Matteo F. Kausch

PhD candidate

Research Interests

biogeochemistry, reactive transport, soil aggregates, selenium

Research Description

Aggregate scale transport and biogeochemical heterogeneity effects on selenium reduction and retention in soils

Selenium (Se) plays a role of twofold importance in the environment: Trace amounts are essential to the growth and wellbeing of animals and microorganisms, while toxicity rapidly ensues at elevated concentrations. Bioavailable Se oxyanions can be immobilized in nature by microbial reduction to solid, elemental Se. In structured soils, which are characterized by strong systematic heterogeneity at the cm scale, mass transfer limitations arising from predominantly diffusive transport domains within soil aggregates are likely to affect Se reduction rates. Working with simplified experimental systems in conjunction with reactive transport modeling, I quantify potential gradients occurring during Se reduction within soil aggregates and elucidate their driving factors.

The experimental focus of my work lies on flow-through experiments utilizing artificial soil aggregates that physically resemble the complex structures found naturally in most soils. Experiments were performed (a) under oxic and anoxic conditions to constrain the influence of oxygen on Se reduction, (b) using different concentrations of organic carbon sources and dissolved Se-species, the reactants of Se reduction, (c) using different isolation cultures of Se reducers (Thauera selenatis and Enterobacter cloacae SLD1a-1), and (d) using different solid matrices that affect the transport of selenium oxyanions via sorption (plain quartz sand and ferrihydrite coated quartz sand were compared). Temporally resolved data on solution chemistry at the outflow and spatially resolved data on solid phase Se within the aggregates was collected. I am currently developing a reactive transport model to fit these experimental results and aid in their interpretation as outcome of the interplay between measured and inferred driving factors. These factors include: heterogeneous and dynamic concentration fields of chemical species determining the reaction rates, bacterial cell densities, sorption, as well as transport of reactants in a spatially variable flow field.

Insights gained at the aggregate scale have the potential to greatly improve our fundamental understanding of Se cycling in soils and enhance predictive capabilities for Se transport and attenuation, thus aiding in the management and remediation of Se contaminated areas. For example, my research showed that aggregates may improve selenium retention in a soil by creating anoxic environments conducive to the reduction process and by accumulating reduced selenium at their cores. Promoting soil aggregation on seleniferous agricultural soils, through the addition of organic matter and reduced tillage, may thus be an effective management practice to alleviate the toxic effects of selenium contaminated drainage water on aquatic ecosystems.

Selected Publications

Kausch, M., Ng, P., Ha, J. and Pallud C. (in print) Soil-aggregate-scale heterogeneity in microbial selenium reduction. Vadose Zone Journal (Reference: V11-0101.)

Kausch, M. and Pallud, C., 2012. Spatial heterogeneity of selenium reduction in model soil aggregates. AGU Fall meeting H53F-1471. (Poster)

Kausch, M. and Pallud, C., 2011. Impact of ferrihydrite coating and aeration conditions on microbial selenium (Se) reduction and retention in artificial soil aggregates. Mineralogical Magazine 75, 1157. (Oral)

Kausch, M., Ha, J. and Pallud, C., 2010. Heterogenous selenium reduction in artificial soil aggregates. Geochim. Cosmochim. Acta. 74 (Suppl. 1): Abstract 499. (Oral)

Pallud, C., Kausch, M., Fendorf, S. and Meile, C., 2010. Patterns and spatial modeling of reductive ferrihydrite transformation observed in artificial soil aggregates. Environmental Science & Technology 44, 74-79.

Kausch, M., Meile, C. and Pallud, C., 2008. Spatial modeling of iron transformations within artificial soil aggregates. Eos, Transactions, AGU 89, Fall Meeting Supplement, Abstract B11B-0357. (Poster)

Koschinsky, A., Kausch, M., Borowski, C. (in review) Metal concentrations in the tissues of the hydrothermal vent mussel Bathymodiolus: Reflection of different metal sources. Submitted to Marine Environmental Research.

Honors and Awards

Bay Area Water Quality Fellowship (2012)

Hans and Jean Jenny Graduate Fellowship (2011)

James P. Bennet Agricultural Fund (2011)

UC Berkeley, Graduate Division Summer Grant (2011)

Goldschmidt Conference Travel Grant (2010)

Recent Teaching

• ESPM 9 - Environmental Science Case Study Seminar (2011 and 2012)
• ESPM 2 - The Biosphere (2009 and 2010)
• Biology 1B - Plant/fungal diversity, evolution & ecology (2008)

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