8 results on '"Manamsa, K."'
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2. A baseline survey of dissolved methane in aquifers in Great Britain
- Author
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Bell, R.A., Darling, W.G., Ward, R.S., Basava-Reddi, L., Halwa, L., Manamsa, K., O Dochartaigh, B.E., Bell, R.A., Darling, W.G., Ward, R.S., Basava-Reddi, L., Halwa, L., Manamsa, K., and O Dochartaigh, B.E.
- Abstract
Interest in dissolved methane (CH4) concentrations in aquifers in England, Scotland and Wales (‘Great Britain’ or GB) has grown concurrently with interest in the exploitation of unconventional gas sources (UGS). Experience, mainly from North America, has shown the importance of a pre-production baseline against which changes possibly due to UGS extraction can be compared. The British Geological Survey, aided by water utilities, private users and regulators, has compiled a unique dataset for CH4 in groundwaters of GB. This focuses principally on areas where UGS exploration is considered more likely, as indicated by the underlying geology. All the main water supply aquifers (Principal aquifers) were targeted, plus Secondary aquifers where locally important. The average dissolved CH4 concentration across GB in the aquifers sampled was 45 μg/l. Out of a total of 343 sites, 96% showed dissolved CH4 concentrations b100 μg/l, 80% b10 μg/l, and 43% b 1 μg/l. No site had a CH4 concentration above the US Department of the Interior suggested risk action level of 10,000 μg/l. While most sites were sampled only once, a sub set was monitored quarterly to determine the magnitude of seasonal or other variations. Generally these variations were minor, with 84% of sites showing variations within the range 0.5–37 μg/l, but some aquifers where the porosity was primarily fracture-related showed larger changes (0.5–264 μg/l). This may have been due to the nature of sampling at these sites which, unlike the others, did not have installed pumps. Since the regulatory compliance monitoring attending UGS operations will include the measurement of parameters such as dissolved CH4, it is essential that sampling methods are tested to ensure that reliable and comparable datasets can be obtained.
- Published
- 2017
3. The baseline concentrations of methane in Great British groundwater : the National Methane Baseline Survey
- Author
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Bell, R.A., Darling, W.G., Manamsa, K., and O Dochartaigh, B.E.O.
- Abstract
This report describes the BGS research programme evaluating the baseline concentration of methane in groundwater which ran from November 2011 to completion in March 2016. The aim of the survey has been to improve knowledge of conditions in aquifers overlying potential shale gas source rocks present at depth, thus providing baseline knowledge relevant to the management of future exploration of new hydrocarbon sources. The necessity for doing this has been prompted by evidence from elsewhere (notably the USA) which has revealed very high methane concentrations in groundwater in some areas of shale gas extraction. Although this has often been directly attributed to shale gas operations, there have generally been no pre-development data on methane concentrations available to test this. Before the start of the current survey, BGS held some 170 analyses of methane in groundwaters from aquifers across Great Britain, acquired from the 1980s onwards. These data have been combined with new survey data, to give a total of 439 methane data points. In this combined dataset, 96% of samples show methane concentrations of less than 100µg/l and indicate that methane is rarely present at concentrations high enough to be potentially explosive (there are no health limits for methane in groundwaters). In the minority of samples with elevated concentrations, this was generally considered to be due to the proximity of organic rich coal seams or peats. The highest concentrations were found in the Cretaceous aquifers of the Weald Basin, a known area for occurrences of methane gas in the shallow subsurface. The new survey covers the majority of principal aquifers in Great Britain, including the Chalk, Permo-Triassic Sandstones, Carboniferous Limestone, and the Lower Greensand. Samples from over twenty different aquifers have been collected. In general, methane concentrations in carbonate aquifers (Chalk, limestones, Oolites etc.) are low, similar to those seen in the Permo-Triassic sandstone aquifers, although methane is widely present above detection limit (approximately 1µg/L) in all these aquifers. The Coal Measures of South Wales have the highest median value across Great Britain and this aquifer also shows the greatest temporal variability. Methane concentrations in the Carboniferous sediments of Scotland are also elevated, likely due to the impact of mining and the presence of coal seams. While little temporal variability is generally seen in aquifers used for public water supply or otherwise regularly pumped, further work is required to understand the impact of borehole use, pumping regime and aquifer type on the variability of the methane baseline of Great British aquifers. It should be noted that the Survey is not intended to replace any oil and gas operator’s local monitoring as required by the regulators. This is a national scale survey to enable a broad understanding of the distribution of methane in aquifers across relevant areas of Britain and cannot replace an understanding of groundwater quality at a local scale.
- Published
- 2016
4. Temporal variability of micro-organic contaminants in lowland chalk catchments: new insights into contaminant sources and hydrological processes
- Author
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Manamsa, K., Lapworth, D.J., Stuart, M.E., Manamsa, K., Lapworth, D.J., and Stuart, M.E.
- Abstract
This paper explores the temporal variation of a broad suite of micro organic (MO) compounds within hydrologically linked compartments of a lowland Chalk catchment, the most important drinking water aquifer in the UK. It presents an assessment of results from relatively high frequency monitoring at a well-characterised site, including the type and concentrations of compounds detected and how they change under different hydrological conditions including exceptionally high groundwater levels and river flow conditions during 2014 and subsequent recovery. This study shows for the first time that within the Chalk groundwater there can be a greater diversity of the MOs compared to surface waters. Within the Chalk 26 different compounds were detected over the duration of the study compared to 17 in the surface water. Plasticisers (0.06–39 μg/L) were found to dominate in the Chalk groundwater on 5 visits (38.4%) accounting for 14.5% of detections but contributing highest concentrations whilst other compounds dominated in the surface water. Trichloroethene and atrazine were among the most frequently detected compounds. The limit for the total pesticide concentration detected did not exceed EU/UK prescribed concentration values for drinking water. Emerging organic compounds such as caffeine, which currently do not have water quality limits, were also detected. The low numbers of compounds found within the hyporheic zone highlight the role of this transient interface in the attenuation and breakdown of the MOs, and provision of an important ecosystem service.
- Published
- 2016
5. Temporal variability of micro-organic contaminants in lowland chalk catchments: New insights into contaminant sources and hydrological processes
- Author
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Manamsa, K., primary, Lapworth, D.J., additional, and Stuart, M.E., additional
- Published
- 2016
- Full Text
- View/download PDF
6. Persistent and emerging micro-organic contaminants in Chalk groundwater of England and France
- Author
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Lapworth, D.J., Baran, N., Stuart, M.E., Manamsa, K., Talbot, J., Lapworth, D.J., Baran, N., Stuart, M.E., Manamsa, K., and Talbot, J.
- Abstract
The Chalk aquifer of Northern Europe is an internationally important source of drinking water and sustains baseflow for surface water ecosystems. The areal distribution of microorganic (MO) contaminants, particularly non-regulated emerging MOs, in this aquifer is poorly understood. This study presents results from a reconnaissance survey of MOs in Chalk groundwater, including pharmaceuticals, personal care products and pesticides and their transformation products, conducted across the major Chalk aquifers of England and France. Data from a total of 345 sites collected during 2011 were included in this study to provide a representative baseline assessment of MO occurrence in groundwater. A suite of 42 MOs were analysed for at each site including industrial compounds (n = 16), pesticides (n = 14) and pharmaceuticals, personal care and lifestyle products (n = 12). Occurrence data is evaluated in relation to land use, aquifer exposure, well depth and depth to groundwater to provide an understanding of vulnerable groundwater settings.
- Published
- 2015
7. Persistent and emerging micro-organic contaminants in Chalk groundwater of England and France
- Author
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Lapworth, D.J., primary, Baran, N., additional, Stuart, M.E., additional, Manamsa, K., additional, and Talbot, J., additional
- Published
- 2015
- Full Text
- View/download PDF
8. A national-scale assessment of micro-organic contaminants in groundwater of England and Wales.
- Author
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Manamsa K, Crane E, Stuart M, Talbot J, Lapworth D, and Hart A
- Subjects
- England, Environmental Policy legislation & jurisprudence, Government Regulation, Groundwater standards, Wales, Water Quality, Environmental Monitoring methods, Groundwater chemistry, Organic Chemicals analysis, Water Pollutants, Chemical analysis
- Abstract
A large variety of micro-organic (MO) compounds is used in huge quantities for a range of purposes (e.g. manufacturing, food production, healthcare) and is now being frequently detected in the aquatic environment. Interest in the occurrence of MO contaminants in the terrestrial and aquatic environments continues to grow, as well as in their environmental fate and potential toxicity. However, the contamination of groundwater resources by MOs has a limited evidence base compared to other freshwater resources. Of particular concern are newly 'emerging contaminants' such as pharmaceuticals and lifestyle compounds, particularly those with potential endocrine disrupting properties. While groundwater often has a high degree of protection from pollution due to physical, chemical and biological attenuation processes in the subsurface compared to surface aquatic environments, trace concentrations of a large range of compounds are still detected in groundwater and in some cases may persist for decades due to the long residence times of groundwater systems. This study provides the first national-scale assessment of micro-organic compounds in groundwater in England and Wales. A large set of monitoring data was analysed to determine the relative occurrence and detected concentrations of different groups of compounds and to determine relationships with land-use, aquifer type and groundwater vulnerability. MOs detected including emerging compounds such as caffeine, DEET, bisphenol A, anti-microbial agents and pharmaceuticals as well as a range of legacy contaminants including chlorinated solvents and THMs, petroleum hydrocarbons, pesticides and other industrial compounds. There are clear differences in MOs between land-use types, particularly for urban-industrial and natural land-use. Temporal trends of MO occurrence are assessed but establishing long-term trends is not yet possible., (Copyright © 2016 British Geological Survey, NERC. Published by Elsevier B.V. All rights reserved.)
- Published
- 2016
- Full Text
- View/download PDF
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