Dry deposition of ammonia around paddy fields in the subtropical hilly area in southern China

Figures & data

Figure 1. Daily NH₃ concentrations at downwind sites in the early rice season.

Figure 2. Daily NH₃ concentrations at downwind sites in the late rice season.

Figure 3. Mean concentrations of NH₃ during the 15 days after basal fertilizer application (DAB), 15 days after topdressing (DAT) and the non-fertilization period (OtherP) at the downwind and upwind sites of the paddy fields in the (a) early and (b) late rice seasons.

Table 1. Ammonia dry deposition during the fertilization period (15 days after N application) and the non-fertilization period in the downwind area 100 m from the paddy fields in the early and late rice seasons.

	Early rice season				Late rice season
	15DAB	15DAT	OtherP	Total	15DAB	15DAT	OtherP	Total
NH3_up	2.31	1.81	2.43		2.86	3.43	2.04
NH3_dn	26.5	3.68	3.67		23.3	18.0	2.08
A_dn (m^2)	15,426	15,426	15,426		15,426	15,426	15,426
PoSW	0.42	0.53	0.40		0.54	0.18	0.24
PoNW	0.45	0.44	0.45		0.35	0.77	0.64
Vd_shrub	0.57	0.57	0.57		0.56	0.56	0.56
Vd_cropland	0.44	0.44	0.44		0.44	0.44	0.44
Duration (d)	15	15	44	75	15	15	76	106
DD_dn (kg)	2.34	0.36	0.93	3.62	2.02	1.83	0.98	4.83
DD_bg (kg)	0.11	0.18	0.61	0.90	0.17	0.30	0.86	1.33

Notes: 15DAB, 15 days after basal fertilizer application; 15DAT, 15 days after topdressing; OtherP, other periods; NH₃_up, mean NH₃ concentration (μg N m⁻³) in the upwind direction; NH₃_dn, mean concentration (μg N m⁻³) in the downwind direction; A_dn, the downwind area within 100 m from the paddy fields calculated as the weighted average of NH₃ concentrations measured at the 0, 20, 50, and 100 m downwind sites; PoSW, proportion of the period with south winds; PoNW, proportion of the period with north winds; V_d_shrub, NH₃ dry deposition velocity on shrubs; V_d_cropland, NH₃ dry deposition velocity in croplands; DD_dn, total NH₃ deposition in the downwind area; DD_bg, total NH₃ deposition in the downwind area caused by the background NH₃ concentration.