Understanding Arsenic removal processes: passive treatment systems as proxies for natural environments

Biogeochemical Cycles

IAP2-19-147

Overview

Groundwater in many regions of the world, including parts of the UK, contains high Arsenic (As) concentrations. The use of this water as main source of drinking water in many South and Southeast Asian countries has led to what was termed the ‘largest mass poisoning’ [1]. Although mitigation strategies have been developed and implemented, still a vast number of people, mostly rural and poor, are consuming the contaminated water and experiencing the adverse health effects today [2].

In contrast to the attention that As-contaminated drinking water has received over the past decades, the use of this As-containing water for irrigation purposes has been less extensively studied. Still, these studies demonstrated uptake of As from irrigation water into the staple crop rice, but also into other plant-based foodstuff [3]. This situation may worsen in coming years as climate change may lead to increasing water stress and thus increasing irrigation around the world. Removing As from large quantities of irrigation water via treatment or natural attenuation processes is a currently unsolved challenge and, in contrast to As removal from drinking water, has not received much attention.

We recently found that As removal occurred in a compost-based passive treatment system for mine-water, which may be a potential low-cost and zero-energy treatment for As-contaminated irrigation water. However, the process(es) leading to this unexpected removal are currently unclear but may be relevant to other passive treatment systems (e.g. sand or zero-valent iron-based filters), and/or occur in natural environments such as soils. This project will investigate the fundamental processes of As removal in these passive treatment systems, as case studies for natural attenuation processes. To address the challenge of managing As-contaminated irrigation water, the project will address the specific questions:
(1) Which biotic or abiotic processes (or both) are removing As in the treatment systems?
(2) How is the removed As bound and what are the consequences for its future release (e.g., due to changes in biogeochemical parameters, waste management practices)?
(3) Can we manage these processes in natural environments, particularly soils, to attenuate As contamination and bioavailability?

Methodology

The student will be based in the School of Engineering at Newcastle University (supervised by A. Neumann and A. Jarvis), with visits to the University of Glasgow to learn and apply molecular biology tools (supervised by C. Smith). The project will involve fieldwork at the Force Crag treatment system, which is a 2.5-hour drive from Newcastle. Sampling will include both treatment system water and solid samples, with subsequent detailed analysis of both undertaken at Newcastle and Glasgow Universities for abiotic and biotic parameters.

Activities at Force Crag will be supplemented with laboratory-based batch and column experiments to investigate, in more detail, the As removal processes under carefully-controlled lab conditions and to compare them to those that occur at larger scale under ambient environmental conditions. For comparison, two other removal approaches, i.e. sand and zero-valent iron-based filters, will be emulated in the laboratory and, if interesting results are obtained, also run with real contaminated water at the field site at Force Crag.

To address question 1, real-time water quality measurements will be carried out in both field and laboratory. Aqueous samples obtained will be analysed with ICP-OES and ICP-MS analysis for metal(oid) concentrations as well as the microbial community present and active. In addition to total As concentrations, specialised columns will be used in conjunction with IC to determine As speciation in the different treatment systems. Solid samples will be retrieved and subjected to a sequential extraction procedure [4] to investigate the mobility and potential for the re-release of As (question 2). Additional solid phase analyses will include XRD to determine the overall mineral composition and, if required, Mössbauer spectroscopy to determine and monitor solid iron phase composition and transformation. To translate the findings from questions 1 and 2 to natural sedimentary environments (question 3), a qualitative and, if possible, quantitative model will be developed, describing the different treatment systems studied as proxies for natural environments. Geochemical and microbial parameters will be analysed for the importance in each system and across systems, to derive master variables for assessment in the field.

Project Timeline

Year 1

Detailed literature review; training in laboratory and field techniques as well as molecular microbial tools; commencement of measurements and experiments pertaining to question 1.

Year 2

Continuation with and conclusion of experiments related to question 1; commencement of work related to question 2; preparation of 1st journal article and conference presentation towards end of year.

Year 3

Completion of experiments related to question 2; development of qualitative/quantitative model(s); laboratory and modelling work to be concluded by end of third quarter; writing up of thesis and preparation of journal article(s).

Year 3.5

Completing writing up of thesis and preparation of journal article(s).

Training
& Skills

The student will be trained in all laboratory skills, analytical techniques, and all aspects of fieldwork as required for the project. Training in all aspects of laboratory work, from planning over implementing to critically assessing, will be provided at Newcastle University. Here, the student will also become familiar with the routine analysis methods for inorganic compounds (ICP-OES, ICP-MS, IC) as well as for As speciation (IC, sequential extraction) and be trained in solid phase characterisation (XRD, Mössbauer spectroscopy). Similarly, the student will receive training at the University of Glasgow in state-of-the-art molecular biology tools and techniques.

Further training needs will be assessed during the first three months of the PhD, involving the PhD student and the entire supervisory team, and a detailed training plan will be developed. This training plan might also include relevant taught MSc modules at Newcastle University or the University of Glasgow. Furthermore, the PhD student will be encouraged to make use of the broad suite of training opportunities in transferable skills provided at Newcastle University. The supervisory team will build on these skills trainings and consolidate and deepen the student’s critical analysis and writing skills, their proficiency in preparing manuscripts for publication in peer-reviewed journals, and their competency at delivering conference presentations.

References & further reading

[1] https://www.who.int/features/archives/feature206/en/[2] Ahmed, M. F.; Ahuja, S.; Alauddin, M.; Hug, S. J.; Lloyd, J. R.; Pfaff, A.; Pichler, T.; Saltikov, C.; Stute, M.; van Geen, A., Epidemiology – Ensuring safe drinking water in Bangladesh. Science 2006, 314, 1687-1688.[3] Dittmar, J.; Voegelin, A.; Maurer, F.; Roberts, L. C.; Hug, S. J.; Saha, G. C.; Ali, M. A.; Badruzzaman, A. B. M.; Kretzschmar, R., Arsenic in Soil and Irrigation Water Affects Arsenic Uptake by Rice: Complementary Insights from Field and Pot Studies. Environ Sci Technol 2010, 44 (23), 8842-8848.[4] Huhmann, B.; Neumann, A.; Boyanov, M. I.; Kemner, K. M.; Scherer, M. M., Emerging investigator series: As(v) in magnetite: incorporation and redistribution. Environ Sci Process Impacts 2017, 19 (10), 1208-1219.

Further Information

For more information, please contact Dr Anke Neumann (anke.neumann@ncl.ac.uk).

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