| The karst area of Guizhou Province is one of the typical ecologically fragile areas in China due to its special geological background.The Caohai Wetland is developed from the accumulation of water in the carbonate-formed karst basin.It is the largest natural plateau freshwater lake in Guizhou Province and an important base for the study of the subtropical plateau wetland ecosystem in China,but the risk of water of heavy metals pollution has already appeared.However,there is currently no research on the source orientation of the metal pollution source from the Caohai wetland on the spatial axis.In this paper,from the vertical space interface,the "atmosphere-water body-sediment" and multi-environmental carriers are linked to study the metal pollution source of water,aiming to understand the change law of heavy metals pollution in the Caohai wetland and the status of water and metal pollution sources that the high background value of heavy metals and frequent under the double stress of human activities,to provides a scientific basis for the rational development of Caohai wetland ecosystem balance and water environment quality protection measures.In this paper,the overlying water and surface sediments of the Caohai were collected to study the law of sediment release of water heavy metals under different thermal and kinetic conditions,and the atmospheric sediment samples were collected by Moss Bag to explore the atmospheric and terrestrial sources of heavy metals of water environment,mainly heavy metals such as Cr,Cd,Pb,As,Cu,Zn,and Hg 7,using principal component analysis and correlation analysis to study pollution characteristics and sources,and pollution assessment by potential ecological hazards index method,the geoaccumulation index method,and the enrichment factor method made.There were some conclusions that were showed as follows on this paper.The results show that there are obvious differences in the atmospheric sedimentation fluxes of the elements in Caohai lake.The precipitation fluxes of Cu and Zn elements are much higher than those of the other elements and account for a large proportion of the total deposition,but Cd,Hg pollution is especially serious through three evaluation methods.The contents of heavy metals in other samples were found to be: overlying water <pore water <sediment.For water samples in wet season,the content of Zn and Cu is higher and the average Zn is 12.86 ?g·L-1,Cu is 4.02 ?g·L-1,while the content of Zn and As in dry season is the higher and average values are0.710 ?g·L-1 for Zn and 1.55 ?g·L-1 for As.The comparison shows that Zn and As are common intensity pollution elements in other water samples in dry season and wet season period.other elements have great difference,and there is no obvious rule.Compared with GB3838-2002 surface water environmental quality standard,Hg exceed the standard,others are in the range;There is no clear pollution characteristics of heavy metals in the surface sediments,in dry season the highest content of Zn and Cr were 279.40 mg·kg-1 and 161.13 mg·kg-1,respectively,which were slightly higher than the wet water period.The other elements were different,and there is no Cu pollution and Pb pollution level is the same as that in the dry and wet season,while the Hg and Cd are in serious pollution.By studying the change of heavy metal content in sediment under different thermal and kinetic conditions,it is found that 20 ? can be regarded as a turning point under the same conditions and different temperature oscillates at the same rotational speed.The results show that the pore water in the sediment will diffuse upward under certain conditions,which has a certain effect on the content of the overlying water.Through static release,it was found that the concentration of Hg and As increased gradually with the change of time,the elements of Cr,Cd,Pb,Zn showed a decreasing trend as a whole,and Cu did not change obviously,which indicated that the heavy metals in sediment were mainly originated from exogenous pollution.It was found that rainfall,waste water discharge and even the feces from bird habitat had a certain effect on the heavy metal content in Caohai wetland by collecting the soil surrounding the Caohai wetland.In the whole spatial vertical system,Hg are at high risk,while the atmospheric-sediment system finds that Cd is also seriously polluted,indicating that there is a certain transmission process of pollution in the space system. |
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