On the marine atmospheric boundary layer characteristics over Bay of Bengal and Arabian Sea during the Integrated Campaign for Aerosols,gases and Radiation Budget (ICARB)

Detailed measurements were carried out in the Marine Atmospheric Boundary Layer (MABL) during the Integrated Campaign for Aerosols, gases and Radiation Budget (ICARB) which covered both Arabian Sea and Bay of Bengal during March to May 2006. In this paper, we present the meteorological observations made during this campaign. The latitudinal variation of the surface layer turbulent fluxes is also described in detail.     

Process-sedimentological challenges in distinguishing paleo-tsunami deposits

There has been a lively debate since the 1980s on distinguishing between paleo-tsunami deposits and paleo-cyclone deposits using sedimentological criteria. Tsunami waves not only cause erosion and deposition during inundation of coastlines in subaerial environments, but also trigger backwash flows in submarine environments. These incoming waves and outgoing flows emplace sediment in a wide range of environments, which include coastal lake, beach, marsh, lagoon, bay, open shelf, slope and basin. Holocene deposits of tsunami-related processes from these environments exhibit a multitude of physical, biological and geochemical features. These features include basal erosional surfaces, anomalously coarse sand layers, imbricated boulders, chaotic bedding, rip-up mud clasts, normal grading, inverse grading, landward-fining trend, horizontal planar laminae, cross-stratification, hummocky cross-stratification, massive sand rich in marine fossils, sand with high K, Mg and Na elemental concentrations and sand injections. These sedimentological features imply extreme variability in processes that include erosion, bed load (traction), lower flow regime currents, upper-flow regime currents, oscillatory flows, combined flows, bidirectional currents, mass emplacement, freezing en masse, settling from suspension and sand injection. The notion that a ??tsunami?? event represents a single (unique) depositional process is a myth. Although many sedimentary features are considered to be reliable criteria for recognizing potential paleo-tsunami deposits, similar features are also common in cyclone-induced deposits. At present, paleo-tsunami deposits cannot be distinguished from paleo-cyclone deposits using sedimentological features alone, without historical information. The future success of distinguishing paleo-tsunami deposits depends on the development of criteria based on systematic synthesis of copious modern examples worldwide and on the precise application of basic principles of process sedimentology.     

Hyperspectral Radiometry to Characterise Dunite Alteration and Magnesite Deposits of Salem,South India

This work reports the results of insitu surveys, hyperspectral-radiometry and geochemistry for dunite-alteration and magnesite mapping in the Salem, southern India. Spectral parameters such as the strength of absorption in the 865 nm and 2,300 nm range for Fe²⁺ and CO3^2- respectively, and the position of absorption trough were derived from the laboratory spectra for 13 samples. It is observed that dunite alteration and conversion to magnesite produce measurable changes in the VIS-NIR-SWIR spectra due to a transition from the silicate-dominated rocky composition to carbonate-dominated industrial mineral composition. Relationship between the spectra and mineralogy suggests that we can identify the varieties of magnesite using hyperspectral radiometry.     

Vertical profiles of aerosol black carbon in the atmospheric boundary layer over a tropical coastal station: Perturbations during an annular solar eclipse

Altitude profiles of aerosol black carbon (BC) in the atmospheric boundary layer (ABL) over a tropical coastal station, Trivandrum have been examined on two days using an aethalometer attached to a tethered balloon. One of these days (15th January, 2010) coincided with a (annular) solar eclipse, the longest of this century at this location, commenced at 11:05 local time and ended by 15:05, lasting for 7 min and 15 s (from 13:10:42), with its maximum contact occurring at ~ 13:14 IST with ~ 92% annularity, thereby providing an opportunity to understand the eclipse induced perturbations. Concurrent measurements of the ABL parameters such as air temperature, relative humidity and pressure were also made on these days to describe the response of the ABL to the eclipse. BC profiles, in general, depicted similar features up to an altitude of ~ 200 m on the eclipse day and control day, above which it differed conspicuously with profiles on eclipse day showing increasingly lower concentration as we moved to higher altitudes. Examination of the meteorological profiles showed that the altitude of maximum convection rapidly fell down during the eclipse period compared to that on control day indicating a rather shallow convection on eclipse day. Comparison of diurnal variations of BC at the surface level showed that the rate of decrease in BC during daytime on the eclipse day was smaller than that on the control day due to the reduced convection, shallow ABL and consequent reduction in the ventilation coefficient. Moreover the time of the nocturnal increase has advanced by ~ 1:30 h on the eclipse day, occurred at around 19:30 IST in contrast to all the other days of January 2010, where this increase usually occur well after 20:30 IST, with a mean value of 21:00 IST. This is attributed to the weak sea-breeze penetration during the eclipse day, which led to an early onset of the land breeze.     

Environmental hydrogeochemistry and genesis of fluoride in groundwaters of Dindigul district, Tamilnadu (India)

Fluoride (F^?) is an indispensable element for the human’s skeletal and dental health at prescribed levels and becomes lethal at higher levels. Spatial–temporal variability of F^? and its geochemical control/association with other dissolved ions in groundwater in the Dindigul district of Tamilnadu (India) were conducted to describe the geochemical dynamics of F^– in response to seasonal variability. High concentrations of fluoride (≥1.5 mg L^?1) were observed in the northern region of the district. High levels of F^? were observed in non-monsoon periods and low levels in monsoon, because of dilution by precipitation. Bicarbonate was well correlated with F^? which explains that both ions were derived from the weathering. While F^? has a very weak correlation with silica, this implies that the silicate weathering does not supply F^? to the groundwater system. The F^? pollution in Dindigul groundwaters is mainly driven by two factors: (1) the geogenic weathering inputs, the geology of this area mainly comprises fluoride bearing minerals (e.g. hornblende biotite gneiss and charnockite); (2) the anthropogenic inputs (agri-fertilizers and tannery waste). Further, F^? in the study area is mainly attributed to geogenic sources during pre and postmonsoons and anthropogenic sources in monsoon periods.     

Assessment of genotoxic and humoral immune system alterations in silica exposed workers from pottery industries in South India

Chemicals, especially silica, have been suspected to cause genetic alterations in pottery industry workers. The present study aims to analyze the frequency of chromosomal aberrations (CA), micronucleus (MN) and DNA damage (comet assay) in the peripheral blood lymphocytes and the immunological alterations workers chronically exposed to silica and in control subjects. In our study, 50 silica exposed workers and 35 control subjects were recruited and silica level was measured by respirable dust and respirable quartz concentrations of badge dosimeter. The serum immunoglobulins (IgM, IgG, and IgA) of all the subjects were measured by using ELISA method. The individuals exposed to silica have a significant increase in the frequency of CA, MN and the total DNA damage (p < 0.05). Immunoglobulin elevation on silica exposed workers was statistically significant (p < 0.05) on comparison with their respective controls. Investigation of the smoking and alcohol habitats coupled with silica exposure in exposed and control subjects represents alcohol consumption and smoking as additional risk factors and must be avoided. Multiple linear regression analysis obtained for CA, MN and comet assay confirm these tests as biomarkers for silica exposed pottery workers. Some confounding factors also showed significant influence on exposed subjects. These results indicate the mutagenic risk in the working environment has a high probability of association with the silica dust exposure in pottery industries. Nevertheless, the present study will create awareness and public concern not only among the silica exposed workers but also to the welfare of their progeny.     

Climate change impacts on fish catch in the world fishing grounds

Climate change impacts on fish catch in the major fishing areas in the world oceans using a new method for forecasting of fish catch is presented with probability statements. The data on historical behaviour of surface water temperature and fish catches were analyzed and processed to assess the dynamics of spatial temperature distribution and fish catches for the world oceans. An analysis shows that the species diversity of fish catch does not change significantly with time and hence the total fish catch was used as the main dynamic variables, practically without loss of information about the dynamic properties of the system. A predictor was constructed to predict the dynamics of fish catch for new values of four moments for a future temperature distribution and the predictor’s power was estimated with a probability statement. Based on the predicted temperatures for the years 2000–2100, the fish catches in the Pacific, Atlantic and Indian Oceans have been predicted with a probability statement.     

Intercomparison of Air–Sea Interface Fluxes over the Yellow Sea and Korea Strait: Impact of Tsushima Warm Current

Surface-layer meteorological observations obtained from oceanic buoys over the Korean Strait and the Yellow Sea are used to estimate surface-layer turbulent fluxes of heat, moisture and momentum over the East-Asian Marginal Seas. Special emphasis is paid towards explanation of the impact of the Tsushima warm current flowing through the Korean Strait on air–sea interface fluxes. During the active phase of the Tsushima warm current, when the difference in sea surface temperature and air temperature becomes as large as 8°C, the sensible heat flux increases to a value of about 135 W m⁻², while the latent heat flux is around 200 W m⁻². The study attempts to broaden our understanding on the air-sea interaction processes over the Yellow Sea and Korean Strait.     

Changes in benthic macrofaunal assemblages in relation to bottom trawling in Cuddalore and Parangipettai coastal waters, Southeast coast of India

Variations in benthic biodiversity owing to bottom trawling were studied in the inshore waters of Parangipettai (Lat.11°24′N; Long. 79°464′E) and Cuddalore (Lat. 11°434′N; Long. 79°494′E), India from February 2009 to January 2010. Four stations each in Parangipettai and Cuddalore were prepared and established. A total of 114 species in Parangipettai and 101 in Cuddalore were found. The population density showed a maximum (10,387 no. m-2) in Parangipettai in the sample collected before trawling and a minimum (40no. m^?2) in Cuddalore in the samples collected after trawling. Among the faunal groups, polychaetes topped the list followed by other groups of organisms both in the samples before and after trawling. Shannon diversity varied from 2.23 to 4.24, 1.85 to 3.45; Margalef richness from 3.2 to 5.9, 2.57 to 4.25; Pielou’s evenness varied from 0.79 to 0.94, 0.81 to 0.88 in the samples collected before and after trawling respectively in Parangipettai. In Cuddalore waters, Shannon diversity ranged from 2.15 to 3.85, 1.92 to 3.15; Margalef richness from 2.95 to 5.2, 2.24 to 3.95 and Pielou’s evenness index from 0.84 to 0.91, 0.79 to 0.82 in the samples before and after trawling respectively. Multivariate methods also showed distinct variations in terms of species composition and abundance between regions and samples.     

Vertical structure of sea-breeze circulation over Thumba (8.5°N,?76.9°E,?India) in the winter months and a case study during W-ICARB field experiment

This research article aims at characterization of the sea-breeze circulation over Thumba (8.5°N,?76.9°E,?India) in the winter season from December 2008 to February 2009, when this mesoscale circulation over the study domain was prominent. The characteristics of sea-breeze circulation cell comprising sea-breeze and compensatory return flow are investigated for clear-sky and cloudy days. The study indicated delayed onset of sea-breeze on the cloudy days as compared to the clear-sky days and the vertical thickness of sea-breeze circulation cell was found to be larger for the clear-sky days. Vertical thickness of the return flow for both clear-sky and cloudy days was larger than that of the sea-breeze flow. Simultaneous observations of upper-air meteorological parameters obtained through balloon-borne GPS sonde ascents carried out from Thumba and its adjoining coastal ocean on 29 January 2009 as part of the Winter phase of Integrated Campaign for Aerosols, gases and Radiation Budget (W-ICARB) are utilized for a case study towards investigation of diurnal evolution of the sea-breeze circulation cell. Results obtained from this study indicated systematic evolution of sea-breeze circulation over Thumba, however, it was not very clear over ocean which is attributed to cloudy conditions that prevailed on the day of measurement.