Long term trends in nitrate and chloride in streams in an exurban watershed, Emma Castiblanco '21

In moderation, eating salt-laden junk food is not terrible; however, eating too much salt can have serious consequences for our health. The same is true for the environment. Too much salt is a very bad thing.

A watershed is an area of land wherein all the streams and small waterbodies flow into a common, larger body of water like a river or bay. When we expose our watersheds to ‘junk food’ like excess fertilizer and road salt, the water can become unhealthy and pose larger ecological problems.

Too much fertilizer flowing into a water body can increase nitrate levels and cause eutrophication. Like eating too much ice cream, eutrophication is essentially too much of a good thing. Nutrients are needed to feed plants; we tend to think of nutrients as good. But high concentrations of nutrients can cause ecosystem imbalances. In water bodies, nutrients that are swept into bodies of water with precipitation feed algae, which can lead to algal blooms. These blooms block sunlight, preventing photosynthesis in the plants growing under water. When plants do not have enough light, they eventually die. Bacteria in the water digest the dead plants, a process which involves absorbing oxygen and emitting carbon dioxide. When there is no more oxygen in the water, animals in the water, like fish, have no oxygen and die.

Additionally, too much salt flowing off roads from winter deicing efforts can increase salinity levels in surrounding bodies of water and threaten aquatic life. Like with fertilizer, the road salt we use for deicing washers into watersheds after it rains. We use road salt as a deicer for our roads to prevent ice from forming and making the roads dangerous. Sodium chloride road salt works to prevent the formation of ice crystals by lowering the freezing point of water. While road salt prevents dangerous driving conditions, dumping tons of salt onto our roads makes freshwaters salty. When there is too much salt in the water, freshwater organisms are not able to maintain healthy levels of salt and other solutes in their bodies.

Researchers with the Baltimore Ecosystem Study (BES) have been collecting information on how much ‘junk food’ watersheds outside of suburban Baltimore are absorbing. For over two decades, the levels of chloride and nitrate in the watersheds have been collected.

This summer, I looked at data on chloride and nitrate levels in the watersheds of Baltimore County collected by the BES. Additionally, I found data on the amount of fertilizers and road salt being applied to areas within Baltimore County. Using this information, I analyzed the relationship between chloride and nitrate levels in Baltimore County watersheds and the amount of fertilizer and road salt being used by homeowners and municipalities.Exurban areas are outside of urban and suburban environments and are often understudied, making this research important. By studying the exurban areas, we are able to see that even with little human influence (ie. small population density and limited roads/infrastructure) there are drastic effects on the environment. The two areas that water samples were taken from were Baisman Run (an exurban watershed) and Pond Branch (a forested watershed). Unsurprisingly, the chloride and nitrate concentrations are significantly higher in the exurban water than the forested water.

Additionally, we found that while the amount of road salt being used each winter has not increased significantly, the amount of chloride in the exurban watershed has been increasing. This leads us to believe that chloride is accumulating in the water.

Nitrate levels at the exurban watershed have not increased significantly, but they have remained at an extremely high level. This means there is also nitrate retention in the water. We need to think about ways to reduce salt and nitrate flowing into Baltimore waterways.

We need to understand the long-term effects of elevated salt and nitrate levels on Baltimore County watersheds, as well as watersheds facing similar problems across the country. Since road salt and fertilizer are needed to maintain safe winter roads and grow vivacious plants, we need to look at alternatives. While we explore alternatives, we must be aware of the barriers preventing implementation of alternative methods of deicing and fertilizing.

Like with food, access to healthier alternatives is a matter of expense. Food that is organic, GMO-free, and generally better for us tends to be more expensive than foods with less nutritional value. The same is true for deicers and fertilizers. Some alternatives to sodium chloride road salt have been studied – and work. These include snow melt mats, potassium chloride, and cat litter. Unfortunately, while many of the alternatives are better for the environment, they tend to be very expensive and are therefore not feasible options for all communities. Similar to how socioeconomic status influences access to healthy foods, watershed health is determined by whether communities can afford eco-friendly alternatives for deicing their roads and feeding their plants.

This may seem like an overwhelming problem, but there are many creative and passionate minds working to find solutions. Viable alternatives for deicers and fertilizers are in hand; now we need to find ways to make these healthy options accessible for all communities.