Use Of Road Salt Research Articles

Halotolerance in the Southeastern Michigan Soil Microbiome

Many communities in the Midwest and Northeastern United States use salt to treat icy roads in the winter. Studies have shown that the many years of salt application have had harmful effects on freshwater ecosystems, roadside flora and fauna, and overall wetland biomes. We were interested in investigating the impact that road salt use has had on the soil microbiome. Specifically, we sought to determine if microbes that reside near salted roads have become more tolerant of salt, or more halotolerant, than microbes that reside far from roads. We accomplished this by first collecting soil samples from near roads (exposed to road salt) and far from roads (not exposed to road salt) from various parks across Southeastern Michigan. Salinity measurements were taken by mixing 1 g soil per 1 mL distilled water. We then used these soil samples to compare the number of colony forming units on 5% NaCl nutrient agar plates and standard nutrient agar plates, investigate growth rate differences between these microbes in 5% NaCl nutrient broth, and sequence various salt intolerant, halotolerant, and halophilic microbes. This allowed us to uncover relationships between the soil salt concentrations, the microbiome distances from roads, and the halotolerance of the microbiomes, as well as to gain some insight into the microbiome population makeup. Preliminary data suggests that there may be a correlation between the salt concentration in soil (ppm) and the overall soil microbiome halotolerance. This indicates that microbiomes closer to roads (which we have shown to have greater soil salt concentration) are likely more halotolerant than microbiomes further from roads (which we have shown to have lesser soil salt concentration). We will investigate the growth rate differences between halotolerant and nonhalotolerant strains as well as determine the genus of the microbes to provide further insight into the composition of the microbiome. This study suggests that the application of road salt is not only affecting wetland biomes but may also be having an effect on the soil microbiome as well.Support or Funding InformationSpecial thanks to Lawrence Technological University for laboratory space, equipment, and funding to carry out this study.

Comparison of Contributions to Chloride in Urban Stormwater from Winter Brine and Rock Salt Application.

The use of road salt to increase roadway safety during winter storms releases high concentrations of chloride into urban and suburban stormwater. This stormwater flows into nearby streams, resulting in concentrations of chloride that can exceed water quality standards intended to protect aquatic life. As chloride pollution is not readily filtered by soil or plants, mitigation will require reductions in the amount of salt used. In this study, cities in St. Louis County, Missouri, U.S., were used as a test case for brining as a best management practice (BMP) to reduce salt use relative to the standard practice of spreading solid rock salt. The practice of brining involves the dissolution of road salt in water and the application of the resulting brine solution to roadways in advance of a forecasted winter storm. During the winters of 2016-2017 and 2017-2018, stormwater runoff from residential areas was monitored in paired cities to determine if the availability of brining as a BMP for salt application on residential roads would result in a decrease in chloride in stormwater and, therefore, a decrease in chloride reaching urban streams. The use of brining by city governments resulted in a 45% average reduction of chloride loads conveyed to streams, demonstrating that brining is a highly viable BMP for local municipal operations.

Seasonal and Long-Term Dynamics in Stream Water Sodium Chloride Concentrations and the Effectiveness of Road Salt Best Management Practices

We use a 32-year dataset from a rural, southeastern New York stream to describe the effect of long-term road salt use on concentrations of sodium (Na+) and chloride (Cl−). Mean annual stream Na+ and Cl− concentrations initially increased, reached a plateau, and then increased again. Trends in summer and winter stream concentrations were similar but summer concentrations were higher than winter, indicating that salt entered the stream via groundwater discharge. Seasonal and inter-annual variability in stream Na+ and Cl− concentrations and export were high in the latter years of the study and can be explained by increased variability in stream discharge. Stream water Na+ and Cl− concentrations were positively correlated with conductivity, and conductivity was negatively correlated with discharge during all seasons (p < 0.001). We used road salt application data from a local agency to examine effects of best management practices. Despite reductions in salt application, there was no commensurate decrease in stream water Na+ and Cl− concentrations. We estimate that the legacy of long-term salt accumulation in groundwater and soils may delay a decline in stream water Na+ and Cl− concentrations by 20–30 years. Continued research to develop road salt reduction practices is important to mitigate impacts on freshwater ecosystems and drinking water supplies.

Impact of Road Salt on Drinking Water Quality and Infrastructure Corrosion in Private Wells.

Increased road salt use and resulting source water contamination has widespread implications for corrosion of drinking water infrastructure, including chloride acceleration of galvanic corrosion and other premature plumbing failures. In this study, we utilized citizen science sampling, bench-scale corrosion studies, and state-level spatial modeling to examine the potential extent of chloride concentrations in groundwater and the resulting impact on private wells in New York. Across the sampled community, chloride levels varied spatially, with the highest levels in private wells downgradient of a road salt storage facility followed by wells within 30 m of a major roadway. Most well users surveyed (70%) had stopped drinking their well water for aesthetic and safety reasons. In the bench-scale experiment, increasing chloride concentration in water increased galvanic corrosion and dezincification of plumbing materials, resulting in increased metal leaching and pipe wall thinning. Our simple spatial analysis suggests that 2% of private wellusers in New York could potentially be impacted by road salt storage facilities and 24% could potentially be impacted by road salt application. Our research underscores the need to include the damage to public and privately owned drinking water infrastructure in future discussion of road salt management.

Investigation of phyco-remediation of road salt run-off with marine microalgae Nannochloropsis gaditana

ABSTRACTPhyco-remediation is an environmental-friendly method, which involves the application of beneficial microalgae to treat wastewater-containing pollutants for a diverse range of conditions. Several industrial processes generate hyper saline wastewater, which is a significant challenge for conventional wastewater treatment, and the disposal of saline waters also has a negative impact on the environment. Road salt run-off is one such saline wastewater stream not currently treated and one that contributes significantly to negatively impacting receiving bodies of water. In this study, Nannochloropsis microalgae were able to assimilate >95% of the nitrates within 8 days in road salt concentrations ranging from 2.6% to 4.4% under phototrophic cultivation mode. Biomass yields of 1–2 g/l of culture were obtained with the maximum lipid of 22% (g/g) biomass in the road salt media. The crude road salt media provided all the essential micronutrients needed for algal cultivation. The fatty acid composition analysis of the obtained lipid composed of C16 and C18 over 45% of FAME are suitable for biofuel. This study has established that the use of road salt containing nitrate and phosphate nutrients will support the growth of marine micro algae for remediation of a waste water system that are the concern at winter-prevalent regions.

PhragNet: crowdsourcing to investigate ecology and management of invasive Phragmites australis (common reed) in North America

Invasion biology research, often performed by scientists at relatively small spatial scales, provides experimental precision but may be limited in generalizability. Conversely, large-scale invasive species management represents a largely untapped wealth of information on invasion ecology and management, but such data are difficult to capture and synthesize. We developed a network (“PhragNet”) of individuals managing wetlands occupied by native and non-native lineages of the invasive wetland grass Phragmites australis (common reed). This network collected environmental and genetic samples, habitat data, and management information to identify environmental and plant community associations of Phragmites invasion and patterns of management responses. Fifty managers overseeing 209 Phragmites stands in 16 US states and ON, Canada participated. Participants represented federal agencies (26%), municipalities (20%), NGOs (20%), academia (14%), state agencies (12%), and private landowners (8%). Relative to the native lineage, non-native Phragmites occurred in areas with higher nitrate/nitrite and ammonium than non-native Phragmites. Stand interiors had higher soil electrical conductivity than nearby uninvaded areas, consistent with use of road salt promoting spread of Phragmites. Non-native Phragmites co-occurred with fewer plant species than native Phragmites and was actively targeted for management. Herbicide was applied to 51% of non-native stands; surprisingly, 11% of native stands were also treated with herbicide. This project demonstrates the utility of crowdsourcing standardized data from resource managers. We conclude by describing how this approach could be expanded into an adaptive management framework, strengthening connections between wetland management and research.

Temporal Variability of Heavy Metals in Suburban Road Runoff in a Rainy Cold Climate

Road runoff contains toxic heavy metals that can threaten the water quality of urban water systems. This paper characterizes the time variability of heavy metal pollution in road runoff in a 9 ha, steep (12% slope), suburban, rainy (235 rainy days; 1,120 mm per annum), cold climate catchment. Twenty-three water samples, collected during six discrete runoff events spanning 1 year, were analyzed for total and dissolved heavy metal concentrations. The most abundant pollutants were Zn (46 μg/L), Cu (14 μg/L), and Cr and Ni (2.3–2.5 μg/L). Zn, As and Cd were predominantly dissolved (>70%), Ni was primarily bound to particulates (68%), and Cu and Cr were equally divided between phases. Elevated dissolved and total concentrations were measured during snowmelt in correlation with high electrical conductance reflecting the use of road salt as a deicing agent. Event mean concentrations were positively correlated to wind speed and negatively correlated to rainfall depth in the two antecedent weeks. A mild first flush of dissolved metals was observed in most events, with 40–50% of pollution mass being discharged in the first 30% of runoff volume. Particulate-bound heavy metals, however, only exhibited first flush during intensive snowmelt. A strong linear correlation was observed between particulate-bound heavy metals and total suspended solids (TSS) (R²=0.8–0.9), corresponding to 0.45, 0.22, 0.05, and 0.06 μg/mg TSS slope for Zn, Cu, Cr, and Ni, respectively. Overall, the pollution levels were moderate compared with residential catchments in northern Europe and North America, which may constrain runoff treatment efficiency.

Ecological benefit of the road salt code of practice

Despite an overall increase in total road salt used over the past 14 years (the data record in this manuscript), there has been a 26% reduction in the rate (normalized as tonnes of salt per cm of snow per km of road) of road salt application by the City of Toronto since that city implemented mitigations from the Road Salt Code of Practice. The ecological benefit of the reduced use of road salt was approximated by comparing the estimated 26% salt reduction to the distribution of chloride tolerances that has been recently published by the Canadian Council of Ministers of the Environment (i.e., CCME). Species sensitivity distributions predict that between 1 and 14% of taxa would benefit from a 26% reduction in chloride concentrations in surface waters. Assuming that a typical ‘healthy’ Canadian watercourse might support between 100 and 200 species of fish, invertebrates and plants, the Code of Practice might provide benefit to between 14 and 28 species. However, the net ecological benefit of implementing the Code may be undermined in rapidly urbanizing watersheds where road networks continue to expand at a rate of 3–5% per year and chloride loads to urban streams are steadily increasing.

Road Salt Use and Groundwater Quality: An Empirical Study

Road Salt Use and Groundwater Quality: An Empirical Study

Stream Conductivity: Relationships to Land Use, Chloride, and Fishes in Maryland Streams

AbstractStream conductivity reflects both landscape and anthropogenic interactions, although increasing chloride inputs from road salt in eastern North America is also important. Employing a spatially extensive database derived from the Maryland Biological Stream Survey (MBSS), we examined relationships of stream conductivity to landscape attributes and determined relationships between stream MBSS fish metrics, abundance, and biomass as well as fish assemblages by means of conductivity (as a chloride surrogate) to estimate potential effects. Background stream conductivity for the MBSS strata and Maryland L3 ecoregions ranged from 51 to 150 μS/cm, with the Piedmont having the highest background conductivity (145–160 μS/cm). For MBSS sites there were strong relationships of stream conductivity and chloride with both impervious surface and road density, and 0.26% of the MBSS sites exceeded the U.S. Environmental Protection Agency's acute chloride criterion and 1.5% the chronic chloride criterion. For the Maryland Piedmont species assemblage, observed conductivity values between 230 and 540 μS/cm caused important alterations in the biotic community as measured by the series of fish metrics, and thus affected fish species assemblages associated with chloride concentrations between 33 and 108 mg/L. Maryland coastal, coldwater, and highland species assemblages displayed variable responses of conductivity to fish metrics, abundance, and biomass. If regional conductivity and chloride levels continue to increase or remain high from road deicing owing to an increase in urbanization in a watershed or climatic changes, differences in stream fish assemblages and therefore fish diversity may become more apparent. Because of the linkage between salt usage and impervious road surfaces resulting from urbanization, it is important to manage effectively the use of road salt to protect biotic resources.Received January 24, 2012; accepted June 5, 2012

Warm season chloride concentrations in stream habitats of freshwater mussel species at risk

Warm season (May–October) chloride concentrations were assessed in stream habitats of freshwater mussel species at risk in southern Ontario, Canada. Significant increases in concentrations were observed at 96% of 24 long-term (1975–2009) monitoring sites. Concentrations were described as a function of road density indicating an anthropogenic source of chloride. Linear regression showed that 36% of the variation of concentrations was explained by road salt use by the provincial transportation ministry. Results suggest that long-term road salt use and retention is contributing to a gradual increase in baseline chloride concentrations in at risk mussel habitats. Exposure of sensitive mussel larvae (glochidia) to increasing chloride concentrations may affect recruitment to at risk mussel populations.

Acute effects of road salts and associated cyanide compounds on the early life stages of the unionid mussel Villosa iris

The toxicity of cyanide to the early life stages of freshwater mussels (order Unionida) has remained unexplored. Cyanide is known to be acutely toxic to other aquatic organisms. Cyanide-containing compounds, such as sodium ferrocyanide and ferric ferrocyanide, are commonly added to road deicing salts as anticaking agents. The purpose of the present study was to assess the acute toxicity of three cyanide compounds (sodium cyanide, sodium ferrocyanide, and ferric ferrocyanide), two road salts containing cyanide anticaking agents (Morton and Cargill brands), a brine deicing solution (Liquidow brand), and a reference salt (sodium chloride) on glochidia (larvae) and juveniles of the freshwater mussel Villosa iris. Sodium ferrocyanide and ferric ferrocyanide were not acutely toxic to glochidia and juvenile mussels at concentrations up to 1,000 mg/L and 100 mg/L, respectively. Lowest observed effect concentrations (LOECs) for these two chemicals ranged from 10 to >1,000 mg/L. Sodium cyanide was acutely toxic to juvenile mussels, with a 96-h median effective concentration (EC50) of 1.10 mg/L, although glochidia tolerated concentrations up to 10 mg/L. The EC50s for sodium chloride, Liquidow brine, Morton road salt, and Cargill road salt were not significantly different for tests within the same life stage and test duration (range, 1.66-4.92 g/L). These results indicate that cyanide-containing anticaking agents do not exacerbate the toxicity of road salts, but that the use of road salts and brine solutions for deicing or dust control on roads may warrant further investigation.

Environmental change in Lake Champlain revealed by long-term monitoring

Long-term monitoring data on Lake Champlain spanning the past two to five decades were analyzed to document water quality and biological changes in the lake. August mean surface water temperatures increased during 1964–2009 in most Lake Champlain regions at rates (0.035–0.085°C/year) similar to what has been observed in the Laurentian Great Lakes and elsewhere. Secchi disk transparency increased by over a meter during 1964–2009 in regions along the main stem of the lake, with much of the increase occurring after the 1993 zebra mussel invasion. Transparency declined in northeastern regions where zebra mussel densities were lower. No trends in hypolimnetic dissolved oxygen concentrations or depletion rates were found in any of the deep lake regions during 1990–2009. Sodium concentrations tripled in the Main Lake region since the 1960s. Chloride increased in the Main Lake by 30% since 1992, but declined in northeastern regions of the lake during recent years, coincident with reductions in road salt use in Vermont. Total phosphorus concentrations decreased during 1979–2009 in southern and northwestern lake regions, but increased by 72% in Missisquoi Bay where chlorophyll-a concentrations doubled over the period. There was a general lakewide trend of decreasing total nitrogen levels during 1992–2009 that may have been due in part to reductions in atmospheric nitrogen loading to the watershed. Cyanobacteria increased their dominance within the phytoplankton community in northeastern regions of the lake since the 1970s.

VARIATION OF ELEMENTAL COMPOSITION OF PARTICULATE MATTER BETWEEN AND WITHIN 20 STUDY AREAS IN EUROPE

Background and Aims: Recent research has indicated the importance of particulate matter (PM) composition on adverse health effects. Furthermore, knowledge of PM composition can be used to apportion pollution to its sources. In 20 study areas of the ESCAPE project, 2-week integrated PM sampling was conducted in 3 different seasons at 20 locations per area in 2008-2010. At the European level, these filters will reveal differences in elemental composition by city, season, size fraction, and site type; thereby, allowing potential determination of likely sources. Moreover, if elemental data can be spatially modelled, it can be linked with health data from cohort studies within ESCAPE. Methods: The filters from PM areas are being analyzed by x-ray fluorescence (XRF) to determine their elemental composition. Currently, a total of 1043 filters have been analyzed from the 1st year of sampling for 48 individual elements. As more analyses results are received and data are linked with filter information, trace element data will be examined by city, season, size fraction, and site type. We expect to observe groupings of correlated elements related to different sources; eg, traffic impacts reflected in Fe/Ba/Zn/Cu. Other aspects examined will include: mass contribution of elements to total PM; seasonal contributions of biomass burning (K) and road-salt use (NaCl). Results: An overview of all 950 analyzed sample filters, with an average mass of 535.5μg, shows an average elemental contribution of 14.2% of total mass. A correlation matrix of these filters already indicates several common groupings: Al/Si/Ca/Fe/Ti (crustal), Fe/Zn/Cu (traffic), Na/Cl (road/sea-salt). The strength of these correlations is currently buried by the aggregation of all filters. Conclusions: Examination of trace element composition of PM will reveal within and between area compositional differences over Europe, which may be associated with health effects. This is particularly notable as all the monitoring was done in a harmonized manner.

Assessing the toxicity of sodium chloride to the glochidia of freshwater mussels: Implications for salinization of surface waters

Chloride concentrations in surface waters have increased significantly, a rise attributed to road salt use. In Canada, this may be a concern for endangered freshwater mussels, many with ranges limited to southern Ontario, Canada’s most road-dense region. The acute toxicity of NaCl was determined for glochidia, the mussel’s larval stage. The 24 h EC50s of four (including two Canadian endangered) species ranged from 113–1430 mg Cl L −1 (reconstituted water, 100 mg CaCO 3 L −1). To determine how mussels would respond to a chloride pulse, natural river water (hardness 278–322 mg CaCO 3 L −1) was augmented with salt. Lampsilis fasciola glochidia were significantly less sensitive to salt in natural water (EC50s 1265–1559 mg Cl L −1) than in reconstituted water (EC50 285 mg L −1). Chloride data from mussel habitats revealed chloride reaches levels acutely toxic to glochidia (1300 mg L −1). The increased salinization of freshwater could negatively impact freshwater mussels, including numerous species at risk.

Salinization of urbanizing New Hampshire streams and groundwater: effects of road salt and hydrologic variability

Since the 1940s, use of road salt as a deicing agent has increased substantially in regions of the US with cold winters. Despite its ubiquitous application and known negative consequences for aquatic and human health, little research has documented the effects of road salt on the water quality of either streams or groundwater in regions, such as New Hampshire (NH), with harsh northern climates. We measured stream Na+ and Cl− concentrations in 44 basins spanning a gradient of urbanization in southeastern and central NH. Among all sampled basins, stream Na+ and Cl− concentrations were highly correlated with basin % road pavement (r2 = 0.75 for Na+, and 0.78 for Cl−). In southeastern NH, concentrations also were correlated strongly with % impervious surface (r2 = 0.86 for Na+, and 0.92 for Cl−). Groundwater salt concentrations in 143 private wells were significantly correlated with % impervious surface within a 500-m radius of each well, but the proportion of explained variance was small (r2 = 0.07 for Na+, and 0.10 for Cl−). Concentrations of salt in streams and groundwater were surprisingly high. Mean concentrations of Na+ ranged from <1 to 298 mg/L and of Cl− ranged from <1 to 573 mg/L. Mean Cl− concentration in 1 small stream exceeded the US Environmental Protection Agency (EPA) chronic toxicity standard of 230 mg/L, and 9% of groundwater samples exceeded the secondary EPA maximum contamination levels for drinking water (250 mg/L of either Na+ or Cl−). In our long-term study basin, the Lamprey River, specific conductance increased over the period from 1978 to 2008, a result that indicated a corresponding increase in Na+ and Cl− concentrations. Both Na+ and Cl− concentrations in the Lamprey River were negatively correlated with flow, but the slope of the relationship decreased after a significant flood in 2006. Our data suggest that road-salting practices are contributing to the salinization of stream water and groundwater in NH, and that hydrologic variability, which is predicted to increase with climate change, could strongly affect the degree of salinization observed in surface waters.

Effects of road salts on the composition of seasonal pond communities: can the use of road salts enhance mosquito recruitment?

Road deicing agents can enter nearby wetlands and alter the composition of aquatic communities by directly eliminating salt-intolerant species and modifying ecological interactions between tolerant species. We conducted field experiments to examine the sensitivity of taxa that inhabit seasonal wetlands and to determine whether salt contamination could increase the production of ovipositing insects. In two outdoor mesocosm experiments, cladocerans and copepods rarely survived concentrations of commercial road salt >1,200 mg L−1, while wood frog eggs and hatchlings (Lithobates sylvaticus) were not strongly impacted until concentrations exceeded 4,500 mg L−1. Shore flies (Ephydridae), mosquitoes (Culex restuans; Anopheles punctipennis) and midge larvae (Chironomidae) were more salt tolerant than macrozooplankton. These taxa tended to be absent or relatively rare in experimental mesocosms with low salinities, but abundant in mesocosms with intermediate to high salinities. We conducted two additional experiments to examine whether adult choice of oviposition sites may in part explain the rarity of Cx. restuans in pools with low salinity. These revealed that Cx. restuans reduced oviposition rates in water-filled containers with cladocerans, and reduced clutch size in the presence of Lithobates larvae. However, salt concentration per se did not influence the propensity of Cx. restuans to oviposit. Collectively, our results suggest that aquatic habitats that are biologically compromised by deicing agents favor salt-tolerant insects, and that the use of road salts could increase the production of adult mosquitoes that are pests and vectors of disease.

Long-Term Sodium Chloride Retention in a Rural Watershed: Legacy Effects of Road Salt on Streamwater Concentration

Sodium and chloride concentrations and export increased from 1986 to 2005 in a rural stream in southeastern New York. Concentrations increased 1.5 mg/L per year (chloride) and 0.9 mg/L per year (sodium), and export increased 33,000 kg/year (chloride) and 20,000 kg/year (sodium) during this period. We estimate that salt used for deicing accounted for 91% of the sodium chloride input to the watershed, while sewage and water softeners accounted for less than 10% of the input. Road salt use in the watershed did not increase during the study, but sodium and chloride from sewage and water softeners is likely to have increased slightly due to a small increase in population. Increased input from sewage and water softeners cannot account for the increase in concentration and export from the watershed. Model results suggest that the increase in streamwater concentration and export was likely due to a lag effect of long-term road salt use and subsurface buildup.

Road Salt Influence on Pollutant Releases from Melting Urban Snow

Abstract A snow-melting experiment was performed to study the effects of road salt on the melting of urban snow from a snow windrow (pile) along a road in central Luleå, Sweden. Two snow piles were formed in the laboratory, with and without road salt added, and melted under similar conditions. All meltwater was collected and analyzed. The purpose of the experiment was to study the influence of the use of de-icing salt on meltwater quality and the release of pollutants from urban snow. The study indicated that the use of road salt may increase the dissolved metal phase in the urban snow meltwater. Also, the salt seems to have the largest effect at the beginning of the melting period when chloride is leaving the snow pile. Of total chloride, 90% was transported with the first 20% of the meltwater. Concentrations of the particulate-bound metals showed a fairly constant rate of release at the start of melt, but increased rapidly towards the end of the melting period, and this was more pronounced in the case of snow containing high chloride concentrations. Overall, a larger transport of solids was found for the pile with salt due to faster melting. Significantly larger masses of suspended solids and two heavy metals (Cu and Zn) were released with the meltwater from the pile with salt in comparison with the no-salt pile. The rest of the suspended solids and heavy metals stayed in the solid residue remaining at the end of the experiment.

Effect of long-term changes in soil chemistry induced by road salt applications on N-transformations in roadside soils

Of several impacts of road salting on roadside soils, the potential disruption of the nitrogen cycle has been largely ignored. Therefore the fates of low-level ammonium-N and nitrate-N inputs to roadside soils impacted by salting over an extended period (decades) in the field have been studied. The use of road salts disrupts the proportional contributions of nitrate-N and ammonium-N to the mineral inorganic fraction of roadside soils. It is highly probable that the degree of salt exposure of the soil, in the longer term, controls the rates of key microbial N transformation processes, primarily by increasing soil pH. Additional influxes of ammonium-N to salt-impacted soils are rapidly nitrified therefore and, thereafter, increased leaching of nitrate-N to the local waterways occurs, which has particular relevance to the Water Framework Directive. The results reported are important when assessing the fate of inputs of ammonia to soils from atmospheric pollution.