What are the relevant sources and factors affecting event mean concentrations (EMCs) of nutrients and sediment in stormwater?

Authors: BEHROUZ, MINA SHAHED - Virginia Polytechnic Institution & State University; YAZDI, MOHAMMAD NAYEB - The Ohio State University; SAMPLE, DAVID - Virginia Polytechnic Institution & State University; SCOTT, DURELLE - Virginia Polytechnic Institution & State University; Owen Jr, James - Jim

Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/3/2022
Publication Date: 3/6/2022
Citation: Behrouz, M., Yazdi, M., Sample, D.J., Scott, D., Owen Jr, J.S. 2022. What are the relevant sources and factors affecting event mean concentrations (EMCs) of nutrients and sediment in stormwater? Science of the Total Environment. 828. Article 154368. https://doi.org/10.1016/j.scitotenv.2022.154368.
DOI: https://doi.org/10.1016/j.scitotenv.2022.154368

Interpretive Summary: This article investigated: (1) the effects of climatological [precipitation (duration and depth) and antecedent dry period (ADP; i.e. time between storm events] and water catchment characteristics (slope, area, percent imperviousness, subsurface soil characteristics) on stormwater quality and (2) common sources of nitrogen and phosphorus forms and sediment affecting stormwater quality in urban areas. The extension of knowledge discussed in this manuscript demonstrates that for some stormwater quality constituents (i.e. particulate nitrogen, particulate phosphorous, and sediment) other factors exert a more important influence on stormwater quality than the antecedent dry period which is the only factor present in current Build-up/Wash-off (BUWO) equations. Using the conventional approach solely on land use and ADP for stormwater quality modelling and prediction is questionable, as it does not provide insight into the processes impacting stormwater quality and the role played by influential factors, including precipitation and catchment characteristics. The inputs required in H/H/WQ models are mainly related to climatological and catchment characteristics. Considering these variables is advantageous, as they can be imported directly in the BUWO equations within most urban watershed models.

Technical Abstract: Urbanization increases runoff, sediment, and nutrients loadings downstream, causing flooding, harmful algal blooms, and eutrophication. Most watershed models apply land-use derived parameters (e.g. nutrient concentrations); coupled with a variety of methods for quantifying loads, the most common being Build-up/Wash-off (BUWO) equations where loading is a function of antecedent dry period (ADP). However, several studies have not found a correlation between constituent loads in stormwater and ADP. The objective of this study is to verify this finding and discover which climatological or catchment characteristics are the most significant in affecting runoff loads and should be included in the BUWO relationship. Stormwater quality data was obtained from the National Stormwater Quality Database (NSQD), which is the largest data repository for stormwater in the U.S. Bayesian Network Structure Learner (BNSL) was used to assess the relationships between catchment characteristics, climatological information, and stormwater quality for selected land uses. Given the optimal BN structure, it was determined which parameters most affect stormwater quality Event Mean Concentrations (EMCs). The results demonstrate that for some constituents (i.e. particulate nitrogen, particulate phosphorous, and sediment), other factors (i.e. precipitation depth and duration, surface slope) exert a far greater important influence on stormwater quality than ADP.