Review of the Air Quality Criteria Document for Particulate Matter

ecosystems are. There are a host of papers that address this issue and at least some should becited.8. In looking at PM per se, it is interesting to note that the chapter fails to mention to onetype of ecosystem for which deposition of PM is likely to be very important – urban andsuburban forests (largely in parks). There is a great deal of literature on these systems. In fact, itmight be best to replace the current discussion of deposition to the IFS sites and replace thatmaterial with the urban suburban forest analysis.Specific Issues1. There is little reason to consider in much depth the consequences of PM on vegetationand ecosystems. In fact, most of the material in Chapter 4 characterizing the effects onvegetation and ecosystems could be reduced by 50% or more. Much of the informationis appropriate to other documents (e.g., deposition of sulfur and nitrogen) but is onlytangentially (at best) related to PM and the standard setting process.2. The discussion of wet and dry deposition on ecosystem processes is largely a function ofresearch conducted in the east where precipitation is the major mode of deposition. Inthe western US, dry processes are far more important as a vector for deposition. It isrecommended that the research in the West be given some parity in the discussionassuming that the discussion of deposition remains. In light of No. 1 (above), this issuemay be moot.3. The discussion of direct effects of PM on vegetation (4.2.1) is appropriate to thisdocument but has no relevance to the standard setting process since effects are seen atlevels well above ambient rates of deposition. This section could be reduced in length by75% or more.4. The discussion of the consequences of nitrogen input to ecosystems (4.2.1.2) is hard tojustify in the depth presented. If it is important to include, it is recommended that thedissimilarity between the eastern and western US be highlighted.5. The same concern for sulfur is appropriate. The detail is only tangentially related to theissue of PM and the deposition is unlikely to be of consequence.6. On page 4-22, reference is made to the fact that ecosystem level responses to stress beginat the population level. I am not quite sure that is accurate.7. On page 4-24, the following statement is offered, “In contrast, anthropogenic stressesusually are severe, debilitating stresses”. I find it difficult to agree with this statement.In the same paragraph, the four categories of stresses seem to be awkward. Where wouldnitrogen deposition or CO2 increase fall in this scheme?8. On page 4-25, reference is made to the concept of secondary succession and chronicstresses. The concept of secondary succession as presented is not accurate and the syntaxof those sentences is not accurate. The entire process of secondary succession is a datedconcept in ecology and its relevance here is marginal.9. On page 4-26, the comment is made that it is difficult to determine responses ofecosystems to stress. As a blanket statement, this is simply not accurate. Maybe themagnitude of the response is not known with certainty but the direction and many of thechanges are known with certainty.10. The section on particulate matter, atmospheric turbidity and effects on vegetationprocesses (page 4-34) is weak from a cause-effect perspective. This could be deleted.11. Is the section on solar UV radiation (p4-39) needed in this document? The argument istenuous.12. The conclusion paragraph (4-84) is too bold a statement regarding the effects. The leadshould be less alarmist and simply state that there is little reason to address secondaryeffects of PM on vegetation and ecosystem processes. It is important to be accurate,particularly in the summary sections.13. On pages 4-113, the work of Chestnut and Davis is presented on the willingness to payfor visibility. It is important that the results and conclusions of the authors be reportedrather than simply that they conducted a study.14. If one is discussing nitrogen and sulfur in the PM document, then all of the otherA - 79