Sedimentary carbon on the continental shelf : emerging capabilities and research priorities for Blue Carbon.

This work was supported by Cefas internal Seedcorn self-investment funding under the project DP440: Blue carbon within climate mitigation and ecosystem service approaches to natural asset assessments, and by Cefas’ Ecosystem Theme science theme.Continental shelf sediments store large amounts of organic carbon. Protecting this carbon from release back into the marine system and managing the marine environment to maximize its rate of accumulation could both play a role in mitigating against climate change. For these reasons, in the context of an expanding ‘Blue Carbon’ concept, research interest in the quantity and vulnerability of carbon stored in continental shelf, slope, and deep ocean sediments is increasing. In these systems, carbon storage is physically distant from carbon sources, altered between source and sink, and disturbed by anthropogenic activities. The methodological approaches needed to obtain the evidence to assess shelf sea sediment carbon manageability and vulnerability within an evolving blue carbon framework cannot be transferred directly from those applied in coastal vegetated ‘traditional’ blue carbon habitats. We present a ‘toolbox’ of methods which can be applied in marine sediments to provide the evidence needed to establish where and when marine carbon in offshore sediments can contribute to climate mitigation, focusing on continental shelf sediments. These methods are discussed in the context of the marine carbon cycle and how they provide evidence on: (i) stock: how much carbon is there and how is it distributed? (ii) accumulation: how rapidly is carbon being added or removed? and (iii) anthropogenic pressures: is carbon stock and/or accumulation vulnerable to manageable human activities? Our toolbox provides a starting point to inform choice of techniques for future studies alongside consideration of their specific research questions and available resources. Where possible a stepwise approach to analyses should be applied in which initial parameters are analysed to inform which samples, if any, will provide information of interest from more resource-intensive analyses. As studies increasingly address the knowledge gaps around continental shelf carbon stocks and accumulation – through both sampling and modelling – the management of this carbon with respect to human pressures will become the key question for understanding where it fits within the blue carbon framework and within the climate mitigation discourse.Publisher PDFPeer reviewe

Characterisation of radioactivity arising from the integrated steelworks in the UK and assessment of occupational exposure situations.

Most of the materials found on the Earth’s surface, such as iron ores and all other materials entering the integrated steel-making process, contain measurable amounts of natural radioactivity mainly due to the presence of uranium-238 (238U), thorium-232 (232Th) and their respective daughter decay products. Some materials after being processed can present a relatively high concentration of natural radionuclides. These materials are defined as Naturally Occurring Radioactive Materials (NORM). Since 2010, in the United Kingdom, industries producing NORM are subject to a new permitting regime. The current regime is named Environmental Permitting Regulations 2010 (EPR 2010), recently amended and replaced by EPR2016 and is directly derived from the European Directive EURATOM 1996, itself reviewed in 2013 and replaces the previous exemption limits defined in the previous regime Radioactive Substances Act 1993 (RSA93). As a result, the steel industry is now potentially producing materials above the new exemption levels to dispose of and therefore has a new environmental duty to accurately determine the radioactivity content of a wide range of iron- and steel-making materials used on site within the processes and/or sold off to third parties. In the steel industry, the main isotopes of concern are polonium-210 (210Po) and lead-210 (210Pb), which concentrate in the waste off-gas dusts from the iron ore sintering and blast furnaces processes, and radium-226 (226Ra) which can be found in slag materials from the blast furnace process. NORM can also result in potential exposure of the workforce to radioactive substances, mainly in workplaces where NORM are handled, stockpiled or processed. The UK steel industry has a duty of care to protect the workers and assess the potential occupational exposure to natural radioactivity in its workplaces in accordance with the Ionising Radiations Regulations 1999 (IRR99), recently replaced by IRR17 since 1st January 2018

Under-estimation of 210 Pb in industrial radioactive scales

Lead-210 (210Pb) can be present at high activity concentrations, in residues arising from the petroleum, mineral processing and chemical industries. Although 210Pb itself poses a low radiological risk, the nuclide decays via 210Bi to the alpha emitting and highly radiotoxic 210Po. Therefore, rapid, accurate determination of 210Pb is essential for assessing the radiological risk to plant operators and appropriate sentencing of waste. Unfortunately, direct measurement of 210Pb by gamma spectrometry is hindered by its weak gamma-ray emission at 46.5 keV, which is readily attenuated by mineral matrices. This paper demonstrates the extent to which 210Pb can be underestimated during routine analysis by an inter-laboratory exercise involving five accredited laboratories and a wide range of scales from diverse industrial sources. Two methods of addressing errors in 210Pb analysis are highlighted; the first, involving lithium tetraborate fusion prior to gamma spectrometry shows promise but is not suitable for all 210Pb-containing phases. The second method, requiring calculation of matrix attenuation factors for a representative fingerprint sample, was applied successfully to deposits from the steel and gas industries. However, its wider application depends on detailed chemical and mineralogical characterisation for each of the major categories of mineral scale found and at present, there is an acute lack of suitable certified reference materials

Determination of natural radioactivity in iron and steel materials

It has been known since the 1990s that two natural radioisotopes from the uranium-238 (238U) decay series, polonium-210 (210Po) and lead-210 (210Pb), originally present in trace amounts in raw materials, are volatilised and concentrate in the form of dusts during iron ore sintering. In the UK, most of the dust generated during this process is collected by means of electrostatic precipitators and recycled back into the production system using conveyor belts. Nevertheless, a small proportion passes into the atmosphere via stack emissions and some fugitive dusts can also escape into the workplace during maintenance operations. Tata Steel UK Ltd, a major European steel making company, has developed and validated in-house radioanalytical methods for the measurement of 210Po and 210Pb in a wide range of iron-making materials including raw feedstock, waste dusts, occupational and emission filter samples. The data gathered have enabled a better understanding of the fate of 210Po and 210Pb throughout the integrated steel making route, providing essential information to support environmental permits for discharges to the atmosphere and for confirming that chronic exposure to these two natural radioisotopes does not lead to significant radiological doses to the workforce. Additionally, since the implementation of the BSS Directive 2013/59 Euratom and the Construction Products Regulation (CPR), there is a need for the European steel industry to characterise the levels of radium-226 (226Ra), thorium-232 (232Th) and potassium-40 (40K) in slag materials and confirm that those materials do not pose a significant risk of internal and external exposure to radiation when reused or recycled in building materials. This paper highlights the technical challenges encountered when measuring those natural radioisotopes in various iron-making materials, including the difficulty of validating radioanalytical methods in the absence of suitable certified reference materials

Under-estimation of 210 Pb in industrial radioactive scales

Lead-210 (210Pb) can be present at high activity concentrations, in residues arising from the petroleum, mineral processing and chemical industries. Although 210Pb itself poses a low radiological risk, the nuclide decays via 210Bi to the alpha emitting and highly radiotoxic 210Po. Therefore, rapid, accurate determination of 210Pb is essential for assessing the radiological risk to plant operators and appropriate sentencing of waste. Unfortunately, direct measurement of 210Pb by gamma spectrometry is hindered by its weak gamma-ray emission at 46.5 keV, which is readily attenuated by mineral matrices. This paper demonstrates the extent to which 210Pb can be underestimated during routine analysis by an inter-laboratory exercise involving five accredited laboratories and a wide range of scales from diverse industrial sources. Two methods of addressing errors in 210Pb analysis are highlighted; the first, involving lithium tetraborate fusion prior to gamma spectrometry shows promise but is not suitable for all 210Pb-containing phases. The second method, requiring calculation of matrix attenuation factors for a representative fingerprint sample, was applied successfully to deposits from the steel and gas industries. However, its wider application depends on detailed chemical and mineralogical characterisation for each of the major categories of mineral scale found and at present, there is an acute lack of suitable certified reference materials

Production and characterisation of reference materials in support of naturally occurring radioactive material (NORM) industries

Naturally occurring radioactive material is a problematic by-product of a range of industries and needs to be handled, stored, processed and disposed of in a safe and economic manner. Accurate characterisation of such material should be underpinned by measurement of certified reference materials in order to validate the methods employed and ensure quality control. This work highlights the current shortage of suitable reference materials and the approach being followed to address this issue, initially for the steel and oil and gas industries

Sedimentary carbon on the continental shelf:emerging capabilities and research priorities for Blue Carbon

Continental shelf sediments store large amounts of organic carbon. Protecting this carbon from release back into the marine system and managing the marine environment to maximize its rate of accumulation could both play a role in mitigating against climate change. For these reasons, in the context of an expanding ‘Blue Carbon’ concept, research interest in the quantity and vulnerability of carbon stored in continental shelf, slope, and deep ocean sediments is increasing. In these systems, carbon storage is physically distant from carbon sources, altered between source and sink, and disturbed by anthropogenic activities. The methodological approaches needed to obtain the evidence to assess shelf sea sediment carbon manageability and vulnerability within an evolving blue carbon framework cannot be transferred directly from those applied in coastal vegetated ‘traditional’ blue carbon habitats.We present a ‘toolbox’ of methods which can be applied in marine sediments to provide the evidence needed to establish where and when marine carbon in offshore sediments can contribute to climate mitigation, focusing on continental shelf sediments. These methods are discussed in the context of the marine carbon cycle and how they provide evidence on: (i) stock: how much carbon is there and how is it distributed? (ii) accumulation: how rapidly is carbon being added or removed? and (iii) anthropogenic pressures: is carbon stock and/or accumulation vulnerable to manageable human activities? Our toolbox provides a starting point to inform choice of techniques for future studies alongside consideration of their specific research questions and available resources. Where possible a stepwise approach to analyses should be applied in which initial parameters are analysed to inform which samples, if any, will provide information of interest from more resource-intensive analyses. As studies increasingly address the knowledge gaps around continental shelf carbon stocks and accumulation – through both sampling and modelling – the management of this carbon with respect to human pressures will become the key question for understanding where it fits within the blue carbon framework and within the climate mitigation discourse