Seasonal trends of the stable nitrogen isotope ratio in particulate nitrogen compounds and their gaseous precursors in Akita, Japan

Figures & data

Fig. 1. Concentrations of water-soluble ions in SPM sampled at Akita Prefectural University during spring (March–May), summer (June–August), autumn (September–November), and winter (December–February) between April 2008 and December 2010.

Fig. 2. Variations of (a) δ¹⁵N-NH₄⁺ values and NH₄⁺ concentrations, and (b) δ¹⁵N-NO₃^– values and NO₃^– concentrations in samples collected at Akita Prefectural University from April 2008 to December 2010.

Table 1. Seasonal concentration (± S.D.) data for NH₃ and NH₄⁺, the NH₃/NH₄⁺ ratio, δ¹⁵N-NH₃, and δ¹⁵N-NH₄⁺, and the NH₃–NH₄⁺ fractionation factor (εNH₃–NH₄⁺) for samples collected at Akita Prefectural University from December 2009 to December 2010.

	NH3 (μg/m^3)	NH4^+ (μg/m^3)	NH3/NH4^+ (mol ratio)	δ^15N-NH3 (‰)	δ^15N-NH4^+ (‰)	εNH3–NH4^+ (‰)
Spring	5.38 ± 3.08	0.50 ± 0.35	11.3	–20.8 ± 8.4	15.3 ± 5.1	+37.4 ± 5.7
Summer	5.52 ± 3.99	0.43 ± 0.36	13.6	–16.7 ± 6.5	18.0 ± 7.0	+33.8 ± 9.8
Autumn	1.44 ± 0.53	0.28 ± 0.23	5.5	–8.1 ± 4.5	18.8 ± 5.3	+28.9 ± 9.2
Winter	1.77 ± 1.51	0.37 ± 0.22	5.1	–23.9 ± 6.7	11.7 ± 7.0	+33.9 ± 7.7
All seasons	3.36 ± 3.05	0.40 ± 0.31	9.0	–16.9 ± 8.8	16.1 ± 6.6	+33.3 ± 8.2

Fig. 3. Variations from December 2009 to December 2010 of (a) δ¹⁵N-NH₄and δ¹⁵N-NH₃ in ambient air and at the cow barn site; (b) δ¹⁵N-NO₃^–, δ¹⁵N-NO_x, and δ¹⁵N-HNO₃ (including HONO) in ambient air and δ¹⁵N-NO_x and δ¹⁵N-HNO₃ (including HONO) at the cow barn and roadside sites.

Fig. 4. Scatter plots between (a) δ¹⁵N-NH₄⁺ and air temperature, and (b) δ¹⁵N-NO₃^–and air temperature at Akita Prefectural University based on data from December 2009 to December 2010.

Table 2. Seasonal concentration (±S.D.) data for NO₂, HNO₃ and NO₃^–, the NO₂/HNO₃ and HNO₃/NO₃^– ratios, δ¹⁵N-NO_2, δ¹⁵N-NO₃, δ¹⁵N-NO₃^–, and the fractionations factors (ε) for NO₂ to HNO₃, HNO₃ to NO₃^–, and NO₂ to NO₃^– for samples collected at Akita Prefectural University from December 2009 to December 2010. HNO₃ is including HONO.

	NO2 (μg/m^3)	HNO3 (μg/m^3)	NO3^- (μg/m^3)	NO2/HNO3 (mol ratio)	HNO3/NO3^– (mol ratio)	δ^15N-NO2 (‰)	δ^15N-HNO3 (‰)	δ^15N-NO3^– (‰)	εNO2–HNO3 (‰)	εHNO3–NO3^– (‰)	εNO2–NO3^– (‰)
Spring	1.04 ± 0.63	0.60 ± 0.34	1.21 ± 0.64	2.3	0.5	–5.9 ± 1.1	–4.6 ± 0.7	–0.4 ± 1.6	+1.5 ± 1.1	+4.2 ± 1.0	+5.7 ± 1.0
Summer	3.18 ± 2.79	1.83 ± 0.52	0.63 ± 0.33	2.4	2.9	–6.6 ± 1.3	–6.2 ± 0.8	–2.5 ± 1.5	+0.2 ± 1.6	+3.8 ± 1.1	+4.0 ± 0.9
Autumn	0.56 ± 0.17	0.51 ± 0.24	0.77 ± 0.23	1.5	0.7	–4.5 ± 1.0	–5.7 ± 1.6	–1.0 ± 2.0	–1.6 ± 2.0	+5.5 ± 2.7	+3.9 ± 2.3
Winter	0.38 ± 0.18	0.34 ± 0.11	0.85 ± 0.35	1.5	0.4	–5.1 ± 1.8	–3.5 ± 3.9	3.1 ± 1.1	+1.6 ± 3.5	+6.4 ± 4.6	+8.0 ± 1.6
All seasons	1.27 ± 1.75	0.81 ± 0.67	0.86 ± 0.46	2.1	0.9	–5.4 ± 1.5	–5.0 ± 2.3	–0.5 ± 2.5	+0.5 ± 2.4	+4.9 ± 2.7	+5.4 ± 2.2