Temporal and spatial variability of ground level atmospheric methane concentrations in the Ebro River Delta

With regard to seasonal variability, autumn transects showed the highest mean values for atmospheric CH4 (2.466 ppm) when dead rice straw is mixed with the sediment, and weed growth is prevented. Spring and summer measurements gave the highest mean CH4 values at dawn (1.897-3.544 ppm), whereas autumn and winter produced the mean values after sunset (2.148-2.930 ppm). Spatial differences were accounted for by proximity to urban areas, presence of shallow water storage structures, and distance to seawater.