Sedimentary Records And Environmental Evolution Of Sediments In Xidahai Lake

Taking the sediments column of the Xidahai Lake as the research object,application of 210 Pb to build the time sequence, by experimental analyzing the indexes of the particle size index, nutritional index(organic matter, total nitrogen, total phosphorus and forms of phosphorus), metal index, and combined with the history of literature records in basin of the Xidahai Lake, discussed the sediments and sedimentary records of environmental evolution history of the Xidahai Lake.The average value of organic sediments(OM), total nitrogen(TN) and total phosphorus(TP) were 1.637%, 0.270%, 1115.01mg·kg-1 in the Xidahai Lake, Ca-P was the main component of TP. The ratio of C/N in sediment showed that organic matter were mainly from aquatic organisms. The clay and fine silt was dominated by the sediment particle size. The average value of Al, Ba, CA, Cr, Cu, Fe, K, Li, Mg, Mn, Na,Ni, Sr, Cd, Pb and Zn were 75885.94mg·kg-1, 527.29mg·kg-1, 48348.35mg·kg-1,89.29mg·kg-1, 27.40mg·kg-1, 38600.65mg·kg-1, 25234.08mg·kg-1, 43.07mg·kg-1,26062.32mg·kg-1, 885.61mg·kg-1, 22984.71mg·kg-1, 44.22mg·kg-1, 367.88mg·kg-1,0.30mg·kg-1, 25.99mg·kg-1, 102.87mg·kg-1in the Xidahai Lake. The average value of Cr,Cu, Ni, Cd, Pb, Zn were exceeded the background value of Songnen plain soil, and especially Cd, which the average was 4 times in the background value.The contents of Ca-P, IP and OM were changed less, the contents of Fe/Al-P, OP,TP and TN were fluctuated more, the contents of Cd, Cr, Mg and Ni were increase in the upper part from 1843 to 1970; The contents of Ca-P, IP, TP, Al, Ca, Cr, Cu, Fe, Li,Mg, Mn were decreased with the decrease of the depth, the contents of Ba, Na was increased, the contents of Fe/Al-P, OP, OM were decreased first and then increased from1970 to 1996; The average content was the highest in the three stages of Fe/Al-P, OP and OM, the contents of Cd, Pb were increased from 1996 to 2009. The sediment core nutrients pollution sources were mainly from industrial wastewater, sewage and the loss of fertilizers in Xidahai Lake.Based on the organic index and organic nitrogen pollution situation of thesediments in Xidahai Lake were evaluated. The organic index of the Xidahai Lake sediment was clean and relatively clean category, and the organic nitrogen of the Xidahai Lake sediment was pollution. And based on Geo accumulation index method and potential ecological risk index method of the sediments to 6 kinds heavy metals of Cr, Cu, Ni, Cd, Pb and Zn in Xidahai Lake were evaluated. The heavy metal of Cd belonged to the partial moderate pollution, Cr, Zn, Ni, Cu, which belonged to light pollution, Pb elements was without pollution. Cr, Cu, Ni, Pb and Zn were minor ecological hazards, Cd belonged to the strong-strong ecological hazard category, the comprehensive potential ecological risk of the Xidahai Lake sediments belonged to the strong ecological risk level.