Ecological health assessment of a coastal ecosystem: Case study of the largest brackish water lagoon of Asia

This study focuses on the ecological health assessment of Chilika, a shallow lagoon present in east coast of India, through nutrient stoichiometry and trophic state index (TSI). Multivariate statistical analysis such as ANOVA, Pearson's correlation, Principal Component Analysis (PCA), and Discriminant Analysis (DA) were employed for data interpretation. Nutrient stoichiometry revealed that the Chilika Lagoon experiences phosphorus limitation with regard to nitrogen and silicate (N:P:Si = 16:1:16) throughout the study period. As per the computed TSI values, the southern sector (SS), central sector (CS), and outer channel (OC) were assigned with a mesotrophic status, whereas the northern sector (NS) was assigned with the eutrophic status. From PCA, total nitrogen was found to be negatively correlated with salinity and positively correlated with silicate, thus indicating that the major source of nitrogen in the lagoon was freshwater ingress by rivers with high silicate content. DA indicated that it was successful in discriminating the groups as predicted

BisGMA-polyvinylpyrrolidone blend based nanocomposites reinforced with chitosan grafted f-multiwalled carbon nanotubes

In this work, initially a non-destroyable surface grafting of acid functionalized multiwalled carbon nanotubes (f-MWCNTs) with biopolymer chitosan (CS) was carried out using glutaraldehyde as a cross-linking agent via the controlled covalent deposition method which was characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Then, BisGMA (bisphenol-A glycidyldimethacrylate)-polyvinylpyrrolidone (PVP) blend was prepared (50:50 wt%) by a simple sonication method. The CS grafted f-MWCNTs (CS/f-MWCNTs) were finally dispersed in BisGMA-PVP blend (BGP50) system in different compositions i.e. 0, 2, 5 and 7 wt% and pressed into molds for the fabrication of reinforced nanocomposites which were characterized by SEM. Nanocomposites reinforced with 2 wt% raw MWCNTs and acid f-MWCNTs were also fabricated and their properties were studied in detail. The results of comparative study report lower values of the investigated properties in nanocomposites with 2 wt% raw and f-MWCNTs than the one with 2 wt% CS/f-MWCNTs proving it to be a better reinforcing nanofiller. Further, the mechanical behavior of the nanocomposites with various CS/f-MWCNTs content showed a dramatic increase in Young’s Modulus, tensile strength, impact strength and hardness along with improved dynamic mechanical, thermal and electrical properties at 5 wt% content of CS/f-MWCNTs. The addition of CS/f-MWCNTs also resulted in reduced corrosion and swelling properties. Thus, the fabricated nanocomposites with optimum nanofiller content could serve as low cost and light weight structural, thermal and electrical materials compatible in various corrosive and solvent based environments

Dynamics and quantification of dissolved metals in a highly contaminated river-estuarine system

1310-1322Dynamics of heavy metals such as Fe, Mn, Co, Ni, Cu, Zn, Cr, Pb and Cd in surface water of Brahmani river-estuarine system were studied taking 25 samples from different sampling locations along the complete stretch. Irrespective of season, Fe was most abundant in both river (avg. 260.15 µg/l ) and estuarine (avg. 119.9 µg/l) samples, whereas Cd (avg. 1.59 µg/l) and Co (avg.1.55 µg/l) were the lowest in the river and estuarine samples respectively. The average concentrations of all the dissolved metals were much higher than the world river average. The average concentrations Cr and Cd for the river were above the criteria of maximum concentration (CMC) as prescribed by US Environmental Protection Agency. Results of factor analyses revealed that anthropogenic contributions were the source for the increase in dissolved metal concentrations. Canonical discriminate function indicated that it was moderately successful in discriminating the groups as predicted. River Brahmani with an annual discharge of 18.58 x 106m3 carries 6.907 x 103 tons of total heavy metals into Bay of Bengal and the calculated rate of erosion in the basin is 176.582 kg km-2 year-1