Page 202 - Soil Degradation, Conservation and Remediation

6.2 Sources of Soil Pollutants 191

Table 6.5 Some anthropogenic sources of heavy metals in soil

Sources Metals

Landfill/chemical waste dump As, Pb, Cr, Cd, Ba, Zn, Mn, Ni

Metal finishing/plating/electronics Cr, Pb, Ni, Zn, Cu, Cd, Fe, As
Chemical/pharmaceutical Pb, Cr, Cd, Hg, As, Cu
Mining/ore processing/smelting Pb, As, Cr, Cd, Cu, Zn, Fe, Ag
Battery recycling Pb, Cd, Ni, Cu, Zn
Wood treating Cr, Cu, As
Nuclear processing/equipment Ra, Th, U
Pesticides As
Vehicle As
Paint Pb, Cr, Cd, Hg

degradation (Kirpichtchikova et al. 2006 ), and their total concentration in soils
persists for a long time after their introduction (Adriano 2003 ). However, their
chemical speciation and bioavailability may change in soil. Heavy metal contami-
nation of soil may pose risks and hazards to humans and the ecosystem through
direct ingestion or contact with contaminated soil and the food chain, drinking
of contaminated water, and deterioration of food quality. Some soils are naturally
metalliferous; their parent materials and rocks contain high concentrations of metals.
Soils of mining areas are particularly high in heavy metals. A spectacular case was
reported by Balke et al. ( 1973 ) from the area of Nievenheim in the lower reaches of
the Rhine River, where a zinc processing plant has infiltrated wastewater onto the

−1
substratum. In the groundwater, the concentrations of arsenic surpassed 50 mg L ;
−1
maximum concentrations have been measured for cadmium of 600 μg L , thallium
−1
−1
−1
800 μg L , mercury 50 μg L , and zinc 40 mg L . The most common anthropogenic
sources of heavy metals in soil are summarized in Table 6.5 .
Natural Metalliferous Soils
The most important types of natural metalliferous soils are (1) serpentine soils,
developed from Fe- and Mg-rich ultramafic rocks, which are signifi cantly

enriched in Ni, Cr, and Co; (2) the calamine soils, enriched in Pb and Zn,
which contain elevated Cd also and sometimes carry high concentrations of As
and/or Cu; (3) Cu- and Co-containing soils such as those of the Shaban Copper
Arc in the Democratic Republic of Congo, derived from argillites and dolomites
containing sulfides of these metals, together with important secondary minerals

(oxides, basic carbonates, silicates); and (4) soils derived from various Se-rich
rocks. Serpentine soils occur over extensive areas in many countries of the
world such as Japan, the Philippines, Indonesia, the USA, Turkey, Greece and
the Balkan lands, parts of the European Alps, central Brazil, Cuba, Puerto Rico,
and parts of Central America. Notable Se-rich soils have arisen particularly
from the Cretaceous shales of the Midwestern USA (Mudgal et al. 2010 ).