Lead and cadmium in wild birds in southeastern Spain

Pergamon Environmental Toxicology and Chemistry, Vol. 14, No. 12, pp. 2049-2058, 1995

Copyright 0 1995 SETAC Printed In the USA

0730-726W9.5 $9.50 i .OO

0730-7268(95)00157-3

LEAD AND CADMIUM IN WILD BIRDS IN SOUTHEASTERN SPAIN

ANTONIO JIJAN GARCIA-FERNANDEZ,*~ JOSE ANTONIO SANCHEZ-GARCIA,t

PEDRO JIMENEZ-MONTALBAN~ and AURELIO L U N A ~ ?Department of Veterinary Toxicology, School of Veterinary Medicine, University of Murcia,

Espinardo Campus, 30071 Murcia, Spain SCentro de Recuperacion de Fauna Silvestre “Ef Valle,” Regional Environmental Agency,

Autonomous Community of the Region of Murcia, Spain $Department of Legal Medicine and Toxicology, School of Medicine, University of Murcia,

Espinardo Campus, 30071 Murcia, Spain

(Received 21 February 1995; Accepted 3 1 May 1995)

Abstract-The main purpose of this study was to monitor exposure to lead and cadmium in wild birds in Murcia, a southeastern region of Spain on the Mediterranean coast. This region lies on one of the African-European flyways. Samples of liver, kidney, brain, bone, and whole blood from several species of wild birds were obtained during 1993. We found a clear relation- ship between cadmium and lead concentrations in birds and their feedings habits. Vultures (Gypsfulvus) had the highest concentrations of lead (mean 40 pg/dl in blood), and seagulls (Larus argentatus and Larus ridibundus) the highest concentrations of cadmium (mean 4.43 pg/g in kidney). Insectivores had high concentrations of both metals, and diurnal and nocturnal raptors showed the lowest tissue concentrations. The finding that tissue and blood concentrations were generally not elevated suggests environmental (rather than acute) exposure. Birds from more industrialized areas of the region studied here had higher concentrations of both lead and cadmium

Keywords- Cadmium Environmental exposure Lead

INTRODUCTION

Lead and cadmium are present in the environment mainly as a result of human activity [ 1,2]. Their influence on human and animal health has led to the development of many analytical procedures designed to determine the concentration of metals in different types of samples.

The measurement of lead and cadmium in avian tissues and blood is the best indicator of the degree and type of exposure, and is thus a useful means of monitoring environmental contamination [3-111.

Despite the opinion expressed by Furness and Greenwood [l I ] that concentrations of metals in blood reflect short-term exposure, these authors note that, to date, the only tissues suitable for the routine determination of cadmium in avian populations are liver and kidney. In previous studies of wildfowl, exposure to cadmium was not measured in blood, mainly because the low concentrations of this element are often below the limits of detection of commonly used techniques [12]. Moreover, it is often difficult to obtain sufficient amounts of wildfowl blood for analysis.

Cadmium and lead are usually measured by atomic ab- sorption spectrometry (AAS). Oehme and Lund [13] cau- tioned that the risk of systematic error of this method should not be underestimated. We slightly modified one of the methods described by these authors for the determination of lead, copper, and cadmium in samples of human blood with anodic stripping voltammetry (ASV), and we used this proce-

*To whom correspondence may be addressed.

Mediterranean area Wild birds

dure to measure lead and cadmium in samples of blood, liver, brain, bone, and kidney from wildfowl. We also provide detailed descriptions of the processes and methods used.

Earlier studies in other countries such as England [4], the United States [5,10,12], Ireland [S], Japan 191, France [14], and the Benelux region [15] have shown that diet, habitat, and proximity to urban and industrial centers condition the body burden of cadmium and lead in wild birds. In Spain, the effects of lead and cadmium in tissues have been investigated thus far only in humans [16,17]. The need for the present study lies in the lack of similar studies in Spain, to- gether with the ecological importance of southeastern Spain as an area on the major African-European flyway for mi- gratory birds.

METHODS

Sampling All birds used in this study were trapped live between

March and October 1993 by the staff of the El Valle Wild- life Recovery Center in Murcia (Spain), to be treated for frac- tures, malnutrition, or other problems. Blood samples only were taken from birds that had a favorable prognosis for recovery. Other birds were killed, and samples of blood and other tissues were obtained during necropsy.

Samples of whole blood, liver, brain, kidney, and bone were obtained with 1 h of death. The species were classified on the basis of feeding habits as insectivores ( n = 26), piscivores ( n = l l ) , diurnal ( n = 25) and nocturnal raptors ( n = 16), omnivores ( n = 8), and carrion feeders ( n = 6). Birds were trapped in four different areas characterized by differ-

2049

2050 A.J. GARCIA-FERNANDEZ ET AL.

ent sources of environmental pollution: city of Cartagena (industrial, mining,and seaport activities), city of Murcia (large city with a population of approximately 400,000), Vega del Rio Segura (rural area traversed by a severely contaminated river), and the rest of the region, which was considered an area of low environmental contamination.

Identification and quantification: Limits of detection We used a polarograph consisting of a VA-646 processor

and a VA-647 work station (Methrom, Switzerland). The working conditions are specified in the Appendix. Under the conditions described, we obtained peaks at -585 k 10 mV for cadmium, and at -380 k 10 mV for lead. Concentrations were measured with two standard additions per analysis in a constant volume of 100 pl, at a concentration that yielded 1.5- and 3-fold higher peaks than those given by the sample.

The limits of detection for each metal were determined by considering peak height as at least three times the value found in a purified water blank digested with the same procedure as that used for the samples. Standard dilutions of decreas- ing concentration were analyzed until we obtained responses below the preestablished minimum value. With this method, the limits of detection were 0.025 pg/L for cadmium, and 1.227 pg/L for lead.

Sample preparation for voltammetry Before ASV, all organic impurities that might interfere

with the results must be eliminated from the sample [13]. Complete digestion was ensured by using high-temperature digestion with a mixture of nitric, perchloric, and sulfuric acids (8: 8: I), followed by dissolution in tetradistilled purified water.

Sample preparation to ensure complete digestion involves a high risk of contamination. To avoid this, all reagents must be handled carefully, and disposables must be washed thor- oughly to obtain minimal baseline levels of cadmium and lead. We used Suprapur reagents (Merck, Darmstadt, Ger- many). To dilute the digestion extract, we used tetradistilled purified water. The addition standards were prepared from dilutions made with Sigma (St. Louis, MO) standard solutions of lead and cadmium.

Samples were digested with a thermostated apparatus equipped with 10 to 450°C temperature control and an alu- minum heating block with a capacity for sixty 10-mm diam- eter tubes.

The quartz digestion tubes measured 10 x 100 mm and had a volume of approximately 5 ml. Before use they were washed with 2% nitric acid for 48 h, then rinsed twice with tetradistilled water, and dried in an oven at 100°C.

The tips of the micropipettes and the containers for the standard solutions were washed in accordance with the rec- ommendations of Oehme and Lund [ 131.

All precautions were taken at each step of the process to avoid contamination from the laboratory environment (clean- air work station and fume hood were used).

Procedure A sample of blood (250 pl) or tissue (0.2 to 0.3 g) was

placed in a quartz tube, and 0.5 ml of a mixture of nitric:perchloric: sulfuric acid was added. Thermal digestion was done

by raising the temperature from 100 to 200°C at a rate of 5"C/5 min, followed by digestion for 2 h at 200"C, and a fur- ther temperature increase to 370°C at a rate of 20"C/5 min; this temperature was maintained until complete dryness was obtained. The sample was allowed to cool, and 100 pl hydro- chloric acid was added as the support electrolyte. Finally, the sample was redissolved in tetradistilled, purified water, and 10 ml was placed in an electrolytic cell. The p H of the final solution was between 1 and 2.

Recovery and reproducibility To calculate percentage recovery, we processed 10 sam-

ples of each tissue, which had been spiked with known amounts of the internal standard. Mean recoveries ap- proached 97% for both cadmium and lead; recovery was lowest from bone tissue (approximately 80%). To determine the linearity of recovery, we analyzed European Economic Community (EEC) reference standards for cadmium and lead [ 181 in triplicate. Lyophilized blood was reconstituted in accordance with the accompanying instructions. Results are summarized in Table 1.

Reproducibility, determined by analyzing 10 identical samples of reconstituted lyophilized blood (CRM 195), was 97.92 & 3.42% for cadmium, and 98.16 f 1.03% for lead.

Data analyses Mean concentration, standard deviation, and range were

calculated for each group that shared feeding habits, and for each area where birds were collected. Comparisons of the means were used to search for significant differences between feeding groups or sampling areas. Statistical tests were per- formed with a MICROSTAT standard statistical package (Ecosoft) using an analysis of variance (one-way) ANOVA 1; previous confirmation of normal distribution was done using Agostino's test. We used Student's t tests for indepen- dent samples.

Because comparisons between groups of birds with shared feeding habits was previously shown to be a valid method for monitoring environmental alterations [ 1 11, we established six feeding groups. The insectivore group consisted of Apus apus, Caprimulgus europaeus, Upupa epops, Sylvia borin, and Sturnus vulgaris; piscivores were Egretta garcetta, bubulcus ibis, and Ardea cinerea; diurnal raptors were Buteo buteo, Falco tinnunculus, Accipiter nissus, Hieraaetuspen- natus, and Hieraaetus fasciatus; nocturnal raptors were

Table 1. Recovery tests for three lyophilized blood materials with known element concentrations [18]

Metal Certified value Quantity found Recovery and standard (PLg/L) ( P d L ) (OJo)

Cadmium CRM 194 0.5 + 0.1 0.53 rt 0.12 106.00 CRM 195 5.37 rt 0.24 5.30 k 0.30 98.72 CRM 196 12.4 + 0.5 11.3 rt 0.8 91.13

CRM 194 126 rt 4 124 rt 3 98.41 CRM 195 416 + 9 421 rt 9 101.20 CRM 196 772 -+ 11 761 + 12 98.58

Lead

Lead and cadmium in Mediterranean wild birds 205 1

Athene noctua and Bubo bubo; omnivores were Lams argentatus and Lams ridibundus; Gyps fulvus was the only species in the carrion feeder (scavenger group)

For purposes of comparison, the birds were also classified according to the area where they were obtained.

Because of the feeding habits of the laughing gull (L. ridibundus), a species that frequents dumps and garbage heaps, and because we were not able to obtain specimens from all four areas of contamination, data for this species were not used in comparisons of the mean values for each area. Tis- sue concentrations of lead (one specimen only) and cadmium were much higher than in all other species.

RESULTS AND DISCUSSION

We agree with Goede and De Voogt’s charge [I51 that comparisons of the findings across studies are hindered by the fact that many of the findings on the determination of metals in tissues and blood of wildfowl underestimate the importance of detailed description of the analytical procedures and instrumental conditions used for analysis. The low concentrations (especially of cadmium) in brain and blood are below the limits of detection of some techniques [12,19] and therefore cannot be measured. We perfected an analytical technique for measuring, in whole blood and tissues, concentrations of cadmium and lead below the detection limits reported by other authors. The positive correlations between blood and liver cadmium ( r = 0.878) and between blood and renal cadmium ( r = 0.833) show that blood cadmium concentration may be a useful indicator of the degree of exposure to this metal, but a definitive answer to this question would require experimental studies with captive animals.

Because some species of wildfowl are uncommon or in danger of extinction, they are protected by law. We were thus unable to obtain large samples of some species investigated here. Nonetheless, we believe our data are of interest because of the value of wildfowl as monitors of ecological change [ I 11, and because of the technical specifications used in our analyses. Previously, we have studied the influence of the wildfowl’s state of health in our results. We found no significant differences by this factor.

Tissue concentrations of lead and cadium varied widely among individuals in each group. Seasonal changes appear not to have been the cause of this variability, as the entire region of Murcia is characterized by a relatively stable Med- iterranean climate. The only sharp change in temperature oc- curs from November to February; no birds were collected during this period. A possible explanation for some of the variation in the concentrations of metals is the grouping on the basis of feeding habits, which meant that data from many species were pooled [5,14]. Liver and kidney concentrations of cadmium and lead have been found in magnitudes ranging from pg/kg to pg/g. The values we found were comparatively low, and were probably due to dietary characteristics and local atmospheric contamination [20,21].

Feeding habits Furness and Greenwood [ I 11 noted that analyses of spec-

imens with common feeding habits can be useful in monitoring ecological change. We analyzed data from different feeding groups for three reasons. First, food consumption

is the main route of metal intake by organisms. Second, feeding habit, which is closely linked to systematic classification and habitat, is one of the features best defining a group of birds. Third, the content of contaminants in foods is closely related to environmental pollution.

Lead and cadmium concentrations in tissues and blood for specific species are presented in Tables 2 and 3, respectively.

Lead Mean concentrations of lead in blood were highest in car-

rion feeders (the griffon vulture, Gpys fulvus), followed by piscivores. The high concentration of lead (20 to 50 pg/dl, mean 37.9 pg/dl) in blood from vultures was above the reported sublethal or lethal dose in wildfowl [6,10,22,23]. Al- though vultures are considered falconids, they feed mainly on carrion, a source of food that is liable to contain contaminants. Species that consume sick or injured individuals, or that scavenge from garbage and carrion, are more likely to ingest lead shot and highly contaminated viscera [14]. The elevated blood levels of lead in vultures indicate recent exposure to large amounts of this metal [9,12,24-281. In the region of Murcia, this species frequents rural areas far removed from human activity, so the most likely origin of the concentrations of lead we found is contaminated viscera, rather than environmental sources.

Gulls (omnivores) had the highest mean concentrations of lead, the difference between gulls and all other groups be- ing statistically significant (Table 4). The only exception to this finding was bone tissue, in which the small number of samples prevented the difference from reaching significance. When the specimen with highest concentrations was eliminated from the analyses, omnivores still had significantly higher renal lead than did diurnal ( T = 1.9502, p = 0.0308) and nocturnal ( T = 2.1254, p = 0.0228) raptors; and significantly higher brain lead in comparison with all other groups (vs. insectivores, T = 3.1563,~ = 0.00177; vs. piscivores, T = 1.9305, p = 0.0357; vs. diurnal raptors, T = 3.1722, p = 0.00174; vs. nocturnal raptors, T = 2.1135, p = 0.0233). Feeding habits of gulls may limit their use as monitors of environmental contamination. Although fish make up a large part of their diet, these species cannot be considered piscivores, because they also scavenge from dumps and garbage heaps, i.e., sites where urban contaminants are highly con- centrated. However, data from carrion feeders and omnivores, if treated with suitable care, can provide important information and should not be excluded from attempts to monitor environmental contamination. Gulls have proven to be valuable indicators of organic chemical contamination [29,30]. These differences concerning the dietary behavior could explain the controversies about the efficiency of these species as indicators of environmental contamination.

After omnivores, insectivores had the highest mean concentrations of lead in liver tissues; this difference reached significance in comparison with nocturnal raptors and piscivores. Mean concentrations in kidney were also highest in insectivores, reaching significance in comparison with diurnal and nocturnal raptors (Table 4). The invertebrates these birds feed on accumulate large amounts of lead. Grue et al. [31] found high concentrations of lead in starlings (Sturnus vulgaris) and in the roadside invertebrates that made up their


diet. Among the insectivores we studied, the highest concentrations of lead in liver and kidney tissues were found in nighthawks (Apus apus) and grey goatsuckers (Caprimulgus europaeus) from the urban areas of Murcia and Cartagena. Because of the feeding habits and habitat preferred by these species, the high levels of lead in their tissues may have been due to atmospheric contamination from gasoline exhaust

fumes, as the metals in this contaminant accumulate in in- sect tissues.

Mean concentrations of lead in piscivores, which inhabit mainly continental wetlands in the region we studied, do not appear to indicate a high degree of contamination. However, three herons had blood concentrations of lead above 20 pg/dl. Continental waters in the region of Murcia receive industrial

Table 2. Concentrations of lead in tissues and blood of wild birds from southeastern Spain classified on the basis of feeding habits, March to October 1993

Lead concentrations"

Bird speciesb Liver' Kidney' Brain' Bone' Bloodd

Insectivores

Apus apus

Caprimulgus europaeus

Upupa epops

Sylvia borin Sturnus vulgaris

Piscivores

Egretta garcetta

Bubulcus ibis Ardea cinerea

Diurnal raptors

Buteo buteo

Falco tinnunculus

Accipiter nissus

Hieraaetus pennatus

Hieraaetus fasciatus

Nocturnal raptors

Athene noctua

Bubo bubo

Omnivores

Larus argentatus

Larus ridibundus

Scavengers

Total Gyps fulvus

0.32 f 0.21 (26)

0.43 f 0.19 (12)

0.40 k 0.28 (5) 0.08-0.75 0.11 (4) 0.06-0.19 0.06 (1) 0.16 (4)

0.06-0.75

0.12-0.71

0.08-0.21 0.20 f 0.14 (11) 0.04-0.49 0.17 (2) 0.12-0.21 0.27 (1) 0.20 f 0.15 (8) 0.04-0.49 0.29 * 0.34 (25) 0.02-1.24 0.11 f 0.06 (5) 0.02-0.18 0.20 f 0.13 (13) 0.05-0.45 0.26 (3) 0.12-0.45 0.81 (4) 0.44- 1.24

0.17 & 0.12 (16)

0.13 f 0.08 (9)

0.22 f 0.15 (7)

1.19 * 2.64 ( 8 )

0.26 & 0.11 (6)

0.03-0.50

0.03-0.29

0.03-0.51

0.13-7.73

0.13-0.45

0.26-7.73 3.99 (2)

0.35 & 0.74 (86) 0.02-7.73

0.61 k 0.64 (20)

0.55 k 0.20 (10) 0.13-2.40

0.13-0.78 1.55 (3) 0.16-2.40 0.21 (3) 0.17-0.26 0.25 (1) 0.40 (3) 0.23-0.54 0.29 f 0.28 (10) 0.04-0.81 0.16 (2) 0.12-0.19 0.71 (1) 0.27 k 0.28 (7) 0.04-0.81 0.28 k 0.20 (22)

0.15 f 0.07 (5) 0.10-0.28 0.29 k 0.20 (1 1)

0.39 (3)

0.38 (3) 0.30-0.40

0.02-0.77

0.08-0.56

0.16-0.77

0.23 f 0.18 (16)

0.16 f 0.09 (9)

0.32 & 0.23 (7)

1.68 * 3.28 (8) 0.56 f 0.56 (6)

0.03-0.67

0.05-0.30

0.03-0.67

0.13-9.70

0.13-0.54 5.03 (2) 0.35-9.70

0.50 rt 0.62 (76) 0.02-9.70

0.07 f 0.04 (26)

0.07 f 0.03 (12)

0.09 f 0.04 (5)

0.02-0.15

0.03-0.12

0.05-0.15 0.09 (4) 0.03-0.15 0.03 (1) 0.03 (4) 0.02-0.04 0.08 rt 0.05 (11) 0.007-0.14 0.03 (2)

0.13 (1) 0.09 f 0.04 (8) 0.03-0.14 0.06 f 0.05 (25)

0.02 k 0.004 (5) 0.02-0.03 0.05 rt 0.03 (13) 0.01-0.12

0.02-0.15

0.007-0.05

0.006-0.19

0.10 (3)

0.09 (4) 0.006-0.19

0.09 f 0.07 (16) 0.014-0.22 0.07 f 0.04 (9) 0.01-0.12 0.14 f 0.08 (7) 0.03-0.22 0.77 k 1.34 (8) 0.07-3.94 0.36 f 0.44 (6) 0.07-1.23 2.03 (2) 0.11-3.94

0.14 & 0.34 (86) 0.006- 3.94

7.84 k 16.26 (16) 1.71-54.00

1.71-9.10 8.95 (3) 3.20- 17.64

4.20 f 2.53 (8)

2.00 (2) 1.70-2.30

20.30 (3) 3 .OO-54.00 9.52 f 15.65 (8) 0.51-39.00 0.70 (2) 0.70-0.70

12.46 f 14.32 (6)

2.76 f 3.29 (16) 0.5 1-39.00

0.64-12.00 1.90 (4) 0.90-2.50 2.74 f 3.53 (9) 0.64-12.00 3.60 (3) 2.30-5.60

8.47 * 14.48 ( 8 )

2.43 f 2.18 (5) 0.5 1-43.00

0.51-6.00

0.62-43.00 18.54 (3) *

25.2 (3)

25.2 (3) 3.9-38.1

3.90-3 8.10

4.07 (3) 3 .OO-5.70

4.07 (3)

15.75 rt 9.10 (8) 3 .OO-5.70

5-25 15.00 (2) 5.00-25 .OO

16.00 f 6.67 (6)

12.10 f 6.58 (16)

11 .so (4)

6.50-25.00

4 .OO-26 .OO

5 .OO-26.00

5 .OO- 17 .OO 11.52 f 5.20 (8)

8.75 (2) 4.00- 1 3.50 18.00 (2) 15 .OO-21 .OO 8.20 rt 5.60 (8) 3 .oo-20.00

4.80- 13 .OO 8.32 & 6.68 (5) 3.00-20.00

7.93 (3)

37.9 k 12.1 (6) 20.0-50.0

7.56 k 12.40 (51) 14.6 f 12.3 (41) 0.51-54.00 3.0-57.0

'Mean rt SD (n) , and range. Standard deviation calculated when n 2 5. A blank indicates calculation not possible or no analysis. bBird species have been classified on the basis of feeding habits in southeastern Spain. 'Measured in pg/g of tissue (wet wt.). dMeasured in pg/dl.

Lead and cadmium in Mediterranean wild birds 2053

and urban wastewaters that contain amounts of heavy metals far in excess of authorized concentrations [32].

Diurnal and nocturnal raptors had lower concentrations of lead, probably because these species inhabit areas where human activity is scarce. Our data are similar to figures for raptors in France [14]. Two specimens of diurnal raptors in

the present study had blood and/or liver levels of lead that were considerably higher than those found in the rest of the diurnal raptors examined. Radiographic examination detected between 20 and 30 lead shot in their tissues, as a result of gunshot wounds. These birds nonetheless had survived for several months. According to O'Halloran et al. [8], birds

Table 3. Concentrations of cadmium in tissues and blood of wild birds from southeastern Spain classified on the basis of feeding habits, March to October 1993

Cadmium concentrationsa

Bird species' Liver' Kidney' Brain' Bone' Bloodd

Insectivores

Apus apus

Caprimulgus europaeus

Upupa epops

Sylvia borin Sturnus vulgaris

Piscivores

Egretta garcetta

Bubulcus ibis Ardea cinerea

Diurnal raptors

Buteo buteo

Falco tinnunculus

Accipiter nissus

Hieraaetus pennatus

Hieraaetus fasciatus

Nocturnal raptors

Athene noctua

Bubo bubo

Omnivores

Larus argentatus

Larus ridrbundus

Scavengers

Total Gyps fulvus

0.17 rt 0.15 (26) 0.03-0.61 0.17 t 0.16 (12) 0.06-0.61 0.24 rt 0.19 (5) 0.07-0.53 0.07 (4)

0.17 (1) 0.186 (4)

0.06-0.09

0.038-0.362 0.20 t 0.23 (1 1) 0.01-0.61 0.06 (2)

0.05 (1) 0.05-0.07

0.25 f 0.25 (8)

0.08 -t 0.09 (25) 0.01-0.61

0.002-0.35 0.026 * 0.022 (5) 0.003-0.052 0.12 t 0.11 (13)

0.091 (3) 0.002-0.353

0.063-0.12 1 0.013 (4) 0.003-0.019

0.09 k 0.10 (16)

0.052 t 0.066 (9)

0.141 f 0.137 (7)

0.72 k 1.19 (8)

0.08 f 0.04 (6)

2.65 (2)

0.002-0.38

0.008-0.200

0.002-0.380

0.04-2.93

0.04-0.14

2.37-2.93

0.18 +- 0.45 (86) 0.002-2.93

0.84 rt 1.39 (20) 0.09-4.70 0.50 f 0.34 (10)

1.92 (3)

0.18 (3)

0.28 (1) 1.73 (3)

0.09-0.96

0.33-4.70

0.09-0.32

0.57-4.00 0.41 f 0.52 (10) 0.01-1.60 0.13 (2)

0.07 (1) 0.52 k 0.60 (7)

0.04-0.22

0.01-1.60 0.27 c 0.44 (22) 0.01-1.92 0.07 5 0.04 (5) 0.024-0.120 0.43 -c 0.58 (11)

0.25 (3)

0.03 (3)

0.01-1.92

0.16-0.37

0.01-0.05

0.15 -+ 0.16 (16) 0.01-0.51 0.10 t 0.11 (9) 0.01 -0.34 0.21 t 0.19 (7)

4.43 f 7.89 (8)

0.19 f 0.08 (6)

17.2 (2)

0.01-0.51

0.05- 18.20

0.05-0.26

16.2- 18.2

0.84 t 2.75 (76) 0.01-18.20

0.016 t- 0.023 (26)

0.004 10 .0006 (12)

0.02 f 0.03 (16)

0.026 f 0.037 (8) 0.002-0.150 NDe-0.1 1

0.003-0.005 0.06 f 0.03 (5) 0.04-0.1 1 0.005 (4)

0.03 (1) 0.03 (4)

0.051 k 0.085 (11)

0.003-0.007

0.01-0.05

0.003-0.250 0.014 (2) 0.01 1-0.017 0.010 (1) 0.066 +- 0.096 (8) 0.003-0.250 0.017 k 0.020 (25) 0.001-0.080 0.005 t 0.002 (5) 0.002-0.008 0.024 + 0.024 (13) 0.00 1 -0.080 0.022 (3) 0.010-0.034 0.003 (4) 0.002-0.004

0.009 k 0.009 (16)

0.007 rt 0.005 (9) 0.001 -0.030

0.002-0.016 0.012 t 0.011 (7) 0.001 -0.033 0.072 f 0.118 (8)

0.021 rt 0.014 (6) 0.002-0.360

0.002-0.045 0.23 (2) 0.10-0.36

0.025 f 0.051 (86) 0.001-0.360

ND-0.11 0.009 (3) 0.006-0.0 12 0.007 (2) 0.006-0.008

0.023 (3) ND-0 .04 0.01 f 0.02 (8)

0.002 (2) ND-0.06

ND-0.004

0.013 k 0.023 (6) ND-0.06 0.02 -t 0.02 (16) ND-0.06 0.003 (4) ND-0.008

ND-0.058 0.021 t 0.020 (9)

0.05 (3) 0.038-0.063

0.008 f 0.013 (8) N D-0 .04

ND-0.04 0.004 (3) ND-0.007 0.017 (3) ND-0.047 0.017 (3) ND-0.047

0.01 f 0.01 (5)

0.017 rt 0.020 (51) ND-0.110

0.12 (3) ND-0.20

0.12 (3) ND-0.20 0.21 f 0.06 (8) 0.12-0.28 0.19 (2) 0.15-0.23

0.22 t 0.06 (6)

0.12 f 0.06 (16) 0.12-0.28

0.01-0.25 0.09 (4) 0.06-0.12 0.14 rt 0.06 (8) 0.07-0.25

0.11 (2) 0.10-0.12 0.09 (2) 0.01-0.17 0.09 f 0.08 (8) ND-0.28

ND-0.12

0.04-0.28

0.08 (3)

0.10 t 0.01 (5)

0.11 t 0.08 (6) 0.01-0.20 0.13 k 0.07 (41) ND-0.28

aMean rt SD (n), and range. Standard deviation calculated when n 2 5. A blank indicates calculation not possible or no analysis. 'Bird species have been classified on the basis of feeding habits in southeastern Spain. 'Measured in pg/g of tissue (wet wt.). dMeasured in Fg/dl. eND, no concentration detected.

Table 4. Results of Student’s t test for comparison of means ~~~

Cadmium Lead Comparisons

of groups Liver Kidney Brain Bone Blood Liver Kidney Brain Bone Blood

Ins vs. Pis 1.6956 (35)= 0.0486

-1,7230 (35) 0.0476

Ins vs. Diur 2.4535 (40) 0.0093

2.4630 (34) 0.0095

2.5597 (49)

1.8064 (40) 0.0068

0.0392

0.0116 -2.3831 (32)

2.2439 (34) 0.0157

2.0326 (40)

2.2068 (34) 0.0244

0.0171

0.0262 -2.0325 (26)

Ins vs. Noct

Ins vs. Omn

2.397 (40) 0.0106

0.046 -1.737 (32)

-1.7845 (40)

-2.7769 (32) 0.0410

0.0045 Ins vs. Scav Pis vs. Diur 2.0088 (22)

0.0285 2.2368 (14)

0.0210

1.9406 (34)

1.9897 (25) 0.0303

0.0288

3.5538 (22)

3.2469 (14) 0.0029

8.89 x 1 0 - ~ Pis vs. Noct

E 1.7386 (24) 0.0475

Pis vs. Omn

Pis vs. Scav

Diur vs. Noct

-1.7569 (17) 0.0490

-3.7846 (12) 0.0013

3.1524 (12) 0.0042

-2.073 (39)

-2.7564 (31) 0.0224

0.0049 -1.7391 (31)

0.0960 Diur vs. Omn -2.0554 (28)

0.0246 -2.7614 (31)

0.0048 -1.7401 (31)

0.0458 Diur vs. Scav

Noct vs. Omn

Noct vs. Scav

-5.9936 (20) 3.67 x

- 1.8059 (22) 0.0423

-2.0557 (22) 0.0259

-2.1463 (22) 0.0216

-2.2218 (22) 0.0184

-5.5029 (12) 6.78 x 1 0 P

Groups: Ins, insectivores, Pis, piscivores; Diur, diurnal raptors; Noct, nocturnal raptors; Omn, omnivores (gulls); Scav, scavengers (vultures). A blank indicates calculation not possible or no difference statistically significant.

aResults of student’s d test (degrees of freedom in parentheses), followed by resulting values of p .


carrying up to six shot embedded in their tissues did not have raised blood concentrations of lead, although the ingestion of the same number of shot did raise the concentration. The shot in the gizzard were eroded, and their lead content had therefore been partly dissolved as lead salts, a readily ab- sorbed form that increases circulating lead levels [8,9,26,33, 341. The findings in these two specimens suggest that if a bird carries a large enough number of shot embedded in its tissues, and survives for long enough, small amounts of lead may be released and may lead to increases in blood and liver concentrations, although the increases may be too small to cause acute intoxication. Another source of lead ingestion is contaminated prey [ 14,27,35-381. In general, our figures suggest that raptors in the region of Murcia were exposed to rather low levels of lead in the environment.

In 80% of all the birds analyzed here, lead concentration in bone tissue was greater than 2 pg/g; mean lead concentration for the entire sample (n = 51) of all feeding groups was 7.56 pg/g (range 0.51 to 54 pg/g). Although different figures have been published for bone lead concentration in non- exposed birds, most experimental studies in wildfowl report values between 1 and 3 pg/g [36,39,40]. These results suggest that birds in the region of Murcia are chronically exposed to lead, which, once accumulated in bone, remains practically stable for half-lives of several years. Bone lead concentrations may thus be useful in monitoring prolonged exposure [24,4 1-43].

Cadmium

Mammals and birds accumulate cadmium from foods in the kidney and liver [44,45]. In our results, omnivores (gulls) had the highest mean concentrations of cadmium in all tissues except bone, in comparison with the other feeding groups (statistically significant difference, Table 4). This finding reflects the feeding habits of these species, which scavenge for food at dumps and garbage heaps. The diet of these birds also includes shellfish and aquatic invertebrates, which have been shown to accumulate large amounts of cadmium [44,46,47]. Our findings are similar to those reported by Hut- ton [30] for silver gulls.

Mean levels of cadmium in liver and kidney of piscivores

and insectivores were significantly higher than in diurnal and nocturnal raptors. Mean brain and blood concentrations of cadmium in piscivores were significantly higher than in other feeding groups (Table 4). Aquatic invertebrates accumulate cadmium from the aquatic milieu, and they can be used as monitors of environmental contamination [44,46]. The wetlands of the region of Murcia contain appreciable amounts of cadmium, and fish-eating birds, which are the next link up in the food chain, thus also serve as monitors of contamination [ 1 I]. These values are lower than many of the figures published in earlier studies [45,48,49]. These differences could be explained by the amount of industrial sources in this area in comparison with other areas.

After omnivores, insectivorous birds had the highest concentrations of cadmium in kidney, and they also had one of the highest concentrations in liver of all species studied here. This finding can be traced to the accumulation of cadmium in the land invertebrates these species feed on [SO].

Diurnal and nocturnal raptors had significantly lower concentrations of cadmium in comparison with insectivores, piscivores, and omnivores (Table 4). The major sources of cadmium emission are associated with heavy industry [5 11, and in the region we studied, most raptors inhabit areas far from centers of human activity. We have found no other data on cadmium levels in birds of prey.

Of the entire sample of birds studied here, 97.3% had a liver cadmium/kidney cadmium ratio below 1, the value considered indicative of prolonged exposure and accumulation [7]. This ratio is informative of exposure, as the kidney is the main site of accumulation of this element, especially as cadmium thioneine. The lower blood concentrations of cadmium and the liver cadmium/kidney cadmium ratio found in the present study suggest that birds were continuously exposed to low levels of cadmium.

Sampling area

Lead and cadmium in tissues and blood of wild birds according to the sampling area are presented in Tables 5 and 6, respectively.

The region where we collected the birds is located in southeastern Spain on the Mediterranean coast and lies on

Table 5 . Concentrations of lead in tissues (pg/g wet wt.) and blood (pg/dl) of wild birds sampled during 1993 from different locations of Murcia region, southeastern Spain

Lead concn.a in tissues (pg/g) and blood (pg/dl)

Locations Liver Kidney Brain Bone Blood

Cartagena 0.25 ? 0.18 (24)

City of Murcia 0.28 k 0.19 (26) 0.05-0.75

0.04-0.70 0.14 f 0.12 (13) 0.02-0.45

Vega Rio Segura

Rest of the region 0.32 k 0.35 (22) 0.04-1.24

0.47 + 0.56 (20)

0.43 f 0.42 (18)

0.20 k 0.19 (13)

0.32 f 0.25 (20)

0.04-2.40

0.07-1.70

0.03-0.77

0.02-0.83

0.15 k 0.24 (24) 0.007-1.23 0.07 t 0.04 (26) 0.02-0.20 0.07 f 0.05 (13) 0.01 -0.15

0.006-0.20 0.08 + 0.06 (22)

12.4 f 17.9 (14) 0.5-54 4.1 t 3.5 (9) 0.64-12 1.6 ? 0.7 (1 1) 0.62-2.9 7.2 f 13.2 (8) 0.5-39

20.28 k 16.6 (8) 5-57

13.5 (4) 5.7-36 5.45 k 1.5 (8) 3-7

15.9 f 11.1 (19) 3-50

aMean f SD (n ) , and range.


Table 6. Concentrations of cadmium in tissues (pg/g wet wt.) and blood (pg/dl) of wild birds sampled during 1993 from different locations of Murcia region, southeastern Spain

Cadmium concn.a in tissues (pg/g wet weight) and blood (pg/dl)

Locations Liver Kidney Brain Bone Blood

Cartagena 0.18 f 0.17 (24)

City of Murcia 0.12 t 0.13 (26) 0.002-0.61

0.002-0.61 Vega Rio Segura 0.076 f 0.051 (12)

0.008 -0.2 Rest of the region 0.097 t 0.131 (22)

0.003 -0.6

0.83 & 1.31 (20) 0.04-4.70 0.22 +- 0.21 (18) 0.006-0.74 0.15 +- 0.10 (12)

0.18 * 0.24 (20) 0.02-0.33

0.007-1.01

0.03 k 0.05 (24)

0.008 k 0.01 (26)

0.02 t 0.016 (12) 0.003-0.05 0.02 t 0.040 (22) 0.001-0.19

0.001-0.25

0.00 1-0.04

0.022 * 0.031 (14) 0.00-0.11 0.016 f 0.021 (9) 0.00-0.06 0.016 t 0.020 (11) 0.00-0.048 0.007 k 0.005 (8) 0.00-0.02

0.13 * 0.08 (8) 0.01-0.28 0.08 (4) 0.00-0.20 0.10 t 0.08 (8) 0.00-0.26 0.14 t 0.07 (19) 0.01-0.28

aMean t SD (n), and range.

one of the African-European flyways (Fig. 1). The climate is typically Mediterranean, with mild temperatures through- out the year.

The highest concentrations of lead and cadmium in tissues and blood were found in Cartagena; differences in comparison with the other three regions were especially significant for cadmium ( p < 0.05). Heavy industrial activity in Car- tagena is represented by electric power plants, explosives fac- tories, and shipbuilding; in addition, the incineration of wastes is unregulated, and the city is an active military and commercial port. Slag and sludge from mines, refineries, and other sources have accumulated near the city.

Accordingly, large amounts of lead, cadmium, and other contaminants are present in this environment, and geograph- ical and climatological factors impede the efficient dispersion

t -N-

Fig. 1. Illustration of some bird migration routes between Africa and Europe [53]. N Region of Murcia.

of these contaminants. We found no significant differences among the other sampling areas (Murcia, Vega del Rio Segura, and the rest of the region) in tissue or blood cadmium concentrations, and we must therefore assume that the degree of contamination by this metal is similar in these areas, which lack heavy industries.

In all sampling areas, kidney and liver concentrations of lead were similar to those found in Cartagena. A possible explanation for this finding is that lead contamination is caused mostly by vehicle exhaust fumes, which account for more than three-fourths of the entire burden of lead emitted into the atmosphere in Europe [51]. In the rest of the region (ini- tially considered to be uncontaminated), the finding that tissue and blood concentrations of lead were similar to those in the city of Murcia may have been due to the region’s ex- tensive system of major roadways bearing intense traffic.

The lowest concentrations of cadmium and lead were found in birds from the Segura River region (a highly contaminated area). This finding may reflect the fact that most contaminants of this river are organic compounds released by nearby food-processing industries [32] ; contamination due to metals is therefore comparatively low.

The lead and cadmium concentrations found in wildfowl did not differ very much from those in humans [52]. This suggests that human activity has a notable effect on the accumulation of these two metals in wild birds, and that it may be possible to draw correlations between the concentrations of these two contaminants in birds and humans. Despite dietary differences between humans and birds, the similarity in tissue levels suggests that the determining sources of contamination could be water and air.

CONCLUSIONS

The findings of the present study suggest that wildfowl in the region of Murcia in southeastern Spain are continuously exposed to low doses of environmental lead and cadmium. Tissue concentrations of lead and cadmium are influenced by feeding habits. Lead shot embedded in the tissues of live birds as a result of gunshot wounds may increase blood and tissue concentrations of lead.

The measurement of low concentrations of cadmium in


blood is possible with the analytical method described (ASV) and could be useful in determining recent exposure

Acknowledgement- We thank P Espinosa for collecting samples, P Maria MOP and 1 Navas for aswance in preparing samples for lead and cadmium analysis, A Tovar and P Rueda for secre- tarial assistance, and Karen Shashok for translating the original manuscript into English

fects of chronic dietary lead in American kestrels (Falco spar- verius) J Wild1 Dis 19 110-113

20 Ohi, G., H. Seki, K. Akiyama and H. Yagyu. 1974 The pigeon, a sensor of lead poisoning Bull Environ Contam Toxicol 12 92-98

21 Gretz, M. and C. B ~ ~ I ~ . 1983 Contamination par le plomb et le cadmium des oiscaux de proie dans l’est de la France Bull Assoc Philomatrque d’Alsacie 20 135-161

22 Redie. P.T . G.E. Duke. S. Schwartz and E. Lawler. 1983 An

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

REFERENCES

Lantzy, R.J. and F.T. Mackenzie. 1979 Atmospheric trace metals Global assessment of man’s impact Geochrm Cosmochrm

Clark, R.B. 1992 Marine Pollution, 3rd ed Clarendon, Oxford, UK Stendell, R.C., R.L. Smith, K.P.BurnhamandR.E. Christku- sen. 1979 Exposure of waterfowl to lead A nationwide survey of residues in wing bones of seven speiies, 1972-1973 U S Fish Wild1 Serv Spec Sci Rep - Wildl 223 1-12 Hutton, M. and G.T. Goodman. 1980 Metal contamination of feral pigeons Columba livia from the London area Part 1 - tissue accumulation of lead, cadmium and zinc Environ Pol-

Di Giulio, R.T. and P.F. Scanlon. 1984 Heavy metals in tissues of waterfowl from the Chesapeake Bay, USA Environ Pollut

Anderson, W.L. and S.P. Havera. 1985 Blood lead, protopor phyrin, and ingested shot for detecting lead poisoning in water

Scheuhammer, A.M. 1987 The chronic toxicity of aluminium, cadmium, mercury, and lead in birds A review Environ Pol

O’Halloran, J., A.A. Myers and P.F. Duggan. 1988 Lead poi soning in swans and sources of contamination in Ireland Zoo1 Lond 216 21 1-223 Honda, K. , D.P Lee and R. Tatsukawa. 1990 Lead poisoning in swans in Japan Envrron Pollut A 65 209-218 Samuel, M.D., E.F. Bowers and J.C. Franson. 1992 Lead ex posure and recovery rates of black ducks banded in Tennessee

Furness, R.W. and J.J D. Greenwood. 1993 Birds as Monitors of Environmental Change Chapman & Hall, London, UK Henny, C.J., L.J. Blus, D.J. Hoffman, R.A. Grove and J.S. Hatfield. 1991 Lead accumulation and osprey production near a mining site on the Coeur d’Alene River, Idaho, Arch Envr ron Contam Toxicol 21 415-424 Oehme, M. and W. Lund. 1979 Comparison of digestion pro cedures for the determination of heavy metals (Cd, Cu, Pb) in blood by anodic stripping voltammetry Fresenrus 2 Anal Chem 298 260-268 Pain, D.J. and C. Anuard-Tnqnet. 1993 Lead poisoning of rap tors in France and elsewhere Ecotoxicol Envrron Saf 25 183- 192 Goede, A.A and P. De Voogt. 1985 Lead and cadmium in wa ters from the Dutch Wadden Sea Environ Pollut A 37 311- 322 Diez, P., A. Lopez, A. Martin, E. Gadea, A. Pascual and A Luna Maldonado. 1992 Niveles de cadmio y plomo en gestantes y neonatos con y sin exposicion ambiental Estudio compara tivo Acta Pediatrica EspaAola 50 316-3 19 Cabeza, J.M., E. Espinosa, F Vdlanueva, L. Vazquez and M.A. Garcia. 1991 Lead and zinc protoporphyrin reference in the blood of a rural child population in Astunas, Spain Sci Total Environ 107 91-98 Yeoman, W.B., F. Colinet and B. Griepink. 1985 The certifi- cation of lead and cadmium in three lyophilized blood materi als CRM 194, 195, 196 Community Bureau of Reference, Commission of the European Communities, Brussels, Belgium Franson, J.C., L. Sileo, O.H. Pattee and J.F. Moore. 1983 Ef-

Act0 43 51 1-525

lut A 22 207-217

A 35 29-48

fowl Wildl SOC Bull 13 26-31

lut 46 263-295

J Wildl D ~ s 28 555-561

investigation into the effects of lead poisoning on bald eagles and other raptors A final report Minnesota Endangered Spe- cies Program Study 200A-200B Minnesota Department of Nat ural Resources, St Paul, MN, pp 1-44

23 O’Halloran, J., P.F. Duggan and A.A. Myers. 1988 Biochem- ical and haematological values for mute swans (Cygnus olor) Effects of acute lead poisoning Avian Patho/ 17 667-678

24 Rabinowitz, M.B., G.W. Wetherill and J.D. Kopple. 1976 Ki- netic analysis of lead metabolism in healthy humans J Clrn In vest 58 260-270

25 Hoffman, D.J., O.H. Pattee, S.N. Wiemeyer andB. Mulhern. 1981 Effects of lead shot ingestion on 6 aminolevuhnic acid de hydratase activity, hemoglobin concentration, and serum chemistry in bald eagles J Wildl Drs 17 423-431

26 Pattee, O.H., S.N. Wiemeyer, B. Mulhern and L. Sileo. 1981 Experimental lead shot poisoning in bald eagles J Wild1 Man age 45 806-810

27 Feierabend, J.S. and 0. Myers. 1984 A national summary of lead poisoning in bald eagles and waterfowl National Wildlife Federation, Washington, DC

28 Gestal, J.J., M.R. Aguiar and M. Romani. 1991 Epidemiolo- gia de la intoxicacion por plomo Mapfre Medicina 2 239-249

29 Clark, T.P., R.J. Norstrom, G.A. Fox and H.T Won. 1987 Dy- namics of organochlorines in herring gulls (Larus argentatus) I1 A two-compartment model and data for ten compounds En- viron Toxicol Chem 6 547-549

30 Hutton, M. 1981 Accumulation of heavy metals and selenium in three seabird species from the United Kingdom Envrron Pol-

31 Grue, C.E., D.J. Hoffman, W.N. BeyerandL.P. Franson. 1986 Lead concentrations and reproductive success in European star lings Sturnus I ulgarrs nesting within highway roadside verges Envrron Pollut A 42 157-182

32 Victoria, F. 1987 ElMedro Ambiente en la Region de Murcia Consecuencias Economicas y Estructurales de la Integracion en las Cornunidades Europeas Consejeria de Hacienda y Adminis tracion Publica, Comunidad Autonoma, Murcia, Spain

33 Pain, D.J. and B.A. Rattner. 1988 Mortality and hematology associated with the ingestion of one number four lead shot in black ducks, Anus rubripes Bull Envrron Coniam Toxicol 40 159-164

34 Havera, S.P., W.L. Anderson and S.G Wood. 1989 Use of blood from dead mallards to monitor lead poisoning Wildl Soc Bull 17 241-244

35 Pattee, O.K. and S.K. Hennes. 1983 Bald eagles and waterfowl The lead shot connection Trans N A m Wild1 Nut Resour Conf 48 230-237

36 Custer, T.W., J.C. Franson and O.H. Pattee. 1984 Tissue lead distribution and hematological effects in American kestrels (Falco sparverrus L ) fed biologically incorporated lead J P”Jld1 DlS 20 39-43

37 Jansen, D L., J.E. Oosterhus, J.L. Allen, M P. Anderson, D.G. Kelts and S.N. Wiemeyer. 1986 Lead poisoning in free-ranging California condors J Am Vet Med Assoc 189 11 15-1 117

38 Garner, M. 1991 Suspected lead toxicosis in a captive goshawk J A m Vet Med Assoc 199 1069-1070

39 Finley, M.T., M.P Dieter and L.N. Locke. 1976 Sublethal ef fects of chronic lead ingestion in mallard ducks J Toxicol En- vrron Health 1 929-937

40 Havera, S.P., S.G. Wood and M.M. Georgi. 1992 Blood and tissue parameters in wild mallards redosed with lead shot Bull Environ Contam Toxicol 49 238-245

lUt A 26 129-145


41. White, D.H. and R.C. Stendell. 1977. Waterfowl exposure to lead and steel shot in selected hunting areas. J. Wildl. Manage. 41~469-475.

42. Honda, K . , B.Y. Min and R. Tatsukawa. 1986. Distribution of heavy metals and their age-related changes in the eastern great white egret, Egretta alba modesta, in Korea. Arch. Environ. Contam. Toxicol. 15:185-197.

43. Merchant, M.E., S.S. Shukla and H.A. Akers. 1991. Lead concentrations in wing bones of the mottled duck. Environ. Tox- icol. Chem. 10:1503-1507.

44. Hunter, B.A. and M.S. Johnson. 1982. Food chain relationships of copper and cadmium in contaminated grassland ecosystems. Oikos 38: 108-1 17.

45. Cain, B.W., L. Sileo, J.C. Fransonand J. Moore. 1983. Effects of dietary cadmium on mallard ducklings. Environ. Res. 32:286- 297.

46. Devineau, J. and C. Amiard-Triquet. 1985. Patterns of bioac- cumulation of an essential trace element (zinc) and a pollutant metal (cadmium) in larvae of the prawn Palaemon serrutus. Mar. Biol. 86: 139-143.

47. Diaz, J., A. Torreblanca and J. Del Ramo. 1993. Presencia de metales en el medio acuatico. In A. Mas and J.M. Azcue, eds., Metales en Sistemas Biologicos. Promociones y Publicaciones Universitarias, Barcelona, Spain, pp. 187-206.

48. White, D.H., K.A. King and R.M. Prouty. 1980. Significance of organochlorine and heavy metal residues in wintering shore- birds at Corpus Christi, Texas, 1976-1977. Pestic. Monit. J .

49. Evans, P.R. and S.J. Moon. 1981. Heavy metals in shore birds and their prey. In P.J. Say and B.A. Whitton, eds., HeavyMet- als in Northern England: Environmental and Biological Aspects. University of Durham, Durham, UK, pp. 181-190.

50. Beyer, W.N., R.L. Chaney and B.M. Mulhern. 1982. Heavy metal concentrations in earthworms from soil amended with sewage sludge. J. Environ. Qual. 11:381-385.

14:58-63.

5 1. Pacyna, J.M., J. Munch and F. Axenfeld. 1991. European inven- tory of trace metal emissions to the atmosphere. In J.P. Vernet, ed., Heavy Metals in the Environment. Elsevier, Amsterdam, The Netherlands, pp. 1-20.

52. Fergusson, J.E. 1990. The Heavy Elements: Chemistry, Envi- ronmental Impact and Health Effects. Pergamon, Oxford, UK.

53. Berthold, P. 1993. Bird Migration: A General Survey. Oxford University Press, Oxford, UK.

APPENDIX Instrument conditions for the analysis of lead and cadmium by

anodic stripping voltammetry

Working electrode Reference electrode Auxiliary electrode Nitrogen purge Method Electrolysis timea Measuring mode Modulation amplitude Pulse repetition time Initial voltage Stopping time Final voltage Scan rate Supporting electrolyte

Multimode working electrode Ag/AgCl, KCI 3 mol/L Platinum 5 min Hanging mercury drop

Differential pulse normal 50 mV 200 ms -800 mV 30 s -200 mV 10 mV/s

60-300 s

HCl, 100 pl

‘Electrolysis time depends on the lead and cadmium concentration in each sample in the preliminary analysis (e.g., 7 ng Cd, 10 ng Pb, t = 300 S; 4 pg Pb, t = 60 s).

Lead and cadmium in wild birds in southeastern Spain

Documents

Transcript of Lead and cadmium in wild birds in southeastern Spain