Nitrogen cycle disruption through the application of de-icing salts on upland highways

It is hypothesized that episodic introductions of road salt severely disrupt the soil nitrogen cycle at a range of spatial and temporal scales. A field-scale study has confirmed impacts on the nitrogen cycle in soil, soil solution and river samples. There is evidence that ammonium-N retention on cation exchange sites has been reduced by the presence of sodium ions, and that ammonium-N has been flushed from the exchange sites. Increases in soil pH have been caused in naturally acidic uplands. These have enhanced mineralization of organic-N, especially nitrification, leading to a reduction in the mineralizable-N pool of roadside soils. There is evidence to support the hypothesis that organic matter content has been lowered over decades either through desorption or dispersal processes. Multiple drivers are identified that contribute to the disruption of nitrogen cycling processes, but their relative importance is difficult to quantify unequivocally. The influence of road salt on soil and soil solution declines with distance from the highway, but impacts on water chemistry in a local stream are still strongly evident at some distance from the road

Competitive and Noncompetitive Batch Sorption Studies of Aqueous Cd(II) and Pb(II) Uptake onto Coffea canephora Husks, Cyperus papyrus Stems, and Musa spp. Peels

Coffea canephora, Cyperus papyrus, and Musa spp. were studied for competitive and noncompetitive removal of aqueous Cd2+ and Pb2+. The optimal conditions were pH 4.5 and agitation time 3.0 hours. Biomass constituent ions showed no interference effects whereas cation exchange capacity values corresponded to the sorption efficiencies. XRD spectroscopy revealed surface oxygen and nitrogen groups that provide binding sites for metal ions. The maximum sorption efficiency ranges for metal ions in noncompetitive media were 95.2–98.7% for C. canephora, 42.0–91.3% for C. papyrus, and 79.9–92.2% for Musa spp. and in competitive sorption 90.8–98.0% for C. canephora, 19.5–90.4% for C. papyrus, and 56.4–89.3% for Musa spp. The Pb2+ ions uptake was superior to that of Cd2+ ions in competitive and noncompetitive media. In competitive sorption synergistic effects were higher for Cd2+ than Pb2+ ions. The pseudo-second-order kinetic model fitted experimental data with 0.917≤R2≥1.000 for Pb2+ ions and 0.711≤R2≥0.999 for Cd2+ ions. The Langmuir model fitted noncompetitive sorption data with 0.769≤R2≥0.999; moreover the Freundlich model fitted competitive sorption data with 0.867≤R2≥0.989. Noncompetitive sorption was monolayer chemisorption whereas competitive sorption exhibited heterogeneous sorption mechanisms