In-Cloud Concentrations and Below-Cloud Scavenging Processes in Hong Kong, China

Peter A. Tanner; Christopher W. F. Tam

doi:10.1071/EN05084

RESEARCH ARTICLE

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In-Cloud Concentrations and Below-Cloud Scavenging Processes in Hong Kong, China

Peter A. Tanner ^A ^B and Christopher W. F. Tam ^A

+ Author Affiliations

- Author Affiliations

^A Department of Biology and Chemistry, City University of Hong Kong, Kowloon, Hong Kong SAR, Peoples’ Republic of China.

^B Corresponding author. Email: bhtan@cityu.edu.hk

Environmental Chemistry 3(2) 142-148 https://doi.org/10.1071/EN05084
Submitted: 17 October 2005 Accepted: 9 January 2006 Published: 5 May 2006

Environmental Context. There are fewer studies of cloudwater than of precipitation because of the limited occurrence of cloud events, and technical and logistic sampling difficulties. In order to assess the importance of in-cloud and below-cloud processes, cloudwater and rainwater samples were collected at the highest mountain in Hong Kong and also near sea level.

Abstract. Preliminary measurements of ionic concentrations in cloudwater collected at the highest mountain in Hong Kong show that the pH can be as low as 3.4, which is lower than that of rainwater collected in urban–residential Hong Kong. Sulfate is the most abundant anion, and hydrogen or ammonium ions are the most abundant cations in the cloudwater samples. Results are also presented for analyte concentrations in sequential samples taken during a rain event from a maritime airmass. The concentrations of sea salt species were high and exhibited an exponential decrease with concentration at the start of the event. The concentrations of other species also decreased to fairly constant, low values after ~10 mm rainfall. The fitting of the concentration–rainfall plots enabled in-cloud and below-cloud mechanisms of incorporation of the species to be distinguished.

Keywords. : atmospheric chemistry — China — cloudwater — scavenging — sequential samples

Acknowledgements

We acknowledge financial support for this work under City University DAG Grant 7100029. We gratefully acknowledge the NOAA Air Resources Laboratory for the provision of the HYSPLIT transport and dispersion model at http://www.arl.noaa.gov/ready/open/hysplit4.html used in this publication.

References

In-Cloud Concentrations and Below-Cloud Scavenging Processes in Hong Kong, China

Acknowledgements

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