Heavy Metal Balances of an Italian Soil as Affected by Sewage Sludge and Bordeaux Mixture Applications

Abstract

AbstractApplications of sewage sludge and Bordeaux mixture (Bm) (a mixture of copper sulfate and lime) add heavy metals to the soil. At an experimental farm in the Cremona district (Italy), we measured current heavy metal contents in soil and their removal via harvested products. We also measured heavy metal adsorption by soil from this farm. With these data, projections were made of the long‐term development of heavy metal (Cd, Cu, and Zn) contents in soil, crop removal, and leaching at different application rates of sewage sludge and Bm. These projections were compared with existing quality standards of the European Union (EU) and Italy with regard to soil and groundwater. The calculations reveal that the permitted annual application rates of sewage sludge and Bm are likely to result in exceedance of groundwater and soil standards. Sewage sludge applications, complying with the Italian (I) legal limits, may pose problems for Cd, Cu, and Zn within 30, 70, and 100 yr, respectively. Furthermore, severe Cu pollution of integrated (mildew controlled by Bm and organopesticides) and especially organic (Bm only) vineyards is unavoidable with the currently allowed application rates of Bm. The results suggest that the current I soil protection policy as well as the EU policy are not conducive of a sustainable heavy metal management in agroecosystems.