Surveillance for previously unmonitored organic contaminants in the San Francisco Estuary     

Oros DR  Jarman WM  Lowe T  David N  Lowe S  Davis JA 《Marine pollution bulletin》2003,46(9):1102-1110

The San Francisco Estuary Regional Monitoring Program initiated surveillance monitoring to identify previously unmonitored synthetic organic contaminants in the San Francisco Estuary. Organic extracts of water samples were analyzed using gas chromatography-mass spectrometry in full scan mode. The major contaminant classes identified in the samples were fire retardants, pesticides, personal care product ingredients, and plasticizers. Evidence from the literature suggests that some of these contaminants can persist in the environment, induce toxicity, and accumulate in marine biota and in higher food chain consumers. The major sources of these contaminants into the marine environment are the discharge of municipal and industrial wastewater effluents, urban stormwater, and agricultural runoff. As a proactive effort, it is suggested that surveillance studies be used routinely in monitoring programs to identify and prevent potential problem contaminants from harming the marine environment.  相似文献   

Incremental Growth of Plains-Type (Compactional) Folds in a Cratonic Environment as Revealed by the Sedimentary Sequence     

Merriam  Daniel F. 《Natural Resources Research》2003,12(1):27-40

The enigma of the origin and development of plains-type folds, as they were christened in the early 20th Century, essentially has been solved. The folds, a considerable distance from the tectonic disturbance, were formed by draping of sediments over differentially displaced Precambrian basement fault blocks. These Precambrian basement fault blocks controlled the location, size, and shape of the folds. Forces were transmitted through the rigid basement causing readjustment along the indigenous fracture/fault pattern formed much earlier. In the U.S. Midcontinent, the crystalline basement is overlain by a thin veneer of sediments, and once the structures were formed, they continued to develop as evidenced by features in the overlying sediments. As the stress was transmitted through the basement and then relaxed, the fault blocks moved differentially in concert to these outside forces. Sediment compaction and nondeposition over structural topographic highs reacted accordingly to form the features as seen today. To determine the structural history, structural closure on different horizons on the anticline is plotted in their appropriate stratigraphic position at depth. This gives a compaction line for each tectonically coherent segment. Similar segments show a relatively straightline with offsets at major unconformities indicating breaks in the continuum. It is at these breaks that the section can be stretched until the compaction line matches as a continuum with the resulting gap giving the approximate amount of missing section for that part of the rock column. Conversely, the amount of closure on a structure at depth for each line segment can be estimated by extrapolating downward in that segment. This technique to determine depth of burial and thus the amount of missing stratigraphic section from well data at numerous locations has been compared with estimates made by other methods and the results are similar. Where no other data are available or for quick estimates, then, it is proposed that this approach will give reasonable results and that the values can be used as a constraint in basin modeling.  相似文献   

Influence of vegetation change on watershed hydrology: implications for paleoclimatic interpretation of lacustrine δ18O records     

Michael F. Rosenmeier  David A. Hodell  Mark Brenner  Jason H. Curtis  Jonathan B. Martin  Flavio S. Anselmetti  Daniel Ariztegui  Thomas P. Guilderson 《Journal of Paleolimnology》2002,27(1):117-131

Stratigraphic shifts in the oxygen isotopic (¹⁸O) and trace element (Mg and Sr) composition of biogenic carbonate from tropical lake sediment cores are often interpreted as a proxy record of the changing relation between evaporation and precipitation (E/P). Holocene ¹⁸O and Mg and Sr records from Lakes Salpetén and Petén Itzá, Guatemala were apparently affected by drainage basin vegetation changes that influenced watershed hydrology, thereby confounding paleoclimatic interpretations. Oxygen isotope values and trace element concentrations in the two lowland lakes were greatest between ~ 9000 and 6800 ¹⁴C-yr BP, suggesting relatively high E/P, but pollen data indicate moist conditions and extensive forest cover in the early Holocene. The discrepancy between pollen- and geochemically-inferred climate conditions may be reconciled if the high early Holocene ¹⁸O and trace element values were controlled principally by low surface runoff and groundwater flow to the lake, rather than high E/P. Dense forest cover in the early Holocene would have increased evapotranspiration and soil moisture storage, thereby reducing delivery of meteoric water to the lakes. Carbonate ¹⁸O and Mg and Sr decreased between 7200 and 3500 ¹⁴C-yr BP in Lake Salpetén and between 6800 and 5000 ¹⁴C-yr BP in Lake Petén Itzá. This decline coincided with palynologically documented forest loss that may have led to increased surface and groundwater flow to the lakes. In Lake Salpetén, minimum ¹⁸O values (i.e., high lake levels) occurred between 3500 and 1800 ¹⁴C-yr BP. Relatively high lake levels were confirmed by ¹⁴C-dated aquatic gastropods from subaerial soil profiles ~ 1.0–7.5 m above present lake stage. High lake levels were a consequence of lower E/P and/or greater surface runoff and groundwater inflow caused by human-induced deforestation.  相似文献   

Water isotopic and hydrochemical evolution of a lake chain in the northern Great Plains and its paleoclimatic implications   总被引：2，自引：2，他引：0  

Zicheng Yu  Emi Ito  Daniel R. Engstrom 《Journal of Paleolimnology》2002,28(2):207-217

Oxygen isotopes and geochemistry from lake sediments are commonly used as proxies of past hydrologic and climatic conditions, but the importance of present-day hydrologic processes in controlling these proxies are sometimes not well established and understood. Here we use present-day hydrochemical data from 13 lakes in a hydrologically connected lake chain in the northern Great Plains (NGP) to investigate isotopic and solute evolution along a hydrologic gradient. The ¹⁸O and ²H of water from the chain of lakes, when plotted in ²H - ¹⁸O space, form a line with a slope of 5.9, indicating that these waters fall on an evaporation trend. However, 10 of the 13 lakes are isotopically similar (¹⁸O = –6 ± 1 VSMOW) and show no correlation with salinity (which ranges from 1 to 65). The lack of correlation implies that the isotopic composition of various source waters rather than in-lake evaporation is the main control of the ¹⁸O of the lakes. Groundwater, an important input in the water budget of this chain of lakes, has a lower ¹⁸O value (–16.7 in 1998) than that of mean annual precipitation (–11) owing to selective recharge from snow melt. For the lakes in this chain with salinity < 15, the water Mg/Ca ratios are strongly correlated with salinity, whereas Sr/Ca is not. The poor correlation between Sr/Ca and salinity results from uptake of Sr by endogenic aragonite. These new results indicate that ¹⁸O records may not be interpreted simply in term of climate in the NGP, and that local hydrology needs to be adequately investigated before a meaningful interpretation of sedimentary records can be reached.  相似文献   

Short-Period Waves That Heat the Corona Detected at the 1999 Eclipse     

Pasachoff  Jay M.  Babcock  Bryce A.  Russell  Kevin D.  Seaton  Daniel B. 《Solar physics》2002,207(2):241-257

As a part of a study of the cause of solar coronal heating, we searched for high-frequency (1 Hz) intensity oscillations in coronal loops in the [Fexiv] coronal green line. We summarize results from observations made at the 11 August 1999 total solar eclipse from Râmnicu-Vâlcea, Romania, through clear skies. We discuss the image reduction and analysis through two simultaneous series of coronal CCD images digitized at 10 Hz for a total time of about 140 s. One series of images was taken through a 3.6 Å filter isolating the 5303 Å[Fexiv] coronal green line and the other through a 100 Å filter in the nearby K-corona continuum. Previous observations, described in Pasachoff et al. (2000), showed no evidence for oscillations in the [Fexiv] green line at a level greater than 2% of coronal intensity. We describe several improvements made over the 1998 eclipse that led to increased image clarity and sensitivity. The corona was brighter in 1999 with the solar maximum, further improving the data. We use Fourier analysis to search in the [Fexiv] channel for intensity oscillations in loops at the base of the corona. Such oscillations in the 1-Hz range are predicted as a result of density fluctuations from the resonant absorption of MHD waves. The dissipation of a significant amount of mechanical energy from the photosphere into the corona through this mechanism could provide sufficient energy to heat the corona. A Monte Carlo model of the data suggests the presence of enhanced power, particularly in the 0.75–1.0 Hz range, and we conclude that MHD waves remain a viable method for coronal heating.  相似文献   

Analyses of organic and inorganic contaminants in Salton Sea fish   总被引：3，自引：0，他引：3  

Riedel R  Schlenk D  Frank D  Costa-Pierce B 《Marine pollution bulletin》2002,44(5):403-411

Chemical contamination of fish from the Salton Sea, a quasi-marine lake in Southern California, could adversely impact millions of birds using the Pacific Flyway and thousands of humans using the lake for recreation. Bairdiella icistia (bairdiella), Cynoscion xanthulus (orangemouth corvina), and Oreochromis spp. (tilapia) were sampled from two river mouths and two nearshore areas of the Salton Sea. Muscle tissues were analyzed for a complete suite of 14 trace metals and 53 pesticides. Fish muscle tissues had concentrations of selenium ranging between 1.89 and 2.73 microg/g wet weight. 4,4'-DDE accounted for 94% of the total DDT metabolites. Total DDTs ranged between 17.1 and 239.0 and total PCBs between 2.5 and 18.6 ng/g wet weight. PCB congeners 132, 138, 153, 168, and 180 comprised over 50% of the total PCBs. Given the potential implementation of a commercial fishing at the Salton Sea in the future, the presence of persistent organic pollutants and selenium warrants further research into the effects of these mixtures on fish populations, and on wildlife and humans consuming fish.  相似文献   

一次过冷层状云催化云迹微物理特征的卫星遥感分析   总被引：5，自引：2，他引：5  

戴进  余兴  Daniel Rosenfel  徐小红 《气象学报》2006,64(5):622-630

利用卫星反演技术,通过卫星观测到的一次人工增雨催化作业后形成的云迹线个例,分析了云迹线与其周围云的光谱特征、亮温、亮温差、云顶粒子有效半径等云微物理特征,比较了它们之间的差异,揭示了这次过冷层状云催化的微物理效应。云迹实际上是持续时间超过80 min、宽和深分别约为14 km和1.5 km的云谷。云迹周围的云顶粒子有效半径为10—15μm,而云沟内的粒子在15—24μm变化。周围云体由过冷滴组成,中间可能夹杂了一些低浓度的冰粒子,云沟内云的主要成分是冰。和周围未被催化的云相比,0.6μm通道的光谱反射率,在云沟处有明显的增加,而3.7μm通道反射率在云沟内是降低的,尽管其绝对变化幅度不大,但其相对变化幅度较大。随着播云时间的增加,云沟深度、宽度逐渐增加,云沟内和周围云体的温差逐渐增加,对通道4和5而言,在最早催化部位,最大分别达到4.2℃和3.9℃,4和5通道之间云沟内的亮温差也是随冰晶化时间的增加而增加,最大为1.4℃,而云沟周围云为0.2—0.4℃。云沟的形成、云沟内云顶温度的增加和4,5通道之间亮温差的增加,都足以说明被播云体变薄,其原因是由于云顶降水使得云内的水流失,云顶下降。云顶冰晶化、冰粒子增长成降水造成云顶下沉,是云沟形成的主要原因。对于本次播云作业,晶化作用在播云22 min后逐渐显现。在播云后38—63 min,有新的水云在云沟的中间部位生成,可能是由于冻结潜热释放引起的上升运动所致。而新生水云在形成较早的云迹中没有出现,这些较早形成的云迹在80多分钟的整个观测期间持续扩散。最终,在周围云从外向云沟内的扩散过程中,云沟开始消散。  相似文献   

Eruptive history and petrologic evolution of the Albano multiple maar (Alban Hills, Central Italy)     

Carmela Freda  Mario Gaeta  Daniel B. Karner  Fabrizio Marra  Paul R. Renne  Jacopo Taddeucci  Piergiorgio Scarlato  John N. Christensen  Luigi Dallai 《Bulletin of Volcanology》2006,68(6):567-591

A comprehensive volcanological study of the Albano multiple maar (Alban Hills, Italy) using (i) ⁴⁰Ar/³⁹Ar geochronology of the most complete stratigraphic section and other proximal and distal outcrops and (ii) petrographic observations, phase analyses of major and trace elements, and Sr and O isotopic analyses of the pyroclastic deposits shows that volcanic activity at Albano was strongly discontinuous, with a first eruptive cycle at 69±1 ka producing at least two eruptions, and a second cycle with two peaks at 39±1 and 36±1 ka producing at least four eruptions. Contrary to previous studies, we did not find evidence of magmatic or hydromagmatic eruptions younger than 36±1 ka. The activity of Albano was fed by a new batch of primary magma compositionally different from that of the older activity of the Alban Hills; moreover, the REE and ⁸⁷Sr/⁸⁶Sr data indicate that the Albano magma originated from an enriched metasomatized mantle. According to the modeled liquid line of descent, this magma differentiated under the influence of magma/limestone wall rock interaction. Our detailed eruptive and petrologic reconstruction of the Albano Maar evolution substantiates the dormant state of the Alban Hills Volcanic District. Electronic Supplementary Material Supplementary material is available for this article at Editorial responsibility: J. Donnelly-Nolan An erratum to this article can be found at  相似文献   

Impact of storm runoff from tropical watersheds on coastal water quality and productivity     

E. Heinen De Carlo  Daniel J. HooverCharles W. Young  Rebecca S. HooverFred T. Mackenzie 《Applied Geochemistry》2007

Storm runoff in the steep watersheds in Hawaii leads to sediment and freshwater pulses to coastal waters that quickly affect nearshore water quality. This is particularly true in semi-enclosed embayments, such as Kaneohe Bay, Oahu, where water has a relatively long residence time compared to more open coastal areas of the islands. In this paper the authors discuss water quality and productivity in Kaneohe Bay after back-to-back rain events in late November and early December 2003, following a particularly dry summer. The short-term biogeochemical response of coastal waters and the ecosystem to runoff and physical forcing was evaluated through a combination of continuous in situ measurements and adaptive synoptic sampling carried out on a variety of temporal and spatial scales.  相似文献   

Analysis and modeling of the seasonal South China Sea temperature cycle using remote sensing   总被引：1，自引：0，他引：1  

Daniel J. Twigt  Erik D. De Goede  Ernst J. O. Schrama  Herman Gerritsen 《Ocean Dynamics》2007,57(4-5):467-484

The present paper describes the analysis and modeling of the South China Sea (SCS) temperature cycle on a seasonal scale. It investigates the possibility to model this cycle in a consistent way while not taking into account tidal forcing and associated tidal mixing and exchange. This is motivated by the possibility to significantly increase the model’s computational efficiency when neglecting tides. The goal is to develop a flexible and efficient tool for seasonal scenario analysis and to generate transport boundary forcing for local models. Given the significant spatial extent of the SCS basin and the focus on seasonal time scales, synoptic remote sensing is an ideal tool in this analysis. Remote sensing is used to assess the seasonal temperature cycle to identify the relevant driving forces and is a valuable source of input data for modeling. Model simulations are performed using a three-dimensional baroclinic-reduced depth model, driven by monthly mean sea surface anomaly boundary forcing, monthly mean lateral temperature, and salinity forcing obtained from the World Ocean Atlas 2001 climatology, six hourly meteorological forcing from the European Center for Medium range Weather Forecasting ERA-40 dataset, and remotely sensed sea surface temperature (SST) data. A sensitivity analysis of model forcing and coefficients is performed. The model results are quantitatively assessed against climatological temperature profiles using a goodness-of-fit norm. In the deep regions, the model results are in good agreement with this validation data. In the shallow regions, discrepancies are found. To improve the agreement there, we apply a SST nudging method at the free water surface. This considerably improves the model’s vertical temperature representation in the shallow regions. Based on the model validation against climatological in situ and SST data, we conclude that the seasonal temperature cycle for the deep SCS basin can be represented to a good degree. For shallow regions, the absence of tidal mixing and exchange has a clear impact on the model’s temperature representation. This effect on the large-scale temperature cycle can be compensated to a good degree by SST nudging for diagnostic applications.  相似文献