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1.
Radiotracer 210Pb and contaminant copper were used to estimate sediment accumulation rates in 4 cores from the Ajkwa River estuary and mangrove tidal channels in western Irian Jaya. Mass accumulation rates (4.5–13 kg dry wt m−2 yr−1) were within the envelope of expectations for a region of high rainfall, great river catchment relief, and rapid tectonic uplift of mountains. Copper accumulation rates were enhanced 40 fold in surface sediments, compared to pre-1950 sections of the sediment cores. These recent sediments with enhanced copper concentrations come from Freeport Indonesia mine tailings over the last 27 years. Variations in sediment core profiles of Al, Fe, and organic carbon were small, indicating no great change in bulk sediment composition. Sulfur concentrations decline toward the sediment surface, suggesting a decline in rates of microbial sulfate reduction. Enhanced sediment copper concentrations will be a useful tracer of sediment dispersal from the Ajkwa River estuary along this coast.  相似文献   

2.
The effect of changes in rainfall event characteristics on urban stormwater quality, which was described by total suspended solids (TSS), was studied by means of computer simulations conducted with the Storm Water Management Model for a climate change scenario for northern Sweden. The simulation results showed that TSS event loads depended mainly on rainfall depth and intensity, but not on antecedent conditions. Storms with low‐to‐intermediate depths and intensities showed the highest sensitivity to changes in rainfall input, both for percentage and absolute changes in TSS wash‐off loads, which was explained by the contribution of pervious areas and supply limitations. This has significant implications for stormwater management, because those relatively frequent events generally carry a high percentage of the annual pollutant load. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

3.
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4.
The objective of this study was to evaluate whether indicator microbes and physical–chemical parameters were correlated with pathogens within a tidally influenced Estuary. Measurements included the analysis of physical–chemical parameters (pH, salinity, temperature, and turbidity), measurements of bacterial indicators (enterococci, fecal coliform, Escherichia coli, and total coliform), viral indicators (somatic and MS2 coliphage), viral pathogens (enterovirus by culture), and protozoan pathogens (Cryptosporidium and Giardia). All pathogen results were negative with the exception of one sample which tested positive for culturable reovirus (8.5 MPN/100 L). Notable physical–chemical parameters for this sample included low salinity (<1 ppt) and high water temperature (31 °C). Indicator bacteria and indicator virus levels for this sample were within average values typically measured within the study site and were low in comparison with levels observed in other freshwater environments. Overall results suggest that high levels of bacterial and viral indicators were associated with low salinity sites.  相似文献   

5.
Although urban wet weather discharges may have elevated concentrations of fecal indicator bacteria impacting water quality at swimming beaches, not all of these bacteria may arise from human sources. In this study, the contribution of non-human fecal indicator bacteria was quantified by sampling coastal reference beaches in southern California. Samples were collected at beaches near stormwater discharges from undeveloped watersheds and analyzed for total coliform, Escherichia coli, and enterococci. Surfzone samples exceeded water quality thresholds >10 times more frequently during wet weather than dry weather. Exceedences were greatest <24 h following rainfall, then steadily declined on successive days. Early season storms exceeded thresholds more frequently, and by greater magnitude, compared to late season storms. Large storms exceeded thresholds more frequently than smaller-sized storms, partly due to the breaching of sand berms. When discharges did reach the surf zone, bacterial concentrations in the wave wash were correlated with watershed bacterial flux.  相似文献   

6.
The deposition record of 137Cs was traced in the SE Black Sea sediments adjacent to the Coruh river mouth in comparison with the earlier studied chronology of 137Cs deposition in front of the Danube delta (NW Black Sea). In both cases, the 137Cs profiles showed two subsurface peaks attributable to maximum fallout of ‘bomb’ and Chernobyl radionuclides. The Coruh profile revealed a larger contribution of ‘bomb’ 137Cs in comparison with the Chernobyl input, suggesting different coverage of NW and SE Black Sea regions with the Chernobyl fallout. The 137Cs-derived dating showed that maximum deposition of particulate bound 137Cs in sediments adjacent to the Coruh river mouth was delayed for 14 yr relative to date of Chernobyl accident, reflecting a buffer effect of the watershed soils. This transit time is 3 times longer than in the Danube catchment area, indicating a difference in retention processes in these mountainous (Coruh) and lowland (Danube) river basins. The 137Cs profile in Coruh sediments showed penetration of 137Cs to much greater depth than would be expected from 137Cs fallout chronology, suggesting the sediment mixing rate of 1.3 cm2 yr−1. This value was used to evaluate deposition chronology of 137Cs, applying the model developed for pulse fallout case. Comparing the measured and modelled data has allowed differentiation of the flood-induced discharge of the 137Cs-containing suspended matter and the slower transit of eroded soil particles from the contaminated catchment areas. The obtained results may be used for the prediction of period when the pollutants, deposited over the river basins, can reach the Black Sea.  相似文献   

7.
Optical properties of colored dissolved organic matter (CDOM) were measured as a tracer of polluted waters in a Southern California surf-zone with consistently high levels of fecal indicator bacteria. Salinity, temperature, fecal coliform, absorbance (200-700nm) and fluorescence (lambda(excitation)=350nm; lambda(emission)=360-650nm) were measured in the creek and surf-zone during a dry and rain event. Fluorescence to absorption ratios for CDOM were used to distinguish water masses, with two distinct CDOM end-members identified as creek (flu/abs=8.7+/-0.8x10(4)) and coastal (flu/abs=2.2+/-0.3x10(4)). Waters containing the same CDOM end-member had highly variable bacterial levels during the dry event, suggesting intermittent sources of bacteria added to a uniform water source, consistent with marine birds. During the rain event, increased levels of the creek end-member and bacteria indicated a second bacteria source from runoff.  相似文献   

8.
Surface partial pressure of CO2 (pCO2), temperature, salinity, nutrients, and chlorophyll a were measured in the East China Sea (ECS; 31°30′–34°00′N to 124°00′–127°30′E) in August 2003 (summer), May 2004 (spring), October 2004 (early fall), and November 2005 (fall). The warm and saline Tsushima Warm Current was observed in the eastern part of the survey area during four cruises, and relatively low salinity waters due to outflow from the Changjiang (Yangtze River) were observed over the western part of the survey area. Surface pCO2 ranged from 236 to 445 μatm in spring and summer, and from 326 to 517 μatm in fall. Large pCO2 (values >400 μatm) occurred in the western part of the study area in spring and fall, and in the eastern part in summer. A positive linear correlation existed between surface pCO2 and temperature in the eastern part of the study area, where the Tsushima Warm Current dominates; this correlation suggests that temperature is the major factor controlling surface pCO2 distribution in that area. In the western part of the study area, however, the main controlling factor is different and seasonally complex. There is large transport in this region of Changjiang Diluted Water in summer, causing low salinity and low pCO2 values. The relationship between surface pCO2 and water stability suggests that the amount of mixing and/or upwelling of CO2-rich water might be the important process controlling surface pCO2 levels during spring and fall in this shallow region. Sea–air CO2 flux, based on the application of a Wanninkhof [1992. Relationship between wind speed and gas exchange over the ocean. Journal of Geophysical Research 97, 7373–7382] formula for gas transfer velocity and a set of monthly averaged satellite wind data, were −5.04±1.59, −2.52±1.81, 1.71±2.87, and 0.39±0.18 mmol m−2 d−1 in spring, summer, early fall, and fall, respectively, in the northern ECS. The ocean in this study area is therefore a carbon sink in spring and summer, but a weak source or in equilibrium with the atmosphere in fall. If the winter flux value is assumed to have been the mean of autumnal and vernal values, then the northern ECS absorbs about 0.013 Pg C annually. That result suggests that the northern ECS is a net sink for atmospheric CO2, a result consistent with previous studies.  相似文献   

9.
The characteristics of chromophoric dissolved organic matter (CDOM) were studied in Hudson Bay and Hudson Strait in the Canadian Arctic. Hudson Bay receives a disproportionately large influx of river runoff. With high dissolved organic matter (DOM) concentrations in Arctic rivers the influence of CDOM on coastal and ocean systems can be significant, yet the distribution, characteristics and potential consequences of CDOM in these waters remain unknown. We collected 470 discrete water samples in offshore, coastal, estuarine and river waters in the region during September and October 2005. Mixing of CDOM appeared conservative with salinity, although regional differences exist due to variable DOM composition in the rivers discharging to the Bay and the presence of sea-ice melt, which has low CDOM concentrations and low salinity. There were higher concentrations of CDOM in Hudson Bay, especially in coastal waters with salinities <28<28, due to river runoff. Using CDOM composition of water masses as a tracer for the freshwater components revealed that river runoff is largely constrained to nearshore waters in Hudson Bay, while sea-ice melt is distributed more evenly in the Bay. Strong inshore–offshore gradients in the bio-optical properties of the surface waters in the Hudson Bay cause large variation in penetration of ultraviolet radiation and the photic depth within the bay, potentially controlling the vertical distribution of biomass and occurrence of deep chlorophyll maxima which are prevalent only in the more transparent offshore waters of the bay. The CDOM distribution and associated photoprocesses may influence the thermodynamics and stratification of the coastal waters, through trapping of radiant heating within the top few meters of the water column. Photoproduction of biologically labile substrates from CDOM could potentially stimulate the growth of biomass in Hudson Bay coastal waters. Further studies are needed to investigate the importance of terrestrial DOM in the Hudson Bay region, and the impact of hydroelectric development and climate change on these processes.  相似文献   

10.
Refractive indices of incompletely hydrated tephra glasses vary widely. Thus, glass refractive index is not a practical indicator for identifying Holocene tephras. Hydration near the surface of tephra glass shards can be removed by either hydrofluoric acid treatment or annealing for 12 h at 400°C. The annealing procedure is a particularly reliable and simple way to dehydrate tephra glasses. Standard deviations (s) of refractive indices for glasses after 12 h annealing are small (s=0.0014–0.0018), in contrast with untreated glasses (s=0.0034–0.0405). The refractive indices of dehydrated tephra glasses are 0.006–0.014 lower than those of the untreated (hydrated) glasses. Using the 400°C 12-h annealing procedure, values for the refractive indices of eight Holocene tephras in Hokkaido were obtained. These refractive indices are useful indicators for identification and correlation of Holocene tephras.  相似文献   

11.
The geopotential value of W 0 = (62 636 855.611 ± 0.008) m 2 s –2 which specifies the equipotential surface fitting the mean ocean surface best, was obtained from four years (1993 - 1996) of TOPEX/POSEIDON altimeter data (AVISO, 1995). The altimeter calibration error limits the actual accuracy of W 0 to about (0.2 - 0.5) m 2 s –2 (2 - 5) cm. The same accuracy limits also apply to the corresponding semimajor axis of the mean Earth's level ellipsoid a = 6 378 136.72 m (mean tide system), a = 6 378 136.62 m (zero tide system), a = 6 378 136.59 m (tide-free). The variations in the yearly mean values of the geopotential did not exceed ±0.025 m 2 s –2 (±2.5 mm).  相似文献   

12.
In the summer of 2001, a coastal ocean measurement program in the southeastern portion of San Pedro Bay, CA, was designed and carried out. One aim of the program was to determine the strength and effectiveness of local cross-shelf transport processes. A particular objective was to assess the ability of semidiurnal internal tidal currents to move suspended material a net distance across the shelf. Hence, a dense array of moorings was deployed across the shelf to monitor the transport patterns associated with fluctuations in currents, temperature and salinity. An associated hydrographic program periodically monitored synoptic changes in the spatial patterns of temperature, salinity, nutrients and bacteria. This set of measurements show that a series of energetic internal tides can, but do not always, transport subthermocline water, dissolved and suspended material from the middle of the shelf into the surfzone. Effective cross-shelf transport occurs only when (1) internal tides at the shelf break are strong and (2) subtidal currents flow strongly downcoast. The subtidal downcoast flow causes isotherms to tilt upward toward the coast, which allows energetic, nonlinear internal tidal currents to carry subthermocline waters into the surfzone. During these events, which may last for several days, the transported water remains in the surfzone until the internal tidal current pulses and/or the downcoast subtidal currents disappear. This nonlinear internal tide cross-shelf transport process was capable of carrying water and the associated suspended or dissolved material from the mid-shelf into the surfzone, but there were no observation of transport from the shelf break into the surfzone. Dissolved nutrients and suspended particulates (such as phytoplankton) transported from the mid-shelf into the nearshore region by nonlinear internal tides may contribute to nearshore algal blooms, including harmful algal blooms that occur off local beaches.  相似文献   

13.
The tropical river ocean processes in coastal settings (TROPICS) program in Indonesia (Indotropics) was carried out in the Mamberamo estuary on May–June 1999 and August 2000. The Mamberamo River flows northward from the high mountains of West Papua to the narrow and steep continental slope of the Pacific Ocean. The data for the 1999 Mamberamo estuary cruises show the dispersal of fresh water coming out of the Mamberamo River into the Bismarck Sea, and the plume is clearly defined by the pattern of salinity, turbidity, and nutrient distribution. The Mamberamo River and other nearby rivers supply high concentrations of phosphate and nitrate to the New Guinea Coastal Current, so that nutrient concentrations are higher in the surface estuarine plume, compared to offshore areas. The distribution of fishes and benthic animals were also sampled over this area.  相似文献   

14.
Hydrogen peroxide is photochemically produced in natural waters. It has been implicated in the oxidative-induced mortality of fecal indicator bacteria (FIB), a microbial water quality measure. To assess levels and cycling of peroxide in beach waters monitored for FIB, diel studies were carried out in surf zone waters in July 2009 at Crystal Cove State Beach, Southern California, USA. Maximum concentrations of 160–200 nM were obtained within 1 h of solar noon. Levels dropped at night to 20–40 nM, consistent with photochemical production from sunlight. Day-time production and night-time dark loss rates averaged 16 ± 3 nM h−1 and 12 ± 4 nM h−1 respectively. Apparent quantum yields averaged 0.07 ± 0.02. Production was largely dominated by sunlight, with some dependence on chromophoric dissolved organic matter (CDOM) levels in waters with high absorption coefficients. Peroxide levels measured here are sufficient to cause oxidative-stress-induced mortality of bacteria, affect FIB diel cycling and impact microbial water quality in marine bathing waters.  相似文献   

15.
During four surveys at spring and neap tides in July and November 2005, continuous observations were conducted at four stations adjacent to the Changjiang (Yangtze River) mouth. The observation times lasted for 26 h that covered two consecutive semidiurnal cycles. Resuspension events and subsequently enhancements of suspended particulate matter (SPM) were commonly observed within a tidal cycle. Although nutrients (SiO32−, NO3−, and PO43−) were primarily governed by salinity, their statistically significant correlations with SPM could always be extracted after partial correlation analysis. Three parameter (salinity, SPM, nutrients) regressions generally produced better results of simulating nutrient concentrations than two parameter (salinity and nutrients) regressions, although compared to the latter, the former R2 values were elevated by no more than 13%. The partial correlation between SPM and a specific nutrient could be either positive or negative in different surveys, suggesting SPM influenced the nutrients in different ways under various conditions. The minor (albeit statistically significant) impacts of highly dynamic SPM on nutrients might be ascribed to the short duration time of resuspension events and estuarine mixing process, together with the complex nature of circulation in the Changjiang plume seawater.  相似文献   

16.
Satellite ocean color and surface salinity data are used to characterize the space–time variability of the Río de la Plata plume. River outflow and satellite wind data are also used to assess their combined effect on the plume spreading over the Southwestern South Atlantic continental shelf. Over the continental shelf satellite-derived surface chlorophyll-a (CSAT) estimated by the OC4v4 SeaWiFS retrieval algorithm is a good indicator of surface salinity. The log (CSAT) distribution over the shelf presents three distinct modes, each associated to: Subantarctic Shelf Water, Subtropical Shelf Water and Plata Plume water. The log (CSAT) 0.4–0.8 range is associated with a sharp surface salinity transition across the offshore edge of the Plata plume from 28.5 to 32.5. Waters of surface salinity <31, derived from mixtures of Plata waters with continental shelf waters, are associated to log (CSAT)>0.5. In austral winter CSAT maxima extend northeastward from the Plata estuary beyond 30°S. In summer the high CSAT waters along the southern Brazil shelf retreat to 32°S and extend south of the estuary to about 37.5°S, only exceeding this latitude during extraordinary events. The seasonal CSAT variations northeast of the estuary are primarily controlled by reversals of the along-shore wind stress and surface currents. Along-shore wind stress and CSAT variations in the inner and mid-shelves are in phase north of the estuary and 180° out of phase south of the estuary. At interannual time scales northernmost Plata plume penetrations in winter (∼1200 km from the estuary) are associated with more intense and persistent northeastward wind stress, which in the period 2000–2003, prevailed over the shelf south of 26°S. In contrast, in winter 1999, 2004 and 2005, characterized by weaker northeastward wind stress, the plume only reached between 650 and 900 km. Intense southwestward plume extensions beyond 38°S are dominated by interannual time scales and appear to be related to the magnitude of the river outflow. The plume response to large river outflow fluctuations observed at interannual time scales is moderate, except offshore from the estuary mouth, where outflow variations lead CSAT variations by about 2 months.  相似文献   

17.
Yonghui Yang  Fei Tian   《Journal of Hydrology》2009,374(3-4):373-383
Runoff in Haihe River Catchment of China is steadily declining due to climate change and human activity. Determining abrupt changes in runoff could enhance identification of the main driving factors for the sudden changes. In this study, the sequential Mann–Kendall test analysis is used to determine abrupt changes in runoff in eight sub-catchments of Haihe River Catchment, while trend analysis via the traditional Mann–Kendall test for the period 1960–1999 is used to identify the basic trend of precipitation and runoff. The results suggest an insignificant change in precipitation and a significant decline in runoff in five of the eight sub-catchments. For most of the sub-catchments, abrupt changes in runoff occurred in 1978–1985. Through correlation comparisons for precipitation and runoff for the periods prior to and after abrupt runoff changes, human activity, rather than climatic change, is identified as the main driving factor of runoff decline. It is also noted that abrupt decline in runoff was actually at the beginning of China’s 1978–1985 land reform. Given that the land reform motivated farmers to productively manage their reallocated lands, agricultural water use therefore increased. Hence percent agricultural land is analyzed in relation to land use/cover pattern for the late 1970s and early 1980s. The analysis shows that when cultivated farmland exceeds 25% of a sub-catchment area, an abrupt decline in runoff occurs. It is therefore concluded that high percent agricultural land and related agricultural water use are the most probable driving factors of runoff decline in the catchment.  相似文献   

18.
Riverine freshwater plumes are the major transport mechanism for nutrients, sediments and pollutants into the Great Barrier Reef (GBR) lagoon and connect the land with the receiving coastal and marine waters. Knowledge of the variability of the freshwater extent into the GBR lagoon is relevant for marine park management to develop strategies for improving ecosystem health and risk assessments. In this study, freshwater extent has been estimated for the entire GBR lagoon area from daily satellite observations of the Moderate Resolution Imaging Spectroradiometer (MODIS) between 2002 and 2010. To enable a reliable mapping of freshwater plumes we applied a physics-based coastal ocean colour algorithm, that simultaneously retrieves chlorophyll-a, non-algal particulate matter and coloured dissolved organic matter (CDOM), from which we used CDOM as a surrogate for salinity (S) for mapping the freshwater extent.  相似文献   

19.
A sewer main serving a large municipal wastewater system ruptured, discharging approximately 3,000,000 gallons (11,355,000 L) of raw human sewage into a multi-branched tidal creek estuary along the US East Coast. The biochemical oxygen demand caused severe hypoxia in the system, causing a large fish kill. The sewage load led to high fecal coliform bacteria concentrations in the creek (maximum of 270,000 CFU 100ml(-1)), which declined in an approximate logarithmic manner over the first few days. The spill caused elevated sediment fecal coliform bacteria and enterococcus counts that declined much more gradually than water column counts. Persistence of relatively high concentrations of fecal indicator bacteria in sediments for several weeks after the spill suggests that sediment sampling should be included in response to major sewage spills. The high concentration of nutrients in the spilled sewage led to several algal blooms. However, nutrient concentrations in the water column declined rapidly, demonstrating the value of conserving marshes because of their pollutant filtration function.  相似文献   

20.
The temporal variations in the chemical and isotopic compositions of urban stormwater under different land uses, and their dependence on physical parameters such as precipitation intensity, stormwater discharge, cumulative stormwater volumes and the size of the drainage area, were investigated in the coastal city of Ashdod, Israel. During 2000/2001 and 2001/2002, 46 stormwater events were intensively monitored for precipitation distribution and intensity at three stations across the city, and for stormwater discharge at seven stations draining 85% of the city area. Sixty-eight and 202 precipitation samples were collected and analyzed for chemical and isotopic compositions, respectively, as were 186 stormwater samples, collected from the drains during 15 of the 46 events. Land use had only a minor effect on the concentrations of major ions and trace elements. Conversely, the concentrations and variety of volatile and semi-volatile organic compounds were significantly higher in stormwater generated in the industrial area than in that draining from residential areas. Ion and trace-metal concentrations were very low (below drinking-water standards) in 97% of the stormwater samples collected from all drains. Stormwater concentrations were higher at stations draining a larger area, thereby linking concentrations to the length of the stormwater flow paths. A first-flush effect was documented on both a seasonal and event basis for both ions and trace elements. The high concentrations of fecal coliform bacteria exceeded the drinking-water standards and displayed a random pattern. The isotopic ratios of oxygen and hydrogen in the stormwater suggest very little exposure to the atmosphere, resulting in very limited fractionation. The presence of fecal coliforms, ammonium in some samples, and specific ratios of oxygen and nitrogen isotopes, suggest that although the sewer and stormwater-collection systems are separated, wastewater, possibly from overflowing sewers, contributed to the drained stormwater.  相似文献   

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