Physical And Chemical Characteristics Of Atmospheric Particulate Matter And Their Impact On Human Health In Lanzhou

Urban air pollution especially particulate matter pollution has been a threat to human healthfor a long period of time. In China, air pollution is a particularly serious problem with the rapidurbanization and economic growth. Numerous studies indicated that the atmospheric particulatematter, especially fine particulate matter are responsible for respiratory and cardiovascularmorbidity and mortality, and their toxicity is closely associated with their size and chemicalcomposition. In this thesis, Lanzhou city is chosen as the study area which was famous for airpollution. Both the change characteristics of the air pollution in recent 20 years and theconcentrations of particle matter with different sizes from 2005 to 2007 were analyzed. Thedifferent sizes of particle matter samples from different functional areas (industrial areas, heavytraffic areas, rural areas) and different seasons were collected and the water-soluble ions and 20kinds of inorganic elements were analyzed. Furthermore, the relationship between air pollutionand daily hospital admissions respiratory and cardio-cerebralvascular diseases were studiedusing GAM model. The biological mechanisms of toxic effects on human health induced byparticulate matters were also investigated through the toxicological experiments. Somemeaningful results were obtained.(1) In recent 20 years, the main air pollutants( PM₁₀, SO₂, NO₂) in Lanzhou city have beendecreasing gradually, and in winter and spring their concentrations were higher than that insummer and autumn, heating period were higher than that in the non-heating period. Two peaksof PM₁₀ were appeared, one was between December and January the next year, and the otherwas between March and April, indicating that both coal-burning and dust were contributed toPM₁₀; annual variation of SO₂ and NO₂ were shown as U-curve and change of NO₂ wassmoother, indicating that coal-burning was main contributor to SO₂ in winter and NO₂ mainlycame from vehicle exhaust. The characteristics of different sizes of particulate matter weredifferent, concentrations of TSP and PM₁₀ were the highest in spring or dust period, followed byheating period, and the non-heating period was the lightest; fine particulate matter PM_2.5 andPM_1.0 were the highest in winter or the heating period, dust period and non-heating period hadno difference. (2) The main water-soluble ions of different sizes of particles in Lanzhou were dominant bySO₄²-,NO₃^-, Ca²⁺, NH₄⁺. In different functional areas, the change trend of SO₄^2- , NO₃^-, NH₄⁺were similar with winter＞spring＞autumn＞summer. However, the concentrations of Ca²⁺ andMg ²⁺ were the highest in spring than that in other seasons. The contribution of water-solubleions to the quality of fine particles was greater than to the coarse particulate matter. Mineralelements such as Ca²⁺, Mg²⁺ and K⁺ were higher in TSP than that in the fine particulate matters.In contrary, the secondary aerosol ions including SO₄^2-, NO₃^- and NH₄⁺ were higher in the fineparticulate matter PM_2.5. The ratios of NO^3-/SO₄^2- in particulate matter were between 0.2 and0.5, and in industrial areas and heavy traffic areas, the maximum value was 0.49 in summer andthe minimum was 0.21 in winter, indicating that the contribution of coal-burning to air pollutionwas higher than motor vehicle exhaust in winter; in rural areas, the ratios of NO^3-/SO₄^2- werestable in difference seasons and the average value was 0.34, suggesting that the contributions ofcoal-burning and motor vehicle exhaust to SO₂ and NO₂ were closely.(3) With significant differences of pollution level at different functional areas, the mainelements of different sizes of particles include Ca, S, Fe, Mg, K, Zn, Pb, P, Mn, Na and Ba. Inindustrial areas such as Xigu district, the pollution level is the most serious, followed by heavytraffic areas and the rural areas are the most slightly. The seasonal variations of elements indifferent function areas were similar. In Yuzhong it was the highest in spring, followed byautumn and winter, the summer was the lowest, while in Chengguan district and Xigu districtwere the highest in winter. Typical crustal elements, such as Ca and Mg, showed the similarseasonal variations, the highest in spring, lowest in summer, and pollution elements, theidentification elements for coal-burning, such as S, Zn, As, were the highest in winter, followedby spring and autumn, the lowest in summer. The pollution elements come from industrialpollution such as Mn, Cd, Ni, Cu, V didn't show obvious seasonal variations because industrialemissions was continuous throughout the whole year. Pb had a high pollution level because ofvehicle exhaust.(4) There was a lag effect of air pollutants on different respiratory diseases in Lanzhou. RRvalues reached the maximum in the following sequences: PM₁₀ with a lag of 3～5d, SO₂ with alag of 1～3d (upper respiratory tract infection 6d) and NO₂ with a lag of 2～4d, and there weresignificantly associated with disease. Furthermore, with increase of PM₁₀, SO₂ and NO₂ for 10μg/m³, RRs of daily hospital admissions for total respiratory diseases were 1.002(95%CI:1.000～1.003), 1.005(95%CI: 1.000～1.010) and 1.011(95%CI: 1.002～1.019) respectively. Thesensitivity of air pollutants to different diseases is not the same. The sequence from strong toweak is as follows: pneumonia＞upper respiratory tract infection＞COPD, and female andpeople over 65 years old to pollutants were more sensitive than male and under 65 years.(5) The effects of air pollutants on different cardiovascular and cerebrovascular diseaseincluding different age and gender in Lanzhou were different. There are significantlyassociations between the three main pollutants and total cardio-cerebrovascular disease with alag of 2～4d; PM₁₀ with a lag of 2d, SO₂ and NO₂ on ischemic cardiovascular disease wereimmediate effect; PM₁₀ with a lag of 7d (elderly group 2d), SO₂ and NO₂ with a lag of 2～4d onhypertension; PM₁₀ with a lag of 6d (male 2d), SO₂ and NO₂ with a lag of 3～4d (female 7d) onstroke. Furthermore, when PM₁₀, SO₂ and NO₂ increase l0μg/m³, the RRs of daily hospitaladmissions for total cardio-cerebrovascular diseases were 1.001 (95%CI: 1.000～1.003),1.007(95%CI: 1.003～1.012) and 1.008(95%CI: 1.001～1.016) respectively.(6) Fine particulate matter PM_2.5 shows cell toxicity to RAW264.7 cell line. The particlesfrom countryside show a weak apoptosis effect on the cell but particles from industrial areasand heavy traffic areas show a stronger effects; There is a seasonal variance of the apoptosiseffect: the strongest in winter, followed by spring and summer, the weakest in autumn; for celldeath, there is a clear dose-response relationship, but is not very different between eachfunctional areas. The lethal capacity of PM₂₅ also shows a seasonal variation: the strongest inwinter, followed by spring and autumn, the weakest in summer.