Salinity decreases methane concentrations in Chinese lakes

Area of Science:

• Environmental Science
• Geochemistry
• Limnology

Background:

• Lakes are significant sources of atmospheric methane (CH4).
• Accurate assessment of CH4 emissions requires understanding environmental influences on lake water CH4 concentrations.
• Salinity is a critical, yet often overlooked, environmental factor in aquatic methane cycling.

Purpose of the Study:

• To investigate the influence of salinity on methane (CH4) concentrations in lake water.
• To compare CH4 concentrations between freshwater and saline lakes in the Tibetan Plateau and other regions of China.
• To provide insights for more accurate global CH4 emission estimations from lakes.

Main Methods:

• In-situ continuous measurements of CH4 concentration in Lake Keluke (freshwater) and Lake Tuosu (saline) from 2021-2023.
• Analysis of spatial and seasonal variations in CH4 concentrations.
• Comparative analysis of CH4 concentrations across 33 lakes (5 saline, 28 freshwater) representing diverse geographical regions.

Main Results:

• Methane (CH4) concentrations exhibited substantial spatial and seasonal variations in both studied lakes.
• CH4 concentrations were consistently higher in the freshwater Lake Keluke compared to the saline Lake Tuosu.
• Saline lakes across different regions showed significantly lower average CH4 concentrations (0.08 μmol/L) than freshwater lakes (1.25 μmol/L).

Conclusions:

• Salinity is a critical factor controlling CH4 concentrations in lake water, likely through microbial community shifts.
• Freshwater and saline lakes exhibit distinct CH4 emission profiles.
• The findings support differentiating lake types for improved global CH4 emission modeling.