Detailed descriptions can be found in Roadman et al. (2003). The Ogawa passive
samplers consist of a solid Teflon cylinder with two open but unconnected ends,
each containing a reactive glass fiber filter. The samples and two filters were
thoroughly cleaned prior to their use (to avoid contamination and carryover) and
then the two filters soaked by 3% H 3 PO 4 (v/v) for NH 3 and 25% (v/v)
triethanolamine for NO 2 (Yang et al. 2010a). Three replicate samplers were
deployed using a PVC rain shelter to avoid contamination from the rainfall and
dust. The assembly diagram of the Ogawa passive sampler can be found online at
http://ogawausa.com/wp-content/uploads/2014/04/assembly.pdf. Another passive
sampler (USDA Forest Service, CA, USA) was used for collecting atmospheric
nitrous acid/nitric acid [HNO 2 /HNO 3 ] samples (Bytnerowicz et al. 2005). Previous
comparative experiments also indicated that this sampler was reliable for determining wide ranges of ambient HNO 3 and HNO 2 (Jovan et al. 2012; Samie et al. 2007;
Elliott et al. 2009). This sampler has 47 mm diameter nylon filters (Magna,
Osmonics Inc.) as the collection medium for HNO 3 and HNO 2 . Prior to sampling,
the filters were soaked by 6% K 2 CO 3 (v/v) and 2% (v/v) glycerin. Samplers were
protected from wind, particulate, and rain by a cap (Teflon filter, Zefluor, Pall
Corporation, USA).
High-volume aerosol samplers (Laoshan Elec. Inc., Qingdao, China) were used to
collect total suspended particulates (TSP) at a flow rate of 1.05 m
3 min
À1 . This
sampler was deployed on the roof of an apartment close to the Lake Dianchi. Three
replicate samplers were installed at a height of 3.5 m and <50 m from the shoreline of
Lake Dianchi. After combustion for 4 h at 500
C in a muffle furnace, Whatman
QM-A quartz fiber filters were installed in the samplers. Passive samplers for
gaseous N were continuously exposed for 2 weeks. High-volume aerosol samplers
were noisy for adjacent residents, so we therefore had to shorten the continuously
running time, and the sampling was operated over 48 h every 2 weeks (Monday in
each week) and was manually halted during rainfall events by the staff of Kunming
Environmental Monitoring Center. The average of these 48-h samples is assumed to
represent the biweekly average concentration. The exposed samplers were placed in
the brown vial in refrigerator until analysis.
In addition, blank sampler from the same batch is applied for accurate results of
NH 3 , NO 2 , HNO 2 /HNO 3 , and particulate matter. Both field blanks (unexposed blank
sampler) and field samples (exposed samplers) in the same batch had the same coating
date (bought directly from Ogawa & Co., FL, USA), the same preparation date, the
same handling, and the same analysis date. For example, filters from the same batch
are assembled, exposed, and disassembled over some period of time defined by the
field study. The blank and field samplers are kept together except when the field
samplers are actively collecting air gases. The blank sampler is kept in the brown vial
or box (not exposed). When the sampling is completed, we place the exposed samplers
in the brown vial or box in refrigerator, until they are ready for analysis. The blank
samples were extracted and analyzed using the same methods as the exposed samples,
measured biweekly in the Kunming Environmental Monitoring Center.
At five deposition monitoring stations, wet deposition samples were taken manually on an event basis using a plexiglass bottle, along with precipitation measured
by tipping bucket rain gauge (WS-601, Guoxinhuayuan Tech. Inc., Beijing, China).
12 Impacts of Nitrogen Deposition on China’s Lake Ecosystems. . .
267
samplers consist of a solid Teflon cylinder with two open but unconnected ends,
each containing a reactive glass fiber filter. The samples and two filters were
thoroughly cleaned prior to their use (to avoid contamination and carryover) and
then the two filters soaked by 3% H 3 PO 4 (v/v) for NH 3 and 25% (v/v)
triethanolamine for NO 2 (Yang et al. 2010a). Three replicate samplers were
deployed using a PVC rain shelter to avoid contamination from the rainfall and
dust. The assembly diagram of the Ogawa passive sampler can be found online at
http://ogawausa.com/wp-content/uploads/2014/04/assembly.pdf. Another passive
sampler (USDA Forest Service, CA, USA) was used for collecting atmospheric
nitrous acid/nitric acid [HNO 2 /HNO 3 ] samples (Bytnerowicz et al. 2005). Previous
comparative experiments also indicated that this sampler was reliable for determining wide ranges of ambient HNO 3 and HNO 2 (Jovan et al. 2012; Samie et al. 2007;
Elliott et al. 2009). This sampler has 47 mm diameter nylon filters (Magna,
Osmonics Inc.) as the collection medium for HNO 3 and HNO 2 . Prior to sampling,
the filters were soaked by 6% K 2 CO 3 (v/v) and 2% (v/v) glycerin. Samplers were
protected from wind, particulate, and rain by a cap (Teflon filter, Zefluor, Pall
Corporation, USA).
High-volume aerosol samplers (Laoshan Elec. Inc., Qingdao, China) were used to
collect total suspended particulates (TSP) at a flow rate of 1.05 m
3 min
À1 . This
sampler was deployed on the roof of an apartment close to the Lake Dianchi. Three
replicate samplers were installed at a height of 3.5 m and <50 m from the shoreline of
Lake Dianchi. After combustion for 4 h at 500
C in a muffle furnace, Whatman
QM-A quartz fiber filters were installed in the samplers. Passive samplers for
gaseous N were continuously exposed for 2 weeks. High-volume aerosol samplers
were noisy for adjacent residents, so we therefore had to shorten the continuously
running time, and the sampling was operated over 48 h every 2 weeks (Monday in
each week) and was manually halted during rainfall events by the staff of Kunming
Environmental Monitoring Center. The average of these 48-h samples is assumed to
represent the biweekly average concentration. The exposed samplers were placed in
the brown vial in refrigerator until analysis.
In addition, blank sampler from the same batch is applied for accurate results of
NH 3 , NO 2 , HNO 2 /HNO 3 , and particulate matter. Both field blanks (unexposed blank
sampler) and field samples (exposed samplers) in the same batch had the same coating
date (bought directly from Ogawa & Co., FL, USA), the same preparation date, the
same handling, and the same analysis date. For example, filters from the same batch
are assembled, exposed, and disassembled over some period of time defined by the
field study. The blank and field samplers are kept together except when the field
samplers are actively collecting air gases. The blank sampler is kept in the brown vial
or box (not exposed). When the sampling is completed, we place the exposed samplers
in the brown vial or box in refrigerator, until they are ready for analysis. The blank
samples were extracted and analyzed using the same methods as the exposed samples,
measured biweekly in the Kunming Environmental Monitoring Center.
At five deposition monitoring stations, wet deposition samples were taken manually on an event basis using a plexiglass bottle, along with precipitation measured
by tipping bucket rain gauge (WS-601, Guoxinhuayuan Tech. Inc., Beijing, China).
12 Impacts of Nitrogen Deposition on China’s Lake Ecosystems. . .
267