TURBIDITY SUSPENI)ED SEDIMENT, AND WATER CLARITY: A REVIEW
Suspended sediment causes a range of environmental damage, including benthic smothering, irritation of fish gills, and transport of sorbed contaminants. Much of the impact, while sediment remains suspended, is related to its light attenuation, which reduces visual range in water and light availability for photosynthesis. Thus measurement of the optical attributes of suspended matter in many instances is more relevant than measurement of its mass concentration. Nephelometric turbidity, an index of light scattering by suspended particles, has been widely used as a simple, cheap, instrumental surrogate for suspended sediment, that also relates more directly than mass concentration to optical effects of suspended matter. However, turbidity is only a relative measure of scattering (versus arbitrary standards) that has no intrinsic environmental relevance until calibrated to a ‘proper’ scientific quantity. Visual clarity (measured as Secchi or black disc visibility) is a preferred optical quantity with immediate environmental relevance to aesthetics, contact recreation, and fish habitat. Contrary to common perception, visual clarity measurement is not particularly subjective and is more precise than turbidity measurement. Black disc visibility is inter‐convertible with beam attenuation, a fundamental optical quantity that can be monitored continuously by beam transmissometry. Visual clarity or beam attenuation should supplant nephelometric turbidity in many water quality applications, including environmental standards. 
Metal pollution assessment of sediment and water in the Shur River
Intensified industrialization and human activities have resulted in the release of various contaminants into the environment. Among them, heavy metals are often present as a result of mining, milling and industrial manufacturing. In the present investigation, bulk concentrations Pb, Cd, Zn, Cu, Fe, Ca and Al in Shur River (Iran) bed sediments and water around the Sarcheshmeh copper mine were measured from several sample locations. In addition, partitioning was assessed to determine the proportions of metals in different forms. The degree of sediment contamination was evaluated using an Enrichment Factor (EF) and geo-accumulation index (I geo) and a newly developed pollution index (I POLL). Elevated metals in sediment and water were found to be correlated with areas of the river that were proximal to direct and indirect mining activities. Cadmium and Zn showed the highest pollution index. Cluster analysis was performed in order to assess heavy metal interactions between water and sediment. Chemical partitioning studies revealed that organic metallic bonds were not significantly present in the sediment of the Shur River. 
Methane oxidation in sediment and water column environments—Isotope evidence
Microbial anaerobic oxidation of methane in sediments is a kinetic process associated with a carbon isotope effect which enriches the remaining methane in 13C. Three, models: % residual methane, higher hydrocarbon enrichment, and CO2-CH4 coexisting pairs are used to independently calculate fractionation factors (αc) in the range of 1.002–1.014, which overlap the range determined by culture studies, αc is smaller than that associated with methanogenesis by CO2 reduction or by acetate-type fermentation, and comparison of the coexisting CO2-CH4 pairs can distinguish between the formation and consumption processes. Methane oxidation in sediments continues to a threshold concentration of ca. 0.2 mM; the residual methane is either unavailable or unattractive to consumption. Minor amounts of methane may also be produced simultaneously in the methane consumption zone, influencing the apparent fractionation factor in this zone. 
Trace Metal Distribution in Fish, Sediment and Water Samples from Nkisa River, Nigeria
Aims: Contamination of surface water, sediment and fish samples by heavy metals have been a problem of developing countries as a result of growing rate of industrialization. This study was aimed at determining the level of heavy metal toxicants in water, sediment and fish samples from Nkisa River. The effect of these elemental contaminants and the associated health hazards were examined.
Study Design: Unicam 919 Atomic Absorption Spectrophotometer (AAS) was used for the determination of heavy metals in water, sediment and fish samples.
Place and Duration of Study: Department of Chemistry, Federal University of Technology, Owerri, Nigeria, between October and December, 2012.
Methodology: Water samples were pre-treated by repeated evaporation with analar grade nitric acid (HNO3) and heavy metal contaminant in the water samples were determined using Unicam 919 AAS. The wet sediment samples were ashed at 555ºC. 5 g of dried sediment was weighed into a Teflon crucible and 1 cm3 of (HNO3/HCl 1:3 v/v) and 6 cm3 hydrofluoric acid were added into the crucible. The resulting solution after digestion was collected in volumetric flask containing 2.7 g of boric acid. The digested sample was analyzed using Unicam 919 AAS. The whole fish were dried in an electric oven at 70-80ºC. A homogenized 2 g of the ground fish samples were put in flasks and 10 ml each of concentrated HNO3 and HCl were added. After digestion the samples were analyzed using Unicam 919 AAS.
Results: The result of this study revealed that water, sediment and fish samples were contaminated with heavy metals such as Cr, Pb, Cd, Fe, Mn. The study indicates that heavy metal contaminant were observed more in the sediment of the river. The associated health hazards of the metals were examined.
Conclusion: This study revealed that Nkisa River is contaminated with heavy metals from crude oil pipeline leakages and vandalization. This study gives an idea to the mechanisms of depletion and possible extinction of fish species in Nkisa River. 
Bioaccumulation of Heavy Metals in Water, Sediments and Tissues of Some Selected Fishes from the Red Volta, Nangodi in the Upper East Region of Ghana
Aims: To investigate the concentrations of Manganese (Mn), Cadmium (Cd) and Mercury (Hg) in water, sediment and organs of Sarotherodon galilaeus, Labeo senegalensis and Brycinus nurse.
Study Design: One-way ANOVA (no Blocking)
Place and Duration of Study: Nangodi, in the Upper East Region of Ghana, West Africa. Between November, 2012 and March, 2013
Methodology: 3 samples of water, sediment and 36 fish samples were collected from the Red Volta River in Ghana. All samples collected were labelled and placed in clean polyethylene bags with ice to maintain the freshness and immediately taken to laboratory where samples were deep frozen at -20°C until prepared for analysis.
Results: There was significant difference between heavy metals found in the river water, however there was no significant difference between heavy metals found in sediment (P= .05). Mn content was the highest and that of Cd was the lowest in water whiles in sediment Mn content was the highest and that of Hg was the lowest.
Also concentration of heavy metals found in the gills and muscles of Sarotherodon galilaeus, Labeo senegalensis and Brycinus nurse were statistically significant(P= .05).
The gills of Sarotherodon galilaeus accumulated the highest concentration of Mn whiles that of Brycinus nurse accumulated the lowest concentration, also the gills of Brycinus nurse accumulated the highest concentration of Cd whiles that of Sarotherodon galilaeusaccumulated the lowest concentration and Labeo senegalensis accumulated the highest concentration of Hg whiles that of Sarotherodon galilaeus accumulated the lowest concentration.
In muscles of the fish species studied, Sarotherodon galilaeus accumulated the highest concentration of Mn and Hg whiles Brycinus nurse accumulated the lowest concentration in the gills, Brycinus nurseaccumulated the highest concentration of Cd whiles Labeo senegalensis accumulated the lowest concentration in the muscles.
Conclusion: The research revealed that the water and fishes from Red Volta is polluted with Mn, Cd and Hg. Consumption of fish from the river could lead to health hazards induced by heavy metals. 
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 Whiticar, M.J. and Faber, E., 1986. Methane oxidation in sediment and water column environments—isotope evidence. Organic Geochemistry, 10(4-6), pp.759-768.
 Alinnor, I. J. and Alagoa, A. F. (2014) “Trace Metal Distribution in Fish, Sediment and Water Samples from Nkisa River, Nigeria”, Current Journal of Applied Science and Technology, 4(20), pp. 2901-2913. doi: 10.9734/BJAST/2014/8199.
 Asante, F., Agbeko, E., Addae, G. and Quainoo, A. (2013) “Bioaccumulation of Heavy Metals in Water, Sediments and Tissues of Some Selected Fishes from the Red Volta, Nangodi in the Upper East Region of Ghana”, Current Journal of Applied Science and Technology, 4(4), pp. 594-603. doi: 10.9734/BJAST/2014/5389.