Bioavailability And Environmental-Ecological Effect Of Elements In The Sludges Treated With Steam-explosion, Compost And Irradiation

A series of laboratory study, greenhouse aiil field experiniems were conducted to assess the effect of steam-explosion. composdng arxl irradiation on the chemical properties of sludge and its potential as organic amendment of the soil.The results indicated that dissolved organic matter (DOM), available N and P of sludge origin would be itiereased markedly under afflueneed by steam-explosion arxl irradiation. However, composting sludge resulted in the decrease of sludge-bonie available N, P and DOM. Of DOM derived from steam- explosion, compostmg and irradeated sludges, steam-explosion sludges DOM have more low molecular size fractions ( irradiated sludge >untreated sludge >coniposted sludge. Furthermore, the results obtained from the aerated ineubation experiment also exhibited that, compared to untreated sludge, steam-explosive sludge aid irradiated sludge have a higher mineralization rate of sludge -borre organic C aid N, while compostcd sludge-borne organic C aid N have a lower mineralization rate, which may be contributed to the breakdown of the refractory organic matrix due to steam-explosion aid irradiation. Accordingly, the results from die greenhouse aid field experiments showed as expected that N~ P~ Cu~ Zn have a much higher bioavailability for the steam-explosive ant irradiated sludges than that for untreatded sludge ant coniposted sludge,which was apparent especially ieredacidcsoil.Asart,theyieldsofWlieatarxiRiceobatixied in eitherfleld experiment or greenhouse pot experiment were iiiereased due to the application of irradiated aid steam-explosive sludge. It was fount that Cu and P sorption onto acklic red soil and calcareous clay loam could be drastically reduced in die presenee of DOM especially for die DOM derived from steam- explosive ant irradiated sludges. The dissolution of P and Cu in the tested soil (vegetable soil and orchard soil ) could also be facilitated apperently as affected by DOM.What is more ,the ability of DOM in mobilizing metal aid P in the soils is the funetkm of DOM cotieermtion ant molecular srze fraction as well as pH. To a gi~at extend, the higher coucentration ant 50 more low molecular size fraction of DOM derived from steam-explosive aixi irradiated sludge were or~ of the causes that the application of these two sludge gave a rise to a higher yield axxl elen~nt bioavailability with comparison to untreated or composted sludge.