Numerical studies on ecological effects of artificial mixing of surface and bottom waters in density stratification in semi-enclosed bay and open sea

Ecological engineering by artificial upwelling is considered a promising way to improve water quality. Artificial upwelling could lift nutrient-rich bottom water to the surface, enhance seaweed growth and consequently increase nutrient removal from seawater. However, one of the major obstacles of the engineering application is to determine the suitable position of ecological engineering, which is critical for artificial upwelling’s performance. In this paper, potential artificial upwelling positions in a semi-closed bay are simulated by using the unstructured-grid Finite-Volume Coastal Ocean Model (FVCOM). The results show that the upwelling position with relative small tidal current and close to corner will be helpful to increasing nutrient concentration of surface water, and be appropriate to build the ecological engineering. With proper design of the ecological engineering, it is possible to have a noticeable impact in semi-closed bay. Thus, artificial upwelling has the potential to succeed as a promising way to alleviate the eutrophication.

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Dissolved and Suspended Polycyclic Aromatic Hydrocarbons (PAH) in the North Aegean Sea

Mediterranean Marine Science ◽

10.12681/mms.261 ◽

2002 ◽

Vol 3 (1) ◽

pp. 89 ◽

Cited By ~ 8

Author(s):

I. HATZIANESTIS ◽

E. SKLIVAGOU

Keyword(s):

Polycyclic Aromatic Hydrocarbons ◽

Aromatic Hydrocarbons ◽

Aegean Sea ◽

Ship Traffic ◽

The North ◽

Open Sea ◽

Polycyclic Aromatic ◽

Bottom Waters ◽

North Aegean ◽

North Aegean Sea

The distribution and sources of polycyclic aromatic hydrocarbons (PAH) were investigated in the seawater of the North Aegean Sea. The measured PAH concentrations in SPM are generally considered as elevated for open sea waters and were evenly distributed in the area. Their levels in the dissolved phase (1.6-33.0 ng/l) were much higher than those encountered in the corresponding particulate phases (0.04-10.2 ng/l). The PAH patterns in both phases were dominated by the three ring aromatics and their alkylated derivatives, reflecting a predominant contribution of fossil hydrocarbons probably related to ship traffic, whereas no significant inputs from the rivers outfalling in the area were detected. In bottom waters PAH values were generally lower, whereas a higher depletion of the petroleum PAH in comparison with the pyrolytic ones according to depth was observed.

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Physical Oceanographic Studies for the Design of the Athens Sea Outfall (Saronikos Gulf, Greece)

Water Science & Technology ◽

10.2166/wst.1992.0203 ◽

1992 ◽

Vol 25 (9) ◽

pp. 31-40 ◽

Cited By ~ 1

Author(s):

A. J. Theodorou

Keyword(s):

Annual Variation ◽

Treatment Plant ◽

Density Stratification ◽

Current Field ◽

Virtual Absence ◽

Untreated Wastewater ◽

Open Sea ◽

Local Current ◽

New Treatment ◽

Under Construction

The discharge of about 600 000 m3/day of untreated wastewater into the northern part of Saronikos Gulf constitutes the major source of pollution for the latter. To take corrective measures, a new treatment plant and sea disposal by a deep outfall system is under construction. The basic design concept is to produce a submerged sewage field below the pycnocline, during the stratified period, at a location where the ambient current field is strong enough to advect it diluted to the open sea. Accordingly, the objectives aimed at obtaining accurate descriptions of the annual variation of the density stratification regime and the local current field. The results obtained showed that during summer the density stratification off Psyttalia Island is sufficiently strong to warrant the submergence of the sewage field; moreover, coupled with the virtual absence of upwelling and the presence of a well organized current field ensures the adequate offshore dispersal of the diluted effluent plume.

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The Role of Thermal Denudation in Erosion of Ice-Rich Permafrost Coasts in an Enclosed Bay (Gulf of Kruzenstern, Western Yamal, Russia)

Frontiers in Earth Science ◽

10.3389/feart.2020.566227 ◽

2021 ◽

Vol 8 ◽

Author(s):

Alisa Baranskaya ◽

Anna Novikova ◽

Natalya Shabanova ◽

Nataliya Belova ◽

Stepan Maznev ◽

...

Keyword(s):

Wave Energy ◽

Coastal Erosion ◽

The Arctic ◽

Shoreline Retreat ◽

Erosion Rates ◽

Open Sea ◽

Decadal Scale ◽

Enclosed Bay ◽

Thermal Denudation

Coastal erosion in the Arctic has numerous internal and external environmental drivers. Internal drivers include sediment composition, permafrost properties and exposure which contribute to its spatial variability, while changing hydrometeorological conditions act as external drivers and determine the temporal evolution of shoreline retreat. To reveal the relative role of these factors, we investigated patterns of coastal dynamics in an enclosed bay in the southwestern Kara Sea, Russia, namely the Gulf of Kruzenstern, which is protected from open-sea waves by the Sharapovy Koshki Islands. Using multitemporal satellite imagery, we calculated decadal-scale retreat rates for erosional segments of the coastal plain from 1964 to 2019. In the field, we studied and described Quaternary sediments and massive ground-ice beds outcropping in the coastal bluffs. Using data from regional hydrometeorological stations and climate reanalysis (ERA), we estimated changes in the air thawing index, sea ice-free period duration, wind-wave energy and total hydrometeorological stress for the Gulf of Kruzenstern, and compared it to Kharasavey and Marre-Sale open-sea segments north and south of the gulf to understand how the hydrometeorological forcing changes in an enclosed bay. The calculated average shoreline retreat rates along the Gulf in 1964–2010 were 0.5 ± 0.2 m yr−1; the highest erosion of up to 1.7 ± 0.2 m yr−1 was typical for segments containing outcrops of massive ground-ice beds and facing to the northwest. These retreat rates, driven by intensive thermal denudation, are comparable to long-term rates measured along open-sea sites known from literature. As a result of recent air temperature and sea ice-free period increases, average erosion rates rose to 0.9 ± 0.7 m yr−1 in 2010–2019, with extremes of up to 2.4 ± 0.7 m yr−1. The increased mean decadal-scale erosion rates were also associated with higher spatial variability in erosion patterns. Analysis of the air thawing index, wave energy potential and their total effect showed that inside the Gulf of Kruzenstern, 85% of coastal erosion is attributable to thermal denudation associated with the air thawing index, if we suppose that at open-sea locations, the input of wave energy and air thawing index is equal. Our findings highlight the importance of permafrost degradation and thermal denudation on increases in ice-rich permafrost bluff erosion in the Arctic.

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The influence of the Pb Content of Source Transport on its Distribution in the Bottom Layer

E3S Web of Conferences ◽

10.1051/e3sconf/202018502017 ◽

2020 ◽

Vol 185 ◽

pp. 02017

Author(s):

Dongfang Yang ◽

Dong Yang ◽

Weifeng Ling ◽

Dong Lin ◽

Haixia Li

Keyword(s):

Water Quality ◽

Surface Layer ◽

Water Body ◽

Jiaozhou Bay ◽

Bottom Layer ◽

Horizontal Distribution ◽

Ocean Current ◽

Open Sea ◽

Sea Current ◽

Bottom Waters

Based on the survey data of Jiaozhou Bay in 1992, the vertical distribution and seasonal variation of Pb in the surface and bottom waters from the bay center to the south of the bay mouth were studied, and the seasonal distribution, range and horizontal distribution trend of Pb content in the surface and bottom waters were determined. The results show that in May, August and October, Pb content in the waters from the south of the bay mouth to the center of the bay, and in the whole water body from the surface to the bottom, ranged from 4.20 to 24.39 μg/L, which met the national sea water quality standard of class II, class III and class IV. In other words, water quality was mildly, moderately and severely polluted by Pb. In the surface and bottom water, the Pb content was from low to high in May, October and August; In addition, the seasonal change of Pb content in the water body from low to high was as follows: spring, autumn and summer. In May, August and October, when the content of Pb in the surface layer was high, the corresponding bottom layer was high. And when the content of Pb in the surface layer was relatively high, and the corresponding bottom layer was relatively high. It shows that in May, August and October, the loss of Pb content from the surface layer to the bottom layer was relatively large. Further, in the waters from the southeast to the center, in May and August, the horizontal distribution trend of Pb in the surface layer was opposite to that in the bottom layer. But in October, the horizontal distribution trend of Pb in the surface layer was consistent with that in the bottom layer. What’s more, from May to October, the seasonal variation of Pb content in the bottom layer of the water body in the southeastern Jiaozhou Bay was mainly decided by that of Pb content transported by the open ocean current. In the water body in the center of Jiaozhou Bay, the seasonal change of Pb content in the bottom layer was different from that in the surface layer and from that in the ocean current. In terms of time scale, in the waters from the southern bay mouth to the center of the bay, in May, August and October, the Pb content in the surface and the bottom layer changed in the same range, maintaining the consistency. Furthermore, in terms of spatial scale, in May and August, according to the high content and increasing trend of Pb transported by the open sea current, the horizontal distribution trend of Pb in the surface layer was opposite to that in the bottom layer. Nonetheless, in October, the Pb content transported by the open sea current was relatively low and showed a trend of decrease. And the horizontal distribution of Pb in the surface layer was consistent with that in the bottom layer.

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