Spatial and seasonal variability of sediment accumulation potential through controlled flooding of the beels located in the polders of the Ganges-Brahmaputra-Meghna delta of Southwest Bangladesh

The Ganges-Brahmaputra-Meghna (GBM) delta plain within Bangladesh is one of the most vulnerable to relative sea level rise (RSLR) in the world especially under current anthropogenically modified (i.e., embanked) conditions. Tidal river management (TRM) as practiced in coastal regions of Bangladesh may provide an opportunity to combat RSLR by raising the land level through controlled sedimentation inside beels (depression within embanked polders) with re-opening of polders. To date, TRM has been applied to tide-dominated coastal regions, but the potential applicability of TRM for the beels within the polders of river-dominated and mixed flow (MF) regimes remains to be assessed. We apply a calibrated 2D numerical hydromorphodynamic model to quantify sediment deposition in a beel flooded through breaching of the polder dike under conditions of river-dominated, tide-dominated and MF regimes for different seasons and applying different regulation schemes for the flow into the beel. Simulation results show considerable seasonality in sediment deposition with largest deposition during the monsoon season. The potential of controlled flooding is highest in the tide-dominated region, where sediment accumulation can be up to 28 times higher than in the river-dominated region. Regulating flow into a beel increases trapping efficiency, but results in slightly lower total deposition than without regulation. We conclude that re-establishing flooding of the beel within the polder without regulating the flow into the beel through breaching of the polder dike is a promising strategy for the mixed and tide-dominated flow regions in the delta as the sediment accumulation can raise the land surface at a higher rate than RSLR and effective SLR (ESLR). In the more upstream river-dominated section of the delta, accumulation rates would be much lower, but the pressure of sea level rise on these areas is lower as well. Owing to the abundant availability of sediment, application of controlled flooding like TRM therefore provides an opportunity to counteract the impact of RSLR and ESLR by means of land raising, particularly along the tidal river reaches in the GBM delta.     

Assessment of health safety from ingestion of natural radionuclides in seafoods from a tropical coast, India

The activities of ²¹⁰Po and ²¹⁰Pb were determined in commonly consumed seafoods to evaluate the internal exposure and risk to humans residing Kudankulam coast where a mega nuclear power plant is under construction. The concentration of ²¹⁰Po in seafoods ranged from 1.2 ± 0.7 to 248 ± 8.1 Bq kg⁻¹. Meanwhile, ²¹⁰Pb ranged between 1.1 ± 0.05 and 14.8 ± 1.6 Bq kg⁻¹. The committed effective dose (CED) due to ²¹⁰Po and ²¹⁰Pb varied from 11.04 to 515.6 and 3.93 to 23.5 μSv yr⁻¹, respectively. The lifetime cancer risk for the public due to ²¹⁰Po was in the range of 3.47 × 10⁻⁵-1.62 × 10⁻³ and it was 4.03 × 10⁻⁵-1.96 × 10⁻⁴ due to ²¹⁰Pb. The activity intake, effective dose and cancer risk was found lesser than international guidelines and the seafood intake was considered to be safe for human consumption.     

Description of the small plastics fragments in marine sediments along the Alang-Sosiya ship-breaking yard, India

This study aimed to assess the accumulation of small plastic debris in the intertidal sediments of the world's largest ship-breaking yard at Alang-Sosiya, India. Small plastics fragments were collected by flotation and separated according to their basic polymer type under a microscope, and subsequently identified by FT-IR spectroscopy as polyurethane, nylon, polystyrene, polyester and glass wool. The morphology of these materials was also studied using a scanning electron microscope. Overall, there were on average 81 mg of small plastics fragments per kg of sediment. The described plastic fragments are believed to have resulted directly from the ship-breaking activities at the site.     

Statistical parameters of Bhuj earthquake sequence of January 26th, 2001

An intraplate earthquake of magnitude (M _c) 6.9 (Anon 2001a) struck Bhuj and the adjoining region of Kachchh in Gujarat on January 26th, 2001 at about 0316 hrs (GMT) and was followed by a number of aftershocks. The epicentre of this earthquake was located at 23.4‡N and 70.28‡E close to the Kachchh mainland fault. The intensity observed around the epicenter was X on the MSK scale. A study of 531 aftershocks, in the magnitude range of 3.0–5.7, recorded at Vadodara Seismological Observatory till March 31st, 2001 has been carried out and various statistical parameters calculated. The total energy released during the study period is calculated to be 8.2 × 10¹⁴ joule. Sudden occurrence of the main shock without any foreshock in the same tectonic system is a unique feature of this sequence. Theb- value (0.86), value of M₀-M₁ (1.2), high M₁/M₀ (0.89) and high value of the decay constanth (0.91), all support the tectonic origin of the present study.     

Vibration analysis of damaged and undamaged steel structure systems: cantilever column and frame

This paper presents the experimental and numerical studies conducted on a steel column and a steel frame structure using free vibration analysis. The effects of damages on structures were investigated, which were simulated by introducing multiple cracks at different locations in the experimental and numerical models. The acceleration responses of the test models, were recorded through an accelerometer, and were used to calibrate the numerical models developed in finite element based software. Modal frequencies of damaged and undamaged structures were compared and analyzed, to derive relationships for damaged and undamaged structures' frequencies in terms of crack depth. It was found that, due to the presence of cracks, the mechanical properties of a structure changes, whereby, the modal frequencies decrease. An approximately linear trend was observed for the frequency decrease with the increase in crack depth, which was also confirmed by the numerical models. The derived relationships were extended to further develop a mechanics-based damage scale for steel structures, to help facilitate structural health monitoring and screening of vulnerable structures.     

Climate‐induced Late‐Holocene ecological changes in Pichavaram estuary,India

Variation in sedimentology as well as freshwater and marine palynomorphs has been studied in ecological perspective in two 2.5‐ and 5‐m deep sediment cores deposited since 3440 and 3630 cal BP, respectively in the central part of Pichavaram mangrove wetland, Cauvery River delta. The palynological and sedimentological results of the sediments reveal a monsoonal circulation and a climatic shift from warm and humid with strengthened monsoon (3630–3190 cal BP) to dry and arid (~2750–760 cal BP). Since the last millennium (~760 cal BP), Pichavaram estuary has been influenced by a similar cyclicity but with a less wet and humid climate due to weakened monsoon conditions. These ecological changes in turn affect the relative sea level rise and fall which is reflected by the variability/extinction of freshwater and marine palynomorphs. The estuary remained an active water channel between ~3630 and 2750 cal BP, responding to the strengthened monsoon, during which the freshwater algal remains with thecamoebians and marine dinoflagellate cysts and foraminiferal linings both dominated with a ratio of 1.5 for marine/freshwater forms. After this period, since ~2750 cal BP there has been a dominance of marine forms with a ratio of 4.5 for marine/freshwater forms, indicating fluvio‐marine sediment deposition and suggesting the recent landward intrusion of seawater during weakened monsoon conditions. Freshwater thecamoebians are vulnerable to the salinity >3 in the aqueous soil solution of estuarine sediment, and therefore serve as an excellent proxy for monitoring salinity gradient along with short‐term high resolution palaeoecological fluctuations induced by climate and relative sea‐level changes in an estuarine ecosystem.     

Distribution, enrichment and accumulation of heavy metals in coastal sediments of Alang-Sosiya ship scrapping yard, India

Since its inception in 1982, the Alang-Sosiya yard has become the largest ship scrapping works in the world. Several hundreds of ships arrive every year. The degree of heavy metal contamination has been studied in bulk and fine sediments from the intertidal zone of this ship scrapping yard, two stations, one on either side at 5 km distance and one reference station 60 km distance near Mahuva, towards the south. The samples have been subjected to a total digestion technique and analysed for elements: Cd, Co, Cu, Cr, Fe, Mn, Ni, Pb, Zn and Al, and %TOC. The absolute metal concentrations reflected variations in BF and FF sediment samples with organic matter content. Enrichment factors (EF) and geoaccumulation indices (Igeo) have been calculated and the relative contamination levels are assessed at these sites. At Alang-Sosiya, the enrichment of heavy metals has been observed to be relatively high.     

Use of Remote Sensing and Geospatial Technique for Pre-feasibility Analysis of Rural Water Pipeline Grids

The article outlines a procedure of pre-feasibility analysis of planned rural water supply pipeline grids in India. Usually, these type of pre feasibility studies prior to actual implementation, is carried out based on ground surveys and is time consuming. In this work, we use thematic spatial data, such as geomorphology and landuse–landcover along with digital elevation model (DEM) to carry out the pre-feasibility assessment of proposed pipeline grids. DEM generated from CartoSat-1 stereo data has been used to understand the possible topographic hindrances along the planned pipeline route and optimise the same. Further, topographic data also indicates the possible routes of gravity assisted flow. The geomorphology thematic data interpreted from Resourcesat-1 LISS III imagery is used to identify possible geomorphologic hindrances along the pipeline route. Similarly, landuse–landcover information derived from Resourcesat-2 LISS III images, was used to assess the land use/cover impact of the planed pipeline corridor. This has been demonstrated, in the current article using a hypothetical pipeline route. The activity can be carried in a specially designed geo-spatial interface in NRSC/ISRO Bhuvan geoportal. This type of assessment can prove to be time saving and cost effective at a pre-feasibility stage.     

Treatment options for wastewater effluents from pharmaceutical companies

In recent years, concerns about the occurrence and fate of active pharmaceutical ingredients, solvents, intermediates and raw materials that could be present in water and wastewater including pharmaceutical industry wastewater has gained increasing attention. Traditional wastewater treatment methods, such as activated sludge, are not sufficient for the complete removal of active pharmaceutical ingredients and other wastewater constituents from these waters. As a result, complementary treatment methods such as membrane filtration, reverse osmosis and activated carbon are often used in conjunction with the traditional methods for treatment of industrial wastewater. Most of the literature published to date has been on the treatment of municipal wastewater. However, there is a growing body of research that looks at the presence of active pharmaceutical ingredients in industrial wastewater, the treatment of these wastewaters and the removal rates. This article, reviews these treatment methods and includes both traditional methods and advanced oxidation processes. The paper concludes by showing that the problem of pharmaceuticals in wastewaters cannot be solved merely by adopting end of pipe measures. At source measures, such as replacement of critical chemicals, reduction in raw material consumption should continue to be pursued as the top priority.