Trace Metal Movement in an Aeric Ochraqualf following 14 Years of Annual Sludge Applications

Abstract

The potential for movement of sewage sludge‐borne trace metals beyond the zone of soil incorporation poses a real concern for society. To address this concern, we sampled an Aeric Ochraqualf (Blount Series) after 14 yr of massive, sludge additions (765 Mg ha−1 cumulative sludge applications, dry wt. basis). Cadmium, Zn, and Cu concentrations in each genetic horizon to a depth of 1.0 m were determined by atomic absorption spectroscopic analyses of 4.0 M HNO3 extracts. In addition, ped surfaces (cutans) and intra‐ped material (s‐matrix) from prismatic structural units of the lower B and upper C horizons were analyzed to determine the partitioning of trace metals in this highly structured profile. Cadmium concentrations in the subsoil of sludge‐treated areas were consistently and significantly higher (∼0.4 mg kg−1) than levels present in the control areas. Similarly, Zn concentrations in the 0.32 to 0.51 m region (Bt1) were increased (∼12 mg kg−1) with sludge applications; no increases in Cu levels were observed. Significantly more Cd (0.08 mg kg−1) was present in cutans removed from ped surfaces in the upper B horizon than was observed in the s‐matrix for sludge‐treated areas. Cutans also contained more sludge‐borne Zn than the associated s‐matrix. The evidence suggests that small amounts of sludge‐borne Cd and Zn moved out of the tillage zone into the subsoil of this highly structured agricultural soil over a 14‐yr period of massive sludge additions.

Movimentação de metais pesados em Latossolo adubado com composto de lixo urbano

“…A imobilidade do Cu também foi observada por Williams et al (1987), Dowdy et al (1991), Chino et al (1992 e Oliveira & Mattiazzo (2001) em solos tratados com elevadas doses de lodo de esgoto e monitorados por períodos de, respectivamente, 9, 14, 12 e 2 anos. A imobilidade do Cu normalmente é atribuída à formação de complexos organometálicos estáveis de baixa solubilidade (Taylor et al, 1995) e à ligação do metal às frações não trocáveis do solo, a chamada fração residual e a óxidos de Fe e Mn (Matos et al, 1996;Amaral Sobrinho et al, 1997).…”

Efeitos de aplicações sucessivas de lodo de esgoto em um latossolo amarelo distrófico cultivado com cana-de-açúcar: carbono orgânico, condutividade elétrica, ph e CTC

“…Nestes casos os autores atribuíram o efeito neutralizante às reações envolvidas na degradação da carga orgânica do resíduo. Por outro lado, trabalhos relatados por Simeoni et al (1984), Pietz et al (1989) e Dowdy et al (1991) revelaram, em solos cultivados, efeitos acidificantes desses resíduos, os quais foram atribuídos às reações de nitrificação, à provável oxidação de sulfitos e à produção de ácidos orgânicos durante a degradação do resíduo.…”

Metal sorption on soils as affected by the dissolved organic matter in sewage sludge and the relative calculation of sewage sludge application

“…A traditionally held view on the mobility of heavy metals in sewage sludge-amended soils is that the metals' migration is insignificant and the metals tend to remain in the site of input, i.e. in the topsoil [4][5][6][7]. However, in several field-base experiments the apparent migration of heavy metals to the deep was observed [8,9].…”