| Aha Reservoir is a karst plateau reservoir,which belongs to geochemical sensitive and ecologically fragile karst carbonate area.It is affected by factors such as unique climate,soil parent material,topography and human activities,the sediment at the bottom of the reservoir is a large amount of siltation,which becomes the main accumulation area of reservoir nutrient,heavy metal and organic pollutants,which would cause secondary pollution to overlying water.Sediment management is one of the important issues to be solved urgently,among which environmental dredging is a cost-effective and thoro?gh method.The utilization of resources is the main use direction of the Aha reservoir.In this study,the physical and chemical properties and heavy metal pollution characteristics of the Aha reservoir were evaluated by "CJ/T 340-2011 green soil planting" and "national soil nutrient content grading standard" by field investigation and laboratory analysis.And the dredged sediment was used in the planting experiment of horticultural plants to explore the effect of horticultural plant cultivation and the influence of horticultural plants on growth matrices.With a view to the Aha reservoir and similar karst mountain lake pollution remediation project to provide reference.The results shows that:(1)As a result of long-term siltation at the bottom of the lake,the reservoir sediment had a large amount of mud,high water content and contained a variety of useful,harmful components.The original sediment and dredged sediment of Aha Reservoir were neutral to weakly alkaline,pH were 7.49 and 7.80,and the bulk density,porosity and clay content were 1.65 g/cm3,1.55 g/cm3,36.08%,32.50% and 30.2%,38%.The contents of organic matter,total nitrogen,available nitrogen,available phosphorus and available potassium in the original sediment and dredged sediment were 92.25 g/kg,3.35 g/kg,312.50 mg/kg,27.48 mg/kg,145.64 mg/kg and 116.42 g/kg,2.50g/kg,110.55 mg/kg,42.44 mg/kg,195.78 mg/kg,reference to the "national soil nutrient content grading standards",Aha reservoir sediment contents of nutrient reached a high and above level,and all in line with "CJ/T 340-2011 green planting soil" standard.The content of medium and trace elements were all very abundant.The contents of As,Cr,Pb,Cd,Hg,Zn,Cu,Fe,Mn in the original sediment and dredged sediment were 26.68,104.86,75.87,1.12,0.27,164.65,59.53,62443.37,1931.05 mg/kg and 0.28,109.47,109.83,1.12,0.21,228.24,76.71,101488.13,2804.68 mg/kg,which have exceeded the surface value of sediments in Guizhou and the national mean value of the sediment which indicating that Aha reservoir sediment heavy metals content have accumulated.The Nemerow pollution index of heavy metals were 0.84,0.91,which were still in a clean level,and Potential Risk index were159.52,163.13,all of which were moderate risk.It can be seen,Aha reservoir sediment porosity was low and the texture was sticky.If the sediment is directly used as the growth substrate,it has the disadvantage to crack after drying,which is not conducive to the normal growth of most plants.At the same time,there was a risk of heavy metal pollution in the sediment,while avoiding the harmful substance entering the food chain,it also gets the resource utilization.(2)Dredged sediment was rich in nutrients and can be used as a growth substrate to improve plant growth after soil improvement.According to the results of pot experiment,the best substrate for the Matthiola incana(L.)R.Br.was the sediment: lava: Perlite: mushroom residue: peat: sawdust: organic fertilizer=10%: 20%: 10%: 15%: 10%:5%: 30%,the plant height,fresh weight,dry weight,nitrogen,phosphorus and potassium accumulation of the plant were 19.25 cm,31.11 g/pots,3.33 g/pots,131.83 g/pots,16.56 g/pots and 159.76 g/pots higher than those of CK at harvest;what's more,In Oxalis triangularis,Tagetes patula L.,Lolium perenne L.planting matrix,Through the two factor analysis of variance,the growth of Tagetes patula L.was the best,and the best treatment was sediment:Perlite: sawdust: mushroom residue: tea garden soil =70%: 10%: 10%: 10%: 0%.In addition,4 kinds of horticultural plants were planted in the sediment matrix with Cd content exceeding the standard,but the content of Cd in the plants were 0.21~1.04 mg/kg,which was within the normal content range of the normal plants.(3)After planting horticultural plants,the nutrient content of the substrate decreased to a certain extent,theorganic matter,the available N,the available K,the available P of which were 35.00~55.55 g/kg,71.31~213.92mg/kg,95.24~667.63 mg/kg,14.07~134.22 mg/kg respectively.At the same time,pH,EC and Cd were 6.81~7.69,0.50~1.01 ms/cm,0.21~1.04 mg/kg respectively,which still meet the green planting standards,may consider re-use. |
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