Path Analysis of Heavy Metal Adsorption by Soil

Abstract

Path analysis, a statistical technique that differentiates between correlation and causation, was used to describe heavy metal adsorption by soil. A path analysis model that evaluates the effect of soil pH, CEC, organic carbon content (OC), and clay content on adsorption of Cd, Cu, Ni, Pb, and Zn by soils from two long‐term cropping experiments in Sutherland and Kanawha, IA, was investigated. In general, direct effects of soil properties on metal adsorption were pH > OC > CEC. Path analysis direct effects of pH on Cd (0.83), Cu (0.93), and Pb (0.96) by Galva (fine‐silty, mixed, mesic Typic Hapludoll) soils from the Sutherland experiment were highly significant (P < 0.01). Significant (P < 0.01) direct effects of pH on Cd (0.93), Cu (0.95), and Pb (0.85) adsorption by Webster (fine‐loamy, mixed, mesic Typic Haplaquoll) soils from the Kanawha experiment. Significant (P < 0.01) simple correlation coefficients were found between soil pH and Cd (0.64), Cu (0.89), and Pb (0.84) adsorption by Galva soils and between soil pH and Cd (0.82), Cu (0.74), and Pb (0.62) adsorption by Webster soils. Both path analysis and correlation analysis showed that soil pH was the predominant property affecting Cd, Pb, and Cu adsorption by soil. However, path analysis revealed three additional relationships not found by correlation analysis. They included direct effects of CEC on Ni adsorption (0.72*), OC on Pb adsorption (0.35*) by Galva soils, and OC on Cd adsorption (0.59*) by Webster soils. Partitioning of OC direct and indirect effects suggested that adsorption of Pb and Cd by soil organic matter through complexation reactions was more important than adsorption by organic matter CEC sites.

Thermal conductivity of soils with heavy metals concentration from the Niger Delta region of Nigeria

“…The presence of these metals may therefore increase the effective thermal conductivity of soils to a considerable level. This complements the paper of Basta et al(1993) and Almas et al(2000) on the adsorption of Pb and Cd by soil organic matter through complexation reaction with organic matter, and Abu-Hamdeh and Reeder (2000) whose useful attempts to study the relationship between percentage increment of organic matter in clay loam soil and thermal conductivity yielded an inverse relation. …”

Pó-de-aciaria como fonte de zinco para o milho e seu efeito na disponibilidade de metais pesados

“…Muitos trabalhos têm demonstrado que a retenção e solubilidade dos metais pesados no solo são fortemente influenciadas pelo pH (HARTER, 1983;CUNHA et al, 1994;MARTINEZ e MOTTO, 2000;ALCÂNTARA e CAMARGO, 2001;DIAS et al, 2001), pela quantidade de metal no solo (BASTA e TABATABAI, 1992), pela CTC (ZIPER et al, 1988;CUNHA et al, 1994), pela matéria orgânica (ELLIOT et al, 1986;LEWIS e RULE, 2001) e pela mineralogia do solo (ZIPER et al, 1988). O pH possui forte influência na retenção de metais no solo, sendo esta maior em pH elevado (BASTA et al, 1993;CUNHA et al, 1994;MARTINEZ e MOTTO, 2000;ALCÂNTARA e CAMARGO, 2001;DIAS et al, 2001).…”

Heavy metal distribution between fractions of humic substances in heavily polluted soils

“…Ladonin and Margolina (1997) attributed this effect to the forming of coordination complexes in the case of Pb and Cu, while Zn and Cd were characterized rather by ion exchangetype reaction. However, Basta et al (1993) showed that both Cd and Pb complexation with organic matter was more important than their adsorption through cation exchange. The strength of metalhumic complexes is influenced by soil pH and ionic strength (Ladonin and Margolina 1997, Adriano 2001, Evangelou and Marsi 2001.…”