Freshwater salinization syndrome (FSS) refers to the suite of interactive effects of salt ions on degradation of physical, biological,and social systems. Best management practices (BMPs), which are methods to effectively reduce runoff and nonpoint source pollution (stormwater, nutrients, sediments), do not typically consider management of salt pollution. We investigate impacts of FSS on mobilization of salts, nutrients, and metals in urban streams and storm water BMPs by analyzing original data on concentrations and fluxes of salts, nutrients, and metals from 7 urban watersheds in the Mid-Atlantic USA and synthesizing literature data. We also explore future critical research needs through a survey of practitioners and scientists. Our original data show 1) sharp pulses in concentrations of salt ions and metals in urban streams directly following both road salt events and stream restoration construction (e.g.,similar to the way concentrations increase during other soil disturbance activities); 2) sharp declines in pH (acidification) in response to road salt applications because of mobilization of H+ from soil exchange sites by Na+; 3) sharp increases inorganic matter from microbial and algal sources (based on fluorescence spectroscopy) in response to road salt applications, likely because of lysing cells and changes insolubility; 4) substantial retention (~30–40%) of Na+ in stormwater BMP sediments and floodplains in response to salinization; 5) increased ion exchange and mobilization of diverse salt ions (Na+, Ca2+, K+, Mg2+), nutrients(N, P), and trace metals(Cu, Sr) from stormwater BMPs and restored streams in response to FSS; 6) downstream increasing loads ofCl–, SO42–, Br–, F–,andI–along flowpaths through urbanstreams and P release from urban stormwater BMPs in response to salinization; and 7)a substantial annual reduction (>50%) in Na+concentrations in an urban stream when road salt applications were dramatically reduced, which suggests potential for ecosystem recovery. We compare our original results with published metrics of contaminant retention and release across a broad range of stormwater BMPs from North America and Europe.Overall, urban streams and stormwater BMPs consistently retain Na+ and Cl–but mobilize multiple contaminants based on salt types and salinity levels. Finally, we present our top 10 research questions regarding FSS impacts on urban streams and stormwater BMPs. Reducing diverse chemical cocktails of contaminants mobilized by freshwater salinization is a priority for effectively and holistically restoring urban waters.
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Stormwater best management practices: Experimental evaluation of chemical cocktails mobilized by freshwater salinization syndrome
Freshwater Salinization Syndrome (FSS) refers to the suite of physical, biological, and chemical impacts of salt ions on the degradation of natural, engineered, and social systems. Impacts of FSS on mobilization of chemical cocktails has been documented in streams and groundwater, but little research has focused on the effects of FSS on stormwater best management practices (BMPs) such as: constructed wetlands, bioswales, ponds, and bioretention. However emerging research suggests that stormwater BMPs may be both sources and sinks of contaminants, shifting seasonally with road salt applications. We conducted lab experiments to investigate this premise; replicate water and soil samples were collected from four distinct stormwater feature types (bioretention, bioswale, constructed wetlands and retention ponds) and were used in salt incubation experiments conducted under six different salinities with three different salts (NaCl, CaCl2, and MgCl2). Increased salt concentrations had profound effects on major and trace element mobilization, with all three salts showing significant positive relationships across nearly all elements analyzed. Across all sites, mean salt retention was 34%, 28%, and 26% for Na+, Mg2+and Ca2+respectively, and there were significant differences among stormwater BMPs. Salt type showed preferential mobilization of certain elements. NaCl mobilized Cu, a potent toxicant to aquatic biota, at rates over an order of magnitude greater than both CaCl2and MgCl2. Stormwater BMP type also had a significant effect on elemental mobilization, with ponds mobilizing significantly more Mn than other sites. However, salt concentration and salt type consistently had significant effects on mean concentrations of elements mobilized across all stormwater BMPs (
- Award ID(s):
- 2021089
- PAR ID:
- 10470081
- Publisher / Repository:
- Frontiers
- Date Published:
- Journal Name:
- Frontiers in Environmental Science
- Volume:
- 11
- ISSN:
- 2296-665X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Freshwater ecosystems are being exposed to increasing salinisation, often because of pollution from road deicing salts, which is becoming more widely acknowledged. To address this issue, municipalities are turning towards the sodium salt alternatives of CaCl2and MgCl2, which are marketed as being safer for the environment. However, research into the actual safety of these salts on aquatic plants is lacking.
We investigated the effects of the most common road salt (NaCl) and two alternatives (MgCl2and CaCl2) on the productivity of a common freshwater plant (i.e.,
Elodea canadensis ) under three salt concentrations (control, 250, and 1,000 mg Cl−/L). Light‐bottle/dark‐bottle trials were performed to quantify net primary productivity, respiration, and gross primary productivity. These responses were tracked over time (1 vs. 3 weeks) to assess plant acclimation and lag effects under different levels of the three salts.We discovered that NaCl and CaCl2altered these measures of plant metabolism, but MgCl2had no effects. We also observed instances of acclimation (i.e. salt effects after 1 week that disappeared after 3 weeks) and lag effects (i.e. no salt effect after 1 week, but salt effects after 3 weeks). These impacts are likely to be the results of plant responses to salt at the cell and molecular levels, including short‐ and long‐term changes in photosynthetic pigments. Therefore, the plant responses were salt‐specific, with instances of plant acclimation and lag effects.
This appears to be the first study of net primary productivity, respiration, and gross primary productivity in freshwater plants across a range of different salts, and it highlights how freshwater salinisation can have substantial effects on plant productivity. These effects will probably have an impact on the growth of macrophytes, which play key ecological roles in aquatic ecosystems.
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Abstract Freshwater salinization is an emerging global problem impacting safe drinking water, ecosystem health and biodiversity, infrastructure corrosion, and food production. Freshwater salinization originates from diverse anthropogenic and geologic sources including road salts, human-accelerated weathering, sewage, urban construction, fertilizer, mine drainage, resource extraction, water softeners, saltwater intrusion, and evaporative concentration of ions due to hydrologic alterations and climate change. The complex interrelationships between salt ions and chemical, biological, and geologic parameters and consequences on the natural, social, and built environment are called Freshwater Salinization Syndrome (FSS). Here, we provide a comprehensive overview of salinization issues (past, present, and future), and we investigate drivers and solutions. We analyze the expanding global magnitude and scope of FSS including its discovery in humid regions, connections to human-accelerated weathering and mobilization of ‘chemical cocktails.’ We also present data illustrating: (1) increasing trends in salt ion concentrations in some of the world’s major freshwaters, including critical drinking water supplies; (2) decreasing trends in nutrient concentrations in rivers due to regulations but increasing trends in salinization, which have been due to lack of adequate management and regulations; (3) regional trends in atmospheric deposition of salt ions and storage of salt ions in soils and groundwater, and (4) applications of specific conductance as a proxy for tracking sources and concentrations of groups of elements in freshwaters. We prioritize FSS research needs related to better understanding: (1) effects of saltwater intrusion on ecosystem processes, (2) potential health risks from groundwater contamination of home wells, (3) potential risks to clean and safe drinking water sources, (4) economic and safety impacts of infrastructure corrosion, (5) alteration of biodiversity and ecosystem functions, and (6) application of high-frequency sensors in state-of-the art monitoring and management. We evaluate management solutions using a watershed approach spanning air, land, and water to explore variations in sources, fate and transport of different salt ions (
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Abstract This work reports the process of sensor development, optimization, and characterization before the transition to on-body measurements can be made. Sensors using lactate oxidase as a sensing mechanism and tetrathiafulvalene as a mediator were optimized for sporting applications. Optimized sensors show linear range up to 24 mM lactate and sensitivity of 4.8
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Summary Concurrent osmotic and chaotropic stress make MgCl2‐rich brines extremely inhospitable environments. Understanding the limits of life in these brines is essential to the search for extraterrestrial life on contemporary and relict ocean worlds, like Mars, which could host similar environments. We sequenced environmental 16S rRNA genes and quantified microbial activity across a broad range of salinity and chaotropicity at a Mars‐analogue salt harvesting facility in Southern California, where seawater is evaporated in a series of ponds ranging from kosmotropic NaCl brines to highly chaotropic MgCl2brines. Within NaCl brines, we observed a proliferation of specialized halophilic Euryarchaeota, which corresponded closely with the dominant taxa found in salterns around the world. These communities were characterized by very slow growth rates and high biomass accumulation. As salinity and chaotropicity increased, we found that the MgCl2‐rich brines eventually exceeded the limits of microbial activity. We found evidence that exogenous genetic material is preserved in these chaotropic brines, producing an unexpected increase in diversity in the presumably sterile MgCl2‐saturated brines. Because of their high potential for biomarker preservation, chaotropic brines could therefore serve as repositories of genetic biomarkers from nearby environments (both on Earth and beyond) making them prime targets for future life‐detection missions.
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3389/fenvs.2023.1020914
