| Phosphorus(P) is a vital element and its cycling in all sphere layers is achieved by the interaction between particulate matters and water among earth-river-sea, which is significant to keep the balance of river-sea ecosystem, and particulate matters in the waters have very important influences for transfer, transformation and end result of nutrient element phosphorus. In this paper, surface sediments from the middle and lower reaches of the Yellow River and shallow sea of Bohai Sea were studied from following three parts:①The contents and their distribution characteristics of totle phosphorus(TP), inorganic phosphorus(IP), organic phosphorus(OP), totle nitrogen(TN), totle carbon(TC) and all kinds of phosphorus forms were investigated in the sediments, and the relativity between their contents and grain sizes was analyzed; The contents of potential bioavailable phosphorus(BP) in the sediments were estimated, based on the differences of various P forms'properties;②P adsorption/desorption on sediments were researched. The results have shown that:1 The researches of TP, all foms phosphorus,TN, TC and BP in the sediments from the Yellow River and shallow sea of the Bohai Sea(1) The contents of TP,IP,OP in all samples were analyzed by using SMT method from the Standards of Measurements and Testing Programme of the European Commission, and the results showed that the contents of TP in the sediments ranged from 656.54 mg·kg-1 to 852.63 mg·kg-1,the average was 725.49 mg·kg-1,and IP was its dominant portion, accounted for more than 85% of TP,the contents of OP were lower;The mean of TC and TN was 61.12 g·kg-1 and 167.43 mg·kg-1, respectively. Their content distributions changed with the sampling sites. The maximum values of TP,IP,OP and TN all appeared in the shallow sea of the Bohai Sea near the Yellow River estuary.(2) Seven forms of P in sediments were investigated by using the improved seven-step sequential extraction method and distinguished as following: exchangeable+loosely bound P(Ex-P), aluminum-bound P(Al-P), iron-bound P(Fe-P), obstinate-bound P(Obs-P), anthigenic+biogenic apatite+calcium carbonate-bound P(Ca-P), Detrital apatite+other remaining inorganic P (De-P), organic P(OP). In all samples with different particle sizes, De-P and Ca-P were the major components and their contents ranged from 135.35 to 399.26 mg·kg-1 and from 63.35 to 142.54 mg·kg-1, respectively, both of them occupied about 88% of TP; OP contens ranged from 6.17 to 60.65 mg·kg-1 and was 1.52% 14.27% of TP; the mean of Ex-P, Al-P and Fe-P was 8.60 mg·kg-1, 12.95 mg·kg-1 and 6.17 mg·kg-1, respectively and all of them were about 5.27% of TP; Obs-P contents were the lowest in all form P, the average was 1.18 mg·kg-1, about 0.31% of TP; The maximum contents of Ex-P, Al-P, Fe-P, De-P and OP were appeared in sediments of the shallow sea of the Bohai Sea and the maximum value of Ca-P contents was appeared at Jinan sediment.(3) The content distribution of various form P in studied sediments correlated with the grain size and the sampling sites directly. The relations between various form P of one kind of sediment and grain sizes and between one form P of different sediments and grain sizes were different, for example, the Ex-P contents in sediments of Lamawan and Huayuankou reduced with grain size minishing and in the other sediments were opposite. The positive correlation between the contents of De-P and TP was very remarkable, so De-P was the major contributor to TP.(4) In all studied samples, the contents of potential BP were at least about 6.09% 23.61% of TP. Based on the quantity of paticulates transported from the Yellow River to the Bohai Sea and the above results, the amount of potential BP was estimated.2 Research of P adsorption/desorption on sediments from the Yellow River and the shallow sea of the Bohai SeaThe P adsorption kinetics and its influence factors, adsorption isotherm and the influence of pH on adsorption isotherm and desorption kinetics on surfacial sediments from the Yellow River and the shallow sea of the Bohai Sea were researched and the results indicated that:(1) The adsorption of sediments to P in their overlying water was faster in 0 8 h, slower in 8 48 h and after 48 h was basically balanceable, but adsorption amount of P on various sediments were different. The initial P concentration and sediment concentration had direct impacts on P adsorption.(2) In natural waters was fastest in 0.5 h and the release rate gradually decreased with increasing of time. The release rate of P on sediments saturated by water of high P concentration was also low.(3) The adsorption isotherms of sediments to P indicated that isotherms for P sorption were well fitted to linear equation and Freundlich equation, as well as Langmuir equation, not fitted to Temkim equation, but the change tendency of experiment data fitted by Temkim equation were well fitted index equation and the relativities were very remarkable. Different pH values had different impacts on P adsoption isotherms. When equilibrium quality concentrations were the same, the maximum and minimum amounts of adsoption to P were appeared at pH = 7.0 and pH = 9.0, respectively, except Sanmenxia or Huayuankou sediments.(4) The correlation between the adsorption amount of sediments to P and initial P concentration had good linear relationship when P concentration in the overlying water was very low. According to the linear equation, adsoption-desorption equilibrium concentrations(EPC0 value) of different sediments to P were found and ranged from 0.001 mg·L-1 to 0.018 mg·L-1, which were all higher than P concentrations in waters, so the sediments had the trend of releasing P to overlying waters. |
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