cadmium in cacao beans

7/26/2019 Cadmium in Cacao Beans

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The concentration of cadmium

(Cd) in Ecuadorian cacao: it

nexus with soil-Cd

Chavez E.1,2*

, He Z. L.1

, Baligar V. C.3

, Moyano B.2

, Mylavarapu R.4

,Li Y.5, Stoffella P1.1 Indian River Research and Education Center University of Florida-IFAS (Fort Pierce, FL)2Centro de Investigaciones Biotecnologicas del Ecuador ESPOL (Guayaquil, EC)3United State Department of Agriculture Beltsville Agricultural Research Center (Beltsville, MD)4Soil and water science department University of Florida (Gainesville, FL)5Tropical Research and Education Center University of Florida (Homestead, FL)

* Presenting author: [email protected]

XX Latin American Congress of Soil Science

Cuzco, Peru

November 2014


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Introduction

Cadmium (Cd) is one of the most concerned elements in

food safety and human health worldwide (Alloway, 2012). Cacao (Theobroma cacao, L.) is the main ingredient in

chocolate production, which is mostly consumed bychildren and women (Dahiya et al. 2005).

Cacao have been reported to accumulate excessive levelof Cd in beans (Mounicou et al. 2003).

The European Union established a critical level of 0.6 mgkg-1 of Cd in cacao beans and will be implemented by

2019 (ICCO, 2012).

At this point, there is no information regarding Cd levelsin Ecuadorian soils or cacao beans


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Introduction

Cacao is a widely plantedcrop in Ecuador withapproximately 500,000hectares (brown area inFigure).


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Objectives

To investigate the status of Cd in cacao

tissues and soil profiles in representativecacao farms.

To distinguish the source of contamination

based on the vertical distribution of Cd in soilprofiles.

To study available pools of Cd in soils undercacao production using single andsequential extraction methods.

To correlate the Cd in cacao beans andtissues with available Cd in soils


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Materials and Methods


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Material and Methods (cont) 19 fiel sites !ere selecte for t"is

stu# in sout"ern $cuaor, %ua#as

an $l &ro 'rovince Cacao leaves an 'os (beans, anbean)coating* !ere sam'le from

mature trees+

Camium in leaves an 'os totalconcentration (-N&. igestion*

Soil 'rofile (4 e't"s* 0)/, /)1/,1/).0 an .0 /0 cm+

Source of 'ollution e"lic" .

(.* an total recoverable ($PA.0/0*, '"#sical c"emical

'ro'erties

Available C ., 0+1 -Cl an 1

N-4&Ac, se3uential etraction (1/sites* (Amac"er, 1995*+ Soil an 'lant sam'ling in sout"ern $cuaor


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Material and Methods (cont)


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The accumulation of Cd in cacao beans and bean

coat from ! cacao farms in southern Ecuador

)0+/0

0+00

0+/0

1+00

1+/0

2+00

2+/0

.+00

.+/0

1

2

.

4

/

5

6

7

9

10

11

12

1.

14

1/

15

16

17

19

Cd

concentra

on

in

nibs

and

shell

(mg

kg-1

)

Field

sites

ean)C Coa ng)C

8e line re'resents C t"res"ol for cacao beans (0+5 mg g)1*+ :"e

concentration of C in cacao leaves !ere belo! t"e etection limit (;L*

of t"e e3ui'ment (0+1 mg L)1*


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"iscussion Concentrations of Cd in cacao beans ranged from 0.02

to 3.00 mg kg-1, with a mean value of 0.94 mg kg-1.

Twelve sites overpassed the critical level for cacaobeans.

The distribution of Cd in cacao tree decreased in theorder of beans > shell >> leaves. Cadmium was detectedin shells only when bean-Cd exceeded 1 mg kg-1

Elevated concentrations of Cd in cacao beans have beenreported previously (Zarcinas et al., 2004). However, inmost cases, Cd concentration has been reportedelevated in chocolate and cacao byproducts (Mounicou

et al. 2003; Dahiya et al., 2005; Yanus et al., 2014). This high Cd concentration in beans is carried along the

chocolate production chain, and this contamination mayjeopardize the sustainability of cacao farmers in

developing countries.


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The distribution of Cd in soil #rofiles under cacao#roduction

0 0+2 0+4 0+5 0+7 1 1+2 1+4 1+5 1+7

0)/

0)1/

1/).0

.0)/0

Soil

Cd

(mg

kg-1)

Sampie

depth

s

(cm)

.)$tractableC :otalrecoverable


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Diapositiva 10

H1 The font of text with the figure is too small.He,Zhenli, 09/11/2014


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Total recoverable and M$-extractable Cd

in re#resentative soil #rofile

0

0+2

0+40+5

0+7

1

1+2

1+4

1+5

0)/ /)1/ 1/).0 .0)/0

Cd

(mg

kg-1)

Depths

(cm)

Site

1

0

0+/

1

1+/

2

2+/

.

0)/ /)1/ 1/).0 .0)/0

Cd

(mg

kg

-1)

Depths

(cm)

Site

3

Site

20

Site

5

Site

16

0

0+/

1

1+/

2

2+/

.

0)/ /)1/ 1/).0 .0)/0

Cd

(mg

kg-1)

Depths

(cm)

0

0+/

1

1+/

2

2+/

0)/ /)1/ 1/).0 .0)/0

Cd

(mg

kg-1)

Depths

(cm)

Site

1

:otal

recoverable

.

etractable

0

0+/

1

1+/

2

2+/

0)/ /)1/ 1/).0 .0)/0

Cd

(mgkg-1)

Depths

0

0+2

0+4

0+50+7

1

1+2

1+4

1+5

0)/ /)1/ 1/).0 .0)/0

Cd

(mg

kg-1)

Depths


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"iscussion

Total recoverable and M3-extractable Cd was found tohave accumulated at the surface layers (0-15 cm), withan average concentration of 1.54 and 1.38 mg kg-1 for

total recoverable, and, 0.40 and 0.29 mg kg-1 for M3-extractable at the depth of 0-5 and 5-15 cm, respectively.Thirteen sites surpassed critical soil-Cd concentration innon-polluted soils (< 1.1 mg kg-1), therefore, areconsidered polluted (Kabata-Pendias, 2011)

The accumulation of Cd in upper layers suggestsanthropogenic activities as the source of contamination

in the studied area. In similar studies, the vertical distribution of a

contaminant has been used to assess the source ofpollution (Buccolieri et al., 2010, CaridadCancela et al.,

2005).


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Extractable Cd in the soils as estimated b%

three sin&le extraction methods

0

0+1

0+2

0+.

0+4

0+/

0+5

0+6

0+1

-Cl

.

1

N-4&Ac

!

"tractable

Cd

mg

kg-1

#ethods

a

a

b

c

0

0+1

0+2

0+.

0+4

0+/

0+5

0+6

0+1-Cl . 1N-4&Ac

!

"tractable

Cd

mg

kg

-1

#ethods

b

a

a

b

$tractable C at t"e 0)/ (a* an /)1/ cm e't" (b*, ifferent letters on

t"e to' of columns inicate significant ifference at /= level+


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'oil-Cd fractionation in cacao farms -* cm

de#th

0=

10=

20=

.0=

40=

/0=

50=

60=

70=

90=

100=

1 2 . 4 / 5 6 7 9 10 11 12 1. 14 1/

$ercentag

e

Sites

>ater soluble Aci)Soluble 8eucible &iizable 8esiual


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'oil-Cd fractionation in cacao farms *-* cm

de#th

0=

10=

20=

.0=

40=

/0=

50=

60=

70=

90=

100=

1 2 . 4 / 5 6 7 9 10 11 12 1. 14 1/

$ercenta

ge

Sites

>ater soluble Aci)Soluble 8eucible &iizable 8esiual


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Correlation coefficients (r) between soil

and tissue Cd

%omenclat&re' (-S ? >ater soluble C, )cid-Sol ? Aci)Soluble C, #3 ? e"lic" . )

etractable C,*Cl ? 0+1 -Cl etractable C,)) ? 1 N-4

&Ac etractable C,+, ?

total recoverable C+


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"iscussion

M3- and HCl-extractable Cd were strongly correlatedwith bean-Cd concentration at both the surface and

subsurface soil layers (0-5 and 5-15 cm), with similarcorrelation coefficients (r = 0.80 and 0.82 for M3, and r =0.78 and 0.82 for HCl; P< 0.0001). In comparison to M3and HCl extractable Cd, lower correlation coefficients

were obtained between total recoverable Cd and bean-Cd (r = 0.56 and 0.61; P < 0.05), and thus total Cdconcentration may not be the best predictor of Cdavailability in cacao beans.

In contrast, previous studies also suggested neutralsalts, which extract only water soluble and exchangeablemetals, as good predictors of plant-available Cd (Zhanget al., 2006; Meers et al., 2007)


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"iscussion (cont)

In summary, the distribution of Cd fractions decreased inthe following order: oxidizable > acid-soluble > residual >

reducible >> water soluble. Soil-Cd was largely bound to organic matter, 34 and 49%

for the 0-5 and 5-15 cm depth, respectively; however,this pool of Cd is not readily available for cacao plants.

Correspondingly, acid-soluble Cd (also known ascarbonate bound) accounted for 25 and 19% of total Cd,in contrast with oxidizable-bound Cd, this fraction isreadily available under acid conditions, such as in the

rhizosphere. In a similar study, Aikpokpodion et al. (2012) reported adecreasing order as follows: residual > oxidizable >water soluble > acid-soluble > reducible.


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Conclusions Twelve out of the nineteen studied farms had a bean

Cd concentration higher than the critical level (0.6 mgkg-1), attention should be paid to managementpractices to reduce Cd availability in soil since cacao

is an important commodity in Ecuador. Cadmium is highly accumulated in cacao beans, in a

lesser degree in beans coat and almost none inleaves. This phenomena might be linked to the uptake

of nutrients and waterof pods directly from the trunk. In thirteen sites, the concentration of soil-Cd

exceeded the pollution threshold (1.1 mg kg-1).Furthermore, Cd was mainly in the first 15 cm of thestudied soil profiles, this indicates the occurrence ofanthropogenic activities as the source of pollution inthe area.

The extraction power of Cd among the selectedmethodsdecreased in the following order: 0.1 M HCl

> M3 >> 1 M NH4OAc.


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Conclusions (cont)

The fractions of Cd in the soils decreased in order:oxidizable > acid-soluble > residual > reducible >>water-soluble/ exchangeable.

The concentration of Cd in beans was highlycorrelated with HCl and M3 extractable Cd in soil,

suggesting that these methods are suitable forpredicting plant-available Cd in the soils under cacaoproduction.

Acid-soluble Cd appears to be the labile pool of Cd insoil; this fraction was highly correlated with bean-Cd,HCl- and M3-extractable Cd. Therefore, managementpractices to avoid soil acidification should beimplemented to prevent the release of Cd into soilsolution.

The results of this study are applicable only to thesampling area and are not representative of thequality of Ecuadorian cacao.


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+eferences Amac"er, + 1995+ Nicel, Camium an Lea+


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,cnowled&ment

:"e 'resenting aut"or !ant to e'ress t"eir gratitue to t"e

Centro e


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T.,/0'

cadmium in cacao beans

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