Shaoming Pan

Pu and 137Cs in the Yangtze River estuary sediments: distribution and source identification.

Pu isotopes and (137)Cs were analyzed using sector field ICP-MS and γ spectrometry, respectively, in surface sediment and core sediment samples from the Yangtze River estuary. (239+240)Pu activity and (240)Pu/(239)Pu atom ratios (>0.18) shows a generally increasing trend from land to sea and from north to south in the estuary. This spatial distribution pattern indicates that the Pacific Proving Grounds (PPG) source Pu transported by ocean currents was intensively scavenged into the suspended sediment under favorable conditions, and mixed with riverine sediment as the water circulated in the estuary. This process is the main control for the distribution of Pu in the estuary. Moreover, Pu is also an important indicator for monitoring the changes of environmental radioactivity in the estuary as the river basin is currently the site of extensive human activities and the sea level is rising because of global climate changes. For core sediment samples the maximum peak of (239+240)Pu activity was observed at a depth of 172 cm. The sedimentation rate was estimated on the basis of the Pu maximum deposition peak in 1963-1964 to be 4.1 cm/a. The contributions of the PPG close-in fallout Pu (44%) and the riverine Pu (45%) in Yangtze River estuary sediments are equally important for the total Pu deposition in the estuary, which challenges the current hypothesis that the riverine Pu input was the major source of Pu budget in this area.

Heavy metal spatial variability and historical changes in the Yangtze River estuary and North Jiangsu tidal flat

This research focuses on the spatial and temporal patterns of heavy metals from the Yangtze River estuary and the tidal flat of north Jiangsu. Most heavy metals in the surficial sediments after normalization to Ti decreased seaward at the Yangtze River estuary. The core records showed that the heavy metal variations in the last 50years were primarily linked to natural weathering input of trace elements. However, significant heavy metal pollution (mainly Ni, Pb, Cd, Cu and As) were in the two study areas, with anthropogenic inventories accounting for 23-40% percent of the total pollution. Sequential extraction showed that Pb, Cu and Ni were present largely in the non-residual fraction, which indicated the potential bioavailability in the study areas. The SEM/EDS together with sequential extraction facilitated the easy tracing of the origin/sources of heavy metals in a simple way in the estuary and the tidal flat.

Sources of plutonium isotopes and 137 Cs in coastal seawaters of Liaodong Bay and Bohai Strait, China and its environmental implications

In order to investigate the sources of plutonium in seawaters of Liaodong Bay and Bohai Strait, China, surface seawater samples were collected and analyzed for 239+240Pu and 137Cs by radiochemical separation combined with ICP-MS and γ-spectrometry, respectively. A large variation of 239+240Pu activities was observed, ranging from 1.993 to 29.677 mBq/m3 in the Liaodong Bay and from 0.932 to 10.183 mBq/m3 in the Bohai Strait. 137Cs activities showed little variation between the investigated locations, which was attributed to the different behavior characteristics of 239+240Pu and 137Cs in seawaters. The 240Pu/239Pu atom ratios showed a significant variation between the Liaodong Bay (0.185) and Bohai Strait (0.225), indicating that Pu derived from the Pacific Proving Grounds might have been transported to the Bohai Strait but not yet to the Liaodong Bay, which could further provide valuable reference for evaluating the seawater exchange cycle between the Bohai Sea and Yellow Sea.

RECENT VARIATION IN SEDIMENT GRAIN SIZE IN THE MUD AREA OF CHANGJIANG SUBAQUEOUS DELTA AND ITS INFLUENCE FACTORS: RECENT VARIATION IN SEDIMENT GRAIN SIZE IN THE MUD AREA OF CHANGJIANG SUBAQUEOUS DELTA AND ITS INFLUENCE FACTORS

The subaqueous delta is a sink on the terrigenous clastic continental shelf.It contains tremendous information on environmental changes influenced by both the sediment supply and marine environmental dynamics.The core of SC09 was collected from the mud area of the subaqueous delta of the Changjiang River.Samples were taken for every 0.2cm of interval.Sediment grain sizes were measured by Mastersizer 2000 laser particle analyzer.Moreover,sediment grain-size sensitive populations were retrieved for analysis using the Empirical Mode Decomposition(EMD).The results show that the sensitive populations of grain-size are distinctly characterized by periodicity and a definite trend.The characteristics of fine grained sensitive populations were mainly relative to the changes in sediment supply from the Changjiang River,and the periodic changes and the trend of the coarse sensitive population reflect either the influence of extreme events,such as storm,or changes in the main course of Changjiang River.

MODERN SEDIMENTATION OF TIDAL INLET-TIDAL BASIN SYSTEM IN CAOFEIDIAN COASTAL AREA, BOHAI BAY, NORTHEASTERN CHINA: MODERN SEDIMENTATION OF TIDAL INLET-TIDAL BASIN SYSTEM IN CAOFEIDIAN COASTAL AREA, BOHAI BAY, NORTHEASTERN CHINA

Five sediment cores (200 cm) and twenty-two sea-bottom surface sediment samples have been collected in Caofeidian coastal area of Bohai Bay during field work in 2008. Grain size and 210Pb data as welll as underwater topographic section (carried out in 2006) have been used to analyze modern sedimentation of tidal inlet in Caofeidian coastal area of Bohai Bay. The results indicate that the sea bottom sediments are mainly composed of silty sand and their particle sizes are getting finer and finer from nearshore to offshore areas. The underwater topographic section has shown that the Laolonggou tidal channel was eroded by 213 cm from 1997 to 2006 on an average. On a decade scale,the Laolonggou channel is quite stable. According to 210Pb data,the accumulation rates in the river mouth and shallow lagoon area are between ca.0.9 cm/a and ca.1.5 cm/a.The results have shown the river mouth area has been greatly disturbed by human activities,such as digging and reclamation. This will positively increase the navigational channel silting and harbor silting. The water depth of Laolonggou tidal channel has been greatly attributed to the strong tidal currents,so in the harbor planning and navigational channel construction the tidal prism should be taken into account.