Regional nitrate deposition inferred from ground- and space-based measurements

Miaomiao CHENG1, Zheng GUO2, Fan MENG1

1 State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China, Email:[email protected]

2 Division of Remote Sensing Data Application, National Satellite Meteorological Centre, Beijing 100081, China

Abstract

Spatial and temporal nitrate deposition fluxes were assessed using satellite data in the Yangtze River Delta (YRD) from 1996 to 2011. Our study reveals significant spatial variations of nitrate deposition. In general, the fluxes of total (dry plus wet) nitrate deposition was up to 22 kg N ha-1 yr-1 with large loading rates received in winter. Most high fluxes appeared over urban (38 kg N ha-1 yr-1) and cropland (30 kg N ha-1 yr-1) areas. During the study period (1996-2011), a significant increasing trend of nitrate deposition was observed with an annual increasing rate of 1.33 kg N ha-1 yr-1. The spatial patterns of estimated nitrate deposition also showed that there were much higher fluxes and annual increasing trend in the middle region of YRD, i.e., the metropolitan areas contained Shanghai-Nanjing-Hangzhou cities, than in other areas. Our results also reveal that dry nitrate deposition contributed more than 50% of the total nitrate deposition over all provinces and land covers except coastal sea (14%), which indicates the relative importance of dry deposition to the total nitrate deposition in YRD region. Our study suggests that it is necessary to consider both dry and wet deposition when evaluating the influences of nitrate deposition on environment and ecosystem health.