No breath­ing easy in Toko­roa just yet

South Waikato News - - NEWS - By ADEN MILES

A Waikato Re­gional Coun­cil of­fi­cial has told South Waikato District Coun­cil­lors that he found no ev­i­dence to sug­gest air qual­ity in Toko­roa is get­ting bet­ter or worse.

The mes­sage came from WRC’s En­vi­ron­men­tal chemist Jonathan Cald­well who pre­sented his find­ings us­ing Pear­son’s Cor­re­la­tion Method and the Sea­sonal Mann- Ken­dall Anal­y­sis of air qual­ity in the South Waikato, notably Toko­roa.

Dur­ing last week’s Cor­po­rate and En­vi­ron­ment Com­mit­tee meet­ing Mr Cald­well said mon­i­tor­ing data shows 15 ex­ceedances in Toko­roa this year, on a par with pre­vi­ous years.

‘‘ If we av­er­age the PM10 con­cen­tra­tions over a year, we are look­ing at 18 mi­cro­grams per cu­bic me­tre, which is quite con­sis­tent with pre­vi­ous years.’’

There is a guide­line of an­nual mea­sures of 20 mi­cro­grams.

‘‘So we are track­ing be­low the an­nual av­er­age guide­line. But it is still up there. The max­i­mum read­ings do seem to have come down a lit­tle bit in the last cou­ple of years that may in­di­cate to you per­haps that things might be im­prov­ing.’’

Mr Cald­well used the sta­tis­ti­cal data to de­ter­mine whether there are trends de­vel­op­ing.

‘‘ Pear­son’s Cor­re­la­tion Method . . . is where we looked at some key sum­mary statis­tics, changes in the an­nual av­er­ages per year. From sta­tis­ti­cal anal­y­sis us­ing Pear­son’s Cor­re­la­tion there is no ev­i­dence that the air qual­ity is get­ting bet­ter or worse.’’

The Sea­sonal Mann-Ken­dall test was sub­se­quently used and came to the same con­clu­sion.

Coun­cil­lor Her­man van Rooi­jen ques­tioned whether the test con­sid­ered weather con­di­tions.

‘‘One thing we have looked at [is] that nine per cent of the time when there has been ex­ceedances we’ve had cool tem­per­a­tures be­low 12 de­grees [day time tem­per­a­tures] and also wind speeds be­low two me­tres per sec­ond,’’ Mr Cald­well said.

The Emis­sions In­ven­tory Sys­tem also re­vealed 93 per cent of PM10 emis­sions in 2012 were a re­sult of domestic heat­ing ap­pli­ances.

‘‘The mon­i­tor­ing data shows what’s ac­tu­ally hap­pen­ing with PM10 in the air, so we are mon­i­tor­ing the con­cen­tra­tions of PM10. All the Emis­sion In­ven­tory shows is how many kilo­grams of PM10 are emit­ted from wood burn­ers, how much is likely to be from in­dus­try and how much is likely to be emit­ted from ve­hi­cles.’’

Air dis­per­sion and how PM10 is dis­persed in the air will have an af­fect on how the air qual­ity is, Mr Cald­well said.

‘‘ So one kilo­gram of PM10 emit­ted from a wood burner will be dis­persed quite dif­fer­ently from one kilo­gram dis­persed from the in­dus­try where you get a much bet­ter dis­per­sion.’’

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