Soil chemistry adjacent to roads treated with dust control products at Loess Bluffs National Wildlife Refuge

The health of soils along roadways is critical for maximizing habitat quality and minimizing negative ecological effects of roads. Adjacent to unpaved roads, soil chemistry may be altered by the deposition of dust, as well as by road treatment with dust suppressants or soil stabilizer products. If present in roadside soils, these product residues may be available to plants, terrestrial invertebrates, or small mammals. Unfortunately, very few studies have attempted to track the transport of dust suppressants after application. As part of a larger ongoing study on the environmental effects of dust suppressant products on roadside plants and animals, we sampled roadside soils at Loess Bluff National Wildlife Refuge in 2015. Replicated road sections at Loess Bluff National Wildlife Refuge had been previously treated with two road productscalcium chloride-based durablend-C and synthetic iso-alkane EnviroKleen. In order to quantify the effect of dust suppressant treatment on roadside soils, we took replicated composite soil samples one year after treatment at 1m and 4m from the roads edge, and analyzed samples for a suite of soil chemistry variables (pH, conductivity, NO3-N, P, K, Ca, Mg, Na and S). We also assessed dust suppressant product residues in the soil. For durablend-C, we used soil conductivity as an indicator. For EnviroKleen, we developed a method for extraction and isolation, followed by analysis with gas chromatography/mass spectrometry to look for a specific EnviroKleen signature. Surprisingly, soil conductivity was not elevated adjacent to road sections treated with durablend-C, relative to other sections. EnviroKleen was detectable at both 1m and 4m from treated sections at concentrations from 1 to 1500 mg/kg, and was non-detectable in soils adjacent to the untreated section. The most notable characteristic of soils across all treated and untreated sections at 1m was elevated calcium (up to 30,000 mg/kg), likely as a result of dust deposition from the limestone surface aggregate. These results indicate that, at least in some cases, soil chemistry may be more influenced by proximity to the road itself than by treatment with a dust suppressant product. Importantly, this study is the first to detect and quantify a synthetic fluid product in soils adjacent to a treated roadway. In addition to informing ecological risk assessments for dust suppressants, these results can help practitioners make informed choices about environmentally responsible unpaved road management.