When river meets ocean: distribution and conversion of suspended organic particles in a Sundarbans mangrove river-estuary system, Bangladesh

Global carbon cycle has received extensive attention,among which the river-estuary system is one of the important links connecting the carbon cycle between land and ocean.In this paper,the distribution and control factors of particulate organic carbon(POC)were studied by using the data of organic carbon contents and its carbon isotopic composition(δ13C)in the mainstream and estuary of Passur River in the Sundarbans area,combined with the hydrological and biological data measured by CTD.The results show that POC content ranged from 0.263 mg/L to 9.292 mg/L,and the POC content in the river section(averaged 4.129 mg/L)was significantly higher than that in the estuary area(averaged 0.858 mg/L).Two distinct stages of POC transport from land to sea in the Sundarbans area were identified.The first stage occurred in the river section,where POC distribution was mainly controlled by the dynamic process of runoff and the organic carbon was mainly terrestrial source.The second stage occurred during estuarine mixing,where the POC distribution was mainly controlled by the mixing process of seawater and freshwater.The source of POC was predominantly marine and exhibiting vertical differences.The surface and middle layers were primarily influenced by marine sources,while the bottom layer was jointly controlled by terrestrial and marine sources of organic carbon.These findings are of great significance for understanding the carbon cycle in such a large mangrove ecosystem like the Sundarbans mangrove.

Timely mental health services contribute to the containment of COVID-19 pandemic in China

The COVID-19 pandemic is the most severe public health crisis in the 21st century.The pandemic not only posed great challenges to people's physical health but also induced wide-ranging impacts on mental health of infected and suspected patients,frontline healthcare workers,and the general public whose normal life was disrupted by the pandemic.In this commentary,we outline the initiatives and coordinated efforts on providing timely mental health services after the pandemic outbreak in China,including understanding the mental health impact of COVID-19,prioritizing and coordinating mental health services along with medical services in the efforts to contain the pandemic,initiating and implementing specific measures to improve mental wellbeing of frontline healthcare workers,and increasing the accessibility of mental health services to the general public.Theses services,along with other coordinated efforts,contribute to the containment of COVID-19 pandemic in China and could be valuable for other countries to take proactive measures to mitigate the mental health impacts of the pandemic now and in the future.