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Fate of methane in the Hudson River and Estuary
Author(s) -
Angelis Marie A.,
Scranton Mary I.
Publication year - 1993
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/93gb01636
Subject(s) - estuary , flux (metallurgy) , brackish water , salinity , atmosphere (unit) , sink (geography) , seawater , methane , anaerobic oxidation of methane , environmental science , environmental chemistry , hydrology (agriculture) , water column , oceanography , chemistry , geology , ecology , biology , geotechnical engineering , organic chemistry , physics , cartography , geography , thermodynamics
Methane (CH 4 ) concentrations and oxidation rates were measured throughout the Hudson River Estuary in March and August of 1991. Methane concentrations ranged from 50 to 940 nM and were supersaturated with respect to the atmosphere along the entire length of the river, with generally higher CH 4 values in the lower, saline portion of the estuary. A seasonally averaged diffusive flux to the atmosphere from the Hudson River was estimated to be 5.6 mg CH 4 m −2 d −1 , corresponding to an annual flux of 0.76 × 10 9 g CH 4 . The Hudson River Estuary also releases approximately 0.2 × 10 9 g CH 4 annually to nearshore marine waters. Diffusive flux across the air/river interface was the dominant removal mechanism for Hudson River CH 4 in March. In August, CH 4 oxidation was the dominant CH 4 sink in freshwater and brackish (<6‰) sections of the river, removing up to 70% of ambient CH 4 per day compared to maximum daily removal rates of 13% in March. Thus methane oxidation can play a major role in limiting releases of CH 4 to the atmosphere from rivers and other freshwater environments. Methane oxidation activity decreased rapidly as salinity increased, with less than 2% of ambient CH 4 being oxidized per day at salinities greater than 25‰. Addition of NaCl or seawater to freshwater samples resulted in comparable inhibition of methanotrophic activity. Budget calculations showed that flux to the atmosphere and CH 4 oxidation in March removed less water column CH 4 than was supplied to the Hudson River over its entire length. In August, however, CH 4 removal approximately equaled CH 4 supply with the result that there was no net accumulation of CH 4 over the length of the river.