Current and Recent Projects and Collaborations

Submarine Groundwater Discharge

Submarine groundwater discharge is a flow of fresh groundwater and recirculated seawater from a coastal aquifer into the ocean and is recognized as a pathway of dissolved components from land to the coastal zone. This water often carries pollutants from anthropogenic sources, for example nutrients and pharmaceuticals from sewer systems, cesspools, or agricultural activities on land. The distribution of these sources along the coastline is not uniform, and the same is true about the magnitude of groundwater discharge. Consequently we are confronted with variable non-point source pollution at the land-ocean interface.

Submarine groundwater discharge on the Kona coast of Hawaii Island.

Our research focuses on the assessment of groundwater discharge in Kona. We use geochemical tracers to derive groundwater fluxes into the coastal zone, investigate its composition, origin, and driving forces. We are looking at short- and long-term variability in fluxes and composition. We performed several in situ short-term time-series measurements of groundwater discharge rates, calculated groundwater-derived nutrient and pharmaceutical (waste water tracer) fluxes, and coastal residence time of groundwater derived nutrients. Within this project we also constructed a new autonomous continuous radon monitor called SGD Sniffer - the newest technology for long-term SGD monitoring. See details here.

Sustainable ecosystem management: analysis of water resources and water quality.

Coastal communities in Pacific Islands have a common set of problems related to global climate change and increased population growth including impacts on water resources, water quality and down-stream coastal ecological health. We have been collaborating with community organizations in Hawaii and American Samoa and have been working on constructing hydrological models based on measured and geochemical tracer-derived water fluxes. We are assessing water resources and projected availability in watersheds with respect to current land-use and proposed restoration efforts under future climate projections.

Assessment of Groundwater Derived Nutrient Inputs.

In several interdisciplinary projects we have been looking at SGD and corresponding nutrient fluxes at various locations around the islands. We combine natural radioactive tracers, nitrogen isotopes, hydrogen and oxygen stable isotopes, waste water tracers (pharmaceuticals, personal care products), geophysical methods, hydrological models and many other tools to assess land-ocean fluxes. Among others some of the most anthropogenically affected sites we studied are: Kihei, Lahaina, Pearl Harbor, Maunalua Bay, Kailua-Kona, Haleiwa, Kahaluu, Waimanalo, and many others.

Cesium isotopes in the Pacific Ocean following the Fukushia Dai-ichi NPP accident

We have been studying the dispersion patterns of cesium isotopes released from Fukushima in the North Pacific Ocean. We have created time series cesium records at the Hawaiian Islands and spatial distribution maps in the west and central Pacific. More studies on cesium isotopes in fish, mushrooms and soil were also performed on the Hawaiian Islands Our results can be found here.

Within this project we developed two highly efficient methods for cesium separation from seawater. Please see work done by postdoc Jan Kamenik.

Tracing shelf-derived component transport offshore

Natural Iron Fertiliztaion in the Southern Ocean: Investigating Horizontal Iron Transport and Vertical Carbon Flux Using Radium Isotopes and ²³⁴Th.

There are regions of the high nutrient-low chlorophyll (HNLC) Southern Ocean that appear to be naturally fertilized by iron sources other than atmospheric deposition. One such area is the Southern Scotia Sea, downstream of the Antarctic Peninsula and the Shackleton Fracture Zone (SFZ). Here, we used radium isotopes as tracers of water transport to investigate the possibility that shelf-derived Fe is fueling phytoplankton blooms. We used ²²⁴Ra to calculate the rate of shelf derived iron transport into the HNLC offshore waters where we calculated the corresponding vertical carbon flux using ²³⁴Th.

Sources of Iron to the Eastern Tropical Atlantic: Does the Continental Margin Supplement Saharan Dust?

On a cross-shelf transect near Mauritania we examined lateral source of Fe from the continental margin. We combined measurements of specific tracers to uniquely determine the importance of lateral transport vs. dust inputs and subsurface remineralization as Fe sources to the surface ocean.

Development of New Radiochemical Methods

Determination of ²²⁷Ac in Young Basaltic Samples.

²²⁷Ac can be used as a radiometric dating tool and tracer of melt transport rates and magma storage times. For this application I developed an extraction chromatographic method to separate ²²⁷Ac from the rock matrix. The actinium values will be used by Ken Sims (WHOI G&G) in combination with ²³¹Pa as a chronometer for dating of young mid-ocean ridge basalts in the time range of 10-100 years.

Autonomous Long-term Measurement of ²¹⁴Bi in Coastal Water .

We use ²²²Rn as a groundwater discharge tracer and developed a very efficient autonomous instrument based on gamma-spectrometry, using ²¹⁴Bi photo-peak, for its long-term measurement. The method allows unattended hourly measurements of radon for many years. The instrument is called SGD Sniffer and has been deployed at multiple coastal sites. See details here.