Effects Of Plants In Caohai Wetland Of Guizhou On Phosphorus Distribution In Sediments

Due to historical reasons,Caohai had suffered from extensive drainage and drying,resulted in serious damage to its complete ecological structure.With the social and economic development of the WeiNing,the intensification of human activities had accelerated the degradation of the ecological functional structure of the Caohai wetlands.At present,the water quality of Caohai was in a state of light and moderate eutrophication.Phosphorus is one of the key limiting factors for eutrophication of wetland waters,exists in many different forms in water andsedimentwithdifferentmigrationcharacteristicsand bioavailability.It is essential to control eutrophication of wetlands water.In this paper,chemical continuous extraction method was used to extract and analyze different forms of phosphorus in Caohai sediments.According to the migration,transformation characteristics and bioavailability of phosphorus forms to evaluate the potential of secondary release of phosphorus from sediments.In this way,we can provide reasonable suggestions for the eutrophication control of Caohai.Wetland plants are an important component of the ecological function structure of Caohai wetland,which has an important influence on the geochemical behavior of phosphorus in water bodies and sediments.In this study,the field sample analysis and indoor contrast culture were used to study the phosphorus composition of water bodies and sediments under different plant conditions,and the correlation analysis of sedimentary physicochemical factors was used to discuss the effects of phosphorus migration and transformation in the sediments of Caohai.The main conclusions are as follows:?1?The wetland plant system had a good absorption effect on water nutrients,and it was beneficial to inhibit the growth of algae in water bodies while reduced the nitrogen and phosphorus levels in water bodies.Under different vegetation types,the average content of total phosphorus?TP?in the sediments of Caohai was 0.38±0.07 g·kg^-1.The profile characteristics reflected the pollution of Caohai sediments in recent years.The organic phosphorus?Or-p?in the sediments of Caohai was the main component of the extraction of phosphorus,and the content in the water depth area was higher than other areas prominent.Its accumulation was closely related to wetland plants and had a high potential for phosphorus release.Detrital calcium phosphorus?De-p?,closed storage phosphorus?Oc-p?and autogenous calcium phosphorus?Aca-p?are less than organic phosphorus.There was no obvious feature in spatial distribution,and it had little effect on eutrophication of Caohai.Exchanged phosphorus?Ex-p?,aluminum-phosphorus?Al-p?and iron-phosphorus?Fe-p?account for a small proportion of phosphorus forms in the sediments of Caohai.Its occurrence and transformation was obviously affected by sedimentation physical factors?pH,TN,SOC,etc.?,and has strong migration characteristics and bioavailability?2?There were different distributions of phosphorus content in different parts of reed in Caohai,showed typical bioaccumulation characteristics of Leaf total phosphorus>stem total phosphorus>root total phosphorus.The characteristics of phosphorus accumulation in different regions reflected the pollution in this area and it is recommended to reduce the proportion of phosphorus to water by regularly harvesting the reeds.The TP content in the rhizosphere sediments of reeds was0.69±0.18 g·kg^-1,which was higher than that of non-rhizosphere sediments.The TP accumulation characteristics of root sediments reflected a good phosphorus enrichment effect of plant growth on the surrounding environment.In terms of spatial distribution,the TP distribution characteristics of sediments reflected a good pollution interception effect of exogenous phosphorus in the lakeside belt of Caohai,and should pay attention to its ecological protection work.The order of phosphorus content in rhizosphere sediments of reeds was organic phosphorus?43.78%?>detrital calcium phosphate?29.50%?>autogenous calcium phosphorus?12.38%?>closed storage phosphorus?12.20%?>exchange state?1.75%?>aluminum phosphorus?0.27%?>iron phosphorus?0.13%?.The accumulation of Or-p was mainly due to the decay of reeds,and the content in the rhizosphere was higher than that in the non-rhizosphere.The accumulation of Aca-p was related to the sediment itself and had a significant positive correlation with sediment pH?P<0.05?.The content of Aca-p was gradually decreasing along the road to the lake.The content of Ex-p in rhizosphere sediments was higher than that in non-rhizosphere,and the content was gradually decreasing along the road to the lake.The migration and transformation were affected by multiple environmental factors.?3?In the 12-week internal contrast culture,wetland plant growth effectively promoted the pH of the overlying water,accelerated the low level of SRP interaction at the interface,and reduced the TP content of the water.Plant growth reduced sediment TP levels,indicated that plant growth had a good absorption effect on sediment nutrients,and the absorption effect of reeds was better than that of Scirpus Tabernaemontani.Plant growth significantly reduced the level of Act-p in sediments,there was a significant negative correlation with plant height?P<0.01?,and it was important for controlling the direct release of phosphorus in sediments;Plant growth showed a slight effect on Or-p content of sediment,and had no significant effect on Ina-p content of sediment.