Discrimination between anthropogenic (pollution) and lithogenic magnetic fraction in urban soils (Delhi,India) using environmental magnetism

In this paper magnetic property of the Delhi topsoil has been used to characterize the potentially polluted areas in terms of magnetic minerals and grain (Magnetic Domain) concentration as a factor of toxic metals and other mutagenic pollutant concentration. The Saturation magnetisation (Ms) and Saturation remanence (Mrs) has been taken as proxy for ferrimagnetic mineral concentration. However, delineation of anthropogenic magnetic fraction from lithogenic (geogenic) magnetic fraction has been done by the paramagnetic/diamagnetic contribution of soil with the fact that the fresh soil contains higher paramagnetic and diamagnetic minerals than polluted. Predominantly, the topsoils of Delhi are dominated with ferrimagnetic minerals (Magnetite and Maghemite phase). Significantly the industrial areas contain highest concentration of the ferrimagnetic minerals with negligible paramagnetic/diamagnetic fraction which leads to anthropogenic contribution. Heavy traffic and densely populated areas of the Delhi exhibit moderate to low soil pollution while green areas show lowest with higher paramagnetic/diamagnetic contribution. The soils in Delhi are dominated with Pseudo-Single Domain (PSD) magnetic grain, though the industrial areas in Delhi show coarser Multidomain (MD) grains in comparison to Stable Single Domain (SSD) in forest areas. Our study reveals that the fine grain particle does not show significant link with higher concentration of ferrimagnetic minerals at least in soils. The presence of the lithogenic magnetite crystal in the forest soil and anthropogenically produced spherules in industrial areas and higher concentration of the heavy metal in Delhi soil strengthen our findings.     

Spatial geochemical variation of major and trace elements in the marine sediments of Mumbai Harbor Bay

The resulting concentration data sets of major (Na, K, Mg, Ca and Fe) and trace elements (Cu, Ni, Co and Mn) in bed and suspended sediments were used to evaluate the enrichment factor for anthropogenic influences and principal component analysis for identifying the origin of source contributions in the studied area. Normalization of metals to Fe indicated that high enrichment factors in the bed sediment were in the order of Co > Cu > Na > Ca > Ni except Mg, K and Mn while for suspended sediments, only Co has a high enrichment factor. High enrichment of Co and Cu reflected the contamination of sediments from anthropogenic sources. The high influence of Na and Ca in sediments may be caused for seawater salinization factor. A significant positive correlation among enrichment factors of various elements of interest suggests a common origin/identical behavior during transport in the sediment system.     

Role of environmental heterogeneity in structuring the macrobenthic community in a tropical sandy beach,west coast of India

In most ecosystems, community structure emerges as a result of the complex interaction between biotic and environmental variables. Sandy beaches connected to adjacent ecosystem like estuaries/creeks provide an opportunity to understand the role of the environment on the community. Kalbadevi beach along the central west coast of India, invaded by creeks at the northern and southern ends, provides an opportunity to investigate the role of environmental heterogeneity in structuring the intertidal macrofaunal communities. Further, the annual tropical rainfall brings about drastic changes in the environmental parameters. Seasonal survey was carried out at 10 transects covering the entire ~5-km beach of Kalbadevi for environmental and macrofaunal studies. We quantified the abundance, biomass, assemblage structure and distribution of macrofauna at different spatio-temporal scales. The univariate and multivariate analyses showed significant spatio-temporal variability in the biotic and abiotic variables. BIOENV analyses showed the best correlation with OC, phaeopigment and grain size. High abundance of macrofauna in the north and south was due to food availability, influenced by the creek. The low abundance during monsoon and subsequent increase in the post-monsoon can be attributed to annual spawning and recruitment of tropical fauna. Therefore, the present research suggests that the other environmental variables also play an important role in structuring the macrofauna of sandy beach. This supports our hypothesis that environmental heterogeneity influences the structuring of macrofaunal community.     

Some observations from radiometric ‘8 bit’ data of sediment thin sections based on alternative petrographic image analysis method

This paper deals with the experiment of sediment microstructure analysis especially microfabric mapping by digital imaging. For that purpose the greyscale images (Red band from RGB combination) of the thin sections have been prepared from the selected 12 samples. The basis of this mapping is the reflectance capacity of different sediments which is influenced by the physical parameters like grain size and colour. The reflectances of different sediments are represented in digital format by different DN values from 0–255 within the radiometric ranges of ‘8 bit’ data. Density slicing has been chosen as the method of microstructure mapping in this research. This study shows that lower DN values normally present dark coloured coarser sand and clay while higher DN values present light coloured finer sediment samples. In the selected samples for this study the maximum DN value has been found from micaceous materials. Another remarkable thing observed from the microfabric mapping is that the presence of coarser sediments forms complex microfabric pattern than the finer sediments in the study area. Though this method have some demerits, still its simple technique can be very useful for accurate microstructure analysis.     

First record of metazoan eggs and embryos from early Cambrian Chert Member of Deo ka Tibba Formation,Tal Group,Uttarakhand Lesser Himalaya

The phosphatized globular to sub-oval metazoan eggs with distinctively ornamented covering and phosphatized polar lobe forming embryos are recorded for the first time from the black phosphatic chert lenticles and bands of early Cambrian Chert Member of Deo ka Tibba Formation, Tal Group, Uttarakhand Lesser Himalaya. Similar metazoan eggs have been recorded earlier from early Cambrian rocks of Shaanxi Province, China, northwestern Canada, Australia, Mongolia, Siberia and Kazakhstan. These eggs are found in association with Small Shelly Fossils (SSF) and may belong to them. However, polar lobe forming embryos have been earlier recorded from Neoproterozoic rocks of southwestern China only. Similar embryos are common in modern molluscs and bilaterians.     

Clustering of Earthquake Events in the Himalaya - Its Relevance to Regional Tectonic Set-up

The earthquake events of Himalaya of magnitude ≥5.0 from the time window 1905–2000 are statistically analysed. The inter-event time between earthquakes shows Hurst phenomena of temporal clustering which are spatially located in five distinct domains along the Himalayan fold-thrust belt. Out of these, two domains, one around Uttaranchal-Nepal border and the other around Nepal-Sikkim border reveal maximum number of temporal clusters and thus considered as seismically most potential zones of the Himalaya. Both these zones are located at the interface of the orthogonally disposed major tectonic discontinuities of the Peninsular Shield and Himalayan fold-thrust belt. Such zones are geologically most favourable locales for strain accumulation during later-tectonic movement. Statistical analysis points towards a probability of recurrence of seismic events in near future in these two zones. However, validity of such statistical results can be ascertained by detailed geological and geophysical modelling of the terrain.     

Shoreline change analysis and its application to prediction: A remote sensing and statistics based approach

Shoreline change analysis and prediction are important for integrated coastal zone management, and are conventionally performed by field and aerial surveys. This paper discusses an alternative cost-effective methodology involving satellite remote sensing images and statistics. Multi-date satellite images have been used to demarcate shoreline positions, from which shoreline change rates have been estimated using linear regression. Shoreline interpretation error, uncertainty in shoreline change rate, and cross-validation of the calculated past shorelines have been performed using the statistical methods, namely, Regression coefficient (R²) and Root Mean Square Error (RMSE). This study has been carried out along 113.5 km of coast adjoining Bay of Bengal in eastern India, over the time interval 1973 to 2003. The study area has been subdivided into seven littoral cells, and transects at uniform interval have been chosen within each cell. The past and future shoreline positions have been estimated over two time periods of short and long terms in three modes, viz., transect-wise, littoral cell-wise and regionally.The result shows that 39% of transects have uncertainties in shoreline change rate estimations, which are usually nearer to cell boundaries. On the other hand, 69% of transects exhibit lower RMSE values for the short-term period, indicating better agreement between the estimated and satellite based shoreline positions. It is also found that cells dominated by natural processes have lower RMSE, when considered for long term period, while cells affected by anthropogenic interventions show better agreement for the short-term period. However, on regional considerations, there is not much difference in the RMSE values for the two periods. Geomorphological evidence corroborates the results. The present study demonstrates that combined use of satellite imagery and statistical methods can be a reliable method for shoreline related studies.     

Methane flux dynamics in relation to methanogenic and methanotrophic populations in the soil of Indian Sundarban mangroves

The dynamics of methane (CH₄) flux in relation to populations of methanogenic and methanotrophic bacteria was studied under the different biophysical conditions of the Indian Sundarban mangrove ecosystem. Soil depth profile analysis (up to 60 cm) in the lower littoral zone (LLZ) revealed that a methanogenic population of 6.45 ± 0.19 × 10⁴ cells/g dry weight (dry wt) of soil accounted for a CH₄ production rate of 6.23 ± 3.53 × 10³ µmol m^?2 day^?1, whereas in the surface soil, a methanogenic population of 3.34 ± 0.37 × 10⁴ cells/g dry wt of soil accounted for a CH₄ production rate of 31.6 ± 0.57 µmol m^?2 day^?1. The CH₄ oxidation rate at 60 cm depth in the LLZ was 24.42 ± 1.28 µmol m^?2 day^?1, with an average methanotrophic population of 1.33 ± 0.43 × 10⁴ cells/g dry wt of soil, whereas in the surface soil, the oxidation rate and average population were 3.38 ± 1.43 × 10³ µmol m^?2 day^?1 and 12.80 ± 2.54 × 10⁴ cells/g dry wt of soil, respectively. A similar soil profile in terms of CH₄ dynamics and the populations of methanogenic and methanotrophic bacteria was found in the mid‐littoral and upper littoral zones of the studied area. The results demonstrate that most of the produced CH₄ (approximately 60%) was oxidized by methanotrophic bacteria present in the soil, thus revealing their principal role in regulating the CH₄ flux from this unique ecosystem.