Seasonal and spatial variations of chloroform, trichloroethylene, tetrachloroethylene, chlorodibromomethane and bromoform in the Northern Yellow Sea and Bohai Sea

2019 ◽  
Vol 16 (2) ◽  
pp. 114 ◽  
Author(s):  
Ying Wei ◽  
Zhen He ◽  
Gui-Peng Yang
Keyword(s):  
Yellow Sea ◽  
Bohai Sea ◽  
Yellow River ◽  
Spatial Variations ◽  
Coastal Current ◽  
Chl A ◽  
Volatile Halocarbons ◽  
Terrestrial Input ◽  
Northern Yellow Sea ◽  
Hydrographic Features

Environmental contextVolatile halocarbons play significant roles as halogen carriers in atmospheric chemistry where they contribute to global warming. We studied temporal and spatial variations of volatile halocarbons in the Northern Yellow Sea and Bohai Sea, and showed that their concentrations were governed by terrestrial input, hydrographic features and biological activity. The emission of volatile halocarbons from coastal regions could have important impacts on the budgets of atmospheric reactive halogen. AbstractConcentrations of five volatile halocarbons (VHCs), namely, chloroform (CHCl3), trichloroethylene (C2HCl3), tetrachloroethylene (C2Cl4), chlorodibromomethane (CHBr2Cl) and bromoform (CHBr3), in the Northern Yellow Sea and Bohai Sea were determined during the spring of 2013 and autumn of 2012. Strong seasonality in the concentrations of VHCs (except for CHCl3) were observed. Concentrations of CHCl3 were markedly higher (1.5 fold) to coincide with the higher concentration of chlorophyll a during the spring. The elevated concentrations of C2HCl3, C2Cl4, CHBr2Cl and CHBr3 were found to match with the higher inputs of land runoff during autumn. The VHCs distributions evidently decreased along the freshwater plume from the mouth of rivers, such as Yellow and Yalu Rivers, to the open sea. The elevated concentrations of the selected halocarbons arise from terrestrial input, complicated hydrographic features, such as the Yellow River effluent, Yalu River, Yellow Sea Coastal Current and Yellow Sea Cold Water, and biological release by phytoplankton. Correlation analyses were conducted among Chl-a, salinity and the concentrations of these gases to investigate possible controls for the concentrations of these gases. Significant correlation was only observed between the concentrations of CHBr2Cl and Chl-a in the surface layer during spring. We made the tentative conclusion that phytoplankton biomass might not be the main limiting factor of sources of VHCs in the surface water. The sea-to-air fluxes indicated that the Northern Yellow Sea and Bohai Sea act as sources of gas in the atmosphere during spring and autumn.

Data assimilation in a coupled physical-biological model for the Bohai Sea and the Northern Yellow Sea

2008 ◽  
Vol 59 (6) ◽  
pp. 529 ◽  
Author(s):  
Qing Xu ◽  
Hui Lin ◽  
Yuguang Liu ◽  
Xianqing Lv ◽  
Yongcun Cheng
Keyword(s):  
Chlorophyll A ◽  
Annual Cycle ◽  
Yellow Sea ◽  
Bohai Sea ◽  
Biological Model ◽  
Model Parameters ◽  
The Bohai Sea ◽  
Northern Yellow Sea ◽  
Ocean Models ◽  
Adjoint Assimilation

One difficulty with coupled physical-biological ocean models is determining optimal values of poorly known model parameters. The variational adjoint assimilation method is a powerful tool for the automatic estimation of parameters. We used this method to incorporate remote-sensed chlorophyll-a data into a coupled physical-biological model developed for the Bohai Sea and the Northern Yellow Sea. A 3-D NPZD model of nutrients (N), phytoplankton (P), zooplankton (Z) and detritus (D) was coupled with a physical model, the Princeton Ocean Model. Sensitivity analysis was carried out to choose suitable control variables from the model parameters. Numerical twin experiments were then conducted to demonstrate whether the spatio-temporal resolutions of the observations were adequate for estimating values of the control variables. Finally, based on the success of the twin experiments, we included remote-sensed chlorophyll-a data in the NPZD model. With the adjoint assimilation of these chlorophyll-a data, the coupled model better describes spring and autumn phytoplankton blooms and the annual cycle of phytoplankton at the surface layer for the study area. The annual cycle of simulated surface nutrient concentrations also agreed well with field observations. The adjoint method greatly improves the modelling capability of coupled ocean models, helping us to better understand and model marine ecosystems.

Pathways of suspended sediments transported from the Yellow River mouth to the Bohai Sea and Yellow Sea

2020 ◽  
Vol 236 ◽  
pp. 106639 ◽  
Author(s):  
Xingmin Liu ◽  
Lulu Qiao ◽  
Yi Zhong ◽  
Xiuquan Wan ◽  
Wenjing Xue ◽  
...  
Keyword(s):  
Yellow Sea ◽  
Bohai Sea ◽  
Yellow River ◽  
River Mouth ◽  
Suspended Sediments ◽  
The Yellow River ◽  
The Bohai Sea ◽  
Yellow River Mouth

Nutrient sources in the Bohai Sea and Yellow Sea: results from seasonal sampling in 2018

2020 ◽  
Author(s):  
Shichao Tian ◽  
Birgit Gaye ◽  
Jianhui Tang ◽  
Yongming Luo ◽  
Tina Sanders ◽  
...  
Keyword(s):  
Yellow Sea ◽  
Bohai Sea ◽  
Yellow River ◽  
The Yellow Sea ◽  
Reactive Nitrogen ◽  
Nutrient Concentrations ◽  
The Yellow River ◽  
Isotopic Ratios ◽  
Nutrient Sources ◽  
The Bohai Sea

<p>The Bohai Sea and Yellow Sea are semi-enclosed basins strongly affected by human activities due to climate change and growing industries in China. Changes of hydrology, nutrient concentrations and sources and resulting ecosystem responses are therefore progressively intensifying during the last decades. In order to characterize nutrient sources and dynamics and to estimate the anthropogenic impact, we investigated nutrient concentrations and dual isotopes of nitrate in spring and summer 2018 in Bohai Sea and Yellow Sea. Furthermore, we sampled suspended matter and surface sediments and determined organic carbon, nitrogen and stable nitrogen isotopic ratios.</p><p>In spring, the water column was well mixed and the study area was mainly affected by the Yellow River diluted water and the Yellow Sea Warm Current water, which were the main nitrate sources. In summer, the water was stratified, and the Yellow River and Changjiang River diluted water supplied nutrients to an even larger region than in spring. During this season, the Yellow Sea Cold Water mass formed the bottom water of the Yellow Sea where nutrients became enriched. In contrast to other polluted marginal seas, the stable isotopic ratios of dissolved and particulate nitrogen are relatively low in the study area, which could be due to nutrient supply from the atmosphere or the open ocean. Using nitrogen isotopes, we developed a box model of reactive nitrogen for the Bohai Sea and quantified the input of atmospheric and riverine reactive nitrogen, submarine groundwater and water exchange with the Yellow Sea, constraining the budgets of reactive nitrogen combining mass fluxes with an isotopic balance. Including the isotopic balance improved the mass balance based only on nutrient concentrations.</p>

scholarly journals Satellite views of the seasonal and interannual variability of phytoplankton blooms in the eastern China seas over the past 14 yr (1998–2011)

2013 ◽  
Vol 10 (7) ◽  
pp. 4721-4739 ◽  
Author(s):  
X. He ◽  
Y. Bai ◽  
D. Pan ◽  
C.-T. A. Chen ◽  
Q. Cheng ◽  
...  
Keyword(s):  
Yellow Sea ◽  
Bohai Sea ◽  
Eastern China ◽  
The Yellow Sea ◽  
China Seas ◽  
Phytoplankton Blooms ◽  
Chl A ◽  
The Past ◽  
Eastern China Seas

Abstract. The eastern China seas are some of the largest marginal seas in the world, where high primary productivity and phytoplankton blooms are often observed. However, little is known about their systematic variation of phytoplankton blooms on large spatial and long temporal scales due to the difficulty of monitoring bloom events by field measurement. In this study, we investigated the seasonal and interannual variability and long-term changes in phytoplankton blooms in the eastern China seas using a 14 yr (1998–2011) time series of satellite ocean colour data. To ensure a proper satellite dataset to figure out the bloom events, we validated and corrected the satellite-derived chlorophyll concentration (chl a) using extensive in situ datasets from two large cruises. The correlation coefficients between the satellite retrieval data and the in situ chl a on the logarithmic scale were 0.85 and 0.72 for the SeaWiFS and Aqua/MODIS data, respectively. Although satellites generally overestimate the chl a, especially in highly turbid waters, both the in situ and satellite data show that the overestimation of satellite-derived chl a has an upper limit value (10 μg L−1), which can be used as a threshold for the identification of phytoplankton blooms to avoid the false blooms resulting from turbid waters. Taking 10 μg L−1 as the threshold, we present the spatial-temporal variability of phytoplankton blooms in the eastern China seas over the past 14 yr. Most blooms occur in the Changjiang Estuary and along the coasts of Zhejiang, with a maximal frequency of 20% (about 73 days per year). The coasts of the northern Yellow Sea and the Bohai Sea also have high-frequency blooms (up to 20%). The blooms show significant seasonal variation, with most occurring in spring (April–June) and summer (July–September). The study also revealed a doubling in bloom intensity in the Yellow Sea and Bohai Sea during the past 14 yr. The nutrient supply in the eastern China seas might be a major controlling factor in bloom variation. The time series in situ nutrient datasets show that both the nitrate and phosphate concentrations increased more than twofold between 1998 and 2005 in the Yellow Sea. This might be the reason for the doubling of the bloom intensity index in the Yellow Sea and Bohai Sea. In contrast, there has been no significant long-term increase or decrease in the Changjiang Estuary, which might be regulated by the Changjiang River discharge. These results offer a foundation for the study of the influence of phytoplankton blooms on the carbon flux estimation and biogeochemical processes in the eastern China seas.

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