中文摘要：

大气中HNO_2光解是OH自由基的重要来源,对大气光化学污染形成非常重要。该研究基于珠三角地区大气超级监测站2013年10月大气中HNO_2、NOx、O_3浓度、HNO_2光解速率常数及太阳辐射等相关参数的在线监测结果,分析了当地HNO_2变化规律与污染特性,并测算了通过HNO_2光解产生OH自由基的速率。观测期间,HNO_2小时浓度为0.48~9.92μg/m3,平均浓度为3.02μg/m3;HNO_2光解产生OH自由基的速率平均为1.53×107个/（cm~3·s）。HNO_2的日变化呈夜间高浓度、午后低浓度的特征,与其重要前体物NOx日变化规律类似。HNO_2浓度与NOx及颗粒物表面积浓度具有较好的正相关性;当相对湿度高于60%时,HNO_2与颗粒物表面积的线性相关性显著增加,意味着高湿度条件下颗粒物表面的非均相反应对HNO_2生成贡献显著。HNO_2光解速率常数主要受到太阳辐射的影响,其日变化规律与日照基本一致,在中午11时-13时出现高值;但随着太阳辐射增强,HNO_2光解速率常数增长速率有所减缓。HNO_2光解产生OH自由基的速率的平均日变化中,其日间高值持续时间较长,8时左右即开始出现,持续至下午臭氧高值时段。HNO_2日最大小时浓度、HNO_2光解产生OH自由基的日最大速率均与O_3日最大小时浓度具有一定的正相关关系,体现了HNO_2在光化学污染中的重要作用。

英文摘要：

Photolysis of HNO_2 in the atmosphere is an important source of OH radical, and plays a crucial role in the formation of photochemical pollution. Based on the online observation of gaseous HNO_2, NOx, O_3, HNO_2 photolysis rate constant, and solar radiation during October of 2013 at the atmospheric supersite in the Pearl River Delta（PRD） region, the variation pattern and pollution properties of HNO_2 were analyzed, and the production rate of OH radical through HNO_2 photolysis was evaluated. During the measurement period, the hourly concentrations of HNO_2 were 0.48 ~9.92 μg/m3, with average concentration of 3.02 μg/m3. The average values of OH radical production rate through HNO_2 photolysis was 1.53 ×107molecule/cm3 s. HNO_2 showed high concentrations at night and low ones during daytime, which was similar to the average diurnal variation of its precursor NOx. The positive relations between HNO_2 and NOxor surface area concentrations of particles were quite good, and the relation between HNO_2 and surface area concentrations of particles became significantly better with relative humidity over 60%. It indicated that heterogeneous reaction of NOxon the particle surface under conditions with high relative humidity contributed a lot in HNO_2 formation. HNO_2 photolysis rate constant was mainly affected by solar radiation,and showed similar average diurnal variation to the latter, with high values from 11：00 to 13：00. However, as the solar radiation became more and more intense, the increase rate of HNO_2 photolysis rate constant turned to be slower. In the average diurnal variation of OH radical production rate, a longer time period of high values were observed, from about 8：00until the high value period of O_3 in the afternoon. The daily maximum hourly average values of HNO_2 concentrations, OH radical production rate, and O_3 concentrations had positive relation, reflecting the important role of HNO_2 in the photochemical pollution.