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Bio-diffusion mixing rates (D) were estimated from depth profiles of excess Pb and Cs in three sediment cores collected from Mumbai Harbour Bay (MHB) using a steady state vertical advection - diffusion model. The mean of Pb and Cs derived D values along the studied area were obtained to be about 23 and 36 cmy respectively. These derived values were within the range of literature values reported for other equivalent environment internationally. The relatively higher D values for Cs profiles demonstrated that particles have diffused more intensely within the surface layer of sediments over 1 year. Conversely, low D values for Pb indicate slow mixing rates in the sediment profile which might be resulted from low Pb flux and diffusion of Rn to the seafloor. The significant differences between Pb and Cs derived D values among cores indicate that there appeared to be as regional differences in sediment properties and local variability in the intensity of seafloor mixing. Furthermore, D values also depend on differences in characteristic time and depth scales of radionuclides in cores, benthic fauna abundances, organic carbon flux to the sediments and primary production in overlying surface waters. Comparison of Pb derived D values with those calculated from Cs distributions reveals better agreement for core 2 than core 1 and 3. The agreement may be fortuitous because Cs appears significantly deeper than Pb in all cores. It was also observed that D values increases as sediment accumulation rate increases for both radionuclide. [ABSTRACT FROM AUTHOR]

Measurements of the vertical concentration profile of deposited Pb and its parent (Ra) in cores of recent marine sediment of Mumbai Harbor Bay (MHB) were made to determine the various depth distribution parameters (sedimentation rate, age of sediment, total inventory, fluxes, residence times, scavenging rate, linear attenuation coefficient and relaxation mass depth). Overall, the profile distributions of Ra and Pb showed a decreasing trend with increasing the depth. The mean of sedimentation rate in the studied area was obtained to be about 0.76 cm year which corresponds to average age of sediment of about 56 years. The average total deposited Pb for the studied sediment profile was 9.68 k Bq m and correspondingly the average value of fluxes of total Pb and excess Pb (atmospheric flux) were 0.59 and 0.32 k Bq myear, respectively. The residence time of Pb was in the range of 26-226 years throughout the sediment profile and showed generally an increasing trend from top to bottom. The mean relaxation mass depth (h) derived from the depth profile of Pb at the studied area was about 190 kg m. The negative association between clay content of cores and the h of Pb indicates that as the clay content increases, the penetration depth of deposited Pb in sediment profile decreases. [ABSTRACT FROM AUTHOR]

The vertical concentration profile of Cs in cores of marine sediment of Mumbai Harbor Bay has been studied by the compartment and the diffusion-convection models. Based on the measured concentrations of Cs in the sediment layers, the various transport parameters such as sedimentation rate, residence half- time, effective migration velocity, diffusion coefficient and the convective velocities were determined. The sedimentation rate was determined to be 1.61, 1.03 0.69 and 1.25 cm year from the slope of lines obtained from the depth profile of Cs in cores using a least-square fitting method at site 1, 2, 3 and 4 respectively. The mean residence half-times, ranging from 11 to 35 years were observed to be the highest at the upper layers (up to 8 cm) of all sites and decreased with sediment depth. Subsequently, the ranges of mean value of effective vertical migration velocity in the same layers were between 0.15 and 0.46 cm year. As expected, the vertical migration in the upper sediment layers was very slow and thereafter increased slowly in the succeeding layers (12 cm onwards) of all sites with a mean ranging from 1.11 to 4.13 cm year. The obtained migration velocities were quite higher than those reported in literatures for global fallout. The convective velocity and diffusion coefficient at each site were assumed to be constant in the whole depth and calculated under the assumption of steady state. Using a depth-zoned bioturbational mixing model, the estimated biological diffusion coefficients ranged from 7 × 10 to 3.8 × 10 cms which were within the literature values reported for shallow coastal environments and deep sea. [ABSTRACT FROM AUTHOR]

The present work shows the activity levels of Ra, Ra, K and Cs in bottom sediments collected from eight locations of Mumbai Harbour Bay. The study has shown that K and Ra concentration is nearly uniform throughout the studied area while Ra and Cs are more concentrated in the southern regions of the bay. The significant variation in the activity levels of radionuclides within the study site might be due to their sorption/desorption processes onto the surface of sediment materials. The low mean value of Ra/Ra ratio (0.72) in the sediments indicates that U has relatively greater solubility and mobility than Th. Similarly, low activity ratio (0.18) for Cs/K reflects the presence of very high content of K in sediment due to presence of primary minerals in sediment. Silt and clay were reported to dominate the composition of the sediment. A significant positive correlation between Ra and Ra and Cs and K suggest a similar origin of their geochemical sources and identical behavior during transport in the sediment system. [ABSTRACT FROM AUTHOR]

Enrichment factor (EF) of elements including geo-accumulation indices for soil quality and principal component analysis (PCA) were used to identify the contributions of the origin of sources in the studied area. Results of 40K, 137Cs, 238U and 232Th including their decay series isotopes in the agricultural soil of Mansa and Bathinda districts in the state of Punjab were presented and discussed. The measured mean radioactivity concentrations for 238U, 232Th and 40K in the agricultural soil of the studied area differed from nationwide average crustal abundances by 51, 17 and 43 %, respectively. The sequence of the EFs of radionuclides in soil from the greatest to the least was found to be 238U > 40K > 226Ra > 137Cs > 232Th > 228Ra. Even though the enrichment of naturally occurring radionuclides was found to be higher, they remained to be in Igeo class of ‘0’, indicating that the soil is uncontaminated with respect to these radionuclides. Among non-metals, N showed the highest EF and belonged to Igeo class of ‘2’, indicating that soil is moderately contaminated due to intrusion of fertiliser. The resulting data set of elemental contents in soil was also interpreted by PCA, which facilitates identification of the different groups of correlated elements. The levels of the 40K, 238U and 232Th radionuclides showed a significant positive correlation with each other, suggesting a similar origin of their geochemical sources and identical behaviour during transport in the soil system. [ABSTRACT FROM PUBLISHER]

Abstract: In this study, the concentration of acid and water-soluble ions (Na+, K+, Mg++, Ca++, F−, Cl−, NO3 − and SO4 − −) in different particle size range (>1.1–<2.0μm, >2.0–<3.3μm, >3.3–<4.7μm, >4.7–<5.8μm, >5.8–<9.0μm and >9μm–<10μm) of PM10 atmospheric aerosols collected by six stages Anderson Cascade Impactor were determined using conductivity suppressed ion-chromatography system. Suspended particulate matters in the form of respirable (PM10) aerosols were collected on the roof of a three storied building at a height of 20m above the ground, at Bhabha Atomic Research Centre (BARC), Mumbai using Hi-Volume Sampler (HVS) with Whatman glass fiber filter paper during the period of March–June 2009. The sequence of solubility of ions in both extractants (acid+water) of PM10 aerosols from greatest to least was found to be Na+ >Ca++ >K+ >Cl− >F− >Mg++ >NO3 − ≈SO4 −−. The average concentration of Na+, K+, Mg++, Ca++, F−, Cl−, NO3 − and SO4 −− in PM10 aerosols was estimated to be 13.36g/kg, 3.76g/kg,0.251g/kg,3.771g/kg,0.833g/kg,1.17g/kg, 81μg/kg and 290μg/kg respectively. The enrichment of particular ion in soluble components may be due to its high abundance in PM10 aerosols, less sorptivity with the tiny solid particles of atmospheric dust, high extractability and leachability, high solubility and mobility. By classifying the PM10 aerosols into two categories viz fine particle (<2.5μm) and coarse particle (>2.5μm–<10μm), it was found that generally, in the fine particle, the geometric mean concentration of total soluble ions in acid and water components was found to be higher than coarse particle. Overall, it was also observed that generally as particle size increases, the geometric mean concentration of soluble ions in both extractants of PM10 aerosols decreases. [Copyright &y& Elsevier]