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。     

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.     

浅谈转基因产品阈值管理

"阈值管理"是指对所有认为有风险的事物(如混杂率、异交率、阳性率、致死率、危害率等)给出一个容许的"度",并以这个"度"为依据进行管理。实施阈值管理是保障生物安全并推动转基因技术健康发展的需要。文章分析了阈值的含义、设置原则以及当前阈值管理存在的问题和发展趋势。     

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.     

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。     

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.     

假眼小绿叶蝉防治指标的研究

利用网罩法测定了假眼小绿叶蝉不同虫口密度对茶鲜叶产量及受害指数的影响。在此基础上,建立了不同虫口密度与茶鲜叶经济损失率线性回归方程。根据目前茶叶的生产情况,制定了绿茶和乌龙茶不同茶区、茶季、茶鲜叶价格水平下假眼小绿叶蝉相应的防治指标。     

KM数学模型在预测、控制森林传染病中的新应用

采用传染病数学模型对我国松林松材线虫病疫情进行模拟,针对森林染病的特点,通过对数学模型阈值的分析研究,得出对染病类松树采取隔离措施是控制疫情发展的一种方法,但实施起来并非易事,因而本文提出了清除染病松树的切实可行措施,详细分析了移除倍率与染病松树总量最大值之间的关系,并对采取清除措施后疫情的发展进行了预测,提出了控制疫情发展的条件.     

西苕溪流域主要经济林土壤磷素流失风险研究

经济林土壤磷素积累与潜在流失风险的研究对流域内磷素管理和面源污染控制十分必要.通过采样调查和室内分析研究了西苕溪流域主要经济林土壤测试磷的状况及磷素流失的潜在风险,调查采集了西苕溪流域安吉段主要经济林(毛竹、白茶、板栗)土壤样品105个,探讨了土壤理化性质对土壤磷素流失的影响以及土壤有效磷的控制阈值.结果表明,土壤水溶...     

葡萄日灼病阈值温度及主要影响因子分析

 以8年生红地球葡萄为试材,从诱发葡萄果实日灼病发生的阈值温度（临界果面温度）研究入手,探索气温、光照、风速等对果面温度的影响。结果表明：果面高温是果实发生日灼的直接原因。在‘红地球’葡萄果实的快速生长期测得日灼病发生的阈值温度为42.0～42.8℃（平均值42.3℃）;遮阴下的果实突然暴露在阳光下,12min后果面温度可达到最大值;强烈的光照可产生较高的气温及较高的果面温度,是日灼病发生的最重要影响因素。在夏季晴天无风的中午,每1万lx的光照强度可使果面温度增高1℃左右;无风时果面温度显著高于风速1.5m﹒s^-1以上时。在3.0m﹒s^-1风速下6min内可使果面温度降至最低;在相同的光温条件下,较高的空气湿度更利于日灼的发生。