Peer Reviewed Journal Articles (Inter.) (FT)

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Assessing temporal variation of coloured dissolved organic matter in the coastal waters of south eastern Arabian sea
(Springer, 2020) Minu, P.; Souda, V.P.; Baliarsingh, S.K.; Dwivedi, R.M.; Ashraf, P.M.
Coloured dissolved organic matter (CDOM) plays a major role in marine photochemical and biological processes and its optical properties are known to affect the underwater light penetration. This paper highlights in situ optical estimation and satellite retrieval of CDOM in deciphering its temporal variations in coastal waters of the South Eastern Arabian Sea. The study accentuated the source of CDOM as terrigenous origin during monsoon, of in situ productions during pre-monsoon and during post-monsoon of autochthonous-allocthonous origin. The matchup analysis for in situ and MODIS Aqua retrieved Adg443 exhibited bias which decreased by incorporating the seasonal component. The study also identified degrading bloom of Noctiluca scintillans as the source for exceptionally high CDOM in the area during January and February. The study demands to incorporate seasonal components and phytoplankton abundance while assessing the performance of CDOM algorithms in optically complex coastal waters.
Assessment of biodetrioration or rubber wood exposed to field conditions
(ELSEVIER, 2006) Edwin, L.; Ashraf, P.M.
Rubber wood (Hevea braslliensis) can be used commercially for the construction of fishing boats, which are subjected to biodegration in the water, and on land both with and without soil contact. In order to obtain data on the natural durability of this wood, the extent of biodeterioration was assessed through visual observation, changes in the specific gravity of the wood and loss in the compressive strenght of wood panel after 90 and 150 days in field tests. Changes in wood chemistry due to biodeterioration under field conditions wre also characterized through Fourier transform infrared (FTIR)spectroscopy. Test samples in soil burial tests (graveyard tests) wre more severely damaged than panels exposed to atmospheric weathering or immersed in sea water below the low tide mark. Strength losses in panels exposed to the marine and atmospheric conditions were not commensurate with the weight losses.
Biofouling control using nano silicon dioxide reinforced mixedcharged zwitterionic hydrogel in aquaculture cage nets
(2019) Mohan, A.; Ashraf, P.M.
Biofouling in aquaculture cages negatively affects the farm productivity, and it requires huge sums of money and labor for its management. A superhydrophilic pseudozwitterionic hydrogel, N-isopropylacrylamide (NIPA) + [2-(methacryloyloxy)ethyl]trimethylammonium (TMA) + 3-sulfopropyl methacrylate (SA) copolymer, is considered as a potential antifouling agent. The present study aimed to synthesize a nano silicon oxide reinforced NIPA−TMA−SA mixed-charged zwitterionic hydrogel over polyaniline-coated polyethylene aquaculture cage nets through the in situ microwave reaction and to test its biofouling resistance. The study highlighted the formation of stable coating over polyethylene, four different treatments, and their effective inhibition of fouling compared with the untreated one. Six month’s immersions of treated nettings in the estuarine environments demonstrated that the biofouling inhibition by nano silicon oxide reinforced zwitterionic hydrogel-coated polyethylene was unable to satisfy the industrial standards but made the samples free from hard-shelled fouling organisms compared with untreated controls. More research is needed to improve the quality of the coatings. The mixed-charged zwitterionic hydrogel with nano silicon oxide showed medium hydrophilic nature. Fourier transform infrared, scanning electron microscopy, and spectroscopic evaluation showed the successful formation of hydrogel over the aquaculture cage net. Nano silicon oxide reinforced in the matrix through hydrogen and coordination bonding between NH2 and carbonyl of the polymeric chain, respectively.
Biofouling resistant polyethylene cage aquaculture nettings: A new approach using polyaniline and nano copper oxide
(2017) Ashraf, P.M.; Sasikala, K.G.; Thomas, S.N.; Edwin, L.
Biofouling in cage aquaculture netting causes clogging of meshes, increased stress and retards the growth of fishes. This paper describes a new method of protecting polyethylene cage nettings from biofouling using polyaniline and nano-copper oxide. Polyaniline was synthesized in-situ over polyethylene cage netting material and subsequently treated with nano copper oxide. The modified netting material exposed to estuarine environment exhibited excellent fouling resistance. FTIR characterization confirmed the formation of polyaniline and adsorption of nano copper oxide over the netting material. SEM and AFM evaluation showed uniform coating of polyaniline and nano copper oxide on the polyethylene-polyaniline (PE-PANI) matrix. The results highlight the potential application of polyaniline plus nano copper oxide coated polyethylene nettings in controlling biofouling in cage aquaculture.
Corrosion resistance of BIS 2062‑grade steel coated with nano‑metal‑oxide mixtures of iron, cerium, and titanium in the marine environment
(2018) Ashraf, P.M.; Anuradha, R.
BIS 2062-grade carbon steel is extensively used for fishing boat construction. The steel is highly susceptible to corrosion on the hull and welding joints under marine environment. Here, we demonstrate the application of a novel multifunctional nano-metal-oxide mixture comprised of iron, titanium, and cerium as a marine coating to prevent corrosion. The electrochemical performance of nano-metal-oxide mixture coatings, applied over boat-building steel, was evaluated at 3.5% NaCl medium. The nano-mixture surface coatings showed an efficient corrosion resistance with increased polarization resistance of 6043 Ω cm2 and low corrosion current density of 3.53 × 10−6 A cm−2. The electrochemical impedance spectral data exhibited improvement in the polarization resistance of outermost surface and internal layers. The coating responded faster recovery to normal state when subjected to an induced stress over the coating. The nano-material in the coating behaves as a semiconductor; this enhanced electronic activity over the surface of the steel.
Decomposition study of in vivo phytoplankton absorption spectra aimed at identifying the pigments and the phytoplankton group in complex case 2 coastal waters of the Arabian Sea
(Faculty of Oceanography and Geography, University of Gdansk/Springer, 2015) Shaju, S.S.; Minu, P.; Srikanth, A.S.; Ashraf, P.M.; Vijayan, A.K.; Meenakumari, B.
Phytoplankton modify the optical properties of the seawater by altering the subsurface light field. Information on the accessory pigments present in the phytoplankton helps to differentiate major phytoplankton classes or taxonomic groups. The variability in the absorption spectra of phytoplankton and particulate matter of case 2 coastal waters of the Southeastern Arabian Sea were studied from June 2010 to November 2011. The phytoplankton specific absorption coefficient, at 440 nm and 675 nm, a*ph (440) and a*ph (675) varied from 0.018 to 0.32 m2 mg-1 and from 0.0005 to 0.16 m2 mg-1, respectively. The 4th derivative spectra computed for each in vivo absorption spectrum showed that the amplitude of maxima obtained is proportional to the concentration of the chromoprotein which absorbed that wavelength. Regression of pigment concentration against the 4th derivative spectral coefficient showed that the measurements of particulate absorption could provide quantitative information on chlorophyll a and other accessory pigment concentrations. Fucoxanthin and diadinoxanthin, the carotenoid pigments found in the diatoms were identified from the derivatives peaks. The study demonstrates the utility of using the 4th derivative analysis as a tool to identify the dominating phytoplankton group and its pigment composition.
Development of CeO2 and TiO2- incorporated aluminium metal-composite matrix with high resistance to corrosion and biofouling
(Springer, 2008) Ashraf, P.M.; Shibli, S.M.A.
Cerium oxide (CeO2) is a potential corrosion inhibitor for aluminium, and titanium oxide (TiO2) is an efficient anti-fouling agent in the marine environment. The present study explored the possibility of incorporating CeO2 and TiO2 in aluminium to prepare a metal matrix composite that could have high corrosion and biofouling resistance under marine conditions. Such incorporation of CeO2 and TiO2 in pure aluminium offered high resistance to corrosion and biogrowth under marine conditions as evidenced during different tests. The specimens exhibited more anodic and stable open circuit potential throughout the period of the study. The optimum concentration of CeO2 and TiO2 was found to be 0.2 and 0.1%, respectively. The present results lay emphasis on the potential scope of the use of CeO2- and TiO2-incorporated aluminium in marine environments.
Development of graphene-nanometre-sized cerium oxide-incorporated aluminium and its electrochemical evaluation
(Springer, 2015) Ashraf, P.M.; Thomas, S.N.; Edwin, L.
Graphene–nanometre-sized cerium oxide-incorporated aluminium was prepared and its electrochemical and surface morphological characteristics were studied. The atomic force micrographs and scanning electron micrographs evaluation highlighted that the grapheme and nanometre-sized cerium oxide in aluminium had decreased the surface roughness and improved the surface morphological characteristics. The graphene: nanometresized cerium oxide (ratios 1:2 or 2:1) with lesser amounts of particle in the matrix showed excellent corrosion resistance in the marine environment as evidenced by linear polarization, electrochemical impedance and weight loss studies. Introduction of graphene in the aluminium matrix showed a barrier separation between the outermost layer and inner layer, increased roughness and increased corrosion. The material is found to be a potential candidate for use in marine environment.
Inter-annual variability in the inherent optical properties along the southeastern Arabian sea from 2009 to 2015
(Springer, 2020) Souda, V.P.; Minu, P.; Lotliker, A.A.; Shaju, S.S.; Ashraf, P.M.
A study was performed on the coastal waters of the southeastern Arabian Sea to understand the changes in the inherent properties of optically active substances (OAS). The objective of this study was to obtain insight into the temporal dynamics of OASs for various remote sensing applications. Both the absorption of light by phytoplankton (aph(440)) and detritus (ad(440)) varied the 2nd orders of magnitude, whereas the absorption of light by chromophoric dissolved organic matter (CDOM; aCDOM(440)) exhibited an increasing trend over the years. aCDOM(440) increased from 2009 to 2015 at a rate 0.012 m−1 year−1. The validation of the satellite data with in situ data indicated that ad(443) underestimated the in situ ad(443) when the in situ ad(443) was less than 0.3 m−1. The ternary analysis of ocean-colour-climate-change initiative (OC-CCI)–derived inherent optical properties (IOP) during the postmonsoon season indicated increased contribution by ad(443). Detritus was the primary light absorber in the coastal waters of Kochi followed by phytoplankton and CDOM. These long-term data sets and their seasonal variation will enable development of seasonal specific regional algorithms for chlorophyll-a, which are employed in potential fishing zone advisories and other applications.
Nano copper oxide incorporated polyethylene glycol hydrogel: An efficient antifouling coating for cage fishing net
(2016) Ashraf, P.M.; Edwin, L.
Netting materials used for cage aquaculture were always susceptible to clogging of mesh lumen due to biofouling. Here we report a microwave assisted in situ synthesis of nano copper oxide incorporated polyethyleneglycolmethacrylate based hydrogel over nylon fishing cage net and its evaluation for resistance to fouling. Physicochemical and morphological characteristics of the material were studied using UVevis spectrophotometry, FTIR, TEM and SEM. FTIR spectra showed the formation of the hydrogel e copper composite over the nylon twines through the amino/carbonyl groups of nylon with vinyl CH2 group of hydroxyethylmethacrylate. The SEM characterization exhibited a uniform thin film of composite formed over the nylon netting material. The hydrogel reinforced with 0.004% (wt/vol) copper oxide treated netting material exposed for 90 days to the estuarine environment exhibited excellent fouling resistance with lowest biomass accumulation. Copper oxide in the matrix played an important role synergistically along with hydrophilic hydrogel to deter the biofilm formation and hence attachment of fouling organisms over the nylon. This study highlights the composite as a potential candidate and efficient molecule to prevent fouling in the aquaculture cage nets.
Performance of operational satellite bio-optical algorithms in different water types in the Southeastern Arabean Sea
(Elsevier, 2016) Minu, P.; Lotliker, A.A.; Shaju, S.S.; Ashraf, P.M.; Sreenivasa Kumar, T.; Meenakumari, B.
Phytoplankton community characteristics in the coastal waters of the southeastern Arabian Sea
(The Chinese Society of Oceanography and Springer-Verlag Berlin Heidelberg, 2014) Minu, P.; Shahu, S.S.; Ashraf, P.M.; Meenakumari, B.
Remote sensing applications are important in the fisheries sector and efforts were on to improve the predictions of potential fishing zones using ocean color. The present study was aimed to investigate the phytoplankton dynamics and their absorption properties in the coastal waters of the southeastern Arabian Sea in different seasons during the year 2010 to 2011. The region exhibited 73 genera of phytoplankton from 19 orders and 41 families. The numerical abundance of phytoplankton varied from 14.235×103 to 55.075×106 cells/L. Centric diatoms dominated in the region and the largest family identified was Thalassiosiraceae with main genera as Skeletonema spp., Planktionella spp. and Thalassiosira spp. Annual variations in abundance of phytoplankton showed a typical one-peak cycle, with the highest recorded during premonsoon season and the lowest during monsoon season. The species diversity index of phytoplankton exhibited low diversity during monsoon season. Phytoplankton with pigments Chlorophyll a, Chlorophyll b, Chlorophyll c, peridinin, diadinoxanthin, fucoxanthin, β-carotene and phycoerythrobilin dominated in these waters. The knowledge on phytoplankton dynamics in coastal waters of the southeastern Arabian Sea forms a key parameter in bio-optical models of pigments and productivity and for the interpretation of remotely sensed ocean color data.
Reinforcing aluminium with cerium oxide: a new and effective technique to prevent corrosion in marine environments
(Elsevier, 2007) Ashraf, P.M.; Shibli, S.M.A.
Cerium oxide (CeO2) is one of the potential choices to be explored for the protection of aluminium from corrosion. However, usage of cerium ions for surface modification of aluminium would not yield any potential effect in aggressive marine environments. Metal matrix composites of aluminium can have all the merits of aluminium such as density, strength, ductility and cost. In the present study, corrosion of aluminium in saline environment was significantly suppressed by means of reinforcing the aluminium with cerium oxide. The presence of cerium oxide in the matrix did not facilitate the formation of Al2O3 which would cause potential re-shift after few days due to the onset of pitting. The present results strongly lay emphasis on the potential scope of use of CeO2 for protection of aluminium in marine environments.
Studies on the seasonal changes of phosphorus in the marine environments off Cochin
(Elsevier, 2006) Ashraf, P.M.; Edwin, L.; Meenakumari, B.
Studies were conducted to evaluate the changes of phosphorus in marine water and sediments of seven stations in the coastal areas off Cochin. Samples were collected on a monthly basis from January 2001 to December 2001. Results revealed higher levels of P in marine water samples collected during October–December 2001. The marine water P ranged from 0 to 0.38 ppm throughout the year. Speciation of P in marine sediment revealed that the Al bound P was maximum compared to Fe, Ca and organic bound P. Loosely bound and aluminium bound P was maximum during October–December especially in 10 and 20 m depth stations off Narakkal. Fe bound P was found to be least in June and September and highest during January–April. Low levels of Ca bound P were detected in samples collected during January–March and inorganic P was maximum in June and September. Organic bound P was maximum in 10 m depth stations and also during June and September. Phosphate fractions varied with locations and exhibited seasonal fluctuations.

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