Study About The Rule Of Gravel-sand Chemical Elements Leaching Simulation Test Of Ningxia Zhongwei Area

This paper aimed at the problems that the health issues of gravel-mulched field soils in the area of Zhongwei,Ningxia,simulation test method was used,the chemical elements composition and the leaching amount under different Supply water quantity conditions of the two gravels were observed.The leaching law of elements in four seasons within one year under the conditions of different supply water quantity was studied.The element accumulation of gravel soaking solution under dry-wet and freeze-thaw cycling conditions was observed,and the kinds and amount of the gravel leaching elements with the number of test cycles was analyzed.The following conclusions were obtained:(1)25 species and 23 species elements were composed by the green slate gravel and red feldspar quartz sandstone gravel respectively.In the simulation of local climate conditions,there were 16 species and 15 species(except H and O)leached by these two gravels,which contained 6 necessary major element N,K,Ca,Mg,P,S,2 trace elements Cl,Mn,2 beneficial elements Na and Si of plant growth elements,and 6 other elements such as C,Br and F.Among them,Ca and Cwere the 2 elements of leachinglargest amount,followed by Na,S and other elements.(2)The elements leaching amounts of these 2 kinds of gravel increased with simulation time increasing.The leaching quantity of various elements of the two kinds of sand and gravel showed a logarithmic growth trend with the increase of the amount of supplement water.In the same water-supply amountcondition,the total leaching elements amount of red feldspar quartz gravel was significantly higher than green slate gravel.(3)There were 13 species and 16 species in dry-wet alternate and freeze-thaw cycles solutions,respectively,wich contained 6 major elements N,Ca,S,K,Mg,P,1 trace elements Cl,Mn,2 beneficial elements Na,Si,and other 4 elements Ba,F,Br,C.Freeze-thaw cycles treatment solution also contained a very small amount of Mn,Mo,Cr elements.(4)The accumulation of major elements,trace elements,and beneficial elements increased with increasing of the number of test cycles(50 times),in both dry-wet alternate treatment and freeze-thaw cycles treatment solutions.Andthe ements acumulation of freeze-thaw cycles gravel solutions was larger than dry-wet alternate treatments significantly,but the elements accumulation of drying-weting alternate solution can not be ignored compared with freeze-thaw cycles.