J. Phys. IV France
Concentrations of heavy metals in soil, Zimapan, MéxicoL.K. Ongley1, A. Armienta2 and H. Mango3
Androscoggin Valley Environmental Center, 221 Pease Hill Road, Monmouth, ME 04259,
Instituto de Geofisica, Universidad Nacional Autonoma de Mexico, CP. 04510,
Delegacion Coyoacan DF, México3
Department of Natural Sciences, Castleton State College, Castleton, VT 05735, U.S.A.
Pb-Zn-Ag mining and ore pocessing have occurred continuously in Zimapán,
México since at least 1632 and possibly since 1576 [1, 2]. This has resulted in the
development of significant slag and tailings piles. Dissolution of ore and tailings has
resulted in arsenic contamination of much of the water in the valley raising the possibility of
arsenicosis of the residents [3, 4, 5].
INAA and ICP analysis of more than 175 sediment, soil and tailings samples
demonstrate significant metal and arsenic contamination of these unconsolidated materials.
As, Cu, Pb, and Zn were among the measured elements.
Metal concentrations in soils and sediments were highest within 1000 m
or slag piles. Some of the highest soil metal concentrations were measured in a developing
soil on top of a slag pile: As-14 700 mg/kg, Cu - 8 638 mg/kg, Pb - 41444 mg/kg, and Zn -
16 976 mg/kg. Soils more than 4 000 m from the tailings and slag generally had less than 40 mg As/kg with Cu
< 30 mg/kg, Pb
< 64 mg/kg, and Zn
< 200 mg/kg.
Some rocks ftum the area also show elevated metal concentrations. For example,
the As concentrations in dikes and ores from Zimapàn averaged 1 242 and 30 800 mg/kg
respectively. Average shale As concentrations (74 mg/kg) match published data for shales
that indicate "normal" As concentrations range from
3-490 mg/kg are found world-wide .
Some of the soil contamination is natural, the result of the geologic processes
responsible for the Pb-Zn ores. However, particularly near the tailings and slag piles, the
soils are also contaminated by anthropogenic means: by dry particulate deposition from
smelters, by windblown tailings, and possibly by ore and rock dust from the ore transport
© EDP Sciences 2003