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United States Department of Agriculture

Agricultural Research Service

Title: Response of Soil Microbiological Activities to Cd, Pb, and Zn Salt Amendments

Authors
item Stuczynski, T - POLISH INST OF SOIL SCI
item McCarty, Gregory
item Siebielic, G - POLISH INST OF SOIL SCI

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 15, 2002
Publication Date: June 1, 2003
Citation: Stuczynski, T., McCarty, G.W., Siebielic, G. 2003. Response of soil microbiological activities to CD, PB, and ZN salt amendments. J. Environ. Qual. 32:1346-1355.

Interpretive Summary: The concept of defining criteria for assessing changes in soil quality is a well-accepted approach, but the existing regulatory values regarding soil pollution with heavy metals are mainly designed to protect the food chain and to control the risk of excessive accumulation of metals in plants. To protect soil habitat function, quantitative assessment tools are needed to determine the heavy metal toxicity factors that influence soil microbial processes. Experiments involving the amendment of soils with heavy metal salts are widely used for these assessments. We studied responses of the soil biological activities to metal stress simulated by soil amendment with Zn, Pb and Cd salts. The amounts of metal salts added to five metal polluted soils and four non-polluted soils were selected to match the total metal concentrations typically found in polluted soils of the Silesia region of Poland. We found that the impact of the metal amendments on biological activities could not be satisfactorily accounted for by metal toxicity because no strong relationship was observed between extractable metal content and the degree of inhibition. Thus, these metal amendment experiments appear to have limited utility for assessing metal pollution impacts on soil quality.

Technical Abstract: Heavy metal pollution of soil has been recognized as a major factor impeding soil microbial processes. We studied responses of the soil biological activities to metal stress simulated by soil amendment with Zn, Pb and Cd chlorides. The amounts of heavy metal salts added to five metal polluted soils and four non-polluted soils were selected to match the total metal concentrations typically found in polluted soils of the Silesia region of Poland. Metal mobility in amended soils could not be described by simple functions of pH or organic matter. Reaction of Pb with the soil caused strong immobilization with less than 1% of the Pb amendment recovered by 0.01 M CaCl2 extractions. Immobilization of Cd was also significant, whereas immobilization of the Zn amendment was much weaker than that of Cd or Pb. The Zn amendment had substantial inhibitory effect on soil dehydrogenase, acid and alkaline phosphatase, arylsulfatase, urease and nitrification potential. Generally, Cd and Pb had limited or stimulatory impact on most of these biological activities, with an exception of Pb strongly inhibiting soil urease. The impact of the metal amendments on biological activities could not be satisfactorily accounted for by metal toxicity because no strong relationship was observed between extractable metal content and the degree of inhibition. The Zn amendment had a significant impact on soil pH, resulting in confounding effects of pH and Zn toxicity on activities.

Last Modified: 10/1/2014
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