【作者】 刘昕；

【导师】 佟金；

【作者基本信息】 吉林大学 ， 农业机械化工程， 2017， 博士

【摘要】 集约化畜禽养殖场规模日益扩大,其导致的颗粒物污染随之增加,通过合理的拦截措施可以实现从源头对颗粒物污染的控制,从而减轻大气环境负担。植被屏障在拦截颗粒物过程中表现出高效、利于环境保护、经济成本低等优势,为畜禽场颗粒物排放控制提供了有效的解决思路,而作为典型植物元素结构,其枝-叶尺寸结构特征对颗粒物拦截起到重要作用,为进一步设计人工滞尘屏障提供了仿生原型。本文调研了以吉林省长春市的背景环境的养牛场与养鸡场的周边环境,依据长春市气候条件及畜禽场周边环境为基础建立了室内低速风洞,风洞洞体总高为1.8 m,全长6.5 m,实验段的风速范围为0~6 m?s-1。设计了模拟畜禽场颗粒物源的制备方法,该方法主要针对于畜禽场产生的初级颗粒物的模拟,而并未考虑畜禽场产生的次级颗粒物污染。通过EDS检测,对两种不同来源颗粒物粉末进行了成分分析:来源于养牛场的颗粒物粉末样品的成分包括,C、N、O、Na、Mg、Al、Si、P、S、Cl、K和Ca,其中C、N、O、Si和Ca是颗粒物源的主要组成成分,平均质量分数分别为30.4%,36.5%,20.5%,4.0%和3.1%;来源于养鸡场的颗粒物粉末样品的成分包括,C、N、O、Na、Mg、Al、Si、P、S、Cl、K和Ca,其中C、N、O、K和Ca是颗粒物源的主要组成成分,平均质量分数分别为34.67%,23.79%,34.44%,1.11%和1.89%。通过风洞测试系统对枝-叶尺寸结构的紫丁香植被拦截牛场颗粒物源的效率进行了试验研究,结果表明:叶表面积密度为19.05 m-1的紫丁香植被屏障,对风速的降低效率最高,范围为60%~85%,风速为2.7m?s-1时其降低效率最大,为88.2±8.23%;随着风速增加,风速的降低效率呈现出增加的趋势;紫丁香植被屏障对含小粒径颗粒物(粒径小于2μm的颗粒物)更多的颗粒物源拦截能力更高,适合于拦截超细颗粒物,叶表面积密度为19.05 m-1的紫丁香植被屏障在最低风速下其最高拦截效率可达48.0±6.0%。利用扫描电镜对紫丁香叶表进行微观形貌观察及颗粒物沉积分布情况:在紫丁香叶片主脉与次主脉附近分布有大量的无序“山脊状”条纹,并且可以观察到大量的细颗粒物沉积;叶片表面的条棱、沟脊及其它微观几何表面结构都能够增加颗粒物的沉积效率,密集的微纳二级结构分布有利于颗粒物的捕集;测得紫丁香叶片的接触角平均值为58.96±4.04°,可以认为紫丁香叶片表面属于亲水性表面,该特性使紫丁香植被屏障更利于颗粒物于其表面沉积。通过风洞测试系统对樟子松幼株植被拦截牛场颗粒物源的效率进行了试验研究,结果表明:在风速为0.9m?s-1,颗粒物源水平条件为pⅡ时,pm1、pm2.5和pm10的拦截效率出现最高值,分别为41.59%、26.41%和36.90%;pm1的拦截效率明显更高,表明樟子松制成的植被屏障对pm1有更好的拦截效果。与紫丁香植被对牛场颗粒物源的拦截效率相比,在接近6.56m-1叶表面积密度条件下,樟子松植被屏障的拦截效率仅略低于紫丁香植被,而风速降低程度却远远小于紫丁香植被,因此在拦截同样数量颗粒物的过程中其产生的风阻远小于紫丁香植被,这一特性适用于畜禽场颗粒物源的拦截控制,并为低阻力的仿生抑尘网提供了解决思路。利用sem观察拦截颗粒物前后的樟子松针叶正面与背面颗粒物沉积情况,结果表明:樟子松针叶表面微观结构整体呈现出有条理的“脊状”条纹带与气孔带有序排列分布,气孔间的区域有绒毛结构分布,大量颗粒物更易于沉积在该区域,并且在樟子松针叶背面沉积颗粒物要多于正面;另外其正面接触角为51.57±1.92°,背面的接触角为78.22±2.61°;通过eds与xps检测,在背面检测到颗粒物源的化学成分多于正面,再次证实樟子松针叶背面沉积的颗粒物源多于正面。采用风洞测试系统对紫丁香及樟子松植被屏障周围的风速进行测量,以考察植被屏障周围的气流分布,结果得出:在植被屏障的迎风面,气流速度发生衰减,在绕过植被屏障上方的监测点处抬升的气流,其流速增加,部分气流穿过植被屏障后速度发生衰减,在植被屏障后方监测点处明显降低,最终气流继续沿轴向流往实验段后部,在远离植被屏障的监测点处其流速呈现出一定的恢复趋势。另外,樟子松植被屏障对风速的降低效率要远小于相同条件下紫丁香植被屏障,最高风速降低程度为28.3%。对紫丁香植被屏障拦截鸡舍颗粒物源的效率进行了试验研究,结果表明:当风速为2.7m?s-1水平时,注入鸡舍颗粒物水平为pⅡ时,叶表面积密度为19.05m-1的紫丁香植被屏障,对风速的降低效率范围为65%~78%,风速档最大时其降低效率最大,为78.0±2.55%;与紫丁香植被拦截牛场颗粒物源的风洞试验结果对比可知,紫丁香植被屏障在拦截来自牛场与鸡舍的颗粒物源试验中对气流的影响基本呈现出相同的规律与趋势,但对于含鸡舍颗粒物源的气流而言,其风速降低程度要略低于牛场颗粒物源;与紫丁香植被屏障拦截牛场颗粒物源的效率相比较,紫丁香植被屏障对鸡舍颗粒物源对pm10的拦截效率出现显著的降低。利用sem扫描电镜对紫丁香叶片表面鸡舍颗粒物源沉积区域分布及其微观结构特征进行了观察,结果表明:紫丁香叶片表面的褶皱区域内积累了大量小粒径的颗粒物,尤其在无序“山脊状”条纹之间易沉积细颗粒物,粗颗粒物非常少见;XPS检测的成分表征证实PⅡ水平下紫丁香叶面积累颗粒物要多于P?水平;紫丁香叶片表面属于亲水性表面,由于鸡舍颗粒物源中的粗颗粒物主要来自饲料,为有机物颗粒物,亲水性较差;而牛场颗粒物源中的粗颗粒主要来自于土壤,为无机颗粒物,易溶于水,亲水性好,因此紫丁香植被更适用于对牛场颗粒物源的拦截。更多还原

【Abstract】 Increasing the scale of the intensive animal feeding operations(AFOs),which results in the increasing of the particulate pollution,by means of the reasonable intercepting measures can control the particulate pollution from the area source,so as to reduce the financial burden on atmospheric environment.Vegetative barriers(VB)showed the advantage of high efficiency,environment friendly,economical in the process of intercepting particulate matter(PM),which provides an effective solution to control the emission of PM from the AFOs.Some special branch-scale structures and micro-structures of vegetation play an important role in intercepting the PM,which provides a bionic prototype for the further design of artificial dust barrier.This study investigates the surrounding environment of the cattle feedlot and the laying hen house,in the background of ChangChun city,Jilin province.We build indoor low speed wind tunnel on the basis of the climate conditions of ChangChun city and the surrounding environment of the AFOs.The total height of the wind tunnel is 1.8 m,total length is 6.5 m.Wing velocity of the test section can be controlled continuously from 0 to 6 m s-1.We designed the method to simulate the PM source of AFOs.This method is mainly for the primary particle of the AFOs,the secondary particles are not in consideration.In addition,different sources of PM were identified through EDS tests.The elements of the cattle feedlot include C,N,O,Na,Mg,Al,Si,P,S,Cl,K Ca,of all the components,C,N,O,Si,Ca were the major components,with mean mass percentages of 30.4%,20.5%,36.5%,4.0%,3.1%,respectively.The elements of the laying hen house include C,N,O,Na,Mg,Al,Si,P,S,Cl,K,Ca,of all the components,C,N,O,K,Ca were the major components,with mean mass percentages of 34.67%,23.79%,34.44%,1.11%,1.89%,respectively.We tested the efficiency of the branch-scale structures of clove to the PM from the cattle feedlot,as a result,VB of clove with the surface area density(SAD)of ρ3 had the best efficiency to reduce the air flow,from 60% to 85%.When the velocity of air flow is V3,it had the highest efficiency,which is 88.2 ± 8.23%.With the increase of wind speed,the efficiency to reduce wind speed presents a trend of increasing.VB of clove has more efficiency to intercept the PM with a diameter smaller than 2μm,is suitable for intercepting ultrafine particles.VB of clove with the surface area density(SAD)of ρ3 had the most efficiency in the low wind speed,which can reach to 48.0± 6.0%.The micro-structures of clove and the particle deposition distribution on the leaf were observed through scanning electron microscope(SEM),as a result,more irregular “ridges” and apparent ditches of stripes distributed around or close to midrib and PM deposition also can be observed.The clove leaves have pinnate venation crossing the non-smooth surface with midrib in the center and many “ridge”-shape structures distributed on the surface which can increase the efficiency of PM deposition.The mean contact angle of clove leaves is 58.96 ± 4.04°,thus,clove leaves can be considered as hydrophilic surface,which have a characterize to capture more PM.We tested the efficiency of Mongolica shoot to the PM from the cattle feedlot,as a result,at the level of PⅡ with the wind speed of 0.9 m?s-1,PM1、PM2.5 and PM10 have the highest efficiency,which is 41.59%,26.41%,36.90%,respectively.And it showed more efficiency to PM1 than PM2.5 and PM10,which indicates that VB of Mongolica shoot have best efficiency to intercept PM1.Compared to the VB of clove to intercept PM from cattle feedlot,when the SAD was close to ρ1,the efficiency of the VB of Mongolica shoot just below the VB of clove,but the efficiency to reduce the wind speed is far less than the latter.Thus,in the process of the same number of PM,the former has a small wind resistance than the latter,which characterize is used to intercept the PM from AFOs,and it provides a solution for low resistance of bionic dust-controlling nets.The positive and negative of the Mongolica shoot needles before and after intercepting PM were observed through SEM,as a result,the micro-structure of the Mongolica shoot needles on the surface present a well organized “ridge” stripe band and porosity distribution,orderly arrangement with fuzzy structure distribution between the pores,a large number of PM are easier to deposit in this area,and on the back of Mongolica shoot needles deposit more PM than the positive.The contact angle of the positive is 51.57± 1.92°,while the negative is 78.22 ± 2.61°.More chemical composition of PM sources were detected in the back of the Mongolica shoot needles through EDS and XPS,which proved once more that Mongolica shoot needles deposit more PM in the negative than the positive.To investigate the air flow around the VB,the wind speed around clove and Mongolica shoot vegetation barrier were tested through wind tunnel,as a result,on the windward of VB,there is a decrease on the velocity of air flow.The velocity had an increase bypass the VB at the top of the lift air monitoring stations.Part of the air flow had a decrease after passing through the VB,there is significantly decrease in the back of the monitoring points of the VB,eventually it flow back into the back of the test section along the axial,and it presented a trend of recovery at the monitoring station which is far from the VB.In additional,under the level,the efficiency to reduce wind speed of Mongolica shoot VB is far less than clove VB,the highest efficiency is up to 28.3%.The efficiency of clove VB to intercept the PM from laying hen house is researched.As a result,at a level of PⅡ with wind speed of V3,clove VB with SAD ofρ3 had the wind speed reduced efficiency from 65% to 78%,which had the highest reduce efficiency when the wind speed is highest,showed the number of 78.0 ± 2.55%.Compared to the former test,clove VB had the same rule and trend of air flow when intercepting the PM from cattle feedlot or laying hen house,but for the air flow which contain the PM from laying hen house,the efficiency to reduce wind speed is just below the air flow which contain the PM from cattle house.Compared to the efficiency to intercept PM from cattle feedlot,clove VB showed lower efficiency on PM10 which came from laying hen house.The distribution and micro-structure characterize on the surface of clove leaves had been observed through SEM.As a result,there has a large number of small particle size accumulated on the fold area of the surface of clove leaves,especially more fine PM deposited in the disorder “ridge” stripe,but the coarse PM is little.Under the level of PⅡ,clove leaves accumulate more PM than the level of P?.The surface of clove belongs to hydrophilic surface,but the coarse PM which came from laying hen house is major generated from feed,which is organic compound particles and is poor hydrophilicity,as for the coarse PM which came from cattle feedlot is major generated from soil,which is inorganic compound particles and is soluble in water,good hydrophilicity,as a result,clove VB is more suitable for intercepting PM which came from cattle feedlot.更多还原