| Sandstone is used as soil cover material in Huanxiangshan area of Ningxia.The local characteristic crops such as jujube and wolfberry are planted.Sandstone material leaches into the soil under local rainfall,irrigation and freeze-thaw cycles.In this paper,two kinds of main compacted gravel(green slate and red sandstone)in Xiangshan area of Ningxia are studied.Through indoor leaching simulation test,the leaching release of two kinds of compacted gravel elements under different water supply conditions and different salinity conditions are observed.The element composition and content of two kinds of compacted gravel are analyzed,The leaching rules of two kinds of compacted gravel under different salinity conditions and different water supplement levels were explored..At the same time,the element leaching amount of the compacted gravel under the local brackish water and the freeze-thaw cycles with the participation of salt was observed,and the leaching element types and the leaching amount of the compacted gravel under different treatment conditions were analyzed and compared with the changes of the number of freeze-thaw cycles and water quality.The main conclusions are as follows:(1)Under the same conditions of temperature,salinity and other factors,the participation of water can promote the leaching of elements in compacted gravel.With the increase of water supplement,the leaching amount of each element increases,and the leaching amount of gravel element has a logarithmic function relationship with the amount of water supplement.The relationship between leaching amount of green slate elements and water replenishment amount is as follows:Y1=161.52 In(x)-767.99,the relationship between leaching amount of red sandstone elements and water replenishment amount is as follows:Y2=71.89 In(x)-330.7.(2)With the increase of salinity,the leaching amount of elements increases first and then decreases,and reaches the maximum at about 3g/l,then decreases gradually.when the salinity of salt solution is about 3g/l,the effect of salinity on the leaching of elements in gravel is the smallest,and then with the increase of salinity,its inhibition on the leaching of elements is the largest.The fitting equation shows that the leaching amount of elements in gravel has a cubic polynomial relationship with salinity.The relationship between element leaching and salinity of green slate is as follows:Y=104.3X3-1367.8X2+5705.6X-6334.8,the relationship between element leaching and salinity of red sandstone is as follows:Y=32.564X3-467.91X2+1919.2X-1568.8.(3)Among the influencing factors(water supply,temperature and salinity)affecting element leaching in Zhongwei area of Ningxia,the amount of water supply has the greatest impact on element leaching,followed by temperature and salinity again.the influence on the leaching amount of elements in Zhongwei area of Ningxia is as follows:water supply>temperature>salinity.(4)As the number of freeze-thaw cycles increases,the amount of element leaching increased with the same water supply,and the increase rate of 2g/L NaCl solution was the fastest.When the number of freeze-thaw cycles reached 150,new elements appeared in the leaching process,namely arsenic(As),copper(Cu),manganese(Mn)and titanium(Ti).Among them,the leaching amount of Cu element in different water quality treatments is NaCl Solution>WXS(local brackish water)>ZLS(distilled water);the leaching amount of Mn element in different water quality treatments is NaCl Solution>ZLS>WXS;the leaching amount of Ti element in different water quality treatments is NaCl Solution>WXS>ZLS;and the leaching amount of As element in different water quality treatments is WXS>ZLS>NaCl solution.(5)As the number of freeze-thaw cycles increases the cumulative leaching amount of various elements in ZLS treatment was higher than that in WXS treatment This may be due to the Relatively high salt concentration in brackish water,which resulted in lower osmotic pressure and weaken leaching release of elements. |
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