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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Sustainable Perennial Crops Laboratory » Research » Publications at this Location » Publication #317025
Title: Chemical speciation of cadmium: an approach to evaluate plant-available cadmium in Ecuadorian soils under cacao production

Author
item CHAVEZ, E - University Of Florida
item HE, H - University Of Florida
item STOFFELLA, P - University Of Florida
item Baligar, Virupax

Submitted to: Geoderma
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/2/2016
Publication Date: 2/15/2016
Publication URL: https://handle.nal.usda.gov/10113/63008
Citation: Chavez, E., He, H.E., Stoffella, P.J., Baligar, V.C. 2016. Chemical speciation of cadmium: an approach to evaluate plant-available cadmium in Ecuadorian soils under cacao production. Geoderma. 150:57-62.

Interpretive Summary: Cadmium (Cd) is one of the most plant-available elements in agricultural soils, minimal alterations in soils conditions greatly affect its mobility and availability. Cadmium poses a threat to food safety and human and plant health. Elevated concentration of cadmium (Cd) in cocoa beans has raised serious concerns about the safety of chocolate consumption. However there are no known association linking the forms of soil Cd and their availability and accumulation in cocoa beans. In this paper we report soil chemical fractionation analytical methods to identify various available Cd pools in the soils and to correlate these Cd pools with bean Cd concentration and soil test indexes at several sites in Ecuador. The results show that the distribution of soil Cd fractions decreased in the order: oxidizable > acid-soluble > residual > reducible >> water-soluble (+exchangeable). Acid-soluble fraction was more closely related to bean-Cd. Such information will help the farmers and researcher to select suitable chemical extraction method to identify the soils of cacao plantations that have high levels of plant available Cd. This information helps the farmers either avoid such areas for cacao cultivation or to find suitable amendments and management practices to reduce Cd bioavailability.

Technical Abstract: Elevated concentration of cadmium (Cd) in cacao beans has raised serious concerns about the safety of chocolate consumption. Accumulation of Cd cacao bean in southern Ecuador has been reported to relate soil contamination. In this study, soil fractionation was conducted to identify available Cd pools in the soils and to correlate these Cd pools with bean Cd concentration and soil test indexes. The distribution of soil Cd fractions decreased in the order: oxidizable > acid-soluble > residual > reducible >> water-soluble (+exchangeable). Oxidizable and acid-soluble fractions accounted for 59 and 68 % of the total recoverable Cd for the 0-5 and 5-15 cm depth, respectively. Acid-soluble fraction was more closely related to bean-Cd, with correlation coefficients (r) of 0.70 and 0.81 (P < 0.01) for the 0-5 and 5-15 cm depth, respectively. Acid-soluble Cd was significantly correlated with HCl- (r=0.9, P<0.01) or M3-extractable Cd (r = 0.98, P<0.01). These results indicate that acid-soluble Cd fraction is an important part of available Cd pool. Since approximately 60% of Cd in the cacao-growing soils is related to the acid-soluble fraction and bound to organic matter, remediation of the contaminated soils should pay attention to the dynamics of soil pH and organic matter content.