Gaseous concentration of nitrogen dioxide (NO2) and ammonia (NH3) was measured at Site A of the Main Experiment for a period of 55 months (May 2010 - November 2014) for estimating dry deposition of nitrogen. Passive sampling tubes (www.passam.ch) were used to quantify NO2 and NH3 concentration.

Gaseous concentration of nitrogen dioxide (NO2) and ammonia (NH3) was measured in Xingangshan (Main Experiment Site A) for a period of 55 months (May 2010 - November 2014) for estimating dry deposition of nitrogen. Commercial passive sampling tubes (www.passam.ch) were used to quantify NO2 and NH3 concentration.The sampling tubes have been exposed continuously and replaced every month. Passive sampling tubes for NO2 and NH3 have been installed at a height of 1.5 m attached to a wooden pole placed next to the climate station at Site A. NO2 measurement principle: "The sampler is based on that of Palmes and is a passive device requiring no power for its operation. It collects NO2 by molecular diffusion along an inert tube to an absorbent, in this case triethanolamine. The collected NO2 is determined spectrophotometrically by the well-established Saltzmann method. The samplers are placed in a special shelter to protect them from rain and minimize the wind influence." NO2-detection limit: 0.3 microgramPercubicmeter for one month exposure in the field. NH3 measurement principle: "The diffusive sampler for ammonia collects gaseous ammonia by absorption on phosphoric acid. The amount of ammonia is determined spectrophotometrically by the indophenol method.The passive samplers are composed of a polypropylene housing with an opening of 20 mm diameter. To reduce wind disturbance a teflon membrane is attached, supported by a wire net. To protect the sampler from weather influences, as well as minimising wind disturbance, a protective shelter has to be used." NH3-detection limit: 0.3 microgramPercubicmeter for one month exposure in the field.

Xingangshan: Main Experiment: Site A: Climate station

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Due to change of workers and worker availability passive samplers could not be exposed in the field in some months.