Chapter 5 Activities
5. Atmospheric Deposition & Clean Machines
Introduction
Atmospheric nitrogen deposition is a major source of nitrogen to water and land in Sarasota County. Human-caused (anthropogenic) sources include emissions from fertilizer use; human, pet, and livestock waste; and fossil fuel combustion in power plants, vehicles, and outdoor power equipment. Natural sources include emissions from wild animal waste, lightning, forest fires, and soils. Atmospheric nitrogen compounds return to the earth in dust or rain as nitrogen oxides, ammonium, and nitrates. Direct deposition refers to nitrogen settling directly onto a water body or landscape, while indirect deposition occurs when nitrogen falls on land and is later transported to a water body, often via stormwater runoff or groundwater seepage.
Figure 5.1 Nitrogen emissions from vehicles, power plants, and livestock react in the atmosphere and fall back to the ground in dust and rain. Source: Gulf Coast Community Foundation
Nitrogen deposition rates vary widely, contributing an estimated 9%–75% of total nitrogen loading in bays of the northeastern U.S. (Howarth 2006), 35%–71% in Tampa Bay (Poor et al., 2013a), and 30%–64% in Lakewood Ranch, FL (Jani et al., 2020). Mobile sources like vehicles and landscape machinery release nitrogen emissions close to the ground and may contribute up to four times more nitrogen to the local watershed than regional power plants (Poor et al., 2013b). A 2005 energy analysis of Sarasota County reported that vehicles emitted 9,843 tons of nitrogen oxides—67% of the total—exceeding the national per capita average (Sarasota County Government 2008). Since 1990, driving-related emissions in the Sarasota-Bradenton metro area have risen 61% (Gately et al., 2019). In 2019, transportation was the largest greenhouse gas (GHG) emitting sector in Sarasota County, responsible for 51% of total emissions (Sarasota County Government 2024). Public policies and outreach that promote reductions in local emissions from vehicles and landscaping equipment could significantly reduce atmospheric nitrogen deposition.
Because Sarasota’s airshed extends hundreds of miles, reducing emissions from regional power plants is also important for protecting local water quality. Encouraging policies and behaviors that promote energy efficiency and lower electricity demand can help reduce power plant emissions. Clean Air Act regulations administered by the U.S. Environmental Protection Agency (EPA) have led to significant reductions in nitrogen oxide and nitrate emissions. As coal-fired plants are replaced by cleaner natural gas and solar facilities, the transportation sector is expected to surpass power generation as the region’s largest emissions source (USEPA 2018). Growth in electric vehicles may help offset some of this shift.
Figure 5.2 Florida carbon dioxide emissions by sector from the combustion of coal, petroleum products, and natural gas. Combustion of fossil fuels also emits nitrogen oxides that contribute to nutrient pollution. Source: United States Energy Information Administration
Activity 1:
Estimate Nitrogen Loading From Atmospheric Deposition Using Multiple Monitoring Stations Within Urban Areas
Atmospheric deposition—both direct and indirect—is a major nitrogen source to land and water in Sarasota County. Additional monitoring stations along urban-to-rural and coastal gradients would greatly improve understanding of nitrogen loading to priority water bodies.
Activity 2:
Educate the Public About the Link Between Air and Water Quality and Choices to Reduce Nitrogen Oxide Emissions.
Public awareness is low regarding how air quality influences water quality. Educating the community about the connections between air pollution—especially from motor vehicles and lawn care equipment—and water quality can foster more sustainable choices and encourage support for clean alternatives and smart transportation planning.
