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1

Mapping depths of groundwater level architecture: implications on modest groundwater level declines and failures of boreholes in sedimentary environs

George N. J., Ekanem A. M., Thomas J. E., Ekong S. A.

Acta Geophysica

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2021

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Vol. 69, no. 5

1919--1932

EN

Due to financial wherewithal, only shallow wells, which are extremely prone to seasonal groundwater decline, are constructed in the study area. Generally, new groundwater wells are designed to follow the criteria of the old wells, which may be vulnerable to substantial groundwater depletion through water-level decline. Going by this, newer groundwater wells constructed near older ones are 100% susceptible to the uninvestigated depletion associated with the older ones. The method used integrates vertical electrical sounding (VES) technique employing the Schlumberger electrode configuration, which measured the resistivity of geologic layers, depths and thickness with hydrogeological information, which constrained the VES interpretation. The aim was to check the spread of groundwater depth–water table ratios for the shallow aquifers. The 1-D resistivity analysis shows that the topsoil/motley topsoil has resistivity ranging from 71.8 to 1964.1 Ωm and mean 586.9 Ωm, while its depth ranges between 0.5 and 11.3 m with mean value of 2.8 m. In layer 2, while the resistivity spans between 71.3 and 1488.6 Ωm with mean value 444.6 Ωm, the depth and thickness, respectively, have a range and mean value of 2.0–170.4 m and 41.9 m and 3.4–112.2 m and 41.0 m. The third layer resistivity ranges from 7.5 to 2332.5 Ωm with mean value of 797.2 m. The depth of burial and the thickness of the third layer, respectively, have mean of 63.0 m and 74.6 m and range of 40.3–106.3 m and 50.1–115.6 m. The fourth layer penetrated by current at 150 m half of current electrode separation has undefined thickness and depth with respective resistivity range and mean of 25.3–2385.3 Ωm and 508.4 Ωm. Based on the resistivity results and nearby borehole data, sizeable numbers of borehole in the area have depths (between 40 and 80 m) that are remarkably greater than the water table depths (1.4–37.6 m). A few boreholes have depths that are sparingly greater than water levels and by the present climate change; they are not likely to be depleted by virtue of water-level declines as the well depth–water table depth ratios are still sustainable to ward of the depletion associated with water-level decline. The results indicate the spatial spread of shallow hydrogeological units as well as the water-level architecture, which is believed to provide useful information that will complement lithological logs while planning for newer groundwater well development in the area.

2

Microstructure evolution and mechanical properties of underwater dry welded metal of high strength steel Q690E under different water depths

Sun Kun, Huc Yu, Shi Yonghua, Liao Baoyi

Polish Maritime Research

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2020

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nr 4

112--119

EN

Q690E high strength low alloy (HSLA) steel has been intensively applied in maritime engineering. Also, the underwater dry welding (UDW) technique has been widely used to repair important offshore facilities. In this paper, joints of Q690E steel were fabricated through single-pass underwater dry welding at three pressures (0, 0.2, and 0.4 MPa). To study the effect of the pressure on the microstructure and mechanical properties of the UDW joint, an optical microscope (OM) and scanning electron microscope (SEM) were used to observe the microstructure and fracture morphology of the welded joints. The electron backscattered diffraction (EBSD) technique was used to analyse the crystallographic features and the crystallographic grain size of the ferrites. The proportion of acicular ferrite (AF) in the UDW joints and the density of low-angle boundaries increase dramatically with the increasing depth of water. The weld metal of UDW-40 shows higher strength because more fine ferrites and low-angle boundaries within UDW-40 impede the dislocation movement.

3

Influence of stick electrode coating’s moisture content on the diffusible hydrogen in underwater wet shielded metal arc welding

Klett J., Hassel T.

Advances in Materials Science

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2020

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Vol. 20, nr 4(66)

27--37

EN

In shielded metal arc welding, the major factors influencing hydrogen uptake into the weld metal are (i) the hydrogen content of the base metal, (ii) hydrogen input by the welding consumable, and (iii) the hydrogen introduced by the atmosphere surrounding the arc process. In this study, the relative contribution of these factors is investigated and compared to each other for the case of underwater wet shielded metal arc welding. To assess the influence of the stick electrode’s moisture (capillary introduced water during handling operations) on the diffusible hydrogen in wet welded samples, wet and dry electrodes were welded at four different water depths. The moisture was absorbed through the sharpened electrode tip only, to ensure close to service conditions. The results show that the moist stick electrode coatings lead to 22.6% higher average diffusible hydrogen content in the weld metal (0.5 m water depth an average). However, the effect disappears with increasing water depths (no difference in 60 m water depth).

4

Assessment of metallic contamination in sediment and mullet fish (Mugil cephalus Linnaeus, 1758) tissues from the East Algerian coast

Ouali N., Belabed B. E., Zeghdoudi F., Rachedi M.

Journal of Water and Land Development

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2018

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no. 38

115--126

EN

The present work was designed to assess the contamination level in the coastal of Annaba, following the spectrophotometric determination of the level of some metallic elements (Fe, Cu, Pb, Zn, Ni and Cd) in the sediments along an increasing bathymetric gradient (10 m and 20 m), as well as in the biological indicator grey mullet (Mugil cephalus) muscle. During the winter period (2014), 12 surface sediment samples, and a total of 24 fish were collected. Once the samples are dried, crushed and sieved, 0.5 g dry weight of each sample was added to concentrated acids. The results showed that the levels of some metals are superior to the recommended guideline values, and consequently the sediment of this bay is contaminated by iron, lead and copper. The contamination index (CI) showed a general tendency in the concentration of the studied metals as follows: Fe > Pb > Cu > Zn > Ni > Cd, since the most studied metals occurred at higher concentration in depth (20 m). However, the average concentrations of metals in fishes were found to be as the following order: Fe > Zn > Pb > Cu > Ni > Cd. The consumption of fish from some contaminated sites can be dangerous because concentrations of lead, cadmium and zinc exceed the international standards. Moreover, the strong positive correlation observed between the metallic elements of sediments and fishes confirm that these metals resulted from the similar sources of the anthropic activities, such as domestic, port, industrial and agricultural waste discharges. This is confirmed by the determined of pollution load index (PLI) parameter. Conclusively, a regular monitoring program of heavy metal is recommended for protecting these organisms, and to reduce the environmental risks.

PL

W pracy oceniono poziom zanieczyszczenia strefy przybrzeżnej w okolicach Annaby na podstawie spektrofotometrycznych analiz metali (Fe, Cu, Pb, Zn, Ni and Cd) w osadach na różnej głębokości (10 i 20 m) i w mięśniach cefala pospolitego (Mugil cephalus) jako organizmu wskaźnikowego. W okresie zimowym (2014 r.) zebrano 12 próbek osadów powierzchniowych i łącznie 24 ryby. Po wysuszeniu, pokruszeniu i przesianiu próbek do stężonych kwasów dodano 0,5 g suchej masy każdej próbki. Wyniki dowodzą, że stężenie niektórych metali przekracza dopuszczalne normy, a osady w zatoce są zanieczyszczone żelazem, ołowiem i miedzią. Wskaźnik zanieczyszczenia (CI) kształtował się następująco: Fe > Pb > Cu > Zn > Ni > Cd, przy czym większe stężenie większości metali notowano na głębokości 20 m. Średnie stężenie metali w mięśniach ryb układało się natomiast w porządku: Fe > Zn > Pb > Cu > Ni > Cd. Konsumpcja ryb z niektórych skażonych stanowisk może być niebezpieczna, ponieważ stężenie ołowiu, kadmu i cynku przekracza międzynarodowe standardy. Ponadto, silna dodatnia korelacja między stężeniem metali w osadach i w rybach dowodzi, że metale te pochodzą z tych samych antropogenicznych źródeł takich jak zrzuty ścieków bytowych, portowych, przemysłowych i rolniczych. Potwierdza to oznaczony wskaźnik ładunku zanieczyszczeń (PLI). W podsumowaniu zaleca się wdrożenie regularnego programu monitoringu w celu ochrony organizmów wodnych i ograniczenia ryzyka środowiskowego.

5

Potholes of Mountain River as Biodiversity Spots : Structure and Dynamics of the Benthic Invertebrate Community

Ren H., Yuan X., Yue J., Wang X., Liu H.

Polish Journal of Ecology

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2016

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Vol. 64, nr 1

70--83

EN

Temporary freshwater rock pools, as special, small-sized and isolated habitats, provide ideal systems for studying island biogeography and ecological theories and processes. In this study, a total of 70 potholes of mountain rivers were sampled during the four seasons from November 2013 to October 2014 to assess the structure of the benthic invertebrate community and to identify the relationships between habitat characteristics and the community composition. Pothole area ranged from approximately 0.01 to 0.39 m2, and pothole depth ranged from 0.03 to 0.74 m. Forty-three taxa belonging to 37 families and 16 orders were collected from the potholes. The highest numbers of benthic invertebrate taxa were observed in summer and the highest average number of taxa per pothole (8.5) was observed in autumn. The diversity was the highest in spring, and the average densities of benthic invertebrates were highest in autumn. Large potholes supported more taxa than small ones and significant relationships between richness and pothole area, richness and water volume were observed. The results of Redundancy Analysis show that the community composition of benthic invertebrates in the potholes was closely correlated with water temperature, pothole area and water depth. Our results indicate that benthic invertebrate communities in river potholes are mainly structured by water depth, pothole area and water volume. The seasonal changes are also an important factor determining the presence/absence of certain taxa.

6

Zmiany stężenia tlenu i temperatury w warunkach różnych głębokości wody w śródpolnym oczku wodnym

Wesołowski P., Brysiewicz A., Gałczyńska M.

Woda-Środowisko-Obszary Wiejskie

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2014

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T. 14, z. 4

135--144

PL

Badania przeprowadzono w latach 2010–2013 w śródpolnym oczku wodnym Stare Czarnowo, w województwie zachodniopomorskim. Celem podjętych badań było określenie stężenia tlenu rozpuszczonego w wodzie i jej temperatury w warunkach zróżnicowanej głębokości wody. Pomiary wykonywano w trzech pionach badawczych o zróżnicowanej głębokości wody. W okresie badań stwierdzono, że stężenie tlenu rozpuszczonego w wodzie oczka wodnego zależało od jej głębokości w badanych pionach pomiarowych. Największe średnie z lat 2010–2013 wartości tlenu rozpuszczonego w wodzie w okresach wegetacyjnych (IV–X) zanotowano w trzecim pionie pomiarowym (III) w warunkach największej głębokości wody (3,00 g O2•m-3). Mniejsze wartości średniego stężenia tlenu stwierdzono w warunkach mniejszych głębokości wody: w pierwszym pionie badawczym (I) – 1,96 g O2•m-3, a w drugim (II) – 2,22 g O2•m-3.

EN

Studies were carried out in the years 2010–2013 in a mid-field pond Stare Czarnowo in Zachodniopomorskie Province. The aim of the study was to determine dissolved oxygen concentration and temperature at different water depths. Measurements were performed in three water profiles of different depth. The concentration of dissolved oxygen in water was found to depend on water depth. The highest mean (April to October 2010–2013) concentration (3.00 g O2 m-3) was noted in the third, deepest water profile. Lower mean concentrations of oxygen were recorded in the first (1.96 g O2 m-3) and second (2.22 g O2 m-3) water profile.

7

Morphological variation of oospores in the population of Chara rudis A. Braun in a mesotrophic lake

Boszke P., Bociąg K.

Polish Journal of Ecology

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2008

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Vol. 56, nr 1

139-147

EN

The morphological variation of Chara rudis A. Braun oospores was examined in a local population in a deep (43 m), hardwater (34 mg Ca dm[^-3]) and mesotrophic (P[tot] 0.095 mg P dm[^-3], SD 8 m) lake (NW Poland). Two variants of population density and three variants of depth were taken into account. Oospores are 712.8 [plus or minus] 37.6 (600-817) [mi]m long and 452.6 [plus or minus] 34.2 (350-516) [mi]m wide. They have 8-13 ridges. The outer membrane is slightly granulated. The isopolarity index (length/width x 100) is 158.4 [plus or minus] 9.9 (140-190). The variation coefficient varies from 5% for oospore length to around 10% for fossa width. It was shown that the differences between oospores coming from individual depth and density variants are statistically significant. The biggest (733.21 [plus or minus] 33.3 [mi]m) oospores occurred on individuals growing at a depth of 3 m, while the smallest ones (673.3 [plus or minus] 43.4 [mi]m) at 5 m. The oospores from highly dense aggregations (> 50 individuals x 0.1 m[^-2]) were much longer and wider than oospores from scattered (<10 individuals x 0.1 m[^-2]) individuals. The observed intrapopulation variation of oospores can be regarded as a response to environmental changes along the depth gradient.