Spatio‐temporal patterns of major ions in urban stormwater under cold climate

Abstract

Multiple natural and anthropogenic factors affect urban water chemistry. However, little is known about the abundance or temporal variation of major ions in urban runoff. This study explores the spatio‐temporal variation of major dissolved ions (Na, K, Ca, Mg, Cl, NO3, and SO4) and total dissolved solids (TDS) in cold climate urban stormwater. Three watersheds with varying degrees of urban land use intensity and imperviousness (from 36% to 66%) in Helsinki, Finland, were continuously monitored for 5 years using an automated sampling procedure to obtain stormwater discharge and ion concentrations and, thus, loadings. High‐resolution datasets, including long‐term continuous discharge, both measured and simulated (using Storm Water Management Model), and automatic water quality sampling enabled the accurate calculation of loads of ions and TDS. Water quality was related to explanatory watershed characteristics (e.g., watershed physiography and sampling time) using hierarchical clustering, nonmetric multidimensional scaling, and hierarchical partitioning methods. Urban land use contributed to increased ion concentrations and loads year‐round. This study highlights how stormwater ion concentrations are elevated across seasons, indicating chronic pollution phenomena. The greatest loads occurred during summer (except for Na and Cl), while the highest variation in loads was observed in autumn. Significant clusters among ions were found in the hierarchical cluster analysis, suggesting similar temporal patterns and sources for the ions in each cluster. The importance of land use was evident, though in the most urbanized watershed, concentrations were not linked to any of the investigated watershed characteristics. Based on our results, only Na and Cl are manageable by alternative winter road antiskid practices, whereas other ions resulted from diffuse pollution sources, being therefore more difficult to control. Finally, this study contributes to an increased understanding of the temporal and spatial patterns of ions in stormwater and highlights the need for consistent time series data for ion monitoring under cold climatic conditions in order to enable reliable estimates of their loads to adjacent water bodies. Finally, year‐round stormwater treatment is highly recommended.

Urban Stormwater Characterization, Control and Treatment

“…At least four studies focused on thermal and/or salt loads transported by urban runoff. Although salts are likely to follow strong seasonal patterns, with the highest export in the spring following wash-off of winter deicing chemicals, Taka et al (2017) reported chronically elevated salt concentrations across three urban watersheds in Finland. In this study, Cland Na + were linked to winter deicing activities, while Ca 2+ , K + and Mg 2+ were likely associated with weathering of other urban surfaces.…”

Distributions and Sources of Sedimentary Sterols as well as Their Indications of Sewage Contamination in the Guanting Reservoir, Beijing

“…For quality assurance and quality control, the external standard method was used for quantitative analysis based on six-point calibration (1,2,4,6,8, and 10 μg ml −1 ). e linear regression coefficients for cholesterol, cholestanol, coprostanol, epicoprostanol, campesterol, sitosterol, and stigmasterol were 0.989, 0.979, 0.977, 0.986, 0.941, 0.992, and 2…”

“…With strict industrial pollution control, domestic sewage discharge has increasingly become the main concern of water quality issues in many populated regions [1][2][3][4]. Sterols have been widely used as a typical biochemical marker to indicate the source of organic matter, such as domestic sewage, marine, and terrestrial source [5][6][7].…”

Are drivers of microbial diatom distributions context dependent in human‐impacted and pristine environments?

“…Anthropogenic land use, comprising agriculture, development and urbanization, contributes to increased nutrient and ion concentrations (Taka et al. ), pollutants and turbidity (due to sediment load) in streams (Foley et al. ), and these effects cascade downstream (Levesque et al.…”

“…For example, land cover previously dominated by agriculture may sustain high nutrient loads from sediments to streams for a long time period after a change in land use (Maloney and Weller 2011). Anthropogenic land use, comprising agriculture, development and urbanization, contributes to increased nutrient and ion concentrations (Taka et al 2017), pollutants and turbidity (due to sediment load) in streams (Foley et al 2005), and these effects cascade downstream (Levesque et al 2017). Wang et al (2008) found that nutrient loading and percent of urban land use were the most important drivers of deteriorating stream conditions.…”