| 英文摘要 |
The main goal of this project is to develop a plan for the collocation comparison of continuously sampling PM2.5 and PM10 air quality monitors in order to validate their performance. A database of PM10 and PM2.5 monitors is also planned in support of this objective. Another task is to enhance the performance quality of the flow and ozone calibration system maintained by the EPA quality assurance laboratory of air quality network.
The current reference method for measuring mass concentration of particulate matter in ambient air relies on a 24-hour collection period followed by gravimetric analysis. Continuous automated monitors provide concentration distribution data at an increased time resolution to allow for pollution tracing in monitoring networks. As these machines rely on continuous readings, it is necessary to demonstrate that these automated instruments can produce results, such as 24-hour average value, that are comparable with the reference method. This is mainly done by executing collocated comparisons between reference and automated monitors.
Three comparison platforms are distributed with one in each of the following; Taipei City, Tainan City, and Kaohsiung City. Each platform can contain a maximum number of eighteen automatic monitors. Currently, three manual samplers operated according to the reference method can be deployed for equivalent comparison. These comparison platforms allow for the stability and precision of automatic monitors to be tested and ensure that the automatic monitor’s results are equivalent to that of the reference method. After ensuring that these conditions are met, the automatic monitors can be distributed to different air quality monitoring stations and can be used to evaluate air quality.
In 2018, three platforms are applied to test the performance of newly purchased PM10 monitors. After, qualified monitors are deployed to various monitoring stations to replace aged monitors and the data from both the new and old monitors are compared. After this comparison, a significant difference was found in stations located in southern Taiwan. However, zero point tests of new monitors to evaluate the detection limit (DL) showed that the DL for 24-hr is 2 μg/m3 and DL for one-hr is 5 μg/m3, which is consistent to what has been reported in Europe.
PM2.5 monitors deployed in Kaohsiung and Taipei comparison platforms are recognized as transfer reference instruments (TRI) after demonstrating a performance equivalence to the manual reference method. One or two TRIs then can be removed from these platforms and installed in a monitoring station to ensure that staion monitor’s readings are consistent with those of the TRIs. If there is a significant variation in the readings between the TRI and station monitors there may be a need to contact the vendor for insight into the issue.
However, preliminary results have shown that the linear regression correlation (including slope and intercept) of TRI versus manual reference method changes by seasons. This variation is especially significant on intercept value and indicates that TRI performance may change even under continuous operation in a single location.
To meet the additional objectives of this project, we also help the quality assurance laboratory to improve the performance and maintenance of two standard calibration systems: a flow meter and ozone analyzer. The plan to achieve this is as follows: (1) design a monthly check list and records for the flow and ozone system, (2) design and setup control charts of the system, (3) help the laboratory maintain TAF accreditation of flow calibration capabilities, (4) design and perform remote control calibration techniques.
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