Assessment of Geochemical Mobility of Metals in Surface Sediments of the Santa Rosalia Mining Region, Western Gulf of California

Abstract

To asses the geomobility of cadmium, copper, iron, manganese, nickel, lead, and zinc in marine sediments near the Santa Rosalía copper smelter, which is located on the eastern coast of the Baja California Peninsula, sequential leaching was applied to sediment samples containing different levels of Cu: (1) uncontaminated or slightly contaminated (<55 mg kg⁻¹ Cu); (2) moderately contaminated (55-500 mg kg⁻¹ Cu); and (3) heavily contaminated (>500 mg kg⁻¹ Cu). Concentrations of Cd, Cu, Fe, Mn, Ni, Pb, and Zn in four fractions of the leachate (mobile fraction F1, relatively mobile fraction F2, associated with organic matter/sulphides fraction F3, and residual fraction F4) were measured by atomic absorption spectrophotometry (AAS). The sediments with Cu concentration <500 mg kg⁻¹ displayed prevalence of mobile acid-leachable fraction F1 and reducible fraction F2 for Cd, Cu, Mn, and Pb, whereas the relative contribution of fraction F3 was relatively low for all of the examined metals. Residual fraction F4 was highest (>65%) for Fe and Ni because both metals are associated with the crystalline matrix of natural sediments. The sediments heavily contaminated with Cu (>500 mg kg⁻¹) had dramatically increased percentages of Cu, Mn, Pb, and Zn, ranging on average from 63 to 81%, in the residual fraction. In the case of Cu, for example, the relative abundances of this element in the different fractions of such sediments followed this sequence: residual fraction F4 (76 ± 5%) >absorbed form and carbonates fraction F1 (15 ± 5%) >Fe and Mn oxyhydroxides fraction F2 (5 ± 2%) >fraction associated with organic matter and sulphides F3 (4.5 ± 3.9%). Copper, Pb, and Zn contents in each geochemical fraction of all samples were compared with sediment-quality guideline values ("effects range low" [ERL] and "effects range medium" [ERM]) to assess their possible negative effects on biota. Copper contents in mobile fractions F1 and F2, which were moderately contaminated with Cu, were higher than ERL but lower than ERM guideline values. For heavily contaminated sediments, Zn contents of mobile fractions F1 and F2 were higher than ERL but lower than ERM guideline values. The Cu content of fraction F1 was higher than ERM guideline values, whereas for fractions F2 and F3 copper content was higher than ERL guidelines but still lower than ERM guideline values.

Fractionation and risk assessment of Fe and Mn in surface sediments from coastal sites of Sonora, Mexico (Gulf of California)

“…These differences may be due to the natural composition of the sediments, and more importantly, they are related to industrial activities, such as mining and agriculture (Ghrefat et al 2012;Li et al 2011;Ochoa-Valenzuela et al 2009). Mn concentrations were similar to those (from 125.36 to 416.31 mg/kg) previously reported by Ochoa-Valenzuela et al (2009) in sediments located in Bacochibampo Bay, Sonora, Mexico, but lower than those values (from 50 to 32,600 mg/kg) reported by Shumilin et al (2011) in surface sediments of the Western Gulf of California.…”

“…The total Fe and Mn values were found to be slightly higher than those values (from 0.6 to 1.72 %) reported by Ochoa-Valenzuela et al (2009) in surface sediments from Bacochibampo Bay, located south of Sonora, Mexico, but lower than those levels (from 21,800 to 102,400 mg/kg) reported by Shumilin et al (2011) in surface sediments of the Western Gulf of California. These differences may be due to the natural composition of the sediments, and more importantly, they are related to industrial activities, such as mining and agriculture (Ghrefat et al 2012;Li et al 2011;Ochoa-Valenzuela et al 2009).…”

“…The highest levels of carbonates were detected in Guaymas samples (site 4), showing a relatively high calcite content at this site consistent with the abundance of shell fragments of calcareous organisms. Carbonates in marine systems are associated to metal mobility and toxicity into the water and sediments (Holmström et al 1999;Shumilin et al 2011).…”

Vertical profiles of cobalt and zinc in marine sediments of the Santa Rosalía mining region, Gulf of California, Mexico.

“…This area displays high levels of metals that are associated with former copper mining and smelting activities that were performed for nearly a century (Wilson and Rocha, 1955;Rodríguez Figueroa, 2004). There is clear evidence of the pollution of surface sediments by such solid waste dumping (Shumilin et al, 2000;Rodríguez Figueroa, 2004, 2010; however, recent data were somewhat encouraging, as the heavy metals from highly polluted sites were shown to be mainly concentrated in the residual fraction of the surface sediments (Shumilin et al, 2011). Additionally, an analysis of the metal levels in brown seaweeds showed that most toxic metals were retained in the sediments and were not released to the water column (Choumiline et al, 2006;Rodríguez Figueroa, 2010;Rodríguez-Figueroa et al, 2010).…”

Niveles De Metales Pesados en Sedimentos De La Cuenca Del Río Puyango, Ecuador

“…Aunque los sedimentos de los ríos Calera, Amarillo y Puyango muestran concentraciones de Mn, Cu, Co y Ni inferiores a las encontradas en sedimentos de zonas marino-costeras ubicadas en la Península de Baja California (México), también impactadas por la explotación minera del Cobre (Shumilin et al 2011, Shumilin et al 2013, las concentraciones de Pb y Zn en los sedimentos del Puyango son superiores a las de los sedimentos de esas zonas de México. Los resultados obtenidos en este estudio también indican que las concentraciones de Mn, Pb, Cu y Zn en los sedimentos del Puyango son mayores a las concentraciones de estos mismos elementos reportadas por Adánez et al (2014) en los sedimentos de los ríos Odiel y Tinto (Mn 717 y 187 mg/kg, Pb 212 y 977 mg/kg, Cu 1220 y 535 mg/kg y Zn 452 y 232 mg/kg), ríos que drenan cuencas localizadas en la Faja Pirítica Ibérica (Huelva, España) y que han sido fuertemente afectados por las actividades mineras y el drenaje ácido de minas por más de 5000 años (Cánovas et al 2007).…”