线上均呈现频率范围相当宽的坪区,频散曲线的特性分析结果表明,黄棕壤和棕壤在3种酸溶液中的始散频率(0.6-1kHz)低于黑土悬液(16-28kHz),而砖红壤的始散频率最高(25-47kHz;Cl^-、SO₄^2-和H₂PO₄^-离子与4种土壤的相对亲合力(REC_1.5/REC_tp-1)顺序为Cl^- < SO₄^2- < H₂PO₄^-,在不同土壤之间的顺序则随酸溶液而异.     

湖南常德回维村的门槛分析与整治规划

基于对门槛理论的概述,应用门槛分析方法,针对我国第二大维吾尔族聚居地——湖南省常德市桃源县枫树乡回维村,分析该村在发展过程中的门槛限制因素,并立足于少数民族特色资源和优势,提出村庄整治规划的措施。     

基于JPEG-LS预测的无损信息隐藏算法研究

对Thodi预测算法进行了改进,并且通过仿真实验,有选择地确定了预测误差阈值和阈值参数值.经初步测试,证明了在较大嵌入量的前提下,较好地提高了信噪比,并能够无损地提取隐藏信息.     

放牧高寒嵩草草甸的稳定性及自我维持机制

以空间代时间,在＂三江源＂和中国科学院海北高寒草甸生态系统研究站地区,将处于不同退化阶段的高寒嵩草草甸作为研究对象,进行了其植物群落、地表状况、草毡表层厚度、根土比和水分渗透速率的演替过程与规律研究,以明晰放牧高寒嵩草草甸退化过程中其系统稳定性及自我维持机制。结果表明,高寒嵩草草甸虽然结构简单,但在长期适应寒冷气候进化过程中形成了低矮化、细绒化和草毡表层加厚、极度发育等一系列特殊的稳定性维持机制,可以承受一定范围内的人为干扰和气候波动,具有较高的系统稳定性与自我调控能力,但系统遭到破坏后的恢复能力极差。今日高寒草甸的大面积退化,是人类所赋加于草地的承载力远超过其承载力阈值而导致系统稳定性崩溃的结果。     

农田土壤中邻苯二甲酸酯临界浓度的研究

[目的]为完善土壤有机污染物质量标准。[方法]采用制定土壤质量指导值/标准通用的暴露风险评价方法,对农田土壤中邻苯二甲酸酯的临界浓度进行初步的推算。[结果]DBP、DEHP、DEP和BBP 4种邻苯二甲酸酯的临界浓度分别为250、50、2000、500 mg/kg。[结论]利用暴露风险评价模型推算的土壤邻苯二甲酸酯临界浓度远低于我国工业企业土壤环境质量风险评价基准中的相应污染物标准,但远高于美国的土壤标准。这可能与模型参数的取值和邻苯二甲酸酯的参考剂量有很大关系。     

Do indicators of nitrogen retention and leaching differ between coniferous and broadleaved forests in Denmark?

The area of broadleaved forests is projected to increase in Denmark as well as in the rest of Europe. However, studies of the N leaching response to elevated N deposition have focused on coniferous stands and considerable uncertainty still remains on whether broadleaved and coniferous forests respond differently to elevated N. We studied N input–output relations for eight stands intensively monitored during 2002–2005 and literature data for 37 additional stands which together formed a comprehensive dataset on Danish forests including 26 broadleaved stands and 19 coniferous stands. Nitrate leaching was significantly higher in first generation stands on former arable land with mineral soil C/N ratios 10–15, but both low and high rates were observed independent of the N input. A net N loss was observed in some of these stands even though they are in the aggrading phase and accumulate N in the biomass. Broadleaved stands had significantly lower throughfall N deposition than coniferous stands and this seems to be the main process where forest type exerts an influence on the N cycle. Lower soil C/N ratios offset the effect of throughfall N deposition and thus N leaching did not differ between the two forest types. The best regression models for prediction of nitrate leaching included throughfall N deposition and C/N ratio, but only a minor part of the variability was explained. The C/N ratio of the upper mineral soil was more generally applicable than that of the organic layer. The N retention of the soil was reasonably well predicted above a C/N ratio of 25, but below this threshold the importance is not known. We suggest focusing future efforts on quantifying the relative retention functions (sink strength) of the vegetation and the soil organic matter to improve the predictions of N retention and N leaching.     

Field Ovservation of Threshold Frictional Velocity on Different Types of Famland

To quantize the difficulty level of dust production on the surface of different types of farmland,the Marticorena threshold frictional velocity pattern was used in this study to simulate the dust threshold frictional velocity.The results showed that the dust threshold frictional velocity of desertification farmland was 7.39cm/s,while it was 29.05 cm/s after the wheat harvested and the farmland ploughed; the turning green period was 46.85 cm/s; shooting period was 98.93 cm/s,the uncovered and the establishment period of fruit tree farmland was 26.0 and 139.15 cm/s.It was concluded that,bare desertification farmland could be changed into source of dust release easier.     

YM型小麦雄性不育系KTM3314A的温敏特性

为了明确YM型小麦温敏不育系KTM3314A的育性转换特性,以1B/1R类型K型小麦雄性不育系K3314A和YM型小麦雄性不育系KTM3314A为试验材料,进行分期播种(秋播、春播)和剪穂再生试验,以K3314A为对照,比较不同播期及再生分蘖穗的自交结实率,并与同期的温度、湿度等气象数据对照,以确定KTM3314A的温度敏感期和临界温度。结果表明,K3314A秋播、春播及再生分蘖穗皆完全雄性不育,KTM3314A秋播完全雄性不育,春播及再生分蘖穗育性部分恢复,育性转换的温度敏感期在孕穗前后5 d,临界温度为18.14℃,表明KTM3314A具有温度敏感特性。