The Availability of Copper in Soils Historically Amended with Sewage Sludge, Manure, and Compost

Abstract

Metals in soils amended with sewage sludge are typically less available compared with those in soils spiked with soluble metal salts. However, it is unclear if this difference remains in the long term. A survey of copper (Cu) availability was made in soils amended with sewage sludge, manure, and compost, collectively named organic amendments. Paired sets of amended and control soils were collected from 22 field trials where the organic amendments had aged up to 112 yr. Amended soils had higher total Cu concentrations (range, 2-220 mg Cu kg ; median, 4 g kg) than control soils. All samples were freshly spiked with CuCl 2 , and the toxicity of added Cu to barley was compared between amended and control soils. The toxicity of added Cu was significantly lower in amended soils than in control soil in 15 sets by, on average, a factor of 1.4, suggesting that aged amendments do not largely increase Cu binding sites. The fraction of added Cu that is isotopic exchangeable Cu (labile Cu) was compared between control soils freshly spiked with CuCl 2 and amended soils with both soils at identical total Cu concentrations. Copper derived from amendments was significantly less labile (on average 5.9-fold) than freshly added Cu in 18 soils. This study shows that Cu availability after long-term applications of organic amendments is lower than that of freshly added Cu 2+ salts, mainly because of its lower availability in the original matrix and ageing reactions than because of increased metal binding sites in soil.

The effects of biochar and compost amendments on copper immobilization and soil microorganisms in a temperate vineyard

“…Gemmatimonadetes copies g À1 soil Control 4.8 Â 10 8 AE 6 Â 10 7 5.1 Â10 8 AE 7 Â 10 7 5.6 Â 10 8 AE 6 Â 10 7 4.5 Â 10 8 AE 3 Â 10 7 Biochar 3.6 Â 10 8 AE 4 Â 10 7 5.0 Â 10 8 AE 6 Â 10 7 4.9 Â 10 8 AE 7 Â 10 7 4.9 Â 10 8 AE 6 Â 10 7 Compost 5.5 Â 10 8 AE 5 Â 10 7 4.6 Â 10 8 AE 3 Â 10 7 6.6 Â 10 8 AE 9 Â 10 7 6.8 Â 10 8 AE 8 Â 10 7 Biochar-compost 4.7 Â 10 8 AE 5 Â 10 7 6.4 Â 10 8 AE 9 Â 10 7 5.9 Â 10 8 AE 5 Â 10 7 5.9 Â 10 8 AE 7 Â 10 7 seen in the lab and in this study a neutral soil pH in addition to organic matter, either as biochar, compost or plant biomass, may have led to similar levels of immobilization across all plots (Smolders et al, 2012;Ruyters et al, 2013). That ability of organic matter to bind with Cu is discussed in Section 4.2.…”

“…Moreover, it is possible that compost simply provided necessary substrates for bacteria to tolerate Cu, as their main Cu strategy is efflux pumps, which require large amounts of energy (Klein and Lewinson, 2011). However, Kostov and Van Cleemput (2001) and Smolders et al (2012) agree that the addition of organic matter has the potential to reduce the impact of Cu, but does not guarantee it even in soil with a neutral pH. This study found that microbial and chemical benefits from compost did not remain stable over time.…”

Zinc, copper and manganese availability in soils treated with alkaline sewage sludge from Paraná state (Brazil)

“…In Paraná, most of the sewage sludge is subjected to sanitization by a prolonged alkaline stabilization process (addition of lime aimed at raising the pH of the mixture to 12 and a curing period of 30 days) (Paraná, 2009). Thus, when applied to agricultural land, the alkaline sewage sludge has double action, it increases the soil pH (Berton;Poggere et al, 2012) and can be a micronutrients source (Smolders et al, 2012;Bittencourt et al, 2014). However, unlike mineral fertilizer, the chemical composition of sewage sludge is quite variable, which results in a high degree of uncertainty regarding the micronutrient supply.…”

“…The specific adsorption is one of the most important mechanisms for controlling Zn and Cu availability in soil. The Zn and Cu adsorption capacity varies depending on the texture, mineralogy, organic matter and pH (Arias et al, 2006;Casagrande;Soares;Mouta, 2008;Smolders et al, 2012), thus, the availability of these nutrients may vary from soil to soil. On the other hand, under natural acid soil condition the Mn usually has high availability, which may promote plants toxicity (Millaleo et al, 2010).…”

Metals Leak from Tilled Soil in a Century – A Review

“…depend on the degree of availability of the copper. Fresh copper that is added to old organically amended soil is less available in the next few days than fresh copper added to unamended soils (Smolders et al, 2012). The relative availability (amended/spiked) increases with the age of the amendment.…”