STUDIES ON HEAVY METALS IN WATER AND SEDIMENT OF HINDON RIVER

Abstract

Heavy Metal Pollution of aquatic systems is of major concern in today. Heavy metals gain accesss into natural water bodies such as rivers, lakes and oceans through avariety of nuiural and anthropogenic sources. The metals broadly partition into water and sediment as dissolved and particulate fractions. Each of these metal fractions further speciate into different forms. The speciation pattern however, depends on the nature of the metal and the physico-chemical characteristics ofwater and sediment. The metal toxicity, mobility bioavailability and depend more on speciation pattern than the metal concentration. Since the river bed sediments act as sink and source for such metalsand their species, the studieson the speciation of metal in water and sediment assumes importantance. The monitoring of Ganga and its tributaries was the prime objective of the projects under Ganga Action Plan Phase-I Ganga Project Directorate, now named as National River Conservation Directorate, Min. of Env. and Forests, Govt, of India. In Phase-ll, attention has been focussed on major tributaries of Ganga, viz. Yamuna, Gomti and Hindon. Hindon carrying pollution load from industrial towns and agricultural areas of Western Uttar Pradesh is one of the major tributaries of Yamuna river. Hindon originates from Upper Shivaliks (Lower Himalayas) and flows through four major districts of Western Uttar Pradesh and joins Yamuna downstream of Delhi. Joshi (1987) conducted some studies on hydrochemical aspects of river Hindon while Singhal eta/, (1987) conducted studies on the influence of industrial discharges on water quality of river Hindon. Seth (1991) carried out research on hydrological aspects of river Hindon basin and Kumar (1993) worked on the bioaccumulation of selected heavy metals in Hindon and Kalinadi. The assessment of metal load, metal distribution and metal speciation in water-sediment matrix of river Hindon has not been dealt at length. Keeping in view the importance of metal speciation studies, a study on the fate of a few heavy metals - Fe, Mn, As, Cu, Cr, Ni and Zn in Hindon river system was undertaken. The (ii) relevant data was collected through monitoring for two years at five different locations. For explicit detailing and clarity of presentation, the research work has been presented in the thesis under 8 different Chapters. CHAPTER 1deals in general, the background of environmental pollution with specific reference to heavy metal pollution and speciation in aquatic ecosystem. It describes briefly, the nature of metals and various processes influencing the metal distribution and transport in the aquatic environment. This chapter also defines the present research problem and emphasises on the major and specific research objectives. Acomprehensive scenario of the studies carried out on various riverine systems of the globe in general, and India, in particular is outlined in CHAPTER 2. The spatio-temporal variations of metals and their speciation pattern in the aquatic environment are presented. The physico-chemical characterization studies of various rivers and lakes are also discussed. Pertinent literature on speciation schemes and studies in water and sediment is collated and presented. The complete information including river basin soil type, climatic features, topography and sources of pollution of the riverine system under investigation has been presented in CHAPTER 3. Details of 5 monitoring locations - Maheshpur (MH), Barnawa (BA), Daruheda (DH), Mohan Nagar (MN) and Noida (NO) are also presented. CHAPTER 4 deals with sampling methodology, sampling frequency and the chemicals and equipment used in the present study. The various methods of analyses adopted for the analysis ofwater, sediment and background soil samples have also been discussed. Met als in water and sediment were analysed by Inductively Coupled Plasma Atomic Emission (iii) Spectrometer (ICPAES, model Plasma Lab 8440 with Labtam Computer, Australia). XRD Spectrograph (model PW 1140/90, Philips of Holland) was employed for the analysis and identification of various types of minerals in the bed sediment samples. Electron Probe Mi cro Analyser (EPMA, model JXA 8600 Super Probe, Joel of Japan) was used for both quali tative and quantitative analyses of bed sediment samples for confirmation of metals and metal oxides present in the mineral grains. The spatio-temporal variations recorded for water quality parameters, bed sediments and background soil characteristics have been presented in CHAPTER 5. The ionic balance check showed correspondence with 90% of the data. The chemical composition of river water is dominated by alkaline earths and weak acids. The pH, alkalinity and suspended solids were found to be higher in postmonsoon season reflecting the addition of alkaline washouts during monsoon. No significant annual variations in the parameters monitored were observed except for few parameters which showed a broader distribution within 95% confidence limits. AtMH and BA, COD and BOD were higher indicating the addition of do mestic and industrial wastes. Slight spatial variation has been noticed for these two param eters. Emperical relationships have been developed to show the decreasing trend in BOD in the river. DO was found to vary from zero mg/l at MH to as high as 7.8 mg/l at NO. Loca tions MH and BA fall in the critical zone of DO and .a sharp rising trend in DO has been observed from DH onwards. MH and NO recorded higher values of chlorides while at other locations, the values were very low indicating the prominence of site specific activities. TKN, Sulphates and Phosphates have not shown any significant temporal and spatial variations. The bed sediments and background soils have been analysed for particle size, pH, carbonate content, volatile solids and organic matter. In river bed sediments, higher values of carbonate content and organic matter were recorded during winter and postmonsoon than in summer. No significant spatial variation in carbonate content and organic matter (iv) was noticed. The XRD spectra of bed sediments revealed the dominance of minerals like quartz, biotite, siderite and albite while EPMA analyses have showed the presence of heavy metals in mineral grains of muscovite, biotite and albite (feldspar). The results of metals (Fe, Mn, As, Cu, Cr, Ni and Zn) and metal speciation ofwater, bed sediments and background soil samples have been presented in CHAPTER 6. Higher metal concentrations were found at all locations during summer and postmonsoon seasons, in summers due to concentration and postmonsoon due to washouts. No significant spatial variation was observed except forAs, Cuand Ni. The total metal in river water was speciated into dissolved and particulate bound fractions to determine partition coefficients (Pc). Postmonsoon season showed higher partition coefficient compared to winter and summer. Almost all metals were bound to particualte matter. Metals in background soil and bed sediments were analysed and higher concentra tion of As was found in the background soil than in river bed sediments. Fe, Mn, Cu, Cr and Ni were present in lower concentrations in background soil compared to that of bed sedi ment metal load. However, Zn has not shown any significant deviation. Metal pair ratio (metal/Fe) or high in bed sediments. Arsenic shown high metal pair ratio at all locations. Cu at MH and Cr at MH, BA and NO recorded high ratios. Zn exhibited high metal pair ratio at BA. The metal enrichment factor (ERF) indicated the enrichment of almost all metals at all locations except of As. However, Zn has shown marginal enrichment at some locations. (v) EP Tox test results established that there is no significant leaching of the metals from background and bed sediment samples. This indicates that there is no risk involved with respect to groundwater contamination by these metals. A comparison of Hindon river bed sediment metal load with those of Yamuna and Ganga, showed higher concentrations of almost all metals, except for Cu, which is 2 to 3 times higher in Yamuna river bed sediment. Coefficients of good correlation were observed between Fe-Mn, Cu-Mn, Cr-Mn, Cr-Cu, Zn-Fe, Zn-Mn and Zn-As while moderate correlation exists between Cu-Fe, Cr-Fe, Ni-Mn and Ni-Cr. Five different metal species - exchangeable, bound to carbonate, Fe/Mn oxides, or ganic matter and residual fractions were quantified in the bed sediment samples season ally using the Sequential Extraction Scheme suggested byTessier eta/, (1979). The speciation pattern is metal specific. However, seasonal variation in speciation was observed. Fe, Mn, Cu, Cr and Zn were prominently present as residual fractions. Carbonate fraction contrib uted moderately towards metal binding. Themajor fraction ofAsinsummer and postmonsoon was identified as bound to Fe/Mn oxides. In winter, arsenic speciated into organically bound and bound to Fe/Mn oxides. In addition to fraction bound to Fe/Mn oxides, two more frac tions viz. organically bound and residual fractions were also observed. However, postmonsoon season showed a clear distribution of metals into different species. This might be due to higher metal load during postmonsoon season. The sorption and leaching characteristics of the bed sediments have been evaluted under controlled conditions. The results are presented in CHAPTER 7. The batch sorption for Cu obeyed Langmuir isotherm. Continuous sorption tests in a plexiglass tray set up showed (vi) complete retention of Cu within 6to 8 hours. No significant influence of pH on copper ad sorption was observed. However, initial copper concentration affects the equilibrium of copper concentration in solution. The experimental results of simulated wastewater indicated that the organics (measured as BOD and COD) do alter the metal sorption and desorption equi librium. The metal desorption In the presence of organics is significant (48% desorption of copper in simulated wastewater as against 5% for tap water). The total metal and metal speciation pattern is an integral part of water quality and sediment characteristics. Therefore, CHAPTER 8 on epilogue includes (i) trend in water qual ity and bed sediment charactersitics and its impact on metal speciation pattern and metal sorption/leaching and (ii) correlation of field data and laboratory experiments. Higher metal load was observed in water and river bed sediments compared to other rivers like Ganga and Yamuna. The increased suspended load in water during postmonsoon increases the partition coefficient (in the range of 0.11 x 10s to 0.39 xlO5). Relatively high metal content of water and sediment seems to affect the metal speciation pattern. The organically bound and residual fraction of metal in the sediment were found to increase. Metal pair ratio and enrichment factor indicated enrichments in bed sediments at various locations. Good to moderate correlation existed between various metals. The metal adsorption and desorption are affected by the presence of organics in the river water. The solution for the proposed mathematical equations would help achieve the quantification of metal pollution load in any riverine system. (