铁路交通噪声对鸟类生态环境的影响预测评价

由于鸟类的听觉频率范围与人类不同,以往基于A计权声压级的噪声测量方法,用于鸟类声环境的监测评价并不准确。以广东省江门市新会区“小鸟天堂”风景名胜区为例,开展铁路交通噪声对鸟类生态环境的影响研究。首先,通过实地调查,对鸟类生态区的多个监测点进行声环境线性频谱测量;其次,根据新茂铁路新会段的规划布局,采用模式预测法计算铁路运行期间在监测点产生的交通噪声频谱,并与铁路运行前实地测量的现状频谱叠加;在此基础上,进一步探讨铁路交通噪声对鸟类生态区声环境的影响以及预防措施。研究结果表明,列车运行时在鸟类良好听觉频率范围的噪声增量可达10~30dB,将严重影响鸟类声环境;当采取全封闭声屏障防护措施之后,可有效降低“小鸟天堂”景区范围的噪声。     

Region-wide retreats from lower elevations of range-restricted birds across the Northern Andes

Local studies show upslope shifts in the distribution of tropical birds in response to warming temperatures. Unanswered is whether these upward shifts occur regionally across many species. We considered a nearly 2000-km length of the Northern Andes, where deforestation, temperature, and extreme weather events have increased during the past decades. Range-restricted bird species are particularly vulnerable to such events and occur in exceptionally high numbers in this region. Using abundant crowd-sourced data from the Cornell Lab of Ornithology database, eBird, and the Global Biodiversity Information Facility, we documented distributions of nearly 200 such species. We examined whether species shifted their elevational ranges over time by comparing observed versus expected occurrences below a low elevational threshold and above a high elevational threshold for 2 periods: before and after 2005. We predicted fewer observations at lower elevations (those below the threshold) and more at upper elevations (those above the threshold) after 2005. We also tested for deforestation effects at lower elevations within each species’ distribution ranges. We compared relative forest loss with the differences between observed and expected occurrences across the elevational range. Species’ retreats from lower elevations were ubiquitous and involved a 23–40% decline in prevalence at the lowest elevations. Increases at higher elevations were not consistent. The retreats occurred across a broad spectrum of species, from predominantly lowland to predominantly highland. Because deforestation showed no relationship with species retreats, we contend that a warming climate is the most parsimonious explanation for such shifts.     

化学分析方法校准曲线有关问题的探讨

校准曲线的线性范围为测定下限与测定上限之间的浓度范围,测定上限应尽可能扩大,但要保证校准曲线呈线性,同时,最高点分析后不会对分析系统造成污染物残留。通常应根据分析方法原理、仪器的特点和样品基质情况来确定校准方式。对于线性校准曲线,除了相关系数外,还要根据不同情况,对校准曲线进行检验。校准曲线的合格判定,除考虑相关系数外,还需要用校准曲线重新计算校准点,对于线性校准,所有校准点计算结果拟合值与实际值的相对误差应在±30%以内,对于非线性二阶校准曲线,应进行最大值与最小值检验。     

浆固碎石桩成桩注浆渗透影响分析

浆固碎石桩作为一种新型软土地基处理技术,其主要通过注浆改善桩体的加固效果,同时通过浆体渗透来改善桩周土体的物理力学性质,从而减小浆固碎石桩复合地基沉降。针对浆体对桩周土体的渗透作用,按照平面轴对称问题,推导出注浆渗透影响范围的计算方法和浆固区压缩模量计算公式,并通过室内模型试验研究,验证了浆固区压缩模量计算公式的正确性。随后,利用数值计算分析,对浆固区影响范围进行量化分析,并通过数值拟合得到了考虑注浆渗透影响的桩体等效半径计算公式。所得结果对工程设计具有重要的指导意义。