Total and Extractable Nickel and Cadmium Contents in Natural Soils

This article was downloaded by: [Dicle University]On: 09 November 2014, At: 18:07Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH,UK

Communications in Soil Scienceand Plant AnalysisPublication details, including instructions forauthors and subscription information:http://www.tandfonline.com/loi/lcss20

Total and Extractable Nickeland Cadmium Contents inNatural SoilsRaquel Caridad‐Cancela a , Antonio Paz‐González a &

Cleide Aparecida de Abreu ba Facultad de Ciencias , Universidad de La Coruña ,A Coruña, Spainb Centro de Solos e Recursos Agroambientais ,Instituto Agronómico , Campinas (SP), BrazilPublished online: 05 Feb 2007.

To cite this article: Raquel Caridad‐Cancela , Antonio Paz‐González & CleideAparecida de Abreu (2005) Total and Extractable Nickel and Cadmium Contents inNatural Soils, Communications in Soil Science and Plant Analysis, 36:1-3, 241-252,DOI: 10.1081/CSS-200043057

To link to this article: http://dx.doi.org/10.1081/CSS-200043057

PLEASE SCROLL DOWN FOR ARTICLE

Taylor & Francis makes every effort to ensure the accuracy of all theinformation (the “Content”) contained in the publications on our platform.However, Taylor & Francis, our agents, and our licensors make norepresentations or warranties whatsoever as to the accuracy, completeness,or suitability for any purpose of the Content. Any opinions and viewsexpressed in this publication are the opinions and views of the authors, andare not the views of or endorsed by Taylor & Francis. The accuracy of theContent should not be relied upon and should be independently verified withprimary sources of information. Taylor and Francis shall not be liable for anylosses, actions, claims, proceedings, demands, costs, expenses, damages,

http://www.tandfonline.com/loi/lcss20

http://www.tandfonline.com/action/showCitFormats?doi=10.1081/CSS-200043057

http://dx.doi.org/10.1081/CSS-200043057

and other liabilities whatsoever or howsoever caused arising directly orindirectly in connection with, in relation to or arising out of the use of theContent.

This article may be used for research, teaching, and private study purposes.Any substantial or systematic reproduction, redistribution, reselling, loan,sub-licensing, systematic supply, or distribution in any form to anyone isexpressly forbidden. Terms & Conditions of access and use can be found athttp://www.tandfonline.com/page/terms-and-conditions

Dow

nloa

ded

by [

Dic

le U

nive

rsity

] at

18:

07 0

9 N

ovem

ber

2014

http://www.tandfonline.com/page/terms-and-conditions

Total and Extractable Nickel and CadmiumContents in Natural Soils

Raquel Caridad-Cancela and Antonio Paz-Gonzalez

Facultad de Ciencias, Universidad de La Coruna, A Coruna, Spain

Cleide Aparecida de Abreu

Centro de Solos e Recursos Agroambientais, Instituto Agronomico,

Campinas (SP), Brazil

Abstract: Trace element analysis in natural soil provides information on background

levels, which may be also useful to detect anthropogenic inputs. The main objective of

this study was to provide background levels of Cd and Ni for natural soils in Galicia

(Spain). Ten natural soil profiles, representative of different parent material with a

wide range of elemental composition, including ultramafic rocks such as serpentine,

were selected in this region. All samples were digested with nitric acid in a

microwave oven (U.S. EPA-SW 846 305 1 method) to assess “total” Cd and Ni

contents. Trace element extractions were carried out with diethylenetriaminepentaace-

tic acid (DTPA) and Mehlich-3. All analyses were performed by ICP-AES. Soil Cd

concentrations obtained by the U.S. EPA method ranged from ,0.01 to

4.42 mg kg21, with an average of 2.03 mg kg21, and Ni concentrations ranged from

12.66 to 2066 mg kg21 with an average of 156 mg kg21. The mean Ni content was

higher, because the used sample included a soil that was developed over serpentine.

The DTPA-and Mehlich-3-extractable Cd and Ni average levels were 0.06 and

8.78 mg kg21 and 0.16 and 3.57 mg kg21, respectively. Nickel levels obtained by

both extractants were highly correlated (r2 ¼ 0.91). A correlation analysis between

total and extractable Cd and Ni form, and soil general properties showed that the

highest significant dependence was for CdDTPA vs. organic matter content and CEC.

Address correspondence to Raquel Caridad-Cancela, Facultad de Ciencias,

Universidad de La Coruna, Campus de la Zapateira, s/n, A Coruna 15071, Spain;

E-mail: [email protected]

Communications in Soil Science and Plant Analysis, 36: 241–252, 2005

Copyright # Taylor & Francis, Inc.

ISSN 0010-3624 print/1532-2416 online

DOI: 10.1081/CSS-200043057

Dow

nloa

ded

by [

Dic

le U

nive

rsity

] at

18:

07 0

9 N

ovem

ber

2014

INTRODUCTION

Soil composition is extremely diverse and governed by many factors,

but climatic conditions and parent material are most predominant (1). The

element contents vary widely within soils, depending largely on the

geology. According to Oertel (2), there is a close relationship between the con-

centration of trace elements in a soil and its parent material. So, Cd is likely to

be concentrated in argillaceous and shale deposits, whereas Ni contents are

highest in ultramafic rocks. These concentrations decrease with increasing

acidity of rocks, so that, for example, in sedimentary rocks the highest

range is found in argillaceous rocks and the lowest in sandstones (1).

A review of the literature has revealed that the average content of total Cd

in soils is between 0.06 and 1.1 mg kg21, and the amount of total Ni ranges

from 20 to more than 2000 mg kg21 (1, 3).

The “normal concentrations” of trace elements in soils are of great

interest because background values are needed to assess the degree of soil con-

tamination (1). Furthermore, heavy metals in soils can have negative influence

on the food chain because of their potential toxic effects. Thus, it is necessary,

in natural soils, to provide a quantitative orientation of these elements through

background levels. The problem is to select the best analytical method, both

for “total contents” and “available contents” to obtain these values.

As trace elements, Cd and Ni are found in small concentrations in most of

the natural and agricultural soils. Moreover, both elements are not needed for

plant growth. However, when high soil concentrations of Cd and Ni occur, the

content of these element in the plant also increases (1, 3).

There are different methods of soil analysis that could be suitable to

obtain background levels. In our study, the U.S. EPA method (SW 846 305 1)

was applied (4) by using closed vessels and a microwave as a heating

source. This method has a fast digestion, therefore, eliminating the risk of

external contamination and loss of volatile elements (5). Nevertheless,

some extractants have been suggested to estimate availability for plants of

trace elements, the list of methods being extensive. For Cd or Ni, an officially

recommended extractant does not exist.

The complexity of soil chemistry and soil-plant relationships is probably

the main reason for the existence of so many soil-testing methods, which also

clearly demonstrate the lack of agreement on the best alternatives (6).

The DTPA and Mehlich-3, both multielement extractants, are commonly

used in the extraction of trace elements such as Fe, Cu, Mn, or Zn. Although

these methods are applied in numerous works (7–11), the effectiveness of

DTPA and Mehlich-3 for other elements such as Cd and Ni has not been

demonstrated.

The DTPA soil test has a sound theoretical basis, is inexpensive, reprodu-

cible, and easily adapted to routine laboratory procedures (12). Mehlich-3 (7),

considered to be an “universal extractant,” is being widely used. Numerous

R. Caridad-Cancela, C. A. de Abreu, and A. Paz-Gonzalez242

Dow

nloa

ded

by [

Dic

le U

nive

rsity

] at

18:

07 0

9 N

ovem

ber

2014

authors have recommended the use of Mehlich-3 because it not only extracts

simultaneously various nutrients but also it shows good correlations between

the amount extracted from the soil, the amount absorbed by the plant, and

crop’s response (9).

The main purpose of this article is to provide background levels of Ni and

Cd from natural soils in Galicia (Spain) and to determine the effect of parent

material on the abundance of these two metals in the soil. The effectiveness of

DTPA and Mehlich-3 in the evaluation of Ni and Cd availability was also

studied. The importance of soil properties in the behavior of these elements

has also been discussed.

MATERIALS AND METHODS

Ten natural soil profiles developed over different parent material were selected

for this study. A total of 38 samples from 10 soil profiles were taken from

several regions of the provinces of La Coruna and Lugo (Galicia, NW

Spain). These soils were chosen as representative of the geology in Galicia,

including granite, basic schist, granulite, serpentine, tertiary-quaternary

clays, amphibolite, coastal sediment, phyllite, and limestone (Table 1).

According to the taxonomic categories, the studied soils belong to

Umbrisols, Phaeozems, Gleysols, Fluvisols, and Leptosols (13).

After the collection, mixed samples were air-dried, and passed through a

2-mm sieve. Routine analysis of soil properties was determined, conforming

to accepted methods described in detail in Guitian and Carballas (14) and

MAPA (15). Soil pH ranged mainly between 4.47 and 8.67; however, pH

values .7.0 were only found in the surface horizon of profile No. 8

developed over coastal sediments and in profile No. 10 developed over

limestone (Table 1). As expected, profiles over granite showed the most

acidic conditions, but profiles over materials containing mafic minerals, and

even over serpentine, and ultramafic rock, were also acidic. Soil organic

matter content range for A horizons (including both A1 and A2 layers) was

between 1.5 and 26.5%, but for most samples it was .4%; for A/B, B, and

C horizons, this figure was between 0.38 and 5%. The minimum and

maximum clay contents were 9.10 and 32.66%, respectively. Higher

CEC values were found in surface A horizons (ranged from 6.77 to

46.58 cmolþkg21) with regard to subsoil A/B, B, and C horizons (ranged

from 3.88 to 18.88 cmol kg21) (16, 17).

The method adopted to assess “total” metal content was digestion by

nitric acid (U.S. EPA-SW 846-305 1). For analyses, 500 mg of each sample

were placed in a Teflon PFA digestion vessel, and 10 mL of concentrated

nitric acid were added. The vessels were capped and placed in a microwave

(CEM model MDS-2000) oven carousel in groups of six samples each

time (4, 18).

Total and Extractable Nickel and Cadmium Contents in Natural Soils 243

Dow

nloa

ded

by [

Dic

le U

nive

rsity

] at

18:

07 0

9 N

ovem

ber

2014

Table 1. Total and available Cd and Ni contents in studied soils (in mg kg21)

No. Parent material Depth (cm) CdEPA NiEPA CdDTPA NiDTPA CdM-3 NiM-3

1 Granite (0–12) 3.01 21.74 0.18 0.30 0.31 0.97

(12–50) 2.81 20.68 0.11 0.22 0.28 0.88

2 Basic schist (0–8) 1.77 55.81 0.11 4.09 0.15 1.92

(8–52) 1.65 40.07 0.02 0.29 0.09 0.58

(52–90) 1.55 44.56 ,0.01 ,0.01 0.16 0.26

(90–110) 1.76 46.16 ,0.01 0.04 0.09 0.28

(þ110) 1.91 48.58 ,0.01 0.06 0.03 1.90

3 Granulite (0–12) 1.67 105.26 0.05 3.79 0.15 2.31

(12–45) 1.04 176.04 0.04 1.35 0.09 1.18

(45–60) 1.15 203.02 ,0.01 0.40 0.04 0.67

(60–90) 1.41 210.01 ,0.01 0.12 ,0.01 0.59

(þ90) 1.35 155.49 ,0.01 ,0.01 0.07 0.60

4 Serpentine (0–8) 2.79 838.95 0.07 81.08 0.31 42.65

(8–35) 0.73 1101.1 ,0.01 143.31 0.20 39.90

(35–40) ,0.01 2066.1 ,0.01 61.43 0.09 22.99

5 Sediment (0–6) 2.00 20.34 0.08 0.90 0.18 1.23

(6–11) 2.14 12.66 0.08 0.33 0.19 0.62

(11–40) 2.18 13.53 0.03 0.06 0.11 0.54

(þ40) 1.75 13.74 0.03 0.11 0.06 0.51

6 Granite (0–4) 2.42 22.97 0.14 0.31 0.20 0.95

R.Carid

ad-C

ancela

,C.A.deAbreu

,andA.Paz-G

onzalez

244

Dow

nloa

ded

by [

Dic

le U

nive

rsity

] at

18:

07 0

9 N

ovem

ber

2014

(4–29) 2.22 20.86 0.02 0.12 0.07 0.36

(29–44) 2.39 24.38 ,0.01 ,0.01 0.09 0.43

(44–84) 1.43 25.93 ,0.01 0.05 0.09 0.22

(þ84) 2.14 22.10 ,0.01 0.06 ,0.01 0.46

7 Amphibolite (0–15) 1.60 48.27 0.05 0.43 0.15 0.75

(15–22) 2.07 53.98 ,0.01 0.16 0.13 0.74

(22–45) 1.61 52.59 ,0.01 0.01 0.04 0.50

(45–65) 1.89 38.77 0.02 0.02 0.03 0.43

8 Sediment (0–6) 2.06 40.18 0.13 0.99 0.41 1.47

(6–35) 2.19 41.12 0.03 0.86 0.31 1.14

(35–95) 2.09 39.89 0.05 0.81 0.23 0.87

(þ95) 1.72 39.41 0.12 2.06 0.23 1.19

9 Phyllite (0–4) 2.82 40.13 0.03 1.37 0.26 1.13

(4–23) 2.77 43.05 0.02 0.74 0.17 0.68

(23–45) 2.11 43.85 ,0.01 0.25 0.09 0.66

10 Limestone (0–18) 4.42 49.04 0.04 0.22 0.25 0.98

(18–40) 2.61 50.29 0.08 0.45 0.26 1.19

(þ40) 1.82 47.95 0.02 0.36 0.15 0.91

Mean 2.03 156.28 0.06 8.78 0.16 3.57

Minimum ,0.01 12.66 ,0.01 ,0.01 ,0.01 0.22

Maximum 4.42 2066.15 0.18 143.31 0.41 42.65

CV (%) 32.51 245.65 83.33 328.25 56.25 271.99

TotalandExtra

ctable

Nick

elandCadmium

Conten

tsin

NaturalSoils

245

Dow

nloa

ded

by [

Dic

le U

nive

rsity

] at

18:

07 0

9 N

ovem

ber

2014

The available Ni and Cd contents were determined both after extraction

with DTPA (19) and with Mehlich-3 (7) using the following procedures:

1. DTPA: 0.005 mol L21 DTPA, 0.1 mol L21 TEA (triethanolamine) and

0.01 mol L21 CaCl2 at pH 7.3. Soil volumes of 10 cm3 and 20 mL

DTPA solution were used for the extraction. The suspensions were

placed in polyethylene flasks covered with a plastic stopper and shaken

by horizontal-circular movements at 240 oscillations per minute for 2 hr.

The suspensions were then filtered, and nutrient concentrations were

measured.

2. Mehlich-3: 0.2 mol L21 CH3COOH, 0.25 mol L21 NH4NO3,

0.015 mol L21 NH4F, 0.013 mol L21 HNO3, and 0.001 mol L21 EDTA

adjusted to pH 2.5. Soil volumes of 5 cm3 with 50 mL of Mehlich-3

extractant were taken. The suspensions were placed in polyethylene

flasks covered with plastic stoppers and shaken by horizontal-circular

movements at 240 oscillations per minute for 5 min. After filtration, the

nutrient contents were determined.

All determinations were replicated two times. Both total and available

forms of Ni and Cd were analyzed by inductively coupled plasma emission

spectrometry (ICP-AES), Jobin Yvon JY 50-P model (18).

The resulting data were statistically treated. Linear correlation was used

to guarantee the dependence of Ni and Cd concentrations from general soil

properties and relationships between the different methods. The statistical

significance levels considered were p , 0.01 and p , 0.05 (20).

RESULTS AND DISCUSSION

Total Cd and Ni Content

The Cd and Ni total concentrations obtained by using the U.S. EPA method

are shown in Table 1. It is observed that the Cd concentrations in the

soils studied ranged from ,0.01 to 4.42 mg kg21, with an average of

2.03 mg kg21. The highest total Cd content was found in profile No. 10

(over limestone), where profile No. 4 (over serpentine) contained the lowest

total Cd. These results are in accordance with those in the literature (21),

where it is reported that ultramafic materials present lower Cd amounts than

limestone rocks.

To assess background levels of Cd in the soils studied, the values obtained

were compared with those reported by other authors (1, 3). Comparison with

other references may produce ambiguities in the evaluation because there are

differences in soil, parent material, and climatology among the various

countries and geological materials (22). Nearly all samples studied here


Dow

nloa

ded

by [

Dic

le U

nive

rsity

] at

18:

07 0

9 N

ovem

ber

2014

showed high total Cd values, higher than the range of 0.06–1.1 mg kg21

quoted in the literature for the natural soils (1). These results suggest the

existence of problems during the analysis in determining Cd content by the

U.S. EPA 3051 method, or that this method is not suitable to evaluate total

Cd content. This last statement is supported by data obtained for the same

samples using another method (acid extraction by HF). In this case, the

mean Cd concentration was 0.14 mg kg21 with a range of 0.07–

0.86 mg kg21, and these results were closer to those found in the literature.

For Ni, the range was 12.7–2066 mg kg21, with a mean of 156.3 mg kg21.

Taking into account that one profile (profile No. 4) in the set of samples was

developed over serpentine, Ni-rich parent material, it is not surprising that the

mean concentration is considered excessive. In this particular case, it is

assumed that high natural Ni levels could have phytotoxic effects, causing

unfavorable growth of vegetation. Nevertheless, the rest of the samples

showed Ni contents similar to those found in the literature (1, 3). The

results obtained by the U.S. EPA method for Ni, in general, are consistent

with those in the literature, including those for profile No. 4. This method

could be adequate for the determination of this element.

As expected, the results showed an important influence of parent material

on Cd and Ni content in the soils studied. Perhaps this factor should be con-

sidered when the objective is to provide background levels. Examination of

the coefficient of variation (CV) revealed a clear indication of the wide geo-

logical variability of the soils studied, mainly for Ni. Clearly, parent

material influences the amount of Ni present in the given soils.

In general, the patterns of distribution followed by total Cd decreased

with depth and howed an irregular distribution (considered when the

element neither accumulates at the surface or at a specific depth). The total

Ni content in the profile tends to increase with depth or remain relatively

stable, with the exception of the soil developed with limestone. Nevertheless,

the soil composition and parent material could have a significant role in the

distribution of Cd and Ni in the profile.

When the study was conducted according to soil groups (Table 2), few

significant differences were observed between them for total Cd, but for

Table 2. Total and available Cd and Ni contents by soil groups studied (in mg kg21)

Element Umbrisols Phaeozems Gleysols Fluvisols Leptosols

CdEPA 1.85 2.47 2.02 2.02 2.57

NiEPA 68.44 692.24 15.07 40.15 42.34

CdDTPA 0.07 0.05 0.06 0.08 0.03

NiDTPA 0.66 47.81 0.35 1.18 0.79

CdM-3 0.12 0.21 0.24 0.30 0.17

NiM-3 0.81 18.10 0.73 1.17 0.82


Dow

nloa

ded

by [

Dic

le U

nive

rsity

] at

18:

07 0

9 N

ovem

ber

2014

total Ni, the content in the samples analyzed was inherent to the geology. So,

the highest levels were found in profile No. 4, developed over ultramafic

material (serpentine), and classified as Phaeozems, whereas the lowest total

Ni contents were for Gleysols, developed over tertiary-quaternary clays,

followed by Fluvisols over coastal sediments.

DTPA and Mehlich-3 Extractable Cd and Ni Content

A summary of the DTPA and Mehlich-3 (M-3) extraction results for all

samples is shown in Table 1. The CdDTPA ranged form 0.01 to

0.18 mg kg21, with a mean value of 0.06 mg kg21. The highest CdDTPA

content was found in the more superficial sample of profile No. 1, which

was also richer in organic matter than the rest of the samples. Organic

matter content could have an important effect on the content of this form of

available Cd, taking into account that DTPA will extract preferentially

complexed metals for this soil property. The range in Cd extracted with

M-3 was ,0.01–0.41 mg kg21, with a mean value of 0.16 mg kg21. In all

the samples analyzed, M-3 generally showed a greater extraction capacity

than DTPA, and considering the mean values, differences between extractants

were translated as 2.66 times more Cd with M-3 than with DTPA. This result

was expected because the presence of acid reagents and chelates such as

EDTA im M-3 is thought to extract higher amounts of elements than DTPA.

When the analysis was conducted for Ni, the range obtained with DTPA

was ,0.01–143.31 mg kg21 with a mean value of 8.78 mg kg21, and

0.22–42.65 mg kg21 with a mean value of 3.57 mg kg21 for M-3. The

highest Ni concentrations were found in profile No. 4, with both DTPA and

M-3, and the lowest contents were observed in profiles No. 2, 3, and 6 with

DTPA, and in profile No. 6 with M-3.

Comparing the extraction capacity of DTPA vs. M-3, in most samples

M-3 extracted more Ni than did DTPA, which may be due to its acid

condition (pH 2.5). However, exceptions were seen in some samples

(e.g., in profile No. 4) over serpentine, where DTPA extracted more Ni

than M-3. Consequently, large differences are found for mean NiDTPA and

NiM-3values, DTPA extracting about 2.46 times the amount obtained by

M-3. Presumably, soil pH is the main factor that explains the Ni soil

content, because in samples with a more elevated pH, DTPA showed the

highest extractability. This finding could be related to the higher effectiveness

of this method at neutral or alkaline conditions (16, 17). If profile No. 4 was

considered in the calculation of the average, the extraction capacity of the M-3

method (0.86 mg kg21) resulted much better with regard to those of DTPA

(0.67 mg kg21), thus M-3 extracted 1.28 times more than DTPA.

With reference to CV for Cd and Ni extracted with DTPA and M-3, it is

noteworthy the high values found for Ni, CV giving values in the order of


Dow

nloa

ded

by [

Dic

le U

nive

rsity

] at

18:

07 0

9 N

ovem

ber

2014

328% (Table 1). The notable differences seen among the parent material of the

soils studied elevate the variability, especially in the case of Ni.

The results when evaluated according to soil groups (Table 2) showed that

elevated Cd concentrations were observed, both with DTPA and M-3, in

Fluvisols. High contents of available Cd in Fluvisols can be due to several

soil properties. According to the correlation coefficients values obtained in

Fluvisols, M-3 extracted Cd associated with organic matter (r ¼ 0.96) and

CEC with (r ¼ 0.98). With both extractants Phaeozems showed the highest

available Ni concentrations. Again, it is evident that parent material exerts a

strong effect on the available content of Ni, as quoted earlier for total Ni

content.

Available Cd and Ni contents followed the expected distribution in soil

profile, because, in general, in the 10 profiles studied, the highest amounts

were observed in the top layer, enriched with organic matter. These results

indicate that the same distribution trend observed for organic matter can be

shown for available Cd and Ni contents in the soils studied. Thus, an

important role of organic matter content on Cd and Ni dynamics between

the soil and plant is suggested.

The correlation of DTPA and M-3 was used to predict the relationship

between both extractants for the determination of available Cd and Ni in

the soils studied (Fig. 1). Both extractants behave differently for Cd, each

one extracting the Cd associated to different pools, as is reflected by the

low correlation coefficient obtained (r ¼ 0.33), despite it being significant

(p , 0.01). Nickel extracted by DTPA was highly correlated with that

extracted by M-3 (r ¼ 0.91). This good correlation suggests that both DTPA

and M-3 extract Ni from the same pool and that the two extractants can be

used to predict the available Ni contents in a given soil. The large

magnitude of variation for Cd and Ni extracted by DTPA or M-3 seems to

depend on the nature of soil parent material and in some cases on the soil pH.

Correlation Analysis Between Total and Available Cd and Ni

Content and Soil Properties

A correlation analysis was carried out between Cd or Ni contents, extracted by

the U.S. EPA method and by DTPA or M-3 and soil properties (Table 3). In the

case of total contents, both CdEPA and NiEPA were significantly correlated with

clay content. This relationship could be explained because the clay fraction has

exchangeable transition metal cations (mainly Cu, Fe, and Co) (1), and in

particular Ni has an ionic radii similar to Cu, Fe, or Co, suggesting that

isomorphic substitution can be produced in the clays.

When the relationship between available forms of Cd and Ni contents and

soil properties was studied, it was seen that CdDTPA correlated significantly

with organic matter content (r ¼ 0.70) and CEC (r ¼ 0.66), whereas NiDTPA


Dow

nloa

ded

by [

Dic

le U

nive

rsity

] at

18:

07 0

9 N

ovem

ber

2014

showed no significant correlation with selected soil properties. Using the

Mehlich-3 extractant, CdM-3 was significantly correlated with pH (r ¼ 0.47),

OM (r ¼ 0.59), and CEC (r ¼ 0.60), and NiM-3 was significantly correlated

with clay content (r ¼ 0.35) and CEC (r ¼ 0.33). This likely indicated that

Figure 1. Relationship between Cd and Ni extracted by DTPA and M-3.

Table 3. Correlation between total (U.S. EPA) and available (DTPA and M-3) Cd and

Ni content and selected soil properties (pH, clay content, organic matter content, and

exchange cationic capacity)

n pH Clay OM CEC

CdEPA 37 ns 0.32� ns ns

NiEPA 38 ns 0.34� ns ns

CdDTPA 24 ns ns 0.70�� 0.66��

NiDTPA 35 ns ns ns ns

CdM-3 36 0.47�� ns 0.59�� 0.60��

NiM-3 38 ns 0.35� ns 0.33�

ns, not significant.�p , 0.05; ��p , 0.01.


Dow

nloa

ded

by [

Dic

le U

nive

rsity

] at

18:

07 0

9 N

ovem

ber

2014

available Cd is mainly associated with the organic matter fraction, whereas

available Ni is controlled by clay content. The correlation of Cd and Ni

with CEC is a function of soil organic matter and clay content, so that

finding probably reflects the effect of both properties on Cd and Ni adsorption.

Let us summarize the above results. In the natural soils studied, it was

observed that total Cd and Ni contents were highly dependent on parent

material. The U.S. EPA method, specifically in the case of Cd, was not

suitable for obtaining background levels, but it was suitable for determining

Ni content.

In general, M-3 had a higher extraction capacity than DTPA, except for

samples with pH in the neutral or alkaline range. The extractant M-3 corre-

lated significantly with DTPA specially for Ni content.

Organic matter and clay content together with CEC are correlated with

different forms of Cd and Ni, which suggests an important role in the

dynamics of available Cd and Ni.

ACKNOWLEDGMENTS

This work was funded by Xunta de Galicia (Spain) in the frame of a soil

quality assessment project. Corrections and suggestions of two anonymous

referees are acknowledged with thanks.

REFERENCES

1. Kabata-Pendias, A. (2001) Trace Elements in Soils and Plants; CRC Press: BocaRaton, FL, 413.

2. Oertel, A.C. (1961) Relation between trace-element concentrations in soil andparent material. J. Soil Sci., 12: 119–128.

3. Alloway, B.J. (1995) Heavy Metals in Soils; Blackie Academic & Professional;368.

4. U.S. Environmental Protection Agency. Test Methods for Evaluation Solid Waste.Vol. IA: Laboratory Manual Physical/Chemical Methods, SW-846, 3rd ed.; U. S.Gov. Print. Office: Washington, DC, 1995.

5. Abreu, M.F., Berton, R.S., and de Andrade, J.C. (1996) Comparison of methods toevaluate heavy metals in organic wastes. Commun. Soil Sci. Plant Anal., 27:1125–1135.

6. van Raij, B. (1998) Bioavailable tests: alternatives to standard soil extractions.Commun. Soil Sci. Plant Anal., 29: 1553–1570.

7. Mehlich, A. (1984) Mehlich-3 soil test extractant: A modification of Mehlich-2extractant. Commun. Soil Sci. Plant Anal., 15: 1409–1416.

8. Sims, J.T. (1989) Comparison of Mehlich 1 and Mehlich 3 extractants for P, K, Ca,Mg, Mn, Cu and Zn in Atlantic Coastal Plain soils. Commun. Soil Sci. Plant Anal.,20: 1707–1726.


Dow

nloa

ded

by [

Dic

le U

nive

rsity

] at

18:

07 0

9 N

ovem

ber

2014

9. Garcia, A., de Iorio, A.F., Barros, M., Bargiela, M., and Rendina, A. (1997)Comparison of soil tests to determine micronutrients status in Argentina soils28: 1777–1792.

10. Rupa, T.R. and Shukla, L.M. (1999) Comparison of four extractants and chemicalfractions for assessing available zinc and copper in soils of india. Commun. SoilSci. Plant Anal., 30: 2579–2591.

11. Vale, R. and Martins, A. (1999) The availability of zinc, copper and manganese insoils in northeastern portugal, 6th International Meeting on Soils with Mediterra-nean Type of Climate, Barcelona, Spain, July 4-9; Bech, J., Ed.; Barcelona, Spain,1999.

12. O’Connor, G.A. (1988) Use and misuse of the DTPA soil test. J. Environ. Qual.,17: 715–718.

13. FAO. (1998) Food and Agriculture Organisation of the United Nations; WorldReference Base for Soil Resources: Rome, 161.

14. Guitian, F. and Carballas, T. (1976) Tecnicas de Analisis de Suelos; Pico Sacro:Santiago de Compostela, Espana; 288.

15. MAPA (Ministerio de Agricultura, Pesca y Alimentacion). Metodos Oficiales deAnalisis de Suelos y Aguas para Riego. In Metodos oficiales de analisis; TomoIII: Madrid, 1994; 205–285.

16. Cancela, R.C., Abreu, C.A., and Paz-Gonzalez, A. (2002) DTPA and Mehlich-3micronutrient extractability in natural soils. Commum. Soil Sci. Plant Anal., 33:2879–2893.

17. Caridad Cancela, R. (2002) Contenido de Macro-, micronutrientes, MetalesPesados y otros Elementos en Suelos Naturales de Sao Paulo (Brasil) y Galicia(Espana). Facultad de Ciencias. Universidad de La Coruna.

18. Abreu, M.F., Abreu, C.A., de Andrade, J.C. (2001) Determinacao de Fosforo,Potasio, Calcio, Magnesio, Enxofre, Cobre, Ferro, Manganes,Zinco, Nıquel,Cadmio, Cromo e Chumbo em Acido Nıtrico usando metodos US-EPA. InAnalise Quımica para Avaliacao da Fertilidade de Solos Tropicais; vanRaij, B., de Andrade, J.C., Cantarella, H., and Quaggio, J.A., Eds.; Instituto Agro-nomico de Campinas. (SP); 251–261.

19. Lindsay, W.L. and Norvell, W.A. (1978) Development of a DTPA soil test forzinc, iron, manganese and copper. Soil Sci. Soc. Am. J., 42: 421–428.

20. Lamotte, M. (1981) Estadistica Biologica. Principios y Aplicaciones, 5th ed.;Toray-Masson, S.A., Ed., 163.

21. Schachtschabel, P., Blume, P., Brummer, G., Hartge, H., and Schwertmann, U.(1992) Lehrbuch der bodenkunde; Enke, 491.

22. Casarini, D.C.P. (2000) Proposta de Valores de Referencia de Qualidade eIntervencao para Solos e Aguas Subterraneas no Estado de Sao Paulo. In AnaisII. Seminario Internacional sobre Qualidade de Solo e Agua Subterraneas:Proposta de Valores Orientadores para o Estado de Sao Paulo; CETESB: Brasil.


Dow

nloa

ded

by [

Dic

le U

nive

rsity

] at

18:

07 0

9 N

ovem

ber

2014

Documents

Total and Extractable Nickel and Cadmium Contents in Natural Soils