东莞与帽峰山黑碳气溶胶浓度变化特征的对比

Compare of black carbon concentration variation between dongguan and maofengshan

将东莞(海拔30m,位于平原地区)与帽峰山(海拔550m,位于山地地区)的黑碳气溶胶(BC)浓度进行对比,结果表明,东莞地区BC浓度年均值为5.27 g/m3,帽峰山BC浓度值为2.43 g/m3,两个站点的浓度都比位于珠三角核心区的南村站浓度(8.42μg/m3)低.雨季,东莞与帽峰山BC浓度的日变化特征在中午呈现反位相,这是因为两站近地层受上升气流控制,热对流把地面的BC气溶胶带至高空,地面浓度下降,东莞出现谷值,而高空有了地面的垂直输送补充,帽峰山出现峰值.旱季,华南地区受高压控制,微弱下沉气流对于BC的垂直输送不利,BC的扩散以平流扩散为主,两地日变化情况相近.此外,受BC源远近的影响,东莞的逐月变化(标准差为0.60μg/m3)大于帽峰山(标准差为0.14μg/m3).通过分析BC吸收系数的波长幂指数α探讨可能的污染来源,发现两地的α值均接近于1,说明两地BC的污染来源相同,均来自于化石燃料的燃烧.

A comparison analysis was carried out on black carbon （BC） concentrations in Dongguang at an altitude of 30m and Maofcngshan at an altitude of 550 m in the Pearl River Delta （PRD） region. The annual average concentration of BC was 5.27μg/m3 at Dongguan and 2,43μg/m3 at Maofengshan. Concentrations of BC at both sites were significantly lower than level of 8.42μg/m3 observed in Nancun station in Guangzhou, a site in the heart of the PRD area. The results show that in the rainy season, the diurnal variations at the Dongguang and Maofengshan were different as a result of influence of vertical convection. The heat-induced convection brought BC from ground to higher altitudes, lowering concentration on the ground while increasing concentration at higher latitudes. This explains that at noontime, Dongguan experienced the minimum BC concentration while BC peaked at Maofengshan. In the dry season when the synoptic weather in South China was controlled by high-pressure systems, the weak descending air had little effect in promoting vertical mixing and air dispersion was dominated by horizontal advection. Consequently, similar diurnal variations were observed at the two locations. Due to closer proximity to BC sources, the monthly variation of BC in Dongguan （standard deviation： 0.60 μg/m3） was larger than that in Maofengshan （standard deviation： 0,14 μg/m3）. The value of α, which is the power index of the wavelength of BC absorption coefficient, was found to be close to 1 at both sites, indicating that BC at the two sites had fossil fuel combustion as the common source.