HOANG THI QUYNH DIEU ANALYSIS AND ASSESSMENT THE …hueuni.edu.vn/sdh/attachments/article/1225/TomTat_EN.pdf · 2020-02-20 · The abstract of doctoral dissertation Hoang Thi Quynh

The abstract of doctoral dissertation Hoang Thi Quynh Dieu

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ticersini

HUE UNIVERSITY

COLLEGE OF SCIENCES

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HOANG THI QUYNH DIEU

ANALYSIS AND ASSESSMENT THE

BIOACCUMULATION OF COPPER AND LEAD BY

BIVALVE (Meretrix lyrata) CULTURED IN TIEN

ESTUARY

THE ABSTRACT OF DOCTORAL DISSERTATION

HUE - 2018


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HUE UNIVERSITY

COLLEGE OF SCIENCES

----------------------------------------------

HOANG THI QUYNH DIEU

ANALYSIS AND ASSESSMENT THE

BIOACCUMULATION OF COPPER AND LEAD

BY BIVALVE (Meretrix lyrata) CULTURED IN

TIEN ESTUARY

MAJOR: ANALYTICAL CHEMISTRY

CODE: 62 44 01 18

THE ABSTRACT OF DOCTORAL

DISSERTATION

SCIENTIFIC SUPERVISORS:

1. Assoc. Prof. Dr. NGUYEN VAN HOP

2. Dr. NGUYEN HAI PHONG

HUE - 2018


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INTRODUCTION

Toxic metals (Hg, Cd, Ni, As, Cr, Pb, Cu and Zn) from

environment (water, soil, sediment) could be bio-accumulated by

organism through food chain and affect human and animal health.

These metals originate from natural and/or anthropogenic sources

such as weathering of rock/soil and volcanic activity; industrial

processing of minerals and ores, industrial use of metals and metal

complexes… Sediments in rivers, lakes, oceans and especially

estuaries are accounted for the sinks of toxic metals in aquatic

ecosystems.

In Vietnam, many bivalve species are cultured on a large

scale in estuarine areas, such as the Tien Estuary in the Tan Thanh

Commune of the Go Cong Dong District in Tien Giang Province,

South Vietnam. This area is where the Tien River - a tributary of the

Mekong River - meets the sea. For years, this estuary has served as

one of the focal areas for culturing clam (Meretrix lyrata) in South

Vietnam, with an average yield of 20,000 tons per year for domestic

consumption. The culture cycles of M. lyrata range from 8 to 10

months.

To date, few studies have examined the toxic metal

bioaccumulation in M. lyrata cultured in the Tien Estuary.

Especially, the accumulation of metal in sediment and M. lyrata;

metal speciation in sediment and bioavailability of them; the

potential of M. lyrata to assess sediment contamination with toxic

metals have not yet investigated. In recent years, the Centre of

environment monitoring of Tien Giang province and nearby

provinces have held many campaign of water monitoring for the Tien

River, but none of them have enough information about toxic metals

to assess their pollution level and effects on the estuarine water

environment.

To clarify these above issues, the dissertation was conducted

with the purpose of providing information about: level of toxic

metals in water, sediment and M. lyrata; metal speciation in

sediment; the potential of using M. lyrata as a biomonitor to assess

sediment contamination with toxic metals (particularly copper and

lead) in Tien estuary.


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The main objectives of our study were:

1) Assessment of the concentration of Fe, Mn and toxic metals

(Cd, As, Pb, Ni, Cr, Cu, Zn) in water of Tien River and Tien estuary;

2) Assessment of the toxic metals speciation in sediment

3) Assessment of the toxic metals accumulation in M. lyrata

cultured in Tien estuary

4) Assessment of the rate of copper and lead accumulation in

M. lyrata through experiment of exposure to seawater or seawater –

sediment environment added with different dissolved metal levels.

Examining the potential of using M. lyrata as a biomonitor to assess

sediment contamination with copper and lead in Tien estuary.

Structure of the dissertation

The study consists of 116 pages, 39 tables and 25 figures, of

which there are:

8 pages of index, list of tables, figure and abbreviation

3 pages of introduction

28 pages of literature review

16 pages of research subjects and methodology

51 pages of result and discussion

02 pages of conclusion

16 pages of reference, with 179 references

CONTENTS

CHAPTER 1. LITERATURE REVIEW

Sources of toxic metals in the environment;

Metal speciation in the environment;

Toxic effects of toxic metals on human health;

Accumulation of toxic metals in organism, bioindicator for

toxic metal pollution and related studies;

Introduction of Tien river, Tien estuary and white clam

(Meretrix lyrata);

Analytical techniques for toxic metals;

Analytical techniques for determining metal fractions in


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sediment and related studies;

Assessment of toxic metals accumulation in sediment and

organism.

CHAPTER 2. RESEARCH SUBJECTS AND

METHODOLOGY

2.1. Specific research subjects

1) Assessment of the concentration of toxic metals (Cd, As,

Pb, Ni, Cr, Cu, Zn), Fe and Mn in water of Tien River and Tien

estuary.

2) Assessment of toxic metals (Cd, As, Pb, Ni, Cr, Cu and Zn)

contamination in sediment by using geochemical load index and

enrichment factor.

3) Assessment of toxic metals speciation in sediment,

including 5 fractions (associated forms): Exchangeable; Carbonate

bound; Fe and Mn oxides bound; Organic matter bound; Residual.

Risk assessment of these metal species to environment and organism.

4) Correlation analysis between the metal species in sediment

and those in M. lyrata. Assessment of the rate of metal accumulation

from the sediment by M. lyrata and the potential risk to the aquatic

environment by using Biota-sediment accumulation factor (BSAF)

and Risk assessment code (RAC).

5) Assessment of the rate of copper and lead accumulation in

M. lyrata through experiment of exposure to seawater or seawater –

sediment environment containing different dissolved metal levels.

Examining the potential of using M. lyrata as a biomonitor to assess

sediment contamination with copper and lead in Tien estuary.

2.2. Research methodology

- Sampling method:

+ Water of Tien River: Sampling was conducted at 5 sites on

Tien River (from Hong Ngu district to Tien estuary with 230 km in

length) in two periods. Each sample was obtained by mixing water

collected (at a depth of 40–50 cm) at three points: at the right and left

banks (the distance between sampling point and bank was 1/4 river


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widths) and in the middle of the river. Sampling and preservation

were performed according to the standard protocol (ISO 5667–

1:2006 and ISO 5667–3:2003)

+ Water of Tien estuary: Sampling was conducted at 7 sites

(S1–S7) in three periods: June, August, and November 2015. Each

sample was obtained by mixing water collected at 2 locations spaced

approximately 1 km apart at each site at a depth of 40–50 cm.

+ Sediment sampling: Sampling was conducted at 7 sites (S1–

S7) in three periods: June, August, and November 2015. Sediments

were sampled using an Ekman grab sampler at 2 locations spaced

approximately 1 km apart at each site at a depth of 0–10 cm (M.

lyrata generally live at this depth). Each sediment sample of

approximately 1 kg wet weight was obtained by mixing sediments

randomly collected at three points of a triangle spaced 1 m apart.

Sampling and preservation were performed according to the standard

protocol (ISO 5667–13:1997 and ISO 5667–15:1999).

+ M. lyrata sampling: Sampling was conducted at 7 sites (S1–

S7) in three periods: June, August, and November 2015. A total of

20–25 M. lyrata clams aged 7–9 months (30 days before harvesting)

and approximately 4 cm in size were collected at each of the two

locations at each sampling site, for an overall sample size of 40–50

individuals. The M. lyrata clams were packed into plastic bags,

preserved at 4°C and transported to the laboratory within two hours.

- Sample preparation method for toxic metals analysis in water

sample (SMEWW–3030); in sediment sample (metal speciation –

Tessier’s method, total metal – EPA 3052); in M. lyrata (FDA-EAM

4.7).

- Analytical methods for determining metals in water –

SMEWW-3125B; in sediment – EPA-6020B; in M. lyrata – FDA-

EAM 4.7.

- Optimization of conditions for ICP-MS analysis of the

metals: optimization of general parameters and mass calibration;

nebulizer flow; collision gas flow; analysis time; washing time.

- Quality control of analytical methods: isotope selection and

calibration range; limit of detection, limit of quantification;

repeatability and trueness.


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Figure 2.1. Tien estuary (study area) and sampling sites

- Assessment of toxic metals contamination level in water and

sediment: based on national guidelines or some indices (Geological

Accumulation Index/Igeo, Enrichment Factor/EF).

- Assessment of toxic metals contamination level in M. lyrata:

based on national guidelines or BSAF index.

- Assessment of the level of copper and lead accumulated in

M. lyrata by the experiment of exposure to the estuary water or the

estuary – sediment environment containing dissolved metal levels

increased in order to examine the potential of using M. lyrata as a

biomonitor of the metal pollution in the Tien estuary environment.

CHAPTER 3. RESULT AND DISCUSSION

3.1 Optimization for analysis conditions of ICP-MS

3.1.1. Optimization of general parameter and mass calibration

3.1.2. Optimization of nebulizer flow

3.1.3. Optimization of collision gas flow

3.1.4 Optimization of analysis time and washing time

The most important instrument settings and parameters used

in the experiments for the ICP-MS instrument are listed in table 3.1


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Table 3.1. Instrumental settings for the ICP-MS instrument

No Parameter Value

1 RF power 1550 W

2 Nebulizer flow 0.96 (L/min)

3 Collision gas flow 5.5 (mL/min)

4 Analysis time 30 (second)

5 Washing time 20 (second)

6 Peristaltic pump 0.3 (round/min)

3.2. Quality Control Analysis

3.2.1. Isotope selection and calibration range

Table 3.2. The equation of the calibration curve

No Element Equation

Y = a*X + b r

1 Cd Y = 6.33*103 X + 1.61*10

2 0.9998

2 Ni Y = 8.25*104 X + 2.11*10

3 0.9999

3 Cr Y = 8.96*104 X + 1.03*10

3 0.9999

4 As Y = 9.63*103 X + 1.44*10

2 0.9999

5 Pb Y = 7.07*104 X + 2.30*10

3 0.9999

6 Cu Y = 6.15*104 X + 2.31*10

3 0.9997

7 Zn Y = 5.03*103 X + 1.41*10

2 0.9997

8 Fe Y = 8.40*104 X + 4.52*10

3 0.9999

9 Mn Y = 9.54*104 X + 2.37*10

3 0.9998

Y: count per second; X: concentration (µg/L); r: the coefficient of correlation

3.2.2. Limit of detection, limit of quantification

Table 3.3. Limit of detection, limit of quantification of ICP-MS

instrument

No Element LOD (µg/L) LOQ (µg/L)

1 Cd 0.03 0.10

2 Ni 0.03 0.10

3 Cr 0.03 0.10

4 As 0.03 0.10

5 Pb 0.03 0.10


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No Element LOD (µg/L) LOQ (µg/L)

6 Cu 0.03 0.10

7 Zn 0.1 0.30

8 Fe 0.1 0.30

9 Mn 0.1 0.30

Repeatability: The results shown that the analysis methods

gained good repeatability. The RSD values obtained in our

laboratory were 1%-14% (for water), 2.6%-14.7% (for sediment) and

2.0%- 8.6% (for M. lyrata); two times lower than ones of 11 – 28%,

calculated by Horwitz equation.

Table 3.4. Limit of detection, limit of quantification of

analytical methods using ICP-MS system

Element River water

(μg/L)

Estuary water

(μg/L)

M. lyrata

(mg/kg)

Sediment

(mg/kg)

Cd 0.3/0.9 0.3/0.9 0.01/0.03 0.001/0.003

Ni 0.3/0.9 1.0/3.0 0.06/0.18 0.005/0.015

Cr 0.3/0.9 0.3/0.9 0.06/0.18 0.005/0.015

As 0.3/0.9 0.3/0.9 0.06/0.18 0.005/0.015

Pb 0.3/0.9 0.3/0.9 0.06/0.18 0.001/0.003

Cu 0.3/0.9 0.3/0.9 0.06/0.18 0.005/0.015

Zn 1.0/3.0 3.0/9.0 1.0/3.0 0.010/0.030

Fe 1.0/3.0 3.0/9.0 1.0/3.0 1.0/3.0

Mn 1.0/3.0 3.0/9.0 1.0/3.0 1.0/3.0

Limit of detection and limit of quantification are presented in the form of

“LOD/LOQ”

Accuracy: For spiked sample, the analysis method had good

trueness with recovery in the range of 98 – 106% for the metal levels

in the water sample; For CRM sample, the analysis had good

trueness with the metal contents found in the 95% confidence

interval of certified values.

3.3. Levels of the metals in Tien River water

- Except Fe, metal levels did not exceed the limit values given

by the national regulation of QCVN 08-MT:2015– MT/BTNMT.


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- The levels of toxic metals determined in the dry season were

higher than those in the rainy season.

- There was an increasing trend of the metals concentrations

from upstream to downstream.

3.4. Levels of the metals in Tien estuary water

- Except Fe, the metal levels did not exceed the limit values

given by the national regulation of QCVN 10-MT:2015/BTNMT.

-The metal concentrations in the first sampling campaign

were significantly higher than those in the other sampling campaigns.

3.5. Toxic metal contents in sediment and M. lyrata

3.5.1. Toxic metal contents in sediment

Concentration (mg/kg dry)

0

5

10

15

20

25

30

35

As Cu PbMetal

S1 S2 S3 S4

S5 S6 S7

Figure 3.9. As, Cu and Pb contents (mg/kg dry weight) in sediment

- All the sediment samples in this study met the regulations

given by QCVN 43:2012/BTNMT for the metal contents.

- The mean metal levels in the sediment (mg/kg dry weight)

followed the order: Zn (60) Cr (46) Ni (22) As (17) Pb (14)

Cu (4.7) Cd (0.05).

- Two-factor variance analysis (ANOVA) indicated that:

During the period of study, the metal contents in sediment were

significantly equal (p > 0,05); However, the metal concentrations at

S1, S4 sites were significantly higher than those at other ones (p <

0,05). It could be rational since the sediments at S1, S4 sites (higher


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terrace) contain more sand than the other sites (30% and 15%,

respectively).

- A linear correlation was found between the metal contents in

the sediment with R = 0.57 – 0.98 (p < 0.01).

Concentration (mg/kg dry weight)

0

10

20

30

40

50

60

70

80

90

Cd* Zn Ni Cr

Metal

S1 S2 S3 S4 S5

S6 S7

Figure 3.10. Cd, Zn, Ni and Cr contents (mg/kg dry weight) in

sediment; * Cd content presented as µg/kg dry weight)

3.5.2. Toxic metal accumulation in sediment

Table 3.15. Igeo values for toxic metals in sediment at Tien estuary

Metal Site

S2 S3 S5 S6 S7 S1 S4

Cd -2.9 -2.9 -2.9 -2.8 -2.7 -2.0 -2.2

Ni -0.6 -0.6 -0.6 -0.6 -0.6 0 0

Cr -0.2 -0.3 -0.2 -0.3 -0.3 0 0

As 2.2 2.2 2.1 2.1 2.1 3.4 3.4

Pb -0.8 -0.8 -0.9 -0.9 -0.8 -0.3 -0.3

Cu -4.2 -4.3 -4.3 -4.3 -4.2 -3.9 -3.9

Zn -1.5 -1.5 -1.5 -1.5 -1.5 -0.8 -0.7

Fe -1.6 -1.6 -1.6 -1.6 -1.6 -1.1 -1.1

- Tien estuary sediment was uncontaminated with metals Cd,

Ni, Cr, Pb, Cu and Zn with negative Igeo values; but highly with As at


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S1, S4 sites (Igeo 3.4), and moderately contaminated at other sites

(Igeo 2.1 – 2.2).

- The EF values for As were 21.8 and 22.5 at S1, S4 sites, and

12.4 – 13.6 at other sites. This again confirmed high accumulation of

As in S1 and S4 sites, and moderate accumulation of the metal at

other sites. Ni and Cr were accumulated in the sediment at fairly low

level with the EF of 1.9 to 2.6; while Cd, Zn, Cu and Pb were non-

accumulated with low EF values in the range of 0.2 – 1.7.

Table 3.16. EF values for toxic metals in sediment at Tien estuary

Metal Site

S2 S3 S5 S6 S7 S1 S4

Cd 0.4 0.4 0.4 0.5 0.5 0.5 0.5

Ni 2.1 1.9 1.9 2.1 2.0 2.0 2.1

Cr 2.6 2.4 2.5 2.6 2.4 2.0 2.1

As 13.6 13.4 13.0 13.6 12.4 21.8 22.5

Pb 1.7 1.7 1.6 1.7 1.7 1.7 1.7

Cu 0.2 0.2 0.2 0.2 0.2 0.1 0.1

Zn 1.1 1.0 1.0 1.1 1.1 1.2 1.3

3.5.3. Toxic metal contents in M. lyrata

- The contents of toxic metals in the body tissue of M. lyrata

showed that, although there was a considerable fluctuation of metal

levels in M. lyrata with coefficient of variation (CV) of 6 to 22%,

they did not exceed the international limit values given by the

guidelines of CODEX STAN193–1995; EC–1881 and S.I. 268. This

confirms that the species are safe for human consumption.

- Accumulation of toxic metals in M. lyrata was different;

- The abundance of metals in M. lyrata varied in the ascending order

of Zn As Cu Cr Ni Cd Pb. Excluding Zn, this order was

different from that of metals in sediment: Zn Cr Ni As Pb

Cu Cd. This reveals that there is no correlation between the metals

levels in sediments and in the bivalves. This finding is in accordance

with the previous publication (Tu et al., 2010), in which researchers

pointed out that, metal accumulation in bivalves is related with levels

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Table 3.18. Toxic metal contents in the body tissue of M.lyrata (mg/kg dry weight)(*)

Metal

Parameter Cd Ni Cr As Pb Cu Zn

Min–max 1.3–1.9 1.5–2.8 1.8–3.4 11–16 0.3–0.6 6.9–8.7 95–128

Mean S (n 21) 1.7 ± 0.2 2.2 ± 0.3 2.7 ± 0.4 13 ± 1 0.4 ± 0.1 8.0 ± 0.5 113 ± 9

CV, % 12 14 15 8 21 6 8

Tu et al (2010) 1.66±0.28 - 0.92±0.2 4.6±0.5 0.20±0.04 6.16±0.99 113 ± 20

1. CODEX STAN 193-1995 a ≤ 22.2 - - - - - -

2. EC-1881 a ≤ 22.2 - - - ≤ 16.7 - -

3. S.I. 268 ≤ 5.0 ≤ 5.0 ≤ 6.0 ≤ 30 ≤ 7.5 ≤ 400 ≤ 4000

4. Regulation of Malaysia (1985) a

-

- - ≤ 11.1 ≤ 22.2 ≤ 11.1 -

5. Regulation of Thailand (1986) a - - - ≤ 22.2 ≤ 11.1 ≤ 222 ≤ 1111

6. Regulation of Korea (2009) a 22.2 - - - ≤ 22.2 - -

7. Regulation of Australia (2016) a ≤ 22.2 - - ≤ 11.1 ≤ 22.2 - -

(*) (-) means non-regulated;

(a) Metal concentrations regulated on a wet weight basis were converted to a dry weight basis by multiplying the regulated values by a conversion

factor of 11.11, assuming that the water content in bivalves is 90%.


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of metal in mobile and exchangeable forms. Clearly, besides total

metal, it is necessary to measure mobile and exchangeable forms of

toxic metals in sediment.

3.6. Metal speciation in sediment and bioaccumulation in

Meretrix lyrata in the Tien estuary

3.6.1. Toxic metal speciation in sediment

Ratio (%)

0%

20%

40%

60%

80%

100%

Cd Ni Cr As Pb Cu Zn

Metal

F1 F2 F3 F4 F5

Figure 3.13. Metal contents in the sediment fractions (%)

- The concentrations, distribution and order of the different

fractions of toxic metals revealed the following:

+ The residual fraction (F5) dominated the distribution of toxic

metals in the sediments, with mean metal percentages of Cd (43)Pb

(53)Zn (60)Ni (83)Cu (84)As (85)Cr (94%). Excluding Cd,

these metals are strongly bound in crystal structures, reflecting the

geophysical characteristics of the sediments in the study area;

+ Excluding Cd (12%) and Cu (5%), the Fe-Mn oxide-bound

fraction (F3) was the second most dominant fraction, with mean

metal percentages of Cr (5)As (11)Ni (16)Zn (34)Pb (35%).

The highly concentrated Fe and Mn species in these sediments

(2.1%–2.6% and 0.55%–0.74%, respectively) were strongly bound to

Pb, Zn, Ni and As through adsorption, flocculation and co-


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precipitation with Fe and Mn oxyhydroxides.

– The metal contents in the organic/sulfide-bound fraction

(F4) were low, with mean percentages of Cr (0.6)As (1.0)Zn

(2.1)Ni (2.9)Cd (3.3)Pb (6.5)Cu (9.2%).

– Excluding Cd, the metal contents in the exchangeable

fraction (F1) were higher than those in the carbonate-bound fraction

(F2). The highest proportion of Cd (37%) was detected in the acid-

soluble fraction (sum of the exchangeable and carbonate-bound

fractions) and was higher than those of the other metals. The mean

metal percentages in the acid-soluble fraction were Cr (0.4)Ni

(1.3)Cu (2.2)As (2.8)Zn (4.2)Pb (5.8%). This fraction consists

of contributions from anthropogenic sources such as industrial,

agricultural and urban activities. Due to the low level of these metals

in the acid-soluble fractions, the accumulation of these metals in

aquatic organisms in the study area may be insignificant.

- Two-factor ANOVA with replication was applied to the

results of the metal speciation in the sediments at all sampling

locations, yielding the following conclusions:

+ The metal concentrations in the acid-soluble fraction (sum of

the concentrations in F1 and F2) at all sites were significantly equal

(p 0.10; Fcalculated 1.4 F (0.10; 13; 252) 1.6), indicating that the

metal fraction originating from anthropogenic sources was the same

over the entire study area;

+ The summed metal concentrations in fractions F3, F4, and F5

at sites S1 and S4 were significantly higher than those at the other

sites (p 0.01; Fcalculated 66.8 F (0.01; 13; 196) 2.2). Sites S1 and S4

contained more sand (30%) than the other sites (15%), and the metals

were more strongly bound to crystal structures (sand and clay) than

to mud and silt in sediments at the study area.

3.6.2. Metal contents in M. lyrata, BSAF (bio-sediment

accumulation factor) and RAC (risk assessment code)

i) About BSAF

- The mean BSAFs of the metals in non-residual fractions for

M. lyrata were Cd>Cu>As>Zn>Cr>Ni>Pb. Excluding Pb, the

BSAFs of the metals in fractions F1 and F2 were much greater than 1


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(24–869 and 9–155, respectively), indicating that these metals

bioaccumulated in M. lyrata.

- Since the percentages of Cd in mobile form were highest

(37%), Cd had the greatest BSAF (55 in the non-residual fraction

consisting of F1 + F2 + F3 + F4), indicating that this metal easily

bioaccumulated.

- Because Cu2+

ions can form strong complexes with soluble

organics, as mentioned above, part of the Cu in fractions F3 and F4

could be converted into a mobile form, increasing the Cu

bioaccumulation in M. lyrata, with a BSAF of 10 in the non-residual

fraction.

- In addition, As and Zn had high bioaccumulation levels, with

BSAFs of much greater than 1. The percentages of the mobile As

and Zn forms (2.8 and 4.2%, respectively) were greater than those of

the other metals, excluding Cd and Pb, which explains the high

bioaccumulation levels of As and Zn, with BSAFs of 5 in the non-

residual fraction.

ii) About RAC:

The RACs show that:

– Cr, with an RAC of less than 1%, poses no risk.

– Ni, As, Pb, Cu and Zn, with RACs of 1 – 10%, pose low risk

– Cd, with an RAC of 37%, poses high risk because it has the

highest mobile fraction in the sediment and can therefore easily

bioaccumulate and enters the food chain.

3.6.3. Correlation between the metal contents in M. lyrata and

sediments

- Correlation analysis was performed between the metal

contents in the exchangeable, acid-soluble, and non-residual

fractions (x) and those in M. lyrata (y), the results shown that:

+ For Cd, Ni, Cu and Zn, strong linear correlations existed

between the metal concentration in M. lyrata (y) and that in the F1

fraction (x) (p < 0.01 and p < 0.05, respectively).

+ For Cd, Cr, Pb and Cu, strong linear correlations existed

between the metal concentration in M. lyrata and that in acid-soluble

fraction (x) (p < 0.001).


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+ For Cd and Cu, significant correlations were found between

the metal concentration in M. lyrata and that in the non-residual

fractions (x) (p < 0.05).

+ No correlations were found between the As content in M.

lyrata and that in the exchangeable, acid-soluble or non-residual

fractions (x).

Table 3.23. Correlations between the metal concentrations in M.

lyrata and the sediment fractions (*)

Metal Fraction Correlation equation

Pearson

correlation

coefficient

(R)

p-value

Cd

F1

F1 + F2

F1 + F2 + F3 + F4

y = 0.012x - 0.009

y = 0.029x - 0.026

y = 0.040x - 0.028

0.56*

0.69*

0.49*

0.0089

0.0005

0.0239

Ni

F1

F1 + F2

F1 + F2 + F3 + F4

y = 0.027x + 0.015

y = 0.003x + 0.315

y = 0.145x + 4.434

0.67*

0.03

0.16

0.0009

0.8992

0.4798

Cr

F1

F1 + F2

F1 + F2 + F3 + F4

y = 0.001x + 0.024

y = 0.038x + 0.083

y = 0.005x + 3.026

0.09

0.74*

0.01

0.7093

0.0001

0.9693

As

F1

F1 + F2

F1 + F2 + F3 + F4

y = 0.001x + 0.064

y = -0.016x + 0.649

y = -0.015x + 2.610

-0.02

-0.26

-0.09

0.9271

0.2646

0.6984

Pb

F1

F1 + F2

F1 + F2 + F3 + F4

y = -0.008x + 0.019

y = 0.840x + 0.494

y = -0.634x + 6.838

-0.12

0.66*

-0.19

0.6054

0.0013

0.4208

Cu

F1

F1 + F2

F1 + F2 + F3 + F4

y = 0.008x - 0.022

y = 0.022x - 0.069

y = 0.108x - 0.032

0.56*

0.78*

0.47*

0.0080

0.0001

0.0312

Zn

F1

F1 + F2

F1 + F2 + F3 + F4

y = 0.002x - 0.056

y = 0.013x + 1.101

y = 0.043x + 20.303

0.48*

0.41

0.25

0.0270

0.0607

0.2726

(*) These correlations were derived from the mean data of x and y found at 7

sampling sites in 3 sampling campaigns (n = 21); * Correlation is significant

These correlations clearly indicated that M. lyrata can be used

as biomonitor of Cd, Cr, Pb, and Cu contamination of the sediment


16

in the study area.

3.7. Copper and lead accumulation in M. lyrata cultured in water

environment in laboratory condition

3.7.1. Effect of metal levels and exposure time

- For testing the bioaccumulation of Cu and Pb in M. lyrata,

28-days culture was carried out at laboratory. The levels of metals

added to the containers were as followed: M1 - 30 µg/L Cu and 50

µg/L Pb (abbreviated to M1-30-50), M2-60-150, M3-100-300 and

M4-200-600, respectively. The result showed that:

- For metal concentrations (level M1, M2 and M3): the metal

concentrations in the bivalves (y) increased with the exposure time

(x) (R 0.97 – 0.99);

- For metal concentrations (level M4): after 14 days of the

exposure, the metals concentrations in the bivalves trended to

decrease, the first death occurred on the 22nd

day of exposure and all

organisms died on 28th day of exposure;

- Pb accumulated in the bivalves much more than Cu;

-The correlation coefficients between the metal concentrations

accumulated in the bivalves (y) and the metal concentrations added

to the containers (x) shown that:

+ For 7 days of exposure: there was linear correlation between y

and x (R 0.88 – 0.90);

+ For 14 days of exposure: there was strong linear correlation

between y and x with R 0.95 – 0.99 (p ≤ 0.05);

+ For 21 days of exposure: there was linear correlation between

y and x with R 0.75 – 0.87 (p ≥ 0.10);

+ For 28 days of exposure: there was strong linear correlation

between y and x with R 0.99 (p 0.05).

The increase of the metal concentrations in the bivalves together

with the increase of the metal concentrations added to the containers

and the exposure time allowed to confirm that M. lyrata could be

used as bio-indicator for the metal pollution in aquatic environment

at the study area

17

Table 3.25. Linear correlation between the metal contents in the M. lyrata and initial concentration of

dissolved metals, and exposure time (*)

Factor Cu Pb

Equation R P Equation R p

Correlation between

the metal content in

the M. lyrata and

exposure time

M1–30–50 y = 12x + 501 0.985 0.02 y = 89x – 484 0.967 0.03

M2–60–100 y = 16x + 632 0.999 0.01 y = 454x –

2430 0.976 0.02

M3–100–300 y = 41x + 271 0.990 0.01 y = 748x +

1365 0.990 0.01

M4–200–600(*)

– – – – – –

Correlation between

the metal content in

the M. lyrata and

initial level of

dissolved metals

7 days y = 2.9x + 485 0.880 0.12 y = 15x + 209 0.898 0.10

14 days y = 5.3x +

466 0.952 0.05 y = 50x – 3572 0.993 0.01

21 days y = 2.4x +

756 0.896 0.10

y = 23x +

3921 0.752 0.25

28 days (**) y = 8.9x +

578 0.999 0.03 y = 81x – 1772 0.999 0.01

(*)For these equations, initial concentrations of dissolved Cu and Pb (x) is 30, 60, 100 µg/L and 50, 100, 300, respectively, due to M.

lyrata reached steady-state after 21 days of exposure at level M4-200-600

(**)For these equations, initial levels is M1, M2 and M3, due to all M. lyrata died on 28th day of exposure at level M4

.


18

3.7.2. Rate of the metal accumulation Table 3.26. Rate of the metal accumulation by the M. lyrata (*)

No Initial levels

of metals

(µg/L)

Cu Pb

RMA

(µg/kg/day) Equation

RMA


1 M1–30–50 6 ± 5 y 0.41x

– 9.2

R 0.996

p 0.004

77 ± 7 y 3.4x –

139

R 0.997

p 0.002

2 M2–60–100 15 ± 3 371 ± 35

3 M3–100–300 28 ± 11 797 ± 80

4 M4–200–600 25 ± 9 623 ± 127

3.8. Bioaccumulation of copper and lead by bivalve Meretrix

lyrata cultured in water – sediment environment

3.8.1. Effect of metal levels and exposure time

Variation of the metal concentrations in the experiment container:

For copper (Cu): Although there was increase in Cu

concentrations added to the containers, the concentrations of

dissolved Cu in the water phase still was significantly equal for the

same metal-to-bivalve exposure time (p > 0.05; Fcalculated 2.9 F(0.05;

3,24) 3.0); The concentrations of dissolved Cu in the containers for

the different exposure time was significantly different (p 0.05;

Fcalculated 3.0 F(0.05; 5,24) 2.6); From the time adding the metal to

the container (day 0) to day 28, dissolved Cu concentrations

decreased about 91 – 99% (compared with Cu concentrations added

to the container).

For lead (Pb): The results in Table 2 show that, although

increased Pb concentrations added to containers, after one day of the

exposure, the concentrations of dissolved Pb in all the containers

were below 0.2 µg/L

Variation of the metal concentrations in the bivalves

- For exposure time: the metal concentrations in the bivalves

(y) increased with the exposure time (x) for all the levels of the

metals added to the containers. Results of linear correlation shown

that: there was strong correlation between y and x with R (Pearson

correlation coefficient) 0.78 - 0.98 (6/8 cases were of statistically


19

significance with p 0.05). Cu accumulated in the bivalves much

more than Pb

- For the metal concentrations added to the containers: the

correlation coefficients between the metal concentrations

accumulated in the bivalves (y) and the metal concentrations added

to the containers (x) shown that: there was strong linear correlation

between y and x (R 0.73 – 0.99), except the case for Pb after 7

exposure days (R 0.034); for Pb, only 4 of 8 cases were of

significance with p 0.05

It should be noted that because there was the strong linear

correlation between the metal concentrations in the bivalves and the

concentrations added to the containers, the metals accumulated in the

bivalves must be derived from both the metals in the water phase and

the sediment phase. Besides, the increase of the metal concentrations

in the bivalves together with the increase of the metal concentrations

added to the containers and the exposure time allowed confirming

that M. lyrata could be used as bio-indicator for the metal pollution

in aquatic environment at the study area.

3.8.1. Rate of the metal accumulation (RMA) in M. lyrata

Table 3.29. Rate of the metal accumulation (RMA) in M. lyrata

bivalves after 28 days of exposure (*)

No Initial levels of

metals (µg/L)

Cu Pb

RMA


RMA


1 30 – 50 5 2 y 0.089x

3.8

R 0.982

p 0.018

0.8 0.2 y

0.002x +

0.8

R 0.943

p 0.056

2 60 – 100 10 1 1.1 0.3

3 100 – 300 14 3 1.5 0.2

4 200 – 600 21 4 1.7 0.4

(*) For the RMA, the data in the table are mean ± standard deviation with n = 3 (3

containers replicated); y: RMA; x: the metal levels added to the container

20

Table 3.27. Linear correlation between the metal concentrations in the bivalves and the metal concentrations added to the

containers, and exposure time (*)

Factor Cu Pb

Equation R P Equation R

P

Correlation between the metal

concentrations in the bivalves

(y) and the concentrations

added in containers (x) for

exposure days

7 days y = 0.969x + 596(*)

0.999 0.01 y = 0.002x + 25.94 0.034 0.81

14 days y = 1.055x +

692(*) 0.994 0.07

y = 0.038x +

24.83 0.915 0.04

21 days y = 2.194x + 711 0.933 0.03 y = 0.035x +

43.46 0.731 0.14

28 days y = 2.381x + 719 0.955 0.02 y = 0.046x +

46.56 0.881 0.06

Correlation between the metal

concentrations in the bivalves

(y) and exposure time for the

metal levels added in the

containers

M1-30-50 y = 5.536x + 613 0.784 0.11 y = 1.160x + 12.20 0.894 0.05

M2-60-100 y = 10.91x + 594 0.963 0.02 y= 1.316x + 17.41 0.882 0.06

M3-100-300 y = 15.88x +

592.5 0.908 0.05

y = 1.893x +

15.23 0.953 0.02

M4-200-600 y = 24.59x +

525.1 0.930 0.03

y = 2.186x +

13.28 0.99 0.01

(*)For these equations, Cu concentrations added (x) = 30, 60 and 100 µg/L, because for x = 200 and above, y nearly reached to plain


21

The results showed that: i) Increase in the metal levels added to the

containers (or increase of the metal pollution) led to increars of the

RMA. The RMA for Cu in M. lyrata (after 28 days of exposure) was

greater 7 – 12 times than that of Pb for all the metal levels added to

the culture container, although Cu levels added were lower than the

Pb levels; ii) Between the RMA (y) and the metal concentrations

added to the containers (x), there was also strong linear correlation

with R 0.94 (p 0.05).

This once again proves that M. lyrata could be used as bio-

indicator for the Cu, Pb pollution in the aquatic environment of Tien

estuary.

CONCLUSION

On the basis of the results of this research, it can be concluded

that:

1) Preliminary analysis of toxic metals content (Cd, As, Pb,

Ni, Cr, Cu, Zn, Fe and Mn) in the water of Tien River and Tien

Estuary was conducted. The pollution of river with Fe led to an

increase in the Fe pollution of estuary.

2) The total metal concentrations in the sediment met the

requirements of the National Technical Regulation on

Saline/Brackish Water Sediment Quality (QCVN 43:2012/BTNMT).

The Igeo and EF factor indicated that sediment of Tien estuary was

polluted with As.

3) The speciation of seven toxic metals (Cd, As, Pb, Ni, Cr, Cu

and Zn) and risk assessment of them to environment and organism

were determined for the first time in the Tien estuary sediment.

4) The metal concentrations in the Meretrix lyrata met the

requirements of the regulations of Vietnam and several of

international organizations. There was no linear relationship between

the concentrations of toxic metals in the Meretrix lyrata tissues and

the sediments. There was linear correlation between the metal levels

accumulated in the Meretrix lyrata and the mobile metal levels in the

sediment.

5) The Cu and Pb levels accumulated in the calm Meretrix

lyrata through the experiment of exposure to increasing levels of the


22

metal in the estuary water and water-sediment were determined for

the first time. There were strong correlations between the metal

contents (Cu, Pb) in the clam and exposure times or the dissolved

metal concentrations; between RMA and metal contents in the

environment of experiment. The results obtained indicate that the

Meretrix lyrata can be used as bioindicator of the metal pollution in

the Tien estuary environment.


23

LIST OF PUBLICATIONS

1. Nguyen Van Hop, Hoang Thi Quynh Dieu, Nguyen Hai Phong

(2017). Metal speciation in sediment and bioaccumulation in

Meretrix lyrata in the Tien Estuary in Vietnam, Environmental

Monitoring and Assessment, 189(6), pp. 299. DOI: 10.1007/s10661-

017-5995-2. PubMed-ID: 28553695.

2. Hoang Thi Quynh Dieu, Nguyen Van Hop, Nguyen Hai Phong

(2017). Contents of the toxic metals in the sediment and their

bioaccumulation in Meretrix lyrata cultured in Tien estuary area,

Tien Giang Provine, Conference proceeding, The 5th Analytical

Vietnam Conference 2017, pp. 76 – 83.

3. Hoang Thi Quynh Dieu, Nguyen Van Hop, Nguyen Hai Phong

(2017). Bioaccumulation of copper and lead by bivalve Meretrix

lyrata cultured in water–sediment environment, Journal of Analytical

Sciences (Vietnam Analytical Sciences Society), 22(2), pp. 146 - 152

4. Hoàng Thị Quỳnh Diệu, Nguyễn Hải Phong, Nguyễn Văn Hợp

(2016). Nghiên cứu đánh giá chất lượng nước sông Tiền, Tạp chí

Phân tích Hóa Lý Sinh (Hội KHKT Phân tích Hóa, Lý& Sinh học

VN), 21(1), tr. 38 - 48.

5. Hoàng Thị Quỳnh Diệu, Nguyễn Văn Hợp, Nguyễn Hải Phong

(2017). Tích lũy sinh học đồng và chì bởi nghêu (Meretrix lyrata):

Nghiên cứu trường hợp đối với nghêu lấy từ vùng nuôi ở cửa sông

Tiền, tỉnh Tiền Giang, Tạp chí Khoa học - Khoa học Tự nhiên, Đại

học Huế, 126(1A), tr. 31 – 40.

6. Hoàng Thị Quỳnh Diệu, Nguyễn Văn Hợp, Lê Thị Ngọc

Thảo, Nguyễn Hải Phong (2017). Nghiên cứu đánh giá chất lượng

nước vùng cửa sông Tiền, tỉnh Tiền Giang, Tạp chí Khoa học và

Công nghệ, Chuyên san Khoa học Tự nhiên, Kỹ thuật và Công nghệ,

Trường Đại học Khoa học, Đại học Huế, 8(1), tr. 87 – 100.

http://csdlkhoahoc.hueuni.edu.vn/index.php/nhakhoahoc/chitiet/131


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