Metal contamination of agricultural soils amended with biosolids (sewage sludge) at a ceramic production area in NE Spain: A 10-year resampling period

Abstract

Heavy metals in ecosystems affect human health through the web chain. Castellon Province is home to the largest ceramic production hub in Spain, with 94% of the country's total production. Agricultural soils in the vicinity of the ceramic hub were reported to contain potentially toxic elements (Pb, Cr, Ni and Cd) in 2008 and have since been subject to repeated amendment with biosolids (sewage sludge). The sample sites were revisited in 2019, and the chemical distribution of these metals reassessed. The distribution of heavy chemical forms was analysed using a sequential extraction protocol that fractionates these four heavy metals into five phases. The incorporation of biosolids for the past 10 years has changed the chemistry of the soil, leading to increased levels of some hazardous elements. The carbonate-sorbed, residual and reducible phases were dominant. From the point of view of compliance with regulations, levels of Cd remained elevated and have increased over the 10-year period.