Maxxam all-season passive sampling system (PASS) is introduced in this paper. The PASS can be used to quantitatively and accurately monitor SO2 , NO2, O 3, and H2 S in air in all weather conditions with flexible exposure times from several hours to several months. The air pollution detection limits of PASS are very low. They can be from sub ppb to ppt levels. The principles of proper use of passive samplers in the field study are discussed by using the PASS as an example.

Hongmao Tang

Introduction to Maxxam All-Season Passive Sampling System and Principles of Proper Use of Passive Samplers in the Field Study

Measurement of ionic deposition in throughfall is a widely used method for measuring deposition inputs to the forest floor. Many studies have been published, providing a large database of throughfall deposition inputs to forests. However, throughfall collection and analysis is labor intensive and expensive because of the large number of replicate collectors needed and because sample collection and chemical analyses are required on a stochastic precipitation event-based schedule. Therefore we developed and tested a throughfall collector system using a mixed bed ion exchange resin column. We anticipate that this method will typically require only one to three samplings per year. With this method, bulk deposition and bulk throughfall are collected by a funnel or snow tube and ions are retained as the solution percolates through the resin column. Ions retained by the resin are then extracted in the same column with 2N KCl and analyzed for nitrate and ammonium. Deposition values in throughfall from conventional throughfall solution collectors and colocated ion exchange samplers were not significantly different during consecutive 3- and 4-month exposure periods at a high (Camp Paivika; &#x3E;35 kg N ha-1 year-1) and a low deposition (Barton Flats; 5&#x2013;9 kg N ha-1 year-1) site in the San Bernardino Mountains in southern California. N deposition in throughfall under mature pine trees at Camp Paivika after 7 months of exposure was extremely high (87 and 92 kg ha-1 based on the two collector types) compared to Barton Flats (11 and 13 kg ha-1). A large proportion of the N deposited in throughfall at Camp Paivika occurred as fog drip, demonstrating the importance of fog deposition as an input source of N at this site. By comparison, bulk deposition rates in open areas were 5.1 and 5.4 kg ha-1 at Camp Paivika based on the two collector types, and 1.9 and 3.0 kg ha-1 at Barton Flats.

Mark E. Fenn

Mark A. Poth

Michael J. Arbaugh

A Throughfall Collection Method Using Mixed Bed Ion Exchange Resin Columns

Passive samplers (diffusion tubes with organic reagent, produced by Passam of Switzerland) were used in a sampling campaign for the detection of weekly mean ozone concentrations in 15 sites over a domain of 80 x 40 km on the southern side of the European Alps from May to August 1998. The area is characterized by vast natural terrain of complex topography, with conifer and broadleaf forests. It is difficult to access and monitor air quality there with continuous analysers. By applying geostatistical techniques (ordinary kriging), and correcting the interpolated ozone concentrations according to the altitude of each single grid cell (2 x 2 km), maps of weekly ozone concentrations were produced. The weekly ozone data were used to assess daily and hourly data by means of an iterative procedure based on a functional dependence of ozone concentrations both on altitude and on the time of day. This allowed the estimation of values with an exposure index such as AOT40 (accumulated exposure over the threshold of 40 ppb) in all 800 cells of the domain. This also allowed the mapping of risk assessment related to the effects of ozone on the regional forest vegetation. Results obtained show values that exceed the exposure standards adopted in the Kuopio protocol (1996). Excess exposure values also match values calculated over a wider territorial domain by using hourly data on ozone concentration derived from continuous automatic analysers.

Cristina Mazzali

Elisabetta Angelino

Giacomo Gerosa

Antonio Ballarin-Denti

Ozone Risk Assessment and Mapping in the Alps Based on Data from Passive Samplers

Passive samplers are useful tools for helping to describe the ozone distribution in complex terrain situations. They are also a good complement to continuous monitoring stations. This paper discusses the results of a pilot study that used ozone passive samplers to describe the spatial and annual temporal distribution of ozone in several forested areas around the city of Madrid. The ozone concentrations around Madrid were found to be higher on the elevated sites located at a certain distance from the city�s urban zone. A seasonal ozone cycle was observed, with maximum concentrations found in the basin in late spring or summer depending on the location. The information obtained allowed us to group the locations into four classes. Altitude and distance to the city during the summer and winter explained the observed ozone concentrations. However, during the transition periods, especially in early spring and to a lesser extent in autumn, there was not a good correlation between ozone levels and elevation or distance from precursor sources. These data strongly suggest that altitudinal gradients for ozone are not always the case in the Madrid Basin.

M.J. Sanz

F. Sanz

G. Sanchez-Peaa

Spatial and Annual Temporal Distribution of Ozone Concentrations in the Madrid Basin Using Passive Samplers

The National Park Service (NPS) has tested and used passive ozone samplers for several years to get baseline values for parks and to determine the spatial variability within parks. Experience has shown that the Ogawa passive samplers can provide &#xb1;10% accuracy when used with a quality assurance program consisting of blanks, duplicates, collocated instrumentation, and a standard operating procedure that carefully guides site operators. Although the passive device does not meet EPA criteria as a certified method (mainly, that hourly values be measured), it does provide seasonal summed values of ozone. The seasonal ozone concentrations from the passive devices can be compared to other monitoring to determine baseline values, trends, and spatial variations. This point is illustrated with some kriged interpolation maps of ozone statistics. Passive ozone samplers were used to get elevational gradients and spatial distributions of ozone within a park. This was done in varying degrees at Mount Rainier, Olympic, Sequoia&#x2013;Kings Canyon, Yosemite, Joshua Tree, Rocky Mountain, and Great Smoky Mountains national parks. The ozone has been found to vary by factors of 2 and 3 within a park when average ozone is compared between locations. Specific examples of the spatial distributions of ozone in three parks within California are given using interpolation maps. Positive aspects and limitations of the passive sampling approach are presented.

John D. Ray

Spatial Distribution of Tropospheric Ozone in National Parks of California: Interpretation of Passive-Sampler Data

Information about spatial and temporal distribution of air pollutants is essential for better understanding of environmental stresses affecting forests and estimation of potential risks associated with air pollutants. Ozone and nitrogenous air pollutants were monitored along an elevation gradient in the Class I San Gorgonio Wilderness area (San Bernardino Mountains, California, U.S.) during the summer of 2000 (mid-June to mid-October). Passive samplers were exposed for 2-week periods at six sampling sites located at 300 m intervals ranging from 1200 to 2700 m elevation. Elevated concentrations of ozone were found in this area with summer 24-h hourly means ranging from 53 to 59 ppb. The highest ozone concentrations were detected in the period July 25 to August 8, reaching values of 64 to 72 ppb expressed as 2-week mean. Passive-sampler ozone data did not show a clear relationship with elevation, although during the periods with higher ozone levels, ozone concentrations were higher at those sites below 2000 m than at sites located above that elevation. All nitrogenous pollutants studied showed a consistent decrease of concentrations with elevation. Nitrogen dioxide (NO2) levels were low, decreasing with increasing elevation from 6.4 to 1.5 ppb summer means. Nitric oxide (NO) concentrations were around 1 to 2 ppb, which is within the range of the detection levels of the devices used. Nitric acid (HNO3) vapor concentrations were lower at higher elevations (summer means 1.9 to 2.5 &#x3BC;g m-3) than at lower elevations (summer means 4.3 to 5.1 &#x3BC;g m-3). Summer concentrations of ammonia (NH3) were slightly higher than nitric acid ranging from 6 &#x3BC;g m-3 at the lowest site to 2.5 &#x3BC;g m-3 registered at the highest elevation. Since complex interactions between ozone and nitrogenous air pollutants have already been described for forests, simultaneous information about the distribution of these pollutants is needed. This is particularly important in mountain terrain where no reliable models of air pollutant distribution exist.

Rocio Alonso

Andrzej Bytnerowicz

Michael Arbaugh

Vertical Distribution of Ozone and Nitrogenous Pollutants in an Air Quality Class I Area, the San Gorgonio Wilderness, Southern California

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