Water environment

About: Water environment is a research topic. Over the lifetime, 13384 publications have been published within this topic receiving 125138 citations.

Flow over gabion weirs.

Abstract: A conventional weir typically consists of an impermeable body constructed of concrete, since its primary functions are to heading up water and efficiently regulate flow. However, an impermeable body prevents the longitudinal movement of aquatic life and transportation of physical and chemical substances in water, eventually having a negative impact on the water environment. One of the advantages of gabions as a building material is that the motion of individual stones comprising the gabion is not of much concern. The wire mesh of the gabion basket serves to restrain any significant movement. Also, gabion weirs offer an alternative design that could be adopted for flash flood mitigation. In this study, a series of laboratory experiments was performed in order to investigate the flow over gabion weirs. For this purpose, two different gabion weir models were tested in two horizontal laboratory flumes of 10-m and 17-m length, 0.3-m width, and 0.3- and 0.5-m depth, respectively, for a wide range of discharge, upstream water depth, downstream water depth, weir height, weir length, and gabion filling gravel material size. The results of the gabion weir were compared with those of experiments carried out on solid weirs having the same dimension and it was found that there is a large deviation when the solid weirs equation is applied to gabion weirs (permeable weirs). So, using one of the existing solid weir flow formulas would lead to an erroneous calculated value. Multiple regression equations based on the dimensional analysis theory were developed for computing the discharge over gabion weirs for both free and submerged flow regimes. Also, equations were introduced for computing the discharge coefficient to be applied with the traditional solid weir equation.

Behavior and mechanism of Ni(II) uptake on MnO2 by a combination of macroscopic and EXAFS investigation

Abstract: The effects of pH, ionic strength, competing ions and initial metal concentrations on the uptake behavior and mechanism of radioactive Ni(II) onto MnO2 was investigated using a combination of classical macroscopic methods and the extended X-ray absorption fine structure (EXAFS) spectroscopy technique. The results indicated that the uptake of Ni(II) on MnO2 is obviously dependent on pH but independent of ionic strength, which suggested that the uptake of Ni(II) onto MnO2 is attributed to an inner-sphere surface complex rather than an outer-sphere surface complex. EXAFS analysis shows that the hydrated Ni(II) is adsorbed through six-fold coordination with an average Ni–O interatomic distance of 2.04 ± 0.01 A. It can be inferred from the EXAFS analysis that the inner-sphere surface complex of Ni(II) onto MnO2 is involved in both edge-sharing and corner-sharing linkages. Both the macroscopic uptake data and the molecular level evidence of Ni(II) surface speciation at the MnO2-water interfaces should be factored into better prediction of the bioavailability and mobility of Ni(II) in soil and water environment.

Benthic macroinvertebrates as indicators of environmental quality of an urban stream, Zaria, Northern Nigeria

Abstract: For a period of 2 years (from July, 1997 to June, 1999), 87 benthic macroinvertebrate taxa, composed of 12,078 individuals were collected from four stations of Bindare stream and one station on River Galma. Samples were collected monthly, using a Van Veen grap. Physicochemical variables were also determined using standard methods. The catchment areas of Bindare upstream (stations 1 and 2) are farmlands, with few isolated human settlements suggesting a less polluted water environment. The BOD which ranged between 1.88 ± 1.67 mg/l to 8.0 ± 4.76 mg/l increased downstream of the point of discharge. This allowed the survival of sensitive species such as Ephemeroptera, Hemiptera, Plecoptera, Odonata and Neuroptera at upstream. The great preponderance of the class Diptera and Oligochaeta at stations 3 and 4 are attributed to various domestic and agricultural effluents discharged into the stream at these points. The organic pollution of Bindare stream resulted in a decrease in benthic macroinvertebrate species richness and an increase in species density. Compared to background values, these changes in both species richness and density contributed to a reduction in the calculated Magarlef water quality index, hence a deteriorated water quality. Key words : stream, effluents, water quality, macro benthos, indicator species. Journal of Aquatic Sciences Vol.18(2) 2003: 85-92