PhD Topics in Environmental Geochemistry at Imperial College London
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Zinc isotopes to unravel plant uptake mechanisms [details]
Copper isotopes and Parkinson disease [details]
Zn isotopes as tracers of diffuse pollution [details]
The ocean chemistry of Pb [details]
The global geochemical cycle of Zn and Cu [details]
Dust fertilisation of the remote ocean [details]
Global extent of atmospheric toxic element pollution [details]
The controls of the Asian Monsoon on the global dust cycle [details]
The adsorption mechanisms of Sb, U and As on minerals
New sorbents for As removal from water [details]
For any inquiries, plse do contact d.weiss[at]imperial.ac.uk
1.
Zn isotopes to unravel plant uptake mechanisms
Zn deficiency in rice affects the nutrition of a large population in Asia. Some rice strains are more
effective than others in taking up Zn from the soil but the mechanisms are little understood – with
uptake or translocations within the rice being potential places where the Zn chemistry in the rice may
be different.
Changes in the bioinorganic chemistry of Zn can be detected using its isotopes and previous work of
our group lead to a fractionation model of Zn in the rice-soil environment (Arnold et al., submitted).
This model we want to test and thus develop a new way to probe plant physiological processes. To do
so we aim to conduct (i) experiments with different rice genotypes, (ii) to conduct speciation
experiments and look at complexes vs. free Zn and (iii) to conduct ab-initio theoretical calculations
using quantum mechanical models.
Arnold, T., Kirk, G. J. D., Wissuwa, M., Frei, M., Zhao, F. J., and Weiss, D. J., in press. Evidence for
the mechanisms of zinc efficiency in rice using isotope discrimination. Plant Cell Environ.
von Blanckenburg, F., Von Wiren, N., Guelke, M., Weiss, D. J., and Bullen, T. D., in press. Metal stable
isotope fractionation by higher plants. Elements.
2.
Copper isotopes and Parkinson disease
Parkinson disease is associated with malfunctions in the Cu metabolism, i.e. changes in its bioinorganic
chemistry in our body.
In this project we aim to explore the application of Cu isotopes to trace changes in the bioinorganic
chemistry of Cu in PD subjects. We will conduct laboratory experiments looking at the isotopic
fractionation during complex formation of Cu with the main organic ligands in the body, i.e., proteins.
We will furthermore look at isotopic variability in the various compartments of the subject and derive
biochemical reaction pathways from this. Ultimately, we hope that the Cu isotopes can act as screening
tool for Parkinson diseases in humans.
3.
Zink isotopes as tracers of diffuse pollution in the atmosphere
Zink is a serious health hazard in the environment. In the air, its toxicity stems from the entrance into
the pulmonary system and damages it does in the alveoli. The main problem with Zn air pollution,
however, is that we know little about where it comes from in the atmosphere. The pollution sources
are diffuse.
Previous work of our research group showed that significant isotopic variations exists in urban
aerosols, and we suggest that this is because Zn derived from non-exhaust traffic sources (i.e. brakes
and tyres) and from combustion (traffic, non traffic) is distinct different. These ideas we want to test
by (i) conducting a systematic study of isotopic variability in exhaust and non-exhaust related products
in the urban environment, (ii) conducting well constrained combustion and smelting experiments and
(iii) investigating the Zn isotopic dynamics in aerosols in traffic and non-traffic dominated places. This
project includes field and experimental work.
Gioia, S., Weiss, D. J., Coles, B. J., Arnold, T., and Babinski, M., 2008. Accurate and precise
measurements of Zn isotopes in aerosols. Anal. Chem. 80, 9776-9780.
Weiss, D., Mason, T. F. D., Rausch, N., Arnold, T., Coles, B. J., Nieminen, T. M., Ukonmaanaho, L.,
and Wilkinson, J. J., 2007. Atmospheric deposition and isotope biogeochemistry of zinc in
ombrotrophic peat. Geochim. Cosmochim. Acta 71, 3498-3517.
4.
The ocean chemistry of lead
Lead is a key tracer in the ocean for two very good reasons: First, Pb in surface waters allows us to
monitor the effect of global air pollution and second, we can use this transient tracer to trace ocean
circulation in the past as well as in the future. The geochemistry of Pb in the ocean, however, is very
little understood partly due to the little information we do have on its isotopic composition at various
places in the ocean, on time evolution patterns etc.
We are a part of the GEOTRACES consortium that aims to study the marine chemistry of
micronutrients and key tracers in the ocean, including Pb, Nd, Cd and Hf isotopes. We aim now to
investigate the spatial distribution of Pb in the Southern Ocean surface waters. We will assess depth
profiles and identify the dominant sources and put these findings in the context of ocean circulation
models and global air pollution. Furthermore we will conduct laboratory experiments investigating
solubility of aerosols (man made and natural) and Pb scavenging on marine particles.
Weiss, D., Chavagnac, V., Boyle, E. A., Wu, J. F., and Herwegh, M., 2000. Determination of lead
isotope ratios in seawater by quadrupole inductively coupled plasma mass spectrometry after Mg(OH)2
co-precipitation. Spectrochim. Acta, B 5, 363-374.
Weiss, D. J., Boyle, E. A., Chavagnac, V., Wu, J., Michel, A., and Reuer, M., 2003. Lead isotope
evolution of the North Atlantic: pattern of deposition and source assessment. J. Geophys. Res. 108, 3306
doi:10.1029/2000JC000762.
5.
The global biogeochemical cycle of Zn and Cu
The importance of Cu and Zn for the functioning of the earth system cannot be overstated – it drives
the microorganism cycle in remote areas of the ocean and it is a key nutrient element for plants an
animals. Nevertheless – their global biogeochemical cycles have not been quantified and this limits its
incorporation into climate models.
We aim here to develop Cu and Zn isotopes as tools to constrain these cycle and to develop – based of
isotope and flux data – a global biogeochemical Zn and Cu model incorporating atmosphere, oceans,
and continent.
Weiss, D. J., Rehkämper, M., Schoenberg, R., McLaughlin, M., Kirby, J., Campbell, P. G. M., Arnold,
T., Chapman, J., Peel, K., and Gioia, S., 2008. Application of nontraditional stable-isotope systems to
the study of sources and fate of metals in the environment. Environ. Sci. Technol. 42, 655 - 664.
6.
Dust fertilisation of the remote ocean
Fertilisation of the ocean via dust deposition has been suggested as a major factor driving the oceanic
carbon cycle. However, there are modelling evidences that it might be less of an importance. This
controversy is partly based on our poor understanding of atmospheric dust deposition to the ocean.
We want to investigate this problem via different pathways, including (i) the use of high resolution
atmospheric archives in HPLC areas to determine micronutrient fluxes during the Holocene and
compare that with productivity/CO2 records to test for synchronicity, (ii) to investigate the dissolution
of various dust types in seawater, and (iii) to investigate the role that atmospheric pollution plays in the
fertilization of the ocean.
Weiss, D., Shotyk, W., Page, S. E., Rieley, J. O., Reese, S., and Martinez-Cortizas, A., 2002. The
geochemistry of major and selected trace elements in a forested peat bog, Kalimantan, SE-Asia, and its
implications on past atmospheric dust deposition. Geochim. Cosmochim. Acta 66, 2307-2323.
7.
Global extent of atmospheric pollution of toxic trace metals
Atmospheric pollution is threatening human and ecosystem health on a global scale. New global
significant pollution centres such as India, China and Brazil have emerged as well as new sources - with
coal being by now one of the major pollution sources.
There is an urgent need to assess this new pollution environment and we aim to address this by (i)
studying the historical development of pollution in the three major regions, (ii) quantifying pollutant
concentrations in aerosols collected in remote areas of the globe under the atmospheric influence of
these centres, and (iii) characterising concentration and isotope data (U, Pb, Hg, Cu and Zn) in the
major coal deposits to improve source tracing.
Diaz Somoano, M., Kylander, M. E., Martínez-Tarazona, M. R., Suarez-Ruiz, I., López Antón, M.,
Kober, B., Ferrat, M., and Weiss, D. J., 2009. Stable lead isotope compositions in selected coals from
around the world and implications for present day aerosol source tracing. Environ. Sci. Technol. 43, 10781085.
Kylander, M., Weiss, D. J., and Kober, B., 2009. Two high-resolution terrestrial records of atmospheric
Pb deposition from New Brunswick, Canada, and Loch Laxford, Scotland. Sci. Total Environ. 407, 16441657.
8.
The controls of the Monsoon system on the global dust cycle
Dust is of major importance to the functioning of the Earth System via a remarkable variety of effects
(ocean fertilization, albedo, etc). A full understanding of its cycle, its drivers and its effects on global
biogeochemical cycles will allows us to develop and improve future climate models. China is a key
region for global dust generation due to its large deserts. Production and emission of the dust from the
regions is dominated by the Monsoon system and the changing regime of dry and wet weather.
Our aim is to study the past interaction between monsoon and dust cycling in Central Asia and based
on this to develop a regional climate model, which then can be incorporated in a global biogeochemical
model. This is achieved using peat cores as archives of past atmospheric dust fluxes and the regional
climate model REMOTE.
Muller, J., Kylander, M. E., Wüst, R. A. J., Weiss, D. J., Martinez-Cortizas, A., LeGrande, B.,
Jennerjahn, T., Behling, H., Anderson, W. T., and Jacobson, G., 2008. Possible evidence for wet
Heinrich phases in tropical NE Australia: The Lynch's Crater deposit. Quaternary Sci. Rev 27, 468-475.
Large, D., Spiro, B., Shopland, M., Ferrat, M., Kylander, M., Li, X., Chengde, S., Possnert, G., and
Weiss, D. J., in press. The influence of climate, hydrology and permafrost on the Eastern QinghaiTibetan plateau. Quat. Sci. Rev.
9.
As, Sb and U interactions with minerals
Watkins, R., Weiss, D. J., Dubbin, W., Peel, K., Coles, B. J., and Arnold, T., 2006. Investigations into
the kinetics and thermodynamics of Sb(III) adsorption on goethite (α-FeOOH). J. Colloid Interface Sci.
303, 639-646.
Wainipee, W., Weiss, D. J., Sephton, M., Coles, B. J., and Unsworth, C., submitted. The effect of crude
oil on arsenate adsorption on goethite. Water Res.
10.
A new sorbent for As removal from ground waters
The pollution of ground water with As is threatening millions of people around the world. And despite
several years of intense research and development activities, a reliable and well working sorbent is still
missing. In countries like Bangladesh, major head wells are not functioning due to reasons such as
competitive adsorption of other elements such as phosphorous.
To address this problem we are devising at Imperial College London a 2-stage device that is able to
remove minute concentrations of As from surface and groundwater. During the PhD project, the
student will be involved in (i) synthesising bi-compositional minerals, (ii) testing them with respect to
adsorption, regeneration, etc. and (iii) investigating the mechanisms As adsorption using various
spectroscopic methods.
Parbhakar, A., Cuadros, J., Sephton, M., Dubbin, W., and Weiss, D. J., 2007. An adsorption study of Llysine on smectite and its implication on early life. Colloids Surf. A: Physicochem. Eng. Aspects 307, 142149.
Watkins, R., Weiss, D. J., Dubbin, W., Peel, K., Coles, B. J., and Arnold, T., 2006. Investigations into
the kinetics and thermodynamics of Sb(III) adsorption on goethite (α-FeOOH). J. Colloid Interface Sci.
303, 639-646.