210Pb and 137Cs measurements in the Circum Bohai ... - Springer Link

Front. Earth Sci. China 2008, 2(3): 276–282 DOI 10.1007/s11707-008-0046-5

RESEARCH ARTICLE

210

Pb and 137Cs measurements in the Circum Bohai Sea coastal region: sedimentation rates and implications Fu WANG (*)1,2, Hong WANG1, Jianfen LI1, Yandong PEI1, Changfu FAN1, Lizhu TIAN1,3, Zhiwen SHANG1, Meiyu SONG1,4, Yan GENG1,4 1 Tianjin Institute of Geology and Mineral Resources, Tianjin 300170, China 2 Chinese Academy of Geological Sciences, Beijing 100037, China 3 China University of Geosciences, Beijing 100083, China 4 College of Earth Sciences, Jilin University, Changchun 130026, China

E

Higher Education Press and Springer-Verlag 2008

Abstract The representative 210Pb and 137Cs age-depth profiles were selected from more than 100 sites in the Circum Bohai Sea (CBS) coastal region to examine the sedimentation rates and associated environmental changes. There are three unique 210Pbexc distribution patterns: 1) ideal-decaying type, representing relatively constant sediment supply and quieter environmental setting; 2) wiggling type, but with approximately equivalent amplitude, representing coarser sediments and associated stronger flow current environment; and 3) episodic-eventinfluencing type, each representing typhoon storm- influenced depositional environment. Our results also show that there is a lower sedimentation rate (ca. 0.1 cm/a) in the coastal lowlands, a higher sedimentation rate (ca. 0.5– 3 cm/a) in the intertidal flat and an intermediate rate of ca. 0.58 cm/a in the subtidal zone near the Huanghua Harbor. The interbedded silt layer occurring in the core sediment reveals lower 210Pb activities, indicating a discontinuous sedimentation mostly due to typhoon events which dwarfs against 210 Pb and 137 Cs applicability. Overall, the 210Pb and 137Cs measurements of the present study provide physical insight into the evaluation of the coastal-marine ecological environment and associated management. Keywords 210Pb and 137Cs, sedimentation rate, Circum Bohai Sea (CBS) coastal region

1

Introduction

The coastal sedimentation rate of the last 100 years serves as an important factor while assessing the recent Received September 20, 2007; accepted April 10, 2008 E-mail: [email protected]

geo-environmental changes. Sea levels continuously rise which will significantly threaten the open coastal ecological setting, including extensive low-lying tidal flat areas (Gornitz et al., 2002; Abhay and Daniel, 2004; Nicholls et al., 2007). A suitable sedimentation rate, in terms of the coastal topographic aggradations will prevent potential disasters from climatic warming and intensified human activities. With the half life of 22.3 a, natural radioisotope 210Pb, a member of the 238U decay series, has been widely used for dating recent sedimentation rates in lakes (Krishnaswamy et al., 1971; Appleby and Oldfield, 1978), floodplains (He and Walling, 1996; Goodbred and Kuehl, 1998; Rolf et al., 2003) and coastal areas (Koide et al., 1973; Milan et al., 1995; Wilfried et al., 1995; Andersen et al., 2000; Meng et al., 2005). As an anthropogenic radioisotope, 137 Cs was introduced into the environment by the human nuclear weapon tests initiated in 1954 (Pennington and Tutin, 1973; Delaune et al., 1978; Milan et al., 1995; Goodbred and Kuehl, 1998; Stam, 1999) which peaked in 1963, and was then followed by a subsidiary peak due to the Chernobyl accident in 1986 (Callaway et al., 1996). There was a measurable, but regional peak referring to 1973 due to the Chinese and French nuclear weapon test at that time (Mishra et al., 1975; Jha et al., 2003). Of note in the last decades, 137Cs as a sediment tracer, in combination with 210Pb dating has been successfully applied to the investigation of erosion and deposition on the earth’s surface (Chung and Chang, 1995; Andersen et al., 2000; Su and Huh, 2002; Li et al., 2003; John et al., 2004; Meng et al., 2005; Wang, 2006a). The assumption of 210Pb dating stands on sediment deposits in a relatively quiet environmental setting in which no re-suspension and secondary sediment transport occurs once settled (Appleby and Oldfield, 1978). Constant Flux and Supply (CFS), Constant Initial

210

Pb and 137Cs measurements in the Circum Bohai Sea coastal region

Concentration (CIC) and Constant Rate of Supply (CRS) models are commonly used for 210Pb dating (Krishnaswamy et al., 1971; Robbins, 1978; Appleby and Oldfield, 1978). However, this assumption is hardly met in the intertidal zone and shallow sea area because of the influence of tidal currents, littoral currents, typhoons and winter storms. These will disturb seabed sediments leading to the changes in particle-absorbed radionuclide content in the coastal sediments. On the other hand, a thorough examination of sedimentation rate by the means of 210Pb and 137Cs measurements would shed light on the assessment of sedimentation in the Circum Bohai Sea (CBS) region.

2

Methods

The 210Pb dating method was used in the CBS region in the 1980s and 137Cs tracing was primarily used in the region in the 1990s. From 1998 to 2007, we have collected numerous cores (1–2 m long) by Eijkelkamp with 59 mm diameters on the intertidal zone of the Liaodong Bay, Bohai Bay and Laizhou Bay (Fig. 1). In the past 10 years, our research group has taken 52 cores for 210Pb and 137Cs dating. We also collected many 210Pb and 137Cs data reported by others in the study area, including the coastal low lands, intertidal zones and shallow sea areas (Fig. 1). Different sampling methods were used in the study area. Trenching was done on the coastal lowlands, where sampling was carried out along the trenching profile by small case. Eijkelkamp sampling method was used to sample on the intertidal zone, and box core applied to the shallow sea area (Li and Shi, 1995a). When sampling, the core samples were kept undisturbed. The cores taken by our research group were sliced at 2 cm to 5 cm intervals. About 10g sediments were taken for radioisotopic analysis. Wet and dry weight, and water content were measured and grain size was tested by the Mastersizer 2000 in Nanjing University. Sub-samples were taken and ground after being air-dried in the laboratory. Samples were stored in an airproof box for more than one month to ensure the equilibrium between 226 Ra and its daughter 222Rn (half life 3.8 d), an inert gas. The activities of 210Pb, 137Cs and 226Ra were measured by gamma detector in different laboratories, i.e. the Nanjing Institute of Geography & Limnology, the Chinese Academy of Sciences and the Stony Brook University using the well detector (GWL-120-15) (Li et al., 2003), the Chinese Academy of Agricultural Sciences using the Hyperpure coaxial Ge detector (BE5030, CANBERRA) (Meng et al., 2005), and the Tianjin Institutes of Geology and Mineral Resources (Hyperpure coaxial Ge detector (GMX-60)). Sedimentation rate of 210Pb measurement is calculated using the equation below:

277

S~lD=lnðCo =C Þ:

ð1Þ

S — Sedimentation rates (cm/a); l — decay constant (l50.031/a); D — depth z; Co — the activity of the tope layer sediments (dpm/g or Bq/kg); C — the activity of the sediments at depth z layer (dpm/g or Bq/kg). The CIC model was applied to calculate the average sedimentation rates for most sediment cores and the CRS model was used for S1 and S2 cores (Fig. 2) because sediment supplement and deposition are different in coastal lowlands, intertidal zones and shallow sea areas. S1 and S2 were taken from coastal lowlands where there is thought to be a constant sediment supply and quieter environmental setting which meets the CRS assumption.

3 3.1

Results and discussion Distribution of sedimentation rates in the CBS region

The previous research results have revealed that sedimentation rates in Liaodong Bay decreased from the Xiaolinghe estuary to the Liaohe estuary, Wulihe estuary and adjacent sea area (Fig. 1) (Xia et al., 1983; Yang et al., 1993; Song et al., 1997). High sedimentation rates occurred in Laizhou Bay and the Yellow River Delta area. Lower sedimentation rates were found in the shallow water near the central Bohai Bay where there is only 0.2 cm/a detached in the middle of the Bohai Sea channel (Li and Shi, 1995b; Li and Gao, 2002). Based on 36 210Pbexc and 137Cs scores taken by our research group (Wang et al., 2002, 2003; Li et al., 2003; Wang, 2006a; Wang et al., 2006b, 2008) from the coastal lowlands, intertidal zones and shallow sea areas of the Bohai Bay, the activities of 210Pbexc are within the range of 0–11.11 dpm/g. The activities of 137Cs are within the range of 0–1.60 dpm/g. Sedimentation rate on the west coast of the Bohai Bay shows two sub-areas: 1) Lower sedimentation rate (,0.1 cm/a) in the coast, and 2) High sedimentation rate (0.5–3 cm/a) in the open tidal flats (Fig. 1). The sedimentation rate of the western Bohai Bay decreases from the Jiyunhe estuary to Tianjin New Port. It then increases from Tianjin New Port to the southern open tidal flats. The core taken from Huanghua Harbor shows that the littoral currents from NW to SE was blocked by the seawall of the harbor which leads to a high sedimentation rate near shoreline in the north area of the harbor. Sedimentation rates are 0.9–1.12 cm/a in this area. Further seaward, sedimentation rates become higher in the southern area of the harbor. Core HHG6 with the higher sedimentation rate (,1.36 cm/a) occurs to implicate sufficient sediment sources supplements (Fig. 1).

278

Fu WANG, et al.

Fig. 1 Map showing locations of the 210Pb and 137Cs cores collected on the CBS Coasts and the sea area 1–210Pb and 137Cs dated cores by Tianjin Institute of Geology and Mineral Resources (TIGMR) (49 cores); 2–210Pb and 137Cs dated cores (3 cores) TIGMR as cooperator (Meng et al., 2005); 3–210Pb dated cores by the others (73 cores) (Xia et al., 1983; Ye et al., 1987, 1991, 1992; Du et al., 1990; Xu and Liu, 1991; Li and Yuan, 1992; Yang et al., 1993; Li and Shi, 1995a, 1995b; Cheng et al., 1995; Song et al., 1997; Li and Gao, 2002 ); 4–lower sedimentation rate area (ca. 0.1 cm/a) in the coastal lowlands; 5–high sedimentation rate (ca. 0.5– 3 cm/a) in the intertidal flat

3.2

210

Pbexc depth distribution pattern

Selected 210Pbexc curves show the three major depth distribution patterns in the CBS region (Fig. 3) (Wang et al., 2006b). These patterns represent different sedimentation and associated coastal environments. 1) Ideal-decaying-type. The 210Pbexc decays with depth. S1 and S2 (Fig. 2) taken from the coastal lowland of the western coast of the Bohai Bay belong to this type. Some cores taken from the intertidal zone of the Liaodong Bay

and most cores taken from the Bohai Sea also fit into this pattern. They represent a coastal environment, where sediment sources supplement is relatively constant and the environmental setting is quieter. 2) Wiggling with approximately equivalent amplitude. 210 Pbexc did not decay with depth, but there was wiggling with an approximately equivalent amplitude. Core C1 and C3 (Fig. 2), located in the sandy area of the intertidal zone between the Lujuhe and the Duliujianhe (Fig. 1) belong to this type. The activities of 210Pbexc

210

Pb and 137Cs measurements in the Circum Bohai Sea coastal region

279

Fig. 2 Depth distribution of 210Pbexc and 137Cs radioactivity, represented as S1, S2, L1, L2, L3, Q1, L5 and L6 (by TIGMR) (Li et al., 2003), C1, C3 and C4 (by TIGMR, and by Chinese Research Academy of Environmental Sciences) (Meng et al., 2005)

are rather low primarily due to coarser sediments and strong current flow. 3) Episodic-event-influencing type. This is a type influenced chiefly by typhoon storm surges. This is characterized by the low activity of 210Pbexc, which primarily occurs in the shallow sea area and in the intertidal zone. During typhoon season, strong coastal erosion can coarsen the seabed sediments resulting in lower activities of 210Pbexc. Core L5 near Laolangtuozi and core Q1, C4 at Mapengkou represent this type (Figs. 1 and 2). For example, the 210Pbexc of C4 shows abnormally lower activities at the core depth of 58–80 cm. According to the field sampling records, shelly gravels were found at this core depth, meaning storm surge sedimentation. A similar situation was also reported in the North Sea in Europe (Andersen et al., 2000) and the Chesapeake Bay in the U.S. (Nie et al., 2001). 3.3

Effect of sediment mixing layer

Human coastal reclamation and physical processes, including bioturbation, storm events, and littoral

currents, can cause sediment mixing in the coastal area which disturbs the activity of 210Pb on the top of core sediments and the distribution of the 137Cs peaks and maximum depth. This lowers sedimentation rates through 210Pbexc and 137Cs dating. For example, core C4, taken from the west coast of Bohai Bay shows that 137 Cs gives sedimentation rate of 2.5 cm/a and 210Pb gives sedimentation rates of 1.8 cm/a (Fig. 2) (Meng et al., 2005). The mixing layers also cause inefficiency while identifying 137Cs peak in the core sediments which was witnessed in the core near Huanghua Harbor (Wang et al., 2008). Anderson et al (2000) has successfully used 210Pb and 137 Cs to study the mixing depth on some European intertidal mudflats. Their results show that the mixing depth may increase with tidal range. On macrotidal and mesotidal mudflats, the mixing is chiefly caused by episodic storm events, while bioturbation prevails on microtidal mudflats. For the microtidal environment of the mudflats of the Bohai Bay, bioturbation influences the results of

280

Fu WANG, et al.

Fig. 3 Three (a, b, c) measured depth distribution of 210Pbexc radioactivity S2, L1 and L5–measured profiles by TIGMR; 1–Ideal-Decaying-type; 2–Wiggling with Approximate Equivalent Amplitude; 3– Episodic-Event-Influencing-type 210

Pb and 137Cs dating, such as core Q1, C3, L4 and L5 (Wang et al., 2002, 2003; Li et al., 2003; Meng et al., 2005). 3.4

Inventory of 210Pb and 137Cs

Inventory of 210Pb and 137Cs is an important index to study the modern sedimentation. Goodbred and Kuehl (1998) recently show that using penetration and raw inventory values as proxies for accretion and linear correlation of these measures yields poor results. However, most disagreement among the data is found at the high values corresponding to very coarse or fine grained sites. Since 137Cs and 210 Pb are found to be absorbed within the fine-size fractions, inventory values were recalculated by normalizing to 50% clay based on the percent mass of clay-sized sediment and show some good results to study sedimentation rates. Walling and He (1992) also give good suggestions on how to use the inventory method for calculating accretion rates. Their work shows that radioisotope activity above the level of atmospheric fallout represents those associated with sediment input. This excess inventory component can be related to sediment deposition by assuming a mean activity for catchments derived sediment. For 210 Pbexc, He and Walling (1996) worked out an equation for sedimentation rate. Considering the data given by our research group since 1998 (Wang et al., 2002, 2003; Li et al., 2003; Wang, 2006a; Wang et al., 2006b; Liu et al., 2007; Wang et al., 2008), S1 and S2, taken from coastal lowland may provide useful information on the atmospheric fallout history of 210 Pb and 137Cs. There is a lower sedimentation rate (,0.1 cm/a) given to S1 and S2, meaning 10 cm thick sediments for the last 100 years. This implies that little sediments may be transported from other places and little

210

Pb and 137Cs in sediments are transported from other places. The most inventories of 210Pb and 137Cs calculated by Wang and Li (2002) could be from atmospheric fallout. Therefore, this paper suggests that for cores S1 and S2, the average inventory of the 210Pb is 20.55 dpm/cm2 and that of 137Cs is 5.50 dpm/cm2 for the atmospheric fallout on the west coast of Bohai Bay. This is a very early result and more work will be done in the coming years. 3.5

Effect of marine episodic events

Monitoring marine events can improve interpretation of Pb and 137Cs data. To monitor the change of the mudflats on the Mapengkou intertidal zone by leveling crosssections of the intertidal zone of the study area would deepen our understanding. For example, the storm surge on Oct.11–12, 2003 accumulated 30–50 cm sediments in this area (Fig. 4). Sediments transported by the storm largely disturb the activity of 210Pb/137Cs so as to weaken the measurement of sedimentation rate. In addition, lower concentrations of 210Pb in Q1 and L1–3, L5 and HHG6 could highlight storm surge events (Fig. 2).

210

4 Summaries Using 210Pb and 137Cs can help us understand the sedimentation rate and related coastal environmental nature, even discontinuous sedimentation happens in the region. Sedimentation rate delineates two sub-areas on the west coast of the Bohai Bay: 1) the lower sedimentation rate of the coast, ,0.1 cm/a; and 2) a high sedimentation rate of the open tidal flat, 0.5–3 cm/a. The sedimentation rate of the western Bohai Bay decreases from the Jiyunhe

210

Pb and 137Cs measurements in the Circum Bohai Sea coastal region

281

Fig. 4 Monitoring section of shallow strata across Beidagang Lagoon-Mapengkou modern intertidal zone (Wang et al., 2002; Wang, 2006a) 1–sand; 2–paleosol; 3–clay; 4–sand with muddy layers; 5–chenier; 6–mud; 7–muddy sand; 8–age; 9–210Pb/137Cs dating and tracing cores; 10–Eijkelkamp cores

estuary to Tianjin New Port and then it increases from Tianjin New Port to the southern open tidal flat. There are three types of the 210Pbexc: 1) ideal-decaying type, representing relatively constant sediment supply and a quieter environmental setting; 2) wiggling type, but with approximately equivalent amplitude, representing coarser sediments or associated stronger flow current environments; and 3) episodic-event-influencing type, representing typhoon storm-influenced depositional environment. The coastal lowlands of the Bohai Bay region are relatively constant depositional environments where 210Pb and 137Cs dating could apply. In the open tidal flat of the CBS region, a few sites can be used for 210Pb and 137 Cs dating because of episodic storm surges. 210Pb and 137 Cs measurements can also provide more useful information for the study area if we know the mixing depth, inventory and the history of the marine events. Acknowledgements Firstly, thanks should be given to Dr. Zhongyuan Chen, who gave many helpful suggestions on this paper. Thanks should be also given to Mr. Yufa Zhang and Mr. Jinqi Zhang (TIGMR), who contributed to the fieldwork. We are also deeply in debt to Mr. Weilan Xia (Key Laboratory of Lake Sedimentation & Environment, Chinese Academy of Sciences), Drs. S. L. Goodbred, L. Robbins, C. Holmes, A. S. Kolker and Mrs M. Marot, who kindly helped measure 210Pb and 137 Cs activity.

References Abhay K S, Daniel R (2004). Levacher Sea level rise and its consequences on coastal environment. VIII e`mes Journe´es Nationales Ge´nie Civil-Ge´nie Coˆtier, Compie`gne, 7–9 Andersen T J, Mikkelsen O A, Moller A L, et al (2000). Deposition and mixing depths on some European intertidal mudflats based

on 210Pb and 137Cs activities. Continental Shelf Research, 20: 1569–1591 Appleby P G, Oldfield F (1978). The calculation of 210Pb dates assuming a constant rate of supply of unsupported 210Pb to the sediment. Catena, 5: 1–8 Callaway J C, Delaune R D, Patrick W H (1996). Chernobyl Cs-137 used to determine sediment accretion rates at selected north European coastal wetlands. Limnology and Oceanography, 41(3): 444–450 Cheng G D, Ye Y G, Diao S B (1995). 210Pb profile and redeposition of the Yellow River Delta. Marine Geology & Quaternary Geology, 15(2): 1–10 (in Chinese, with English abstract) Chung Y, Chang W C (1995). Pb-210 fluxes and sedimentation rates on the lower continental slope between Taiwan and the South Okinawa Trough. Continental Shelf Research, 15(2/3): 149–164 Delaune R D, Patrick W H, Buresh R J (1978). Sedimentation rates determined by 137Cs dating in a rapidly accreting salt marsh. Nature, 275: 532–533 Du R Z, Liu G X, Zhou Y H, et al (1990). Modern sedimentation rate and sedimentation process in Bohai Bay. Marine Geology & Quaternary Geology, 10(3): 15–22 (in Chinese, with English abstract) Goodbred S L, Kuehl S A (1998). Floodplain processes in the Bengal Basin and the storage of Ganges-Brahmaputra River sediment: An accretion study using 137Cs and 210Pb geochronology. Sedimentary Geology, 121(3): 239–258 Gornitz V, Couch S, Hartig E K (2002). Impacts of sea level rise in the New York City metropolitan area. Global & Planetary Change, 32: 61–88 He Q, Walling D E (1996). Use of fallout Pb-210 measurements to investigate longer-term rates and patterns of overbank sediment deposition on the floodplains of lowland rivers. Earth Surf Process Landforms, 21: 141–154 Jha S K, Chavan S B, Pandit G G, et al (2003). Geochronology of Pb and Hg pollution in a coastal marine environment using global fallout 137Cs. Journal of Environmental Radioactivity, 69: 145– 157 John P, Gregg B, Irena Z (2004). 137Cs and excess 210Pb deposition patterns in estuarine and marine sediment in the central region of

282 the Great Barrier Reef Lagoon north-eastern Australia. Journal of Environmental Radioactivity, 76: 81–102 Koide M, Bruland K W, Goldberg E D (1973). 228Th/232Th and 210Pb geochronoligies in marine and lake sediments. Geochim Cosmochim Acta, 37: 1171–1187 Krishnaswamy S D, Marin J M, Meybeck, M (1971). Geochronology of lake sediments. Earth and Planetary Science Letters, 11: 407–414 Li F Y, Yuan W (1992). Stage profiles of 210Pb and implication of migration of the channel to the modern Yellow River Delta. Oceanologia Et Limnologia Sinica, 23(5): 566–571 (in Chinese, with English abstract) Li F Y, Shi Y L (1995a). Study of the modern sedimentation in the Bohai Sea. Oceanographic Sciences, 2: 47–50 (in Chinese, with English abstract) Li F Y, Shi Y L (1995b). Accumulation rates of sediment and sedimentary environment in the south Bohai Sea. Journal of Oceanography of Huanghai & Bohai Seas, 13(2): 33–37 (in Chinese, with English abstract) Li F Y, Gao S (2002). Contemporary deposition rates of fine grained sediment in the Bohai and Yellow seas. Oceanologia Et limnologia Sinica, 33(4): 364–369 (in Chinese, with English abstract) Li J F, Wang H, Xia W L, et al (2003). 210Pbexc and 137Cs dating and modern sedimentation rate on the western coast of Bohai Bay. Geological Survey and Research, 26(2): 114–128 (in Chinese, with English abstract) Liu Z G, Wang Fu, Pei Y D, et al (2007). 137Cs and 210Pb distribution and modern sedimentation in the north and south intertidal zones of Sanhe Island, Tianjin, China. Geological Bulletin of China, 26(7): 864–868 (in Chinese, with English abstract) Meng W, Lei K, Zheng B H, et al (2005). Modern sedimentation rates in the intertidal zone on the west coast of the Bohai Gulf. Acta Oceanologica Sinica, 24(3): 46–53 Milan C S, Swenson E M, Turner R E, et al (1995). Assessment of the 137Cs method for estimating sediment accumulation rates: Louisiana salt marshes. Journal of Coastal Research, 11(2): 296–307 Mishra U C, Lalit B Y, Sethi S K, et al (1975). Some observations based on the measurements on fresh fallout from the recent Chinese and French nuclear explosion. Journal of Geophysical Research, 80(36): 5045–5049 Nicholls R J, Wong P P, Burkett V R, et al (2007). Costal systems and low-lying areas. In: Parry M L, Canziani O F, Palutikof J P, et al, Eds. Climate Change 2007: Impacts, Adaptation and Vulnerability, Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge: Cambridge University Press, 315–356 Nie Y H, Suayah I B, Benninger L K (2001). Modeling detailed sedimentary 210Pbexc and fallout 239,240Pu profiles to allow episodic events: An application in Chesapeake Bay. Limnol Oceanogr, 46(6): 1425–1437 Pennington W, Tutin T G (1973). Observation on Lake Sediments using Fallout 137Cs as a Tracer. Nature, 242: 324–326 Robbins J A (1978). Geochemical and geophysical applications of radioactivity lead. In: Nriagu J D, Ed. The Biogeochemistry of lead in the Environment. Amsterdam: Elsevier/North Holland Biomedical Press, 285–383

Fu WANG, et al. Rolf A, Laurence M B, Thomas D, et al (2003). Episodic sediment accumulation rate on Amazonian flood plains influenced by El Nino/southern Oscillation. Nature, 425 : 493–497 Song Y X, Zhan X W, Wang Y G (1997). Modern sedimentation in the north estuary of Liaodong Bay. Acta Oceanologica Sinica, 19(5): 145–149 (in Chinese, with English abstract) Stam M H (1999). The dating of fluvial deposits with heavy metals, 210 Pb and 137Cs in the Geul Catchment (the Netherlands). Phys Chem Earth (B), 24(1–2): 155–160 Su C-C, Hu C (2002). 210Pb, 137Cs and 239,240Pu in East China Sea sediments: sources, pathways and budgets of sediments and radionuclides. Marine Geology, 183: 163–178 Walling D E, He Q (1992). Interpretation of caesium-137 profiles in lacustrine and other sediments: the role of catchment-derived inputs. Hydrobiologia, 235/236: 219–230 Wang F (2006a). Modern Accumulation rates and Land Surface Environmental Changes of Tianjin and its Coastal Area. Graduation Thesis for Master Degree. Jilin: Jilin University, 1– 64 (in Chinese, with English abstract) Wang F, Pei Y D, Liu Z G, et al (2008). Sedimentary characteristics of Huanghua Harbour traced by 137Cs. Geological Bulletin of China (in press; in Chinese, with English abstract) Wang F, Wang H, Li J F, et al (2006b). Current study of 210Pb and 137 Cs geochronology in the Circum Bohai Sea Region. Geological Review, 52(2): 244–250 (in Chinese, with English abstract) Wang H, Jiang Y, Li J F, et al (2003). 14C,137Cs,210Pb dating and accelerated tendency of the present sedimentation rate along the Laolangtuozi coast of the Bohai Sea. Geological Bulletin of China, 22(9): 658–664 (in Chinese, with English abstract) Wang H, Li J, Zhang Y F, et al (2002). Modern Sedimentation of the Muddy Coast (accumulation rate, erosion and coastline change) and High Resolution Dating Report. Tianjin Institute of Geology and Mineral Resources Report Wilfried B M, Ten B, Pieter G E, et al (1995). Fine-grained Sediment Deposition on Mussel Beds in the Oosterschelde (The Netherlands), Determined from Echosoundings, Radio-isotopes and Biodeposition Field Experiments. Estuarine, Coastal & Shelf Science, 40: 195–217 Xia M, Zhang C H, Ma Z B (1983). 210Pb measurement and sedimentation rates on Zhujiang estuary and Jinzhou Bay. Chinese Science Bulletin, 5: 291–295 (in Chinese) Xu J S, Liu Z H (1991). The Introduction of the Development of Huanghua Coast. Ocean press, 1–93 (in Chinese) Yang S L, Liu G X, Du R Z, et al (1993). Study of the modern sedimentation rate through 210Pb age dating, Liaodong Bay. Acta Sedimentologica Sinica, 11(1): 128–135 (in Chinese, with English abstract) Ye Y G, He J, Diao S B, et al (1991). Geochemistry of 210Pb, Al, Fe, Mn, and Cu of core ZK226 in the modern Yellow River Delta. Marine Geology & Quaternary Geology, 11(4): 25–33 (in Chinese, with English abstract) Ye Y G, He J, Diao S B, et al (1992). Standardization of 210Pb profile in the modern Yellow River Delta–the correlation method of grain size. Scientia Geographica Sinica, 12(4): 379–386 (in Chinese, with English abstract) Ye Y G, Xue C D, Diao S B (1987). 210Pb Evidence of the lobe model in modern Yellow River Delta. Marine Geology & Quaternary Geology, 7: 75–80 (in Chinese, with English abstract)