Evaluation of trace-metal enrichments from the 26 December 2004 tsunami sediments along the Southeast coast of India

The tsunami sediments deposited after the December 2004 tsunami were sampled immediately in the coastal environment of Tamil Nadu State on the southeast coast of India. Fifty-four sediment samples were collected and 14 representative samples were selected to identify the level of metal contamination in tsunami sediments. The results indicate that the sediments are mainly of fine to medium-grained sand and contain significantly high contents of dissolved salts in sediments (Na⁺, K⁺, Ca⁺², Mg⁺², Cl⁻) in water-soluble fraction due to seawater deposition and evaporation. Correlation of acid leachable trace metals (Cr, Cu, Ni, Co, Pb, Zn) indicate that Fe-Mn oxyhydroxides might play an important role in controlling their association between them. Enrichment of trace metals is observed in all the locations with reference to the background samples. High values of trace metals in the southern part of the study area are due to the large-scale industries along the coast, and they are probably anthropogenic in nature and of marine origin, which could cause serious environmental problems.     

Enrichment of trace metals in surface sediments from the northern part of Point Calimere, SE coast of India

This study deals with the geochemical nature of distribution, enrichment of total trace metals (Fe, Mn, Cr, Cu, Ni, Co, Pb, Zn, Cd) in bulk sediments and its association with sediment texture, carbonates and organic carbon. Sixty surface sediment samples were collected during two different seasons in 2002 and 2003 along the coastal regions in three transects from Nagapattinam town, north of Point Calimere in southeast coast of India. The sediments are mostly sandy silt and are dominated by the carbonate content. Organic carbon distribution indicates that they are brought in by the minor river input. Enrichment of trace metals is clearly identified by the domination of Pb, Zn, Cd with high values than the average crustal values and comparison of trace metals from other coastal regions in the southeast coast of India. Statistical analysis clearly indicates that Fe and Mn control the distribution of trace metals and are concentrated in the finer particles and organic carbon fraction. The increase in concentration signifies the need for regular monitoring of the offshore coastal region in southeast coast of India which was recently destroyed by the 2004 December tsunami event, and which is also located near the Sethu Samuthram Ship Canal Project.     

Geochemical variations of major and trace elements in recent sediments,off the Gulf of Mannar,the southeast coast of India

The Gulf of Mannar along the Tuticorin coast is a coral base of the southeast coast of India. To obtain a preliminary view of its environmental conditions, geochemical distribution of major elements (Si, Al, Fe, Ca, Mg, Na, K, P), trace elements (Mn, Cr, Cu, Ni, Co, Pb, Zn, Cd) and acid leachable elements (Fe, Mn, Cr, Cu, Ni, Co, Pb, Zn, Cd) were analyzed in surface sediment samples from two seasons. Geochemical fractionation confirmed the lithogenic origin of metals, which were mainly associated with the detrital phase. The sediments in the gulf are sandy with abundant calcareous debris, which controls the distribution of total and acid leachable elements. Enrichment factors relative to crust vary by a magnitude of two to three and the presence of trace metals indicates the input of Cr, Pb, Cd, Cu and Zn in both forms through industrial activities. Factor analysis supports the above observation with higher loadings on acid leachable elements and its association with CaCO₃. The increase in concentration of trace metals (Cr, Pb, Cd, Cu, Co, Ni, Zn) along the Gulf of Mannar indicates that the area has been contaminated by the input from riverine sources and the industries nearby. The present study indicates that other sources should be evaluated in the long-term monitoring program.     

Anthropogenic influences on toxic metals in water and sediment samples collected from industrially polluted Cuddalore coast,Southeast coast of India

The present study was carried out to investigate the impact of anthropogenic influences on Cuddalore coast, Southeast coast of India, with regard to physicochemical parameters and heavy metal concentration in the surface water and sediment samples of the study area. The samples were collected in different seasons of the year (January–December 2010) and analysed for physicochemical parameters (Temperature, pH, salinity, nitrate, nitrite, ammonia, phosphate and silicate) and heavy metals (Cd, Cu, Pb and Zn) using standard methods. Results showed that physicochemical characteristics and heavy metals concentration in the samples of the study area were varied seasonally and spatially. The concentrations of heavy metals in water and sediment samples of the study area were higher in the monsoon season compared with those of other seasons. The heavy metal concentration in collected samples was found to be above WHO standards. The order of heavy metals in water and sediment samples was Pb > Cu > Cd > Zn. The heavy metal data were analysed through widely using multivariate statistical methods including principle component analysis (PCA) and cluster analysis (CA). CA classified the sampling sites into three clusters based on contamination sources and season. The PCA revealed that the season has a huge impact on the levels, types and distribution of metals found in water and sediment samples. The study also shows the main basis of heavy metals pollution at Cuddalore coast is land based anthropogenic inputs as a result of discharging of waste from industries, municipal, agricultural activities and sewage into estuarine regions, which carries the wastes into coastal area during tidal action. Statistical analyses and experimental data revealed that the Cuddalore coast may cause health risk to the recreational users and fisher folk, ultimately warrants environmental quality management to control heavy metal contamination.     

Wind waves and sediment transport regime off the south-central Kerala coast,India

Wind waves in the innershelf of the south-central Kerala coast, south-west India were measured at four locations during different seasons. Simultaneously, numerical models were developed to simulate the wave and sediment transport regime of the innershelf. Strong monsoonal influence is seen in the wave characteristics with greater amplitudes, lower periods and switch-over from SW to SWW–W direction. The net annual longshore sediment transport is southerly in the innershelf and northerly in the surf zone. These counter-directional transports are linked by seasonally reversing the cross-shore transports. In the locations where the transports in the longshore and cross-shore directions are balanced, stable beaches prevail. Erosion/accretion tendency prevails in locations where these transports are not balanced. The southern and northern parts of the coast where onshore transports are predominant could be accreting zones. The erosion/accretion pattern deduced from the sediment transport model corresponds well with the long-term erosion/accretion trend for this coast.     

Seasonal and diurnal variability of thermal structure in the coastal waters off Visakhapatnam

Seasonal and diurnal variability of thermal structure in the coastal waters off Visakhapatnam has been examined in relation to the flow field and surface winds utilizing the hourly data of temperature and currents taken at a fixed location over a tidal cycle at monthly intervals. The coastal currents in the pre-monsoon period and strong near-surface winter cooling processes affect the thermal structure of the coastal sea. Upwelling which is predominant during March to May with an intermittent relaxing event helps in the development of a strong layered thermal structure while convective mixing due to winter inversions during November to February causes weak thermal gradients in the water column.     

Mesoscale modeling study of the oceanographic conditions off the southwest coast of India

A high resolution model, using the Miami Isopycnic Coordinate Ocean Model (MICOM), has been implemented for the first time to study the seasonal circulation and coastal upwelling off the southwest Indian coast during 1974. This model is part of a model and data assimilation system capable of describing the ocean circulation and variability in the Indian Ocean and its predictability in response to the monsoon system. Along the southwest coast of India the dominant coastal current is the reversing West Indian Coastal Current which is well simulated and described, in addition to the weaker undercurrent of the opposite direction. Upwelling of cold water, 4‡C lower than offshore temperatures appear in April. The upwelling intensifies with the southwest monsoon and is simulated in accordance within situ observations. Upwelling appears to be strongest off Cochin and Quilon, and the upwelling of cold water is seen together with a decrease in salinity in the model simulation.     

Metal pollution in coarse sediments of Tuticorin coast,Southeast coast of India

Indian coastal waters are subjected to considerable pressure from sewage and industrial wastes, which are responsible for the contamination of the coastal sediments with consequent loss in biosphere. The present investigation attempts to study the significance of coarse material (Sand fraction) in the distribution of metals in polluted marine sediments. The study revealed that coarse Sand component contains a relatively significant proportion of the anthropogenic metals (Cd, Cu, Pb and Zn) and therefore it cannot be neglected in metal pollution studies of coastal sediments. Further, the distribution of anthropogenic metals in both Silt + Clay and Sand fraction follow the same suit indicating similar pollution sources. From the total sediment type (Silt + Clay and Sand fraction) all anthropogenic metals had a noticeable amount (>50%) in the acid extractable (and potentially bio-available) fraction. This article stresses the importance of coarse fraction in metal pollution studies in Indian coastal system.     

Heavy metals distribution and fractionation in sediments of the Mahanadi River basin, India

Heavy metals distribution in core sediments, different size fractions of bed sediments (>212 urn, 90-212 jam, 63–90 urn, 53–63 urn, < 53 urn), and suspended sediments (>30 urn, 20–30 m, 10–20 urn, 2–10 urn, <2 m) have been discussed. Pb, Zn, and Cr have been accumulating in recent years in the sediments. Si, Al, Fe, Ca, and Mg dominate the bed and suspended sediment composition. Metals show increasing concentrations in finer sediments. Applying multivariate analysis to sediment composition, metals have been grouped into different factors depending upon their source of origin. Chemical fractionation studies on suspended and bed sediments show Fe, Zn, Cu, and Pb are associated with the residual fraction and Mn with the exchangeable fraction.     

Distribution and enrichment of trace metals in marine sediments of Bay of Bengal,off Ennore,south-east coast of India

In order to avoid the pollution of trace metals in marine environment, it is necessary to establish the data and understand the mechanisms influencing the distribution of trace metals in marine environment. The concentration of heavy metals (Fe, Mn, Cr, Cu, Ni, Pb, Zn, Co and Cd) were studied in sediments of Ennore shelf, to understand the metal contamination due to heavily industrialized area of Ennore, south-east coast of India. Concentration of metals shows significant variability and range from 1.7 to 3.7% for Fe, 284–460 μg g⁻¹ for Mn, 148.6–243.2 μg g⁻¹ for Cr, 385–657 μg g⁻¹ for Cu, 19.8–53.4 μg g⁻¹ for Ni, 5.8–11.8 μg g⁻¹ for Co, 24.9–40 μg g⁻¹ for Pb, 71.3–201 μg g⁻¹ for Zn and 4.6–7.5 μg g⁻¹ for Cd. For various metals the contamination factor (CF) and geoaccumulation index (I _geo) has been calculated to assess the degree of pollution in sediments. The geoaccumulation index shows that Cd, Cr and Cu moderately to extremely pollute the sediments. This study shows that the major sources of metal contamination in the Ennore shelf are land-based anthropogenic ones, such as discharge of industrial wastewater, municipal sewage and run-off through the Ennore estuary. The intermetallic relationship revealed the identical behavior of metals during its transport in the marine environment.     

Environmental geochemistry of Damodar River basin, east coast of India

 Water and bed sediment samples collected from the Damodar River and its tributaries were analysed to study elemental chemistry and suspended load characteristics of the river basin. Na and Ca are the dominant cations and HCO₃ is the dominant anion. The water chemistry of the Damodar River basin strongly reflects the dominance of continental weathering aided by atmospheric and anthropogenic activities in the catchment area. High concentrations of SO₄ and PO₄ at some sites indicate the mining and anthropogenic impact on water quality. The high concentration of dissolved silica, relatively high (Na+K)/TZ⁺ ratio (0.2–0.4) and low equivalent ratio of (Ca+Mg)/(Na+K) indicate that dissolved ions contribute significantly to the weathering of aluminosilicate minerals of crystalline rocks. The seasonal data show a minimum ionic concentration in the monsoon season, reflecting the influence of atmospheric precipitation on total dissolved solids contents. The suspended sediments show a positive correlation with discharge and both discharge and suspended load reach their maximum value during the monsoon season. Kaolinite is the mineral that is possibly in equilibrium with the water. This implies that the chemistry of the Damodar River water favours kaolinite formation. The concentration of heavy metals in the finer size fraction (<37 μ m) is significantly higher than the bulk composition. The geoaccumulation index values calculated for Fe, Mn, Zn, Ni and Cr are well below zero, suggesting that there is no pollution from these metals in Damodar River sediments. Received: 21 January 1998 · Accepted: 4 May 1998     

Impact of internal waves on the acoustic field at a coastal station off Paradeep,east coast of India

Internal Wave (IW) characteristics and the impact of IW on acoustic field have been studied utilizing the hourly time series of temperature and salinity data collected at a coastal site off Paradeep (north Bay of Bengal) during 24–25 October 2008. The IW characteristics, viz. period (t _per ), velocity (C _vel ), wavelength (L), and wave numbers (k), are found to be 2.133–34.72 h, 0.135 km h⁻¹, 0.37–6.2 km and 2.70–0.16 cycles km⁻¹, respectively. The semi-diurnal tidal forces are predominant than diurnal as well as at other frequencies and its contribution is about 64% towards the total potential energy (E ₀ = 3.34 J m⁻²). Sound velocity perturbations with space and time in the presence of IW field are examined from Garrettt-Munk (GM) model. Transmission loss anomaly for optimized source-receiver configuration at the depth of 53 m and range of 9 km has been computed from acoustic modelling. The loss in the acoustic transmission is found to be 38.4 dB in the presence of low-frequency IW field.     

Environmental effects of river sand mining: a case from the river catchments of Vembanad lake,Southwest coast of India

Rivers in the southwest coast of India are under immense pressure due to various kinds of human activities among which indiscriminate extraction of construction grade sand is the most disastrous one. The situation is rather alarming in the rivers draining the Vembanad lake catchments as the area hosts one of the fast developing urban-cum-industrial centre, the Kochi city, otherwise called the Queen of Arabian Sea. The Vembanad lake catchments are drained by seven rivers whose length varies between 78 and 244 km and catchment area between 847 and 5,398 km². On an average, 11.73 million ty⁻¹ of sand and gravel are being extracted from the active channels and 0.414 million ty⁻¹ of sand from the river floodplains. The quantity of instream mining is about 40 times the higher than the sand input estimated in the gauging stations. As a result of indiscriminate sand mining, the riverbed in the storage zone is getting lowered at a rate of 7–15 cm y⁻¹ over the past two decades. This, in turn, imposes severe damages to the physical and biological environments of these river systems. The present paper deals with the environmental effects of indiscriminate sand mining from the small catchment rivers in the southwest coast of India, taking the case of the rivers draining the Vembanad lake catchments as an example.     

Groundwater quality and its change over a decade: An analysis of a coastal urban environment from the west coast of India

Mangalore, one of the fastest growing cities along the west coast of India has witnessed a leap in industrialisation and urbanisation during the last decade. This study focuses on the quality of the groundwater of Mangalore city. The results are compared with an earlier study to record the change in water quality over a decade. HCO₃ and Na were found exceeding the highest desirable limit of the World Health Organisation (WHO) and Indian Standards Institute (ISI) standards for drinking water. The pH values at seven localities are not within the limits prescribed by WHO or ISI (highest desirable level or maximum permissible level). The present study shows that there has been an enrichment of chemical constituents during the last decade and that the Gurupur River, which flows parallel to the coast, plays an important role in impeding saltwater intrusion along the coast.     

Benthic foraminifera and geochemical studies with influence on pollution studies along the coast of Cuddalore,Tamil Nadu-ITS,India

Foraminifers, being sensitive to minute changes, either undergo morphological changes or even disappear from the area completely due to pollution or under unfavourable conditions. The characteristics of foraminifers to incorporate the signature of presence of pollutants are considered to be an effective tool for temporal pollution monitoring studies. Totally, 12 offshore samples (both sediment and water) were taken along a normal profile along the coast of Cuddalore for pollution studies. Apart from foraminiferal studies, geochemical studies of the sediments collected are also undertaken to correlate and substantiate the findings. The near-shore area has a higher concentration of trace elements. If these concentrations exceed or go below permissible limits, it is collateral for the marine community and for those who consume these marine resources. The concentration of trace elements like lead, zinc, manganese, copper, chromium and nickel was illustrated to give an idea of the trace element concentration of the study area. The sedimentological studies reveal the organic matter and calcium carbonate content of the samples, and the bottom water measurements reveal the temperature, salinity and dissolved oxygen of sample locations. These are used to determine whether the conditions prevailing could sustain life. The ratio of living to dead species is also determined and correlated with sedimentological and geochemical parameters. Pollution studies have given way to identify morphological abnormalities in the species mainly in Spiroloculina, Quinqueloculina, Elphidium, etc. but we could not find many effects among the faunal assemblages because of the nature of the sediments found in that area.     

Temporal and spatial variations in water flow and sediment load in Narmada River Basin, India: natural and man-made factors

The Narmada River flows through the Deccan volcanics and transports water and sediments to the adjacent Arabian Sea. In a first-ever attempt, spatial and temporal (annual, seasonal, monthly and daily) variations in water discharge and sediment loads of Narmada River and its tributaries and the probable causes for these variations are discussed. The study has been carried out with data from twenty-two years of daily water discharge at nineteen locations and sediment concentrations data at fourteen locations in the entire Narmada River Basin. Water flow in the river is a major factor influencing sediment loads in the river. The monsoon season, which accounts for 85 to 95% of total annual rainfall in the basin, is the main source of water flow in the river. Almost 85 to 98% of annual sediment loads in the river are transported during the monsoon season (June to November). The average annual sediment flux to the Arabian Sea at Garudeshwar (farthest downstream location) is 34.29×10⁶ t year⁻¹ with a water discharge of 23.57 km³ year⁻¹. These numbers are the latest and revised estimates for Narmada River. Water flow in the river is influenced by rainfall, catchment area and groundwater inputs, whereas rainfall intensity, geology/soil characteristics of the catchment area and presence of reservoirs/dams play a major role in sediment discharge. The largest dam in the basin, namely Sardar Sarovar Dam, traps almost 60–80% of sediments carried by the river before it reaches the Arabian Sea.     

Buried channels provide keys to infer Quaternary stratigraphic and paleo-environmental changes:A case study from the west coast of India

High resolution shallow seismic data was acquired from inner continental shelf of Goa,west coast of India to map underlying stratigraphic and buried geomorphic features of shelf strata.Seismic data revealed characteristic channel incisions beneath 4-15 m thick sediment layer and corresponds to multi cycle incisions.Stratigraphic analysis of these incision signatures reveals three prominent subaerial unconformities S6,S7 and S9.These unconformities were exposed during the last glacial,penultimate glacial(MIS-6)and prior to penultimate glacial(MIS-8)periods.On the basis of interpreted age of subaerial unconformities and differences in their morphological features,observed channel incisions have been divided grossly into three phases of incision.Phase-1 incisions are older than ～330 kyr BP,whereas,incisions of Phase-2 and Phase-3 correspond to ～320-125 kyr BP and ～115-10 kyr BP respectively.Plan form of these incisions varied from a straight channel type to ingrown meander and then to anastomosing channel types.These channels meet at the confluence of present-day Mandovi and Zuari rivers.The confluence point has varied in due course of time because of cyclic incision and burial with repeated sea level fluctuations.The preserved main channel width varies from ～100 m to 1000 m.and maximum channel depth reaches up to ～35 m.Comparison of quantitative and qualitative morphologic results of different phases of incisions suggest that Phase-2 channels had ～33% more mean bank full discharge than that of the Phase-3 channels.Phase-2 incisions had been carved in higher hydraulic energy condition as compared to Phase-3 incisions implying that the Indian summer monsoon was better during formative stages of Phase-2 incisions.     

Seasonal variation of the salinity in the Zuari estuary,Goa, India

The annual salt budget of the Zuari is examined. The characteristics of the estuary differ markedly from the low run off season during November–May to the heavy run off period of the southwest monsoon from June to October. During November–May the estuary is vertically mixed and the two processes controlling the transport of salt are run off induced advective transport out of the estuary, and tidally induced diffusive transport into the estuary. The magnitude of the latter is about 20% larger, leading to a salinity rise in the estuary. The diffusion coefficient has been estimated to be 233 ± 101 m²/sec. With the onset of the southwest monsoon, the run off increases dramatically, and the estuary loses about 75% of its salt during the first two months of the season. About 2/3 of this loss is recovered in the next two months when the run off decreases. Because the estuary is partially stratified during June–October, gravitational circulation is expected to play a role in addition to tidal diffusion and run off. The magnitude of its contribution has, however, not yet been determined.     

Hydrochemistry of reservoirs of Damodar River basin, India: weathering processes and water quality assessment

Water samples collected from the six reservoirs of Damodar River basin in pre- and post-monsoon, have been analysed, to study the major ion chemistry and the weathering and geochemical processes controlling the water composition. Ca, Na and HCO₃ dominate the chemical composition of the reservoir water. The seasonal data shows a minimum concentration of most of the ions in post-monsoon and a maximum concentration in pre-monsoon seasons, reflecting the concentrating effects due to elevated temperature and increased evaporation during the low water level period of the pre-monsoon season. Water chemistry of the reservoirs strongly reflects the dominance of continental weathering aided by atmospheric and anthropogenic activities in the catchment area. Higher concentration of SO₄ and TDS in Panchet, Durgapur and Tenughat reservoirs indicate mining and anthropogenic impact on water quality. The high contribution of (Ca+Mg) to the total cations, high concentration of dissolved silica, relatively high (Na+K)/TZ⁺ ratio (0.3) and low equivalent ratio of (Ca+Mg)/(Na+K) suggests combined influence of carbonate and silicate weathering. Kaolinite is the possible mineral that is in equilibrium with the water, implying that the chemistry of reservoir water favours kaolinite formation. The calculated values of SAR, RSC and sodium percentage indicate the ‘excellent to good quality’ of water for irrigation uses.