Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Freshwater and Saltwater Interactions in Coastal Groundwater Systems May Provide Clues to Chemicals Entering Coastal Waters

05.09.2005


Scientists have recently recognized an imbalance in the flow of salty groundwater into the coastal ocean: considerable saltwater discharge into the ocean has been observed, but little or no return flow has been seen. Now it appears that the timing of the discharge may be key to the health of our coastal waters.



New measurements and models suggest that seasonal changes in the water table may provide clues to how water is exchanged and why the largest discharge occurs during the summer, when the coastal ocean may be most vulnerable to the dissolved chemicals in the groundwater because biological activity is at its highest and river inflow at its lowest.

Fresh and salty groundwater flows into coastal waters as submarine groundwater discharge and is an important source of nutrients, contaminants and trace elements to the coastal ocean. Recent research has revealed that a large portion of submarine groundwater discharge is saline water. Although this water was once ocean water, the mechanism controlling its flow into and out of the sediments has not been previously determined. Using seepage meters and geochemical tracers, scientists have directly measured and inferred groundwater flow from land to sea. But they have not previously been able to observe the opposite, large-scale flow or intrusion of seawater into coastal aquifers to balance this exchange.


In a paper published August 25, 2005 in Nature, scientists from the Massachusetts Institute of Technology (MIT) and Woods Hole Oceanographic Institution (WHOI) made both direct and indirect measurements of flows back and forth at Waquoit Bay, Massachusetts at various seasons of the year and compared those results with a general model of a coastal groundwater system. Their findings reveal a lag in the inflows and outflows related to seasonal changes in the water table.

Study co-author Ann Mulligan of the WHOI Marine Policy Center says seawater is drawn into aquifers as the freshwater-saltwater interface or boundary moves landward during winter. The water discharges back into coastal waters as the boundary moves seaward in summer. Since summer is typically associated with higher temperatures and evaporation, saltwater should intrude inland rather than discharge at the coast. However, the numerical model reveals that there may be a time lag of several months between precipitation, groundwater recharge, and associated impacts on saltwater flowing into or out of the aquifer.

“We looked at several mechanisms other than seasonal exchange that could drive saltwater circulation, including tides, wave run-up on the beach, and entrainment or trapping of saltwater into fresh,” Mulligan said. “ But each of these flows balanced over a tidal cycle and occurs in a well-defined relatively small area, and could not account for the large discharge we observed during summer in Waquoit Bay.“

The study was conducted at the Waquoit Bay National Estuarine Research Reserve in Falmouth, Massachusetts and supported by the National Science Foundation.

The authors say the global extent of seasonal exchange of freshwater and saltwater is unknown but could be an important factor in transporting nutrients and contaminants trapped in sediments into coastal waters. Because the chemistry of coastal waters is affected, it is important to understand the link between the seasonal hydrologic cycle on land and the saline groundwater system in coastal aquifers. Now that a major driving mechanism of saline water flow has been determined, important follow-up studies will look at the chemical content of the inflowing and outflowing water over a yearly cycle. Most previous studies have looked at chemical loading from groundwater over short time-periods, but this study shows that a major process is occurring on a yearly cycle.

“The impact on coastal chemistry could be enormous,” Mulligan says. “Along the U.S. east coast the greatest saltwater discharge may occur in summer, when biological activity is at its highest and river inflow at its lowest. The input of nutrients at certain times of the year may be key to the health of our coastal waters.”

Shelley Dawicki | EurekAlert!
Further information:
http://www.whoi.edu

More articles from Ecology, The Environment and Conservation:

nachricht Foxes in the city: citizen science helps researchers to study urban wildlife
14.12.2018 | Veterinärmedizinische Universität Wien

nachricht Machine learning helps predict worldwide plant-conservation priorities
04.12.2018 | Ohio State University

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Data storage using individual molecules

Researchers from the University of Basel have reported a new method that allows the physical state of just a few atoms or molecules within a network to be controlled. It is based on the spontaneous self-organization of molecules into extensive networks with pores about one nanometer in size. In the journal ‘small’, the physicists reported on their investigations, which could be of particular importance for the development of new storage devices.

Around the world, researchers are attempting to shrink data storage devices to achieve as large a storage capacity in as small a space as possible. In almost...

Im Focus: Data use draining your battery? Tiny device to speed up memory while also saving power

The more objects we make "smart," from watches to entire buildings, the greater the need for these devices to store and retrieve massive amounts of data quickly without consuming too much power.

Millions of new memory cells could be part of a computer chip and provide that speed and energy savings, thanks to the discovery of a previously unobserved...

Im Focus: An energy-efficient way to stay warm: Sew high-tech heating patches to your clothes

Personal patches could reduce energy waste in buildings, Rutgers-led study says

What if, instead of turning up the thermostat, you could warm up with high-tech, flexible patches sewn into your clothes - while significantly reducing your...

Im Focus: Lethal combination: Drug cocktail turns off the juice to cancer cells

A widely used diabetes medication combined with an antihypertensive drug specifically inhibits tumor growth – this was discovered by researchers from the University of Basel’s Biozentrum two years ago. In a follow-up study, recently published in “Cell Reports”, the scientists report that this drug cocktail induces cancer cell death by switching off their energy supply.

The widely used anti-diabetes drug metformin not only reduces blood sugar but also has an anti-cancer effect. However, the metformin dose commonly used in the...

Im Focus: New Foldable Drone Flies through Narrow Holes in Rescue Missions

A research team from the University of Zurich has developed a new drone that can retract its propeller arms in flight and make itself small to fit through narrow gaps and holes. This is particularly useful when searching for victims of natural disasters.

Inspecting a damaged building after an earthquake or during a fire is exactly the kind of job that human rescuers would like drones to do for them. A flying...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

ICTM Conference 2019: Digitization emerges as an engineering trend for turbomachinery construction

12.12.2018 | Event News

New Plastics Economy Investor Forum - Meeting Point for Innovations

10.12.2018 | Event News

EGU 2019 meeting: Media registration now open

06.12.2018 | Event News

 
Latest News

When a fish becomes fluid

17.12.2018 | Studies and Analyses

Progress in Super-Resolution Microscopy

17.12.2018 | Life Sciences

How electric heating could save CO2 emissions

17.12.2018 | Power and Electrical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>