Resumen

PEREZ OLVERA, Ma. Antonia et al. Concentration of Pb, Cd, Ni, and Zn in Polluted Soils and their Transference to Broccoli Heads. Terra Latinoam [online]. 2008, vol.26, n.3, pp.215-225. ISSN 2395-8030.

Pb, Cd, Ni, and Zn concentration was quantified through atomic absorption spectrometry in soils and broccoli heads extracted with EDTA 0.05 M pH 7.0 ratio soil:extraction solution (w/v) 4:1 for soils and by wet digestion for plant tissue. Samples were taken from 28 plots irrigated with water under different management and from different origins: treated from the «chinampas» canal (TCC); treated at exit point 1 and 2 (TS1 and TS2); treated from main and secondary canals (TCPYS); treated mixed with sewage sludge (T+N); residual from local drainage (DL), and a fresh water control (BCA). Soil-broccoli head transference ratios were estimated, and pH, electrical conductivity (EC), organic matter (OM), N, and cation exchange capacity (CEC) in soil were analyzed. Concentrations of Zn, Pb, Ni, and Cd in soils ranged from 1.90 to 11.02, 3.74 to 6.42, 0.65 to 1.36, and 0.08 to 0.27 mg kg^-1, respectively, depending on location and irrigation water source. In broccoli heads, concentrations ranged from 30.60 to 47.16, from 0.8 to 4.49, from 0.77 to 1.03, and from 0.5 to 4.51 mg kg^-1 for Zn, Pb, Ni, and Cd, respectively. The concentrations of Cd, Ni, and Zn in the broccoli head are greater than those found in the soil, which indicates that in addition to soil there are other sources of these metals in the crop. There is a high degree of correlation among chemical characteristics of soils (OM, N, and CEC) and concentration of heavy metals in soil and broccoli heads. The Zn level in heads is within the range established for this crop. Uptake of Pb and Cd is below the level established by the FAO/WHO, considering an estimated consumption per capita of 2.8 kg per year.

Palabras llave : Brassica oleracea; heavy metals; transference ratios; contamination; wastewater irrigation.