乌鲁木齐市近几年大气颗粒物中重金属的浓度特征

采用重量法对2014年、2015年、2017年采暖期乌鲁木齐市新疆农业大学大气颗粒物TSP、PM₁₀、PM_2.5进行采集,使用TAS-990型火焰原子吸收分光光度计、PF3型原子荧光光谱仪、石墨炉原子吸收分光光度计测定颗粒物中5种重金属元素的质量浓度,利用富集因子法分析重金属元素的富集程度及来源。结果表明：该采样点采暖期大气颗粒物TSP、PM₁₀的质量浓度在近几年均呈现出下降趋势,PM_2.5的质量浓度变化趋势为：2017年＞2015年＞2014年;重金属元素As的质量浓度在不同粒径大气颗粒物中均为最高值,且采暖期大气颗粒物中除Cr以外的重金属含量、重金属元素的富集程度近几年均呈现明显的下降趋势;重金属As、Cr、Zn、Hg元素更易富集于细颗粒物中。     

南极春季中山站地区大气臭氧和NO2的变化特性

利用可见／紫外差分吸收光谱学方法，在１９９１年南极臭氧洞期间对中山站地区的大气臭氧和ＮＯ２含量进行了测量。分析结果指出，对中山站地区面言，１９９１年大气臭氧含量的迅速减少开始于８月中旬，到１０月３日达最低值，并很于１０月７日恢复到正常值。     

乌鲁木齐近30a大气稳定度和混合层高度变化特征及与空气污染的关系

基于1979 - 2008年乌鲁木齐1天4个时次的地面常规气象观测资料,运用Pasquill -Tumer稳定度分类方法和修正的罗氏法计算得出了乌鲁木齐市近30 a大气稳定度和大气混合层高度随时间序列的变化特征,分析了2001-2008年混合层高度和稳定度与空气污染的关系.结果表明:近30 a乌鲁木齐大气混合层高度随时...     

半干旱地区大气颗粒物浓度及粒径谱特征的观测研究

采用兰州大学半干旱气候和环境观测站（SACOL）2007年11月1日至2008年10月31日的APS-3321粒径谱仪的连续观测资料,对该地区大气颗粒物的浓度变化和粒径分布特征进行分析研究。结果表明,该地区颗粒物浓度年变化呈单峰值型,无论是数浓度还是质量浓度峰值均出现在12月,数浓度6月最低,质量浓度9月最低;和其他地区相比,无论数浓度还是质量浓度,均低于污染较严重的城市,但高于内陆清洁地区。数浓度和质量浓度平均日变化均呈单峰值型,都在上午11：00BST左右达到峰值,下午18:00BST左右达到谷值,但质量浓度峰值出现时间随季节而有所差异。颗粒物浓度的年变化和背景风场主导风向的年际变化有一定关系,而局地垂直风速及水平风向的昼夜转换对颗粒物浓度的日变化有较大的影响。数浓度粒径谱分布特征呈单峰值型,主要集中在0.673 μm左右;质量浓度粒径谱分布特征呈双峰值型,第一个峰值出现在0.777 μm左右,第二个峰值出现在5.048 μm左右。降水对大于1 μm的粒子的去除效果非常明显。当沙尘天气发生时,数浓度和质量浓度与背景天气条件下相比增大了22%和127%。     

1960～2017年华北地区气候生长季变化特征及成因分析

基于华北地区1960~2017年逐日气温数据,运用Mann-Kendall非参数检验、Morlet小波分析和R/S分析等方法,分析了华北地区气候生长季指标生长季开始（GSS）、生长季结束（GSE）、生长季长度（GSL）、生长季内≥10℃活动积温（AT10）及其对应的天数（DT10）的时空变化特征及其影响因素。结果表明:① 华北地区GSS呈显著的提前趋势,变化速率为-2.43 d/10a,GSL呈现出明显延长,AT10和DT10表现为显著增加趋势,变化速率分别为2.95 d/10 a、67.14℃/10a和2.31 d/10a,GSE变化趋势不明显。近60 a来华北地区GSL的延长主要归因于GSS的明显提前。② 生长季指标变化趋势在空间上存在明显差异,其中GSS与GSL,AT10与DT10变化趋势的空间分布格局较为相似。③ 生长季指标普遍在20世纪90年代中后期发生了明显的突变,GSS、GSE和GSL的突变年份为1994~1995年,AT10和DT10的突变年份为1997~1998年。④ 近60 a来华北地区生长季指标变化存在着2~3 a、5~6 a的主周期。生长季指标Hurst指数都大于0.7,表现为较强的持续性,其过去变化趋势将在未来继续延续。⑤ 北大西洋年代际振荡指数（AMO）是影响近60 a来华北地区生长季指标（GSS、GSE与AT10）变化的主要大气环流因子。     

塔克拉玛干沙漠腹地沙尘暴过程大气颗粒物浓度及影响因素分析

利用Grimm1.108、Thermo RP 1400a、TSP以及CAWS-600等仪器,对2008年4月17日至23日发生在塔克拉玛干沙漠腹地的1次强沙尘暴过程的颗粒物质量浓度进行连续观测,结合天气资料分析得出:①Grimm1.108颗粒物分析仪监测结果表明,日平均浓度出现两个峰值区,主峰值出现在20日,次峰值出现在18日,而小时平均浓度高值区主要集中4月19日至20日,21日中午存在1个峰值区,其他时段浓度相对较低。②强沙尘暴发生时的分钟观测数据表明,随着风速的逐渐增强,沙尘暴强度逐渐增强,不同粒径颗粒物浓度达到最大值,>0.23 μm颗粒物总浓度为39 496.5 μg·m-3,>20.0 μm颗粒物总浓度为5 390.7 μg·m-3,随后浓度逐渐下降。③PM10和TSP的浓度变化同样反映沙尘天气的过程和强度,沙尘暴前期大气中颗粒物浓度远低于强沙尘暴期间,随沙尘天气减弱,颗粒物浓度明显下降。④沙尘天气过程中大气颗粒物浓度变化具有以下规律：晴天<浮尘天气<浮尘、扬沙天气<沙尘暴天气。风速大小直接影响大气中颗粒物浓度,风速越大颗粒物浓度越高。气温、相对湿度和气压是影响沙尘暴强度的重要因素,也间接影响大气中颗粒物浓度的变化。     

湖北气温的3—5年周期振动及其与大气环流低频变化的联系

本文用月平均资料序列，提取湖北气温，北半球５００ｈＰａ高度和北太平洋海博温度的３－５年低频分量，分析研究了三者之间的联系，初步揭示了前期ＳＳＴ对湖北冬季气温影响的过程。     

库尔勒市大气颗粒物浓度特征及来源北大核心CSCD

在塔里木盆地东北部库尔勒市大气颗粒物逐时数据(2015年1月至2020年12月)污染特征分析的基础上,利用HYSPLIT模型、聚类分析、潜在源贡献因子分析(PSCF)、浓度权重轨迹分析(CWT)分析不同季节库尔勒市颗粒物传输路径与潜在源区,揭示研究期间库尔勒市不同季节大气颗粒物的潜在源分布及其贡献水平。结果表明:2015—2020年库尔勒市PM_(2.5)、PM_(10)年均值分别为47.7±20.0、162.2±102.4μg·m^(-3),超过国家年均值二级浓度限值132%、36.3%,PM_(10)为主要污染物;颗粒物季节变化呈现冬春高、夏秋低的变化特征;PM_(2.5)/PM_(10)值春季最低(0.29),冬季最高(0.47),PM_(2.5)/PM_(10)值整体呈下降趋势;气流输送路径主要来自西风短气流,其次为吐鲁番盆地的东灌气流;塔里木盆地全年四季都是库尔勒市颗粒物的主要贡献源区,颗粒物浓度贡献水平春冬季较高,夏秋季较低。     

海南旅游客流量年内变化与气候的相关性分析

气候是旅游资源不可或缺的组成部分,也是影响旅游地开发的重要因素,直接影响到旅游季节的长短及旅游客流的年内变化。利用海南9个气象站点自建站以来的气候资料及近5年旅游统计资料,通过特吉旺气候舒适指数、相关分析和回归分析等方法,分析海南气候舒适度及其与旅游客流量年内变化的相关性。结果表明:11月~3月是海南旅游的最适宜期;气候对海南旅游客流量有显著影响,以气温为主导的气候舒适度是海南旅游客流年内淡旺季变化及游客旅游决策的主要影响因素;温度与海南旅游客流量呈显著负相关关系;与海口比较而言,三亚旅游业对气候更加敏感。本项研究对更好地将气候整合到旅游产品中进行宣传促销、提高产品吸引力,对海南旅游业发展规划,对提前预判游客规模尽早做出对策安排及旅游投资有很强的现实指导意义。     

Comparisons on seasonal and annual variations of δ18O in precipitation

The spatial and temporal variations of stable oxygen isotope in precipitation on different time scales are analyzed according to the data from the IAEA/WMO stations with long survey series in the Northern Hemisphere. Temperature effect is mainly distributed in mid-high latitudes on seasonal scale except for Bamako and Addisababa stations. The δ18O/temperature slope displays the positive correlation against altitude for most of the statistical stations. Amount effect appears primarily in the region south of 30oN and coastal areas. The δ18O/precipitation slope is indirectly proportional to precipitation amount. For some of the sampling stations at mid-high latitudes where their seasonal distribution of precipitation is contrary to that of temperature, coupled with temperature effect, the amount effect appears synchronistically. Either the temperature effect or the amount effect on seasonal scale, there are positive correlations to a certain extent between the annual weighted mean δ18O and the annual mean temperature for almost all the stations. The correlation between composite δ18O and temperature on spatial scale is much more marked, compared with that of individual station. There is a good agreement between 10-year moving average temperature curves I and II, with the values of the former all markedly smaller than corresponding ones of the latter, calculated by the monthly mean series group I and the annual mean series group II, respectively. However, two calculated dδ18O/dT curves display the distinct difference: the variation amplitude of slope series II is larger than that of slope series I. Both curves had similar ascending trend from the 1960s to the 1970s, and then, their variations display the anti-phase. Moreover, the analyses show that there is negative correlation between slope series II and temperature series II. However, the status is different for slope series I and temperature series I. Both series have contrary trend from the 1960s to the 1970s, whereas the same trend since the 1980s.     

A record of vegetation dynamics and lake level changes from Lake Emakat,northern Tanzania,during the last c. 1200 years

Analyses of down-core variations in pollen and charcoal in two short cores of lake sediment and wood samples taken from the in situ remains of Nuxia congesta from Lake Emakat, a hydrologically-closed volcanic crater lake occupying the Empakaai Crater in northern Tanzania, have generated evidence of past vegetation change and lake level fluctuations. Eight AMS radiocarbon (¹⁴C) dates on bulk samples of lake sediment provide a chronological framework for the two cores and indicate that the sediment record analysed incorporates the last c. 1200 years. The in situ remains of a Nuxia congesta tree, now standing in deep water, were dated with three additional AMS ¹⁴C dates, suggesting tree growth within the interval ∼1500–1670 AD. Down-core variations in pollen from terrestrial taxa, particularly the montane forest trees Hagenia abyssinica and Nuxia congesta, indicate a broad period of generally more arid conditions in the catchment to c. 1200 AD and at a prolonged period between c. 1420 and 1680 AD. Variations in pollen from plants in lake margin vegetation indicate low lake levels, presumably as a result of reduced effective precipitation, contemporary with indications of relatively dry conditions mentioned above, but also during the late 18th and the late 19th centuries. The presence of charcoal throughout both cores indicates the frequent occurrence of vegetation fires. An increase in burning, evident in the charcoal data and dated to the early to mid second millennium AD, could relate to an expansion of human population levels and agricultural activity in the region.     

Comparisons on seasonal and annual variations of δ<Superscript>18</Superscript>O in precipitation

The spatial and temporal variations of stable oxygen isotope in precipitation on different time scales are analyzed according to the data from the IAEA/WMO stations with long survey series in the Northern Hemisphere. Temperature effect is mainly distributed in mid-high latitudes on seasonal scale except for Bamako and Addisababa stations. The δ¹⁸O/temperature slope displays the positive correlation against altitude for most of the statistical stations. Amount effect appears primarily in the region south of 30°N and coastal areas. The δ¹⁸O/precipitation slope is indirectly proportional to precipitation amount. For some of the sampling stations at mid-high latitudes where their seasonal distribution of precipitation is contrary to that of temperature, coupled with temperature effect, the amount effect appears synchronistically. Either the temperature effect or the amount effect on seasonal scale, there are positive correlations to a certain extent between the annual weighted mean δ¹⁸O and the annual mean temperature for almost all the stations. The correlation between composite δ¹⁸O and temperature on spatial scale is much more marked, compared with that of individual station. There is a good agreement between 10-year moving average temperature curves I and II, with the values of the former all markedly smaller than corresponding ones of the latter, calculated by the monthly mean series group I and the annual mean series group II, respectively. However, two calculated dδ¹⁸O/dT curves display the distinct difference: the variation amplitude of slope series II is larger than that of slope series I. Both curves had similar ascending trend from the 1960s to the 1970s, and then, their variations display the anti-phase. Moreover, the analyses show that there is negative correlation between slope series FI and temperature series II. However, the status is different for slope series I and temperature series I. Both series have contrary trend from the 1960s to the 1970s, whereas the same trend since the 1980s.     

The melting of floating ice raises the ocean level

It is shown that the melting of ice floating on the ocean will introduce a volume of water about 2.6 per cent greater than that of the originally displaced sea water. The melting of floating ice in a global warming will cause the ocean to rise. If all the extant sea ice and floating shelf ice melted, the global sea level would rise about 4 cm. The sliding of grounded ice into the sea, however, produces a mean water level rise in two parts ; some of the rise is delayed. The first part, while the ice floats, is equal to the volume of displaced sea water. The second part, equal to 2.6 per cent of the first, is contributed as it melts. These effects result from the difference in volume of equal weights of fresh and salt water. This component of sea rise is apparently unrecognized in the literature to date, although it can be interpreted as a form of halosteric sea level change by regarding the displaced salt water and the meltwater (even before melting) as a unit. Although salinity changes are known to affect sea level, all existing analyses omit our calculated volume change. We present a protocol that can be used to calculate global sea level rise on the basis of the addition of meltwater from grounded and floating ice; of course thermosteric volume change must be added.     

Inferring paleosalinity trends using the chrysophyte cyst to diatom ratio in coastal shallow temperate/subtropical lagoons influenced by sea level changes

Data on chrysophyte cyst to diatom ratios as an index to track Holocene paleosalinity changes are presented. Six sediment cores taken in four coastal systems influenced by Holocene sea level changes indicate that during the transition from marine/brackish to brackish/freshwater and freshwater conditions, increases in the cyst to diatom ratio were recorded. These data suggest that Holocene changes in paleosalinities in coastal aquatic systems may be tracked by using this simple index, however other factors (such as changes in nutrient levels) may complicate some interpretations. Nevertheless, data required to calculate this simple index are easy to obtain, and so relatively little effort is required to obtain some paleolimnological information on these two important algal groups.     

Holocene trophic state changes in relation to sea level variation in Lake Blanca, SE Uruguay

Paleolimnological data are presented relating trophic development to sea level variation in Lake Blanca, a small (0.6 km²), coastal fresh waterbody in southern Uruguay. Using a sediment core that extended to 7300 years BP, analyses of grain size, thin sections, organic matter, carbonate, total carbon, nutrients, diatoms and palynomorphs, allowed us to infer changes in trophic state and paleosalinities, which were closely related to Holocene sea level variation. Higher trophic states were observed during regressive events, most probably due to increases in runoff and erosion as regression progressed. Four diatom association zones (DAZ) were identified in the sediment core. The basal core section pre-dated the first Holocene marine transgression, contained no diatoms, chrysophyte cysts or non-siliceous microalgae, and showed C/N ratios values higher than 20. Thus, it is likely that the system exhibited terrestrial characteristics. In the second section (6500–2200 years BP, following the first Holocene transgression), there was dominance of marine/brackish diatom species. The lowest trophic states of the core were observed in this section. The third section (2200–1100 years BP), represented the system as it became separate from the Atlantic Ocean, and showed a dominance of brackish/freshwater species and increases in trophic state were observed. In the last section (after 1100 years BP), the system became fully freshwater as no marine or brackish diatom species were found, but a trend to oligotrophication was observed, probably due to nutrient depletion. However, after 1967 AD, eutrophication intensified because of forestry and soil fertilization in the catchment. Pollen association zones (PAZ) allowed us to identify four sections. Below 250 cm (2200 years BP), the core contained no pollen grains as redox potential and pH values were not conducive for pollen preservation. After 2200 years BP (when the system started to separate from the ocean), xerophilic taxa typical of coastal dunes colonized the catchment. Only after 1100 years BP (after fully freshwater conditions established) pollen grains of trees were observed.     

上荆江枯水位对河床冲刷及水库调度的综合响应

为系统揭示长江中游近期枯水情势及其对三峡水库蓄水的直接和间接响应,本文以冲刷剧烈、枯水位降幅最大的上荆江为例,通过统计其不同形式枯水位的变化特征,建立了水位下降与河床冲刷、水库不同运行方式的相关关系。结果表明,沙市站同流量枯水位几乎与枯水河槽河床平均高程等幅下降,枝城站枯水位下降幅度较小与本底河床形态、河床粗化及航道整治工程有关。上荆江汛前枯水位降幅、最低水位及极枯水位历时等枯水情势会受到三峡水库补水调度的影响,这种补水效应沿程递减,至沙市站补水调度仍然无法抵消河床下切对枯水位造成的影响。     

Upper Pleistocene and Holocene paleosalinity and trophic state changes in relation to sea level variation in Rocha Lagoon, southern Uruguay

Paleolimnological data are presented on trophic development in relation to sea level variation in Rocha Lagoon, a 72 km² coastal lagoon in southern Uruguay. Using sediment cores that extended to ∼20,000 yr BP, analyses of grain size, organic matter, carbonate, total carbon, nutrients, and diatoms allowed us to infer changes in trophic state and paleosalinities, which were closely related to Holocene relative sea level variation. Higher trophic states were observed during regressive events, most probably due to increases in runoff and erosion as regressions progressed. Diatom Association Zones (DAZ) were identified in both cores. Those DAZ corresponding to transgressive events were dominated by marine/brackish taxa and relatively low organic matter and nutrient values, while those DAZ corresponding to regressive events showed increases in brackish/freshwater diatoms and both organic matter and nutrients. Although the lagoon formed after the first Holocene marine transgression, our data indicate the existence of a marine/brackish aquatic system during upper Pleistocene (i.e., before 15,000 yr BP), but by ∼20,000 yr BP, the system was still likely to be a semi-arid terrestrial system.     

长江口水域悬沙浓度时空变化与泥沙再悬浮

A detailed analysis of suspended sediment concentration (SSC) variations over a year period is presented using the data from 8 stations in the Yangtze River estuary and its adjacent waters, together with a discussion of the hydrodynamic regimes of the estuary. Spatially, the SSC from Xuliujing downwards to Hangzhou Bay increases almost constantly, and the suspended sediment in the inner estuary shows higher concentration in summer than in winter, while in the outer estuary it shows higher concentration in winter than in summer, and the magnitude is greater in the outer estuary than in the inner estuary, greater in the Hangzhou Bay than in the Yangtze River estuary. The sediments discharged by the Yangtze River into the sea are resuspended by marine dynamics included tidal currents and wind waves. Temporally, the SSC shows a pronounced neap-spring tidal cycle and seasonal variations. Furthermore, through the analysis of dynamic mechanism, it is concluded that wave and tidal current are two predominant factors of sediment resuspension and control the distribution and changes of SSC, in which tidal currents control neap-spring tidal cycles, and wind waves control seasonal variations. The ratio between river discharge and marine dynamics controls soatial distribution of SSC.