Abstract
Urban landscapes are significant contributors of organic carbon (OC) in receiving waters, where elevated levels of OC limit the light availability, increase the transport of pollutants, and result in high costs of potable water treatment. Our objective in this study was to investigate the concentrations, fractions (dissolved and particulate), and loads of OC in a residential catchment (3.89 ha drainage area) located in Florida, United States. The outlet of the stormwater pipe draining the residential catchment was instrumented with an automated sampler, a flowmeter, and a rain gauge. The rainfall and runoff samples collected over 25 storm events during the 2016 wet season (June to September) were analyzed for dissolved organic carbon (DOC) and total organic carbon (TOC), with particulate OC (POC) calculated as the difference between TOC and DOC. Mean concentration of DOC was 2.3 ± 1.7 mg L−1 and POC was 0.3 ± 0.3 mg L−1 in the rainfall, whereas DOC was 10.5 ± 6.20 mg L−1 and POC was 2.00 ± 4.05 mg L−1 in the stormwater runoff. Concentrations of DOC were higher during the rising limb of the hydrograph in 15 out of 25 storm events, suggesting flushing of DOC, with an increase in the amount of runoff, from the landscape sources in the residential catchment. The estimated total export of OC during the 2016 wet season was 66.0 kg ha−1, of which DOC was 56.9 kg ha−1 (86.2% of TOC), and POC was 9.1 kg ha−1 (13.8% of TOC). High concentrations and loads of OC, especially DOC, in the stormwater runoff imply that residential catchments in urban watersheds are hot-spots of DOC influx to water bodies. Reducing DOC transport in the urban landscapes is complex and require identifying the origin of DOC and then using site-specific targeted approaches to mitigate DOC loss.
Highlights
Urbanization affects nutrient retention and transport to water bodies due to the alteration of the hydrologic flow patterns [1,2]
Urban development can contribute to a significant influx of organic carbon (OC) due to the contribution from additional sources, such as lawn grass clippings, leaves, eroded sediments, atmospheric deposition [3], and wastewater flows from sewage
Fractions, and loads of OC in stormwater runoff in a residential catchment located in the subtropical climate
Summary
Urbanization affects nutrient retention and transport to water bodies due to the alteration of the hydrologic flow patterns [1,2]. Many urbanized areas are designed to capture and transport stormwater runoff via hydraulically connected storm network systems [3]. These, in turn, result in altering the structure and function of the urban landscapes and lead to physical, chemical, and biological modifications, eventually affecting downstream ecosystems [4]. These modifications are the primary driver of reduced infiltration, increased stormwater runoff, decreased biodiversity, and increased transport of pollutants [5]. An increase in OC concentrations in water bodies can intensify the binding and co-transport of pollutants, reduce light penetration, lessen vertical heat distribution, and diminish oxygen mixing and production [7]
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