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

VIETNAM ACADEMY OF SCIENCE AND TECHNOLOGY (VAST) ~ Institut de recherche pour Ie d'veloppement INSTITUT DE RECHERCHE POUR LE DEVELOPPEMENT (IRD)xwvutsrqponmlkjih ISBN: 978-604-913-162-2 BAo cso KHOA HOC ~ ,,? HOI THAO VAST - IRD VE KHOA HOC BIEN • •QPONMLKJIHGFEDCBA ,,? P R O C E E D IN G S O F V A S T - IR D S Y M P O S IU M O N M A R IN E S C IE N C E H a ip h o n g - V ie tn a m , N o v e m b e r " _, ? _ 28th_29th, "A _ 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; PROCEEDINGS OF VAST -IRD SYMPOSIUM ON MARINE SCIENCE Hubert Loisel, Vincent Vantrepotte, Dinh Ngoc Dat, Sylvain Quillon, Jean-Pierre Lefebvre, Xavier Meriaux, Ph am Minh Thu, Antoine Mangin 96 Analysis of the suspended particulate matter concentration variability of the coastal waters under the Mekong's influence from remote sensing 10 Le Quang Dung, Nguyen Viet Linh, Nguyen Due Cu, Vu Van Tu 108 Levels of heavy metals in muscles with relation to the growth of two marine fish speciesxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA II 117 Judith C Klein, Nguyen Vu Thanh, Nguyen Dinh Tu, Nguyen Thanh Hien, Ulrich Saint-Paul Macrobenthic communities in estuarine mangrove ecosystems subject to aquaculture activities 12 Cung Thi Ngoc Mai, Le Thi Nhi Cong, Nghiem Ngoc Minh 125 Degradation of naphthalene by biofilm forming rhodococcus sp bqn 11 isolated from petroleum-polluted water samples in Quang Ninh coastal zone, Vietnam 13 Vu Duy Vinh, Sylvain Quillon, Jean-Pierre Lefebvre, Pham Hai An, Le Due Cuong, Nguyen Minh Hai Tran Anh Tu, 134 Application of a 3d numerical model for simulation of suspended sediment transport in Bach Dang - Cam estuary (Vietnam) 14 Cao Thi Thu Trang, Ph am Thi Kha, Jean Pascal Torreton Duong Thanh Nghi, Vu Thi Luu 145 Water quality in Cam - Bach Dang estuary area 15 Chu Van Thuoc, Nguyen Thi Minh Huyen, Duong Thanh Nghi, Vu Thi Luu, Dinh Van Nhan, Pham The Thu, Do Manh Hao 152 Spatio-temporal variability of phytoplankton in Halong bay: a preliminary result 16 Dang Hoai Nhon, Tran Due Thanh, Dinh Van Huy, Nguyen Thi Kim Anh, Nguyen Mai Luu, Nguyen Dinh Khang, Phan Son Hai, Nguyen Manh Ha, Pham Tien Due, Lai Thi Bich Thuy 164 The sedimentary processes on tidal flats in the north of Vietnam: initial results and implication future 17 Dinh Van Nhan, Chu Van Thuoc, Nguyen Xu an Quynh A preliminary study on variability oftintinnid 179 (order tintinnida) in Halong bay 186 18 Do Thi Phuong Thao Biological and physical aggregation/disaggregation process in mixing jar 19 Tran My Linh, Ninh Khac Ban, Dam Due Tien, Vu Huong Giang, Le Quynh Lien, Ph an Van Kiem, Chau Van Minh 195 Studies on marine sponge biodiversity in Vietnam: patterns and outlooks 20 Le Quynh Lien, Tran My Linh, Ninh Khac Ban, Chau Van Minh, Tatyana Dautova 202 Molecular marker: an alternative strategy to study biodiversity of soft coralsdcbaZYXWVUTSRQ (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~Nxwvutsr THE SEDIMENTARY PROCESSES ON TIDAL FLATS IN THE NORTH OF VIETNAM: INITIAL RESULTS AND IMPLICATION FUTURE 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% H 202) 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 calculate chronology of sediment layers (1) This model was suggested by 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 210Pbexcess in sediment core elOPbcxccss=210Pbactivity - 226Ra); A(x) is 210Pbexcess in sediment core at depth x For metals analysis: Weighed 0.5g dry sediments, then were extracted by 10 ml 8N HN03 and 3ml 30% H 202 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 hours (Method 3050b), cooled and filtered by 0.45 urn papers (Whatman) Finally, samples were diluted to 100 ml and measured by using ICP-MS method (Elan 9000 Perkin 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 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 ON MARINE SCIENCExwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIH 167 OF VAST - IRD SYMPOSIUM 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 in depth of 33 - 40 em, at MC 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 in depth ofO-27cm, at MC 7, MC and MC in all of dep,th in cores, on MC I and MC 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 sedimentary environment dominated by fine-aleurites muds (MC 4, MC 5); and Embayment tidal flat sedimentary environment dominated by fine to coarse sands (MC 1, MC 3) Table Sediment parameters on the tidal flats SoNMLKJIHGFEDCBA M d (mm) CoresQPONMLKJIHGFEDCBA SO M in dcbaZYXWVUTSRQPONMLKJIHGFEDCBA M ax A v e r SO M in M ax A v e r 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 BAo cAo KHOA HOC HOI THAo VAST - IRD V~ 168xwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Sediment QPONMLKJIHGFEDCBA SJ pw am e •••.• (Md, KHOA HOC BI~N J M II'W 'I8 e r1 (Md, Sedment Sol ., Me Sediment paramelera (Md, Sediment parameters so> {Md SJ lAd("",,) -.- S Sedimentary MC8 _ parameters / (Md, so> NMLKJIHGFEDCBA '\lT i' ' , ",(mm) ~s -., ,,/ / Sediment paramelltf$ (Md, so> Sediment Fig Distribution D is tr ib u tio n O f2 O Pb and parameter (Md, so> Sediment parame\efl (Md SJ of sediment parameters on tidal flatsdcbaZYXWVUTSRQPONML 226 R 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 210Pbin 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 on the tidal flats, the content of 210Pbactivity is 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 210Pbactivity in 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 , , J"Pb_ , '1 , , and lltIRa (8qlkg) , 11OPb_ , , " "" J · I~j ,t •· ; , -+-"'"PD_ ~~ f , toe " '~ c: Me2 , , and mRa (SqIIotg) '" " · dcbaZYXWVUTSRQPONMLKJIHGFEDCBA rr> " 169xwvutsrqponmlk ON MARINE SCIENCE ,, '" ,, "I Me3 1:1NMLKJIHGFEDCBA f 'I •• 1:1 -+- 210 .• 22&Ra PblldMly J~_.nd~(8q/IIgl " I " ) '> " '" '" Me4 _210PII~ ".22eRlt !" I t • ~"" 210P!:l_ , :1 :1 / t " and mRa (8q/tg) '~== :j ~" 'I •• " "ss ""J , :1 " "1 ~- , , and Z2tRa(Bqlkgl roc " r- ~ , '" < { K"i " o as _"'Pb-, 2· 'Pb , , M'-' X I '" , t MC6 :, " " " '" '" Me, c '>OPb_ ~~ J"'AI_ and -Ra (8qI\g) , -'~~~ ~ •• !" ' , :1 ", 710 Pb , 't' 1i and mRa (Bqlkg) " '", 'I" ,, :h0P!)_ • , , " " ,, and 21IIRa " '" '" Me -v- :1 j) '''Re I" j" " t •• ,, '''Pb_and~' " b "j " " • ''''PtJ -, , " ~g) ,., " Me 10 MC9 ~ 210~ I j - •••- 226R• !" P -""""~ • l"Pb_ and 22IRa(BqIkg) o 01 _ _ ••• _ _ _ I I _ _ _ Men ~- K" '''Pb_ t" 'I " as ,,' Fig Distribution of 210Pb and 226Ra in sediments on tidal flats Sedimentation rates on tidal flats were timely changed in different areas They were low in Me and Me 10 (Fig 4), high in Me 2, Me 4, Me 5, Me7, Me 9, Me II (Table 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 The sedimentation rate is closely related to the diameter of sediment The high sedimentation rate, the much more fine BAo cAo KHOA HOC HOI THAo VAST 170xwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA - IRD V~ KHOA HOC BI~N 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 Table Sedimentation rates (em/year) on tidal flatsNMLKJIHGFEDCBA M C2 M C3 M C4 Max 0.11 1.31 0.04 0.34 0.19 2.35 A v e r 4 SD 0.37 0.11 0.65 Min Min = minimum; M C5 0.13 15.00 2.94 4.01 = Max M C7 M C6 0.26 M C8 0.17 14.42 1.18 M C9 0.07 3.24 MC MC 11 10 0.06 15.83 0.14 0.09 14.84 0.64 7 4 1.71 0.31 3.105 0.83 5.27 0.15 4.15 = average; maximum; Aver SD = Standard deviation In Table 2, at MC 5, MC 7, MC and M C II 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 Sedimentalioo rate (anlyear) Sedimentation rates (cmlyear) "" "'" "",,, • "" , ., '9111 MC "51 MC3 "" -""" ~ '"3 , " :""::: """ ,, , " " 117 , > , 1'13 • , "" ,." Sedimentation 1911 '1173 , '''' "" rate (cmfyear) •••~~-> ~-> -+ -> -+ -< Me5 !! e " •• 19845 1981 " , , "" 1'70 "" "" "" • , 1.71 "" "" 1'15 , 1912 '&71 rate " = •••• > 55 "" " "" Sedimentation (cnVyear) rate (cm'yeat) ~H'~~~-~"",;,,-+-~-> ~ ., "" "" MC I :~ l G "" ," " '''' f g dcbaZYXWVUTSRQPONMLKJIHGFEDCBA '.1 199& '995 '970 Sedimenlalion "" "'"::: , , :: ""t====~=====:;:;;;-::: Mea Me7 · >- rate (anlyear) (emlyear) ~r -;=====~======- ., " Sedimentation rates "" """ MC6 1911 "" Sedimentation "" r-""t"""-> ~ ~-> -+ -< 19711 1111' ,"- , (cm'year) 11191 : >- 1'71 "", K'IM Sedimentation rate ""~~-> -+ -> -+ ~> -+ -< "'" "",." "" , ", r~:::;~~~=====-"" ~ ,, ,, """" " "" , "" MC · rt i~ !" , ; I "•• ~ rate ::~r -j.-+- ; -+ + +-~ < e ,", S Sedimentalion "" ~~-+ +-+ + + + -< "" "" "" ""'''' >- (cmtyear) ,,,,t-"r -> ~-> -+ -':'-~ -< "79 Hil" !:! l5 · ~ S" :: "" "" " MC10 PROCEEDINGS OF VAST - IRD SYMPOSIUM Sedm.ntalion rate ON MARINE SCIENCExwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHG 171 (O'I'IIyNr) Me 11 rates on tidal flatsdcbaZYXWVUTSRQPONMLKJIHGFEDCB Fig Sedimentation 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, M NMLKJIHGFEDCBA C , MC and MC 10 In comparison with MC 1, MC and MC 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 and MC (Table 3) Copper (Cu) in sediments were in the range from low to high concentration, the highest concentration at MC and MC Most of them are higher than ISQG levels of Canadian standard The lower concentration compared with ISQG is in MC MC and MC (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 and MC 10, only at MC 1, MC and MC but lower than ISQG level The highest concentration was at MC Table Value of metals (mg/kg) in core sediments on tidal flats M C1 M e ta l (n = Cu M C2 M C3 M C5 8) (n = ) (n = ) (n = 24) M C7 (n = 23) M C8 M C10 (n = ) (n = ) M C 11 (n = Min 2.17 10.06 0.69 47.66 53.25 60.31 19.93 33.68 11.42 7.37 18.84 12.14 70.88 89.01 94.76 85.59 74.55 36.12 A v e r 5.12 3.85 57.58 0 72.93 23.72 SO 1.83 2.20 2.80 8.03 8.46 7.78 21.51 17.54 6.77 ) 18.70 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 A v e r 19.59 23.71 12.69 76.16 72.25 95.02 61.27 79.41 28.61 SO 6.98 2.93 4.00 6.88 8.72 12.24 22.48 18.76 21.43 Min 3.95 13.26 19.63 87.46 94.25 72.21 62.19 88.60 26.67 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 2 113.80 65.97 SO 14.39 111.89 11.37 18.26 8.72 17.71 27.20 30.93 29.88 30.20 ISOG Zn (n = ) Max ISOG Pb M C6 L e v e ls BAo cAo KHOA HOC HOI THAo VAST 172xwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA - IRO V~ KHOA HOC BIf:N 124.00 ISQG Min 0.61 3.15 0.26 23.43 20.24 25.78 7.13 13.27 376 Max 6.69 9.69 8.41 53.93 42.94 38.62 42.16 30.81 12.09 AsNMLKJIHGFEDCBA 27.53 A v e r 4.22 dcbaZYXWVUTSRQPONMLKJIHGFEDCBA 38.29 26.68 21.66 7.31 11.38 7.96 2.22 2.18 SO 2.21 2.18 5.27 12.86 Ni Min 10.88 9.93 2.60 30.96 23.16 34.66 8.74 34.88 2.05 Max 23.86 41.44 24.97 44.80 36.83 74.11 63.67 55.97 323.32 A v e r 16.38 18.12 31.92 44.18 32.41 44.49 45.89 4.18 8.43 6.62 4.34 3.85 9.82 12.01 8.75 83.66 SO - ISQG Cr 4.00 7.20 ISQG Min 5.35 17.07 5.98 34.40 28.71 32.35 12.70 30.67 8.86 Max 22.17 54.46 17.65 49.80 47.83 53.33 50.83 44.40 22.71 A v e r 16.44 24.11 11.47 41.98 41.41 33.19 36.55 15.78 ISQG 5.74 8.30 2.75 5.11 4.39 5.00 12.75 5.79 3.53 52.30 TEL Min = minimum; Max = maximum; Aver = average; SD = Standard deviation; n= number of sample Zinc (Zn) has high concentration in sediment Although average concentration of Zn was lower than were higher than ISQG level At some positions on recently (Me 8, Me 11, Me and Me 2) increased Me and Me (Fig 5, Table 3) Concentration of metals (mgIkg dry weight) Concentration of metals eo 80 (mgfkg in Me 5, Me and Me 10 ISQG level, some layers in cores the tidal flats, the concentration The lowest concentration was in dry weight) JOe) of Concentration 500 ~r.~ ~7/,'~' ' 0102030 40 50 60 metals 7011090 (mglkg dry weigl!) 100110120130140150160 o~~~~~~~~~~~ MC3 " MC1 ~"" ••.• Pb MC2 • - In Concentration of metals (mglkg city weight) Concenltalion of metals (mglkg dry weighl) Concentration of metals (mglkg dry weight) PROCEEDINGS Concentration o ~u ~c" •.• Concentration dry weight) (mglkg o I 40 of metals 60 " '" :::.: 20 • • Concentration ''''' -" I~ ,_ "', ••••• e- "w dl)' weignt) • , f Content 01 minerals (%) ~v 0,,,0 °_ " j 1" of minerals ~ Mea' -" « f i " , -- CIort ~ f) ~.: (%) ~_ ,I (' ~" I;c-""- ~'" ~~~~~:~ L o~., t,·",,'v )., tv ~: _ MC11 MonmorioIt .•• KeoIini\e .• CIoriI Fig Distribution of monmoriolite, kaolinite, illite and chlorite in sediments on tidal flats 176 BAo cAo KHOA HOC HOI THAo VAST - IRD V~ KHOA HOC BIt:N Chlorite concentration was only higher than that of monmoriolite in clay minerals The concentration was higher at MC 5, MC and lower in other cores Comparison with other clay minerals in tidal sediments, the concentration of chlorite was changed in depths but not so clear Fenspate in sediments was high in concentration at MC and MC 11 at depth from 30cm to the end of cores The lowest concentration of fenspate was at MC and MC 3, but not clearly changing in the cores NMLKJIHGFEDCBA ~': "" ,:. " " " Cootentofminefilis (%l , 0 ''' ( 1" '" of minerals Content (%) of minerals ("!o ) ", -,~J MC> ",J K Content eo • MC5 - ••• Quatlz -a·· Go.Ih~ \ 1M L -+ • • QUlII1z Go.IhiI • ~ Conlenlofminerals(%) o 10~ ~ ~ ~ ro ~ ~ 0r -~ -"~'~'~'~~~ ···• •· ·.: · " ~ " ~ f MC6 -.• F,,"-, • -.- """" Goelh ~ o o -" ~ "" !" l ConlentofmineraJs dcbaZYXWVUTSRQPONMLKJIHGFEDCBA ("to ) Fig Distribution of fenspate, quartz and goethite in sediments on tidal flats Quartz in tidal sediments was quite high in concentration at all cores In Table standard deviation of mineral is high with quartz, this mineral are most abundant in tidal sediment, if concentration of quartz changes that mean sedimentary environment are changed, these event are shown in MC (at 20-70 em in depth), MC (at 30 - 40cm in depth), MC (27-40 em in depth) and MC 11 (27-50 em in depth) (fig 8) Goethite had the highest concentration at MC 2, followed by those at MC 5, MC In the other cores, the change in concentration was not so high As the results, it is difficult to indicate for dynamic conditions, but it may be an indicator for physical chemical of sediment PROCEEDINGS ON MARINE SCIENCExwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJI 177 OF VAST - IRD SYMPOSIUM Generally, in three environments mentioned above, common clay minerals in sediment cores are kaolinite and illite The highest content in these clay minerals are in the order: MC > MC > MC > MC > MC 11 > MC Quartz was concentrated at MC Taking the concentrations of clay minerals and quartz as indicators for sedimentary processes, the accretion takes place where high clay minerals are concentrated and the erosion with low sedimentation rates is at the areas with high quartz concentration Finally connection all data in sediment cores shows that used 210Pb and 226Ra in monitoring sedimentation rates only true for the accretion environment, but environmental erosion did not specify the exact age This problem is seeing in sediment cores at MC 3, MC 8, MC 9, and MC 11, other sediment parameters are complementary to each other reflect sedimentary processes at tidal flats As difference of21°Pb and 226Ra at layers are causes of during time, mean diameters, clay minerals and condition environment All of them show clearly two sedimentary processes which are erosion and accretion in the North of Vietnam CONCLUSION Based on study results on the sedimentary characteristics of grain size, sedimentation rate, metals and minerals, three sedimentary environments are classified, including deltaic tidal flat sedimentary environment from Kim Son to southwest Do Son Peninsula, estuarine tidal flat sedimentary environment from northeast Do Don Peninsula to southwest Cat Ba Island and embayment tidal flat sedimentary environment from Cat Ba to Mong Cai In deltaic tidal flat sedimentary environment, two sedimentary processes of accretion that is dominant and erosion that appears at 30cm in depth of MC 8, MC 9, MC 10 and MC 11 are with common fine sediments and high sedimentation rate, accumulation of metals in sediment, high clay minerals concentration Estuarine tidal flat sedimentary environment is characterised by accretion process, dominating fine sediment, high sedimentation rate, highest accumulation of metals and high clay minerals Embayment tidal flat sedimentary environment is with low sedimentation rate, common coarse sediments, low accumulation of metals and high quartz The study results from a large area with 11 sediment cores are initial information on sedimentary environments For future understanding the sedimentary processes in the region, more studies and detail research plans should be developed and carried out These studies will contribute to use and manage tidal flats, function and fate of them in local environmental conditions.dcbaZYXWVUTSRQPONMLKJIHGFEDCBA A c k n o w le d g m e n t: S c ie n c e p o llu ta n ts and in T e c h n o lo g y tid a l V A S T C T G l1 -1 F u n d s J o r th is w o r k w e r e p r o v id e d (V A S T ) s e d im e n ta r y in tw o p r o je c ts : e n v ir o n m e n t o j th e a n d " S tu d y , a s s e s s a c c r e tio n a r e a o j th e R e d R iv e r D e lta " d u r in g -2 1 by V ie tn a m "A ssessm ent N o r th A cadem y a c c u m u la tio n oj oj oj V ie tn a m " w ith a n d e x p a n s io n o J m u d fla t o n c o a s ta l W e a r e in d e b te d code w ith c o lle a g u e s J r o m 178 BAo cAo th e In s titu te o f M a r in e E n v ir o n m e n t KHOA HOC HOI THAo a n d R e s o u r c e s fo r VAST - IRD V~ KHOA HOC BI~NdcbaZYX th e ir h e lp in s a m p le c o lle c tio n , s u b s a m p lin g a n d h a n d lin g REFERENCES Anh N T T, Giang N K (2006) Status metal pollutant of tidal sediment of Tien Yen - Ha Coi area, Quang Ninh O Provine Journal of Geology, Serial A, Vol 293, p.1-1xwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFED Anh N T T, Giang N K, An P V (2005) Environmetal geochemistry of sediments in estuary and tidal flat: A case study in Ha Long City, Quang Ninh province Journal of Geology, Serial B, Vol 26, p 55-64 A~pleby P G, Oldfield F (1978) The caculation 21 Pb to sediment Catena 5, p, 1-8 Appleby P G, Oldfield F (1992) Applications of 210Pb to sedimentation (Eds.), Uranium Series Disequilibrium Application to the Earth Clarendon Canadian Council of Ministers of the Environment, Cu N D (1991) Some characteristic geochemical sediments in Mangrove forest of coastal area in the North Vietnam Marine Environment and Resources, Vol 1, p 54-59 Science and Technics Publishing House, Ha Noi Cu N H, Tuan N V, Thanh T D, Tuan N Q, Nhon D H (2003) Geological structure and evolution of the Nghia Hung tidal flat area Marine Environment and Resources, Tome X, p 54 - 66 Science and Technology Publishing House, Hanoi Hai P S, et al (1999) Determination of Pb-210 in sediment and it's application Journal Analysis chemistry, physic and biology Vol 4, issue 4, pp 40-42 Hoai V T T, Huyen N X (2010) Composition characteristics of modern alluvial estuaries from Ba Lat to Day river mouths Journal of Marine Science and Technology, Vol 10, Issue 3, p 53-67 Publishing House for Science and Technology, Hanoi 10 Krishnaswami S, Lal D, Martin J M, Meybeck Science Letter Vol 11, p 407-414 11 Lan T D, Thanh T D (1991) Morphology, sediment distribution and accumulative process of tidal flood plain of coastal Kim Son area Marine Environment and Resources Vol 1, p.33-39 Science and Technics Publising House, Ha Noi of 210 Pb dates assuming 1999 Canadian M (1971) rate of supply of unsupported studies In: Ivanovich M., Harmon Press, Oxford, pp 731-778 environmental Geochronology quality guidelines, for estimation update 2002 of dating sediments of lake sediments Earth and Planet 12 Last W M, Smol J P (2001) Tracking Lisitzin A P (1986) N.33, Paris 14 Nhan N D, Am N M, Hoi N C, Dieu L V, Cavanho F P, Villeneuve J P, Catini C (1998) Organochlorine pesticides and PCBs in the Red River Delta, North Vietnam Marine Pollution Bulletin Vol 36, p 742-749 15 Nhon D H, Chien H T, Anh N T K, Vuong B V, Anh N N, An P H, Hung V M, Hai P S (2011) Sedimentation in the Bang La and Ngoc Hai intertidal zone, Hai Phong Joumal of Marine Science and Technology, Vol 11, Issue 1, p 1-13 Publishing House for Science and Technology, Hanoi 16 Nhon D H, Tuan N Q, Thanh T D, Cu N D, Cu N H, Toan N D (2012) Distribution sediments and heavy minerals in Hai Hau coastal area, Nam Dinh Province Joumal of Sciences and Technology, Vol 50, Issue E, p 1139-1150 Publishing House for Science and Technology, Hanoi 17 Robbins J A (1978) Geochemiscal and geophysical applications of radioactive lead In: Nkagru Biogeochemistry of Lead in the Environment Elsevier, The Netherlands, pp 285-393 18 Thanh T D (1999) Holocene stratigraphy and structure of tidal flats Hai Phong coastal area Journal of the Earth Science, Vol 3, p 197-206 Science and Techniques Publishing House, Ha Noi 19 Tue N T, Quy T D, Amano A, Hamaoka H, Tanabe S, Nhuan M T, Omori K (2011) Historical profiles of trace element concentrations in mangrove sediment from Ba Lat Estuary, Red River, Vietnam Water Air Soil Pollut Volume 223, 1315-1330 20 Perillo G, Wolanski Elsevier 21 Van den Bergh G D, Boer W, Schaapveld M A S, Duc D M, Van Weering T C E (2007) Recent sedimentation and sediment accumulation rates of the Ba Lat prodelta (Red River, Vietnam) Journal of Asian Earth Sciences Vol 29, p 545-557 E, Cahoon of geological Change Using Lake Sediments R.S 13 Principles Environmental a constant mapping of marine sediments D, Brinson M (Eds.) (2009) Coastal Wetlands: Unesco Vol - Springer Reports An Integrated in Marine Science J (Ed.), The Ecosystem Approach  ... clay minerals and condition environment All of them show clearly two sedimentary processes which are erosion and accretion in the North of Vietnam CONCLUSION Based on study results on the sedimentary. .. Thuy 164 The sedimentary processes on tidal flats in the north of Vietnam: initial results and implication future 17 Dinh Van Nhan, Chu Van Thuoc, Nguyen Xu an Quynh A preliminary study on variability... 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