Road Salt Application Research Articles

Use of a Storm water Retention System for Conservation of Regionally Endangered Fishes

ABSTRACTMaintaining aquatic biodiversity in urban or suburban areas can be problematic because urban landscapes can be nearly devoid of aquatic habitats other than engineered basins for storm water management. These areas are usually of questionable value for fish, but we examined a case study in which five regionally imperiled fish species were reintroduced into an artificial storm water detention pond and subsequently thrived. Although not a formal experiment, postintroduction survey data suggested that three of the five species maintained high population densities for 10 years after initial stocking, and two persisted in lower numbers. Success was likely due to a combination of unique design features and prior habitat preparation that resulted in clear water conditions that supported dense vegetation. Stocked fish persisted despite occasional bouts of low dissolved oxygen and increased chloride levels resulting from road salt application within the watershed. Transplanted fish served as a source population for both research and further reintroduction experiments. We suggest that, for some fish species, habitat preservation has a middle ground between natural habitats and completely artificial environments that require constant husbandry and that storm water systems could be used to create engineered sanctuaries within the human landscape that have many potential benefits for both humans and fish.

Simple Model of Changes in Stream Chloride Levels Attributable to Road Salt Applications

Increasing stream chloride ( Cl- ) concentrations have been observed over the last several decades in regions that receive regular road salt. In many cases, these increases occur even when road salt application has remained nearly constant, indicating the presence of multiyear attenuation within watersheds. This paper presents a simple mixing model to interpret the relationship between Cl- inputs and Cl- in stream discharge. The model was applied to data collected between 1972 and 2003 from Fall Creek in central New York, and the results indicate that stream salt concentrations may continue to increase for several decades. The estimated average residence time of road salt in the watershed was approximately 50 years, although the uncertainty in road salt application history suggests residence times of 40–70 years are reasonable. Hydrologists may be able interpret historical road salt applications and stream salt responses as essentially a regional tracer experiment to gain insights into macroscale watershe...

Increasing chloride concentrations in Lake Simcoe and its tributaries

Chloride concentrations in Lake Simcoe have increased significantly (P < 0.001) over a 36-year period during which the human population in the watershed has grown. Lake concentrations are now between 36 and 40 mg/L, having increased more than three-fold at the lake's outflow since 1971. Concentrations increased significantly in eight tributaries of the lake from 1993 to 2007 (P < 0.05), and were highest in those rivers draining the greatest percentage of urban land and roads, and in a river close to a major highway. The cumulative chloride load estimated at the mouths of seven rivers flowing into Lake Simcoe ranged from 11,563 to 32,107 tonnes/year from 1998 to 2007, and increased significantly over this period (P < 0.05). The fluxes or unit area loads of chloride, averaged from 2004 to 2007 for each of 10 tributaries, were positively correlated with the proportion of urban land and roads drained (P = 0.005, r = 0.80). Although Lake Simcoe is a large lake and only 12% of its watershed drains urban land and roads, evidence of road salt application can already be seen. This indicates that inputs must be reduced to preclude future ecological impacts on the lake.

Review of approaches to reducing adverse impacts of road deicing on groundwater in Finland

An increase in groundwater chloride concentrations was first reported 20 years ago in Finland. This discovery coincided with a sharp rise in the rate of road-salt application – the annual amount of NaCl consumed had increased from 50 t a−1 in the late 1970s to 140 t a−1 10 years later. To reverse these trends, research and development projects aimed at the reduced application of sodium chloride and improved protection of valuable groundwater resources were initiated. Several innovations, methods and practices, including the use of brine and pre-wetting, preventive anti-icing, advanced devices for salt spreading, utilization of meteorological online data and rewarding the private contractors for accurate, timely and scarce anti- and deicing, has resulted in a decline of 35% in the amount of salt applied since the early 1990s. Research on the fate and behavior of road salt in groundwater aquifers, predictions of future chloride concentrations and risk assessment have guided the risk management actions taken. Campaigns with reduced salting, use of geomembranes and recent progress on alternative deicing agents provide attractive options for further work towards sound deicing at valuable groundwater areas.

Road Salt Application in Highland Creek Watershed, Toronto, Ontario - Chloride Mass Balance

Abstract Occurrence of increasing chloride concentrations in urban streams of cold climates, mainly due to road salt application, has raised concerns on its adverse effects on aquatic and terrestrial ecosystems. Therefore, there is a need for a better understanding of processes associated with road salt application and subsequent discharge into the environment in order to develop management practices to minimize detrimental effects of chlorides. The chloride mass analysis for the Highland Creek watershed based on four years of hourly monitoring data indicates that approximately 60% of the chlorides applied on the watershed enter streams prior to subsequent salting period, 85% of which occurs during the period between November and March. Contribution of private de-icing operations on chloride mass input within Highland Creek watershed was estimated to be approximately 38%, indicating its significance in overall chloride mass balance. Salt application rates, as well as chloride output in the streams, vary spatially based on land use, influencing chloride concentrations in surface waters. The estimated groundwater chloride concentration of 275 mg/L indicates that some aquatic organisms in Highland Creek would potentially be at risk even outside the winter period under dry weather flow conditions.

Effects of road-deicing salt (NaCl) and saline water on water quality in the Urmia area, northwest of Iran

Increased application of road salt for winter maintenance has resulted in increased concentration of deicer constituents in the environment. The runoffs from the deicing operation have a deteriorating effect on water quality. The existence of salt super saturated Urmia lake and easy access to it, causes Urmia municipality to over use the super saturated water of this lake and salt (NaCl) during winter for snow melting, freezing prevention and traffic load facilitation. The aim of this study was investigation of surface and groundwater contaminations in consequence of salt (NaCl) and saline water usage in Urmia city and its surroundings. Studying the chloride ion concentration as a tracer in runoff result snowmelts during winter shows that its amount is differential with respect to time and place sampling. Results indicate that runoff result of snowmelts effected groundwater, soil and plant growth. The contamination of groundwater in study area by road salt and saline water is a slow process and directly related to the amount of road salt and saline water applied.

Concentration trends and water-level fluctuations at underground storage tank sites

Concentration trends of monitor wells utilized in monitored natural attenuation at petroleum underground storage tank sites can be used to predict achievement of regulatory standards if the data approximate a first-order decline trend. However, declining concentration trends often display seasonal and other fluctuations that complicate trend interpretation. Seasonal correlations between concentration and water-level elevation, including in-phase and inverse relationships, constitute one of the most common types of variation. The in-phase fluctuations are most common for monitor wells located in or near the source area of the release. This relationship may be the result of increased contact with the smear zone in the source area during periods of high water table. Conversely, inverse trends of water-level elevation and concentration are most common in downgradient wells beyond the limit of the source area. In a year long study of short-term fluctuations in BTEX and other parameters in a downgradient monitor well, the data suggest that the winter/spring recharge event significantly controls the concentration trends of BTEX as well as inorganic compounds in the well. Recharge and associated water table rise began in late fall and were soon followed by a slug of inorganic ions strongly influenced by road salt application. This slug of recharge diluted the concentrations of petroleum compounds and alkalinity (bicarbonate). Electron acceptors including oxygen, nitrate, and sulfate, which is a component of road salt, are also contributed to the water table during recharge. Oxygen and nitrate were not detected in the monitor well samples and were most likely consumed quickly in biodegradation reactions at the top of the contaminant plume. Sulfate peaked during winter/spring recharge and then slowly declined during the summer and fall, along with redox potential. Alkalinity (bicarbonate) increased during this period, which may represent the coupled oxidation of organic carbon to CO2 with sulfate as the electron acceptor. BTEX concentrations peaked in the fall probably due to the lack of diluting recharge. The slow changes in concentration over the summer and fall months, interpreted to be caused by biodegradation, contrast with the rapid changes associated with dilution during the recharge event.

Effect of Road Salt Application on Seasonal Chloride Concentrations and Toxicity in South‐Central Indiana Streams

Contemporary information on road salt runoff is needed for management of water resources in regions experiencing urbanization and increased road density. We investigated seasonal Cl(-) concentrations among five streams in south-central Indiana that drained watersheds varying in degree of urbanization and ranging in size from 9.3 to 27 km(2). We also conducted acute toxicity tests with Daphnia pulex to assess the potential effects of the observed Cl(-) concentrations on aquatic life. Periods of elevated Cl(-) concentrations were observed during the winters of 2007-08 and 2008-09 at all sites except the reference site. The highest Cl(-) concentration observed during the study was 2100 mg L(-1) and occurred at the most urbanized site. The Cl(-) concentration at the reference site never exceeded 22 mg L(-1). The application of road salt caused large increases in stream Cl(-) concentrations, but the elevated Cl(-) levels did not appear to be a significant threat to aquatic life based on our toxicity testing. Only the most urbanized site showed evidence of salt retention within the watershed, whereas the other sites exported the road salt relatively quickly after its application, suggesting storm drains and impervious surfaces minimized interaction between soils and salt-laden runoff. During winter at these sites, the response in stream Cl(-) concentrations appeared to be controlled by the timing and intensity of road salt application, the magnitude of precipitation, and the occurrence of air temperatures that caused snowmelt and generated runoff.

Projections of Chloride Concentrations in Urban Lakes Receiving Road De-icing Salt

The chloride concentrations of urban lakes where road de-icing salt (NaCl) is used have increased to levels that can change natural lake-mixing behavior and influence aquatic life. A zero-dimensional model was formulated to project the long-term accumulation of chloride in urban lakes receiving runoff from roads on which road salt is applied. Four model parameters and an initial concentration were obtained by calibrating the model with 5 years (2004-2008) of monthly salinity data from seven lakes in the Minneapolis/St. Paul Twin Cities Metropolitan Area of Minnesota, USA. Three of the seven lakes appear headed towards year-round volume averaged chloride concentrations above the 230-mg/L chronic standard for impairment to aquatic habitat. The two lakes with the lowest projected equilibrium concentrations of chloride have already reached equilibrium. One lake is projected to take an additional 40 years to reach equilibrium under current climate conditions and current road salt application rates. If road salt application rates are reduced in future winters, it is projected that the lakes will respond with noticeably lower chloride concentrations within 5 to 10 years. If road salt applications are discontinued altogether, chloride concentrations are projected to drop to natural levels within 10 to 30 years in all seven lakes. A reduction of application rates by 50% would result in annual volumetric average chloride concentrations below the chronic standard.

Stream Chloride Monitoring Program of City of Toronto: Implications of Road Salt Application

Abstract In cold regions, winter road safety is a major challenge for municipalities and provincial highway transportation agencies. Road salt is widely used to improve winter road conditions, but concerns have been raised about the effects of road salts on the environment. This paper describes a water quality monitoring program designed to measure both background chloride concentrations and the effects of road salt application on stream water quality in four watersheds (Humber River, Don River, Highland Creek, and Morningside tributary of Rouge River) located within the City of Toronto boundary. The effect of road salts on stream water quality was evaluated based on chloride concentration because of its conservative nature. A bilinear correlation was developed to transform measured specific conductance levels in stream water to chloride concentrations. There are no Ontario aquatic fresh water quality guidelines for chloride, but chloride concentrations in almost all the monitored streams in Toronto periodically exceeded chronic and acute chloride threshold levels of the United States Environmental Protection Agency. The City of Toronto has been proactive in its efforts to implement management practices to reduce the impact of road salt application on the environment while maintaining safe driving conditions for its road users. Normalized salt application rates in Toronto have been on a gradual declining trend in the last decade from about 0.08 to 0.07 tonnes of salt applied per centimetre of snowfall per kilometre of lane. With public safety in mind, further reductions in salt application rates are being considered to reduce the adverse environmental effects to acceptable limits.

Characterization of chloride transport in the unsaturated zone near salted road

The application of road salts as deicing agents contributes to the anthropogenic loading of chloride (Cl−) on the environment. Using a 2D solute model, the potential of the unsaturated zone to serve as a reservoir and the mechanisms controlling the movement of Cl− were examined. Physical properties and initial pore-water Cl− concentrations were derived from an array of soil borings. Initial pore-water concentrations show the presence of a Cl− “slug” approximately 0.75 m below the surface. Simulations show that within the unsaturated zone, Cl− transport is predominantly vertical, driven by molecular diffusion. After a 1-year simulation, a Cl− slug similar to the background observation was noted. While Cl− is retained in the unsaturated zone, a net loss of Cl− from the unsaturated zone was simulated for the first 10 years. In year 11, an equilibrium between the Cl− input and output is achieved. The presence of Cl− in the unsaturated zone becomes a long-term source of chloride to the groundwater, which eventually discharges into the surface water. Historically, surface water chemistry data support the continual discharge of chloride to the surface water in the area, further supporting the hypothesis that the unsaturated zone serves as a Cl− reservoir.

Increase of urban lake salinity by road deicing salt

Over 317,000 tonnes of road salt (NaCl) are applied annually for road deicing in the Twin Cities Metropolitan Area (TCMA) of Minnesota. Although road salt is applied to increase driving safety, this practice influences environmental water quality. Thirteen lakes in the TCMA were studied over 46 months to determine if and how they respond to the seasonal applications of road salt. Sodium and chloride concentrations in these lakes were 10 and 25 times higher, respectively, than in other non-urban lakes in the region. Seasonal salinity/chloride cycles in the lakes were correlated with road salt applications: High concentrations in the winter and spring, especially near the bottom of the lakes, were followed by lower concentrations in the summer and fall due to flushing of the lakes by rainfall runoff. The seasonal salt storage/flushing rates for individual lakes were derived from volume-weighted average chloride concentration time series. The rate ranged from 9 to 55% of a lake's minimum salt content. In some of the lakes studied salt concentrations were high enough to stop spring turnover preventing oxygen from reaching the benthic sediments. Concentrations above the sediments were also high enough to induce convective mixing of the saline water into the sediment pore water. A regional analysis of historical water quality records of 38 lakes in the TCMA showed increases in lake salinity from 1984 to 2005 that were highly correlated with the amount of rock salt purchased by the State of Minnesota. Chloride concentrations in individual lakes were positively correlated with the percent of impervious surfaces in the watershed and inversely with lake volume. Taken together, the results show a continuing degradation of the water quality of urban lakes due to application of NaCl in their watersheds.

IMPACTS OF ROAD DEICING SALT ON THE DEMOGRAPHY OF VERNAL POOL-BREEDING AMPHIBIANS

Deicing agents, primarily road salt, are applied to roads in 26 states in the United States and in a number of European countries, yet the scale of impacts of road salt on aquatic organisms remains largely under-studied. The issue is germane to amphibian conservation because both adult and larval amphibians are known to be particularly sensitive to changes in their osmolar environments. In this study, we combined survey, experimental, and demographic modeling approaches to evaluate the possible effects of road salt on two common vernal-pond-breeding amphibian species, the spotted salamander (Ambystoma maculatum) and the wood frog (Rana sylvatica). We found that in the Adirondack Mountain Region of New York (USA), road salt traveled up to 172 m from the highway into wetlands. Surveys showed that egg mass densities of spotted salamanders (A. maculatum) and wood frogs (R. sylvatica) were two times higher in forest pools than roadside pools, but this pattern was better explained by road proximity than by increased salinity. Experiments demonstrated that embryonic and larval survival were reduced at moderate (500 muS) and high conductivities (3000 muS) in A. maculatum and at high conductivities in R. sylvatica. Demographic models suggest that such egg and larval stage effects of salt may have important impacts on populations near roads, particularly in the case of A. maculatum, for which salt exposure may lead to local extinction. For both species, the effect of road salt was dependent upon the strength of larval density dependence and declined rapidly with distance from the roadside, with the greatest negative effects being limited to within 50 m. Based on this evidence, we argue that efforts to protect local populations of A. maculatum and R. sylvatica in roadside wetlands should, in part, be aimed at reducing application of road salt near wetlands with high conductivity levels.

Anthropogenically Driven Changes in Chloride Complicate Interpretation of Base Cation Trends in Lakes Recovering from Acidic Deposition

Declines in Ca and Mg in low ANC lakes recovering from acidic deposition are widespread across the northern hemisphere. We report overall increases between 1984 and 2004 in the concentrations of Ca + Mg and Cl in lakes representing the statistical population of nearly 4000 low ANC lakes in the northeast U.S. Increases in Cl occurred in nearly all lakes in urbanized southern New England, but only 18% of lakes in more remote Maine had Cl increases. This spatial pattern implicates road salt application as the major source of the increased Cl salts. Among the 48% of the lake population classified as salt-affected, the median changes in Cl (+133 microeq/L) and Ca + Mg (+47 microeq/ L) were large and positive in direction over the 20 years. However, in the unaffected lakes, Cl remained stable and Ca + Mg decreased (-3 microeq/L), consistent with reported long-term trends in base cations of acid-sensitive lakes. This discrepancy between the Cl groups suggests that changes in ion exchange processes in salt-affected watersheds have altered the geochemical cycling of Ca and Mg. One policy-relevant implication is that waters influenced by Cl salts complicate regional assessments of surface water recovery from "acid rain" related to the passage of the Clean Air Act.

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.

Elevated NH3 and NO2 air concentrations and nitrogen deposition rates in the vicinity of a highway in Southern Bavaria

Abstract A transect study consisting of air concentration and deposition measurements of nitrogen compounds was performed to estimate the potential influence of car emissions on the nitrogen input to ecosystems. Therefore, two transects each consisting of 4 plots, the first in a coniferous forest and the second one in an extensively farmed grassland, were installed perpendicular to a highway south of Munich (Bavaria). Both profiles were influenced mainly by car emissions and showed only small local influences caused by agricultural activities. In the framework of a pilot study based upon denuder measurements we found a strong temporal dependency of both nitrogen dioxide (NO2) and ammonia (NH3) concentrations on traffic density. In the main study air concentrations of NO2 and NH3 were measured by passive samplers; they used as the basis for the estimation of dry deposition. These estimations have been compared with the results of analyses from simultaneously conducted canopy throughfall deposition and open air bulk measurements of nitrate (NO3−) and ammonium (NH4+). Additionally, within the forest transect the variety of different soil vegetation species was recorded and quantified. We obtained a strong gradient of gas concentrations along both profiles. Whereas the bulk deposition remained quite constant along the non-forested transect, the nitrogen throughfall deposition rate diminished substantially with the distance from the highway. The deposition rate at the forest edge was twice of that inside. The nitrogen load estimated for the examined forest in the vicinity of the highway was comparable to other forest ecosystems situated near diffuse emission sources from agriculture. It could be shown that changes in soil composition and soil vegetation along the forest transect are caused by decreasing nitrogen deposition with distance from the highway. The application of road salt in winter leads to further impacts.

Long-term trends in sodium and chloride in the Mohawk River, New York: the effect of fifty years of road-salt application

Ecological studies have demonstrated the adverse effects of road-salt, primarily NaCl, on water quality, flora, and fauna. In this study, we quantified changes in ionic composition and solute flux of water draining the Mohawk River Basin (9103 km 2) in New York State, from 1952 to 1998. Using various statistical, graphical, and modeling techniques, we showed that concentrations of Na + and Cl − have increased by 130 and 243%, respectively, while other constituents have decreased or remained constant. The use of de-icing salt on roads within the watershed, which we estimate at 39 kg km −2 day −1, appears to be the primary mechanism responsible for reported increases, accounting for the increase in NaCl export from 16 to 46 kg km −2 day −1 over the 47-year period. Moreover, despite population decline within this rural upstate watershed, increased environmental stewardship, and The Clean Water Act, concentrations of Na + and Cl − still increased during the 1990s.

Evaluation of Methods for High-Speed Application of Road Salt

The operating speed for applying rock salt with conventional spreaders is limited by material loss caused by bouncing or sliding across the pavement. This results in excess salt loss to the roadside environment, traffic congestion during winter operations, and unnecessarily long spreading cycle times. Equipment designed to control the velocity at which material hits the pavement and to prewet winter materials has been developed to solve these problems. Tests were undertaken to examine the feasibility of high-speed material application on bare pavement by using traditional and newly developed methods and equipment. The study included measurement of spread patterns and material loss against operating speeds using ground-speed spreaders and using prewet materials, in comparison with conventional methods. Ground-speed spreaders and prewetting are recommended to permit high-speed spreading of salt in a windrow pattern on bare pavement.

Eutrophication of gravel pit lakes which are situated in close vicinity to the river Donau: Water and nutrient transport

From the end of the 1970's until the end of the 1990's, the eutrophication process in six gravel pit lakes situated near to the dammed river Donau, was studied. The gravel pits were dredged between 1956 and 1972. Water levels in the river were over 2 m higher than in the lakes and this resulted in considerable hydraulic pressure from the river to the lakes and, therefore, infiltration of nutrient rich water into the lakes. At the end of the 1970's the total phosphorus concentrations showed a trend with lake I having the highest and lake VI the lowest concentration. Lake I was hypertrophic, lake II eutrophic and lakes III to VI were meso- to eutrophic. This trend can be explained by the infiltration pattern: infiltration was greatest at, and upstream of lake I, and lower downstream and in the other lakes as they were shielded by a concrete barrier. In the 1990's the level of eutrophication in lakes I and II decreased because the phosphorus loads in the river decreased. The level of eutrophication in the other lakes stayed constant or slightly increased in this time due to ageing. The water level in the lakes increased in the course of the years, probably due to the lake bottom and sides becoming more tightly sealed from the sedimentation of autochthonous material. Chloride concentrations in the lakes and the surrounding water were high compared to natural conditions. Chloride concentrations in lake VI increased considerably in the course of the three decades. A drainage ditch runs through this lake. The increase of chloride concentration in this lake probably results from the long term application of road salts during snowy or icy periods, which get washed off roads into the surrounding groundwater and surface water.

Road salt contamination of groundwater in a major metropolitan area and development of a biological index to monitor its impact

A survey of 23 springs in the Greater Toronto Area (GTA) of southern Ontario recorded chloride contamination levels, resulting from the winter application of road de-icing salt, ranging from <2 to >1200 mg l −1. Chloride level measured in spring water was far more seasonally stable than that measured in surface (river) water, and thus the spatial pattern of Cl contamination indicated by the former was judged to be more reliable. Chloride contamination of groundwater in the GTA was strongly related to urbanisation, and at the four most affected springs increases of between 21 and 34% were detected over the period November 1996 to November 1997. The response of macroinvertebrates living in these springs to increasing salinity was examined with the aim of creating a biological index of contamination: the Chloride Contamination Index (CCI). A power function yielded a significant correlation between this index and the mean Cl concentration measured at each spring. Taxa were able to be categorised as either “tolerant” or “non-tolerant” of high Cl although none was unique to either end of the scale. However, from both field observations and salinity tolerance trials in the laboratory, the amphipod Gammarus pseudolimnaeus was found to be associated with source aquifers only mildly contaminated with Cl. Absence of this species from a spring, particularly if nymphs of the stonefly Nemoura trispinosa are present should indicate moderate to high contamination.