查看更多>>摘要：The release of internal phosphorus(P)is a key and complex process relative to a lake's nutrient levels.The P response to nitrogen input should be clarified to obtain better detail,especially with respect to the mediation role of iron(Fe)connecting nitrogen and P.A simulation study was done in batch vials con-taining sediment and overlying water collected from Lake Moshui—a shallow lake.Because of nitrate(NO3-)input,the abundances of Firmicutes and Proteobacteria at the phylum level increased,as did the abundances of Crenothrix,Sideroxydans,and Flavobacterium at the genus level.Moreover,nitrate input enhanced the proliferation of nitrate-reducing Fe(Ⅱ)oxidization bacteria and the activity of denitrifying enzyme in sediment,but decreased the concentrations of total phosphorus(TP),soluble reactive P,and enzymatically hydrolyzable P in the water phase.The suppressive effect of nitrate on P release was mainly attributed to the increase in Fe(Ⅲ)(hydr)oxides generated by Fe(Ⅱ)oxidation.With sequential extraction,two types of dominant iron fractions-easily reducible oxides and reducible oxides(Feoxi and Feox2,respectively)-seemed to contribute to the fixation of P largely in the sediment.In addition,more P is converted to Feox2,which is induced by the transformation of Feox1 to Feox2.Driven by nitrate,a higher content of P bound to Feox1 and Feox2 was observed after a 7-day incubation,indicating the potential function of the Fe(Ⅱ)oxidation process.The current study revealed that the P transformation is influ-enced by nitrate input from the angle of iron as the connecting bridge to better understand the geochemical cycle of P in the anoxic environment of lakes.
查看更多>>摘要：Hydromorphodynamic interactions with vegetation are a part of fluvial biomorphodynamics in actively meandering rivers.Using palynofacies and grain size from sub-urban to urban reaches across the river valley,the spatial patterns of organic matter behavior are examined in a 38 km reach of the Gomati River in Lucknow District,Uttar Pradesh,India.This is done to understand how they respond to the alteration,preservation,and degradation after getting transported and deposited in sediment.Thirteen surface sediment samples of the Gomati River floodplain were analyzed for palynofacies and grain size to ascertain its fate in this reach,which comprises the big picture for past human settlement The shifts in the proportions of palynofacies associations,Le.,phytoclasts,palynomorphs,and amorphous organic matter(AOM)along with grain size,are considered to visualize the depositional process.The CONISS duster analysis revealed four zones reflecting high degradation and alteration of palynofacies in the urban regime compared to the sub-urban reaches where the low interference with natural settings il-lustrates the low deterioration of palynofacies.The relation between grain size and palynofacies was obtained using Principal Component Analysis(PCA)to emphasize the correlation with palynofacies in the meandering fluvial system of the Gomati River.In the floodplain deposits,the behavior of palynofacies,allows for the distinction of the regional aspects of fluvial sediment disposition.The current study compares urban and sub-urban settlement premises of today's communities and contributes to the understanding of the growth,dispersal,and decline of earlier human settlements.
查看更多>>摘要：The current study deals with experiments on hydro-suction removal of cohesionless bed material from reservoirs.The primary focus lies in scrutinizing the scour profile and the volume of bed material removed through hydro-suction.A comprehensive record of 252 datasets was collected from experi-ments done on various combinations of governing parameters.The resultant equilibrium scour profile exhibited a symmetrical configuration resembling a semi-ellipsoidal shape.Notably,for the densimetric Forude number equal to or less than 5.8,a small central hump within the scour hole was seen.The investigation found that the optimal sediment removal efficiency was obtained when the C/D ratio was zero(where C is the suction inlet height and D is the suction pipe diameter)and with the highest densimetric Froude number.The sediment to water volume removal was highest in the initial few seconds,and reduced swiftly,followed by a subsequent smaller peak and gradually decreased to zero at equilibrium.Empirical equations for computing maximum scour depth,scour radius,and scour profile at equilibrium also were developed,which predict values within a commendable±10％error range.
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