title: Soluble organic carbon and pH of organic amendments affect metal mobility and chemical speciation in mine soils.
abstract: We evaluated the effects of pH and soluble organic carbon affected by organic amendments on metal mobility to find out the optimal conditions for their application in the stabilization of metals in mine soils. Soil samples (pH 5.5-6.2) were mixed with 0, 30 and 60 th a(-1) of sheep-horse manure (pH 9.4) and pine bark compost (pH 5.7). A single-step extraction procedure was performed using 0.005 M CaCl2 adjusted to pH 4.0-7.0 and metal speciation in soil solution was simulated using NICA-Donnan model. Sheep-horse manure reduced exchangeable metal concentrations (up to 71% Cu, 75% Zn) due to its high pH and degree of maturity, whereas pine bark increased them (32% Cu, 33% Zn). However, at increasing dose and hence pH, sheep-horse manure increased soluble Cu because of higher soluble organic carbon, whereas soluble Cu and organic carbon increased at increasing dose and correspondingly decreasing pH in pine bark and non-amended treatments. Near the native pH of these soils (at pH 5.8-6.3), with small doses of amendments, there was minimum soluble Cu and organic carbon. Pine bark also increased Zn solubility, whereas sheep-horse manure reduced it as soluble Zn always decreased with increasing pH. Sheep-horse manure also reduced the proportion of free metals in soil solution (from 41% to 4% Cu, from 97% to 94% Zn), which are considered to be more bioavailable than organic species. Sheep-horse manure amendment could be efficiently used for the stabilization of metals with low risk of leaching to groundwater at low doses and at relatively low pH, such as the native pH of mine soils.
authors.affiliation: Organic and Bio-Organic Chemistry Department, Sciences Faculty, Universidad Nacional de Educación a Distancia (UNED), Paseo de Senda del Rey 9, 28040 Madrid, Spain. Electronic address: jpereze@madrid.uned.es.
authors.forename: Javier
authors.initials: J
authors.lastname: Pérez-Esteban
authors.affiliation: Organic and Bio-Organic Chemistry Department, Sciences Faculty, Universidad Nacional de Educación a Distancia (UNED), Paseo de Senda del Rey 9, 28040 Madrid, Spain. Electronic address: cescolastico@ccia.uned.es.
authors.forename: Consuelo
authors.initials: C
authors.lastname: Escolástico
authors.affiliation: Soil Science Department, Agricultural Engineering School, Universidad Politécnica de Madrid, Avenida Complutense s/n, 28040 Madrid, Spain. Electronic address: alberto.masaguer@upm.es.
authors.forename: Alberto
authors.initials: A
authors.lastname: Masaguer
authors.affiliation: Soil Science Department, Agricultural Engineering School, Universidad Politécnica de Madrid, Avenida Complutense s/n, 28040 Madrid, Spain. Electronic address: c.vargasv@alumnos.upm.es.
authors.forename: Carmen
authors.initials: C
authors.lastname: Vargas
authors.affiliation: Soil Science Department, Agricultural Engineering School, Universidad Politécnica de Madrid, Avenida Complutense s/n, 28040 Madrid, Spain. Electronic address: ana.moliner@upm.es.
authors.forename: Ana
authors.initials: A
authors.lastname: Moliner
mesh_terms: D000818:Animals; D002244:Carbon / Q000032:analysis*; D006736:Horses; D006863:Hydrogen-Ion Concentration; D008372:Manure; D008670:Metals / Q000032:analysis* / Q000302:isolation & purification; D008906:Mining; D012756:Sheep; D012989:Soil Pollutants / Q000032:analysis* / Q000302:isolation & purification; D012995:Solubility
chemical_list: D008372:Manure; D008670:Metals; D012989:Soil Pollutants; D002244:Carbon
keywords: Metal mobility; Pine bark; Sheep–horse manure; Soluble organic carbon; Speciation modeling