Because of environmental and societal concerns, new strategies are being developed to mitigate the effects of road salt. These include new deicers that are alternatives to or mixtures with the most common road salt, sodium chloride (NaCl), improved techniques and equipment, and biotic mitigation methods. Using outdoor mesocosms, we investigated the impacts of NaCl and two common alternatives, magnesium chloride (MgCl₂) and calcium chloride (CaCl₂) on freshwater communities. We also investigated the mitigation ability of a common macrophyte, Elodea. We hypothesized that road salt exposure reduces filamentous algae, zooplankton, and macrocrustaceans, but results in increases in phytoplankton and gastropods. We also hypothesized that MgCl₂ is the most toxic salt to communities, followed by CaCl₂, and then NaCl. Lastly, we hypothesized that macrophytes mitigate some of the effects of road salt, specifically the effects on primary producers. We found that all three salts reduced filamentous algal biomass and amphipod abundance, but only MgCl₂ reduced Elodea biomass. MgCl₂ had the largest and longest lasting effects on zooplankton, specifically cladocerans and copepods, which resulted in a significant increase in phytoplankton and rotifers. CaCl₂ increased ostracods and decreased snail abundance, but NaCl increased snail abundance. Lastly, while we did not find many interactions between road salt and macrophyte treatments, macrophytes did counteract many of the salt effects on producers, leading to decreased phytoplankton, increased filamentous algae, and altered abiotic responses. Thus, at similar chloride concentrations, NaCl alternatives, specifically MgCl₂, are not safer for aquatic ecosystems and more research is needed to find safer road management strategies to protect freshwater ecosystems.

Road-side aquatic ecosystems in North America are annually polluted with millions of tons of road deicing salts, which threaten the survival of amphibians which live and breed in these habitats. While much is known of the effects of NaCl, little is known of the second most-commonly used deicer, MgCl2, which is now used exclusively in parts of the continent. Here we report that environmentally relevant concentrations of both NaCl and MgCl2 cause increased incidence of developmental deformities in rough-skinned newt hatchlings that developed embryonically in these salts. In addition, we provide some of the first quantification of severity of different deformities, and reveal that increased salt concentrations increase both deformity frequency and severity. Our work contributes to the growing body of literature that suggests salamanders and newts are particularly vulnerable to salt, and that the emerging pollutant, MgCl2 is comparable in its effects to the more traditionally-used NaCl.

The application of road deicing salts has led to the salinization of freshwater ecosystems in northern regions worldwide. Increased chloride concentrations in lakes, streams, ponds, and wetlands may negatively affect freshwater biota, potentially threatening ecosystem services. In an effort to reduce the effects of road salt, operators have increased the use of salt alternatives, yet we lack an understanding of how these deicers affect aquatic communities. We examined the direct and indirect effects of the most commonly used road salt (NaCl) and a proprietary salt mixture (NaCl, KCl, MgCl2), at three environmentally relevant concentrations (150, 470, and 780 mg Cl−/L) on freshwater wetland communities in combination with one of three biotic stressors (control, predator cues, and competitors). The communities contained periphyton, phytoplankton, zooplankton, and two tadpole species (American toads, Anaxyrus americanus; wood frogs, Lithobates sylvaticus). Overall, we found the two road salts did not interact with the natural stressors. Both salts decreased pH and reduced zooplankton abundance. The strong decrease in zooplankton abundance in the highest NaCl concentration caused a trophic cascade that resulted in increased phytoplankton abundance. The highest NaCl concentration also reduced toad activity. For the biotic stressors, predatory stress decreased whereas competitive stress increased the activity of both tadpole species. Wood frog survival, time to metamorphosis, and mass at metamorphosis all decreased under competitive stress whereas toad time to metamorphosis increased and mass at metamorphosis decreased. Road salts and biotic stressors can both affect freshwater communities, but their effects are not interactive.

The use of road deicing salts in regions that experience cold winters is increasing the salinity of freshwater ecosystems, which threatens freshwater resources. Yet, the impacts of environmentally relevant road salt concentrations on freshwater organisms are not well understood, particularly in stream ecosystems where salinization is most severe. We tested the impacts of deicing salts—sodium chloride (NaCl), magnesium chloride (MgCl2), and calcium chloride (CaCl2)—on the growth and development of newly hatched rainbow trout (Oncorhynchus mykiss). We exposed rainbow trout to a wide range of environmentally relevant chloride concentrations (25, 230, 860, 1500, and 3000 mg Cl− L−1) over an ecologically relevant time period (25 d). We found that the deicing salts studied had distinct effects. MgCl2 did not affect rainbow trout growth at any concentration. NaCl had no effects at the lowest three concentrations, but rainbow trout length was reduced by 9% and mass by 27% at 3000 mg Cl− L−1. CaCl2 affected rainbow trout growth at 860 mg Cl− L−1 (5% reduced length; 16% reduced mass) and these effects became larger at higher concentrations (11% reduced length; 31% reduced mass). None of the deicing salts affected rainbow trout development. At sub-lethal and environmentally relevant concentrations, our results do not support the paradigm that MgCl2 is the most toxic deicing salt to fish, perhaps due to hydration effects on the Mg2+ cation. Our results do suggest different pathways for lethal and sub-lethal effects of road salts. Scaled to the population level, the reduced growth caused by NaCl and CaCl2 at critical early-life stages has the potential to negatively affect salmonid recruitment and population dynamics. Our findings have implications for environmental policy and management strategies that aim to reduce the impacts of salinization on freshwater organisms.

Uranium wastewater treatment has been performed by adsorption method using Mg(OH)₂-impregnated activated carbon. Research purposes are to determine (i) uptake capacity of the adsorption isotherm of uranium in Mg(OH)₂-impregnated activated carbon, (ii) mathematical correlation of uranium (VI) adsorption rate, and (iii) effect of the impregnation ratio of adsorbent to uranium removal efficiency. Adsorbent was synthesized through several stages, i.e., pyrolysis of coconut shell (400 °C), chemical activation using NaOH, and impregnation process using varied solutions of MgCl₂ (600 °C). The materials were characterized comprehensively using FTIR, BET, XRF, and XRD. The parameters studied in this research were adsorption temperature (T), average particle diameter of adsorbent (d), mass ratio of adsorbent to wastewater solution (r), and impregnation ratio of Mg(OH)₂/activated carbon. The results shown that equilibrium data are well fitted with the Langmuir isotherm model with the maximum adsorption capacity about 85 mg/g at 303 K and dimensionless constant separation factor (RL) value about 0.7. The adsorption rate was increased by increasing the adsorption temperature, mass ratio of adsorbent to wastewater solution, and the decrease of particle diameter of adsorbent with mathematical equation of the uranium (VI) adsorption rate as:[Formula: see text]In addition, the results also shown that increasing the impregnation ratio from 0.3 to 1.0 can increase the uranium removal efficiency up to 67.3%.

Biochar produced from agricultural residues through pyrolysis has the characteristics of large specific surface area and porous structure and thus can be used as an adsorbent for various contaminants. In this study, five types of agricultural residues, peanut shells (PS), mung bean shells (MBS), rice husk (RH), corn cob (CC), and cotton stalks (CS), were selected as feedstocks to prepare biochars. Magnesium chloride (MgCl₂; 5 mol L⁻¹ m) solution was used as a modifier to prepare pre-modified and post-modified biochar adsorbents. The modified biochars were used in adsorption experiment to test their sorption ability to phosphate from aqueous solution. Model simulations and analysis were used to determine phosphorus removal mechanisms. Experimental results showed that the phosphate removal efficiency of the pre-modified cotton stalk paralyzed at 600 °C (Pre-CS600) was the best with adsorption capacity of 129.9 mg g⁻¹. The results also showed that the adsorption capacity of the biochar pre-modified by MgCl₂ was much better than that of unmodified and post-modified ones, suggesting the pre-modification method can be used to prepare modified biochars for the removal of phosphorus from aqueous solution.

Lead wastewater not only causes deterioration of water quality but also further enters the human body through the food chain and is harmful to human health. Therefore, there is an urgent need to find an economical, simple and efficient water treatment technology to treat lead-contaminated wastewater in waterbodies. In this paper, the modified biochar derived from corn straw by magnesium chloride is prepared. Adsorption experiments of Pb(II) in solution by the modified biochar are carried out. Experiment results show that the modified biochar mainly contains C and O elements, and a large number of functional groups. The adsorption amount of Pb(II) by modified biochar reaches 5.15 mg/g under 0.2 g of modified biochar, 25 mg/L initial concentration of Pb(II) ion, reaction time of 480 min, temperature 25°C and at a speed of 200 rpm. The adsorption process of Pb(II) ions in solution by the modified biochar fits on the Freundlich isotherm model. Pseudo-second order kinetic model can better describe the adsorption process of Pb(II) ion in solution by the modified biochar. The process of adsorbing Pb(II) ions in solution by modified biochar is dominated by multi-layer adsorption process and chemical adsorption process.

Investigations of vegetation stress along non-paved roads treated with a range of magnesium chloride (MgCl₂) application rates utilized 60 roadside and 79 drainage plots on 15 and 18 roads, respectively. Evaluations were completed of foliar damage, plant health, biotic and abiotic damage incidence and severity, soil and foliar chemistry and other common site and stand characteristics of Pinus contorta, Populus tremuloides, Picea engelmannii, Abies lasiocarpa, and lower elevation plots dominated by shrubs and grasses. High concentrations of soil magnesium and chloride (400-500 ppm), high foliar chloride (2,000-16,000 ppm depending on species) and high incidence of foliar damage were measured in roadside plots along straight road segments in the first 3 to 6.1 m adjacent to treated roads. In drainage plots, where water is channeled off roads, high concentrations of both magnesium and chloride ions and associated foliar damage were measured between 3 and 98 m from the road. High incidence of foliar damage and elevated ion concentrations were not apparent in control plots along non-treated roads. Lodgepole pine appeared to be the most sensitive species, while aspen accumulated the most chloride and exhibited the least amount of damage. Foliar chloride concentrations strongly correlated with percent foliar damage for all species (r = 0.53 to 0.74, p < 0.0001) while the incidence of biotic damages did not correlate well. Positive relationships between foliar chloride and magnesium chloride application rates were strong and can be used to predict foliar concentrations and subsequent damage to roadside trees.

In this study, an innovative material (nitrogen, phosphorus, and oxygen controlling agent, NOC) was synthesized by calcium peroxide (CaO₂), magnesium chloride (MgCl₂), bentonite, zeolite, cement, stearic acid (SA), citric acid (CA), and silver sand. The treatment performance of NOC in mimic black-odor river water was investigated in lab-scale, and the results showed that over 73.7% phosphorus and 77% ammonia nitrogen were removed from river water with the addition of 470 g NOC at 30 mL h⁻¹ flow rate, demonstrating that the presence of NOC could remove phosphorus and ammonia nitrogen simultaneously. Moreover, the addition of NOC could release oxygen with tender influence on pH in water. Calcium phosphate (Ca-P), aluminum phosphate (Al-P), and ferric phosphate (Fe–P) in the river sediment increased from 1.6, 0.136, and 0.12 mg g⁻¹ to 2.16, 0.242, and 0.196 mg g⁻¹ for 28 days, respectively. The results manifested that the mobile phosphorus could be adsorbed by NOC and further transformed to inert phosphorus form, thereby restraining the release of endogenous phosphorus from sediment to the overlying water. Besides, the relative abundance of microorganisms could be enhanced with the existence of NOC, further promoting the removal of phosphorus. Hence, NOC could be applied to the efficient remediation of the black-odor river.

Wastewater from a limestone-gypsum wet desulfurization system cannot be directly reused or discharged due to its high suspended matter content and complex water composition. Desulfurization wastewater evaporation in flue gas is an effective way to dispose wastewater. Multicomponent soluble chlorine salts exist in the desulfurization wastewater. During the evaporation, chlorine enters into the flue gas due to volatilization, which accelerates the enrichment rate of the Cl⁻ concentration in the desulfurization slurry and leads to an increase in wastewater production. This study explored the chlorine migration of various chlorine salt solutions and typical desulfurization wastewater at high temperature during the evaporation process of concentrated wastewater by a laboratory-scale tube furnace and a pilot-scale system. Results showed that when NaCl-evaporated substance was heated, the chlorine ion hardly volatilized. For the evaporated substances of CaCl₂ and MgCl₂ solutions, some of the crystal water was lost, and hydrolysis occurred to generate gaseous HCl. NH₄Cl was easily sublimed, and the decomposition temperature was lowest. A pilot study on spray evaporation of desulfurization wastewater in flue gas showed that the particle size of the evaporated product increased and the main particle size was within 2.5–10 μm with increasing flue gas temperature. Increasing the mass ratio of gas to liquid significantly reduced the particle size of the atomized particles, thereby reducing the average particle size of the evaporated particles. The HCl concentration increased with increasing flue gas temperature. When the flue gas temperature was 350 °C, the concentration of HCl was 40 ppm, and the escape rate of chlorine in the desulfurization wastewater was approximately 30% using typical wastewater from a limestone-gypsum wet desulfurization system.