Phthalates and nonylphenols in profiles of differently dressed soils

Abstract

The concentrations of nonylphenols and phthalates in depth profiles of eight differently dressed, fertilised and cultured fields were investigated. The fields were typical for Danish agriculture and comprised an uncultured location, two manured fields, an artificially fertilised field and three fields amended with different amounts of sewage sludge. In addition, a location receiving run-off from a sewage sludge storage facility were investigated. At each location, two 50 cm vertical soil cores were taken, divided into sections of 10 cm each and analysed for nonylphenols and phthalates by high-resolution mass spectrometry. Di-(2-ethylhexyl)-phthalate (DEHP) was the most abundant phthalate in all samples whereas Di-(n-butyl)-phthalate (DBP) played a minor role. Nonylphenols occurred in significant concentrations only in soil samples exposed to high amounts of sludge and at the run-off location. A close relationship was found between the concentrations of contaminants in the soil samples and the method of dressing. The concentrations were low at comparable levels in the soil samples from the artificially fertilised field and in the fields amended with low amounts of sludge, as well as in the manured fields. Remarkably, these concentrations did not differ significantly from the level in an uncultured recreational preserved area, which was used as a reference. In contrast, much higher levels of contaminants were found in the soil samples from fields exposed to high amounts of sludge. We must conclude that sludge amendment below a certain limit does not lead to elevated levels of nonylphenols and phthalates in the soils, whereas heavy sludge amendment leads to the accumulation of these contaminants. For the vertical distribution of substances in the soils, an influence of soil characteristics on the concentration profile was noted. Thus, in soils with visible clay in the upper layers, a DEHP maximum occurred at a depth of 10-20 cm, whereas in most sandy soils no such maximum was observed. A 2-year time trend study of the highly sludge amended soil showed no measurable reduction in the substances during this period. The time study further suggested a downward movement of the DEHP maximum of approximately 10 cm per year.