| Hygienic buffer zone is the minimal distance between residential district and boundary of the department (plant or section) which can release hamful pollutants to the air.The purpose of hygienic buffer zone is to providea certain dilution distance so as to the concentrationof pollutants from plant emmissionsource can be decreased to satisfy the national standards when they reach residential areato protect health of people nearby. It refers to subjects such as environmental hygiene, pollution meteorology, epidemiology, urban and rural planning. and socio-economic. The approval of the national standard Hygienic buffer zone in China was made in2001and the data used for the approvalwere collected in1990s. Great improvements have been made not only in production technology, environmental conditions, energy conservation but also in controling pollution emissions for slaughtering and meat processing plants recently. Thus, there are many sharp differences between the plantscurrnetly and that in1990s. On other hand, the demand of adjusting and optimizing sructure, eliminating laggard capacity,advocatingnew mode of clean production.conserving energy as well asutilizing resources comprehensively was put forward according to the Plans for the Pig Slaughtering Industry Development2010～2015. Soit is necessary to conduct the subject which aims at verifying whether the current Hygienic Buffer Zone in China is still appropriatecurrent.This is significant because it can not only protect health of people but also favour further development of this industry.We selected a saughtering and meat processing plants located inAnhui Province with an area of26million square meters for this survey. The capacity production for the plants was6500pigs per day. We selected10health indicators for this monitoring as follows:NH3, H2S, malodour, PM10, CO2temperature, relative humidity. average wind speed, wind direction and solar radiation intensity on the basis of literatures home and abord. The environmental monitorings were carried out on May25th～27th.(Spring) Augst24th～26th,(summer).November25th～27th (fall) of2010and Jaunary11th～13th(winter) of2011respectively.Every four survy was lasted for3days in each season and was repeated for3times each day:we began with our sampling at8:00in the morning,11:00in the noon and15:00in the afternoon. All survys werelasted for40min with flowrate of1.5L/min. The source of pollution was open style. All sampling sites were classified as three sorts:①source of fugitive emission(one sampling site);②the plants (two sampling sites:Site A and Site B)and③buffer zone:downwind of the pollution(six sampling sites) which were50m,100m,200m,300m,400m,500m away from the source respectively. Fan-shaped distribution of all sampling sites was used to make sure all monitoring sites can represent the pollution situation best. The height of the air sampler was1.5m from the ground and each concentration was repeated for3times evenly in order to guarantee the stability and reliablity. The control monitoring site was located100m away from the source upwind. The concentrations of NH3、H2S、PM10and malodor were monitored with current national standard method except for PM10(PM10:TSI SIDEPAKTM AM510Personal Aerosol Monitor), NH3:Air and exhaust gar-Determination of ammonia-Nessler’s reagent spectrophotometry, HJ533-2009(sharpness of0.5μg per lOmL absorpotion liquid);H2S:Standard method for hygienic examination of hydrogen sulfide in air of residential areas-Methylene blue spectrophotometric method, GB11742-89(sharpness of0.15μg per10mLabsorpotion liquid); Malodor: Air quality-Determination of odor-Triangle odor bag method, GB/T14675-93;The concentration of CO2and the temprature as well as the relative humidity were monitored by portable direct-reading instrument TSI-7454. Sharpness of the instrument for temprature was0.1℃and0.1%for relative humidity. The wind speed and wind direction were monitered by anemoscope KA22(the range was0-4.99m/s,the sharpness was0.01m/s). The hygienic buffer zone was calculated according to the Technical methods for making local emission standards of air pollutants,(GB/T13201-1991) and provied science evidence for the govement to make new national standards.The results showed that tempeture in four seasons were28.25±3.188℃.23.83±5.000’C,21.24±3.694℃and5.521±2.868℃respectively and for the relative humidity, they were58.61±9.923%,90.20±7.683%.43.42±12.45%and30.30±8.932%respectively.The wind speedin four seasonswere1.243±0.7924m/s,1.615±1.234m/s.1.093±1.013m/s and1.390±1.267m/s respectively. The wind directionin spring and autumn were southeast and in summerit was northwest. It was northwest switch to southerly in winter. The results of variance analysis showed that the tempratureand the relative humidity were influenced significantly by season (P<0.001). However, there were no significant difiences forwind speed between seasons (P=0.596).Thefuther comparison of SLD showed that temprature was highest in spring and lowest in winter. The second highest temprature was in summer.The wettest season was in summer and the driest was in winter. The second wettest season was spring. The concentration of NH3in source of pollution in four seasons were1.66±0.492mg/m3,1.77±0.469mg/m3,1.09±0.234mg/m3,0.97±0.432mg/m3respectively.It was in moitoring site of200m that the concentration of NH3Was below0.2mg/m3in spring, summer and autumn and100m in winter. The concentration of H2Sin source of pollution in four seasons were0.018±0.032mg/m3,0.022±0.003mg/m3,0.019±0.005mg/m3,0.0540±0.0686mg/m3respectively.It was in moitoring site of200m that the concentration of H2S was below0.01mg/m3in spring, summer and autumn and100m in winter. The concentration ofPM10in source of pollution in four seasons were0.229±0.067mg/m3,0.136±0.047mg/m3,0.327±0.169mg/m3,0.261±0.112mg/m3and all concetnrations of PM10were above0.15mg/m3except that in summer. The concentration of malodourin source of pollution in four seasons were71±6.48(not-dimentional),55±0.000,67±9.165,39.12±15.30. It was inmonitoring site of300m that the concentration of malodour was undetectable (signed as10). The concentration of CO2in source of pollution thoughout a year were500.0±61.9ppm,568.0±71.0ppm,474.5±28.4ppm,492.13±62.8ppm respectively. The results of variance analysis showed that NH3was influenced by season, time interval, interaction between them and distance between source of pollution and sampling sites significantly. This conclution was also applied to H2S. PM10was affected by season. time interval and interaction between them significantly. Malodour were influenced by season, time interval, interaction between them, distance mentioned above,interaction between distance and season,between distance and time interval significantly (p<0.05).The concentrations of CO2were effected only by distance significantly.The results of SLD showed that concentrations of NH3in all sampling sites could be classified into three sorts according to whether they were significantly among each other:monitoring site in source of pollution;50msampling site:other sampling sites.For H2S. it could be classified into two sorts:monitoring site in source of pollution and other sampling sites.For malodour.it could be classified into four parts:monitoring site in source of pollution; sampling sites in plant:50m sampling sites and other sampling sites. It was no necessarity toconduct the SLD comparisonfor according to distance because itsconcentrations were not impacted by distance significantly (P=0.068).The results of bar chart showed that it was highest in the morning of autumn and lowest in the the morning of summer for PM10.Thanks to the fact that there were no significant differences for CO2in different seasons and different time intervals, so we analysized the fluctuation of itvarying to different distance away from the source. The chart bar showed that its concentration was highest in source of pollution and rather flat in other sampling sites.The regression coefficient between tempture and concentration of NH3、H2S、PM10、malodor were positive but negative for that between the relative humidity andthese pollutants. The regression coefficient between distance and NH3、H2S、PM10、malodor were negative too. The factors of tempture、distance and the relative humidity contributed to the variation of NH3、H2S、PM10、malodor to different degrees.The questionarie survy implemented to the people was conducted by stratified random sampling in each monitoring site and108people were planed to survy but only100pieces of questionaires were retrived(recovery rate was92.59%). The results of the survy on the symptomsofnausea,headache dizziness,fatigue,throat irritation,blunted in smell,and inattention caused by the air pollutants showed that the reply that they had been impacted by the air pollutants were100%,100%,100%,100%,87.5%respectively in source ofpollution.There was no one to reply that they had been influenced by air pollutants in sampling site located300m-400m away and futher from the source. Then, all people questioned in this survy were classified into different groups according to their age, gender as well as whether they were employees of the plant. The results of the survy on how the air was contaminated by the slaughtering and meat processing plants showed that different age group (P=0.038) and different people(employee group and residential group)(P<0.001) were distinct significantly respectively. But there were no significant difference between gender (P=0.076)and smoking(χ2=3.17,P=0.366). The results on the survy of which season and time interval were polluted most severely by the plant showed that there was no difference on the fomer (P=0.139) but distinct significantly on the latter (P=0.003). All informants replied that the atmosphere was contaminated badly in summer. However, employees in plant tended to consider the air was polluted severely most in the afternoon but in the morning for the residents group. The χ2test showed that symptoms caused by the air pollutants were different significantly between employee group and residents group questioned in this survyThe calculation on the hygienic buffer zone was made according to Technical methods for making local emission standards of air pollutants,(GB/T13201-1991). The results showed that the widest hygienic buffer zone for NH3、H2S、 PM10、malodour thoughout one year was476.5m、46.3m、46.6m and309.4m with recent5years wind speed of<2m/s. With recent5years wind speed of2-4m/s, the widest hygienic buffer zone for NH3、H2S、PM10and malodour thoughout one year was347.3m、188.4m、166.4m and232.2m. And with recent5years wind speed of>4m/s, the widest hygienic buffer zone for NH3、H2S、PM10and malodour thoughout one year was285.1m、48.4m、31.6m and186.0m respectively. We concluded that it is reasonable if the hygienic buffer zone was revised as500m、400m、300m with the slaughter capacity of6500per day under the wind speed of<2m/s、2～4m/s、>4m/s respectivelyfor recent5yearson the demand of Technical methods for making local emission standards of air pollutants,(GB/T13201-1991). |
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