Dry deposition (downward,upward) concentration study of particulates and water-soluble ionic species during daytime,night-time period at the traffic sampling site of Sha-Lu,Taiwan

Abstract

Ambient suspended particulate (dry deposition, TSP) was collected in the traffic sites Sha-Lu, central Taiwan. In addition, the related water-soluble ionic species (Cl^¹/4, NO₃ ^¹/4, SO₄ ² ^¹/4, Na⁺, NH₄ ⁺, K⁺, Mg² ⁺and Ca²⁺) were analysed and wind speed, wind direction and temperature were also measured in this study. The downward dry deposition fluxes (averaged 54.07 mg/m²-sec) were about twice that of upward dry deposition fluxes (averaged 26.48 mg/m²-sec) in the daytime period. Furthermore, the average downward dry deposition fluxes (averaged 26.22 mg/m²-sec) were also about twice that of upward dry deposition fluxes (averaged 12.11 mg/m²-sec) in the night-time period. The results showed that the total suspended particulate concentrations of particulate mass in the daytime period (averaged 996.2 mg/m³) were higher than in the night-time period (averaged 560.7 mg/m³). The results showed that the total suspended particulate concentrations of particulate mass in the daytime period (averaged 996.2 mg/m³) were higher than in night-time period (averaged 560.7 mg/m³). As for water-soluble ionic species, the average dry deposition order and velocity for downward ionic species were Cl^¹/4 Í-Ca²⁺Í-NO₃ ^¹/4 Í-K⁺(2.09 cm/sec Í-1.46 cm/sec Í-1.46 cm/sec Í-1.07 cm/sec) anions during the daytime period. And the average dry deposition order and velocity for downward ionic species were NO₃ ^¹/4 Í ^/ Cl^¹/4 Í ^/ K⁺Í ^/ Ca²⁺(2.92 cm/sec Í ^/ 2.74 cm/sec Í ^/ 0.96 cm/sec Í ^/ 0.93 cm/sec) anions during the night-time period. The average dry deposition order and velocity for upward ionic species were Cl^¹/4 Í ^/ Ca²⁺Í ^/ K⁺Í ^/ Mg² ⁺(4.69 cm/sec Í ^/ 0.62 cm/sec Í ^/ 0.59 cm/sec Í ^/ 0.55 cm/sec) anions during the daytime period. And the average dry deposition order and velocity for upward ionic species were Cl^¹/4 Í-Ca²⁺Í-Mg² ⁺Í-K⁺(1.65 cm/sec Í-0.43 cm/sec Í ^/ 0.37 cm/sec Í ^/ 0.33 cm/sec) anions during the night-time period. The results also indicated that the sodium and chloride concentrations in total suspended particulate were highly positively related, indicating that the sea-salt aerosols were the major contributors for these species at this sampling site of central Taiwan.

Keywords

dry deposition suspended particulate water-soluble ionic

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