基于商值法的镧水生态风险评价方法研究及应用

随着我国稀土资源开发和利用，稀土元素对水生生态环境的影响及其生态风险越来越受关注。本文以稀土镧的通用敏感生物急性半致死/效应浓度(half lethal/effect concentration, L(E)C_(50))和慢性无观察效应浓度(no observed effect concentration, NOEC)数据，分别采用评价因子法和物种敏感度分布法(species sensitivity distribution, SSD)推导计算了镧的预测无效应浓度(predicted no effect concentration, PNEC),比较不同数据类型和计算方法的结果差异及不确定性，并以四川安宁河为例进行了水生态风险表征。采用评价因子法推导的急性和慢性PNEC分别为1.180μg·L^(-1)和4.000μg·L(-1)和4.000μg·L^(-1)。由急性数据拟合SSD曲线推导的PNEC为42.770μg·L(-1)。由急性数据拟合SSD曲线推导的PNEC为42.770μg·L^(-1),通过急慢性比(acute to chronic ratio, ACR)转换的PNEC为2.032μg·L(-1),通过急慢性比(acute to chronic ratio, ACR)转换的PNEC为2.032μg·L^(-1)。在慢性数据缺乏的情况下，ACR-SSD是相对可行的方法。安宁河镧的水生态风险评价结果表明，所有调查断面均处于中等以上生态风险，其稀土污染问题应引起重视。     

Age and spatial distribution of the world's oldest trees

Extremely old trees have important roles in providing insights about historical climatic events and supporting cultural values, yet there has been limited work on their global distribution and conservation. We extracted information on 197,855 tree cores from 4854 sites and combined it with other tree age (e.g., the OLDLIST) data from a further 156 sites to determine the age of the world's oldest trees and quantify the factors influencing their global distribution. We found that extremely old trees >1000 years were rare. Among 30 individual trees that exceeded 2000 years old, 27 occurred in high mountains. We modeled maximum tree age with climatic, soil topographic, and anthropogenic variables, and our regression models demonstrated that elevation, human population density, soil carbon content, and mean annual temperature were key determinants of the distribution of the world's oldest trees. Specifically, our model predicted that many of the oldest trees will occur in high-elevation, cold, and arid mountains with limited human disturbance. This pattern was markedly different from that of the tallest trees, which were more likely to occur in relatively more mesic and productive locations. Global warming and expansion of human activities may induce rapid population declines of extremely old trees. New strategies, including targeted establishment of conservation reserves in remote regions, especially those in western parts of China and the United States, are required to protect these trees.     

沿海设施环境适应性试验和评价方法研究进展

概述了沿海设施所服役的腐蚀环境分类，主要分为海洋大气、浪花飞溅区及海水浸泡区，并对其暴露于大气和不同海洋环境位置的环境适应性试验评估方法进行了系统的总结分析。海洋大气环境模拟采用干湿交替加速腐蚀法，或建立户外大气暴露试验台开展试验；海水飞溅区试验通过实验室建海水冲刷试验装置进行模拟试验，或在实际环境中建立腐蚀试验中心开展试验；海水浸泡环境模拟通过海洋工程深水试验池开展试验。本研究对于开展海洋环境钢结构设施的防护性能考核评估具有重要意义，对沿海设施的环境适应评估方法发展具有指导意义。     

基于密度–距离空间的红外引信抗噪声方法研究

目的 通过简易的图像处理和目标检测方法，提高红外引信在复杂环境下的抗干扰能力。方法 分析红外引信在复杂背景中的噪声类别，采用“密度–距离”空间方法与像素生长方法进行预处理和目标检测，赋予像素2种属性，并进行量化分析，确定灰度平坦区域中的红外候选目标，并通过像素生长方法筛选候选目标中的真实目标。结果 计算在不同信噪比环境下算法的抗噪声干扰能力，当红外图像的SNR值在44.1~45.4时，算法检测效果理想。结论 红外引信探测过程中的复杂背景和随机噪声都会降低图像质量，考虑到红外目标所占像素数少，极易受噪声影响，需要运用自适应简易算法提高检测准确性。该算法有良好的实时性和抗干扰能力，为红外引信在目标检测中的环境适应性提供了理论依据。