Interpreting the effect of soil texture on transport and removal of nitrate-N in saline coastal tidal flats under steady-state flow condition

摘要: Abstract Tidal-flats play important roles in oceanic nitrogen (N) cycles. Particularly, N loss the tidal-flats depends on soil texture and yet dominant removal mechanism relation to is not clear. Therefore, objective of this study was investigate effect NO3−-N transport texturally contrasting western coast Korea [Gangwha (GH, silt) Saemangeum (SMG, loamy sand) sites]. To interpret experimental results, we compared time-course patterns disappearance during incubation under intertidal subtidal conditions breakthrough curves (BTCs) with a conservative tracer (Br−) miscible displacement experiment. Nitrate by denitrification negligible for SMG soils, but 1.6 2.3 mg N kg−1 day−1 GH respectively. The BTCs Br− were identical followed Gaussian distributions tidal-flats, while those obtained broad asymmetrical. Calculated Peclet number seawater matrix fitting CXTFIT model measured 45.03 4.93 indicating dominance advection over dispersion former, vice versa latter. From mass balance NO3−-N, nearly all added (38.8 mg) recovered effluents slight unaccounted-for portion (2.8 mg) system, possibility an intense off-shore discharge (leaching) from tidal-flats. In contrast, considerably large amount (27.0 mg) system one-third (13.5 mg) effluents, suggesting that dominates removal. Our results showed different depending characteristics should be predetermined site-specific management waste water loadings coastal systems.