Research On Water Purification Effect And Optimizing Allocation Technology Of Riparian Buffer Strips

Riparian buffer strips are in flooding-drying habitat crisscross area, which are affected by water and land ecological system at the same time. Its edge effect is obviously so that it has high social value, economic value and ecological value. Aim at the deteriorating trend of water pollution and the degeneration of ecological system of riparian buffer strips, this study uses all kinds of methods like field investigation, simulation experiment of slope buffer strips and aquatic plants simulation experiment. Community structure, water purification effect, transfer rules of nutrient substance enrichment and optimal allocation technology of riparian buffer strips are studied. The main purposes of this study are building vegetation ecological buffer zones whose function is water purification and which distributes in echelon and improving water purification function of water resource protection forest. It has important theoretical significance and practical value for protecting fresh water resource and land which human beings depend on. This paper’s main conclusions as follow:(1)At the continental riparian buffer strips of Mulan Paddock,the water pH value of birch pure forest changes to a larger extent, but mixed broadleaf-conifer forest has a less effect on the water pH value; mixed larch-birch forest has the best effect on removing COD in the water, the removal rate reaches98.27%;in sample plot6,the larch pure forest has the best effect on removing TP in the water, the removal rate reaches96.57%; in sample plot6,the larch pure forest has the best effect on removing PO43--P in the water, the removal rate reaches96.7%;mixed larch-birch forest has the best effect on removing TN in the water, the removal rate reaches58.41%;Each forest type has a very obvious effect on removing NO3--Nin the water. Among them, the final NO3--N concentration of sample plot1,sample plot2,sample plot5,sample plot6and sample plot7are all lower than the set value in experiment.(2) With planting the combination of small typha and iris wilsonii and the combination of scirpus tabernaemontani gmel and iris wilsonii, the water pH value is relatively small and is less than9. The combination of lythrum salicaria and iris wilsonii has the best effect on removing COD in the water,the removal rate reaches77.40%;the combination of scirpus tabernaemontani gmel and iris wilsonii has the best effect on removing TP in the water, the removal rate reaches88.98%;the combination of scirpus tabernaemontani gmel and iris wilsonii has the best effect on removing PO43--P in the water, the removal rate reaches92.39%;the combination of lythrum salicaria and iris wilsonii has the best effect on removing TN in the water, the removal rate reaches73.83%;compared to planting the combination of lythrum salicaria and iris wilsonii, planting the combination of scirpus tabernaemontani gmel and iris wilsonii and the combination of small typha and iris wilsonii makes NO3--N concentration of the water below the set value early. In general speaking, three kinds of different plants configuration all have a very obvious effect on removing NO3--N in the water.(3)The combination of larch and birch, lythrum salicaria and iris wilsonii has the best effect on enriching COD in the water, the removal rate reaches99.61%; thecombination of larch and birch, scirpus tabernaemontani gmel and iris wilsonii has the best effect on enriching TP in the water, the removal rate reaches99.44%; the combination of larch, scirpus tabernaemontani gmel and iris wilsonii has the best effect on enriching PO43--P in the water, the removal rate reaches99.75%; the combination of larch and birch, lythrum salicaria and iris wilsonii has the best effect on enriching TN in the water, the removal rate reaches89.12%.Terrestrial vegetation has the best effect on enriching NO3--N, and after passing the whole riparian buffer strips, N03--N concentration of all combinations reduce under the set value and the removal rate is relatively high.(4)The Removal Rate of Nutrient Substance-Width Model of riparian buffer strips is established:Y=-0.3218X2+8.4707X+22.524,and13.16m is determined as the narrowest of optimal removal effect by riparian buffer strips; The Density-Water Quality Model of riparian buffer strips is established:Y=1.925X1-160.045X2+3277.940X3+494.961X4-1875.013X5+1074.309,and1074plants/hm2is determined as the optimal density; the Slope-Water Quality Model of riparian buffer strips is established:Y=0.036X1-1.727X2-11.796X3-0.057X4+1.369X5+14.755,and14.8°is determined as the optimal slope.(5)This paper sets3kinds of riparian buffer strips vegetation as following:larix gmelini pilg and birch, lythrum salicaria and iris wilsonii; Chinese pine and larix gmelini pilg, scirpus tabernaemontani gmel and iris wilsonii; larix gmelini pilg, scirpus tabernaemontani gmel and iris wilsonii. And these combinations are arranged reasonably.