Transport and adsorption-desorption of heavy metals in different soils

Understanding the reactivity and mobility of heavy metals in soils is indispensable for assessing their potential risk to the environment. In this study, column transport and batch kinetic experiments were performed to assess the sorption-desorption and mobility of Cd, Cu, Pb, and Sn in alkaline and acidic soils. Furthermore, sequential extractions were accomplished to examine their behavior in soils. Also, the competitive reactivity of Sn and Pb in two acidic soils was quantified. Additionally, the effect of introducing Cd and Cu after a Pb pulse in calcareous soil was presented. Modeling of these heavy metals retention and transport was carried out using different models; multireaction and transport model, CXTFIT model, kinetic ion exchange formulation, and second-order two-site model. The results revealed that: 1) the studied heavy metals exhibited strong nonlinear and kinetic retention behavior; 2) Cd was nearly immobile in alkaline soil with 2.8% CaCO3, whereas 20 and 30% of the applied Cd was mobile in the acidic soil and the subsurface layer of the alkaline soil with 1.2% CaCO3, respectively; 3) for a short Cu pulse, the recoveries were \u3c1 and 11% for alkaline and acidic soils, respectively, whereas, for the long Cu pulse, the recoveries ranged from 27 to 85% for the studied soils; 4) tin was highly sorbed in acidic soils where more than 99% of applied Sn was retained in the acidic soils columns; 5) the presence of Sn in solution reduced Pb retention in soils since the Pb recovery in the effluent solution ranged from 37.4 to 96.4%; and 6) the multireaction approach was capable of describing heavy metals retention and transport in soil columns. Moreover, a field study of the spatial distributions and the accumulation of Pb, Cd, Cu, and Ni among soil depth as consequence of irrigation with domestic wastewater were studied. The results of this research showed that Pb, Cu, and Ni had high affinity for retention in the surface soil layer whereas Cd results showed homogeneous distribution within soil depth. The impact of time scale effect on accumulation and spatial distribution of heavy metals indicated the urgent need for remediation and rational management

Soil Compaction Thresholds for the M1A1 Abrams Tank: Field Study at Camp Minden, La. (Bulletin #891)

The purpose of this study was to establish critical soil compaction thresholds for M1A1 Abrams battle tank traffic in an effort to minimize soil physical properties that adversely affect vegetation regeneration.https://digitalcommons.lsu.edu/agcenter_bulletins/1004/thumbnail.jp

Multireaction Modeling of Lead (Pb) and Copper (Cu) Sorption/Desorption Kinetics in Different Soils

Batch kinetic experiments were carried out to quantify and describe the sorption/desorption of Cu and Pb in ten soils that exhibited a wide range of properties. Sorption isotherms were quantified using the Langmuir equation, whereas modeling of sorption/desorption kinetics was described using multireaction model (MRM). Results revealed the nonlinear sorption behavior of Cu and Pb in all soils. The ten soils exhibited higher affinity to Pb (6.4 to 36.5 mmol kg−1) in comparison to Cu (3.6 to 22.4 mmol kg−1). Simulation of Cu and Pb kinetic data indicated that the rate of sorption reaction was two orders of magnitude higher than the rate of release. Considering one irreversible site in addition to one-reversible kinetic site improved the estimation of rates of reaction for both Cu and Pb in acidic and alkaline soils. All soils exhibited sorption/desorption hysteresis where Pb-releases ranged between <0.2% and 14.4% of the total sorbed. The respective Cu releases ranged from <0.85% and 23.4%. The multireaction model, which was successful in describing Cu and Pb for all ten soils, provided insight into the processes of sorption/desorption of Cu and Pb in all soils