IJRRAS 7 (3) ● June 2011 www.arpapress.com/Volumes/Vol7Issue3/IJRRAS_7_3_02.pdf 228 SPATIAL DISTRIBUTION OF MARINE SALTS IN COASTAL REGION USING WET CANDLE SENSORS Khandaker M.A. Hossain & Said M. Easa Dept. of Civil Engineering, Ryerson University 350 Victoria Street, Toronto, Ontario, M5B 2K3, Canada. Tel: (416) 979 5000-ext 7867, Fax: 416 979 5122 E-mail: ahossain@ryerson.ca ABSTRACT The results of a study to evaluate the spatial distribution of marine salts from sea spray in relation to the distance from the sea are presented. The study monitored the deposition rate of chlorides and sulfates from sea spray in wet candle sensors, located at twelve sampling stations scattered around the metropolitan region of the port city of Chittagong in Bangladesh which is situated on the coastline of the Bay of Bengal. The type and amount of salts captured in the solution from the wet candle sensors were determined by ion chromatography. The data collected showed that the marine salt deposition is significant up to a distance of about 200 m from the seashore. From this point onward, the amount of chlorides drops sharply and in the case of sulfates, other emission sources become more critical than the sea spray. Relationships between the concentration of marine salts and the distance from the sea are established. The results of this study can be used to evaluate the potential aggression of salt deposition on marine systems, and as such should be useful in infrastructure planning and management. Keywords: Sea spray; Marine salts; Wet candle sensors, Ion chromatography. 1. INTRODUCTION Excessive salt in terrestrial environments can lead to accelerated corrosion of human assets, salinization of agricultural soils, elevated water stress, leaf necrosis, and growth inhibition of plants that have low salt tolerance. In coastal regions, the atmosphere is enriched with particles that are naturally generated by the action of wind on the seawater surface. The sea spray, composed primarily of seawater along with these particles, introduces ionic species into the atmosphere, principally chlorides and sulfates (Campos et al. 2006, Carlos et al. 2003, Davidson et al. 1989). The enriched air containing sea spray causes accumulative deposition of ions (on the external surface of structures) which are able to penetrate to the interior of the material through ionic diffusion causing its degeneration. Such environments that are charged with salts are extremely dangerous to construction materials as they can penetrate and crystallize inside the material, causing deterioration of the physical structure (Soroka and Carmel 1987). Research work has been conducted to evaluate the deterioration of structures exposed to atmospheric aerosol and/or to acid deposition. Many of these researches concentrated on the mechanisms of interaction between atmospheric substances and those present in construction materials (Sabbioni et al. 2003, Perry and Duffy 1997, Leysen et al. 1989, Zappia et al. 1992). Others were concentrated on the production/distribution of salts from marine aerosols as well as their interaction with structures (Meira et al. 2007, Meira et al. 2006, Lee and Moon 2006, Cole and Paterson 2004, Cole et al. 2003, Morcillo et al. 2000, Petelski and Chomka 2000, Gustafsson and Franze´n 1996). Bangladesh is a country which has a large coastal area with the Bay of Bengal (Fig. 1). Some major cities including Chittagong are situated on the coastline where the action of sea spray creates an aggressive atmosphere for materials and products used in construction. Chittagong is the second largest city, the Commercial Capital, the chief sea port and the main centre of export and import of Bangladesh. From the last decade, the city is expanding rapidly with the establishment of heavy, medium and light industries. The population of the city also increased with the rapid expansion of its metropolitan region. In the city of Chittagong, an intense presence of sea spray can be detected along the coastal line and over the greater metropolitan area of the city. The atmosphere of this area has a strong presence of marine aerosol that has high levels of chloride ions like other regions of the world (Hossain 2001). Such aggressive environment has caused tremendous deterioration/damage to local structures (such as buildings and bridges) and reduced their service life. Very little research has been conducted to measure and evaluate the quantity of airborne sea salt in the context of Bangladesh. Such studies can provide important data for the design and maintenance of seashore infrastructures in Bangladesh.