NERC DOMAINE Project – University of Bristol

Characterising the nature, origins and ecological significance of Dissolved Organic Matter IN freshwater Ecosystems.

Background
Research scientists from the University of Bristol, School of Geographical Sciences have recently asked Wavelength Environmental to supply a range of sophisticated water quality monitoring instrumentation for a prestigious NERC (Natural Environment Research Council) funded project looking in detail at dissolved organic matter (DOM) in freshwater ecosystems and public water supply. The NERC DOMAINE project aims to resolve the role of DOM in the cycling, transport and downstream export of the major nutrients – carbon, nitrogen and phosphorus. Using state of the art sensing technologies they will investigate the character and functional significance of DOM in UK freshwater catchments.

DOMAINE will address big questions of international significance, reducing the uncertainties associated with current scientific understanding of the major biogeochemical cycles, and underpinning the development of improved modelling approaches to better predict the ecosystem health, goods and services of aquatic ecosystems under changing land use and climate.

Monitoring instrumentation
The project team led by Professor Penny Johnes, in collaboration with colleagues from Bangor University, the Centre for Ecology and Hydrology and the University of East Anglia, had already identified the Submersible Ultraviolet Nitrate Analyser (SUNA) from Sea-Bird Coastal / Hach Hydromet as a key instrument for enabling greater understanding of the behavior of DOM in freshwater systems. The SUNA V2 is a chemical-free UV nitrate sensor that uses the full UV spectrum (190 – 370 nm wavelength range) to measure nitrate with industry-leading accuracy across the entire sensing range. Whilst the nitrate concentrations will be of some interest, it is by delving deeper into the raw spectral data that the DOMAINE research team expect to find the most valuable insight into DOM behavior. The SUNA V2 has been upgraded with a reduced 5mm path-length and adaptive sampling logic to deliver improved performance in highly turbid conditions and applications with high levels of coloured DOM (CDOM).

Alongside the SUNA V2 the NERC DOMAINE project will be deploying submersible fluorometers from the Sea-Bird Coastal ECO (Environmental Characterisation Optics) line of sensors. Instruments tuned for chlorophyll-a and CDOM will shed more light on other key areas of the fluorescence excitation emission matrix.  Turbidity, dissolved oxygen and pH information will come from a Hydrolab MS5 mini-sonde deployed at each monitoring location, and water level and flow data will be collected using Hach Flow area velocity units. The Hach Flow FL900 Series flow logger is a rugged and reliable solution for open channel flow monitoring and can be paired with a wide range of sensor technologies from the non-contact FLO-DAR AV and down-looking ultrasonic sensors to submerged Doppler and electro-magnetic units. For this project the Doppler sensors will be used and with their built in pressure transducer they will calculate flow and level which will be important for understanding the context for the water quality data collected by the other sensors

An important part of the DOMAINE project will be the detailed analysis carried out on water samples back at the University laboratory. To make sure that these samples are collected at key times throughout the various processes and cycles and coincide with peaks and features observed by the sensors – portable automatic samplers from Hach Lange will also be deployed at each site. The Sigma SD900 uses an improved peristaltic pump to deliver repeatable sample volumes at a timed interval or upon receipt of a trigger pulse. The SD900 has been recently redesigned and now features a 5-line, transflective LED, backlit display that is readable in bright sunlight or subdued lighting. Ease of use and reduced maintenance are at the heart of the SD900 – the peristaltic pump now features spring-loaded rollers which reduce wear and tear on the pump and extend the tubing life to twenty times longer than other samplers.

Data logging, control and telemetry
With such a wide range of sophisticated sensing technology deployed it was the perfect opportunity to include the versatile netDL 500 IP datalogger from OTT Hydromet. The netDL can take in data from each of the sensors and store it in one time stamped file. Data is downloadable on site via a USB stick or connection to a laptop and sensor values can be checked via the local display. With the optional GPRS modem the datalogger is transformed into a powerful remote telemetry unit, delivering data from the field to a desktop PC via the mobile phone network. The netDL 500 can also perform complex calculations on board and will be able to send out commands to the sensors or a trigger pulse to the automatic sampler if any parameter or range of parameters meets predetermined trigger conditions. This may be an accelerated sensor interrogation rate in times of rapid change, collection of water samples at certain CDOM thresholds or targeted sampling on the rising or falling limb of a storm hydrograph. The netDL 500 not only provides a single point of access to the sensor suite, but with its flexible and powerful remote control functions it will ensure that the research team are able to concentrate on analysing and interpreting results without the distraction of managing a complex sensor suite in a remote location.