فهرست مطالب k. hashemimajd

Utilizing sewage sludge as a source of cheap fertilizer and rich in nutrients is common in some parts of Iran. But, too much application causes accumulation of heavy metals in soil, which results in soil pollution and transfer of this pollution to food chain and endangers human and animal health. The aim of this research was to investigate the effect of biological sludge of Tabriz petrochemicals complex on some heavy metals concentration in spring barley grown in a calcareous soil after 6 months of incubation. The experiment was conducted in greenhouse conditions with 5 levels of 0 (control), 25, 50, 75 and 100 ton/ha sewage sludge, in three replications, based on complete randomized blocks design. Soil analysis showed that application of biological sludge significantly increased DTPA extractable Fe, Zn, Mn, Cu and Cd (except 25 ton/ha treatment) compared to the control. The results of plant analysis showed an increase of Fe, Zn and Mn in shoots and Zn and Mn in roots, compared to the control. But elevation of root Fe content was not significant. The amount of Cu and Cd in shoots and roots was below the detection limit of the instrument. Overall, it was concluded that although the application of biological sludge increased the content of heavy metals in soil, but its effect on concentration of toxic elements, such as Cd, in plants was not significant.

The ability of earthworms in recycling a wide range of organic solid wastes is well established. Only a few earthworm species are suitable for commercial vermicomposting. Two species, Eisenia foetida and Lumbricus rubellus, are common in temperate regions. Samples of earthworms were collected from manure pills and forest litter in North and Northwest of Iran. The samples were maintained in pots under greenhouse conditions. External morphological characteristics of mature worms were used in identifying earthworm species. These characteristics included: total number of body segments, numbers of clitellum and tubercula pubertatis (TP) segments, dorsal and external body color, body size, prestomium and prostomium shape, number of first segment with dorsal pore and patterns of clitellum and TP. All collected samples belonged to the species Eisenia foetida. Under incubation conditions in manure substrate (a moisture of 70% saturation at 24±2oC), each worm produced 1-2 cocoons daily and each cocoon contained 2-7 worm embryos. The collected earthworm samples showed a good ability in vermicomposting of manure, plant residues, and some organic industrial refuses. The C:N ratio decreased during the vermicomposting process, which indicates the improved stage of decomposition and the vermicompost stability.