Qiangqiang Zhong, Linwei Li, Viena Puigcorbé, Dekun Huang, Tao Yu, Jinzhou Du. Contrasting behaviors of 210Po, 210Pb and 234Th in the East China Sea during a severe red tide: enhanced scavenging and promoted fractionation[J]. Acta Oceanologica Sinica. doi: 10.1007/s13131-021-1958-0
Citation:
Qiangqiang Zhong, Linwei Li, Viena Puigcorbé, Dekun Huang, Tao Yu, Jinzhou Du. Contrasting behaviors of 210Po, 210Pb and 234Th in the East China Sea during a severe red tide: enhanced scavenging and promoted fractionation[J]. Acta Oceanologica Sinica. doi: 10.1007/s13131-021-1958-0
Qiangqiang Zhong, Linwei Li, Viena Puigcorbé, Dekun Huang, Tao Yu, Jinzhou Du. Contrasting behaviors of 210Po, 210Pb and 234Th in the East China Sea during a severe red tide: enhanced scavenging and promoted fractionation[J]. Acta Oceanologica Sinica. doi: 10.1007/s13131-021-1958-0
Citation:
Qiangqiang Zhong, Linwei Li, Viena Puigcorbé, Dekun Huang, Tao Yu, Jinzhou Du. Contrasting behaviors of 210Po, 210Pb and 234Th in the East China Sea during a severe red tide: enhanced scavenging and promoted fractionation[J]. Acta Oceanologica Sinica. doi: 10.1007/s13131-021-1958-0
Third Institute of Oceanography, Ministry of Natural Resource, Xiamen 361005, China
2.
State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200241, China
3.
School of Science, Centre for Marine Ecosystems Research, Edith Cowan University, Joondalup, WA 6027, Australia
Funds:
The Science Research Foundation of the Third Institute of Oceanography, Ministry of Natural Resources under contract Nos 2017017 and 2019004; the China Postdoctoral Science Foundation under contract No. 2021M693780; the Foundation of Xiamen Institute of Marine Development under contract No. K201301; the Science and Technology Plan Projects of Guangxi Zhuang Autonomous Region under contract No. 2017AB30024.
210Po, 210Pb, and 234Th were determined in water columns of the East China Sea (ECS) to investigate their biogeochemical behaviors during a severe red tide event. Dissolved 210Po, 210Pb, and 234Th accounted for large fractions of the total phases. The abnormally high concentrations of dissolved 210Pb were observed. Partition behaviors of these radionuclides were influenced by particle content effect and particle composition based on distribution coefficient (Kd) vs. total suspended matter (TSM) content and Kd vs. ratios of particulate organic carbon and total suspended matter content (POC/TSM ratios). The peaks of mass specific activities of 210Po, 210Pb, and 234Th indicated that degraded particles could have an intensified enrichment ability for radionuclides compared with the surficial suspended matters. Fractionation factor of 210Po and 210Pb (FPo/Pb) (>1) and fractionation factor of 210Po and 234Th (FPo/Th) (>1) were much higher at algal blooming regions than that at non-blooming stations, indicating that algal blooms promoted the fractionation of 210Po against 210Pb and 234Th, and proving that 210Po exhibited a stronger affinity for biogenic particles than 210Pb and 234Th when POC content increased in the sea. POC/210Po, POC/210Pb and POC/234Th content ratios sharply decreased with depth in both algal bloom and non-bloom stations. The outbreak of algal bloom promoted the complexity of suspended particles and increased the variability of POC/tracer ratios in the different depth of the shallow seas. More considerations should be taken to the difficulty of the selection of export interface and the suitable tracers when algal blooming occurs.
Figure 1. Map showing the locations of the stations in the Changjiang River and East China Sea in July 2016 (a). Red stars are four stations where radionuclides were measured, with two stations (A1-5 and A3-9) affected by algal blooms (b), and two no-bloom stations (A6-11 and A8-7) (c). The regional currents during summer are included: Changjiang Dilute water (CDW), Zhejiang-Fujian Coast Current (ZFCC), Yellow Sea Coastal Current (YSCC) and Taiwan Warm Current (TWC). Black dots in red dashed boxes represent the locations where algal blooms were observed.
Figure 2. Vertical distribution plots of temperature (°C) (a) and salinity (b) along the defined section of the East China Sea off the Changjiang River Estuary in July 2016.
Figure 3. Profiles of concentrations of DO and Chl a, contents of TSM and POC in four stations. Horizontal gray line denotes seafloor.
Figure 4. Relationships between POC and TSM (a), POC and PN (b), POC and Chl a (c), POC and five nutrients (NO3- (e), NO2- (f), NH4+ (g), PO43- (h), SiO32- (i)) and between PN and Chl a (d) during algal blooming in July 2016. The dotted lines indicate the correlation between the two parameters and the equation is presented in the corresponding panel. Red symbols indicate outliers of the general trend due to particularities of those specific samples, as described in each graphic.
Figure 5. Variations of stable organic carbon isotopic ratio (δ13C) and organic carbon and nitrogen ratio (POC/PN ratio) in particles collected in bloom (green) and non-bloom (blue) stations.
Figure 6. 210Po, 210Pb, and 234Th activity profiles for the dissolved (D, black squares), particulate (P, red dots), and total (dissolved+particulate; T, blue triangles) phases. Horizonal line indicated the bottom depth.
Figure 7. Relationships between POC content and particulate 210Po, 210Pb and 234Th activity in surface (black squares), middle (red dots), and bottom (blue triangles) waters.
Figure 8. Profiles of the POC/TSM ratio (a) and mass specific activities of 210Po (b), 210Pb (c), and 234Th (d) at the four stations. The green highlighted regions represent the peaks of mass specific activity of 210Po, 210Pb and 234Th in water columns.
Figure 9. Relationships between the variation in the distribution coefficient (LogKd in mL/g) for 210Po, 210Pb, and 234Th and the particle content (LogTSM in mg/L) (a) and organic carbon content in TSM (b).
Figure 10. Fractionation factors of 210Po to 210Pb (a), 210Po to 234Th (b) and 210Pb to 234Th (c) at the four sampling stations.
Figure 11. The ratios of POC content to 210Po, 210Pb, and 234Th activities in the particulate samples.
Figure 12. POC/210Po vs. POC/210Pb (a) and POC/210Po vs. POC/234Th (b) in the particulate samples. Data enclosed in black ellipse represent samples collected from surface layers at algal blooming stations. Data enclosed in blue ellipse represent fecal pellets or resuspended particulate matters. The red dashed lines indicate the 1:1 line.