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Science of the Total Environment 388 (2007) 316 – 324
www.elsevier.com/locate/scitotenv
Mercury transport and bioaccumulation in riverbank communities of
the Alvarado Lagoon System, Veracruz State, Mexico
Jane L. Guentzel a,⁎, Enrique Portilla b , Katherine M. Keith c , Edward O. Keith c
a
Coastal Carolina University Department of Marine Science P.O. Box 261954 Conway, SC, 29528-6054, USA
b
Instituto de Investigaciones Biologicas Universidad Veracruzana Xalapa, Ver., Mexico
c
Oceanographic Center Nova Southeastern University 8000 N. Ocean Drive Dania Beach, FL, 33004, USA
Received 16 April 2007; received in revised form 16 July 2007; accepted 24 July 2007
Available online 12 September 2007
Abstract
The Alvarado Lagoon System (ALS) is located within the Papaloapan River Basin in southern Veracruz, Mexico. The ALS is a shallow
system (2 m) connected to the Gulf of Mexico through a narrow sea channel. There are a large number of riverbank communities within the
ALS that are dependent upon its biological productivity for comestible and economic subsistence. The purpose of this project was to
determine the levels of mercury in water, sediment, fish, and hair samples from within the Papaloapan River Basin and to characterize the
risk of Hg exposure to the individuals that reside in these communities. Water and fish samples were collected during the wet (September
2005) and dry (March 2003 and 2005) seasons. Hair samples, dietary surveys, and sediment samples were obtained during the wet and dry
seasons of 2005. Total Hg in the water column ranged from 1.0 to 12.7 ng/L. A strong correlation (R2 =0.82; p b 0.001) between total Hg and
total suspended solids in the water column suggests that particulate matter is a transport mechanism for Hg within the lagoon system. Total
Hg in the sediments ranged from 27.5 to 90.5 ng Hg/g dry weight with no significant difference between the 2005 wet and dry seasons.
There was a mild, but significant, correlation between total Hg and % carbon for the March 2005 sediment samples (R2 = 0.435; p = 0.020),
suggesting that Hg is associated with organic matter on the solid phase. Concentrations of total Hg in fish and shellfish harvested from the
ALS ranged from 0.01 to 0.35 μg Hg/g wet. The levels of total Hg in hair ranged from 0.10 to 3.36 μg Hg/g (n = 47) and 58% of the samples
were above 1.00 μg Hg/g. The findings from this study suggest that individuals who frequently consume fish and shell fish containing low
levels of Hg (b 0.3 μg/g) can accumulate low to moderate body burdens of Hg, as indicated by hair Hg concentrationsN 1.0 μg/g, and may be
at risk for experiencing low dose mercury toxicity.
© 2007 Elsevier B.V. All rights reserved.
Keywords: Mercury; Sediment; Fish; Hair; Alvarado Lagoon System; Veracruz; Mexico
1. Introduction
Mercury exists in many different physical and chemical
forms within the environment and it is the interconversions
between these species that mediate its distribution patterns
and geochemical cycling. The three most prevalent forms
⁎ Corresponding author. Tel.: +1 843 349 2374; fax: +1 843 349 2545.
E-mail addresses: [email protected] (J.L. Guentzel),
[email protected] (E. Portilla), [email protected] (E.O. Keith).
0048-9697/$ - see front matter © 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.scitotenv.2007.07.060
of mercury in the environment are elemental mercury
(Hg0), divalent inorganic mercury (Hg (II)), and organic or
monomethylmercury (CH3Hg+) which bioaccumulates in
higher trophic levels and is most toxic to organisms near
the top of the food chain. Sources of mercury to the
environment are natural and anthropogenic. The natural
sources include volcanic emissions, windblown dust from
continental areas, and the emission of gaseous Hg from
soils, vegetation, and the ocean. Fossil fuel combustion,
mining/smelting, and waste incineration are the major
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J.L. Guentzel et al. / Science of the Total Environment 388 (2007) 316–324
anthropogenic sources of mercury (NAS 2000, US EPA
1997). Atmospheric deposition of wet and dry species is
the primary delivery mechanism of inorganic Hg to ecosystems. In highly industrialized regions local sources may
contribute significantly to inorganic Hg deposition (Jensen
and Invefeldt, 1994) while Hg from the global pool contributes more significantly to the deposition in more remote
non-industrialized regions (Guentzel et al., 1995, 2001a).
In addition to atmospheric deposition, mobilization of
mercury from soils as a result of deforestation (biomass
burning and clear-cutting) can be a source of inorganic
and organic Hg to ecosystems during storm events (Friedli
et al., 2003; Porvari et al., 2003; Munthe et al., 2007).
Once deposited to ecosystems, inorganic mercury can
be reduced to gas phase Hg and released back to the
atmosphere via volatilization, become complexed with
terrestrial soils and vegetation or aquatic organic/particulate
matter and settle out of the water column, or be transformed
to methylmercury via anerobically mediated microbial
processes in soils and sediments (Gilmour et al., 1992;
Mason et al., 1995; Guentzel et al., 1996, 1998).
Methylmercury bioaccumulates with increasing trophic
level and comprises 95–100% of the total mercury in
predatory fish (Bloom, 1992). The main source of exposure
to methylmercury in humans is the consumption of fish,
shellfish, and sea mammals (NAS, 2000; Clarkson et al.,
2003). Human health risks associated with methylmercury
poisoning and the occurrence of elevated (N 0.3 ppm) levels
of mercury in marine and freshwater fish have resulted in
worldwide advisories for fish and shellfish (NAS, 2000).
The brain is the primary target tissue for mercury toxicity.
Adults with mercury poisoning may experience blurred
vision, tremors, ataxia, myocardial infarction, and coronary
heart disease (Yoshizawa et. al., 2002; Clarkson et al., 2003;
Virtanen et al., 2007). Pre- and/or post-natal exposure to
methylmercury in children can be associated with decreased visual memory recognition in infants (Oken et al.,
2005), delayed auditory response, and deficits in motor
function in children through age 14 (Murata, et al., 2004,
1999; Grandjean et al., 1998).
The purpose of this project was to determine the levels
of mercury in water, sediment, and biota from the Alvarado
Lagoon System and to characterize the mercury exposure
of the individuals that reside in these communities. In 2002
personnel with the Consejo de Desarrollo del Papaloapan
(Papaloapan Basin Development Commission; CODEPAP), an agency of the government of the State of
Veracruz, reported to two of us (EOK and KMK) their
suspicion that the waters of the ALS were contaminated
with mercury (Eduardo Santaella, pers. com.), having
obvious implications for the health of the human inhabitants there. There are a large number of indigenous river-
317
bank communities within the ALS that rely mainly on
agriculture and fishing for comestible and economic subsistence. Vasquez et al. (1998) examined the concentrations
of major and trace elements, not including mercury, in the
ALS, and found cadmium and lead concentrations in the
water were higher than the established values of the
Secretaria de Medio Ambiente Recursos Naturales y Pesca
(SEMARNAP). Thus, it became of interest to determine
the degree of contamination, if any, of the ALS by mercury.
The ALS is an agricultural area, with sugar cane cultivation
and cattle ranching being the primary economic activities
other than fishing. There are no local sources of mercury
and the nearest urban areas are the cities of Veracruz
(50 km), Oaxaca (250 km) and Puebla (300 km). Water and
fish samples were collected during the wet (September
2005) and dry (March 2003 and 2005) seasons. Hair samples, dietary surveys, and sediment samples were obtained
during the 2005 wet and dry seasons. These are the first
reported mercury levels from this lagoon system and our
findings will provide a baseline for future studies in the
region as this ecosystem is beginning to experience anthropogenic stress due to expanding urban zones, increased
agricultural activities, and mangrove deforestation (Castaneda and Contreras, 2001; Cruz-Escalona et al., 2007).
2. Materials and methods
2.1. Study area
The Alvarado Lagoon System is a large mangrove
(Rhizophora mangle, Avicennis germinans, Laguncularia
racemosa) dominated coastal wetland formed by the
confluence of four rivers (Papaloapan, Blanco, Acula,
Limon) that descend from the central Mexican cordillera
(Fig. 1). The ALS is located in southern Veracruz state,
Mexico and flows parallel to the northwestern coastline of
the Gulf of Mexico. It is a shallow system (2 m) connected
to the Gulf of Mexico via a 0.4 km wide sea channel. The
ALS has a maximum width of 4.5 km and a mean surface
area of 62 km2. Approximately 50× 109 m3 of water flow
through the system each year and the estimated water
exchange time in the ALS is 0.5 days (Moran-Silva et al.,
2005; Cruz-Escalona et al., 2007).
The mean annual temperature ranges from 22 to 26 °C
and the average summertime precipitation ranges from
110 to 200 cm. The rainy season occurs from June to
September and the dry season occurs from March to June.
The ALS is affected by high velocity northern winds (90–
129 m/s) from October through February (Vazquez et al.,
1998; Moran-Silva et al., 2005; Cruz-Escalona et al.,
2007). This is one of the most productive estuarine-lagoon
systems in the Mexican Gulf of Mexico. There are two
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Fig. 1. Map of the Alvarado Lagoon system (ALS) Veracruz, Mexico. Water and fish samples were collected during the wet (2005) and dry (2003 and
2005) seasons. Hair samples, dietary surveys, and sediment samples were obtained during the wet and dry seasons of 2005. The letters on the map
denote sampling locations within the ALS.
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periods of high productivity that are associated with the
dry season and the north winds season. The dominant
energy pathway through the system is primary production
associated with seagrass beds (Ruppia maritima) (CruzEscalona et al., 2007). The ALS is an internationally
recognized conservation site for many threatened species
and sustains the largest manatee (Trichechus manatus)
population in Veracruz state. It is becoming anthropogenically stressed due to mangrove deforestation, intensive fishing activities, expanding urban and tourism
zones, and poor waste management practices (Castaneda
and Contreras, 2001; Cruz-Escalona et al., 2007).
2.2. Sample collection
Samples were collected from the ALS during the March
2003 (stations B, C, G, H, I, J, K, L, M, N, Q, R, T, U, W, Y,
AA, BB, CC) and March 2005 (stations B, D, J, L,R, T, V,
W) dry seasons and the September 2005 (stations B, D, J,
L, R, T, U, V, W) wet season (Fig. 1). Not all stations were
sampled during each collection period due to time constraints and logistical issues. Surface water samples for total
unfiltered Hg were collected in acid washed Teflon bottles
using ultra clean collection protocols (Guentzel et al., 1996,
2001b). Additional unfiltered surface water samples were
collected for total carbon analysis (TC), total suspended
solids (TSS), pH, and salinity. The samples for TC analysis
were collected in pre-combusted dark vials. The TSS, pH,
and salinity samples were collected in polyethylene bottles
(Guentzel et al., 1996). All water samples were kept on ice
in the field and frozen upon return to the field station.
Sediment samples were collected during the March
2005 dry and September 2005 wet season using a stainless
steel Widlco sediment dredge (Ben Meadows Company;
Janesville, WI, USA). The samples were placed in precleaned glass jars and sealed with Teflon lined screw caps.
Fish samples from the ALS were purchased from local
fishermen during the March 2003 and 2005 dry season
and during the September 2005 wet season. The fish and
sediment samples were kept on ice and frozen upon return
to the laboratory.
Hair samples were collected, on a voluntary basis, from
adults and children during the March 2005 dry and September 2005 wet season. A section of hair (1–3 cm) was
clipped close to the scalp in the occipital region of the head.
Hair segments ranging from 1 to 3 cm generally represent a
1–3 month period of recent exposure (Murata et al., 1999).
Each hair sample was placed in an acid washed polycarbonate vial and sealed with a Teflon lined screw cap lid.
The samples were stored in a cool, dry, dark location prior
to analysis. Dietary surveys were conducted at the time of
hair collection. The questions contained in the dietary
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survey included: gender, age, the number of fish meals per
month, the number of shellfish meals per month, what
percentage of fish and shellfish consumed originated from
the ALS, hair color, and chemical treatment of hair. The
collection of the hair samples was approved by the Nova
Southeastern University Institutional Review Board (Research Protocol #OSC02040506EXP) and by the University of Veracruz, Xalapa, Veracruz, Mexico.
2.3. Sample digestion and analysis
Unfiltered water samples collected for total Hg analysis
were thawed and immediately acidified with dilute aqua
regia, hermetically sealed in the Teflon bottles, and placed
in a low wattage UV flux chamber for 48 h. The mercury in
the samples was reduced to elemental Hg via NaBH4
reduction, pre-concentrated using gold amalgamation, and
quantified using a Tekran CVAFS detector (Guentzel et al.,
1995, 1996, 2001a,b; Landing et al., 1998). The analytical
detection limit, based on three times the standard deviation
of the purge blank, was 0.1 ng/L. Aqueous phase Hg
standards gave recoveries of 95 ± 5% relative to injections
of gas phase elemental Hg. Total carbon (TC) and total
inorganic carbon (TIC) in unfiltered water samples were
determined using a Shimadzu 5000A total carbon analyzer.
Total organic carbon (TOC) was determined by subtracting
the TIC concentration from the TC concentration. Total
suspended solids were quantified by filtration using a
0.45 μM polycarbonate filter, drying to constant weight,
and gravimetric determination. Salinity and pH were
measured using ion selective electrodes.
Fish muscle, sediment, and hair samples were digested
in closed Teflon digestion vessels using a CEM microwave
digester. The digestion matrix was a mixture of 6 M ultra
clean HCl, 15 M ultra clean HNO3, and ultra-pure water.
The digests were analyzed using NaBH4 reduction, preconcentration via gold amalgamation, and quantification
using a Tekran CVAFS detector (Guentzel et al., 1995,
1996; Landing et al., 1998; Guentzel et al., 2001a,b). The
analytical detection limits were: Hair 0.004 μg Hg/g dry;
Sediment 0.003 μg Hg/g dry; and Fish 0.008 μg Hg/g wet.
Digestion and analysis of standard reference materials
yielded recoveries of 93 ± 7% (n = 8) for NIST 2701 Marine Sediment; 99± 1% (n = 5) for NIST 2709 San Joaquin
Soil; and 101 ± 2% for NIST 2976 Marine Mussel Tissue.
3. Results and discussion
3.1. Aqueous phase
Unfiltered total Hg, TSS, and organic carbon are
removed from the water column as salinity increases
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Fig. 4. The concentrations of total unfiltered Hg in the Rio Limon and
Rio Papaloapan during the wet and dry seasons. The samples with error
bars are the mean and standard deviation of replicate field samples. The
letters on the x-axis refer to the stations on the map in Fig. 1.
Fig. 2. The distribution of total Hg (A) total suspended solids (TSS)
(B), and total organic carbon (TOC) (C) as a function of salinity in the
Alvarado Lagoon. The samples are unfiltered.
0.9 to 12.6 ng/L, with higher concentrations associated
with the turbid organic rich river end-members or
higher TSS loadings in the brackish mixing zones
(Fig. 2A,B,C). Levels of total Hg from other estuaries
that discharge into the northern Gulf of Mexico are
comparable to the ALS. Guentzel et al. (1996) report
(Fig. 2A,B,C). This removal is most likely associated with
direct sedimentation of particulate species or scavenging of
dissolved species onto particles and subsequent removal
from the water column via sedimentation (Guentzel et al.,
1996). The samples were slightly alkaline with pH ranging
from 7.9 to 8.5. TSS and organic carbon ranged from 157.4
to 1.0 mg TSS/L and 59.9 to 1.1 mg C/L, respectively,
with higher loadings at or near the river end-members
(Fig. 2A,B,C). Levels of total unfiltered Hg range from
Fig. 3. The relationship between total unfiltered Hg and total suspended
solids (TSS) in the lagoon (R2 = 0.82; p b 0.001; y = 0.0813x + 1.134).
The linear regression was calculated using SigmaStat 3.5.
Fig. 5. The concentrations of Total unfiltered Hg in the Alvarado Lagoon
(I, T, BB), Gulf of Mexico (AA), Rio Acula (B,C, D, G, H), and Rio
Blanco (R). The letters correspond to the station locations on the map in
Fig. 1. The samples with error bars are the mean and standard deviation of
replicate field samples.
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values of total Hg ranging from 1 to 7 ng Hg/L in the
Ochlockonee estuary (north Florida) and levels in
Galveston Bay (Texas) range from 0.2 to 5 ng Hg/L (Han
et al., 2006). The turnover time of total Hg, with respect to
the water column, in the ALS is 0.9 days (assuming an
average concentration of 1.7 ng Hg/L, a water column
volume of 1.24 ×108 m3 water, and a flushing rate of
50× 109 m3 water/yr). The levels of total Hg in the ALS are
not elevated with respect to the US EPA ambient surface
water quality criteria (0.77–1.4 μg Hg/L) (US EPA 2006)
or the Mexican marine aquatic life criteria (0.02 μg Hg/L)
(Jimenez et al., 1999). This is in contrast to other dissolved
metals in the ALS. Concentrations of Cd (1.5–3 μg/L), Cu
(5–60 μg/L), and Pb (5–120 μg/L) (Vazquez et al., 1998) in
the lagoon were positively correlated with salinity and were
above the Mexican marine aquatic life criteria of 0.9 μg
Cd/L, 3 μg Cu/L, and 6 μg Pb/L (Jimenez et al., 1999).
Total Hg is significantly (R 2 = 0.82; p b 0.001)
correlated with suspended matter in the water column
(Fig. 3). This correlation explains 82% of the variance in
the data and suggests that particulate matter is a carrier
phase for Hg in the wet and dry season. Concentrations
of Hg (0.9–10.4 ng/L) in the Alvarado Lagoon, Rio
Limon, Rio Aula, and Rio Blanco during the March
2003 and 2005 dry seasons are similar to the September
2005 wet season (1.9–4.9 ng Hg/L) (Figs. 4 and 5), with
higher Hg levels associated higher levels of particulate
matter (Fig. 3). Although the data are limited, levels of
Total Hg and TSS in the Rio Papaloapan (stations U, V,
W) during the wet season (10.9–12.7 ng Hg/L, 89.1–
154.7 mg TSS/L) are higher than the dry seasons (0.9–
2.7 ng Hg/L; 4.8–39.7 mg TSS/L) (Fig. 4). Sites U, V,
and W from the Papaloapan River were sampled within
12 h of a night-time rainfall (15 cm) event during the
September 2005 wet season. The elevated Hg concentrations at these three stations are likely a result of
increased particulate matter transport down the estuary
during high flow conditions and or input of dissolved
and particulate Hg from precipitation. A Mercury
Deposition Network (MDN) monitoring site in Huejutla
(HD01), located within 400 km of Alvarado, reported
a rainfall Hg concentration of 11.4 ng/L for the week of
8/30/2005 to 9/06/2005, which corresponds to our
September 2005 collection period. The annual 2005
Hg deposition to this region was 10.9 μg Hg/m2/yr
(www.nadp.sws.uius.edu). There was no measurable
precipitation during the March collection periods.
3.2. Sediment
Surface sediments from the ALS were a mixture of
sand, mud, and shells. The sediments did not contain
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Fig. 6. Total Hg concentrations of sediment samples. Stations C, D, and B
are from the Rio Acula, stations J and L are from the Rio Limon, stations U,
V, W, are from the Rio Papaloapan, station R is from the Rio Blanco, and
station T is from the Alvarado Lagoon. The letters correspond to station
locations on the map in Fig. 1. The samples with error bars are the mean and
standard deviation of replicate field samples. There is a significant relationship between the sediment concentrations of total Hg and total carbon for
the March 2005 sampling period (R2 =0.435; p=0.020; y=37.244+
5.264x). The linear regression was calculated using SigmaStat 3.5.
noticeable levels of H2S, via olfactory inspection, at the
time of collection. Total Hg in the sediments ranged from
27.5 to 90.5 ng Hg/g dry weight with no significant difference between the 2005 wet and dry seasons (Fig. 6).
These values are within the US EPA background sediment
criteria of 0–300 ng Hg/g dry (US EPA 1997) and are
below the threshold effects level for marine sediments
(130 ng Hg/g dry) (Buchman 1999). Rosas et al. (1983)
report similar values of total Hg (28± 12 ng Hg/g dry) for
surface sediments in the Mandinga Lagoon located approximately 50 km north of the ALS. Values of total Hg in
surface sediments from the mangrove dominated Cienaga
Grande de Santa Marta estuary and the Magdalena River
(Columbia) range from 24 to 100 ng Hg/g dry (Perdomo
et al., 1998; Alonso et al., 2000). The carbon content of the
ALS sediments ranged from 1 to 8%. Similar values for %
organic matter have been reported for the ALS (RosalesHoz et al., 1985) and for other mangrove dominated coastal
ecosystems (Perdomo et al., 1998). There was a mild, but
significant, correlation between total Hg and % carbon for
the March 2005 samples (R2 = 0.435; p = 0.020), suggesting
that Hg is associated with organic matter on the solid phase.
A similar relationship (R2 = 0.518; p = 0.039) has also been
observed in sediments from the Cienaga Grande de Santa
Marta estuary (Columbia) (Alonso et al., 2000).
3.3. Biota and hair
Levels of total Hg in seafood from the ALS range
from 0.01 to 0.35 μg Hg/g wet and do not vary substantially from wet to dry season (Fig. 7). Although the
sample sized is limited, the types of fish and shellfish
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analyzed represent 87% of the annual catch from the
ALS (Cruz-Escalona et al., 2007). The invertebrate
species sampled (shrimp, blue crab) are representative
of trophic level 2 and the vertebrate fish species sampled
represent trophic levels 3–4 within the ALS (Manickchand-Heileman et al., 1998). Concentrations of total Hg
in shellfish harvested from the ALS range from 0.01 to
0.07 μg Hg/g wet (Fig. 7). Rosas et al. (1983) report
values of total Hg (0.07 ± 0.19 μg Hg/g wet) for oysters
in the Mandinga Lagoon located approximately 50 km
north of the ALS. The levels of total Hg in piscivorous/
omnivorous fish (Fig. 7) from the lagoon range from
0.07 to 0.35 μg Hg/g wet. The catfish (0.29 μg Hg/g
wet) and moharra (0.3–0.35 μg Hg/g wet) are at or
slightly above the recommended consumption limit of
0.3 μg Hg/g wet (NAS, 2000). The levels of moharra in
the ALS are higher than values reported for Cartagena
Bay, Columbia (0.06–0.167 μg Hg/g wet) (Alonso et al.,
2000) and the San Jose Lagoon, Puerto Rico (0.02–
0.11 μg Hg/g wet) (Rodrigues-Sierra and Jimenez,
2002).
Hair samples were collected from 47 individuals
during the 2005 wet (September) and dry (March) seasons. Individuals reported that their diet contained an
average of 12 ± 6 seafood meals per month and approximately 50% of their seafood meals contained shellfish
(47 ± 23) and 50% (52 ± 22%) contained fish. A large
majority (86%) of individuals surveyed reported that 75 to
100% of the seafood they consumed originated from the
ALS. The levels of total Hg in hair ranged from 0.10 to
3.36 μg/g (n = 47) (Fig. 8) and 58% of the samples were
above the US EPA reference dose of 0.1 μg Hg/kg body/
day which corresponds to 1.00 μg/g in hair (NAS, 2000).
A total of 27 adults (ages 19–59) had a mean hair
concentration of 1.48 ± 0.86 μg/g Hg, with a range of 0.36
to 3.36 μg/g. A total of 20 children (ages 2–18) had a
mean hair concentration of 1.12 ± 0.62 μg/g Hg with a
range of 0.18 to 2.57 μg/g. Mean levels of total Hg in hair
for sub-groups of adults and children within the ALS
ranged from 1.0 to 1.7 μg/g (Fig. 9). The results from this
study are similar to other biomarker studies from
populations that experience low to moderate level Hg
exposure via fish consumption. Hair Hg levels in children
(ages 0–12) from non-gold mining Amazon riverside
villages ranged from 0.39 to 5.16 μg/g (n = 21) (Pinheiro
Fig. 8. Levels of total Hg in hair during the 2005 wet and dry season
(n = 47). Adult represents ages 19–59 and Child represents ages 2–18.
None of the individuals reported that their hair had been chemically
treated and only one individual had gray hair. All other hair colors
were black.
Fig. 9. Mean levels of total Hg in hair for adults and children (gray
bars) and sub-groups within the adults and children (black bars).
Adults n = 27; children n = 20; ages 2–7, n = 5; ages 8–12, n = 10; ages
13–18, n = 4; ages 19–29, n = 4; ages 30–39, n = 10; ages 40–49,
n = 6; ages 50–59, n = 8).
Fig. 7. Total Hg concentrations in seafood from the Alvarado Lagoon.
Brown shrimp (Peneus aztecus) (n=20, March 2003; n=18, March 2005;
n=20, September 2005), Bay Squid (Lolliguncula brevis) (n=3), Blue crab
(Callinectes rathbunae) (n=3), White mullet (Mugil curema) (n=2),
Sheepshead (Archosargus probatocephalus) (n=1), Big mouth sleeper
(Gobimorus dormitor) (n=2), Fat snook (Centropomus parallelus) (n=2),
Spine snook (Centropomus ensiferus) (n=1), Stripped moharra (Eugerres
plumeri) (n=3, March 2003; n=2, March 2005), Catfish (Bagre marina)
(n=1).
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et al., 2007) and hair Hg levels ranged from 0.15 to
1.25 μg/g in adults from Canadian coastal communities that consumed fish containing low levels of Hg
(≤0.2 μg/g) (Legrand et al., 2005).
No significant (p N 0.05) correlations were observed
between the Hg levels in hair and age, gender, wet and
dry season, or seafood meals consumed. Variability in
the relationship between diet and Hg levels in hair may
reflect differences in short-term fish consumption and
concentrations of Hg in hair segments, which represent
longer term periods of Hg exposure (Mergler et al.,
2007). Seasonal variations in hair Hg levels have been
observed in sequential hair segments of individuals that
consumed mainly piscivorous species, containing 0.29–
0.71 μg Hg/g during the wet season and herbivorous
species, containing 0.07–0.14 μg Hg/g during, the dry
season (Lebel et al., 1997). Individuals within the ALS
reported consuming a mixture of piscivorous/omnivorous fish ranging from 0.1 to 0.35 μg Hg/g and shellfish
ranging from 0.01 to 0.07 μg Hg/g during the wet and
dry seasons. The hair levels (0.1–3.36 μg Hg/g) from
individuals in this study represent a 1–3 month
weighted average of exposure resulting from consumption of seafood containing mercury concentrations at or
below 0.3 μg Hg/g. The findings from this study suggest
that individuals who frequently consume fish and shell
fish containing low levels of Hg (b0.3 μg/g) can accumulate low to moderate body burdens of Hg, as indicated by hair Hg concentrations N 1.0 μg/g, and may be
at risk for experiencing low dose mercury toxicity.
Acknowledgements
Work in 2003 was funded by Nova Southeastern
University Faculty Development Fund (Edward Keith
(EOK)) and Coastal Carolina University Professional
Enhancement Funding (travel funding for Jane Guentzel
(JLG)). Work in 2005 was supported by an NSU President's Faculty Scholarship Award to EOK and JLG.
Additional funding for instrumentation was awarded to
JLG by NSF/MRI: Division of Ocean Sciences (award
#0079658; funding period 09/01/2000 to 08/31/2004)
and the South Carolina Higher Education Commission
(SCRIG #R99-09T; funding period 01/01/2000 to 07/
31/2001). We thank Mr. Eduardo Santaella and Lic.
Juan Manuel Irigoyen, Director, Papaloapan River
Basin Development Commission CODEPAP), Xalapa,
Ver., for the generous use of their field station. We
acknowledge the laboratory assistance of Coastal Carolina University undergraduate students James Patanio,
Lacie Armstrong, Andy Deffobis, Rebecca Allen, Sean
Briggs, Eric Mazzone, Angela Cruciano, and Griffin
323
Meincke. We also thank Dr. Richard Moore for his
assistance with fish identification. We gratefully acknowledge Bianca Cortina, Claudia Rodriguez, Marco
Zavala, Alejandro Palacios, and Daniel Palacios for their
assistance with the collection of samples.
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