首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 578 毫秒
1.
Between January 1978 and September 1979 samples of subsurface (1 m) water and surface sediment were collected from sites in the North Sea, English Channel, Irish Sea and a number of estuarine areas. These have been analysed by fluorescence spectroscopy (UVF) in order to provide information on the levels of hydrocarbons generally present in UK marine waters.Total hydrocarbon concentrations (THCs) of water samples ranged from 1.1–74 μg l.?1 Ekofisk crude oil equivalents, all values greater than 3.5 μg l.?1 occurring inshore. In offshore areas the mean THCs were: 1.3 μg l.?1 in the northern North Sea, 1.5 μg l.?1 in the western Channel, 2.5 μg l.?1 in the eastern Channel and southern North Sea, and 2.6 μg l.?1 in the Irish Sea.THCs of sediment samples ranged from 0.27–340 μ g?1 dry weight Ekofisk crude oil equivalents, the highest concentration being in the Queen's Channel, the main entrance to the River Mersey.  相似文献   

2.
Total arsenic concentrations have been measured in macroalgae specimens from two coastal areas of South Australia. Phaeophyta in both areas were found to contain elevated arsenic concentrations (42.2–179 μg g?1 and 26.3–65.3 μg g?1) relative to Rhodophyta (17.6–31.3 μg g?1 and 12.5–16.2 μg g?1) and Chlorophyta (6.3–16.3 μg g?1 and 9.9–10.8 μg g?1).  相似文献   

3.
Analysis of hexane-extractable hydrocarbons in zooplankton collected off Bermuda in August 1979, and their faecal pellets, gave an estimated removal rate of hydrocarbons from surface waters by ‘grazing’ of 16–46 μg m?2 for a 4 h period. With a number of assumptions, this can be translated to 8–23 mg m?2 yr?1. When compared to the annual input due to petroleum discharge in the currents feeding the Sargasso Sea (18–70 mg m?2 yr?1 hexane-extractable hydrocarbons), this result implies that zooplankton are an important factor in the short-term removal of petroleum residues from open ocean surface waters.  相似文献   

4.
A survey of waters adjacent to this heavily urbanized and industrialized region showed concentrations of copper, 65 μg l.?1 to be the highest reported to date for estuarine waters, and lead up to 13.9 μg l.?1 Correlations between distributions of dissolved and total metal concentration in the water column, hydrography, and metal in the sediment were related to benthic studies in this area. Laboratory studies are cited which show the potential for adverse effects on marine animals at these metal concentrations.  相似文献   

5.
The concentration of petroleum hydrocarbons in Arctic surface water under the ice north of Svalbard has been determined by fluorescence spectrofluorometry using three different excitation/emission wavelength combinations. With Kuwait crude oil as a reference, the concentration range is 0.1–0.6 μg l?1 crude oil equivalents with respect to light molecular weight components and 0.05–0.2 μg l?1 heavy molecular weight components.  相似文献   

6.
Biologically configured ββ-hopanes, geologically configured αβ-hopanes and the biogenic hopenes were determined in dated sediment cores from Lake Fuxian in SW China and Lake Changdang in Eastern China in order to investigate anthropogenic influences on the abundance, composition and provenance of hopanoid hydrocarbons in lake sediments. Based on the results, hopenes were prevalent, with maximum values reaching 148.9 μg g−1 TOC in sediments of Lake Fuxian, an oligotrophic deep lake (average depth 89.6 m), where the long water column provided ample potential for the growth of hopene-producing bacteria especially the cyanobacteria. Sediment hopenes have diminished in abundance to values of 13.4–78.5 μg g−1 TOC in Lake Changdang, a eutrophic shallow (average 0.8–1.2 m) body, reflecting comparatively reduced importance of nutrient level on hopene production. Historical trends in hopenes input to the sediments of each lake are strongly dependent on nutrient status. During the last few decades, human-induced eutrophication has greatly boosted bacterial production, enhancing the accumulation of hopenes in sediments. Inputs of petroleum-derived αβ-hopanes were exceptionally high (average 71.2 μg g−1 TOC) in post-1968 sediments from Lake Changdang, their increase coinciding with the advent and acceleration of petroleum product use around the lake, in particular by fishing boats. Lake Fuxian on the other hand, has undergone slower economic development and the appearance of petroleum-derived αβ-hopanes in sediments was delayed to 1990 since when the average value has been 27.1 μg g−1 TOC. The abundance of αβ-hopanes in Lake Changdang has created a marked decrease in the relative contribution of hopenes to total hopanoids since 1968. Conversely, the amounts of αβ-hopanes introduced to Lake Fuxian since 1990 has yet to yield a clear change in the overall proportion of hopenes, but the abundance of ββ-hopanes has declined relative to total hopanoid levels for the period.  相似文献   

7.
A database composed of 673 natural rainfall events with sediment concentration measurements at the field or plot scale was analysed. Measurements were conducted on similar soil type (loess soils prone to sealing phenomenon) to apprehend the variability and complexity involved in interrill erosion processes attributable to soil surface conditions. The effects of the dominant controlling factors are not described by means of equations; rather, we established a classification of potential sediment concentration domain according to combination of the dominant parameters. Thereby, significant differences and evolution trends of mean sediment concentration between the different parameter categories are identified. Further, when parameter influences interact, it allows us to discern the relative effects of factors according to their respective degree of expression. It was shown that crop cover had a major influence on mean sediment concentration, particularly when soil surface roughness is low and when maximum 6‐min intensity of rainfall events exceeds 10 mm h?1: mean sediment concentration decreases from 8·93 g l?1 for 0–20 per cent of coverage to 0·97 g l?1 for 21–60 per cent of coverage. The established classification also indicates that the increase of the maximum 6‐min intensity of the rainfall factor leads to a linear increase of mean sediment concentration for crop cover over 21 per cent (e.g. from 2·96 g l?1 to 14·44 g l?1 for the 1–5 cm roughness class) and to an exponential increase for low crop cover (e.g. from 3·92 g l?1 to 58·76 g l?1 for the 1–5 cm roughness class). The implication of this work may bring perspective for erosion prediction modelling and give references for the development of interrill erosion equation. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

8.
The composition of hydrocarbons (aliphatic and polycyclic aromatic) is studied in the surface layer of bottom sediments of the Ivankovo Reservoir. Their concentrations are found to be high both per dry mass and in the composition of Corg. The concentration range was 0.42 to 28.15% for Corg, 141.9 to 3451.8 μg/g for aliphatic hydrocarbons (0.2–51.2% Corg), and 28.2–9161 ng/g for polycyclic aromatic hydrocarbons ((0.04–6.58) × 10?3 % Corg). The distribution of hydrocarbons is shown to be determined not only by the lithologic type of sediments, but also by their input from petroleum and pyrogenic sources.  相似文献   

9.
Mercury（Hg） is well known as one of the most toxic elements to man.The coastal environments adjacent to industrial areas are reported to often be contaminated with mercury.Mercury becomes more toxic in the form of methylmercury（Me-Hg） which is converted from inorganic mercury in aqueous systems by microbial activity and can bio-magnify through the food chain.A simple method for the determination of total mercury and methylmercury in sediments was optimized by slightly modifying an old method using the direct mercury analyzer technique.Core sediment samples from Thane Creek,Mumbai,India were collected and analysed for total mercury and methylmercury.The Hg concentration in the creek varied between 0.54 to 16.03 μg g~（-1） while Me-Hg concentrations ranged between0.04 to 1.07 μg g~（-1）.In surface sediment,mercury concentrations ranged from 4.33 μg g~（-1） to 12.16μg g~（-1）.Total organic carbon content was found to be around 2 percent in different layers of the sediments.The enrichment factors,which indicate the extent of pollution in sediments,were estimated to range from 26 to 50 at different locations in the creek.Lithogenic and anthropogenic concentrations of mercury in the creek were also determined to compare the impact of anthropogenic and natural sources.Anthropogenic inventories were about 5-70 times more in concentration than the lithogenic in the different core sediments.  相似文献   

10.
Glacier recessions caused by climate change may uncover pro‐glacial lakes that form important sedimentation basins regulating the downstream sediment delivery. The impact of modern pro‐glacial lakes on fluvial sediment transport from three different Norwegian glaciers: Nigardsbreen, Engabreen and Tunsbergdalsbreen, and their long‐term development has been studied. All of these lakes developed in modern times in overdeepened bedrock basins. The recession of Nigardsbreen uncovered a 1.8 km long and on average 15 m deep pro‐glacial lake basin during 1937 to 1968. Since then the glacier front has been situated entirely on land, and the sediment input and output of the lake has been measured. The suspended sediment transport into and out of the lake averaged 11 730 t yr?1 and 2340 t yr?1 respectively. Thus, 20% remained in suspension at the outlet. The measured mean annual bedload supplied to the lake was 11 800 t yr?1, giving a total transport of 23 530 t yr?1 which corresponds to a specific sediment yield of 561 t km?2 yr?1. A 1.9 km long and up to 90 m deep pro‐glacial lake basin downstream from Engabreen glacier was uncovered during 1890 to 1944. The average suspended sediment load delivered from the glacier during the years 1970–1981 amounted to 12 375 t yr?1and the transport out of the lake was 2021 t yr?1, giving an average of 16% remaining in suspension. The mean annual bedload was 8000 t yr?1, thus the total transport was 20 375 t yr?1, giving a specific sediment yield of 566 t km?2 yr?1. For Tunsbergdalsbreen glacier, measurements in the early 1970s indicated that the suspended sediment transport was on average 44 000 t yr?1. From 1987 to 1993 the recession of the glacier uncovered a small pro‐glacial lake, 0.3 km long and around 9 m deep. Downstream from this, the suspended sediment load measured in 2009 was 28 000 t yr?1, indicating that as much as 64% remained in suspension. Flow velocity, grain size of sediment, and morphology of the lake are important factors controlling the sedimentation rate in the pro‐glacial lakes. A survey of the sub‐glacial morphology of Tunsbergdalsbreen revealed that there are several overdeepened basins beneath the glacier. The largest is 4 km long and 100 m deep. When the glacier melts back they will become lakes and act as sedimentation basins. Despite an expected increase in sediment yield from the glacier, little sediment will pass these lakes and downstream sediment delivery will be reduced markedly. Beneath Nigardsbreen there was only a small depression that may form a lake and the sediment delivery will not be significantly affected. © 2014 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.  相似文献   

11.
At present the concentrations of polycyclic aromatic hydrocarbons in sediments from the Great Barrier Reef are remarkably low. The baseline levels range from <0.01 μg kg?1 dry wt. for benzo(k)fluoranthene and benzo(a)pyrene to <0.82 μg kg?1 for chrysene. Measurable levels of polycyclic aromatic hydrocarbons have only been found in small areas close to sites frequently visited by power boats. Sediments from Townsville and Gladstone Harbours on the coast adjacent to the reef are polluted with polycyclic aromatic hydrocarbons to a similar degree to that reported for coastal sediments in similar locations in other parts of the world.  相似文献   

12.
A simple weighing method using carbon tetrachloride as solvent was used to survey the dissolved hydrocarbon and tarball levels in the area of the Egyptian Red Sea coast. The area of investigation covers the coastal area from Ras-Gharib down to the port of Qosier during the period from September 1979 to February 1981. This survey confirms the presence of extensive oil pollution in the area, especially at Ras-Gharib and Ras-Shukhair. Minimum concentrations were obtained at Ghardaqa where no dissolved hydrocarbons were detected (i.e. less than 10 μg l?1) in 1979–1980 but an increase to 20 μg l?1 in 1981 was recorded. The high levels of pollution recorded in the southern part of the Gulf of Suez are related to the presence of the offshore oil fields, most of which are located at Ras-Gharib.  相似文献   

13.
The nature and rates of fluvial and slope processes change over time and space as urbanized areas replace forested land in Singapore. Storm-based and time-based data, from undisturbed rainforests, heavily disturbed construction sites, urban grass-covered slopes and an experimental plot, are collected to observe the impact of rainwater on the soil moisture conditions, surface microtopography, runoff generation, sediment movement, and ground lowering in the three different categories of land use. The undisturbed forested environment is characterized by high throughfall (58% of total rainfall) and frequent negative soil moisture suctions. The slow and unconcentrated overland flow during heavy storms is restricted by the forest floor microtopography. No rills develop. Ground lowering is recorded as 3·2–3·4 mm a?1. But sediment movement is episodic and suspended sediment concentrations in overland flow are 172–222 mg l?1. During urban construction, gully development is rapid on the bare slopes, runoff generation, voluminous, and sediment-laden discharges (5200–75498 mg l?1) lead to sediment plumes at channel mouths. Ground lowering rates are measured at 132·4 mm a?1. Once grass-covered, runoff carries less suspended sediment (800 mg l?1) and ground lowering rates are reduced, but depend on the condition of the cover, ranging from 0·2 to 8·2 mm a?1. As urban development continues, environments are altered both in time as well as spatially.  相似文献   

14.
H. Marttila  B. Kløve 《水文研究》2014,28(17):4756-4765
Lowland catchments in Finland are intensively managed, promoting erosion and sedimentation that negatively affects aquatic environments. This study quantified fine‐grained bed sediment in the main channel and upstream headwaters of the River Sanginjoki (399.93 km2) catchment, Northern Finland, using remobilization sediment sampling during the ice‐free period (May 2010–December 2011). Average bed sediment storage in river was 1332 g m?2. Storage and seasonal variations were greater in small headwater areas (total bed sediment storage mean 1527 g m?2, range 122–6700 g m?2 at individual sites; storage of organic sediment: mean 414 g m?2, range 27–3159 g m?2) than in the main channel (total bed sediment storage: mean 1137 g m?2, range 61–4945 g m?2); storage of organic sediment: mean 329 g m?2, range 13–1938 g m?2). Average reach‐specific bed sediment storage increased from downstream to upstream tributaries. In main channel reaches, mean specific storage was 8.73 t km?1, and mean specific storage of organic sediment 2.45 t km?1, whereas in tributaries, it was 126.94 and 34.05 t km?1, respectively. Total fine‐grained bed sediment storage averaged 563 t in the main channel and 6831 t in the catchment. The proportion of mean organic matter at individual sites was 15–47% and organic carbon 4–455 g C m?2, with both being highest in small headwater tributaries. Main channel bed sediment storage comprised 52% of mean annual suspended sediment flux and stored organic carbon comprised 7% of mean annual total organic carbon load. This indicates the importance of small headwater brooks for temporary within‐catchment storage of bed sediment and organic carbon and the significance of fine‐grained sediment stored in channels for the suspended sediment budget of boreal lowland rivers. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

15.
Dissolved petroleum hydrocarbons were measured in some parts of the Northern Indian Ocean using UV absorbance technique with a clean up step. The concentration of oil ranged from 0.6 to 26.5 μg l?1. Higher values were recorded along the oil tanker route compared with the coastal region From surface to about 10 m depth the oil appeared to be well mixed with water.  相似文献   

16.
Concentrations of benzo[a]pyrene (BAP) were measured in subpopulations of softshell clams, Mya arenaria, from four intertidal sites in Coos Bay from June 1976 to June 1978. Subsequently, concentrations of 15 unsubstituted polynuclear aromatic hydrocarbons (PNAH) were determined in two subpopulations from September 1978 to August 1979. There were significant differences between BAP concentrations in clams from the four sites. For the two-year period, they were highest in clams inhabiting areas adjacent to the industrialized bayfront and lowest in clams inhabiting more remote areas. There were no significant seasonal variations in BAP concentrations during this period. During the 1978–1979 study, the average total PNAH concentration in clams from the bayfront area was 555.1 μg kg?1 compared to 76.3 μg kg?1 for clams from a more remote environment. In general, PNAH concentrations were lowest in the fall-winter and highest during the spring-summer.  相似文献   

17.
The coastal waters of Hong Kong constitute a transition from estuarine conditions in the west to more oceanic conditions in the east, with a major discharge of untreated sewage located at the mid-point. Chlorophyll a was determined and net phytoplankton was sampled at 45 stations throughout this transition. Over a period of 20 months, chlorophyll a values rarely exceeded 2 μg l.?1 in unpolluted coastal waters. Estuarine waters generally contained 2–6 μg l.?1 and, in waters influenced by sewage discharge, values sometimes exceeded 20 μg l.?1. There was no evidence of a reduction in taxonomic diversity in polluted areas except in summer, when the net phytoplankton was dominated by Chaetoceros spp. In the autumn and early winter, Skeletonema costatum was abundant in the central polluted areas.  相似文献   

18.
Gravel sediment freshly enriched with over 4.4 μg Cu g?1 significantly increased the burrowing and reburrowing times of Littleneck marine clams (Protothaca staminea). Abnormal burrowing behaviour was observed with time-lapse video. Aged (1 day) copper-enriched sediment did not affect clam burrowing time. Copper in sediment porewater declined three days after sediment enrichment to background levels without change in total sediment copper. In a long-term experiment, clams with increased burrowing time into copper-enriched sediment had up to 25% mortality after 12–29 days burial in the sediment. The majority of clam mortality was found in clams burrowing within the first 48 h. Over 7 weeks there was blackening of sediment and clam shells proportional to sediment copper enrichment.  相似文献   

19.
— The aims of this study were to estimate the total amount of mercury released to the environment during 60 years of gold mining (1867–1926) at Gympie, Queensland, Australia and to measure the mercury levels in soil samples surrounding the mining activity. We estimated that 1902 tonnes of mercury was released to the environment and about 1236 tonnes of which was released to the air. The mean mercury in the soil samples in the vicinity of the Scottish battery varied from 1.07 to 99.26 μg g?1 as compared to 0.075 μg g?1 as background mercury concentrations. The maximum mercury concentration measured in sediments of the Langton Gully was 6.12 μg g?1. These results show that large amount of mercury was used in this area during gold mining. Since mining is active in the area and Langton Gully flows into Mary River, we therefore, recommend that mercury concentration in air and fish should be monitored.  相似文献   

20.
Tissue cadmium and zinc levels in Steller sea lions have been analysed to elucidate the body distribution of these metals and their age-related accumulation. A significant correlation between age (0.7–8.8 year old) and renal and hepatic cadmium concentration was noted. Of the tissues examined, the kidney manifested the highest cadmium content (mean: 20.9 μg g?1 dry wt). A similar zinc distribution pattern was observed; its concentration was more uniform among tissues than that of cadmium. The tissue cadmium concentration in the Steller sea lion was lower than in other pinnipeds from various areas, possibly due to their feeding habits which may represent a major pathway of metal accumulation.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号