Biomonitoring environmental contaminants near a municipal solid-waste combustor

PII:

S0269-7491(97)00012-2

Environmental Pollution, Vol. 96, No. 1, pp. 99-105, 1997 © 1997 Elsevier Science Ltd All rights reserved. Printed in Great Britain 0269-7491/97 $17.00 + 0.00

ELSEVIER

BIOMONITORING ENVIRONMENTAL CONTAMINANTS NEAR A MUNICIPAL SOLID-WASTE COMBUSTOR D. G. Rumboldfl* M. C. Brunerfl M. B. M i h a l i k at a n d E. A. M a r t i b aSolid Waste Authority Palm Beach, 7501 North Jog Road, West Palm Beach, FL 33412, USA bTriangle Laboratories Inc. of RTI, Research Triangle Park, NC, USA

(Received 1 June 1996; accepted 13 December 1996)

single largest contributor of Hg to the atmosphere (KBN, 1992). Other metals or metalloids detected in stack emissions or collected ashes include lead (Pb), cadmium (Cd), copper (Cu), nickel (Ni), beryllium (Be), tin (Sn), zinc (Zn), arsenic (As) and selenium (Se) (Nriagu and Pacyna, 1988; Korzun and Heck, 1990; Mumma et al., 1990; Roffman and Roffman, 1991). Environmental gradients in a variety of media, with increasing concentrations near MSW combustors, have been reported for both dioxins and metals (Bache et al., 1991; Liem et al., 1991). Because MSW combustion has long been regarded as a major source of environmental pollution, particularly by the lay public, obtaining regulatory approval for construction of new combustors is difficult. Considerable controversy occurred in December 1985 over an application to construct and operate an MSW combustor in Palm Beach County, Florida. In addition to the human-health issues, concerns also focused on potential impacts this facility might have on a large wading-bird colony and endangered snail kite (Rostrhamus sociabilis) roost located nearby (for details, see Rumbold and Mihalik, 1994). Accordingly, as part of a larger impact assessment, a long-term biomonitoring program was begun in 1989. This program consisted of surveys of local wildlife for residues of chemicals potentially released from this facility. Specifically, eggs and nestlings of anhingas (Pelecaniformes: Anhinga anhinga) and white ibises (Ciconiiformes: Eudocimus albas) were collected and analyzed for residues of tetrachlorodibenzop-dioxin (TCDD), tetrachlorodibenzofuran (TCDF) and selected metals. Anhingas were selected as a sentinel species because they forage in the extensive wetlands near the facility and feed on fish that concentrate contaminants. Thus, tissue concentrations in the anhingas were expected to serve as an indicator of environmental contaminants, particularly those that exhibit biomagnification. Although ibises typically feed on crayfish (Kushlan and Kushlan, 1975), members of this population supplement their diet with refuse from nearby landfills (Rumbold, 1990; Rumbold et al., 1996). Consequently, incidental ingestion of ash by the ibises was identified as a potential risk for those scavenging at the ash-refuse landfill. Concern for the ibises was heightened when they were observed bathing in and drinking from

Abstract Tetrachlorodibenzo-p-dioxin ( TCDD ) , tetrachlorodibenzofuran (TCDF) and selected metal concentrations were measured in eggs and nestlings of anhingas (Anhinga anhinga) and white ibises (Eudocimus albus) collected from a colony next to a municipal solid-waste ( M S W ) combustor and ash landfill. Most of the measured residues, including TCDD, TCDF, arsenic, beryllium, cadmium and nickel, remained at pre-operational levels during the first five years of facility operation. Selenium (in anhingas) and mercury (in both anhingas and ibises) occurred at their lowest concentrations in samples collected during the fifth year of facility operation (Year-5). Alternatively, concentrations of lead in ibis nestlings were highest in Year-I and Year-5 compared to Year-O. The M S W combustor could neither be ruled out nor confirmed as the source of this lead. © 1997 Elsevier Science Ltd

Keywords: Incinerator, dioxins, metals, anhinga, white ibis. INTRODUCTION

Dioxins, polycyclic aromatic hydrocarbons (PAH) and heavy metals have been detected in stack emissions and in collected ash from municipal solid-waste (MSW) combustors (Korzun and Heck, 1990; Mumma et al., 1990; Shane et al., 1990; USEPA, 1987; Roffman and Roffman, 1991). Much of the concern about organic contaminants from MSW combustors has focused on 2,3,7,8 tetrachlorodibenzo-p-dioxin (USEPA, 1987; Travis and Hattemer-Frey, 1991). While dioxins are produced by many other sources (Travis et al., 1989), MSW combustors are thought to be a major source to the environment (Fiedler and Hutzinger, 1992; Harrad and Jones, 1992). Of the heavy metals emitted from MSW combustors, mercury (Hg) has received the most attention (Collins and Cole, 1990; Keneagy, 1992). In Florida, MSW combustion has been estimated to be the Present address: 9686 SW 2nd Street, Boca Raton, FI 33428, USA. * To whom correspondence should be addressed. 99

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D.G. RumboM et al.

temporary pools of rainwater on top of ash-refuse disposal sites. Therefore, while levels of contaminants in both species serve to biomonitor releases from the MSW combustor, residue profiles of the ibises may also reflect exposure at the landfill. This document reports concentrations of dioxins, furans and metals in eggs and whole bodies of nestlings of anhingas and white ibises collected during four surveys at the MSW combustor. The first survey was carfled out before facility start-up. Three additional surveys were conducted over a period of five years after the facility became operational.

METHODS Study site The MSW combustor is a component of the North County Resource Recovery Facility (NCRRF) that is located on 1320 acres in West Palm Beach, Florida (Lat. 26° 46'N; Long. 80° 08'W). The N C R R F processes about 2000 tons of MSW per day; refuse-derived fuel is burned continuously. The combustor began operating in November 1989, has a 76 meter tall stack with two operational flues and uses both dry flue-gas scrubbers and electrostatic precipitators for pollution control. Two types of ash, bottom ash (90% of solid output) and fly ash (10% of solid output) are produced by the combustor. Combined ash is transported and deposited in a double-lined landfill located on-site along with refuse rejected from the combustor (about 22% of the MSW is considered too small and is rejected). In addition to the MSW combustor and the ash-refuse landfill, the N C R R F included a yardwaste/construction-debris landfill, a sludge composting facility, a vehicle maintenance shop, a recycling center, a household hazardous waste transfer facility, an administration complex, and two deep injection wells. Landfill leachate and process water from the MSW combustor are deepwell injected. The entire site is hydrologically isolated with on-site stormwater being routed through a series of basins and finally discharged off-site to a single canal. Regional features in the area include: (1) the large wading bird rookery and endangered snail kite roost located within 0.8 km of the facility (for details, see Rumbold and Mihalik, 1994); (2) the City of West Palm Beach Water Catchment Area, a 44 km 2 remnant of the Loxahatchee Slough. This area, located directly west of the NCRRF, consists of a sawgrass - - spikerush marsh managed as a potable water reservoir with inputs from Lake Okeechobee; (3) the Dyer Boulevard Sanitary Landfill that operated from 1968 to 1989 and is located 2.5 km east of the NCRRF.

Sampling methods Each year, 10 eggs and 10 nestlings were collected from both anhinga and white ibis nests. A single egg or nestling (at 10-14 days of age when chicks begin to climb out of the nest) was collected from randomly selected nests containing more than one egg or young. Live

nestlings were sacrificed immediately upon capture by cervical dislocation. Contents of eggs and carcasses of whole nestlings (minus bill, legs, gastrointestinal tract and feathers) were placed in commercially obtained chemically-cleaned jars with Teflon coated caps (I-Chem Research; Hayward, CA), and were frozen pending chemical analysis. Each composite sample consisted of the contents of two eggs or the carcasses of two nestlings. In 1989, an additional sample consisting of mixed organs and muscle tissue from two adult white ibises found dead at the ash-refuse landfill, was also analyzed. Samples were collected during the birds' nesting season (April-June) in 1989 prior to the start-up of the MSW combustor (_= Year-0), in 1990 ( - Year-l), in 1991 (= Year-2), and again in 1994 ( - Year-5). From 1989 through 1994, a total of 81 samples were analyzed, representing 162 individuals (81 eggs, 79 nestlings, and a mixed sample of two salvaged adult ibises). In 1990, three anhinga eggs were inadvertently placed into one composite sample; another egg was subsequently collected from the field. Also in 1990, only nine ibis nestlings of appropriate age were located.

Analytical methods Samples for dioxin and furan analyses were homogenized using a food processor and then fortified with carbon-labeled internal standards. Soxhlet extraction was performed with methylene chloride followed by hexane exchange. The extract was washed with sulfuric acid and sodium hydroxide and then chlorine-labeled surrogate standards were added. This was followed by pre-cleaning on an alumina column and final cleanup on a carbon column. The residue was dissolved in a nonane solution and processed using High-Resolution Gas Chromatography/ High-Resolution Mass Spectrometry (HRGS/HRMS). Samples were run on two different GC columns, the DB5 and the DB225. The higher value was used when concentrations differed between columns. Lower limits of detection varied from 0.03 to 1.4ngkg -I wet wt depending on sample volume, calibration, and GC column. Analyte concentrations were corrected using recovery rates of internal standards. As, Se and select metal analyses were carried out by a contract laboratory, Research Triangle Institute (Research Triangle Park, North Carolina). Subsamples of homogenized tissues were lyophilized then digested, refluxed, or solubilized in nitric acid concurrent with specific microwave techniques. Inductively Coupled Plasma (Argon) Emission Spectrometry (ICP) was used for the detection and quantification of Be, Cd, Pb and Ni. Graphite Furnace Atomic Absorption (GFAA) spectrophotometry was employed for As and Se. Hg was determined using Cold Vapor Atomic Absorption spectrophotometry. In 1991, Pb residues greater than 5 #gg-I were confirmed by GFAA. The lower limit of detection varied slightly during the study period; on a /~g g-~ dry wt basis it ranged between 0.02-0.05 for Be, 0.2-0.25 for Cd, 1.0-1.2 for Pb, 1.0-1.2 for Ni, 0.30-0.4 for As, 0.02-0.2 for Hg and 0.3-0.4 for Se.

Biomonitoring environmental contaminants Quality ammmee Five sodium sulfate blanks were analyzed as method blanks for the T C D D f r C D F analyses (one each year, two in 1994). All but one method blank were negative for TCDD/TCDF; one of the two blanks run in 1994 was contaminated and contained 0.24ppt 2,3,7,8 TCDF, 0.08 ppt total TCDD, and 0.34ppt total TCDF. Two of six store-bought egg blanks were positive for T C D D f r C D F ; in 1989, a store-bought egg blank contained 1.2ppt 2,3,7,8-TCDF and, in 1994, a storebought egg blank contained 0.15 ppt 2,3,7,8-TCDF, <_ 0.06 ppt total TCDD and 0.15 ppt total TCDF. All four store-bought chicken tissue blanks (one each year) were negative for TCDD/TCDF. Recovery rates of the carbon-labeled internal standard TCDD in field samples was 70.1 ± 30.3% (n= 63) on the DB-225 column and 61.0±20.5% (n=46) on the DB-5 column. Recovery rates of the carbonlabeled internal standard TCDF in field samples was 65.44-25.7% (n=63) on the DB-225 and 64.3±20.0% (n = 46) on the DB-5. Recovery rates of the chlorinelabeled TCDD surrogate was 62.04- 27.3% (n=64) on the DB-225 column and 57.44-21.2% (n=46) on the DB-5 column. Percent recoveries in four laboratory matrix spikes (store-bought eggs in 1990 and 1991, store-bought egg and chicken in 1994) was 110.6± 9.7% for 2,3,7,8-TCDD and 101.0± 16% for 2,3,7,8TCDF. Five sodium sulfate method blanks for metal determination (one each year, two in 1994) were all negative for As, Be, Cd, Hg, Ni, Pb, and Se. Four store-bought egg blanks (not spiked with metals) contained on average: no detected (ND) As, 0.05/~g g-~ Be, ND Cd, ND Hg, ND Ni, ND Pb, and 1.01/zgg -l Se. A store-bought chicken analyzed in 1994 contained: ND As, ND Be, ND Cd, ND Hg, 1.29/~gg-I Ni, 1.9/zgg -I Pb, and 0.66/zg g-t Se. The average coefficient of variation between duplicate analyses of field samples for metals was 6.94- 15.8% (n = 70). Laboratory matrix spikes of all metals had an average recovery of 100.7 ± 8.3% (70). Percent recoveries for a single blind matrix spike analyzed in 1989 was 213.5% for Pb and 136.5% for Se. Statistical methods To facilitate comparison with data reported in the published literature, concentrations of dioxins and furans were based on wet wt, whereas As, Se and metals were based on dry wt. Because of composite sampling, weights were not adjusted to a fresh egg basis. Descriptive statistics were calculated for analytes that were detected in more that 50% of the samples for a given year; data are expressed as the mean ± 1 standard deviation (S.D.). For statistical purposes half of the limit of detection was used where the analyte was below detection limits. The assumptions of normality and equal variances were tested by the Kolmorogov-Smirnov and Levene Median tests, respectively. Data with a normal distribution and equal variance were evaluated by analysis of variance (ANOVA). Data-sets lacking

101

homogeneity of variances, or that departed from the normal distribution, were natural-log transformed and re-analyzed. If transformed data met the assumptions, they were used in ANOVA. If not, raw data were evaluated using the nonparametric Mann-Whitney Rank Sum test or the Kruskal-Wallis 1-Way ANOVA on ranks. If multigroup null hypotheses concerning residue levels were rejected, all groups were compared to Year-0 (1989), employed as a control, using either Dunnett's method (when parametric) or Dunn's method (when non-parametric). All statistical analyses were performed using the statistical software program Sigmastat ~ (Jandel Corporation, San Rafael, California).

RESULTS

Temporal trends Residues of dioxins and furans were found in eggs and nestlings collected in Year-0 through Year-5 (Table 1). A significant among-year difference in egg tissue concentration of 2,3,7,8-TCDD occurred in both the anhingas (Kruskal-Walhs test, H = 9.6, d.f. = 3, p = 0.022) and the ibises (H=8.37; d.f.=3; p=0.04). However, among-year differences were not significant when comparisons were made to pre-operational levels of 2,3,7,8TCDD (i.e. samples collected in Year-0; Dunn's method, p > 0.05). While detected more frequently in nestlings collected in later years, both TCDD and TCDF tissue concentrations actually declined (Table 1). Among-year differences in total-TCDF concentration in anhinga eggs were not significant (H=2.2; d.f.=3; p=0.53). Metals also were found in eggs and nestlings collected in Year-0 through Year-5 (Table 2). Tissue concentrations of As, Be and Cd showed little variation in both eggs and nestlings during the monitoring period (Table 2); As was not detected, and Be and Cd residues were rarely detected. Se concentrations in anhinga eggs varied among years (F= 4.27; d.f. = 3, 16; p = 0.02), with Year-5 concentrations significantly lower than preoperational levels (Dunnett's method, p < 0.05). Other year-to-year comparisons of Se concentrations in anhinga eggs were not significant (Dunnett's method, p >0.05). Se concentrations in ibis eggs did not differ among-years (F=2.6; d.f.-3,16; p=0.09). Se levels in anhinga and ibis nestlings had no among-year differences (F=2.18; d.f.=3,16; p=0.13, and F=l.09; d.f. = 3,16; p = 0.38, respectively). Concentrations of Hg in anhinga eggs varied among-years (F= 3.33; d.f. = 3,16; p = 0.046). Like Se, Hg levels in anhinga eggs collected in Year-5 were lower than pre-operational levels (Dunnett's method, p < 0.05). Other year-to-year comparisons of I-Ig concentration in anhinga eggs were not significant (p > 0.05). There was no among-year variation in Hg concentration in anhinga nestlings (F= 1.98; d.f. = 3,16; p=0.16). Concentration of Hg also declined to below the level of detection in both the eggs and nestlings of the ibises during the monitoring period (Table 2).

D.G. Rumbold et al.

102

Table 1. Mean :t: 1 SD, highest concentration (in parentheses), and frequency of detection (n = 5) of tetra-chiorodibenzo-p-dioxin (TCDD) and tetrachiorodibenzofuran (TCDF) residues in anhinga and white ibis eggs and nestlings collected at the NCRRF during the first five years of operation. Samples collected in Year-0 (1989) prior to facility startup are employed as a control

Analyte

Year of operation

(ng kg-1 wet wt) anhinga

white Ibis

eggs Total TCDD

2,3,7,8-TCDD

Total TCDF

2,3,7,8-TCDF

nestlings

eggs

nestlings

0 1 2 5

1.6 ± 0.9 3.6±3.4 1.4± 1.0 0.3+0.1

(2.6) (9.5) (2.3) (0.4)

4 5 4 4

NC NC NC 0.1±0.1

(1.3) (0.5) (0.2) (0.3)

1 1 I 5

0.4 ± 0.4 2.6±2.7 0.2±0.1 0.6±0.6

(1.0) (7.2) (0.4) (2.3)

3 4 4 5

ND NC 0.I ±0.0 0.2±0.1

0 1 2 5

1.6±0.9 3.6+3.4 1.3 ±0.9 0.3±0.1

(2.6) (9.5) (2.1) (0.4)

4 5 4 4

NC NC NC NC

(1.3) (0.5) (0.2) (0.2)

1 1 1 1

0.4±0.4 2.6±2.7 0.2±0.1 0.3+0.1

(1.0) (7.2) (0.4) (0.4)

3 4 4 5

0 1 2 5

0.2±0.1 0.3+0.2 0.3±0.3 0.2+0.1

(0.4) (0.5) (0.8) (0.3)

4 5 3 3

NC NC 0.2±0.1 0.3+0.1

(4.6) (0.2) (0.3) (0.3)

2 1 4 5

0.1 ±0.1 0.2±0.0 ND 0.1 ±0.1

(0.3) (0.4)

0 1 2 5

0.2±0.2 0.2±0.1 0.2±0.1 NC

(0.4) (0.5) (0.3) (0.2)

4 5 3 2

NC NC 0.2±0.1 0.2+0.0

(0.4) (0.2) (0.3) (0.2)

2 1 4 5

0.1±0.0 0.1 ±0.1 ND 0.1 ±0.1

(0.1) (0.4)

(0.2)

(0.2)

(0.5) (0.2) (0.3)

0 1 4 5

ND ND 0.1 ±0.0 0.1 +0.0

(0.2) (0.1)

0 0 4 4

3 4 0 3

ND ND NC 0.2±0.1

(0.8) (0.2) (0.4)

0 1 1 4

3 3 0 3

ND ND NC 0.1 ±0.1

(0.2) (0.2)

0 0 1 4

NC = not calculated; arithmetic mean given when > 50% of samples contain residues. ND = not detected. A sample of mixed organs and tissues from two dead adult ibises salvaged in 1989 contained: < 0.4 ng kg-1 Total TCDD, < 0.14 ng kg-~ 2,3,7,8-TCDD, < 0.03 ng kg-~ Total TCDF, and ND 2,3,7,8-TCDF.

Ni and Pb were somewhat unusual in that residues of both occurred sporadically at relatively high levels. Tissue concentration of Pb in ibis nestlings was significantly greater in Year-1 and Year-5 when compared to Year-0 ( t = - 3 . 7 2 ; d.f.=8; p=0.006, and t = - 5 . 6 9 ; d.f.=8; p<0.001, respectively). Pb did not increase monotonically over the monitoring period, however, as evidenced by the drop in frequency of detection in Year-2 (Table 2). Differences between eggs and nestlings Higher residues and more frequent detections of T C D D and T C D F occurred in eggs than in nestlings for both species of birds (Table 1). Likewise, Se was more concentrated in eggs than in nestlings for both the anhingas and the ibises (t-test, t =-7.1; d.f. = 38; p < 0.001, t =-8.7; d.f. = 38; p < 0.001 respectively). In contrast, Hg concentrations in anhinga eggs and nestlings did not differ significantly (F = 2.6; d.f. = 1, 32; p = 0.12). Likewise, Hg concentrations did not differ between eggs and nestlings of the ibises, when Year-0 and Year-1 were combined (Mann-Whitney test t = 137; n = 10; p>0.1). There was also no apparent concentration differences between eggs and nestlings for residues of As, Be or Cd for either species. The only contaminants that were generally more concentrated in nestlings compared to eggs were Pb and Ni in the ibises (Table 2). A composite sample of tissues from two dead adult ibises, salvaged in 1989, had residue profiles similar to that observed in nestlings (Tables 1 and 2). Species differences The median egg concentration of 2,3,7,8-TCDD was greater in the anhingas than in the ibises ( M a n n -

Whitney Test, t = 483; p = 0.05). Similarly, egg concentrations of 2,3,7,8-TCDF also were generally greater in the anhingas than in the ibises (Table 1). There was little difference between the two species in either T C D D or T C D F concentrations in nestlings. With the exception of As that was not detected in either species, residues of other metals occurred in some samples of both species (Table 2). Se residues were at greater concentrations in the anhingas than the ibises in both eggs (F = 106.4; d.f. = 1, 32; p < 0.001) and nestlings (F=27.1; d . f . = l , 32; p<0.001). Hg residues were detected more frequently and levels were higher in the anhingas than in the white ibises. By contrast, Pb occurred more frequently and at greater concentration in the ibises.

DISCUSSION Because of a requirement for spatial replication of independent subjects and the need for randomized assignment of treatment groups, it is difficult to investigate the 'average' effects resulting from an industrial operation (Hurlbert, 1984; Stewart-Oaten et al., 1986, Schmitt and Osenberg, 1996). Statistically demonstrating causality can be difficult even where the focus of a study is on the specific putative impact that a particular project may have at a specific locale (for review, see Schmitt and Osenberg, 1996). The objective of present study was to biomonitor environmental contaminants near an MSW combustor. However, because we did not sample birds from distant colonies, the study was 'suboptimal' in that it lacked spatial controls. Without spatial controls there is always a risk that an observed

Biomonitoring environmental contaminants

103

Table 2. M e n ± 1 SD, ~ co~mtrafioR (in parmtheses), and frequency of detection (n = 5) of arsenic, ~ and metal residues in anhinga and white ibis eggs and nestlings collected during the first five years of facility operation. Samples collected in Year-O (1989) prior to facility startup are employed as a control

Analyte

Year of operation

(/zg g-1 dry wt) anhinga

white Ibis

eggs Arsenic

nestlings

eggs

nestlings

0

ND

0

ND

0

ND

0

ND

0

1

ND

0

ND

0

ND

0

ND

0

2 5

ND ND

0 0

ND ND

0 0

ND ND

0 0

ND ND

0 0

Selenium

0 1 2 5

3.4+0.4 3.65:0.6 3.3q-0.6 2.44-0.5

(4.0) (4.2) (4.3) (2.9)

5 5 5 5

2.1+0.8 1.8+0.6 1.74-0.7 1.14-0.2

5 5 5 5

2.1+0.3 1.7+0.2 1.7±0.3 1.74-0.3

5 5 5 5

1.1 +0.2 1.1+0.2 1.04-0.3 0.84-0.2

(1.3) (1.5) (1.4) (1.2)

5 5 5 5

Belyllium

0

NC

(0.3)

2

ND

0

ND

0

NC

(0.1)

2

1

ND

0

ND

0

ND

0

NC

(0.5)

1

2 5

ND ND

0 0

ND ND

0 0

NC ND

2 0

NC ND

(0.1)

1 0

0

ND

0

ND

0

ND

0

ND

1

ND

0

ND

0

ND

0

NC

2 5

ND ND

0 0

NC ND

(0.3)

l 0

ND ND

0 0

ND ND

(3.9)

Cadmium

Nickel

(3.2) (2.7) (2.8) (1.5)

(2.4) (1.9) (2.0) (2.2)

(0.3)

0 (0.5)

l

0 0

0

NC

(1.5)

2

2.0 4- 1.4

4

ND

0

2.1 4- 0.5

(2.7)

1

NC

(10.3)

1

ND

0

ND

0

1.3+1.2

(3.3)

3

2 5

ND ND

0 0

ND ND

0 0

NC 2.7 4- 3.0

(1.6) (7.4)

1 3

ND 2.0 4-0.9

(3.4)

0 5

Mercury

0 1 2 5

1.34-0.7 1.14-0.7 1.34-0.5 0.34-0.3

(2.4) (2.0) (1.9) (0.7)

5 5 5 3

0.8+0.4 0.5+0.4 1.04-0.2 0.84-0.4

(1.3) (1.0) (1.3) (i.3)

5 5 5 5

0.24-0.1 0.44-0.2 NC ND

(0.4) (0.6) (0.4)

5 4 1 0

0.14-0.0 0.14-0.0 ND ND

(0.1) (0.2)

5 5 0 0

Lead

0 1 2 5

NC ND NC ND

(1.9)

1 0 1 0

NC ND NC NC

(3.4)

2 0 1 2

NC (2.9) ND 1.4± 10.7 (2.2) ND

1 0 3 0

1.24-0.7 5.34-3.5 NC 4.94-0.7

(2.2) (10.9) (9.8) (5.7)

3 5 2 5

(2.4)

(1.7) (1.4)

5

ND = not detected. NC = not calculated; arithmetic mean given when > 50% of samples contain residues, A sample of mixed organs and tissues from two dead adult ibises salvaged in 1989 contained: ND As, 1.8/zgg-1 Se, ND Be, 0.6 #gg-i Cd, ND Ni, 0.7 /zgg-1 Hg, and 2.91/zgg-q Pb.

change may be unrelated to the impact (Green, 1979). Accordingly, hypothesis testing in this 'Before-After Impact-only' field assessment cannot conclusively demonstrate causality. Despite the statistical limitations, summary statements of considerable importance can be made regarding temporal trends in residue concentrations. First, there were no monotonic increases in levels of dioxin, furan, or metals in the present study. While concentrations of certain analytes fluctuated, concentrations of As, Be, Cd and Ni remained relatively constant. Moreover, Hg and Se declined by the last year of the study. This data would seem to indicate that environmental concentrations o f these contaminants did not increase locally as a result of MSW operation. Alternatively, concentrations of Pb in ibis nestlings were highest in Year-1 and Year-5, and this warrants some concern. Although there are no simple remedies for lacking internal spatial controls, one recourse is to try to draw inferences, albeit tentative, from comparative data in the published literature. Tissue concentrations of dioxin

and furan observed in the present study were generally much lower than concentrations reported for bird eggs or nestlings from colonies in contaminated areas (Stalling et al., 1985; Elliott et al., 1988). More importantly, concentrations observed in the present study also were generally lower than background levels reported for eggs collected from control or unimpacted colonies (Stalling et al., 1985; Elliott et al., 1988). Generally, concentrations of metal residues in the birds also were lower than levels reported in the literature. Hg and Se in the eggs and nestlings were comparable to levels reported for similar species collected elsewhere (King et al., 1980; Fleming et al., 1984; Henny and Herron, 1989). By contrast, Pb in ibis nestlings were generally greater than what has been reported for other wading birds from Florida (Spalding and Forrester, 1991). The inferences about low Hg and high Pb concentrations in the ibis nestlings are in general agreement with data from other studies that were carried out at this colony which analyzed liver tissues (Spalding and Forrester, 1991; Sundlof et al., 1994).

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D . G . Rumbold et al.

Further inferences can be drawn from tissue-specific differences (i.e. between eggs and nestlings) and speciesspecific differences in residue profiles. Bird eggs are usually considered an indicator of the female's body burden at the time the egg was laid. Accordingly, egg tissue concentrations provide little information on the location where the female was exposed. Alternatively, residues detected in the nestling not only reflect levels in the egg and thus the female, but also reflect levels of contaminants in locally obtained food resources fed to the nestlings. In the present study, contaminants such as TCDD, TCDF, Se and Hg that were less concentrated in the nestlings than the eggs were either being eliminated by the nestlings or were at low enough concentration in the diet of the nestlings to be overcome by the dilution factor associated with chick growth. Alternatively, contaminants such as Pb and Ni that were at greater concentration in the nestling than the eggs were probably relatively concentrated in locally-collected food items fed to the nestlings. Caution must be exercised in making these types of generalizations, however, because not all contaminants are mobilized and transferred to eggs during oogenesis. For example, because Pb is compartmentalized in hard tissues, eggs may not be a reliable indicator of the female's body load of Pb at the time the egg was laid (Leonzio and Massi, 1989). At this point an important question arises. How well do residue levels in eggs and nestlings correspond to tissue concentrations in the adult? Although we are limited in our ability to address this question, the sample of mixed organs and tissues from the two dead adult ibises salvaged in 1989 had profiles similar to those found in the nestlings. Additionally, results from analyses of liver and kidney tissues taken from these two dead adult ibises, analyzed by an outside laboratory (for details, see Spalding and Forrester, 1991), also tend to agree with inferences about concentrations in whole bodies of nestlings. It should be noted that Spalding and Forrester, (1991) concluded that Pb concentrations were at toxic levels in the kidneys. Collectively, the data suggest that Pb is a local problem to both nestling and adult birds. While none of the measured residues occurred only in the ibises Pb was detected more frequently and was at greater concentration in the ibises than the anhingas. There are numerous sources of Pb to the environment (for review, see Eisler, 1988). For example, the study site was located next to a heavily traveled highway (i.e. the Florida Turnpike) and Pb in automobile exhausts may have accumulated in the area prior to its ban as a fuel additive. Nevertheless, because these ibises foraged at the landfill, the simplest interpretation would be that the ash-refuse landfill was the source of this Pb. This may not necessarily have been the case, however. First, samples collected prior to the start-up of the MSW combustor, of both ibis and anhinga, contained Pb residues. This indicates that there was Pb contamination in the area prior to ash landfilling. Yet, one could still argue that the ibises might have been exposed to Pb while scavenging at the old Dyer landfill from some operation

other than ash landfilling, such as refuse landfilling, landfilling sludge from waste water treatment facilities or landfilling fuel contaminated soils. This would be consistent with a report by Leonzio et al., (1986) that black-headed gulls feeding at a 'dump' (i.e. non-ash disposal) had greater tissue concentrations of Pb than gulls feeding in coastal areas of Italy. However, such a simple explanation would not account for the Pb residues occurring in the anhingas. Because anhingas fed on fish from area wetlands, contaminants that occurred as residues in their tissues were probably distributed in the local environment and present in the aquatic food chain. Hence, there was probably a source of Pb, other than the landfills, present in the area prior to the operation of the MSW combustor. Nevertheless, the MSW combustor cannot be ruled out as a possible source of Pb following its operation, and exposure at the ash-landfill is the most obvious explanation for the increases in Pb residues observed in the ibises in Year-I and Year-5. Direct exposure at the ash-landfill seems more likely at this point than widespread contamination from atmospheric deposition of stack emissions because Pb profiles in the anhingas remained unchanged. However, it must be emphasized that contamination from the MSW combustor is speculative and that the source of Pb remains uncertain. An argument for the preceding scenario would be strengthened, notwithstanding the statistical limitations of this study, if, in the future, similar increases were observed in other contaminants associated with MSW combustion.

ACKNOWLEDGEMENTS The authors would like to thank Karen Larson and Chris Perretta for their assistance in sampling. We are also grateful to Ben Martin for his comments during the planning stage and for the blind matrix spike. We would also like to thank William Gutnecht for coordinating metal analysis at Research Triangle Institute.

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