Sediment Analysis

This study deals with the pollution load of river Chambal in context with physico-chemical parameters of river’s sediment. The study was carried out for a span of one year from February 2017 to January 2018 at four sampling stations which is situated along with the drift area of river Chambal. Various physico-chemical parameters of river Chambal were observed viz., pH, soil texture, bulk density, water holding capacity (WHC), alkalinity, chloride, phosphate, sodium, potassium along with some trace metals like copper, iron, zinc, manganese, lead, cadmium, etc. The mean concentrations of trace metal elements were found in order of Fe>Mn>Pb>Cr>Cu>Zn>Cd respectively. High quantity of Fe and Mn were found at certain locations showing the interference of some local contaminants. The results give vital information regarding the pollution load of the river Chambal. There is an urgent need for more representative samples to be used to go beyond initial assessment as reported in the present study for making adequate recommendations.


Material and Methods:
The sediment samples were collected for the present investigation from four different experimental sites within a specific stretch of 70±10 kms. of river Chambal. The river bed samples from various depths were collected by dredge and scoop method (Robert and Christopher, 2001), quarterly from each sampling station and analyzed for a span of one year from February 2017 to January 2018. Samples were collected in fine quality polyethylene bags which were properly cleaned, labeled to indicate collection point, date and place, sealed and then taken to the laboratory for further analysis (USEPA, 1977). In laboratory, the collected samples were air dried and finely powdered by using mortar and then sieved. Before determination of metal elements the sediment samples were digested with HNO3 and HClO4 digestion method. The air dried samples were analyzed for metal elements with the help of an atomic absorption spectrophotometer. The protocol and analysis strategies were followed according to Method Manual for Soil Testing in India, 2011.

Result and Discussion:
The physico-chemical analysis provides a proper idea of any river's ecosystem. The results of determination of various physico-chemical parameters of river Chambal sediment at four locations; are summarized in Table-1 and station wise variations are shown in Fig.1 and Fig.2.
The color of sediment gives prefatory information of any soil or sediment that how much minerals included in it. All the four sampling stations sediment's color is found brown except station 'A'. Sediment or soil texture indicates about particle contents of different sizes which it includes. The Chambal river sediment is found almost sandy. The pH is simple but extremely important factor since most of the chemical reactions in aqueous environment are controlled by any change in pH value (Korfali S.I., 2003). Excessive acidic or alkaline environment of any habitat can kill marine life. Thus, pH value describes the quality of waste water effluent (Singare et al.;2011). In present investigation the maximum value of pH is observed 8.87 at SS-A and the minimum 7.78 at SS-C while the average pH is found 8.31(as shown in table-1). Higher value of bulk density is an indicator of low porosity and sediment compaction. Bulk density is used to express sediment's physical, chemical and biological measurement on volumetric basis for sediment quality assessment (Ramachandran et al., 2012). From station 'A' to 'D', the bulk density varies 1.34 g/cc to 1.88 g/cc and the mean value is observed 1.63 g/cc, whereas for sandy type of soil texture, below 1.60 g/cc is considered ideal bulk density for plant growth. Specific gravity is a specific ratio which gives information about sediment or soil containing organic matter and porous particles. Normally sediment or soil having heavy substances may have specific gravity around 3.0. In the analysis of specific gravity of river Chambal sediment, it is found in order to sample stations A>C>D>B; but during the whole study the average value 2.66 observed, which is almost close to 3.0. There is little critical difference between moisture content and water holding capacity (WHC) of soil. Moisture content of samples varies from 6.82% (SS-A) to 7.90% (SS-B) whereas the average moisture content of river sediment is found 7.29% (as shown in table-1). Water holding capacity is the maximum capacity of soil or sediment for holding water content itself. The maximum WHC is found 26.84% at SS-B while the minimum 18.93% is found at station-C. Overall the average WHC of river Chambal sediment is observed 21.75% of which variation is shown in Fig.1. Alkalinity provides a buffering capacity to aqueous system and support to resists pH changes. The alkalinity of river Chambal sediment is found maximum 0.023% at SS-C and minimum 0.005% at SS-A; whereas the mean of alkalinity of river sediment is 0.014% observed. Chloride is one of the major anion in stream water which acts as a disinfectant if present in a limited amount. In sediment it comes through atmosphere, earth crusts, igneous rocks, accumulation in sedimentary particles and by many anthropogenic activities. During this study the average value of chloride is seen 0.049% and the maximum is obtained 0.071% at SS-B (Table-1   The major sources of metals and nutrients are almost all type of detritus sedimentary rocks, industries effluents in which they used, anthropogenic activities, agricultural runoff nearby areas coming in to river drift area, finally settle down, stabilized and accumulated in sediment (Cheung et al., 2003). Surface water generally contains sodium and potassium as naturally abundant elements. As the sediments have low concentration of these nutrients, consequently the concentration of these ions is found in small quantities. In this sediment analysis, sodium varies from 0.074% to 0.095% and found maximum at SS-B, and minimum at SS-A. The average value of sodium 0.087% is observed; whereas potassium ranges from 0.38% at SS-B to 0.76% at SS-D during the study. An average value of potassium is obtained 0.52% at all locations of the river (Table-1). Although potassium is comparatively less hazardous in water, but spreads rapidly in water due to its relatively high mobility and transformation capability. In this analysis, the concentration of potassium is found little higher at all the stations in comparison to sodium (as shown in Fig.1).
Calcium and magnesium are also essential nutrients for all aquatic organisms and humans, occurs naturally in water bodies. Excess of cations such as Ca, Mg, Fe, Mn etc. influences the hardness and alkalinity of water (Shrivastava and Patil, 2002). Their presence in water is often closely correlated with the type of land use in the catchment area. Limestone is one of the naturally occurring sedimentary rock consisting of calcium and magnesium. Metal elements which bound to carbonates, oxides are released in water as a result of pH decrease (Zerbe et al., 1999). It is found during the study that the amount of calcium in sediment is relatively high compared to magnesium. The values of both Ca and Mg are observed maximum at SS-A, 16.71% and 1.68% respectively; and minimum value of calcium 12.68% at SS-D while the lowest value of magnesium is observed 0.87% at station-C (Table-1 & Fig-1). Similarly the mean concentration of Ca and Mg are found 14.23% and 1.1% respectively.
Phosphorus is one of the key elements necessary for the growth of planktons, plants and animals. The presence of phosphorus is often very rare in properly oxygenated freshwater system. The recycling of sediment bound phosphorus is particularly important because it may increase the rate of eutrophication and whenever eutrophication rises, it indicates phosphate augmentation in a water body resulting in depletion of dissolved oxygen (Chattopadhyay et al., 1995). Generally it is assumed that a major carrier for phosphate in sediments; is organic matter which acts as the source of nutrients to microbial communities (Ruttenberg et al., 2009). In this study period, the amount of phosphate in sediment is not observed so high. The average value of phosphate is recorded 0.05% in river sediment (Table-1) and doesn't show any wide fluctuation in its concentration.
The study of risk analysis of trace metals in any urban aquatic system is extremely important due to their persistence, bio-accumulation, toxicity and non bio-degradability (Helen D. et al., 2016). Large amount of metals are accumulated by all the creatures that are involved in aquatic food chain, in their bodies from water and sediment and finally reaching in a human body by this food cycle; can cause severe health and environmental problems to those, whose life depends on them (Adeyemo et al., 2008). Trace metals can be bound to or congested in amorphous materials, adsorbed on clay surfaces or iron/manganese oxyhydrides, complexes with organic matter, co-precipitated in secondary minerals such as carbonates, sulphates or oxides etc. (Lakshmanasenthil et al., 2013). There are many ways through which trace metals can be leaked into water viz. the erosion of geological matrixes, atmospheric depositions or anthropogenic sources such as sewage outfalls, industrial and agricultural runoff etc. (Edward et al., 2001;Kumar Rahul et al., 2014). In this study, total seven trace metals Cu, Cr, Pb, Fe, Zn, Mn and Cd have been investigated. Distribution and comparison of trace metals according to sampling sites are shown in Fig.2. The concentration of these metals significantly varies in the bed sediment samples collected from four locations of river Chambal. If the level of metals in sediment is below the threshold effect concentration (TEC), there is less possibility of harmful effects likely to be observed, but If the level is above the probable effect concentration (PEC), harmful effects can be seen broadly (Hoda et al., 2009).
Iron and zinc, are the two most essential trace elements for growth of plants and animals but in excess they may have adverse effects too. The main source of fluvial iron mainly includes agricultural runoff, erosion, natural decomposition of rocks and minerals, municipal wastes and untreated effluents of various industries etc. which keeps flowing in the stream and slowly depositing in river bottom sediment. During the study period, the level of iron has also been examined in the river sediment; which was found maximum among all the analyzed metals at all the sites and clearly crossing the limit of 30 ppm given by USEPA. The concentration of iron varies between 2.67% (26700 mg/Kg) at SS-A to 3.36% (33600 mg/Kg) at SS-C with an average value of 2.93% (29300 mg/Kg), station wise fluctuation are shown above (in Fig.1 and Table-1); However the mean concentration of Fe is found far above the TEC limit and less than the PEC limit but at station 'C' its value seems nearer to PEC limit (Table-2), which is the matter of serious concern. The concentration of Zn is recorded 1.54 mg/Kg maximum at SS-C and 1.12 mg/Kg minimum at SS-B with an average value of 1.36 mg/Kg for the river's sediment. The level of zinc is observed far below the limits given by USEPA and WHO sediment quality guidelines which are shown in Table-2 (Table-2). During this study, observed lead content in river sediment ranges between 65.38 mg/Kg (SS-B) to 82.01 mg/Kg (SS-C) with an average value of 74.16 mg/Kg (Table-1). The quantity of Pb in samples is also crossing the USEPA limit of 40 ppm. The exceeding value of Pb is very hazardous and noxious for riverine ecosystem (Singh et al., 2012). The results show the anthropogenic activities as well as nature's interference in the river.
The concentration of manganese has also been determined which is the second most observed metal in all the bed sediment samples. The dissolvability of Mn in water from sediment depends on pH level with many other factors (Ha N.T. et al., 2011). The maximum amount of Mn is found 673.92 mg/Kg at SS-A and the minimum 134.71 mg/Kg at SS-C, which seems much higher than the normal range. The average value of Mn in river sediment is recorded 300.72 mg/Kg; which is also exceeding the acceptable limit of 30 ppm given by USEPA for Mn (as shown in Table-2). Cadmium is another toxic metallic element which may be very dangerous for aquatic animals as well as ecological system of river; found below detection level at all the sampling stations. High concentrations of iron, manganese, copper, lead and chromium have been found in this river sediment; if they leached tardily in water from sediment in different weathering conditions and intaked regularly for a long period, then prove to be very fatal and carcinogenic.

Conclusion:
The sediment assessment gives significant information about relavantness of factors playing role in contamination of sediment and toxicity in bio-accumulative substances. The release of elements from sediments and their reaction with water are influenced by various environmental factors of an ecosystem. Many important physico-chemical parameters like bulk density, specific gravity, water holding capacity, sodium, potassium, calcium, magnesium etc. are determined which shows their extensive variations in all collected samples. High quantity of some metal elements confirms about anthropogenic activities as well as directly putting of sewage effluents by the municipalities and the industries of near by cities, agricultural runoffs, Nallah's falling, illegal sand mining, cremation of dead bodies near river banks and directly flown of these ashes into the river etc. According to the mean concentration of trace metals in river Chambal sediment; the sequence is as follows Fe>Mn>Pb>Cr>Cu>Zn>Cd. The concentration of almost all the trace metals in the collected samples is exceeding the guideline limits except Zn and Cd. But Fe and Mn contents are found superabundant in comparison to other metals; and on the basis of risk assessment code (RAC), environmental risk of Mn is found very high (Davutluoglu et al., 2011); that is indicating towards the contamination of sediment and continuously increasing pollution level of river Chambal. Through this study we have made an attempt to define the level of chemical exposure to biota. However, due to river fluxes, floods, tidal fluctuations and other weathering processes sediment contents changes accordingly, therefore more efforts needed to be made in this direction so that the river's fragile ecosystem can be retained.