Manure Application and Cannabis Cultivation Influence on Speciation of Lead and Cadmium by Selective Sequential Extraction

Abstract

The contamination of agricultural soils by heavy metals is a worldwide problem. Degradation of organic matter (OM) from organic amendments used in the remediation of metal-contaminated soils leads to changes in soil chemical properties shortly after their addition, which may affect the soil metal distribution. The effects of four differing organic amendments on chemical forms of Pb and Cd in a contaminated soil were investigated in a pot experiment of control unamended soil and soils amended with dry cow and poultry manures (20 g CM or PM kg −1 soil), and cow and poultry manure extracts (2 g CME or PME kg −1 soil) cultured with cannabis sativa. After eight weeks, a sequential extraction scheme was used to fractionate soil Pb and Cd into soluble-exchangeable (Sol-Exch), organic matter associated (AOM), and carbonates associated (ACar) forms. The addition of animal manures and their extracts increased the DTPA-extractable Pb and Cd in soil significantly. Soil Pb and Cd in Sol-Exch fraction were increased by manure applications. Both Pb and Cd in AOM fraction were increased by application of manures and their extracts. This increase was more obvious for Pb in application of cow and poultry manure extracts. The ACar chemical forms of Pb and Cd were also increased by application of manures and their extracts. The increases of Pb and Cdin Acar fraction was noticeable in soils treated with cow manure. Soil cultivation with cannabis sativa increased available, Sol-Exch, and AOM chemical forms of Pb in soil significantly compared to control soil. However, soil Pb and Cd in ACar fraction were decreased significantly by cannabis cultivation. The effect of cannabis cultivation on all of the Cd chemical forms (except on Sol-Exch) was similar to the results of Pb chemical forms. Plant cultivation had no significant effect on Cd in Sol-Exch chemical form.

Time evolution of Pb(II) speciation in Pampa soil fractions

“…Some shortcomings have been distinguished: limited selectivity of the extractants, redistribution of elements among phases during extraction and limited comparability of data obtained by several investigators. Thus, in general, the accuracy of these procedures could be hampered due to overlay between fractions; nevertheless, they are considered to be useful and are actively applied in different soils and conditions (Rao et al, 2008;Torri and Lavado, 2008;Orroño and Lavado, 2009;Kabala et al, 2011;Garrido and Helmhart, 2012;Singani and Ahmadi, 2012). The successive steps are often assumed to remove the pollutant associated with a given soil component or fraction; however, due to the lack of complete knowledge of the soil composition, it is more appropriate to relate the fractions to the reactants employed giving an operational definition (Rao et al, 2008;Kabala et al, 2011).…”

Chelating Agents and Heavy Metal Phytoextraction

“…The increased SOC in turn increases the organo-metal complexes (Hesterberg et al 1993;Safari Sinegani and Ahmadi 2012). Tahmasbian and Safari Sinegani (2013) by analyzing the active fractions of heavy metals in a soil treated with chelating agents reported that the concentration of solubleexchangeable Pb and Zn reduced after the application of cow and poultry manure extract, while the concentration of organic-bound fraction of the metals increased.…”

“…Of the organic matters used to improve soil phytoextraction efficiency and soil fertility, manures and their extracts such as cow, sheep, and poultry manures and extracts are more common and used by many scientists (Safari Sinegani and Khalilikhah 2008Safari Sinegani and Ahmadi 2012;Tahmasbian Ghahfarokhi and Safari Sinegani 2013;Tahmasbian and Safari Sinegani 2014). Fresh organic matters such as manures contain soluble organic fractions being able to increase the solubility of metals shortly after adding to soil through the formation of organo-mineral complexes (Almas et al 1999).…”

Chelate-assisted phytoextraction of cadmium from a mine soil by negatively charged sunflower

“…In the no voltage treatment, Cd availability was markedly higher in soil NRS especially in PME and CME treatments, which maybe because of higher soil biological activity. Safari Sinegani and Ahmadi (2012) found that soil Pb and Cd in soluble and exchangeable fractions were increased by manure applications in cannabis cultivation. …”

“…In situ technologies are noninvasive techniques used to remove pollutants from soils (Pazos et al 2010). Phytoremediation is one of the in situ procedures, which has been applied by many scientists (Huang et al 1997;Kulli et al 1999;Cooper et al 1999;Safari Sinegani and Khalilikhah 2011;Safari Sinegani and Ahmadi 2012) and has received increasing attention as a cost-effective alternative to usual engineering-based remediation approaches . Only plants with high biomass and high metal uptake capacity are suitable for phytoextraction of contaminants from soils.…”