| 兰州河谷盆地大气多环芳烃干沉降通量及来源 |
| 摘要点击 2209 全文点击 644 投稿时间：2017-01-22 修订日期：2017-03-08 |
| 查看HTML全文
查看全文 查看/发表评论 下载PDF阅读器 |
| 中文关键词 兰州河谷盆地 大气多环芳烃 干沉降 污染特征 来源解析 干沉降速率 |
| 英文关键词 Lanzhou valley atmospheric PAHs dry deposition fluxes spatial distribution characteristics source appointment dry deposition velocity |
|
| 中文摘要 |
| 利用大气被动干沉降采样技术对兰州河谷盆地 13个采样点的 15种 USEPA优控 PAHs的大气干沉降进行了 观测研究，并对其污染特征及来源进行了解析. 结果表明15种PAHs的年大气干沉降通量范围为7.48~53.94 μg·（m2·d）-1，均值为18.65 μg·（m2·d）-1；采暖期和非采暖期干沉降通量均在交通最为密集的采样点东岗桥最高，分别为60.85和47.03 μg·（m2·d）-1，植被较好的城区黄河边白塔山最低，分别为8.16和6.80 μg·（m2·d）-1，背景点官滩沟明显低于其他各采样点，为6.73 μg·（m2·d）-1和4.92 μg·（m2·d）-1；PAHs干沉降的族谱特征为：两季节均以3、4环的Phe、Flua、Flu和Pyr为主要污染物，所占比例分别为采暖期87.53%、非采暖期82.73%，而非采暖期5、6环所占比例高于采暖期，推断可能由于较轻组分PAHs由于气温较高易挥发所致；利用主成分分析法进行源解析，结果表明：PAHs大气干沉降主要来自汽车尾气和燃煤炼焦，除交通采样点（东岗桥）外，采暖期燃煤、炼焦为主要贡献源，非采暖期以汽车尾气排放贡献为主. 此外，本研究还运用干沉降模型，利用气象数据对城区（城关区环境保护局，JCZ）、工业区（西固区兰苑宾馆，LLH）和七里河区交通干道（职工医院，ZGH）采样点位的大气PAHs干沉降速率进行了模拟计算，3个采样点年均沉降速率分别为0.20、0.15和0.17cm·s-1，相对较小，该沉降速率由该处的风速、气温和下垫面性质等综合气象条件决定. 模拟计算与观测的3、4环组分干沉降通量值处于同一数量级，模拟通量值略大于观测值，4环PAHs吻合较好，而3环组分在观测过程中有部分挥发损失. |
| 英文摘要 |
| The atmospheric dry deposition flux pollution levels were determined and the sources apportioned for 15 US EPA priority polycyclic aromatic hydrocarbons (PAHs) collected at 13 sampling sites in the Lanzhou valley using passive sampling techniques. The results are as follows. The annual atmospheric dry deposition fluxes ranged from 7.48 to 53.94 μg·(m2·d)-1, with a mean of 18.65 μg·(m2·d)-1. The highest flux levels for both the heating and non-heating seasons, 60.85 μg·(m2·d)-1 and 47.03 μg·(m2·d)-1, respectively, appeared at the traffic site (Donggang Bridge), where the heaviest traffic in the Lanzhou valley occurs. The lowest flux levels of 8.16 μg·(m2·d)-1 and 6.80 μg·(m2·d)-1 for the heating and non-heating seasons, respectively, were found at Baita Mountain, which has a higher percentage of vegetation cover. Meanwhile, the flux levels at the background site (Guantangou Mountain) were significantly lower than those of the other sampling sites. For dry deposition, the PAH components Phe, Flua, Flu, and Pyr were dominant in the heating and non-heating periods, and the sums of the percentages of 3- and 4-ring PAHs were 87.53% for the heating season and 82.73% for the non-heating season. Moreover, the percentage of 5- and 6-ring PAHs for the non-heating period was higher than that for the heating period, which may be because the lighter PAHs were easily volatilized, and thus escaped. Furthermore, the sources of atmospheric dry deposition were identified by principal component analysis (PCA). The results of source apportionment showed that the main atmospheric PAH dry deposition in the Lanzhou valley were from vehicle exhaust emissions, coal combustion, and the coking industry. In further detail, coal combustion and the coking industry contributed most of the PAH dry deposition emissions during the heating period except for the traffic area site of Donggang Bridge, whereas vehicle exhaust was the dominant contributor during the non-heating season. In addition, the annual average dry deposition velocities of atmospheric PAHs were calculated using the dry deposition model for three sites: 0.20 cm·s-1 downtown (Environmental Protection Agency of Lanzhou; JCZ), 0.15 cm·s-1 in an industrial area (Lanyuan Hotel of Xigu; LLH), and 0.17 cm·s-1 in a traffic area (the Staff Hospital of Gansu Province; ZGH), of which the latter two were relatively lower because of comprehensive meteorological factors such as wind speed, temperature, and land use categories. Regarding the dry deposition flux values of the 3- and 4-ring PAHs, the simulated values were a bit larger than the observed values, but all were at the same level of magnitude. However, the simulated flux values were closer to their observed values for 4-ring PAHs than for 3-ring PAHs, which indicated that 3-ring PAHs were lost more easily than 4-ring PAHs were during monitoring. |
|
|
|
