The influence of natural and anthropogenic factors on mangrove dynamics over 60 years: The Somone Estuary, Senegal

Although such ecosystems are fragile, this study shows that the anthropogenic damages inflicted on the mangrove forests of West Africa can be reversed over a relatively short time period if environmental conditions are favorable. The mangrove ecosystem of the microtidal Somone Estuary, Senegal, has undergone extreme changes during the last century. The area occupied by mangrove forest was estimated with a diachronic study by GIS for the period 1946-2006. Between 1946 and 1978, 85% of the area was progressively replaced by unvegetated mudflats in the intertidal zones and by barren area in the supratidal zones. Until 1990, this was mainly a result of traditional wood harvesting. The impact was exacerbated by the closing off of the estuary to the sea (1967-1969 and 1987) and by an extended drought (1970 onwards), which resulted in a lack of renewal of water, hypersalinization and acidification. The main factors controlling mangrove evolution in the Somone ecosystem, however, are anthropogenic. Until 1990, traditional wood cutting (for wood and oyster harvesting) was practiced by the local population. Between 1978 and 1989, a small area occupied by the mangroves was stabilized. Since 1992, a modification of mangrove logging and a new reforestation policy resulted in an exponential increase of mangrove area progressively replacing intertidal mudflats. Such success in the restoration of the ecosystem reforestation is supported by favorable environmental conditions: tidal flooding, groundwater influence, rainfall during the wet season, low net accretion rate of about 0.2-0.3 cm year⁻¹, and a ban on the cutting of mangrove wood. The rate of mangrove loss from 1946 to 1978 was 44,000 m² year⁻¹, but this has been offset by restoration efforts resulting in an increase in mangrove area from 1992 to 2006 of 63,000 m² year⁻¹.     

Changing anthropogenic influence on the Santa Monica Bay watershed

Santa Monica Bay is an open coastal embayment located directly seaward of Los Angeles, California. The Bay provides vital economic value through its water-dependent activities, such as swimming, diving, boating, and fishing. An increase from 100,000 residents in 1900 to 10 million in 2000 has imposed numerous environmental stressors on the Bay, including urbanization of the watershed. Pollutant discharges into the Bay increased throughout the early part of the century, but declined following passage of the Clean Water Act in 1972. Since that time, the predominant source of pollutant inputs has changed from point sources to non-point urban runoff. To assess how present-day and historical pollution interact to affect the environmental quality of Santa Monica Bay, three organizations collaborated on a multi-disciplinary study in 1997, towards which this volume is focused. This paper details the temporal patterns of anthropogenic influence on Santa Monica Bay to provide context for the papers that follow.     

西北太平洋热带气旋的闪电特征及其与强度关系的初步分析

使用TRMM卫星搭载的闪电成像传感器测得的1998-2005年间的闪电信息,结合热带气旋的活动特征,提出了一种识别热带气旋闪电的方法,进而分离了1998-2005年西北太平洋热带气旋的闪电信息,并在此基础上,对西北太平洋的热带气旋闪电特征进行了初步分析.结果表明:西北太平洋热带气旋的眼壁附近(距热带气旋中心约30~50km)、内雨带(热带气旋中心外约60~100km)和外雨带(热带气旋中心外约130~610km)内普遍存在闪电现象,而且各月均有发生,并以7-8月较频;我国东南沿海地区,特别是台湾岛-台湾海峡-福建沿海地区、珠江三角洲的近海海域,是最易发生热带气旋闪电的两个区域,而日本岛东南方向广阔的西北太平洋洋面上的热带气旋,则较少有闪电发生.此外,闪电与热带气旋的强度及其变化有一定的关系,利用发生在热带气旋不同区域的闪电信息可对热带气旋的强度进行估算,估算的误差与目前的业务定强误差接近.     

起伏海面的雷电电磁场传播特征及其对闪电定位精度的影响

为了研究起伏海面对雷电电磁传播的影响,本文利用Barrick表面阻抗理论和Wait近似算法,采用改进二维分形海面模型模拟起伏海面,利用数值模式,分析起伏海面的雷电电磁传播特征,并进一步讨论了起伏海面对时差法闪电定位系统定位精度的影响。结果表明:起伏海面对垂直电场和磁场的峰值的影响不显著,但会引起波形的上升期时间的延长,浪高越大,影响越明显;随着观测距离的增加,雷电垂直电场波形的上升时间逐渐变长;风速的变化与雷电垂直电场波形的上升时间成正比;由于海面起伏引起雷电电磁场波形在传播中的变化会影响基于时差法闪电定位系统的定位精度,定位误差可达几至十几公里。     

Hunnebotn: a seawater basin transformed by natural and anthropogenic processes

The lake Hunnebotn (A=1 km², z_max=11 m) has become separated from the sea by isostasis, but a 1.5-m-deep channel is held open by periodic dredging. Water exchange is minor due to the small tidal range (21 cm) and the length of the channel (1.8 km), but there may be an inflow of seawater at spring tides. The terrestrial watershed runoff may be fertilized by sewage and agricultural runoff despite some measures taken to prevent this. Historical and new records of biological communities indicate variations in sensitivity to different phases of the isolation and eutrophication process. The native oyster was most sensitive and disappeared first. Later, the eelgrass disappeared possibly due to overgrowth by epiphytic algae, and finally there was a massive littoral–sublittoral invasion of green algae. The lake should not be left in this condition, for aesthetic reasons and because marine inlets and eutrophic brackish water may serve as refugia for spore populations of toxic microalgae. Improving surface water quality will require better control of anthropogenic sources, but bursts and leaks of nutrients from the anoxic monimolimnion cannot be controlled.     

热带气旋闪电活动特征研究综述

针对热带气旋(tropical cyclone,TC)闪电已有研究,首先从闪电活动分布特征、眼壁闪电爆发对TC强度和路径的指示、外雨带闪电活动与雨带对流结构的关系三个方面进行了总结;其次从动力-微物理方面对TC闪电的形成原因和特征机理进行了梳理;最后提出当前研究中存在的两个关键问题,并对后续研究内容进行了展望。基于地基和空基相结合的综合闪电探测得到的闪电属性特征参量,有望建立一个明确的、具有代表性的闪电活动-TC强度变化关系。利用沿海地区架设的三维闪电定位系统结合地基双偏振雷达,针对登陆台风强对流过程开展的综合观测研究,将有助于推进闪电观测资料在台风中小尺度强对流监测、预警和资料同化中的应用。     

The influence of dissolved petroleum hydrocarbon residues on natural phytoplankton biomass

The effect of dissolved petroleum hydrocarbons in the environment on phytoplankton biomass measured as chlorophyll a was studied near the oil tanker route in the southern Bay of Bengal. In the transect from 5° N, 77° E to 5° N, 87° E the concentrations of dissolved petroleum hydrocarbons were negatively correlated with phytoplankton biomass, whereas in the 0° N, 87° E to 1° N, 79° E transect they were positively correlated with phytoplankton biomass. The mean petroleum hydrocarbon concentrations in the two transects were 12·12 ± 4·67 μg litre⁻¹ and 11·23 ± 4·5 μg litre⁻¹, respectively.It is surmised that the effect of dissolved petroleum hydrocarbons on phytoplankton biomass varies depending on the nature rather than the quantity of petroleum hydrocarbons present. Culture studies with unialgal Nitzschia sp. in seawater collected from selected stations in the study area as well as in artificial seawater spiked with the water-soluble petroleum hydrocarbon fraction of light Arabian Crude support this.     

强对流过程对大尺度模式洋面通量加强的参数化研究与进展

由于地球表面热通量直接决定着大气环流运动,在大气数值模式中如何准确描述地球表面热通量就变处得十分重要.洋面是地球表面最广泛分布的下垫面,它的表面热通量描述尤为被重视.尤其是西赤道太平洋暖池、东赤道太平洋冷舌、ITCZ及信风带等关键区域的洋面热通量的准确估计更是非常重要,这些区域的地表通量变化通常被认为是全球气候变化即ENSO现象的最重要的信号[1].众所周知,中尺度降水对流在以上关键海域频繁发生.中尺度降水对流系统往往有较强的下沉气流(downdraft)[2],这种下沉气流在中尺度降水对流系统与大尺度过程的相互作用中伴演着重要角色.     

Estimation of the influence that natural fires have on air pollution in the region of Moscow megalopolis based on the combined use of chemical transport model and measurement data

Satellite measurements of the fire radiation power, measurements of atmospheric pollution in the network of GPU Mosekomonitoring stations, and the modern CHIMERE chemical transport model (CHIMERE CTM) are used for estimating the influence that forest fires have on the air pollution level in the Moscow megalopolis region during the summer of 2007. The method by which the radiation power caused by natural fires determined from satellite measurements is converted into emissions of individual model species is described. General problems related to the optimization of estimates of fire emission and the effects caused by them based on the combined use of measurement data on the composition of the atmosphere and the CTM are considered using a concrete example. It is shown, in particular, that the use of the standard least squares method for the optimization of fire emissions from leads in the general case to obtaining biased (underestimated) estimates. The results of calculations consistent with measurements show that forest fires near Moscow can occasionally be responsible for a considerable part of the air pollution observed in Moscow and its vicinities, and they can be the main reason for the high level of atmospheric pollution in some neighboring regions.     

Dispersal of natural and anthropogenic lead through submarine canyons at the Portuguese margin

Submarine canyons represent natural conduits for preferential transport of particulate material, including anthropogenic contaminants, from coastal zones directly to the deep sea. To assess related dispersal of natural and anthropogenic lead (Pb), we analyzed Pb concentrations and stable isotope ratios in surface sediments and sediment trap particulate material from the Portuguese margin Nazaré and Setúbal/Lisbon canyons. Geochemical data are integrated with previously obtained data on near-bottom hydrodynamics and processes and pathways of sediment transport. The two canyon systems are located in close geographic proximity to each other, but represent contrasting settings in terms of sediment input and down-canyon sediment transport processes.Concentration–isotope diagrams and three-isotope plots (²⁰⁶Pb/²⁰⁷Pb vs. ²⁰⁸Pb/²⁰⁶Pb) suggest binary mixing between natural and anthropogenic end members. The inferred isotopic signature of pollutant Pb (²⁰⁶Pb/²⁰⁷Pb=1.143 [1.134–1.149, 95% confidence interval]) is most consistent with industrial Pb; ongoing influence from gasoline Pb additives is at most of minor importance. Two proposed natural end members most likely bracket the isotopic signature of natural Pb. Accordingly, binary mixing calculations indicate that on average 20–45% vs. 35–55% of total Pb is derived from anthropogenic sources in the Nazaré and Setúbal–Lisbon canyon systems, respectively. Enhanced anthropogenic influence in the latter area is consistent with its proximity to heavily populated and industrialized areas and with sediment input from the Tagus and Sado rivers, potential major carriers of pollutant particles. In both canyon systems, the anthropogenic component generally decreases with increasing water depth.Isotopic signatures of sediment trap particulate material are generally consistent with surface sediment data at similar water depth, but show large variability in the upper Nazaré canyon and major deviations from surface sediments in the lower canyon. In the lower canyon, Pb isotopic ratios of sediment trap particulate material mostly reflect low pelagic fluxes from the overlying water column, whereas surface sediment signatures are dominated by episodic down-canyon mass transport events. Such gravity flows appear to incorporate older (pre-industrial) material masking the isotopic signature of pollutant Pb. Large variability in the upper canyon reflects continuous sediment resuspension by bottom currents. Stronger average bottom currents are associated with higher ²⁰⁶Pb/²⁰⁷Pb ratios of sediment trap particulate material and hence decreased influence of pollutant Pb. This may reflect preferential resuspension of natural Pb at the canyon floor and/or additional remobilization of older, less-polluted sediment in adjacent areas such as the canyon walls.     

不同环境因素影响下直链藻垂向分布特性研究

为了解不同环境因素对水库内直链藻(Melosira)垂向分布的影响程度, 作者利用自制沉降柱实验模拟不同光照、水动力以及降雨条件对水中直链藻垂向分布的影响。通过单因素方差分析实验数据表明光照和降雨条件的改变对上浮区内直链藻的垂向分布具有显著影响, 底部出流流量的改变对下沉区内直链藻的垂向分布具有显著影响。随着水深的增加, 光照和降雨对水中直链藻垂向分布的影响减弱而水动力则对其影响增强。同时还验证了直链藻具有较强的趋光性, 宜在低光强环境内生长, 模拟测得其最适光强在3 000 lx 左右; 降雨对水中直链藻的垂向分布起到抑制作用, 降雨强度越大水中直链藻就越偏离水体表面; 在底部出流流量影响范围内, 随着出流流量的增大水中直链藻就越向水动力改变处聚集且稳定时间越短。     

Analyzing qualitative and quantitative changes in coastal wetland associated to the effects of natural and anthropogenic factors in a part of Tianjin,China

Natural and anthropogenic factors in coastal wetland changes are widely discussed in wetland studies. Previous literatures have demonstrated that many factors may cause wetland change and argued that the global climate change and nutrient enrichment may become the most important ones in the next 50 years. Through field investigation, with the help of remote sensing technology and geographic information system, this research discusses the wetland change in Tianjin under the great pressure of rapid economic development, population growth, and sea-level rising. These findings include: (1) the wetland area expanded from 466.50 km² to 658.38 km² between 1987 and 1998, but it shrank to 550.5 km² by the year of 2006. (2) The results show that the groundwater has not been contaminated while the surface water has been polluted. (3) The questionnaire survey shows that the social environment in some specific ways impedes the protection of natural reserve. In order to achieve the harmony between human and nature, feasible countermeasures on how to keep ecological balance should be immediately taken. Consequently, natural conservation and sustainable economic development will be realized.     

长江口夏季水体磷的形态分布特征及影响因素

根据2006年7月至9月"海监49号"科学考察船夏季航次的调查数据,分析了长江口及邻近海域水体中磷形态的平面分布特征及其影响因素,结果表明,调查海域水体各种形态磷平均浓度均为底层高于表层,并呈现出由河口向邻近海域降低的趋势.杭州湾及最大混浊带部分区域水体中以颗粒态磷为主,且颗粒态无机磷为磷的主要存在形态;长江口门及江苏东部近海区域水体中以溶解态磷为主,溶解态无机磷为磷的主要存在形态;舟山群岛东部外海区表层水体以溶解态磷为主,溶解态有机磷为磷的主要存在形态,而底层水体中溶解态磷浓度略高于颗粒态磷,以溶解态无机磷为磷的主要存在形态.水体中颗粒态无机磷与颗粒态有机磷、颗粒总磷与总磷、总磷与悬浮颗粒物均呈非常显著的正相关,说明悬浮颗粒物是颗粒态磷的主要影响因素.调查海域外海区域绝大部分站位水体中溶解态无机磷表层浓度接近或小于浮游植物生长限制的动力学最低阈值,是磷限制或潜在的磷限制区域.     

泰山景区地闪分布特征及与海拔高度关系研究

我国因雷击造成的森林火灾和景区人员伤亡时有发生,近年来,泰山景区也多次发生雷击森林火灾和设备损坏等事故。为了有效地避免或降低雷击对泰山景区的危害,利用2007—2018 年山东省闪电定位系统监测的地闪资料,对泰山景区闪电活动特征及其与地形、海拔的相关性进行分析,从而为有效地开展防雷减灾服务及为地方政府部门决策提供技术支撑。 结果表明：虽然不同年份的落雷次数有所差别,但每年不同海拔高度落雷次数的分布特征比较一致,泰山景区年均地闪密度为1.82 次•km-2•a-1,地闪密度较高的区域集中在主峰和主峰西北方4 ～7 km附近山顶区域;地闪活动的季节性分布特征明显,夏季（6—8月）地闪次数约占全年总地闪次数的86.86%,海拔900 m以下落雷次数较多;日落雷次数的高峰时段为14:00—20:00,落区集中在200～800 m之间;正闪强度均值随海拔升高波动较大,负闪强度随海拔的变化较小;地闪密度随海拔升高呈现上升趋势,海拔高度＜800 m的区域地闪密度随海拔增加呈缓慢上升的趋势,海拔高度＞1 000 m的区域地闪密度随海拔增加呈明显上升的趋势,同时发现随海拔高度的增加地闪密度和陡度呈现增大和增高的趋势,800 m以上尤其明显,可见泰山景区地闪密度与陡度和海拔高度呈现较好的正相关性。     

Key natural and anthropogenic parameters enhancing the effect of sea level rise: The case of Israel's Mediterranean coast

Sea level rise (SLR) adversely impacts groundwater quality and capacity of coastal regions. The objectives of this paper are to determine key natural and anthropogenic parameters which may influence and enhance adverse SLR impact upon coastal environments, as well as to assess these natural and anthropogenic components contributing to SLR, and enhance adverse effects of SLR on the environment. This would enable assessment of vulnerability of coastal areas. Components are evaluated in this paper by averaging data relative to respective measured parameters, along with given weightings and assessed ratings, vis-à-vis world maximal reference values. Israel's Mediterranean coast is utilized as an example for such an approach. This can indicate where operational long-term planning measures would be recommended, along with development of effective monitoring and the carrying out of helpful engineering and ecological activities.     

胶州湾海水痕量金属?溶解有机质分配特征及其影响因素探讨

采集胶州湾表层和底层海水样品,分析了Cu、Cr、Cd、Pb、Ni、Co等痕量金属在海水中的空间分布特征及其在不同分子量溶解有机质中的分配特征,并探讨了痕量金属?溶解有机质分配机理及浮游生物活动与盐度等环境因素对该分配过程的影响。结果表明,胶州湾海水中痕量金属呈近岸浓度较高的分布特征,在湾东北部出现高值区,Cd和Pb还分别在湾口与湾中部出现高值区。胶州湾海水中痕量金属平均有70.1%分配于低分子量(<1 kDa)组分中,其中Cu和Cd低分子量组分所占平均比例分别达79.0%与77.6%,Cr、Ni和Co稍低,分别为71.5%、67.3%及66.9%,Pb则仅为58.2%。海水中的溶解有机碳也以低分子量组分为主,所占比例平均达73.1%,且光谱特征显示低分子量溶解有机质中类腐殖质含量更高,含有丰富的羧基和羟基,金属配合能力较高,导致痕量金属多分配于低分子量溶解有机质中。高分子量溶解有机质(>1 kDa)所占比例与叶绿素a浓度呈显著正相关,表明浮游植物初级生产通过释放高分子量溶解有机质影响海水痕量金属?溶解有机质的分配过程。胶州湾湾顶盐度较低海域痕量金属高分子量组分略高,可能是生物活动及陆源输入(产生更多高分子量溶解有机质)与盐度(低盐有利于高分子量有机质的稳定性)共同作用的结果。     

海洋分层介质中雷电电流源的水平辐射电场传播特征研究

随着我国海洋战略的持续推进,海上各类固定及移动的工作平台均需进行更加有效的雷电防护。海上防雷工作中深入了解雷电电流源水平辐射电场(Er),在海洋分层介质中的传播特性则是一项十分重要的工作。本文就能够对海上设施产生较大影响的地闪进行研究,因此选取具有代表性的正地闪首次回击电流源(PS)及Nucci电流源(TLS),通过时域的方法对两种雷电电流源的水平辐射电场在由空气、海水及洋壳所组成的海洋分层介质中的传播特征进行对比分析。结果表明:(1)在海面及其以上的高度(h≥0 m),当距雷电电流源水平距离r=0 m时,两种雷电电流源产生的Er均为正值;其中PS产生的Er是随时间呈对数增加,而TLS的则随时间呈单峰正偏态分布;当r0 m时,两种雷电电流源产生的Er与r=0 m时的基本呈反位相。(2)当r=0 m,h介于0~50 m及100~500 m之间,PS于雷电发生后10μs的Er值则分别介于3.273 3×10~6~1.177 1×10~7v/m及1.035 1×10~7~1.155 3×10~7v/m之间,而TLS的Er峰值则分别为9.274 7×10~5~2.887 6×10~6v/m及2.688 7×10~6~2.854 2×10~6v/m之间。(3)当h=10 m,r介于50~500 m之间,PS于10μs的Er值则介于-1.1216×104~-7.027 9 v/m之间,而TLS的Er峰值则介于-2.478 4×10~3~1.385 9 v/m之间;当h=10 m,r=1 000 m时,TLS的Er峰值为9.482 6 v/m。(4)在海面以下(h0 m),r介于50~1 000 m之间,两种雷电电流源的Er主要为正,且随时间均呈单峰正偏态分布;当h=-5 m及-10 m时,PS与TLS的Er值于两个深度的差分别介于5~53 v/m与2~28 v/m之间。     

雷达波段对多极化SAR海面溢油检测极化特征参数的影响

多极化SAR数据海面溢油检测研究日益受到重视。本文研究不同波段极化SAR数据的海面溢油检测能力,为最大程度减小观测条件、环境因素等的影响,选取准同步获取的SIR-C/X多极化SAR数据。针对海面油膜、生物油膜和低风区疑似溢油现象,研究L波段和C波段的共极化相位差、一致性系数、极化熵、各向异性和平均散射角等极化特征对海面油膜以及不同海面暗斑现象的检测能力。研究结果表明:在海面溢油检测以及探测不同暗斑现象间差异方面,C波段总体优于L波段;L波段,极化分解特征各向异性参数优于共极化相位差和一致性系数;C波段,共极化相位差、一致性系数特征优于极化分解特征各向异性和极化熵,结合平均散射角特征有助于滤除生物油膜和低风区。     

Parameters of thunderstorm activity and lightning discharges in Central Yakutia from 2009 to 2012

The results of integrated instrumental observations of thunderstorm activity around Yakutsk at a radius of 400 and 30 km are presented. The seasonal course of thunderstorm activity was found to contain characteristic peaks in the first 10 days of June and the last 10 days of July or early August. The fraction of cloud-to-ground discharges in Central Yakutia is 40–60%, which is consistent with observations in Western Siberia (40–50%). The number of positive discharges to the ground was 8–15% of all cases of discharges to the ground, which is consistent with observations in Germany (17%) and slightly exceeds the observed number in the Caucasus (2.2–8.2%) and United States (4.5%). The thunderstorm activity in Yakutsk is three times higher than in the area around Yakutsk with a radius of 400 km, which can be explained by the fact that the city is a heat island.     

Use of surface sediments in Pagassitikos Gulf, Greece, to detect anthropogenic influence

Volos city and its port are situated in the northern part of Pagassitikos Gulf, a shallow, semi-enclosed marine area in central Greece. A wastewater treatment plant (WWTP) and pipeline operate in the same area. Muddy sediments with low carbonate contents cover most of the seabed, except for the Volos embayment and the western part of the gulf where sandy carbonates prevail. Bulk organic carbon contents and the organic carbon contents of the clay fractions are high in the vicinity of Volos embayment. High element (Pb, Cu, and Zn) contents and Igeo (geoaccumulation index) values were found for the clay fractions in the northern part of Pagassitikos Gulf. This enrichment is attributed to the discharge of raw domestic and industrial effluents of Volos city and port before the WWTP was installed. The dispersal of pollutants is essentially controlled by diffusion from point sources (city, port and WWTP) and is limited to Volos Bay. Relatively high Mn levels are ascribed to diagenetic formation of manganese carbonates (authigenic phase), whereas Cr and Ni are elevated due to weathering of ultrabasic formations on land.