| Due to the global warming and the degree of industrialization,wetland area has been declining.Liaohekou wetland is facing severe water shortage problem.At the same time,the groundwater supply condition is poor and the natural precipitation is not enough.The papermaking plant in the wetland is distributed along the river,wastewater flows through wetlands,and the waste water is large and the wetland wastewater is inevitable.In order to study the changes of soil properties in different soil layers and different growth stages,the migration characteristics of each index in wetland soil under long-term wastewater irrigation were analyzed.Simulation of natural reed wetland in Liaohe estuary using pilot plant,the papermaking wastewater CODcr concentration was 50mg·L-1,175mg·L-1,300mg·L-1,respectively,in different growth stages(seedling stage,leaf stage,jointing stage,heading stage and maturity stage)for irrigation,In 2009,the soil bulk density,porosity,organic matter,total nitrogen,total phosphorus and heavy metals content of the basal value,from 2009-2015,were irrigated every year,after long-term irrigation in 2015 after the determination of soil bulk density,porosity,organic matter,total nitrogen,total phosphorus and heavy metals content,ratio analysis of the content in 2009-2015.The main results are as follows:(1)After long-term irrigation,papermaking wastewater with different mass concentration,the bulk density decreases with the increase of soil depth.With the increase of soil depth,porosity decreases continuously.After long-term irrigation,different concentrations of papermaking wastewater,soil bulk density change trend with the increasing concentration of wastewater irrigation quality,soil bulk density gradually decreased.The porosity of the soil pores in the same concentration of papermaking wastewater decreased with the increase of soil depth,and the porosity decreased gradually,and the porosity reached the maximum in the 0-5cm soil layer.When the mass concentration was 300mg·L-1,the soil porosity changed the largest,and the change in 175mg·L-1 was the smallest.(2)After a long period of irrigation of different concentrations of paper wastewater,the content of organic matter in soil and the change of soil organic matter content in the soil surface was 5.01%.On the contrary,the growth rate of soil organic matter was 1.88%.At different growth stages of reed,the concentration of soil organic matter in the 0-5 cm soil layer was 3.97%at the concentration of 300mg·L-1.When the reed was in the leaf stage,when the mass concentration was 50mg·L-1,the growth rate of organic matter content in 0-5cm soil layer was 3.62%.The flowering stage,when soil organic matter content in the accumulation of organic matter,the reed quantity is less,so that a large number of organic matter accumulation in soil.(3)After a long period of irrigation with different mass concentration of papermaking wastewater,the maximum content of total phosphorus in soil in 0-5cm soil layer was 0.75gkg-1 The mass concentration of 300mg·L-1 was the highest in the treatment of total phosphorus,and the concentration of was the highest in the total concentration of 50mg·L-1.The content of total nitrogen in soil with the growth period was as follows:emergence stage>heading flowering stage>leaf stage>mature stage>rapid growth period.The variation of total nitrogen in soil is different from the concentration of irrigation,but there is no good rule to follow,but with the increase of soil depth,the change of total nitrogen.(4)After a long period of irrigation with different mass concentration of papermaking wastewater,the content of Pb in soil was 62.39mg·kg-1,and the content of 5-10cm was the lowest in the 40-60cm soil layer,which was 45.63mg·kg-1.The results showed that the Pb content in the upper layer soil was higher than that in the bottom layer.The reason was that the reed was less absorbed to the surface,and a large amount of lead ions were accumulated on the surface.The results showed that with the increase of wastewater irrigation time,the content of Pb in soil was increased,which led to the increase of lead ion.The minimum copper content in bottom soil was 12.53mg·kg-1,the copper ions in wastewater due to soil particle adsorption,a large number of copper ion concentration in the upper soil;cadmium content in soil did not change,a large number of cadmium ion concentration in the middle and bottom soil,cadmium content in surface soil is relatively small.The change of the surface cadmium ion was 2.00mg·kg-1.A large amount of chromium ion concentration in the soil surface was 53.76mg·kg-1,indicating that the reed of the surface soil in the absorption of chromium ions less.The content of manganese ion in the upper layer soil was significantly higher than that in the bottom soil,which indicated that after the wastewater was irrigated,the absorption of manganese ions by Reed was weak.The variation of soil manganese ion distribution in different soil layers,and the lower the distribution of more in the content of zinc;no good regularity in different soil layers,that is not the bottom or surface,the zinc ion content is bigger or smaller,the soil zinc ion variation distribution in different soil layer.And with the increase of soil depth,the change gradually decreased.(5)In different growth period of reed irrigation with different concentration of papermaking wastewater,soil content of lead ions at the concentration of 300mg·L-1 treatment,the content of lead ions,the concentration of 50mg·L-1,Pb content in soil minimum.The highest content of lead ion in 5-10cm soil layer was 62.39mg·kg-1.The distribution of copper ions in soil layers was similar.In the 5-10cm soil layer,the maximum content of copper ion was 59.49mg·kg-1,and in the 40-60cm soil layer,the content of copper ion was 45.28mg·kg-1.The change of copper ion in the mature soil was the largest,which indicated that the reed was the weak absorption of copper ions in the soil after irrigation.Soil cadmium ion in the 0-5cm soil layer,the highest concentration of 300mg·L-1 treatment.The change of cadmium ion concentration was the highest at the concentration of 300mg·L-1,and the change of 50mg·L-1 was the least.The content of chromium in soil was highest in 0-5cm soil layer.The greater the concentration of irrigation wastewater,the more the content of chromium ions in the soil.The change trend of chromium ion with the growth period of Reed was the mature stage>heading flowering stage>jointing stage>leaf stage>seedling stage.The content of manganese ion in the 0-10cm soil layer was the highest in the 40-60cm soil layer when the concentration of manganese ions in the soil was treated with 300mg·L-1.The change of manganese ion content was similar to that of manganese ion.With the increase of irrigation quality,the content of zinc ion in soil increased.The variation regularity of soil zinc ion with the change of long-term was the mature stage>jointing stage>heading flowering stage>leaf stage>seedling stage.There was a significant correlation between the water quality and the chemical and physical properties of the pulp. |
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