Porównanie biotycznych i abiotycznych zmian WWA w glebie nawożonej osadami ściekowymi

W bogatej literaturze dotyczącej obecności WWA w środowisku znajdują się także pozycje potwierdzające występowanie tych związków w glebach i osadach ściekowych. Zawartość WWA w glebach zależy od rodzaju gleby (piaszczyste, gliniaste), miejsca jej występowania (tereny narażone na zanieczyszczenia antropogenne, nie narażone, leśne,) oraz sposobu użytkowania [1÷3]. Stopień zanieczyszczenia osadów ściekowych jest ściśle związany z obciążeniem ścieków poliaromatami. Zależy więc od rodzaju ścieków (różne odpływy przemysłowe, bytowe, opadowe) oraz od stopnia zmineralizowania materii organicznej [4÷6].

The Polish legislation demand control of heavy metals and pathogen organisms only in sewage sludge to be applied in the agriculture. However, the presence of toxic organic micropollutants such as PAHs in sewage sludge should be taken into account. Changes in the concentration of PAHs were analysed in this study. The digested and dewatered sewage sludge from municipal treatment plant and soil from agriculture area were used. The concentration of the these compounds was analysed in soil samples with added sludges and after one, two, three and four weeks of incubation of samples, respectively. The samples under biotic and abiotic conditions were incubated. 16 PAHs according to EPA were determined. The extraction of the organic solvents were used. For sewage sludge samples mixture of dichloro-methane and cyclohexane were used. For solid samples and mixture of solid and sewage sludge samples petrol ether as solvents were used. The extraction in ultrasonic batch were done. The extracts were separated from samples, purified on silica gel and concentrated under nitrogen stream. PAHs were determined using GC-MS. The limit of detection was in the range from 0.14 to 0.59 jug/L. The sum of 16 PAHs in sewage sludge taken from a municipal treatment plant was in the range of 1584 to 1912 |ng/kg.s.m. The content of hydrocarbons in soil was 218.5 ug/kg.s.m in average. The fluctuation in the concentration of PAHs both in the mixture of soil and sewage sludge under biotic and abiotic conditions were observed. After four weeks of the experiment in the soil supplemented with sewage sludge under biotic conditions, the contents of PAHs was lower than initial concentration of 28%. The final content of PAHs in samples under abiotic condition was lower than initial content of 26%. The fluctuations in the concentration both in the individual hydrocarbons and of the total contents were observed.