Work Package 5 (Gaßmann, Zielinski, Wurl)

"Microfluidic sample treatment for dissolved organic matter"

Broader background of the proposed research project

For the investigation of DOM numerous sophisticated laboratory analysis methodologies are available, still further methodologies need to be developed, especially with respect to the field applicability. With the help of a microfluidic system well defined abiotic conditions (e.g. temperature, UV radiation, etc.) can be achieved in a uniform, precise and rapid way. Thus DOM samples can be exposed to these conditions and subsequent changes of the sample can be studied. This will help to understand the complex behavior of the DOM.

In previous experiments, the microfluidic treatment of DOM samples with temperature was already carried out (Gassmann et al. 2015, Miranda et al. 2015). The advantage of the microfluidic setup was demonstrated and a significant change in the fluorescence excitation-emission-matrix spectrum of the DOM sample was observed. The response of DOM to UV is well documented and occurs especially near the sea surface (Wurl et al. 2009, Blough 1997). Specific conditions of the surface layer can be mimicked using the microfluidic approach for a better understanding. Further investigations will include separating columns or electrical fields added to the system. The in-depth investigation of the temperature influenced structural change of DOM as well as the treatment with high ultraviolet (UV) radiation will be done in the framework of EcoMol. Once the response of DOM under the treatment is understood this methodology can be used as an improvement of existing sensing methodologies. So the sample is treated first with the microfluidic system potentially helping to remove cross sensitivities and leading to more precise sensing result.

Outline for the proposed PhD research project

During this research project a microfluidic system will be developed which is able to apply different treatments to DOM samples. First, a system for laboratory use will be developed. Different sample treatments should be implemented (e.g. temperature, UV, electrical field, separation columns). Once the system is operable different treatments with known samples will be performed. The results need to be validated with sophisticated laboratory analysis methodologies available in EcoMol (e.g. FT-ICR-MS, WPs 3 and 4). Main questions concerning UV treatment could be: Can the DOM break up at the sea surface (WP 15) as modeled in the microfluidic system? How will DOM behave when parameters like wavelength or intensity are changed? This aims towards a better understanding of the complex behavior of the DOM and should be used to improve in situ sensors. The PhD research will be combining engineering work with aspects of the biology and chemistry of the ocean. The EcoMol training group will be the ideal framework for this cooperation.