The sedimentary processes on tidal flats in the north of vietnam initial results and implication future proceedings of VAST

bqn 11 isolated from petroleum-polluted water samples in Quang Ninh coastal zone, Vietnam Pham Hai An, Le Due Cuong, Nguyen Minh Hai Application of a 3d numerical model for simulation of

VIETNAM ACADEMY

OF SCIENCE AND TECHNOLOGY

(VAST)

POUR LE DEVELOPPEMENT

(IRD)xwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA

Institut de recherche pour Ie d'veloppement

ISBN: 978-604-913-162-2

_29th

N H A X U A T B A N K H O A H Q C T V N H IE N V A C O N G N G H I;

9 Hubert Loisel, Vincent Vantrepotte, Dinh Ngoc Dat, Sylvain Quillon, 96

Analysis of the suspended particulate matter concentration variability of the

coastal waters under the Mekong's influence from remote sensing

Levels of heavy metals in muscles with relation to the growth

of two marine fish speciesxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA

Nguyen Thanh Hien, Ulrich Saint-Paul

Macrobenthic communities in estuarine mangrove ecosystems subject to

aquaculture activities

Degradation of naphthalene by biofilm forming rhodococcus sp bqn 11 isolated

from petroleum-polluted water samples in Quang Ninh coastal zone, Vietnam

Pham Hai An, Le Due Cuong, Nguyen Minh Hai

Application of a 3d numerical model for simulation of suspended sediment

transport in Bach Dang - Cam estuary (Vietnam)

Water quality in Cam - Bach Dang estuary area

Dinh Van Nhan, Pham The Thu, Do Manh Hao

Spatio-temporal variability of phytoplankton in Halong bay: a preliminary result

Nguyen Mai Luu, Nguyen Dinh Khang, Phan Son Hai, Nguyen Manh Ha,

Pham Tien Due, Lai Thi Bich Thuy

The sedimentary processes on tidal flats in the north of Vietnam: initial results

and implication future

A preliminary study on variability oftintinnid (order tintinnida) in Halong bay

Biological and physical aggregation/disaggregation process in mixing jar

Ph an Van Kiem, Chau Van Minh

Studies on marine sponge biodiversity in Vietnam: patterns and outlooks

Molecular marker: an alternative strategy to study biodiversity of soft coralsdcbaZYXWVUTSRQPONMLKJIHGFEDCBA

(c n id a r ia : o c to c o r a llia )

164 BAo cAo KHOA HOC HOI THAo VAST - IRD V~ KHOA HOC BI~NxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA

NORTH OF VIETNAM: INITIAL RESULTS AND IMPLICATION

FUTURE

<Dang Hoai Nhont, Tran Due Thanh), Dinh Van Huyl

1 In s titu te o f M a r in e dcbaZYXWVUTSRQPONMLKJIHGFEDCBA E n v ir o n m e n t a n d R e s o u r c e s , V ie tn a m A c a d e m y o f S c ie n c e a n d T e c h n o lo g y

(V A S T )

2 N u c le a r R e s e a r c h In s titu te , D a L a t

3 F a c u lty o f C h e m is tr y , H a n o i U n iv e r s ity o f S c ie n c e s

" C e n tr e fo r G e o lo g ic a l A n a ly s is L a b o r a to r y , H a N o i

1 SUMMARY

Tidal flats in North Vietnam extending from Mong Cai (Quang Ninh province) to

Kim Son (Ninh Binh province) are affected by human activities and land - ocean

interaction processes It can be shown in erosion, accretion, accumulation of pollutants

with time For understanding sedimentary processes on tidal flats, samples from 11

collected sediment cores were in analysis of 210Pb, 226Ra, grain size, metals and

minerals The sediment parameters on tidal flats are divided in three sedimentary

environment types, including Deltaic tidal flat sedimentary environment from southwest

Do Son Peninsula to Kim Son and dominated by accretion processes, estuarine tidal flat

sedimentary environment from northeast of Do Son Peninsula to southwest of Cat Ba

Islands, and embayment tidal flat sedimentary environment from Cat Ba Islands to

Mong Cai and characterised with slow accretion and small rate of sedimentation

K e y w o r d s : tid a l fla t, s e d im e n ta r y p r o c e s s , N o r th V ie tn a m , 2 1 O p b , h e a v y m e ta ls

2 INTRODUCTION

Tidal flat which is a kind of coastal wetlands plays an important role for human

life by providing space for socio-economic development and being in high biodiversity

[20] Because the tidal sediments record many of information on the impacts from

nature and human activities, it is a key factor to understand sedimentary processes

Tracking environmental changes using many indicators of biology and geochemistry

[12] can help us to get information on environment conditions in the past and at present

The coastal provinces of North Vietnam extend from Quang Ninh to Ninh Binh

where the rivers discharge to sea through their mouths of Ka Long, Tien Yen, Ba Che,

Troi, Bach Dang, Carn, Lach Tray, Van Uc, Thai Binh, Ba Lat, Ninh Co and Day

(Fig 1) The channels which bring water from mainland to sea are changing coastal

PROCEEDINGS OF VAST - IRD SYMPOSIUM ON MARINE SCIENCE 165xwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA

environment conditions The coastal environments record human impacts, nature events

in sediments, but they are reflected changing with time

As part of the coastal region of North Vietnam, intertidal zones interest many

scientists, indicating with the number of articles on environmental sediment These

studies can help us understand environmental conditions as sedimentation and erosion

rates [11, 15, 19,21], geological structure of tidal flats in Holocene [7, 18], sediment

compositions [9, 16] and sediment geochemistry [1, 2, 6, 14, 19] These publications

have shown that nature and human activities are influenced on the tidal environment

Our research questions are in the past and at present what the human and the

nature have affected on the tidal environment By analysis of sediment cores in the tidal

flats m gram size,. 210Pb ,226R a, meta s anI d mimmera s, se irnentary processes on1 di tiid 1a flats

will be clearer understood

During 2009 - 2012, three campaigns were carried out to collect samples of sediment

cores Me 6 (0-40cm) and Me 5 (0-63cm) in April 2009, Me 8 (0-40cm) and Me

11(0-50cm) in October 2010, and Me 190cm), Me 2 70cm), Me 3 70cm), Me 4

(0-90cm), Me 7 (0-(0-90cm), Me 9 (0-90cm) and Me 10 (0-90cm) in March 2012 (Fig.1)

21'

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3 2 Methods

We had cut 2.0 em per samples from the top to the end of cores, and kept them at

4°C in field before storing in laboratory In the laboratory, all sediments are dried in

air-condition at 16°C

Grain sizes of sediment were analyzed by sieves for coarse grain (> 0.063mm) and

particle size analyzers CILAS 990 for fine grain « 0.063mm) after removing salts and

organic matters by distilled water and hydrogen peroxide (10% H202) Sediment

classification is according to Lisitzin [13]

The 2lOPb analysis in sediments was calculated indirectly by 2lOpO in sediments,

the sediments were extracted by HN03 and HF concentrated Then we used 0.1 %

diethylammonium diethyldithiocarbamate and chloroform in 5M HCI to absorb 210pO

by silver dish and measured on alpha s£ectrometry We used 209pO as initial standard

assess recovery of extraction [8] The 22 Ra in sediments as background were measured

directly by gamma spectrometry The constant rate supply (CRS) model is used to

Krishnaswami [10], later have been modified [3, 4, 17] Nowadays, this CRS model is

used very common in calculating sedimentation rate in coastal and estuaries

(1) Where t: year;

A constant = 0.031;

A(O) is total of 210Pbexcessin sediment core elOPbcxccss=210Pbactivity- 226Ra);

A(x) is 210Pbexcessin sediment core at depth x

For metals analysis: Weighed 0.5g dry sediments, then were extracted by 10 ml

8N HN03 and 3ml 30% H202 under reflux column at 95°C in 15 minutes After that

samples were cooled and added about 5ml 16N HN03, then kept at 95°C in 2 hours

(Method 3050b), cooled and filtered by 0.45 urn papers (Whatman) Finally, samples

Elmer) All chemicals are in grade analysis For control Q A lQ C of analysis processes,

the certified reference material samples (PACS2, MESS-3) were used

Minerals in sediments were analyzed by two methods, which were analysis by

thermo gravimetric on STA-PT 1600 instrument for clay minerals with relative error ±

5%; other minerals were analysis by X-ray diffraction analysis on D8-Advance Bruker

instrument with in ±3% relative error

4 RESULTS AND DISCUSSION

4.1 Distribution of grain s iz e in tidal flats

From Mong Cai to Kim Son, sediments on tidal flats were composed of coarse

sand (Md = 0.50-1.00mm), medium sand (Md = 0.25 0.50mm), fine sand (Md = 0.10

-0.25mm), coarse aleurites (Md = 0.05 - 0.10mm), fine-aleurites muds (Md =

0.01-PROCEEDINGS OF VAST - IRD SYMPOSIUM ON MARINE SCIENCExwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA

0.05mm) and alerutic-pelitic muds (Md < 0.05mm) Coarse, medium and fine sands

were only in the north of the study area (MC 1, MC 3) and most of them were medium

and well in sorting Fine-grain sediments dominated the south of the area and most of

them were poor to medium in sorting

In Fig 2, the diameters of sediments in the cores changed in depths, reflecting the

change of sedimentary environmental conditions with time Based on the diameters,

sediments can be divided into two sedimentary processes of erosion and accretion on the

tidal flats Erosion processes are seen at MC II in depth of 27-50 em At MC 10 erosion

and accretion were alternative from 22 to 90 cm, at MC 8 in depth of 33 - 40 em, at MC

3 in depth of 20 - 66 em and on MC I at 15 - 90 cm, where the diameters were from

coarse aleurites to coarse sands Accretion processes are seen in all cores, at MC 11 in

depth of 0-27 cm, at MC 10 from 0-22 em, at MC 8 in depth ofO-27cm, at MC 7, MC 5

and MC 4 in all of dep,th in cores, on MC I and MC 3 in depth of 0-20cm

Based on mean diameters (Md) of sediments, three areas were divided, including

Deltaic tidal flat sedimentary environment (MC 11, MC 10, MC 9, MC 8, MC 7) with

most sediments of coarse aleurites to fine-aleurites muds; Estuarine tidal flat

Embayment tidal flat sedimentary environment dominated by fine to coarse sands (MC

1,MC 3)

MC1 0.052 0.725 0.224 0.119 1.297 6.381 2.280 1.497

MC3 0.080 0.181 0.130 0.021 1.531 4.047 1.887 0.654

MC4 0.008 0.057 0.024 0.015 2.284 3.988 3.262 0.380

MC5 0.008 0.034 0.015 0.007 1.601 2.986 2.686 0.324

MC7 0.022 0.063 0.048 0.012 1.740 3.557 2.991 0.408

MC8 0.019 0.116 0.040 0.029 1.803 3.060 2.565 0.255

MC9 0.054 0.102 0.065 0.008 1.255 3.635 2.119 0.810

MC10 0.051 0.084 0.066 0.007 1.233 3.588 2.108 0.848

MC 11 0.037 0.068 0.057 0.008 1.366 2.696 2.151 0.410

Min = minimum; Max = maximum; Aver = average; SD = Standard deviation

167

168xwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBABAo cAo KHOA HOC HOI THAo VAST - IRD V~ KHOA HOC BI~N

Me.

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MC8 /NMLKJIHGFEDCBA '\lT i' ' ,

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4 2 D is tr ib u tio n O f2 1 O P b a n d 226R a a n d s e d im e n ta tio n r a te o n tid a l fla ts

The 210Pb and 226Ra in sediments can help us tracking change of environments;

they are indicators for erosion or accretion processes When the content of 226Ra in

sediment layer is higher than that of 210Pb, there is no deposition of sediment On the

other hand, if the content of 210Pb in sediment is higher than that of 226Ra, it will show

the deposition of sediment On the tidal flats of North Vietnam, there are consisted of

two above cases

In the sediment cores Me 2, Me 4, Me 5, Me 6, Me 7 on the tidal flats, the

content of 210Pbactivityis higher than that of 226Rain a111ayers, indicating the accretion in

these areas for the whole time (Fig 3) In the sediment cores Me 3, Me 8, Me 9, Me

10,Me 11 in the tidal flats, there are in these sediment cores two phases, including the

first phase with content of 210Pbactivityin sediment higher than that of 226Raand the later

second phase with content of 226Rain sediment higher than that of 210Pbactivity(Fig 3)

PROCEEDINGS OF VAST - IRD SYMPOSIUM ON MARINE SCIENCE 169xwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA

,

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l"Pb_ and 22IRa(BqIkg)

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Fig 3 Distribution of 210 Pb and 226 Ra in sediments on tidal flats

Sedimentation rates on tidal flats were timely changed in different areas They

were low inMe 3 and Me 10 (Fig 4), high in Me 2, Me 4, Me 5, Me7, Me 9, Me II

(Table 2 and Fig 4) On tidal flats, there were not only accretions, but also erosion that

was indicated at Me II, MetO, Me 9, and Me 8 The sedimentation rate is closely

related to the diameter of sediment The high sedimentation rate, the much more fine

Men

~-

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sediment is In three sedimentary environments mentioned above, high sedimentation rate was recorded in estuarine tidal flat sedimentary environment and deltaic tidal flat sedimentary environment

Max 1.31 0.34 2.35 15.00 1.18 14.42 3.24 15.83 0.64 14.84

SD 0.37 0.11 0.65 4.01 0.31 3.105 0.83 5.27 0.15 4.15

In Table 2, at MC 5, MC 7, MC 9 and M CII standard deviation of sedimentation rates are high, because in these cores sedimentation rates are change very fast and suddenly (Fig 4), they show that effect from sedimentary environment, we are also seeing same trend changes by concentration of metals and clay minerals and quartz in these sediment cores

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PROCEEDINGS OF VAST - IRD SYMPOSIUM ON MARINE SCIENCExwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA

Me 11

4 3 D is tr ib u tio n o f m e ta ls o n tid a l fla ts

Heavy metals in sediment cores were analyzed including Cu, Pb, Zn, As, Ni, Cr

High concentrations of elements are As, Cu, Pb and Zn in MC 5, MC 6, MNMLKJIHGFEDCBA C 7 , MC 8

and MC 10 In comparison with MC 1, MC 2 and MC 3 in the north of the study area,

the concentrations of metals in the south of the study area is higher Metals in sediment

cores increased in recent years, clearly in MC 5, MC 8 and MC 2 (Table 3)

Copper (Cu) in sediments were in the range from low to high concentration, the

highest concentration at MC 5 and MC 6 Most of them are higher than ISQG levels of

Canadian standard The lower concentration compared with ISQG is in MC 1 MC 2 and

MC 3 (Table 3)

The concentration of lead (Pb) in sediment had a trend similar to the one of Cu It

was high in sediment cores MC 5, MC 6, MC 7, MC 8 and MC 10, only at MC 1, MC 2

and MC 3 but lower than ISQG level The highest concentration was at MC 7

M C 1 M C 2 M C 3 M C 5 M C 6 M C 7 M C 8 M C 1 0 M C 1 1

M e t a l L e v e l s

( n = 8 ) ( n = 2 0 ) ( n = 2 1 ) ( n = 2 4 ) ( n = 1 9 ) ( n = 2 3 ) ( n = 1 7 ) ( n = 4 ) ( n = 1 8 )

Min 2.17 10.06 0.69 47.66 53.25 60.31 19.93 33.68 11.42

Max 7.37 18.84 12.14 70.88 89.01 94.76 85.59 74.55 36.12

Cu A v e r 5.12 1 4 8 0 3.85 57.58 8 0 0 5 72.93 5 6 0 3 5 0 4 1 23.72

Min 5.78 18.37 5.99 59.61 55.36 70.96 22.32 60.59 12.67

Max 26.06 31.12 22.99 90.20 82.25 120.32 96.28 103.01 111.63

Pb A v e r 19.59 23.71 12.69 76.16 72.25 95.02 61.27 79.41 28.61

Max 45.66 492.01 62.64 137.68 132.99 143.68 151.79 152.08 152.16

A v e r 30.69 81.62 35.89 111.66 123.05 98.89 1 0 6 2 2 113.80 65.97

SO 14.39 111.89 11.37 18.26 8.72 17.71 27.20 30.93 29.88

171