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71.
In this paper, a method of assessing water quality from satellite data is introduced. The composite pollution index (CPI) was calculated from measured chemical oxygen demand (COD) and nutrient concentration. The relationships between CPI and 240 band combinations of SeaWiFS water-leaving radiance were analyzed and the optimal band combination for estimating CPI was chosen from the 240 band combinations. An algorithm for retrieval of CPI was developed using the optimal band combination, (L443 × L510)/(L412 + L490). The CPI was estimated from atmospherically corrected SeaWiFS data by employing the algorithm. Furthermore, the CPI value range for each water quality level was determined based on data obtained from 850 samples taken in the Pearl River Estuary. The remotely sensed CPIs were then transferred to water quality levels and appropriate maps were derived. The remotely sensed water quality level maps displayed a similar distribution of levels based on in situ investigation issued by the State Ocean Administration, China. This study demonstrates that remote sensing can play an important role in water quality assessment.  相似文献   
72.
英国气象局的长期天气预报,是每月第二周的星期一发布。预报时段为1—5天,6—15天和16—30天。预报区有10个,预报要素是平均气温和降水。制作这些预报,首先是报出这三个预报时段的平均地面气压(1—5天的预报只报1000—500hPa 的厚度场)。所使用的预报方法如表1:  相似文献   
73.
The WFD has introduced an international commitment to assess the ecological status of transitional waters (TWs), within which fish communities are a key biological monitoring component. The Transitional Fish Classification Index (TFCI) outlined in this paper uses 10 ecological measures to analyse fish populations caught from various ecological niches using a variety of gear types within the Thames estuary. These reach and method-specific communities are then compared to a reference population created from a 'healthy' population from TWs of a similar type. The results indicate a progressive downstream increase the quality of fish communities, consistent with previous work; variation between methods can be accounted for by gear selectivity. Overall, the TFCI is an effective communication tool for converting ecological information into an easily understood format for managers, policy makers and the general public.  相似文献   
74.
在高分辨率SPOT卫星数字影像和大比例尺航片处理、断错地貌制图、野外核实与位移测量基础上, 利用宇宙成因核素(10Be, 26Al)、碳十四(14C)和热释光(TL)等多种测年手段, 厘定了各断错地貌面的形成年龄, 得到了阿尔金断裂带不同段落全新世左旋走滑速率: 阿克赛以西的中、西段左旋走滑速率可达(17.5±2) mm/a, 肃北-石包城段为(11±3.5) mm/a左右, 疏勒河口段减少到(4.8±1) mm/a左右, 东端宽滩山段仅约(2.2±0.2) mm/a, 左旋走滑速率突变点位于阿尔金断裂带中东段存在分支活动逆断层向南东扩展的肃北、石包城和疏勒河等三联点上. 矢量分析表明, 三联点东、西两侧左旋滑动速率的减少量转换成了阿尔金断裂带中东段南盘北西向活动逆断层上的地壳缩短和上盘推覆体抬升, 形成了党河南山、大雪山、祁连山等条块山地. 因此, 青藏高原北部物质向东挤出的速率和幅度是有限的, 符合“叠瓦状逆冲转换——有限挤出模型”.  相似文献   
75.
PCBs were analysed in surficial sediments and selected sediment cores collected between 2002 and 2008 in Central Vietnam coastal lagoons. The aim was to determine contamination levels and trends, and to evaluate the effects of anthropogenic pressures and natural events. Samples were mostly fine-grained with low total PCB concentrations (0.367-44.7 μg kg−1). Atmospheric transport and post depositional processes modify to some degree the fingerprint of PCB inputs to the environment favouring the predominance of 3, 4 and 5 chlorinated congeners. The similarity of congener distributions in contemporary surficial samples also suggests the presence of a unique source over the entire study area, probably connected to mobilisation and long range transports from land-based stocks. The removal of consistent sediment layers is hypothesised based on repeated samplings of the same area. Natural meteorological events (such as typhoons) are suspected to be responsible for these sediment losses.  相似文献   
76.
Although large loads of potentially toxic constituents are discharged from coastal urban watersheds, very little is known about the fates and eventual impacts of these stormwater inputs once they enter the ocean. The goal of this study was to examine the effects of stormwater discharges on the benthic marine environment of Santa Monica Bay. Sediment samples were collected across a gradient of stormwater impact following significantly sized storm events offshore Ballona Creek (a predominantly developed watershed) and Malibu Creek (a predominantly undeveloped watershed). Sediments offshore Malibu Creek had a greater proportion of fine-grained sediments, organic carbon, and naturally occurring metals (i.e., aluminum and iron), whereas sediments offshore Ballona Creek had higher concentrations of anthropogenic metals (i.e., lead) and organic pollutants (i.e., total DDT, total PCB, total PAH). The accumulation of anthropogenic sediment contaminants offshore Ballona Creek was evident up to 2 km downcoast and 4 km upcoast from the creek mouth and sediment concentrations covaried with distance from the discharge. Although changes in sediment texture, organic content, and an increase in sediment contamination were observed, there was little or no alteration to the benthic communities offshore either Ballona or Malibu Creek. Both sites were characterized as having an abundance, species richness, biodiversity and benthic response index similar to shallow water areas distant from creek mouths throughout the Southern California Bight. There was not a preponderance of pollution tolerant, nor a lack or pollution sensitive, species offshore either creek mouth.  相似文献   
77.
In this part ot the paper theoretical wind-wave spectra nave been derived oy (I) expressing the spectrum in series composed of exponential terms; (2) assuming that the spectrum satisfies a high order linear ordinary differential equation; (3) introducing proper parameters in the spectrum; and (4) making use of some known charateristics of wind-wave spectrum, for instance, the law governing the equilibrium range. The spectrum obtained contains the zero order moment of the spectrum m0, the peak frequency ω0 and the ratio R =ω/ω0 (ω being the mean zero-crossing frequency) as parameters. The shape of the nondimensional spectrum S(ω) = ω0S(ω)/m0(ω=ω/ω0) changes with R and theoretically reduces to a Dirac delta function δ(ω-1) when R = 1. A spectrum of simplified form is given for practical uses, in which R is replaced by a peakness factor P=S(1).  相似文献   
78.
2011年8月至2013年7月中国地震局地球物理研究所与蒙古科学院天文与地球物理研究中心在蒙古中南部区域布设了宽频带流动地震台阵,这为开展远东地区深部结构的精细探测提供了有利的数据基础.利用台阵记录的远震地震事件,采用P波接收函数的H-κ叠加分析和共转换点(CCP)叠加方法获得了台站下方的地壳厚度及平均波速比.结果显示研究区的地壳厚度介于39 km至45 km之间.整体上Moho面埋深从西北往东南方向逐渐变浅.在蒙古主线性构造两侧地壳厚度呈现区域性变化特征,东南部地区地壳厚度较薄,约为39 km,而西北部地区地壳较厚,达45 km,为此推测蒙古主构造线可能是地壳的一个陡变带.此外,研究地区地壳的平均波速比值(VP/VS)在1.70到1.79之间,均值为1.75,低于全球大陆的平均值1.78,这可能暗示着该区其地壳是缺少铁镁质的.研究还发现测线的西北与东南地区其地壳波速比值较高,推测是古生代铁镁质地壳的残留或是新生代岩浆底侵的反映.  相似文献   
79.
The concentration and distribution of some trace elements were determined in stomach contents, excreta and feathers of Adélie penguins (Pygoscelis adeliae) breeding at Edmonson Point (Terra Nova Bay-Antarctica). In these materials obtained by non-destructive methods, concentrations of mercury, cadmium and lead measured were used to establish natural levels of these metals in the penguins' diet. An intake-excretion hypothesis was formulated.  相似文献   
80.
An examination of decay and growth rates of electric field near the ground during total solar eclipse of 16 February 1980 was made to study the electrical relaxation time and conductivity at Raichur. The values obtained i. e., 1320 seconds and 67.1163× 10-16 mhos m-1 of the two parameters were in fair agreement with the reported ones at the rural locations.  相似文献   
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