Rate of the metal accumulation (RMA) in M.. The results showed that: i) Increase in the metal levels added to the containers (or increase of the metal pollution) led to increars of[r]
Trang 1-
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
Trang 2COLLEGE OF SCIENCES
-
HOANG THI QUYNH DIEU
ANALYSIS AND ASSESSMENT THE BIOACCUMULATION OF COPPER AND LEAD
BY BIVALVE (Meretrix lyrata) CULTURED IN
1 Assoc Prof Dr NGUYEN VAN HOP
2 Dr NGUYEN HAI PHONG
Trang 3INTRODUCTION
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
Trang 4The 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
Trang 5sediment 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
Trang 6widths) 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
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
Trang 7Figure 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
Trang 8Table 3.1 Instrumental settings for the ICP-MS instrument
3.2 Quality Control Analysis
3.2.1 Isotope selection and calibration range
Table 3.2 The equation of the calibration curve
3.2.2 Limit of detection, limit of quantification
Table 3.3 Limit of detection, limit of quantification of ICP-MS
Trang 9No Element LOD (µg/L) LOQ (µg/L)
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)
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
Trang 10- 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
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
Trang 11terrace) 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)
3.5.2 Toxic metal accumulation in sediment
Table 3.15 Igeo values for toxic metals in sediment at Tien estuary
- Tien estuary sediment was uncontaminated with metals Cd,
Ni, Cr, Pb, Cu and Zn with negative Igeo values; but highly with As at
Trang 12S1, 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
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
Trang 13Table 3.18 Toxic metal contents in the body tissue of M.lyrata (mg/kg dry weight)(*)
Trang 14of 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
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