A new study maps the potential of wetlands - an ecosystem flooded with water and supporting a vegetation of aquatic plants - to improve water quality. Through the study, the researchers claim that regrowing wetlands can act as a key strategy for improving water that is laden with contaminants like nitrate.
A new paper featured in the journal Nature builds on the existing knowledge that wetlands can improve water quality. Conducted by researchers from the University of Illinois Chicago and the University of Waterloo, the study now extends this understanding to map the impact of wetlands on nitrate removal from the water.
High levels of nitrate in groundwater, rivers, and coastal areas has been an increasing cause of concern lately. The nitrates reach such water bodies through the runoff from fertilizer and manure application in agricultural regions. The high nitrate levels can ultimately threaten the supply of drinking water and also lead to ¡°problems with algal blooms and degradation of aquatic ecosystems,¡± explains a UIC university release.
The scientists now imagine wetlands as a solution. This is because when nitrate-laden water enters the boundaries of wetlands, a chemical reaction takes place that has a purifying effect on the water. The reaction releases harmless nitrogen gas into the atmosphere and thus results in cleaner water to flow downstream.
In their study, the researchers mapped the potential of this effect at the U.S. scale, particularly in the Mississippi River Basin and Gulf of Mexico regions.
¡°Unfortunately, most wetlands that originally existed in the U.S. have been drained or destroyed to make way for agriculture or urban development. Ironically, areas with the biggest nitrate problems, due to agriculture and intensive use of nitrogen fertilizers, are also usually areas with the fewest numbers of remaining wetlands,¡± said Kimberly Van Meter, UIC assistant professor of earth and environmental sciences and co-lead author of the paper.
After quantifying the amount of nitrate currently being removed by wetlands across the US, researchers concluded that despite the high levels of wetland loss, nitrate loads in some locations might be approximately 50% higher than they are currently without the presence of remaining wetlands.
In addition, the researchers carried out computer model simulations to figure out if wetland restoration might actually benefit water quality further.
¡°We found that by targeting wetland restoration to areas in the U.S. with the highest levels of nitrate pollution, even a 10% increase in current wetland area could cut nitrate levels in rivers and streams by half,¡± UIC¡¯s Van Meter said.
The researchers even found the cost of restoring these wetlands to be around 40 times more effective in purifying water than the ongoing efforts.
¡°You get much more bang for your buck if wetland preservation and restoration are targeted,¡± said Nandita Basu, professor of civil and environmental engineering, and earth and environmental sciences at the University of Waterloo and corresponding author of the paper. ¡°From a policy perspective, it is dramatically more effective and efficient.¡±