Relations Between Annual Dredging Activities, Suspended Matter Concentrations, and the Development of the Tidal Regime in the Ems Estuary

This paper challenges Kühl and Mann's suggestion (1973) that an increase in organic matter in the Ems Estuary between 1950 and 1970 caused a five- to tenfold increase in the turbidity in that period. Their hypothesis is refuted because: (a) during that period the discharge of organic matter via both the River Ems and the River Westerwoldsche A did not change significantly; (b) the increase in particulate organic carbon in the western Dutch Wadden Sea and possibly also in the Ems Estuary resulting from eutrophication of the North Sea by the River Rhine during 1950–70 is unlikely to have been more than twofold; and (c) Secchi-disc data do not support the five- to tenfold increase in turbidity. It is suggested that dredging is probably responsible for the increase in turbidity because the volume of material dredged annually increased fourfold between 1950 and 1970. The mean annual concentration of suspended matter increased by a factor ranging from 1.3 to 2.1 between 1954 and the period 1970 to 1979. The fluctuations in concentrations of suspended matter showed a statistically significant correlation with the distance dredged annually and not with the volume dredged annually. This indicated that the relation depended more on how "extensive" rather than on how "intensive" the dredging was. The fluctuations in concentrations of suspended matter are caused by the intensified erosion and sedimentation cycle that is initiated after the local natural equilibrium between channel morphology and current pattern is disturbed. This explanation is supported by the morphological changes that occurred in part of the study area between 1975 and 1979. Further support for this hypothesis was found in the changes of the tidal regime in the estuary. It is postulated that the complete cessation of dredging would probably be accompanied by the concentrations of suspended solids falling from the 1979 levels to values nearer those obtained in 1954. The biological implications of the processes described are discussed.Key words: dredging, suspended matter, tidal regime, Ems Estuary, turbidity

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Effects of Physicochemical Variables of Superficial Waters on the Abundance of the North African Freshwater Crab Potamon algeriense (Bott, 1967)

Journal of Toxicology ◽

10.1155/2021/6669919 ◽

2021 ◽

Vol 2021 ◽

pp. 1-13

Author(s):

Soufiane Fadlaoui ◽

Ouahid El Asri ◽

Mustapha Bouterfas ◽

Mohammed Melhaoui

Keyword(s):

Organic Matter ◽

Dissolved Oxygen ◽

Water Temperature ◽

Suspended Matter ◽

Mountain Stream ◽

Freshwater Crab ◽

Physicochemical Variables ◽

The North ◽

Global Quality ◽

Nitrite Nitrate

The large number of pollutants discharged into the aquatic environment may influence the physicochemical and biological qualities of the aquatic ecosystem. This study discloses the global quality of the surface waters and the effect of physicochemical variables on the abundance of the African freshwater crab Potamon algeriense inhabiting Zegzel watercourse, a mountain stream in the northeast of Morocco. Physicochemical variables including streamflow, water temperature, pH, dissolved oxygen, suspended matter, chloride, calcium, magnesium, ammonia, nitrite, nitrate, orthophosphate, and organic matter were evaluated monthly for one year (October 2017–September 2018). The evaluation of the physicochemical quality showed that the waters of all the stations studied are between the excellent and good quality classes concerning all the physicochemical variables and highlights also two variations with a tendency towards degradation, one spatial from upstream to downstream and the other seasonal from the wet to the dry period. The abundance of crabs was recorded to exhibit a positive correlation with dissolved oxygen, calcium (N = 44) (p < 0.01), and magnesium. However, a negative correlation has been noticed for streamflow (N = 1) (p < 0.01), water temperature, pH, suspended matter, chloride, ammonia, nitrite, nitrate, orthophosphate, and organic matter. The results obtained reveal that besides the biotic variables, the distribution of P. algeriense also depends on these specific environmental variables.

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Features of the Oceanological Values Fields in the Sivash Bay (The Sea of Azov)

Morskoy gidrofizicheskiy zhurnal ◽

10.22449/0233-7584-2021-6-696-709 ◽

2020 ◽

Vol 37 (6) ◽

Author(s):

P. D. Lomakin ◽

Keyword(s):

Organic Matter ◽

Dissolved Organic Matter ◽

Suspended Matter ◽

Water Area ◽

Total Suspended Matter ◽

Western Coast ◽

Colored Dissolved Organic Matter ◽

Marine Hydrophysical Institute ◽

The North ◽

Azov Sea

Purpose. The study is aimed at revealing the structural regularities and variability of the fields of temperature, salinity, the colored dissolved organic matter and total suspended matter concentrations, and also the factors that form them in the Sivash Bay. Besides, the results obtained are to be compared with the already known features of the fields of the values under investigation which are typical of the Azov-Black Sea coastal zone; and the response in the considered fields to the North Crimean Canal damming is to be assessed. Methods and Results. Based on the data of 8 expeditions carried out by Marine Hydrophysical Institute in 2013–2016, the structural regularities and variability of the fields of temperature, salinity, the colored dissolved organic matter and total suspended matter concentrations, and the factors that form the fields of these values in the Sivash Bay were revealed. The quantitative indicators of changes in the fields of the considered values, which arose after the North Crimean Canal was dammed, are represented. Conclusions. In the region under study, a number of constantly acting factors that determine formation of special, not typical of the coastal area, features of the oceanological values fields are identified, namely: the influence of the Azov Sea and the North Crimean Canal waters, the rivers inflowing to the water area of the Sivash western coast, the isolated lakes, the swampy shallow bays and the isolated, relatively deep, parts of the coastline. Three years after the North Crimean Canal was dammed, in the northwestern Sivash salinity increased by 20 PSU. The opinion that Sivash is not a typical sea bay, but a connected with the Azov Sea reservoir with the signs of a salt swamp is confirmed

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Light attenuation in the north sea and the Dutch Wadden sea in relation to secchi disc visibility and suspended matter

Netherlands Journal of Sea Research ◽

10.1016/0077-7579(66)90005-6 ◽

1966 ◽

Vol 3 (1) ◽

pp. 28-51 ◽

Cited By ~ 15

Author(s):

L. Otto

Keyword(s):

North Sea ◽

Suspended Matter ◽

Wadden Sea ◽

Light Attenuation ◽

Secchi Disc ◽

The North ◽

The North Sea

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The Rotterdam Initiative in Reducing Waste Discharges at Source

Water Science & Technology ◽

10.2166/wst.1991.0289 ◽

1991 ◽

Vol 24 (10) ◽

pp. 171-177

Author(s):

T. Vellinga ◽

J. P. J. Nijssen

Keyword(s):

Public Relations ◽

Action Plan ◽

Detailed Balance ◽

River Rhine ◽

The North ◽

Complementary Role ◽

Action Programme ◽

The North Sea ◽

Set Up

Much of the material dredged from the port of Rotterdam is contaminated to such a degree that it must be placed in specially constructed sites. The aim of Rotterdam is to ensure that the dredged material will once again be clean. This will entail the thorough cleansing of the sources of the contamination of the sediment in the harbours and in the River Rhine. The Rotterdam Rhine Research Project (RRP) is one of the means to achieve this based on: technical research, legal research, public relations and dialogues with dischargers. The programme for five selected heavy metals is almost complete. For many heavy metal discharge points between Rotterdam and Rheinfelden, a specially devised independent load assessment has been carried out four times. Balance studies were used to determine the relative contributions of the point discharges to the total. Currently the results are being used in an attempt to negotiate agreements with a selected number of the major dischargers. At present, more detailed balance studies are being set up and exploratory measurements carried out for organic micropollutants. It may be concluded that the research is progressing successfully and methods and techniques developed seem satisfactory and broadly applicable. The Rhine Action Programme encompasses an international effort to improve the quality of the Rhine water. Although the RRP plays a modest complementary role to the Rhine Action Plan, there is no doubt of the value of this Rotterdam initiative. The mode of work followed in the RRP contains elements that can be of use in combatting the contamination of the North Sea by rivers other than the Rhine.

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Experimental procedures characterizing transformations of wastewater organic matter in the Emscher river, Germany

Water Science & Technology ◽

10.2166/wst.1995.0233 ◽

1995 ◽

Vol 31 (7) ◽

pp. 201-212 ◽

Cited By ~ 7

Author(s):

H. Løkkegaard Bjerre ◽

T. Hvitved-Jacobsen ◽

B. Teichgräber ◽

D. te Heesen

Keyword(s):

Organic Matter ◽

Wastewater Treatment ◽

Treatment Plant ◽

Subsequent Treatment ◽

Treated Wastewater ◽

Batch Reactors ◽

River Rhine ◽

Quality Changes ◽

Ruhr District ◽

Wastewater Quality

The Emscher river in the Ruhr district, Germany, is at present acting as a large wastewater collector receiving untreated and mechanically treated wastewater. Before the Emscher flows into the river Rhine, treatment takes place in a biological wastewater treatment plant. The transformations of the organic matter in the Emscher affect the river catchment, the subsequent treatment and the river quality. This paper focuses on evaluation of methods for quantification of the microbial transformations of wastewater in the Emscher with emphasis on characterization of wastewater quality changes in terms of biodegradability of organic matter and viable biomass. The characterization is based on methods taken from the activated sludge process in wastewater treatment. Methods were evaluated on the basis of laboratory investigations of water samples from the Emscher. Incubation in batch reactors under aerobic, anoxic and anaerobic conditions were made and a case study was performed. The methods described will be used in an intensive study of wastewater transformations in the Emscher river. This study will be a basis for future investigations of wastewater quality changes in the Emscher.

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Present Status of the Salmonids Atlantic Salmon and Sea-Trout in the Dutch Part of the River Rhine

Water Science & Technology ◽

10.2166/wst.1994.0057 ◽

1994 ◽

Vol 29 (3) ◽

pp. 37-41 ◽

Cited By ~ 7

Author(s):

W. G. Cazemier

Keyword(s):

Atlantic Salmon ◽

Salmo Trutta ◽

Natural Populations ◽

River Rhine ◽

Sea Trout ◽

The Past ◽

The North ◽

Trout Population ◽

The North Sea ◽

Heavy Pollution

In the past, the anadromous salmonids, Atlantic salmon (Salmo salar) and sea-trout (Salmo trutta), have formed natural populations in the river Rhine. From the beginning of the nineteenth century onwards, the greater part of the drainage area of the river has been gradually altered from a more or less rural and agricultural area, into a highly industrialised one with subsequent industrialisation, river-engineering and heavy pollution. These developments are considered to be the major cause for the disappearance of the populations of anadromous salmonid fish in the 1950s. The water quality has recovered significantly during the past 25 years. From about 1975 onwards, this process gave rise to a recovery of the anadromous trout population. Results of recent studies of the sea-trout migration pattern are presented. They reveal that nowadays these salmonids can complete their up- and downstream migrations from the North Sea to places, situated at hundreds of kilometres upward the river and vica versa. The numbers of recorded Atlantic salmon and catch locations in inland waters are presented. They show a significant increase since 1989. These phenomena can be understood as promising signs of the recovery of the Rhine aquatic ecosystem.

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