Reduction of bioaccessibility and leachability of Pb and Cd in soils using sludge from water treatment plant
The adsorption properties of sludge from drinking water treatment station make it an option to remediate soils contaminated with toxic metals. This paper describes the reuse of this sludge to immobilize Pb and Cd from contaminated soils, as well as the efficiency of this process applying bioaccessibility assays to evaluate how this sludge/soil mixture can mitigate the exposition that could potentially affect the health of individuals. The adsorption test revealed that Pb and Cd bound five and eight times more strongly to the sludge as compared to soil, respectively. The bioaccessibility assay showed that the best proportion of sludge/soil was 1:1 for both metals, with the reduction of 28.8% and 34.5% for Pb and Cd bioaccessibility, respectively. The high amount of organic matter of sludge could underlie the Pb and Cd stabilization and the decrease in the bioaccessibility. Chemical fractioning revealed that Pb stabilized better on Fe, Al, and Mn oxides. After 4 months, the exchangeable fractions together were less than 3% in samples with sludge/soil ratio 1:1, indicating that Pb is less available for leaching and became more stable. Cd was less leachable and reached stable fractions faster in samples with sludge/soil ratio 1:1. Based on these results, the sludge represents a potential adsorbent for simple Pb and Cd remediation in soils.
KeywordsCadmium Contaminated soil Lead Remediation
The authors are grateful to Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) for financial support (Grant#2009/00158-8). We are also grateful to the Water Treatment Plant in the city of São Carlos, Brazil, for providing the sludge samples.
Compliance with ethical standards
Conflict of interest
There are no conflicts to declare.
- Alonso Castillo ML, Vereda Alonso E, Siles Cordero MT et al (2011) Fractionation of heavy metals in sediment by using microwave assisted sequential extraction procedure and determination by inductively coupled plasma mass spectrometry. Microchem J 98:234–239. https://doi.org/10.1016/j.microc.2011.02.004 CrossRefGoogle Scholar
- Elliott HA, Dempsey BA, Maille PJ (1990) Content and fractionation of heavy metals in water treatment sludges. J Environ Qual 19:330. https://doi.org/10.2134/jeq1990.00472425001900020021x CrossRefGoogle Scholar
- Gee GW, Bauder JW (1986) Methods of soil analysis part 1: physical and mineralogical methods, 2nd edn. American Society of Agronomy, Inc. and Soil Science Society of America, Inc, MadisonGoogle Scholar
- Karadaş C, Kara D (2012) Chemometric evaluation for the relation of BCR sequential extraction method and in vitro gastro-intestinal method for the assessment of metal bioavailability in contaminated soils in Turkey. Environ Sci Pollut Res 19:1280–1295. https://doi.org/10.1007/s11356-011-0646-6 CrossRefGoogle Scholar
- Kulikowska D, Gusiatin ZM, Bułkowska K, Klik B (2015b) Feasibility of using humic substances from compost to remove heavy metals (Cd, Cu, Ni, Pb, Zn) from contaminated soil aged for different periods of time. J Hazard Mater 300:882–891. https://doi.org/10.1016/j.jhazmat.2015.08.022 CrossRefGoogle Scholar
- Nordberg GF, Nogawa K, Nordberg MFL (2007) Handbook on the toxicology of metals, 3rd edn. Academic Press, LondonGoogle Scholar
- Roy WR, Krapac IG, Chou S-FJ, Griffin RA (1992) Technical resource document: batch-type procedures for estimating soil adsorption of chemicals. EPA, WashingtonGoogle Scholar
- Schintu M, Marrucci A, Marras B et al (2016) Heavy metal accumulation in surface sediments at the port of Cagliari (Sardinia, western Mediterranean): environmental assessment using sequential extractions and benthic foraminifera. Mar Pollut Bull 111:45–56. https://doi.org/10.1016/j.marpolbul.2016.07.029 CrossRefGoogle Scholar
- Schumacher BA (2002) Methods for the determination of total organic carbon in soils and sediments. Carbon N Y 32:25. http://epa.gov/esd/cmb/research/papers/bs116.pdf
- U.S. EPA (1986) Method 9081: Cation-Exchange capacity of soils (Sodium Acetate). 1986, 1–4. https://www.epa.gov/hw-sw846/sw-846-test-method-9081-cation-exchange-capacity-soils-sodium-acetate
- U.S. EPA (1996) Method 3050B: acid digestion of sediments, sludges, and soils, Revision 2. Washington, DC, pp 1–12. https://www.epa.gov/homeland-security-research/epa-method-3050b-acid-digestion-sediments-sludges-and-soils