华北农牧交错带夏季降水变率及其与前期下垫面热力状况的关系

华北农牧交错带夏季降水有很大的变率 ,频繁的干旱对农牧业生产有严重影响。论文分析了1880年以来的夏季降水变化特征 ,近百年来农牧交错带夏季降水有明显的阶段性。功率谱分析显示有35年左右的周期。年代际尺度的波动是干湿变化的重要背景。以250mm等雨量线表示的农牧交错带南北位置也有明显的年际和年代际的变化 ,在1978年以前和以后的两段时期 ,平均位置有显著的差别 ,前后平均有大约1.5个纬度的变化。农牧交错带夏季降水与前期春季亚欧地区大范围的温度异常有较好的关系。印度和巴基斯坦及相邻印度洋地区是显著的正相关区 ;亚洲西部的内陆地区是显著的负相关区。这两个地区春季的温度能解释农牧交错带夏季降水方差的15 %左右。     

New remains of the enigmatic cetartiodactyl Bugtitherium grandincisivum Pilgrim, 1908, from the upper Oligocene of the Bugti Hills (Balochistan, Pakistan)

Newly discovered fossil material of the enigmatic cetartiodactyl Bugtitherium grandincisivum from the upper Oligocene of the Bugti Member of the Chitarwata Formation in the Bugti Hills (Balochistan, Pakistan) is reported. These new specimens consist of two fragmentary muzzles (one preserving the first incisors and belonging to a juvenile) and a fragmentary right mandible with m3. The morphologies of the anterior dentition and m3 provided by these new specimens confirm the validity of the genus Bugtitherium and advocate probable anthracotheriid affinity for the genus rather than entelodontid or suoid affinities, but do not definitively close the debate about Bugtitherium’s familial affinities within Cetartiodactyla. Although still poorly documented, this large-sized anthracotheriid-like cetartiodactyl is a possible key form for understanding the early evolution of hippos, and, in turn, the ancestry of whales, because of both its morphological similarities with hippos and primitive Paleogene whales and its Tethysian distribution.     

Effects of Urbanization on Occupancy of Stream Salamanders

Abstract: Urban development is the most common form of land conversion in the United States. Using a before–after control‐impact study design, we investigated the effects of urbanization on larval and adult stages of southern two‐lined salamanders (Eurycea cirrigera) and northern dusky salamanders (Desmognathus fuscus). Over 5 years, we estimated changes in occupancy and probabilities of colonization and survival in 13 stream catchments after urbanization and in 17 catchments that were not urbanized. We also examined effects of proportion of urbanized area in a catchment and distance of the salamander population to the nearest stream on probabilities of colonization and survival. Before urbanization, adult and larval stages of the two salamander species occupied nearly all surveyed streams, with occupancy estimates ranging from 1.0 to 0.78. Four years after urbanization mean occupancy of larval and adult two‐lined salamanders had decreased from 0.87 and 0.78 to 0.57 and 0.39, respectively. Estimates of mean occupancy of larval northern dusky salamanders decreased from 1.0 to 0.57 in urban streams 4 years after urbanization; however, adult northern dusky salamander occupancy remained close to 1.0 in urban streams over 5 years. Occupancy estimates in control streams were similar for each species and stage over 5 years. Urbanization was associated with decreases in survival probabilities of adult and larval two‐lined salamanders and decreases in colonization probabilities of larval dusky salamanders. Nevertheless, proportion of impervious surface and distance to nearest stream had little effect on probabilities of survival and colonization. Our results imply that in the evaluation of the effects of urbanization on species, such as amphibians, with complex life cycles, consideration of the effects of urbanization on both adult and larval stages is required.     

Assessment of water quality of Manchar Lake in Sindh (Pakistan)

Manchar Lake is the largest natural freshwater lake in Pakistan. The Lake has received less fresh water in past few years. In addition, drainage water is being discharged in the Lake through Main Nara Valley Drain (MNVD) since many years. Consequently, concern has grown regarding the water quality of the Lake. The aim of this study was to assess the water quality of Manchar Lake and MNVD and the objectives were to determine physiochemical properties and the concentrations of common cations and anions as well as seven trace metals i.e. Cu, Ni, Zn, Co, Fe, Pb and Cd. The concentration of the trace metals were determined by simultaneous preconcentration and solvent extraction using flame atomic absorption spectrometer. Results of physicochemical parameters of Manchar Lake water samples showed mean pH 8.4 (±0.2), conductivity 2,310.3 (±581.3) μS cm⁻¹ and hardness (as CaCO₃) 213.1 (±62.3) mg l⁻¹. Mean concentrations of cations and anions were Na 521.5 (±49.7), Cl⁻ 413.6 (±225.7), Ca 70.7 (±12.9), Mg 56.2 (±28.9), K 17.6 (±6.5), 0.34 (±0.2) and 0.02 (±0.01) mg l⁻¹. Mean concentrations of trace metals were Zn 15.7 (±1), Fe 12 (±3.5), Pb 9 (±2.7), Cu 8.9 (±7.7), Ni 4.3 (±3.4), Co 4 (±3.4) and Cd 1.1 (±1) μg l⁻¹. MNVD water samples showed mean pH 8.9 (±0.8), conductivity 1,735.7 (±567.8) μS cm⁻¹ and hardness (as CaCO₃) 184.8 (±32.4) mg l⁻¹. In MNWD, the mean concentrations of cations and anions were Na 482.7 (±11.7), Cl⁻ 395.7 (±271.5), Ca 79.1 (±23.5), Mg 54.2 (±28.1), K 26.2 (±21.3), NO⁻³ 0.5 (±0.3) and 0.1 (±0.1) mg l⁻¹. Mean concentrations of trace metals observed in MNWD water were Fe 14.9(±3.5), Cd 8.3 (±9.4), Pb 6.9 (±2.4), Cu 6.6 (±3.1), Zn 6.2 (±1.8), Co 4.5 (±2.7), and Ni 3.5 (±2.9) μg l⁻¹. The pH of both Manchar Lake and MNVD waters and concentration of Pb in Manchar Lake and concentration of Cd in MNVD water were higher than the World Health Organisation’s guideline values for the drinking water quality. The water quality of Manchar Lake was found degraded.     

From socioeconomic disparity to environmental injustice: the relationship between housing unit density and community green space in a medium city in Pakistan

Rapid urbanisation, lack of proactive planning and improper allocation of resources may result in socio-economic disparity among and within cities, causing social unrest and environmental injustice in the neighbourhoods. This study aims to examine whether the planning standards for housing schemes in Pakistan are able to maintain equitable access to green spaces within the cities. Ten residential sites in Sheikhupura city with different housing unit sizes and densities were selected for the study. The supply of urban green infrastructure in housing scheme has been assessed: (i) by comparing the percentage of green spaces, including community parks and open spaces and street landscape; and (ii) by calculating per dwelling unit and per capita share of green spaces. These indicators have been studied against the housing density and population density of the schemes by applying correlation and linear regression models. The results show that all the housing schemes plans provide for similar amounts of green space as a percentage of total area. The per capita share of green spaces is very low in high-density areas, but interestingly, the street landscape has a higher potential to contribute to the overall landscape in high-density neighbourhoods, compensating for low per capita green space. Housing unit density and population density must be incorporated in planning standards so planners can effectively devise a mix of community parks, street landscape and private green spaces to help maintain per capita green spaces, and hence environmental resource equality in different parts of the city.     

陕北长城沿线沙质荒漠化遥感研究

采用1975年MSS卫星图像、2000年ETM卫星图像为遥感信息源,通过建立科学的沙质荒漠化土地分类体系,并结合地理信息系统方法,对位于农牧交错带生态环境脆弱的陕北长城沿线沙质荒漠化进行了现状及动态变化分析,结果表明,经过20多年来沙质荒漠化防治,现代沙质荒漠化过程得到了明显的逆转,25年间,沙质荒漠化土地面积减少了195.18km²,逆转区的面积比发展区的面积大1280.48km²,为该区能源化工基地的建设提供了良好的生态环境,但是目前该区的沙质荒漠化土地强度依然较大,危害较大的极重度和重度沙质荒漠化土地占到总沙质荒漠化土地面积的35.64%,同时煤炭、油气资源的开发对沙质荒漠化的负面影响具有潜在性和长期性,因此,建立合理的资源开发和环境保护体系具有重要的生态和社会意义。     

南京北郊BTESX特征及健康风险评估

采用AMA GC5000BTX监测2014年1月~2016年12月南京北郊大气中苯、甲苯、乙苯、间/对-二甲苯、邻-二甲苯和苯乙烯（BTESX）的体积分数,分析了BTESX体积分数的变化特征以及气象要素对其的影响,并使用特征比值法（T/B）对BTESX的来源进行了定性分析,最后利用EPA的人体暴露分析评价方法对BTESX健康风险进行评估.结果表明,在观测期间,φ（BTESX）平均值为（7.28±6.63）×10^-9,其中φ（苯）最高,为（2.45±3.91）×10^-9,其他物种体积分数由大到小为：甲苯>乙苯>间/对-二甲苯>邻-二甲苯>苯乙烯,分别为：（2.41±2.61）×10^-9、（1.37±1.28）×10^-9、（0.51±0.48）×10^-9、（0.30±0.36）×10^-9和（0.22±0.42）×10^-9.由于存在稳定的芳烃源,BTESX体积分数的月变化和季节变化均不如其他物种（NO_x、CO、SO₂和PM_2.5等）明显.同时,BTESX及其他污染物的"周末效应"不显著.BTESX体积分数很大程度受到来自东北方向化工等企业以及交通主干道的污染物短距离输送的影响,导致BTESX体积分数在东北方向上较大.BTESX体积分数受到相对湿度和温度的共同影响,其高值区主要位于30%~70%相对湿度范围内,在该相对湿度范围内,温度越高,BTESX体积分数高值区域范围也越大.BTESX在不同季节的HI （危害指数）处于EPA认定的安全范围内,而R（苯致癌风险）值则高于EPA规定的安全阈值,同时HI和R值在夏季较高,因此需要高度重视.     

轨道尺度下东亚夏季风降水的北方主导演变模态

众多古气候记录的分析表明：轨道尺度气候变化下我国北方地区的季风降水变化显著,该现象的理解对于深入认识东亚夏季风降水的长期演变模态具有重要意义。本文基于瞬变古气候模拟的分析发现：在轨道尺度气候变化下,东亚夏季风降水的变化中心位于季风区北边界附近的半干旱区,是季风环流整体性演变及季风区北边界摆动的综合作用结果。东亚夏季风降水的轨道尺度演变模态与古气候记录的指示相一致,但与当前观测记录给出的以年际尺度变化为主的模态显著不同,说明东亚夏季风降水对气候变化的响应与气候变化的时间尺度有关。进一步的分析表明：轨道尺度气候变化下东亚夏季风北方降水的响应幅度取决于气候变化的驱动因素,其中轨道辐射的影响最为显著。     

Spatial and temporal dynamics of phytoplankton and bacterioplankton biomass in Sanya Bay, northern South China Sea

The composition of phytoplankton and the dynamics of phytoplankton and bacterioplankton biomass (PB and BB, respectively) of Sanya Bay, South China Sea, were determined. A total of 168 species (67 genera) phytoplankton were identified, including Bacillariophyta (diatom, 128 species), Pyrrophyta (35 species), Cyanophyta (3 species), and Chrysophyta (2 species). Annual average abundance of phytoplankton was 1.2 × 107 cells/m3, with the highest abundance in autumn, and the lowest in summer. Annual average dive...     

利用蒸散比和气温模拟藏北高寒草甸的光能利用效率

光能利用效率(light use efficiency,LUE)是指初级生产力与植被冠层吸收的光合有效辐射(absorbed photosynthetically active radiation,APAR)之比,对LUE的准确定量化模拟是定量化模拟初级生产力的基础。研究利用一个基于通量观测的LUE模型(EC-LUE)模拟了2004-2005年藏北高寒草甸的LUE,该模型的参数只有蒸散比(Evaporative Fraction,EF)和气温(air temperature,T_a),EF和T_a分别为最大光能利用效率(maximum light use efficiency,LUE_max)的水分和温度胁迫因子,在研究中LUE_max取0.85 g C/MJ。EF和T_a对LUE_max的胁迫作用存在两种方式:连乘方式和最小限制因子方式,这两种方式模拟的光能利用效率分别记为LUE_multipEC和LUE_minEC,并与通量观测数据估算的LUE(LUE_EC)进行了比较。结果表明,LUE_minEC显著高估了LUE_EC,而LUE_EC和LUE_{multipEC差异不显著;LUEmultipEC和LUEminEC分别解释了89%以上LUEEC的季节变化;EF显著地解释了土壤表层含水量、 比湿,且在一定程度上解释了相对湿度的季节变化;相对于水分胁迫因子,温度胁迫因子更能够解释LUEEC的季节变化。因此,EC-LUE模型可以定量化高寒草甸LUE的季节变化,同时EF可以定量化高寒草甸生态系统水分状况的季节变化。}