Factors controlling nitrous oxide in the inner Pearl River Estuary, Northern South China Sea

Chemometrics coupling geographic information system (GIS) was applied to investigate the spatial distribution patterns of nitrous oxide in the water column, its relation with environmental factors and to identify spatial human impacts on local scales. N₂O concentrations in both the surface and bottom waters of the inner Pearl River Estuary had obvious variability along the Pearl River. The spatial variation in distribution of N₂O concentration in the inner Pearl River Estuary was influenced by freshwater discharge along salinity gradients, which highlights the effects of human impacts on N₂O emission rates. Principal component analysis recognized human impacts and their affected areas. The primary anthropogenic source in the area was domestic sewage. Cluster analysis further confirmed the results of principal component analysis. Moreover, GIS-based spatial analysis facilitated chemometrics.