Nitrate sources and transformation pathways in salt-affected agricultural ditches: biogeochemical responses along contrasting salinity gradients

Agricultural nitrate pollution, largely associated with high-intensity fertilizer application and untreated or insufficiently treated waste inputs, has become a major driver of water quality degradation worldwide. Agricultural ditches, as key recipients of surface runoff and lateral seepage, function as both transport conduits and biogeochemical hotspots for nitrogen transformation. In salt-affected ditches, high nitrogen inputs and salinity can interact to enhance nitrate accumulation and mobil