基于本地化因子的上海市露天蔬菜地氨排放时空分布特征

为获取上海地区露天蔬菜种植的NH₃排放规律及时空分布特征，通过通气-氨捕获法对露天蔬菜种植的NH₃排放特征进行监测，并对主要气象参数进行同步观测。结果表明，4个季节5种典型露天蔬菜的NH₃累积排放量范围为14.44~41.94 kg·hm^-2，NH₃排放通量最大值出现在施肥后2~5 d，NH₃排放持续时间为15~18 d，追肥期的NH₃排放通量显著高于基肥期。叶菜类、瓜类、茄果类、豆类和白菜类的NH₃排放损失率分别达到了6.02%、18.30%、14.98%、14.57%和11.77%，表现为瓜类>茄果类>豆类>白菜类>叶菜类。相关性分析表明，温度和湿度是影响露天蔬菜种植NH₃排放的主要因素，温度对NH₃排放有显著的促进作用，湿度则与之呈较好的负相关关系。2017年上海市露天蔬菜种植NH₃排放总量达到832 t，空间分布特征表明，上海市露天蔬菜NH₃排放总量最高的3个区为崇明区、浦东新区和青浦区，合计占NH₃排放总量的67%以上； NH₃排放季节变化特征表现为夏季>秋季>春季>冬季，夏季的NH₃排放总量达到冬季的3.6倍。研究表明，上海地区露天蔬菜种植的NH₃排放变化特征显著，时空分布具有明显的规律性。

Local emission factors and spatio-temporal distribution of open-air vegetable production-related ammonia emissions in Shanghai

In this study, we monitored the ammonia emission characteristics of open-air vegetable cultivation using the dynamic boxaeration method and simultaneously observed the main meteorological parameters in order to obtain the characteristics of ammonia emission from open-air vegetable cultivation and its spatio-temporal distribution in Shanghai. The results showed that the cumulative ammonia emission amount of 5 typical open-air vegetables in 4 seasons ranged 14.44~41.94 kg·hm^-2, and the highest ammonia emission appeared between day 2 and day 5 post fertilization. Most of the emitted ammonia was released within 15~18 days. The ammonia emission during the topdressing stage was significantly higher than that of the base fertilization stage. The ammonia emission loss rates of leafy vegetables, melons, solanaceous fruits, beans, and cabbage reached 6.02%, 18.30%, 14.98%, 14.57%, and 11.77%, respectively, following the order of melon > eggplant > beans > cabbage > leafy vegetables. The correlation analysis showed that temperature and humidity were the two main ammonia emission-affecting factors in open-air vegetable cultivation lands. Furthermore, temperature and humidity exhibited a strong positive and a significantly negative correlation with the ammonia emission flux, respectively. In 2017, the total ammonia emissions from open-air vegetable cultivation in Shanghai reached 832 tons. Analyses of the spatio-temporal distribution characteristics of total ammonia emissions in Shanghai showed that the three districts with the highest ammonia emissions are Chongming, Pudong, and Qingpu, accounting for more than 67% of the total ammonia emissions. The seasonal distribution characteristics of the total ammonia emissions are summer > autumn > spring > winter across the whole city of Shanghai. The total ammonia emissions in summer are 3.6 times significantly higher than those in winter. In conclusion, the NH₃ emission of open-air vegetable cultivation in Shanghai exhibits significant changes and its spatio-temporal distribution shows obvious regularity.