Distribution Of Inorganic Sulfur Fractions And Their Influences On Nitrogen Removal From Marsh Sediments In Fuzhou Reach Of The Min River

Nitrogen effective removal from marsh ecosystems under the background of increased nitrogen load has become a hot spot of academic.Different forms of sulfur can affect the ability of nitrogen removal in marsh sediments by impacting the nitrification,denitrification,anaerobic ammonium oxidation,and dissimilatory nitrate reduction to ammonium.The Min River Basin is located the areas with more acid deposition in china.Affected by the acid deposition and estuary hydrodynamics,the Distributionand cycle process of sulfur in marsh sediments are extremely complex.At present,the related studies on the spatial variations of sulfur in marshes along the Min River are still weak,and the effectes of sulfur on the ability of nitrogen removal has been rarely reported.In this paper,the marshes in Fuzhou reach of the Min River were studied based on the method of field sampling and indoor simulation experiments.The distribution of inorganic sulfur fractions and its main influencing factors in sediments were discussed.Meanwhile,the influence of sulfur forms and levels on the ability of nitrogen removal were clarified.Results were as follows:ⅰ)The overall performances of H₂O-S、Adsorbed-S、HCl-Soluble-S and TIS contents in the marshes in Fuzhou reach of the Min River were estuary>urban reach>freshwater reach,and the HCl-Volatile-S was urban reach>freshwater reach>estuary.The proportion of Adsorbed-S,HCl-Soluble-S and HCl-Volatile-S in the TIS content decreased from the Shuikou Power Station to the estuary,while the proportion of H₂O-S increased.H₂O-S,Adsorbed-S and HCl-Soluble-S were higher in salt marsh,aquaculture farm and silty beach,and lower in scrub swamp;while HCl-Volatile-S was higher in scrub swamp and lower in sandy beach.ⅱ)The environmental factors that affect the distribution of inorganic sulfur in sediments were different.Among them,sediment grain composition,electrical conductivity（EC）and pH showed significant effects on sulfur distribution.Compared with other estuary in china,the inorganic sulfur contents of marsh sediments in Min River were generally at a higher level,which may be mainly related to the higher SO₄^2-deposition level and favorable hydrothermal conditions.ⅲ)The effects of sulfate and sulfide additions on removal of NO₃^--N in sediments were not obvious,which may be mainly related to the dominant of heterotrophic denitrification in denitrification.Sulfate additions reduced the ability of NH₄⁺-N removal in sediments under low nitrogen loading,and increased the ability under high nitrogen loading,but had barely effect on NH₄⁺-N removal without nitrogen loading,which may be related to the promoting of sulfate on anammox.Sulfide additions can promote the removal of NH₄⁺-N,which may be mainly due to the enhanced bioavailability of iron by sulfide.The influence of sulfate and sulfide additions on NO₃^--N removal roughly lasted for 3-5 d,while on NH₄⁺-N removal mainly concentrated in the first 3 d.ⅳ)Different sulfate addition levels promoted the removal of NO₃^--N in sediments,but the differences among these levels were not significant,which may be mainly related to the preferential utilization of organic matter in the process of nitrate dissimilatory reduction process.Low level sulfate additions can reduce the overall ability of NH₄⁺-N removal in sediments,but with the increase of sulfate addition levels,it can improve the ability of NH₄⁺-N removal,which may be mainly due to the promotion of sulfate on anammox.Different levels of sulfide addition also promoted the ability of NO₃^--N removal from sediments,but the difference between the input levels was not significant,which may be caused by the preferential utilization of organic matter during the heterotrophic respiration of denitrifying microorganisms.Different levels of sulfide addition can promote the removal of NH₄⁺-N from sediments,and the ability of NH₄⁺-N removal increased with the increase of sulfide and nitrogen addition levels,which may be related to the inhibition on organic nitrogen mineralization and the promotion on anammox by sulfide.This paper found that,the inorganic sulfur contents in the mash sediments of the Fuzhou reach of Min River（especially the freshwater reach）may further increase with the influence of SO₄^2-deposition.And the increase of the inorganic sulfur contents may improve the ability of nitrogen removal in mashes in Fuzhou each of the Min River by inhibit organic nitrogen mineralization and promote anammox under the background of enhanced nitrogen load.