Page 143 - Enzymes in Tropical Soils

Enzymes in Tropical Soils 131

Soils contaminated with Pb were also found in the lands with intensive
transportation (Minami and Araki, 1975; Tiller, 1989; Akhter and Madany, 1992;
Markus and McBratney, 1996). The general pattern of Pb distribution adjacent to
the heavy traffic roads or highways is depicted in Fig. 9.2 (Tiller, 1989). Paddy
fields around Cr mines in Vietnam (Co Finh) were also contaminated with Cr,
Co,and Ni. These heavy metals may endanger human health through agricultural
products and animals (Kien et al., 2010). Berenguer et al. (2008) reported that
long-term uses of liquid wine industry significantly increased the concentrations of
Cu and Zn in soils. The concentration of Cu, Ni, Hg, Pb, Cd, and As in sediment
samples from waste treatment unit in Guiyu, Guangdong, China, also significantly
increased above their natural concentrations (Guo et al., 2009). Benke et al. (2008)
also showed that the total concentration and avalabilities of Cu and Zn significantly
increased with long-term application of cow residues. Lately, Kargar et al. (2013)
found significantly higher concentrations of Cu, Cd, Zn, and Pb in soils from
commercial streets, possibly as a result of heavier traffic as compared with
residential streets. It is obvious that external inputs may increase the heavy metal
concentrations higher than the safe levels.

Pb Concentration Soil

Vegetation

Distance from highway

Fig. 9.2. Lead distribution in soil and vegetation adjacent to the heavy
traffic roads or highways (After Tiller, 1989).

Abdul Kadir Salam - 2014