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Dynamics of arsenic species in the seabed sediments


Project Description

This project will be supervised by Professor Andy Meharg and Dr Caroline Meharg of Queen’s University School of Biological Sciences, Dr Adam Mellor of the Agri-Food and Biosciences Institute, and Dr Gareth Norton of the University of Aberdeen’s School of Biological Sciences. The start date will be 1 October 2019.

Arsenic has a complex global biogeochemical cycle, driven by inorganic arsenic mobilization from sediments and subsequent microbial methylation, with volatile arsines being the end product (Zhu et a., 2017). We have recently shown that oceans are a greatly neglected source of arsines to the atmosphere (Savage et al., 2018), but it is unclear whether these arsines are solely produced in the water-column, or from a combination of sources including sea-floor sediments. Both the water column and sediments have been identified as arsines sources in terrestrial and estuarine systems (Mestrot et al., 2011, Savage et al. 2018). This project will study the role of marine benthic sediments in arsenic cycling, using well characterised and accessible Irish Sea study sites. Utilizing AFBI’s established survey platforms to obtain sediments and benthic waters for experiments, this project will involve AFBI’s marine chemistry laboratory facilities, site knowledge and survey/sampling capacity. Determining the arsenic inputs via detrital sediment settling from the water column is of particular importance, given that marine biota (and thus their necromass) are elevated in arsenic, primarily in the forms of arsenobetaine and arsenosugars. Sediment traps will be deployed for capturing these. Sediments and surficial waters will be incubated to ascertain arsines efflux, and their microbiology investigated (using next-generation-sequencing approaches) to determine activity and diversity of arsenic methylating genes. Porewater and water-column arsenic speciation will be undertaken by ion chromatography ICP-MS. The microbial degradation of methylated arsenic species, arsenobetaine and arseno-sugars also needs considering as these will be present in necromass and may be important to arsenic cycling. Arsines trapping from water-column and sediments samples will involve the use of microcosms that will enable the manipulation of arsenic species and nutrients that arsenic is known to interact with (carbon, phosphorus, iron, sulphur, silica). Taken together, this will lead to a new and holistic understanding of arsenic behaviour on the seafloor and across the sediment/water interface. The studentship will develop a unique link between biogeochemistry and advanced molecular sequencing to explore arsenic dynamics in benthic habitats. The project will be centred at QUB where the chemistry, molecular microbiology and microcosm work will be conducted, with AFBI located nearby for marine logistics and marine chemistry. Aberdeen has the facilities and expertise in both sediment mineralogical and structural analysis, as well as facilities to conducted general chemical characterisation of sediments and water which will complement the techniques conducted at QUB.

References:

Mestrot A, Feldmann J, Krupp EM, Sumon MH, Roman-Ross G, Meharg AA (2011) Field fluxes and speciation of arsines emanating from soil. Environmental Science & Technology 45, 1798-1804.

Savage L, Carey M, Williams PN, Meharg AA (2018) Biovolatilization of arsenic as arsines from seawater. Environmental Science Technology 59, 3968-3974.

Zhu YG, Xue XM, Kappler A, Rosen B, Meharg AA (2017) Linking genes to biogeochemical cycling: lessons from arsenic Environmental Science Technology 51, 7326-7739.

Funding Notes

This studentship is available to UK and other EU nationals and provides funding for tuition fees and stipend, subject to eligibility.

Candidates should have (or expect to achieve) a minimum of a 2.1 Honours degree in a relevant subject.

References

Application Procedure:

(1) Apply for Degree of Doctor of Philosophy in Biological Sciences;
(2) State name of the lead supervisor as the name of proposed supervisor;
(3) State QUADRAT DTP as intended source of funding;
(4) State the exact project title on the application form.

How good is research at Queen’s University Belfast in Earth Systems and Environmental Sciences?

FTE Category A staff submitted: 24.40

Research output data provided by the Research Excellence Framework (REF)

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