Dissolved Oxygen

Agnébi is the most important river of littoral of Côte d'Ivoire. The first study of benthic macroinvertebrates of this river was studied in the middle stream (Pont Autoroute). This station was visited monthly during 10 months covering the 4 local rainy seasons. Ten (10) samples of the Ekman grab (an area of 0.225 m2) have been analyzed. Benthic macro fauna inventory showed for the whole river, 50 taxa distributed or divided: Oligochetes (2 taxa), Molluscs (14 taxa) and Insects (34 taxa). Five taxa are abundant (superior or equal of 5 % of total number) at Pont Autoroute: Potadoma liberiensis (37,3 %), Gabbiella africana (8,4 %), Cleopatra bulimoïdes (7,7 %), Mutela dubia (5,9 %) Chironomus spp (5,3 %). Specimen such as Ephemeroptera and Diptera Chironomidae are influenced by temperature and dissolved oxygen. High positive correlation has been established between snails and nitrate.

A pen culture system of the mud crab, Scylla serrata was introduced in Mtwapa mangrove creek with the aim of finding an alternative source of income and food for the local communities, who practice artisanal fishery in the creek. Other objectives were to motivate the interaction between scientists and the community through technology transfer, and to collect scientific data necessary for maintenance and management of the culture system. Pen construction took place from October 2000 - January 2001. The pen was located in the intertidal area and measured 800 m2. It was constructed and fenced using uzio (fish trap) material made of mangrove poles and wood. Stocking of the pen with seed crabs occurred from February- May 2001. Local sources was used to obtain a total of 1697 crab seeds which were measured (carapace length and width), weighed and sexed before stocking. The crabs were fed with trash fish obtained from a local fish processing plant. Feeding was conducted once daily, prefera...

The aim of this paper is to present an assessment of nitrates fluxes in the groundwater in Timis County using some direct measurements, as well as their spatial distribution. The presence of the high nitrogen concentrations in soils is a high potential risk for the groundwater and, implicitly, for human and animal health, the groundwater being the main source of the drinking water in many rural areas. One of the main risk factor for nitrates pollution is the agricultural activity, through the application of the mineral and organic fertilizers doses. As EU country, Romania has to report to international committees the state of nitrate pollution, in the respect of Nitrate Directive, in order to promote a sustainable agriculture based on suitable agricultural practices application for environmental protection. Several information systems, assessing and monitoring the potential vulnerable zones to nitrates, using pre-established indicators, have been developed. In order to assess the in...

In recent years, several ponds near Alviso, California, previously used in commercial salt production, were modified for wetland restoration and management as part of the South Bay Salt Pond Restoration Project. Algal growth and subsequent decay often leads to suboxic or anoxic water conditions in the ponds. Sampling trips were coordinated in the second half of 2008 to examine the interstitial water in the sediment and the overlying bottom waters of three shallow (average depth

While non-point nutrient loads are important determinants of biological productivity in Southeastern Piedmont impoundments, productivity can be attenuated by concomitant sediment loads that reduce the biological availability of these nutrients. A biogeochemical model is proposed ...

The aim of this work was to investigate the compatibility of fuel delivery materials with palm biodiesel fuel under novel immersion method which simulated diesel engine operation. For this, a two-stage investigation was conducted. In the first stage, the effects of biodiesel dissolved oxygen concentration and conductivity value on fuel delivery materials degradation under standard immersion were determined as a baseline study. In the second stage, modified immersion investigations which simulated the deterioration of biodiesel under common rail diesel engine operation (CRDE) were carried out to ascertain the compatibility present between fuel delivery materials and palm biodiesel. Palm biodiesel dissolved oxygen and conductivity were found to adversely affect both copper corrosion and nitrile rubber (NBR) degradation. The copper corrosion rate and NBR volume change increased by 9% and 13%, respectively due to 22.5% increase in the conductivity. In contrast, the copper corrosion rate and NBR volume swelling reduced by 91% and 27%, respectively due to 96% reduction in the dissolved oxygen concentration. Copper corrosion and NBR degradation were found to be lowered by up to 93% and 85%, respectively under modified immersion as compared to standard immersion. This study has inferred that good compatibility is present between fuel delivery materials and biodiesel under CRDE operation.

Photo-Fenton degradation of a reactive dyestuff, Reactive Black 5, was investigated in this study. The effects of UV light on Fenton Reagent process and the influence of reagents dosage, UV light intensity and initial dissolved oxygen concentration on photo-Fenton were explored. The experiments were conducted in a 3-L batch-mode reactor and were designed using Response Surface Method. The performance of

The purpoase of this research was to test the effects of three culture densities on the growth and survival of Octopus vulgaris. A total of 141 sub-adult octopuses (1,175.4 ± 194.9 g) were randomly distributed in nine tanks of 2,000 l each (3.6 m × 1.1 m, and 50 cm water depth). Three tanks were stocked with a low initial density of 4 kg/m3, while three other tanks were stocked with an initial density of 8 kg/m3, and the remaining three tanks were stocked at an initial density of 15 kg/m3. Octopuses were all fed frozen squid (Loligo gahi) at 5% body weight per day (%BW/day). The experiment lasted for 70 days. Water temperature varied between 20 ± 2°C, and salinity varied between 36 ± 1 ppt. During the entire experiment, dissolved oxygen was always >75%, and ammonia was always lower than 0.1 mg/l. No differences in growth or growth rates (between 0.9 and 1.1%BW/day for the three densities) were found. Nevertheless, mortality was significantly lower for the low density compared to the other two densities tested. Maximum densities in the culture tanks (>25 kg/m3) were attained in the higher culture densities after 56 days of the experiment.

The aim of this study was to investigate the seasonal and spatial variations in surface water quality at the mid-Black Sea coast of Turkey. The samples were collected from ten monitoring stations including rivers and sea water during the years from 2007 to 2008. The samples were analyzed for 25 parameters: total carbon, total inorganic carbon, total organic carbon, chromium, cadmium, copper, lead, iron, nickel, manganese, phenol, surfactants, ammonium, nitrite and nitrate-nitrogen, total phosphorus, adsorbable organic halogen, sulfate, hardness, dissolved oxygen, pH, temperature, total dissolved solids, electrical conductivity, and salinity. Multivariate statistical techniques, cluster analysis (CA) and factor analysis/principal component analysis (FA/PCA), were applied to analyze the similarities among the sampling sites to identify the source apportionment of pollution parameters in surface waters. The results indicate that seven factors for river water explained 82.24% of the variance. In seawater, seven factors account for 89.65% of the total variance. Varifactors obtained from factor analysis indicate that the parameters responsible for water quality variations are mainly related to organic pollution (municipal effluents), inorganic pollution (industrial effluents and waste disposal areas), nutrients (agricultural runoff), and dissolved salts (soil leaching and runoff process).

In view of the desire to improve the water quality of the heavily polluted branches of the Shatt al-Arab River at the City of Basrah, it was proposed to maintain effective flushing as well as contracting sewerage system. The present study was conducted in order to examine the water quality of these branches in an attempt to evaluate the effectiveness of the proposed flushing system. It has been found that their waters contained very low levels of dissolved oxygen and relatively high amounts of both COD and BOD5. The annual average water quality parameters for Basrah Branches were: dissolved oxygen 3.4 ppm; pH 7.67; hydrogen sulphide 1.4 ppm; ammonia 97 μg-at. N l−1; COD 15.9 mg l−1; BOD5 12.7 mg l−1; dissolved silicates 202 μg-at. Si l−1; dissolved reactive phosphate 13.4 μg-at. P-PO43− l−1; nitrate 10.4 μg-at. N-NO3− l−1; nitrite 2.1 μg-at. N-NO2− l−1 and chlorophyll-α 14.3 mg m−3. Based on our calculations, it has been concluded that the proposed system is effective, thus within a...

The microbial activity within activated sludge floc is a key factor in the performance of the activated sludge process. In this study, the microenvironment of activated sludge flocs from two wastewater treatment plants (Mill Creek Wastewater Treatment Plant and Muddy Creek Wastewater Treatment Plant, with aeration tank influent CODs of 60-120 and 15-35 mg/L, respectively) were studied by using microelectrodes. Due to microbial oxygen utilization, the aerobic region in the activated sludge floc was limited to the surface layer (0.1-0.2mm) of the sludge aggregate at the Mill Creek plant. The presence of an anoxic zone inside the sludge floc under aerobic conditions was confirmed in this study. When the dissolved oxygen (DO) in the bulk liquid was higher than 4.0mg/L, the anoxic zone inside the activated sludge floc disappeared, which is helpful for biodegradation. At the Muddy Creek plant, with its lower wastewater pollutant concentrations, the redox potential and DO inside the sludge...