posted on 2021-10-18, 12:05authored byYanan Wang, Xiao Fu, Dianming Wu, Mengdi Wang, Keding Lu, Yujing Mu, Zhiguo Liu, Yuanhang Zhang, Tao Wang
Nitrogen
lost from fertilized soil is a potentially large source
of atmospheric nitrous acid (HONO), a major precursor of the hydroxyl
radical. Yet, the impacts of fertilizer types and other influencing
factors on HONO emissions are unknown. As a result, the current state-of-the-art
models lack an appropriate parameterization scheme to quantify the
HONO impact on air quality after fertilization. Here, we report laboratory
measurements of high HONO emissions from soils at a 75–95%
water-holding capacity after applying three common fertilizers, which
contrasts with previous lower predictions at high soil moisture. Urea
use leads to the largest release of HONO compared to the other two
commonly used fertilizers (ammonium bicarbonate and ammonium nitrate).
The significant promotion effect of fertilization lasted up to 1 week.
Implementation of the lab-derived parametrization in a chemistry transport
model (CMAQ) significantly improved postfertilization HONO predictions
at a rural site in the agriculture-intensive North China Plain and
increased the regionally averaged daytime OH, O3, and daily
fine particulate nitrate concentrations by 41, 8, and 47%, respectively.
The results of our study underscore the necessity to include this
large postfertilization HONO source in modeling air quality and atmospheric
chemistry. Fertilizer structure adjustments may reduce HONO emissions
and improve the air quality in polluted regions with intense agriculture.