Bioconcentration of polycyclic aromatic hydrocarbons (PAH) in corn grains cultivated on the sewage sludge-amended soil

Abstract

The sewage sludge volume produced by wastewater treatment station has been growing every year, which constitute an important environmental problem. Because of its rich composition in organic matter, nitrogen and phosphorus, sewage sludge has been amended in agricultural soil to condition and fertilize soils. However, the sewage sludge contains many pathogenic organisms, heavy metals and organic pollutants. Like several of these organic pollutants are persistent and toxic for humans and wildlife, the agricultural use of the swage sludge can contaminate the environmental compartments and the agricultural crops, putting in risk human and aquatic and terrestrial organisms. In soil samples of experimental area of Embrapa Meio Ambiente was observed the presence of naphfthalene, benz(a)antracene and bez(a)pyrene, three polycyclic aromatic hydrocarbons (PAH). These samples were collected two years after successive applications of sewage sludge in a soil used for the experimental corn crops. PAH residues were found in samples of sewage sludge of wastewater treatment station of Barueri and Suzano municipality, both in São Paulo State. PAH are organic pollutants with an environmental and toxicological importance, because many of these pollutants are persistent and have carcinogenic and mutagenic properties to human and animals. Mathematical models and experimental studies preview and demonstrate that organic pollutant of sewage sludge can accumulate in plants. Some pollutants accumulate in plants as a consequence of your physic-chemical characteristics, such as water solubility and lipid affinity. The objective of this project will be verifying experimentally if the sixteen polycyclic aromatic hydrocarbons (PAH), classified as proprietary pollutant by US-EPA, are contained in a sewage sludge used as soil fertilize and observe if these pollutants can bioconcentration in corn grains of a corn crops cultivated in a soil fertilized with sewage sludge. The PAH studied by this project will be acenaphthene, acenaphthylene, anthracene, benz(a)anthracene, benz(a)pyrene, benz(b)fluoranthene, benz(k)fluoranthene, benzo (g-h-i)perylene, chrysene, dibenz(a,h)anthracene, fluoranthene, fluorene, indeno(1,2,3-cd)pyrene, naphthalene, phenanthrene and pyrene. The analyses will be accomplished to quantify residues of PAH in samples of sewage sludge, soil without report of applications of sewage sludge, soil with report of applications of sewage sludge, corn grains cultivated in a soil without report of addition of sewage sludge and in corn grains cultivated in a soil with only an application of sewage sludge. The analyses will allow to verify which PAH are contained in the sewage sludge and if they can contaminate soils and bioconcentrate in corn grains. We also can estimate if the found concentrations to damage the quality of the corn grains for human and animal consumption. The quantifications of PAH, in all samples will be obtained by high efficient liquid chromatography (HPLC) with fluorescence detection and will be confirmed by liquid chromatography system, coupled to a mass spectrometry (LC/MS/MS) and or a gas chromatography coupled to a mass spectrometry (GC/MS/MS). It will be estimated both the accumulated probability of distribution functions of concentrations and the probabilities that these concentrations exceed the acceptable maximum limits for environmental norms. The uncertainties associated to these estimates will be calculated by no parametric statistical methods. It will be developed a mathematical model to preview the bioconcentration of organic pollutants in corn grains. The model will be validated experimentally with the concentrations of PAH observed in the soil, sewage sludge and corn grains. The informations produced by the project will add knowledge that can be useful to improve the legislation about sewage sludge use as agricultural fertilizers and will help to establish safe limits of PAH in sewage sludge and soils. (AU)