Rain samplers

Table VII Sampling and analysis precision for co-located rain samplers of Che Maple Leaf site (units = ppm unless Indicated)...

Figure 1. Location of rain samplers and urban cross-section of average elemental concentrations in rainwater.

The work reported here represents one aspect of an on-going study into the intra-urban distribution and sources of pollutants in urban precipitation. A dense network of bulk, wet-period and sequential rain samplers, along with intensity rain gauges are operating within the Hamilton area. 

Fig. 2A. Photograph of DOE/HASL Rain Sampler Fig. 2B. (Photo Courtesy of C. Hakkarinen)...

Canada, and Mexico (23). The National Atmospheric Deposition Program has established the nationwide sampling network of —100 stations in the United States. The sampler is shown in Fig. 14-9 with a wet collection container. The wet collection bucket is covered with a lid when it is not raining. A sensor for rain moves the lid to open the wet collector bucket and cover the dry bucket at the beginning of a rainstorm. This process is reversed when the rain stops. 

Pankow JF, Isabelle LM, Asher WE. 1984. Trace organic compounds in rain. 1. Sampler design and analysis by adsorption/thermal desorption (ATD). Environ Sci Technol 18 310-318. 

Factor Analyses. In an attempt to identify sources of the various elements, factor analyses were carried out separately on two data sets representing 1) filters exposed face down under an inverted funnel rain shield, and 2) filters exposed in a vane sampler continuously facing into the wind. Within each data set, separate factor analyses were performed on the data expressed as 1) concentrations in air (ng m ) and 2) abundances (percent of total mass). Rain amount, rain duration, and soil moisture data were included in early analyses, but these parameters were later dropped from the data sets because they had no significant relationship to any of the elements. Wind direction frequencies were included in the data sets throughout the analyses, however. 

Collecting a representative sample of snow for precipitation chemistry measurements poses special problems. Most electronic sensors on precipitation chemistry samplers do not detect snow, particularly light, dry snow, as efficiently as rain. Light, dry snow may also fall into and then be blown out of an open container or funnel. Snow may stick to sampler parts and later be blown into the sample container. Ice may coat sampler parts and prevent proper operation. Heavy snow may... 

Experimental Uncertainty from 10 Co-located Samplers Collected at one Control Site for Two Rain Events (Expressed as the average of two storms in stated units)... 

Field Operations. Each si e had four automatic precipitation collectors (Aerochem Metrics) and a Universal Recording Weighing Bucket Rain Gauge (Belfort) with an eight-day spring powered clock and strip chart recorder. An event pen marker was interfaced with the samplers and noted the sampler lid open and close times on the rain gauge strip chart. 

A known amount of distilled water was added to each sampler in the period when no rain was observed. At the end of each month, the sample solution was transferred into flexible polyethylene bottles and sent to the Meteorological Research Institute at Tsukuba Science City for analyses of the chemical components. 

Tropical storms, typhoons, or hurricanes, depending on their strength and geographical context, often deliver torrential rains. Increased river flow during such high intensity, low frequency rainfall events can transport a major portion of annual river N load to coastal systems. Historically, there has been a paucity of data on such events due to their irregular and extreme nature and the generally manual nature of water sample collection for nutrient analyses. However, with the use of in situ automatic water samplers and nutrient analysis systems, data from such events can now more readily be captured. 

Measurements using two samplers that had different upper range particle-size cutoffs indicated that during rain and fog the airborne salt shifts from aerosol-sized particles to droplets of approximately SO-jitm diameter (upper range of fog droplets) or greater. Consequently, the determination of the total concentration of atmospheric salt would require special sampling techniques to deal with both wet and dry particles of all sizes. 

The most widely used sampler in the United States networks today is comprised of two buckets, and a rain-activated switch to operate a movable cover. During non-precipitating periods, the cover remains tightly sealed on one bucket. Precipitation falling on the sensitive switch completes an electrical circuit activating a motor which lifts the cover from one side and places it on the opposite bucket. The sampler thus provides a dry sample as well as a wet sample. This is the standard instrument used throughout the NADP/NTN network. 

In each field, a rain-gauge was attached to one monitoring well to collect rainfall and irrigation water. The location of the wells and samplers in Fields 1-7 are shown in Figures 1 and 2. 

Either assemble your own collector or use a commercial self-contained unit. Place it 6 to 8 feet above ground and as clear of overhanging trees or structures as possible. However, all outside air samplers must be protected from rain, so it should be placed under some type of small cover. 

Marine aerosols are sampled for dust and salt by impingement of the aerosol particles onto nylon meshes 12). This dust-kite method (13, 14) uses a mesh with a strand diameter of 230/x and an air speed of approximately 15 knots. High-speed aerosol collectors 12) used on ships and aircraft employ meshes with strands of 48/a diameter and an air speed of 75-150 knots. Electron micrographs show that dust particles of 0.1 are collected by these high-speed samplers. To collect condensates (rain and fog) aboard ship, we have modified the shape of a dust kite so that the condensates will run to one point on the bottom and drop directly into a 1-liter polyethylene bottle. The system has collected up to 500 ml/hour in a fog of 0.5-mile visibility. 

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