Effect of Organic Matter Oxidation on the Fractionation of Copper, Zinc, Lead, and Arsenic in Sewage Sludge and Amended Soils

Abstract

Long-term land application of sewage sludge (SS) has caused concern over the potential release of trace metals into the environment following the degradation of organic matter (OM). This study was performed to assess the impact of OM degradation on the relative distribution of Cu, Zn, Pb, and As in SS and SS-amended soils. Three SSs of different ages and two soils treated with SS were subjected to incubation and direct chemical oxidation using diluted HO, followed by a sequential extraction. The majority of Cu, Pb, and As were bound to OM, whereas the majority of Zn was bound with Fe/Mn oxides for all three SSs. Incubation of SS for 6 mo did not result in a substantial decrease in OM content or a change in the relative distribution of Cu, Zn, Pb, and As. Direct OM oxidation to 30 and 70% by diluted HO resulted in a significant decrease in organically bound Cu but increased its exchangeable, carbonate-bound, and Fe/Mn-bound fractions. Oxidation of OM slightly decreased organically bound Zn but significantly increased exchangeable Zn in all SSs. Oxide- and carbonate-bound Zn also decreased following OM oxidation. Exchangeable fractions of As and Pb were minute before and after OM degradation, indicating that release into the environment would be unlikely. The relative distribution of Cu, Zn, Pb, and As in SS-treated soils was similar to that of SS, suggesting a dominant role of SS properties in controlling metal distribution following OM oxidation. Overall, OM oxidation increased the mobility and bioavailability of Zn and Cu, whereas it had less impact on Pb and As.

Relationship between organic matter humification and bioavailability of sludge-borne copper and cadmium during long-term sludge amendment to soil

“…Accordingly, there are two theories regarding this regulation. One is known as the 'time-bomb' viewpoint, which indicates that the change in bioavailability of heavy metals in sludge accounted for the bondability of organic matter to different heavy metal fractions (Bergkvist et al, 2005;McBride, 2003;Stietiya and Wang, 2011). In this theory, the proportion of active fractions of heavy metal increases after sludge is recycled to soil as the sludge is gradually degraded.…”

“…It is generally believed that organic matter in sludge decreases with time after application to soil (Diagboya et al, 2015;Lu et al, 2014;Stietiya and Wang, 2011). This is a consequence of stabilization and humification (Fernández et al, 2007).…”

Achilles heel of environmental risk from recycling of sludge to soil as amendment: A summary in recent ten years (2007–2016)

“…Antoniadis et al (2007) stated that the potential for the long-term release of heavy metals from sludge should be considered when assessing the risks associated with amendment sludge to soil, particularly in climates in which organic matter is likely to be degraded quickly or slowly. Other researchers think that the inorganic fraction of sludge plays a decisive role in the release of heavy metals to soil, meaning that an invariable percentage of each heavy metal will potentially be released from sludge to amended soil (Stietiya and Wang, 2011). From the viewpoint of actual conditions, accumulated literature supports the conclusion that organic matter in sludge being amended to soil regulates heavy metal behavior far more strongly than does the inorganic fraction of the sludge.…”

Availability of Cu and Zn in an acidic sludge-amended soil as affected by zeolite application and liming

“…Sludgeadded metals are reported to be considerably less mobile in soil than metals derived from inorganic sources, due to the binding capacity of organic phases also added to soil with sludge application. For example, Stietiya and Wang (2011) found that 75% of Cu and 8% of Zn were bound onto organic phases and that with organic matter oxidation the percentages fall to <10% for Cu and <3% for Zn. Apart from the presence of sludge-borne organic chelates, the role of inorganic colloids has also been recognised, especially some time (months or years) after the last application of an organic waste (when, as reported by Benke et al 2008, it is expected that waste-added organic matter will have been decomposed to a great extent).…”