Search

The spatio-temporal distribution of geochemical fractions of phosphorus and its bio-availability for Asia's largest brackish water lake has been carried out. One way ANOVA analysis revealed that both iron bound phosphorus (Fe-P) (p central sector (42.22%) > outer channel (36.63%) > southern sector (29.27%) of total phosphorus (TP). This is supported by the fact that bioavailable P is comparatively higher in the freshwater zone than in the brackish water zone. The principal component analysis (PCA) revealed a good relationship between dissolved phosphate concentrations of water column with benthic population density. It showed that TP availability in the sediment of the lake is mostly bounded with Al, Fe and organic matter (OM). Positive association of total carbon (TC), total nitrogen (TN) and OM with negatively loading of Eh indicates towards the fact that, deposition of TN and TC is largely governed by OM availability in sediment.

The current study focuses on the vertical profile of different geochemical fractions of phosphorus - loosely bound (Lo–P), aluminium bound (Al–P), iron bound (Fe–P), calcium bound (Ca–P), and organic bound phosphorus (O–P) along with ecological risk assessment of sediment cores from Chilika Lake, east-coast of India. The percentage contribution of the different fractions to the sedimentary phosphorus in the sediment column of the whole lake are on the order: O–P (33.2%) > Ca–P (20.3%) > Fe–P (18%) > Al–P (6.7%) > Lo–P (0.35%). The Phosphorus Pollution Index (PPI) revealed the contamination of lake sediment with phosphorus. The principal component and cluster analyses highlighted the anthropogenic contribution of phosphorus. The negative loading of Ca–P with Ca points towards its origin from marine shells. The discriminate analysis showed that the variables like Ca–P, bio-available phosphorus (BAP), and pH were able to effectively discriminate the sectors in a significant manner.

The study signifies the first work on natural radioactivity and to identify the associations as well as influence of geochemical properties on it. The determination of the natural radioactivity such as: 226Ra, 232Th, and 40K were carried out by gamma spectrometer and the median activities were found to be 26.27, 81.61, and 620.09 Bq kg−1, respectively. The geochemical parameters are pH, sand, silt, clay, organic carbon (OC), calcium carbonate (CaCO3), magnesium (Mg), potassium (K), calcium (Ca), sodium (Na), iron (Fe), phosphorus (P) and nitrogen (N) has been determined. The lagoon was mostly dominated by muddy-type sediment which is nearly 60% of the total sample and the high pH noticed in the NS (7.58) of Chilika, which is due to the presence of grass and weeds, by their photosynthesis process, which may cause the lake slighter alkaline. The high Fe concentration (2.53%) in the NS may be due to rapid relies of iron, whereas the enrichment of Ca in CS (1.02%) in the sediment may be from land runoff. The influence and relations between geochemical and natural radionuclides of the sediment were evaluated through geo-statistics, such as correlation matrices, factor analysis, and cluster analysis.

The study focuses on the spatial mapping of naturally occurring radionuclides along entire Tamil Nadu coast, which constitute nearly 30% of the east coast of India. In view of this, a total of 37 beach sediment samples are collected, and spectral measurement was carried out by High Purity Germanium detector. The average activity concentrations were found to be in the range of 34.33 ± 32.94 Bq kg−1 for 238U, 51.55 ± 40.39 Bq kg−1 for 238Th and 282.59 ± 84.45 Bq kg−1 for 40K. The contour maps showed the spatial distributions of each radionuclide and were drawn using the kriging method. Box-whisker plot shows the variation of activity concentrations of radionuclides, which follows the order 40K > 232Th > 238U in all the sediment samples. To understand the complex relationships among the radioactive variables and its environmental classifications, a multivariate statistical technique such as correlation matrices, and cluster analysis were applied to the radioactive data sets.

Socioeconomic developments and industrialization exert tremendous impact on beaches which is often neglected. Heavy metal (Cr, Mn, Co, Ni, Cu, Zn, Cd, and Pb) contents were estimated in the intertidal region from Kalpakkam to Mamallapuram (20 km), southeast coast of India covering seven locations. To evaluate the level of contamination of these metals; enrichment factor (EF), geoaccumulation index (I geo), contamination factor (CF), pollution load index (PLI) and modified degree of contamination (mCd) were applied. The results were also compared with the sediment quality guidelines (SQGs) to find out the eco-toxicity level. Metal contents in the beach sediment were observed in the order: Fe > Al > Mn > Cr > Cu > Ni > Zn > Pb > Co > Cd. Grain size distribution showed medium to coarse nature of the sediment. Significant positive correlation was found among the metals indicating their common source of input. Based on EF, minor enrichment of Mn and Zn and moderately severe to severe enrichment of Cr, Cu, Pb and Cd were observed which was further confirmed by I geo and CF values. Moreover, Mamallapuram showed a very high CF value for Cd (>6) indicating very high contamination accountable to anthropogenic sources. PLI and mCd in all the stations indicated unpolluted nature except M1 where the values pointed moderate degree of contamination. As per the SQGs, Ni and Cr values exceeded the probable effect limit value implying that these metals can have adverse impacts. None of the metals exceeded the effect range median indicating that the beach sediment is not very toxic.

This study focused on ecosystem responses to the environmental perturbations caused by the 2004 Indian Ocean Tsunami in a small lake that was a freshwater body in 1996, prior to the tsunami. The physicochemical and biological characteristics of Kokilamedu Lake (KKM) revealed drastic changes, compared with pretsunami conditions. Monthly average observations on water quality indicated the electrical conductivity of the water increased steeply to 17.41 mS cm−1 in 2009, from the lowest pretsunami value of 1.83 mS cm−1 (range of 1.83–5.25 mS cm−1). Simultaneously, the nitrate + nitrite (NO3 + NO2) values increased significantly from 0.49 μmol L−1 in 1996 to 74.47 μmol L−1 in 2006. Silicate (SiO4-Si) exhibited a dramatic increase in concentration, from an average of 64.87 μmol L−1 in the pretsunami period to 309.71 μmol L−1 the post-tsunami period (2009–2010). Inorganic phosphate had increased to a maximum of 9.59 μmol L−1 from a pretsunami maximum of 1.09 μmol L−1. The chlorophyll-α concentrations did not respond to the increased nutrient stoichiometry of the lake. There was a decreased chlorophyll-α concentration under post-tsunami conditions. The recent infilling of the lake with sediment during the tsunami, associated with wind-driven resuspension reduced the light penetration. There was a significant improvement in dissolved oxygen concentrations (2006–2010 average of 8.27 mg L−1) in the lake, however, compared with the pretsunami values (1994–1995 average of 5.94 mg L−1). The algal component is now dominated by blue-green algae, while green algae had dominated in the pretsunami period. Pre- and post-tsunami observations from a control site did not exhibit such dramatic shifts from the 1995 and 1996 conditions, whereas a shift was apparent in the case of KKM. Certain marine fishes have adapted to this altered ecosystem. These marine species encountered (Elops machnata, Cociella punctata, Sphyraena jello, Platycephalus indicus, Glossogobius giuris) might have been recruited during the intrusion of the tsunami waves.

Sequential chemical extractions were used to study the spatial and temporal distribution of different forms of phosphorus (P) in the surface sediments of Chilika, the largest brackish water lake in Indian subcontinent. Sediments were analyzed for different forms of phosphorus along with some sedimentary parameters such as sand, mud, and organic carbon. The lake sediments are found to be mostly sandy near outer channel, whereas other parts of the lake are muddy sand type. Among the inorganic phosphorous fractions, calcium-bound P (Ca-P) emerged as the most dominant fraction contributing 55 and 37 % of the total phosphorous (TP) respectively in pre- and post-monsoon seasons, respectively. Contribution of loosely bound phosphorus (Lo-P) to the TP in lake system was the lowest (

The geochemical association of some trace metals (Fe, Mn, Ni, Cu, Cr, and Pb) were sequentially extracted from bulk sediments of the Chilika lagoon, India. The low elemental concentration, except Pb, in the exchangeable phase suggests poor availability to bottom dwellers. However, slightly higher abundance of Pb in the exchangeable phase at station 4 (9.9%) and station 6 (9.5%) is mainly related with waste from major fishing jetties. The carbonate-bound phase reflects heavy metal distribution of detrital origin along with biological decomposition in the lagoon. A relatively higher percentage of Mn in the reducible phase is attributed to the flocculation of its colloids. The concentrations of Cu, Ni, and Pb show their higher affinity to the organic-bound fraction. The absolute metal concentrations in the residual fraction was Fe > Mn > Ni > Cu > Pb > Cr, which reflects the predominance of physical weathering, a high erosion rate, and a high sedimentation rate in the lagoon. According to Risk Asses...

A study was carried out at Kalpakkam coast to find out the distribution of various fractions of phosphorus (P) in the marine sediment during pre-northeast monsoon period. Samples were collected from ten locations covering ~80 km2 of the inner-shelf region. Sedimentary parameters such as sand, silt, clay, and organic carbon percentage were analyzed in order to find out their relation with various P fractions. The sediment was found to be predominantly sandy in nature with low silt and clay content. Among all the fractions (loosely bound (LoP), calcium bound (CaP), iron bound (FeP), aluminum bound (AlP), and organic (OP)), CaP fraction constituted the largest portion (68.7 %) followed by organic fraction (16.3 %). The bioavailable P fractions ranged from 5 to 44 % of the total P (TP) content. Relatively high LoP content was observed at the offshore locations with comparatively high mud percentage as compared with the near-shore locations. As FeP and AlP concentrations were directly proportional to the amount of fine-grain sediment, the low levels of these fractions found in this coastal area were therefore attributed to the sandy nature of the sediments. The order of abundance of the major forms of P in the surface sediments of Kalpakkam coast was as follows: CaP > OP > LoP > AlP > FeP.