Why study sedimentary metal bioavailability? Coastal sediments are - - PowerPoint PPT Presentation

Application of radiotracer methodology for

understanding the influence of geochemical fractionation on metal bioavailability in estuarine sediments Nicholas Fisher and Zofia Baumann School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, New York USA

Why study sedimentary metal bioavailability?

• Coastal sediments are enriched with toxic metals (relative to
• verlying water)
• Potentially important source of metals to marine organisms
• Conduit for animals higher in the food chain, including humans

Location Kd [L kg-1] As Cd Cr Mare Island 9.12 x 102 4.61 x 103 3.08 x 105 Baltimore Harbor 2.41 x 104 5.94 x 103 9.52 x 105 Elizabeth River 2.24 x 102 0.90 x 102 4.01 x 104

MI ER BH

MI – Mare Island in San Francisco Bay, CA; BH – Baltimore Harbor, MD; ER – Elizabeth River, Norfolk, VA

Objectives

• 1. To compare the relative importance of

aqueous and dietary sources of metal (73As,

109Cd and 51Cr) for the polychaete Nereis

succinea

• 2. To study the geochemical fractionation of

metals in estuarine sediments and relate these to metal assimilation in Nereis succinea

• 3. To study chemical composition of the gut

fluid, its extracting capabilities for particle- associated metals, and its influence on metal assimilation into tissues

Radiotracer approach

• Gamma – emitting radioisotopes: 73As, 109Cd and 51Cr
• Used in low concentrations << 0.01% of background

metal concentrations

• Quick, accurate and non-destructive analysis, well-suited

for kinetic studies of metal uptake and release in different compartments

convenience + low biological variability!

Radiolabeling of worm food

73As 109Cd 51Cr

Radiolabeled algae Sediment + algae Sediment + dissolved isotope Goethite + dissolved isotope WORM FOOD

Thalassiosira pseudonana centric diatom Dissolved radioisotopes

Food: fresh algae, goethite, and sediment with or without added radiolabeled algae, aged for 2 & 30 days

Pulse-chase feeding experiments

 to determine AE and kef

2 30 2 30

Well-type NaI gamma detector

Assimilation efficiencies in Nereis succinea

Unamended sediments Sediments mixed with algae 2 d 30 d 2 d 30 d ER

73As

1.2 ± 1.05 nd 69.7 ± 9.7 16.8 ± 4.1 BH 7.8 ± 6.2 6.59 ± nd 51.6 ± 11.6 30.1 ± 1.4 MI 10.2 ± 6.8 12.1 ± 12.5 50.7 ± 9.0 24.0 ± 12.2 algae 72.41 ± 3.30 goethite 2.48 ± 0.68 ER

109Cd

30.8 ± nd 43.6 ± 16.4 9.9 ± 3.5 21.5 ± 6.1 BH 1.5 ± 1.29 2.4 ± nd 68.7 ± nd 21.6 ± 14.9 MI 46.1 ± 18.7 58.9 ± 6.6 9.4 ± 4.0 7.6 ± 4.6 algae 22.91 ± 19.73 goethite 24.15 ± 1.78 ER

51Cr

4.5 ± nd 1.0 ± 0.5 0.9 ± 0.2 3.6 ± 1.7 BH 4.2 ± 3.3 4.6 ± nd 1.2 ± nd 0.8 ± 1.0 MI 4.0 ± 3.1 0.7 ± 1.3 5.0 ± 2.7 0.3 ± 0.6 algae 2.8 ± 1.6 goethite 34.2 ± 6.5

< 3-70x from sediments mixed with algae no consistent pattern

unamended sediments = sediments mixed with algae

f ef w ew u ss

C g k IR AE C g k k C       

w ew u w ss

C g k k C   

, f ef f ss

C g k IR AE C    

,

Biokinetic model

from water: from food: % 100 %

, 

 

ss f ss

C C dietary Wang et al. 1996

Dietary metal contribution to bioaccumulation

location metal age AE from food from water dietary days % µg g-1 ng g-1 % BH As 2 7.8 23.1 0.12 100 30 6.6 34.7 0.12 100 Cd 2 1.5 0.3 0.0005 100 30 2.4 0.4 0.0005 100 Cr 2 4.2 113.0 0.007 100 30 4.6 149.6 0.007 100 ER As 2 1.2 1.0 173.1 85.5 Cd 2 30.8 0.4 0.17 100 30 43.6 1.1 0.17 100 Cr 2 4.5 15.9 0.37 100 30 1.0 86.8 0.37 100 MI As 2 10.2 0.6 1.76 99.7 30 12.1 0.7 1.76 99.8 Cd 2 46.1 25.0 0.002 100 30 58.9 9.0 0.002 100 Cr 2 4.0 88.6 0.02 100 30 0.7 14.7 0.02 100

~100% from food!

unamended sediment

location metal age AE from food from water dietary days % µg g-1 ng g-1 % BH As 2 51.6 112.1 0.12 100 30 30.1 65.5 0.12 100 Cd 2 68.7 0.6 0.00 100 30 21.6 0.1 0.00 100 Cr 2 1.2 29.9 0.01 100 30 0.8 86.0 0.01 100 ER As 2 69.7 15.3 173.1 98.9 30 16.8 6.6 173.1 97.4 Cd 2 9.9 2.0 0.9 100 30 21.5 0.2 0.2 99.9 Cr 2 0.9 154.9 0.4 100 30 3.6 59.6 0.4 100 MI As 2 50.7 5.7 1.76 100 30 24.0 5.7 1.76 100 Cd 2 9.4 10.2 0.002 100 30 7.6 12.3 0.002 100 Cr 2 5.0 61.6 0.02 100 30 0.3 32.4 0.02 100

Dietary metal contribution to bioaccumulation

~100% from food!

sediment with algae

sediment 2 g wet wt extraction conditions phases intended to extract 1 M MgCl2 pH=7; 1h exchangeable carbonate 1 M NaOAc pH=5; 1h acid volatile sulfides 0.5 M HCl; 30 min Fe/Mn oxides Hydroxylamine/ NaOAc; 6 h @ 96 °C

• rganic I

1 M NaOH; 8 h @ 80 °C

• rganic II

5 M H2SO4; 6 h residual sediment pyrite 11 M HNO3; 2 h

Cutter et al., in prep.

20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

“carbonex”

• rganic

AVS

pyrite

• xides

%

2d 30d 90d algae 2d 30d 90d algae 2d 30d 90d algae Baltimore Harbor Elizabeth River Mare Island

As Cd Cr

% in exchangeable + carbonate fractions 20 40 60 80 100 AE [%] 20 40 60 80

Linear regression, p <0.05 Baumann and Fisher, 2011

Data for all sites, treatments, metals combined

% of metal in oxides (AVS + Fe/Mn oxides) 10 20 30 40 50 60 70 80 AE [%] 10 20 30 40 50

Linear regression, p <0.05 Baumann and Fisher, 2011

Data for sediments labeled by algae from all sites and metals combined

single & combined fractions

1 2 3 4 5 6 7 8 9 10 11 12 13

slope of regression

• 0.4
• 0.2

0.0 0.2 0.4

Baumann and Fisher, 2011

exchangeable carbonate

• xides
• rganic II

pyrite exchangeable + carbonate = “carbonex” exchangeable + carbonate + AVS

• xides

+ AVS pyrite + residue

Regression of assimilation efficiency and extracted fraction of metal (all sites, treatments, metals combined)

w ew u w ss

C g k k C   

,

NEW

from water: from food:

Geochemical biokinetic model

f ef i i w ew u ss

C g k IR b z C g k k C        

f ef i i f ss

C g k IR b z C     

,

zi - % of metal in fraction “i”; bi - slope of regression between AE and zi

carbonex total

Directly labeled Algae labeled Metal concentrations in worms; model predictions vs. field measurements (all sites and metals)

gut fluid seawater

mmol kg-1 200 400 600 2200 2300 2400 Cl- SO4

2-

K+ Na+ Ca2+ Mg2+

Chemical composition of the gut fluid

gut fluid: seawater ratio 0.9 5.7 10.1 4.9 4.5 5.0

gut fluid pH= ~7; [AA] = 2.46 mg L-1

Amino Acid

gut fluid (GF) BSA

BSA : GF mean ± SD [mmol/L ] mean ± SD [mg/L] % of total AA in gut fluid [g/g] % of total AA in BSA

Alanine

3.891 ± 0.231 0.35 ± 0.02

14.2

0.082 6.6

0.5 Arginine

1.244 ± 0.017 0.22 ± 0.00

8.9

0.069 5.6

0.6 Aspartic Acid

1.466 ± 0.385 0.20 ± 0.05

8.1

0.102

8.2 1.0 γ-Aminobutyric Acid

0.010 ± 0.017 0.001 ± 0.002 0.04

• Glutamic Acid

1.641 ± 0.199 0.24 ± 0.03

9.8

0.024 2.0

0.2 Glycine

2.984 ± 0.239 0.22 ± 0.02

8.9

0.029 2.3

0.3 Histidine

0.714 ± 0.151 0.11 ± 0.02 4.5 0.135

10.9 2.4 Isoleucine

2.955 ± 0.649 0.39 ± 0.09

15.9

0.0356 2.9

0.2 Leucine

1.161 ± 0.055 0.15 ± 0.01 6.1 0.179

14.4 2.4 Lysine

0.758 ± 0.538 0.11 ± 0.08 4.5 0.195

15.7 3.5 Methionine

0.119 ± 0.206 0.02 ± 0.03 0.8 0.000 0.0

0.0 Phenylalanine

0.488 ± 0.042 0.08 ± 0.01 3.3 0.103

8.3 2.6 Serine

1.281 ± 0.018 0.13 ± 0.00 5.3 0.052 4.2

0.8 Threonine

0.941 ± 0.102 0.11 ± 0.01 4.5 0.067 5.4

1.2 Tyrosine

0.257 ± 0.022 0.05 ± 0.00 2.0 0.089 7.2

3.5 Valine

0.693 ± 0.011 0.08 ± 0.00 3.3 0.078 3.3

1.0 Σ AA

20.6 mmol L-1 2.46 mg L-1 1.242

Amino acid composition of gut fluid and bovine serum albumin

BSA data from Shi et al., 2006

1 2 3 4 5 10 15 hours 1 2 3 4 5 10 15 20 25 1 2 3 4 % 73As released 10 20 30 40 50 60 70

Release of 73As from particles to solution

sediment + algae sediment + dissolved isotope goethite + dissolved isotope

assimilation efficiency

water BSA BSA + Cl- gut fluid

Summary

1.Nearly all of bioaccumulated metal ( >98%) comes from diet. 2.Sedimentary metals in the easily extractable pool (“carbonex”) are most bioavailable for polychaetes; metals associated with iron oxides are not readily bioavailable. 3.Metal release from ingested particles into gut fluid is a necessary but not sufficient step to explain metal assimilation in worms.