Research On The Effect Of Plant Calcification On Phosphorus Cycle In Water Body

In the present study,uncalcified(UCa-CF)submerged plant Ceratophyllum demersum L.and calcified(Ca-CF)submerged plant Potamogeton crispus L.were chosen as the research objects to study the effects of plant calcification on phosphorus cycle in water by adding different concentration of phosphorus and calcium ions in the overlaying water.Two experiments were inclued.The "water-submerged plant" system was constructed in the light incubator to study the effects of phosphorus and calcium addition on the phosphorus enrichment capacity of plants in water.The "supernatant water-submerged plant-sediment" system was constructed in microcosmic control system to study the different phosphorus forms in overlting water,interstitial water,sediment and plant phosphorus and phosphors migration and transformation under different phosphorus and calcium concentrations.The main conclusions are as the followings:(1)In the two systems,P.crispus L.and C.demersum L.could effectively reduce the concentration of total phosphorus(TP),total soluble phosphorus(DTP)and soluble reactive phosphorus(SRP)in the overlying water.In the light incubator experiment,the phosphorus content of the solution with P.crispus L.showed higher decrease amplitude than that with C.demersum L.,while the phosphorus content of the solution with P.crispus L.showed lower decrease amplitude than that with C.demersum L.in the microcosmic control system.(2)In the microcosmic control experiment,the contents of TP and PP in the interstitial water decreased in the P.crispus L.system,while that in the C.demersum L.system increased.During the experiment,adding phosphorus in the P.crispus L.system could increase TP in the sediment,because NaOH-P(Fe/Al-P)increased,while in the C.demersum L.system,the HCI-P in the sediment increased,but NaOH-P(Fe/Al-P)decreased,which results in the TP decreased.(3)In the light incubator experiment and microcosmic control experiment,phosphorus concentration significantly affected plant phosphorus content(dry weight)of both P.crispus L.and C.demersum L.,phosphorus concentration and calcium concentration significantly affected ash total phosphorus and the fraction of ash total phosphorus(including water-soluble phosphorus,organic phosphorus and Ca-bound P)of both P.crispus L.and C.demersum L.For P.crispus L.,the ash total phosphorus in the two experiments were the highest phosphorus under high phosphorus and high calcium(2-100),while for C.demersum L.,ash total phosphorus in the light incubator experiment was the highest under medium phosphorus and low calcium(0.2-0),and that in the microcosmic control experiment was the highest under high phosphorus and high calcium(2-100).(4)The phosphorus from the overlying water(including interstitial water)could be concentrated by both P.crispus L.and C.demersum L.in three ways: absorbtion,adsorption and Ca-P coprecipitation.During the light incubator experiment,for P.crispus L.water phosphorus and Ca-bound P were all the highest level under high phosphorus and high calcium(2-100),organic phosphorus was under high phosphorus and low calcium(2-0),while for C.demersum L.water-soluble phosphorus and Ca-bound P was the highest under medium phosphorus and low calcium(0.2-0),organic phosphorus was under high phosphorus and high calcium(2-100).However,in the microcosmic control experiments,for both P.crispus L.and C.demersum L.Ca-bound P was the highest under high phosphorus and high calcium(2-100).(5)In terms of the decline of phosphorus in water,P.crispus L.showed higher capability of phosphorus enrichment during the experiment of light incubator,while C.demersum L.was more capable of phosphorus enrichment in water during the experiment of microcosmic control.From the calcium phosphorus of ash phosphorus,the P.crispus L.showed higher abilities of phosphorus enrichment than C.demersum L.during the experiment of light incubator and the experiment of microcosmic control.