BS EN 15853-2010 pdf download.Ambient air quality Standard method for the determination of mercury deposition.
7 Sampling
7.1 Sampling equipment — General requirements
Use collectors with a defined horizontal opening, either a funnel/bottle combination (see A.1 and A.3) or a wide-mouthed jar (see A.2). The collectOrs can be bulk samplers, which collect at all times, or wet-only samplers which collect only during wet precipitation events.
If a funnel/bottle collector is used, the funnel shall have a cylindrical vertical section of sufficient height to avoid sampling losses resulting from splashing. If a jar is used, it shall have a sufficient depth to avoid such sampling losses.
Collector dimensions shall be selected with respect to the expected precipitation collected in the sampling period used. Typical sampling periods vary between one week and one month. The funnel area shall be large enough to provide sufficient sample for chemical analysis at a minimum precipitation depth of 1 mm per week.
It is recommended that short sampling periods (weekly) and/or two or three samplers in parallel are used.
The sampling efficiency of funnel/bottle collectors can be checked by comparing the collected precipitation with the precipitation determined using a standard meteorological rain gauge. The difference in precipitation between the standard rain gauge and the heavy metal sample collector shall not be greater than 20 % for precipitation depths between 1 mm to 2,5 mm, and not greater than 10 % for precipitation depths larger than 2,5 mm of precipitation (9). Checking sampling efficiency is especially important if a wet-only collector is used.
Mercury deposition is collected in special precipitation samplers, which are used only for mercury deposition determinations. All parts of the precipitation collector that are in contact with the sample shall consist of materials that do not alter the mercury content of the sample (e.g. glass. fluorocarbon polymers). Also, all parts of the sampling collectors shall be easy to clean,
In order for the sample not to be contaminated during heavy rain, the rim of the funnel shall be positioned 1,5 m to 2,0 m above the ground level.
NOTE Sample contamination can be caused by insects, bird droppings or other matenal in the sampling vessels, especially when using extended sampling periods. This is a major drawback to bulk sampling.
For extended sampling periods — especially if HCI is used to preserve the sample during exposure — it is necessary to prevent the diffusion of Hg° into the precipitation sample collected, since it could contribute to the mercury content of the sample via oxidation to water-soluble forms. For funnel/bottle collectors this can be done easily by using a capillary tube between the funnel and the bottle.
It is also necessary to shield the sample bottles from light to avoid photo-induced reduction of the mercury in the precipitation sample.
If a funnellbottle collector with capillary tube is used, add HCI (6.1 or 6.5) to the sampling bottle before exposure in order to stabilize the sample (see 7.3). Do not add acid. if an open jar is used for sampling.
Samplers shall be suitable for all seasons and all climatic conditions. Thus, especially for wet-only collectors, a heating device should be Included to melt snow and to prevent the formation of ice in the funnel and bottle during winter. Otherwise, for bulk collectors, an extra large and deep cylindrical jar should be used for snow sampling. It can be useful to cool the samples in locations where high temperatures are expected during summer.
7.2 Sampling equipment — Special requirements for different collector types
7.2.1 Bulk collector: Funnel/bottle combination
Sampling equipment as described in A.1 can be used for sampling.
If a bird ring Is needed, it shall be covered by a suitable inert material, e.g. polyethylene. In order to prevent insects, leaves, etc. from entering the collection bottle a sieve made of e.g. polycarbonate can be used. The sieve shall not obstruct the funnel neck.
Funnel/bottle combination bulk collectors can be used at all types of sampling sites.
7.2.2 Bulk collector: Wide-mouthed jar
Sampling equipment as described In A.2 can be used for sampling. If a bird ring is needed, it shall be covered
by a suitable inert material, e.g. polyethylene.
Wide-mouthed jar bulk collectors can be used at all types of sampling sites
7.2.3 Wet-only collector: Funnellbottle combination
Sampling equipment as described in A.3 can be used for sampling.
Wet only collectors are equipped with an automabc lid, which opens after activation of a precipitation sensor. The sensitivity of the sensor might affect the sampling efficiency. A precipitation of 0,05 mm/h shall be sufficient for the lid opening mechanism to be activated.
Wet-only collectors can be used at all types of sampling sites.
NOTE Especially at industrial sites or at costal sites, corrosion by e.g. reactive gases or sea salts can occur to
precipitation sensors based on measuring the electrical conductivity. At such sites it can be useful to use ophcal sensors.
7.3 Preparation of precipitation collectors.BS EN 15853-2010 pdf download.