From Wikipedia, the free encyclopedia
Jump to: navigation, search
WikiProject Physics (Rated B-class, Mid-importance)
WikiProject icon This article is within the scope of WikiProject Physics, a collaborative effort to improve the coverage of Physics on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.
B-Class article B  This article has been rated as B-Class on the project's quality scale.
 Mid  This article has been rated as Mid-importance on the project's importance scale.
WikiProject Meteorology  
WikiProject icon This article is within the scope of WikiProject Meteorology, a collaborative effort to improve the coverage of Meteorology on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.
 ???  This article has not yet received a rating on the project's quality scale.
 ???  This article has not yet received a rating on the project's importance scale.
WikiProject Environment (Rated B-class, High-importance)
WikiProject icon This environment-related article is part of the WikiProject Environment to improve Wikipedia's coverage of the environment. The aim is to write neutral and well-referenced articles on environment-related topics, as well as to ensure that environment articles are properly categorized.
Read Wikipedia:Contributing FAQ and leave any messages at the project talk page.
B-Class article B  This article has been rated as B-Class on the project's quality scale.
 High  This article has been rated as High-importance on the project's importance scale.

What is meant by the cryptic sentence fragment, "Sea salt does not absorb." ?[edit]

This says nothing intelligible. The thought should be completed by supplying the object -- what it is that sea salt does not absorb. Otherwise, the fragment should be removed. — Preceding unsigned comment added by Ocdnctx (talkcontribs) 20:40, 13 July 2012 (UTC)

I suspect it means light - the start of the paragraph mentions that dust is light absorbing. I will complete the sentance, but leave the reference needed. I think that the discussion of optical properties is probably better moved to the section on direct radiative effect which mentions Single scattering albedo. --NHSavage (talk) 15:12, 14 July 2012 (UTC)


It has been a while since I tried to do anything on this article. I am still not happy with the aerosol/particulate distinction. Given the industrial and medical importance of aerosols it seems odd that that article only refers to atmospheric aerosols. This article also mostly covers atmospheric particulates with some brief mention of others in the lead only. I would like to propose the following changes:

  1. Remove most of the information on atmospheric particulates from the aerosol article apart from a brief section with a link to this page as the Main section.
  2. Extend the aerosol article to mention the wide technological uses of aerosols
  3. Rename this article 'Atmospheric particulate matter' or if you insist 'Atmospheric particulates'.

--NHSavage (talk) 15:41, 14 July 2012 (UTC)

Some ideas for sections in the new aerosol page

  1. definition of an aerosol and also term like monodisperse, particle size distribution, number density etc
  2. atmospheric aerosols - with a short explanation of the rather subtle (in my opinion) distinction between aerosol and particulate matter and also the difference the usage of different communities - climate scientists almost always use aerosol while epidemiologists use
  3. aerosol generation e.g. spray cans etc
  4. aerosol applications - medical, industrial, consumer (spray cans)

Thoughts welcome. --NHSavage (talk) 06:32, 15 July 2012 (UTC)

I see that the last time this was proposed it failed because we did not know what the page should be redirected to. I think that the answer to this is that it doesn't need to be redirect but a disamabiguation page which consists of the first paragraph of the lead and then links to this article. and Total suspended solids for the water part.--NHSavage (talk) 06:53, 15 July 2012 (UTC)

Draft of how this page will look after the move is on a subpage at Particulates/draft. Comments and edits welcome. The biggest challenge will be sorting out the redirects etc and even more the foreign language wikipedias - some will need to go to one page and some to the other.--NHSavage (talk) 05:31, 20 July 2012 (UTC)

I propose to make this change on Saturday unless there is any other feedback in accordance with WP:BB.--NHSavage (talk) 19:39, 19 July 2012 (UTC)


I removed the following text from the section on regulation. The link it gives no longer works and if it was just daily monitoring data, it would not be useful as a reference of past concentrations. It also does not include any units. Daily average of 500 means nothing. (It's probably μg/m3 but I don't know). If someone can find a sourced reference for this, it might go in the affected areas part (which also needs a lot of work)

During November and December 2011, the values for particulate matter concentrations in Skopje, Macedonia have been record high, with daily average of 500. The values are taken from a page supported by the city authorities.[1]

--NHSavage (talk) 08:09, 11 August 2012 (UTC)

Proposed re-organisation[edit]

I am not happy with the current structure of this article and I would like to suggest the following sections:

First a lead which summarises all the content of the article and is not just a definition (although it needs to include a definition). Then:

  1. Definition (what is a particulate and how is it related to an aerosol, PM10, respirable fraction etc)
  2. Sources (natural and anthropogenic, including information on size and composition)
    1. Primary sources
    2. Secondary sources
  3. Atmospheric sinks (not including control technologies)
  4. Atmospheric concentrations (using material from Affected areas as a starting point)
  5. Impacts on human health
  6. Impacts on Ecosystems
  7. Climate impacts
  8. Regulation
  9. Control technologies

Thoughts anyone?--NHSavage (talk) 10:34, 11 August 2012 (UTC)

Dubious table[edit]

Most Polluted World Cities by PM[1]
Particulate matter,
μg/m3 (2004 and 2011)
508 Skopje, Macedonia
279 Ulaanbaatar, Mongolia
169 Cairo, Egypt
150 Delhi, India
128 Kolkata, India (Calcutta)
125 Tianjin, China
123 Chongqing, China
109 Kanpur, India
109 Lucknow, India
104 Jakarta, Indonesia
101 Shenyang, China

I have removed this table from the article for 2 reasons.

  1. Some of the entries in are not supported by the reference Skopje, Macedonia and Ulaanbaatar, Mongolia
  2. I don't think that the caption is actually correct. The source states: The data on concentrations of particulate matter are estimates, for selected cities, of average annual concentrations in residential areas away from air pollution “hotspots,”. This does not support them being used to create a list of "Most polluted cities by PM".
  3. The average is for a single year - even with fixed emissions, variations in weather can cause changes from year to year

--NHSavage (talk) 11:29, 11 August 2012 (UTC)

  1. ^ "Air pollution". World Bank. Retrieved 6 August 2012. 

Fairbanks designated non attainment for PM2.5[edit]

EPA designated Fairbanks, Alaska as a non-attainment area for PM2.5. It would be neat to see the map updated to reflect this. Currently only the PM10 map includes Alaska, with Eagle River shaded. — Preceding unsigned comment added by Sdegan (talkcontribs) 01:10, 30 May 2013 (UTC)

PM(2.5-10) and PM(2.5) exposure typical in the United States significantly associated with worse cognitive decline in older women.[edit]

Weuve J, Puett RC, Schwartz J, Yanosky JD, Laden F, Grodstein F.

Exposure to particulate air pollution and cognitive decline in older women.

Arch Intern Med. 2012 Feb 13;172(3):219-27. doi: 10.1001/archinternmed.2011.683.

An analysis of The Nurses' Health Study Cognitive Cohort, this study concluded:

Long-term exposure to PM(2.5-10) and PM(2.5) at levels typically experienced by many individuals in the United States is associated with significantly worse cognitive decline in older women.


PMCID: PMC3622279


PMID: 22332151


No Units on a chart? Are you kidding? This is something students learn in middle school. Put units on charts and graphs! JabberWok (talk) 03:26, 18 November 2013 (UTC)


Boys and girls - this is not a refereed journal, it's an encyclopedia. When I look up PM2.5, I expect to find out what the hell that means, not get into a discussion about what constitutes a "particle". PM is Particulate Matter? 2.5 is ... ? Inches? km? Is it even a size? Maybe it's how the particle tastes - 2.5 is raspberry and 10 is chocolate? --plaws (talk) 18:25, 25 April 2014 (UTC)

The article says micrometers. If you think the description can be improved, feel free to do it. — HHHIPPO 14:26, 26 April 2014 (UTC)

Requested move[edit]

The following discussion is an archived discussion of a requested move. Please do not modify it. Subsequent comments should be made in a new section on the talk page. Editors desiring to contest the closing decision should consider a move review. No further edits should be made to this section.

The result of the move request was: no consensus, much as it pains me to say it. I left this open for a fair while because it's clear that the current title is sub-par, but when deciding what to move it to I think both sides have made equally reasonable arguments and to split them would amount to a supervote. No prejudice against a new RM in the near-ish future because everyone seems to agree the current title is less than ideal. Jenks24 (talk) 06:57, 11 September 2014 (UTC)

ParticulatesAtmospheric particulate matter – The article, as written, is about atmospheric particulate matter. Particulates should be a disambiguation page similar to Particulate (disambiguation), as atmospheric particulate matter is not the primary topic of "Particulates", but rather one type of particulate matter. There is some related discussion at Talk:Particulate (disambiguation). Relisted. Jenks24 (talk) 07:51, 25 August 2014 (UTC) --Relisted. George Ho (talk) 05:59, 13 August 2014 (UTC) G. C. Hood (talk) 17:04, 3 August 2014 (UTC)

I disagree about the redirects. As Particle explains, a particulate is something that is composed of particles. Once the current content of Particulates is moved to Atmospheric particulate matter, Particulates and Particulate should redirect to Particulate (disambiguation). Particulate matter should redirect to Atmospheric particulate matter per WP:PRIMARYUSAGE, with a hatnote leading users to Particulate (disambiguation). G. C. Hood (talk) 17:57, 4 August 2014 (UTC)
  • Support, with no redirects as G. C. Hood indicates. Also pinging @BD2412: because he started a related RM back in 2012. Titoxd(?!? - cool stuff) 20:11, 4 August 2014 (UTC)
  • Support the rename, move Particulate (disambiguation) to Particulate, and anything that is not obviously Atmospheric particulate matter should go there (talk) 21:28, 4 August 2014 (UTC)
  • Support with redirects as suggest by G.C. Hood.--NHSavage (talk) 17:45, 5 August 2014 (UTC)
  • Please hang on until I get back from Wikimania. I'll be available on the 12th. The discussion can be relisted to remain open until then. Cheers! bd2412 T 12:27, 7 August 2014 (UTC)
  • Support per nom. "Particulate" fails to reflect the scope of this article, and is ambiguous with particle. --SmokeyJoe (talk) 11:27, 11 August 2014 (UTC)
  • I am concerned that we are not fully thinking through and plotting out the best solution here. Our goal is to help readers find the article that they are likely to be looking for when they search for or link to particulates. I would much rather get this done right than get it done quickly, particularly since the status quo has existed for about two years, and I am not aware of any complaints about it in that time. I have some questions about possible alternatives to moving this page, first and foremost being whether the current article can be expanded or adjusted to include both airborne and waterborne particulates (aside from the much more rarely discussed space debris, these appear to be the only important mediums in which particulates are carried). However, I have found some sources which distinguish these, only labeling airborne particles as particulates. For example:
The United States Environmental Protection Agency, on its website, defines "Particulate matter" also known as particle pollution or PM, as "a complex mixture of extremely small particles and liquid droplets. Particle pollution is made up of a number of components, including acids (such as nitrates and sulfates), organic chemicals, metals, and soil or dust particles."
Danny D. Reible, Fundamentals of Environmental Engineering (1998), p. 45: "Particulates are non-gaseous pollutants. We include in this category any substance that exists in the form of microscopic liquid or solid particles in the atmosphere. Dusts, smokes, mists, and aerosols are all different names for particulates." The same book, three pages later, has a section on "water pollutants" that does not refer to "particulates".
David E. Newton, Chemistry of the Environment (2009), p. 40: "Particulate matter is the term used to describe solid particles and liquid droplets found in the atmosphere." Later in the book, water pollution also does not refer to "particulates".
My Google Books search returns about 40,000 hits for "particulates", and 1,220 hits for the specific phrase "particulates in water". I would consider this a lack of evidence of anything other than air pollution being commonly referred to as Particulates, although I also think that a more appropriate title given the sources would be Particulate matter.
I also looked at page hits. If readers are arriving at this page but intending to find something else, they might follow the hatlink to the disambiguation page. In the last 90 days, however, Particulates has been viewed nearly 48,000 times, while the disambiguation page has been viewed 178 times, of which about one third happened in the few hours after this page was initially moved to a different title. In the same period, Total suspended solids was viewed about 15,000 times, but again there is little evidence that this term is considered synonymous with "particulates", and no evidence that editors are reaching that page after having searched for "particulates", and then gone through the disambiguation page.
Lastly, there is the question of ambiguity itself. I recently de-disambiguated Particulate pollution, and noted there that the EPA describes how the same particles can pass back and forth between water and air, being carried in the air and deposited in the water, and then returning to the air to form acid rain and the like. I wonder, do we need a separate page on particulate pollution at all if it is asserted that all particulates are polluting? Some of the literature (e.g. Newton, above) suggests that there can be natural particulates such as dust, smoke from forest fires, and airborne biogenics, but this is a distinction that can be covered in an article, just as Newton has succinctly covered it in his book chapter. Based on all of the foregoing, I propose that the optimal solution is to move the current title to Particulate matter, and move the current particulate pollution article to this title with some added material indicating that both natural and artificial particulates exist, with the latter constituting pollution. bd2412 T 19:14, 13 August 2014 (UTC)
I don't really like any of these options. I agree from when I tried to do some disambiguation on links to Particulate (disambiguation) ages ago, that most (but not all) of the links meant aerosol pollution in Earth's atmosphere. Some meant naturally formed aerosols in Earth's atmosphere. A secondary usage was particles suspended in water. The problem of ambiguity is due to the way people abuse this term. How about this: rename this page as per your suggestion to particulate matter. Redirect particulates, particulate, particulate pollution, atmospheric particulate matter to particulate matter. Add a hat note along the lines of This article is about particles suspended in the atmosphere. For particulate matter suspended in water see Suspended solids. I would ignore marine debris and space debris - neither article mentions particulates or any variant thereof. I would then delete Particulate (disambiguation). This article already mentions that there are natural sources of particulate. Are there any other redirects or pages I missed?--NHSavage (talk) 20:11, 13 August 2014 (UTC)
Oh one more thing - there is nothing in the EPA article cited by particulate pollution about particles evaporating from water. The point of the EPA article is that when particles settle on water, they can damage the water quality (or in the case of desert dust fertilize it, but that is another story). The particulate pollution is misleading to say Notably, some of the same kinds of particles can be suspended both in the air and in water, and pollutants specifically may be carried in the air and deposited in the water, or carried by water and transferred to the air through evaporation. If aerosols are water soluble, then when deposited to water, they will dissolve. If they are insoluble, then they will generally not evaporate again. There are two main sources of particulates from water bodies that I can think of sea salt generated mechanically, but there is such a large resevoir of salt that the re-deposition of sea salt in the oceans is a bit beside the point, and dimethyl sulfide which is produced by plankton and can then be oxidised to give sulfate aerosol. In neither case does a particle cycle back and forth as that article suggests. If I wasn't proposing its deletion, I'd want to change that statement.--NHSavage (talk) 20:30, 13 August 2014 (UTC)
Oh I missed Colloidal particle - I would just redirect this to Colloid.--NHSavage (talk) 20:36, 13 August 2014 (UTC)
I support this alternative solution. With respect to evaporation, I was thinking of the reference to acid rain, since rain forms from evaporation. In retrospect, though , rain can obviously incorporate atmospheric pollutants. bd2412 T 21:18, 13 August 2014 (UTC)
A smoothing of 50 misleadingly, falsely, suggests a strong ongoing trend. It doesn't allow the graph to reflect the increase followed by decrease.
Prior to the 1970s, there was little discussion of particles in the atmosphere, "particulate" was barely used at all, water particulates was a mature field, and written discourse on atmospheric pollution was yet to explode. So yes, since 1980, particulate is associated with air more often than water, but it is not 10-tenfold in recent years, and the ratio is in decline. Particulate continues to be used in terms of water solids, and remains very important, even if there is less ongoing need for new books to be written about it. This article needs a more precise title. --SmokeyJoe (talk) 01:47, 14 August 2014 (UTC)
Smoothing the results avoids a slavish adherence to microtrends. Our readers may just as well be reading books from the 1970s or 1980s when they come upon the term they wish to search as books from today. However, even using a smoothing of 1, it is clear that air and atmospheric references continue to outnumber water references several times over, far more than the "all the other topics combined" threshold by which we determine the primary topic of a term. bd2412 T 02:06, 14 August 2014 (UTC)
Yes, agreed that ngram evidence indicates that atmospheric usage outnumbers water usage several times. That's a worthy point, but I think it is diminished because atmospheric references are amplified by the recentism of interest in atmospheric pollution, even to the point of tabloid sensationalism, while water pollution because a boring known science decades ago. I suggest that this bias is influenced by wealthy book writers having easy access to clean water, but breathing the common air, and that such biases should be resisted. "Particulate" does not necessarily imply "atmospheric particulate".
Above, you support an alternative solution with NHSavage. Can that alternative solution be clarified please? --SmokeyJoe (talk) 03:52, 14 August 2014 (UTC)
I have only ever seen recentism raised as an issue in disambiguation discussions where one term was much, much older than the other. Here, it seems that "particulates" has referred to those in both air and water for about the same amount of time, and that reference to those in the atmosphere has predominated not just for a the past few years but consistently over decades. The alternative solution proposed by NHSavage is to move this page to Particulate matter; then redirect particulate, particulates, particulate pollution, and atmospheric particulate matter to Particulate matter; and then put a hatnote on that page pointing to suspensions in water. bd2412 T 12:48, 14 August 2014 (UTC)
  • Relisting comment. Would like some of the people who voted in support earlier to give their opinion on the alternative option that seems to be supported by BD2412 and NHSavage. Pinging G. C. Hood, Titoxd and SmokeyJoe. Jenks24 (talk) 07:51, 25 August 2014 (UTC)
I continue to support the move, usage statistics notwithstanding because introductory usage of particulate matter seems to always be in the context of the atmosphere, and/or to have followed use of the word "aerosol". As a Wikipedia article title, neither is true. "Atmospheric" is required because the particulates covered by this article are limited to particulates in the atmosphere, and many important particulates do not pertain to the atmosphere. Definitely support "Atmospheric particulate matter" over the current. Atmospheric particulates may be superior, because "particulate" implies matter, there are no immaterial particulates in the atmosphere. --SmokeyJoe (talk) 05:21, 26 August 2014 (UTC)
After googling these terms, and reading what returns, I think Atmospheric particulates is far superior a title to Particulate matter. The first is overwhelmingly more frequently used in an introductory sense in scholarly sources. the contrast with google ngram tells me that google ngram is not to be relied upon for titling decisions. --SmokeyJoe (talk) 05:27, 26 August 2014 (UTC)
Since you have done the research, would you agree at this point that most references to "particulates" intend atmospheric particulates? If the only other significant form of particulate is water-borne particulates, we can resolve all of this with a redirect and a hatnote. bd2412 T 13:46, 26 August 2014 (UTC)
That "most references to "particulates" intend atmospheric particulates?". No, I would not agree to that wording. Instead, I would say "most recurring usage of the word "particulates" is in reference to atmospheric particulates". Once the context of the atmosphere is established, "particulates" can only refer to atmospheric particulates. However, at the level of the title, the context of the atmosphere is not established.
"Significant" is a troublesome word, having different meanings opposite to each other. Discussion of atmospheric particulates dominates 5-10 fold. The overwhelming count of the remainder relates to particulates in water. Use of particulate elsewhere, such as low orbit space, cosmology (where it seems to mean undefinded particles, not elemental or plasma) and materials (a particulate solid is composed of finer parts than a conglomerate), are all important but not frequent. But none of this line of thinking goes to the question of how a stand-alone document, such as a Wikipedia article, should be titled. Without "Atmospheric (or similar), the title does not precisely define the scope of the article. A hatnote is not sufficient to correct a title that ignores other important uses of the word. --SmokeyJoe (talk) 00:21, 27 August 2014 (UTC)
I agree that Atmospheric particulates is far better than both Atmospheric particulate matter and Particulate matter. The word "particulate" already implies "matter" (what else could it be in this context?), so that latter is just a redundant term.
Also, I am strongly against assuming that all "particulates" are in the atmosphere; presence of them in water (e.g. finely-divided plastic particles) and in other contexts is increasingly under study (e.g. soil contamination, biomass and seafood contamination). Conflating all "particulates" with "atmospheric particulates" is only going to result in more confused writing, confused readers, and time-wasting disputes over the coming years. Let's resolve this clearly now, and resume working on improving the content. Reify-tech (talk) 15:45, 26 August 2014 (UTC)
What, then, do we do about the WP:DABCONCEPT problem? There may be different kinds of particulates, but that makes them related subtopics, not ambiguous terms. bd2412 T 16:21, 26 August 2014 (UTC)
It's not so much a group of related topics, as a group of topics with one common intrinsic physical characteristic, connected by use of a common word. --SmokeyJoe (talk) 00:21, 27 August 2014 (UTC)
It is the "common intrinsic physical characteristic" that makes them related. They are all only called "particulates" because they share the characteristic of the particulate form. This is what makes it a WP:DABCONCEPT, because it is possible to explain that relationship. Perhaps a set index is in order, although I think a primary topic would be more informative to the average reader. bd2412 T 20:33, 9 September 2014 (UTC)
"It is the "common intrinsic physical characteristic" that makes them related." Yes. This could be well explained in a DABCONCEPT page at "particulate", or "particulate matter" (the first is an adjective, "particulates" is informal). Particulates are usually grains, dust, solid/liquid mixtures, larger and more complicated that particles, which include atoms, electrons, oxygen molecules. Is a water droplet a particulate?
"They are all only called "particulates" because they share the characteristic of the particulate form." No. "Particulate" is a persisting 1960s neologism coined and used to distinguish particulates from particles, used for convenience, not used in a serious treatment of the particulates themselves. When soot is called a particulate, it is not in a study of the structure of soot. (I wish I had handy access to the oed, by far the best source for this stuff) There is usage of the word 100 years preceding, but I believe that this was usage as adjective for the composition of materials, between pure and conglomerate, as in "concrete is a particulate material", "steel is not a particulate material". --SmokeyJoe (talk) 00:32, 10 September 2014 (UTC)
If you have sources for this, then you have the basis for an article explaining what particulates (as an informal designation) are. We do have articles discussing the use of amorphously described concepts. They are difficult to write, but are particularly useful for readers like me, who would otherwise generally be under the impression that these concepts were well defines and cleanly delineated. There is, apparently, a history of use here that goes beyond mere etymology. bd2412 T 00:40, 10 September 2014 (UTC)

Related moves[edit]

The above discussion is preserved as an archive of a requested move. Please do not modify it. Subsequent comments should be made in a new section on this talk page or in a move review. No further edits should be made to this section.

Mammoth captions[edit]

This article has some monster captions that far outweigh the graphics they are attached to. The massive text blocks in small print are nearly indigestible to non-specialist readers. It would be better to explain the pictures in ordinary text, with headings, paragraph breaks, references, and other readability accommodations for non-obsessive readers. The caption should concisely summarize what the picture shows, and refer to a nearby text explaining all the details for a reader wishing to delve into them. As it stands now, it is difficult to even discern what the pictures are supposed to show. Reify-tech (talk) 19:00, 12 August 2014 (UTC)

I have reformatted those captions to make them more legible. I have extracted some matter from them into a new section Particulates#Size distribution of particulates. Anthony Appleyard (talk) 04:34, 15 August 2014 (UTC)
Thank you for trimming the captions and moving much of the explanation details to the main text. It is now noticeably easier to figure out what the images are showing. As a further improvement, I suggest that the image sourcing details be moved to the end of the captions, or still better, into the main text. Concerned readers can always find full details about any Wikipedia image's sourcing, with a couple of clicks. The general reader needs to see quickly what an image is about; questions about sourcing and methodologies only emerge later, after the reader is drawn into the meaning of the image. Reify-tech (talk) 16:10, 26 August 2014 (UTC)

Lead sentence and grammar[edit]

The lead sentence is currently:

"Atmospheric particulate matter – also known as particulate matter (PM) or particulates – are particles of solid or liquid matter suspended in the Earth's atmosphere as atmospheric aerosol, a term which refers to the particulate/air mixture, as opposed to the particulate matter alone."

Please can we amend it to something grammatical: at present it's saying "Atmospheric particulate matter are particles...", when you remove the parenthesis: a singular subject with a plural verb.

As the article title is "Particulates" I suggest:

(Option 1) Particulates – also known as atmospheric particulate matter or particulate matter (PM) – are particles of solid or liquid matter ... "

Or, if there's consensus for keeping the order of the terms as is, then:

(Option 2)  :"Atmospheric particulate matter – also known as particulate matter (PM) or particulates – comprises particles of solid or liquid matter ... "

Or, for those who prefer simple language:

(Option 3)  :"Atmospheric particulate matter – also known as particulate matter (PM) or particulates – is particles of solid or liquid matter ... "

or (4)"consists of", (5)"is made up of", various other terms - anything to ensure that we have a leade sentence which doesn't jar the reader by having a disagreement in number between the subject and the verb. PamD 08:02, 10 September 2014 (UTC)