J. Environ. Res. 34 (2): 21-38 J. Environ. Res. 34 (2): 21-38 ACCUMULATION OF HEAVY METALS IN MANGROVE SEDIMENTS OF CHUMPHON PROVINCE, THAILAND การสะสมโลหะหนักในดินตะกอนป่าชายเลน จังหวัดชุมพร ประเทศไทย Nathsuda Pumijumnong1,2*and Bussarin Uppadit1,2 1Faculty of Environment and Resource Studies, Mahidol University, Salaya, Phutthamonthon, Nakhon Pathom 73170, Thailand 2The Center for Toxicology, Environmental Health and Management of Toxic Chemicals under Science & Technology Postgraduate Education and Research Development Office (PERDO) of the Ministry of Education, Thailand นาฏสุดา ภูมิจำานงค์1,2*และ บุศรินทร์ อุปดิษฐ1,2 1คณะสิ่งแวดล้อมและทรัพยากรศาสตร์ มหาวิทยาลัยมหิดล นครปฐม 73170 ประเทศไทย 2ศูนย์ความเป็นเลิศทางด้านอนามัยสิ่งแวดล้อม พิษวิทยาและการบริหารจัดการสารเคมี ภายใต้การกำากับของ โครงการพัฒนาบัณฑิตศึกษาและวิจัยด้านวิทยาศาสตร์และเทคโนโลยี กระทรวงศึกษาธิการ,ประเทศไทย Received: February 14, 2012 Accepted: June 26, 2012 Abstract model Varian SpectrAA 220FS). Cd and Pb were analyzed by a graphite furnace atomic The objective of this study was two-fold: to absorption spectrophotometer (GASS, model examine the heavy metal (Cd, Cu, Cr, Ni, Mn, Pb and Varian SpectrAA220). The accumulation of heavy Zn) levels that have accumulated in mangrove metals originated largely upstream and decreased forest sediments in Chumphon Province, Thailand, towards the canal mouths. The highest levels of and to determine the relationship between heavy heavy metals were found at E-let canal (Thung Kha metals and the physiochemical properties of Bay). The heavy metals present in our study area, sediment. The sediment was digested with HNO 3 listed from the most to least prevalent, were Mn, and HCl using a milestone microwave digestion Cu, Zn, Cr, Ni, Pb, and Cd. A striking relationship system (model MLS-1200 MEGA), followed by the was found between heavy metal type and sediment addition of 50 ml distilled water. The concentrations physiochemical properties (pH, OM, EC, and CEC). of Cu, Cr, Ni, Mn, and Zn in the filtered and digested samples were determined by air-acetylene flame Key Words: heavy metal, mangrove sediment, atomic absorption spectrophotometry (FAAS, Chumphon Province, Thailand * corresponding author E-mail : [email protected] Phone : +66-2441-5000 ext. 2311 21 Phumijumnong and Uppadit, 2012 บทคัดย่อ land from mangrove and wetland to shrimp วัตถุประสงค์ในการศึกษาครั้งนี้เพื่อตรวจสอบ farming, palm oil harvesting, and rubber การสะสมโลหะหนัก (Cd, Cu, Cr, Ni, Mn, Pb and Zn) tree plantations(4). In the past, mangrove ในดินตะกอนป่าชายเลน จังหวัดชุมพร ประเทศไทย forests at Thung Kha bay and Sawi bay in และความสัมพันธ์ระหว่างโลหะหนักกับคุณสมบัติ the Chumphon province were the second ทางกายภาพ-เคมีของตะกอน ตะกอนถูกย่อยด้วยกรด largest in Thailand and exhibited much ไนตริกและกรดเกลือโดยเครื่องไมโครเวฟ, รุ่น MLS-1200 MEGA, เติมด้วยนำ้ากลั่น 50 มิลลิลิตร ความเข้มข้นของ biodiversity. When mangrove logging was Cu, Cr, Ni, Mn และ Zn ทำาการวัดโดยเครื่องเฟรม (FAAS, banned in 1983, only small trees remained. model Varian SpectrAA 220FS) Cd และ Pb ทำาการ The local inhabitants have since realized วัดโดยเครื่องกราไฟท์ (GASS, model Varian Spectr the benefits a mangrove ecosystem could AA220) ผลการศึกษาพบว่าโลหะหนักมีการสะสมสูง provide, and have thus attempted to บริเวณต้นนำ้าและลดต่ำาลงสู่ปากนำ้า โลหะหนักมีการสะสม propagate and extend the mangrove forest สูงที่สุดที่ คลอง อีเล็ด (อ่าวทุ่งคา) ลำาดับของการสะสม โลหะหนักในการศึกษาครั้งนี้จากมากไปน้อยคือ Mn, Cu, area. Zn, Cr, Ni, Pb และ Cd ความสัมพันธ์อย่างเด่นชัด Research, regarding how the พบระหว่างโลหะหนักกับคุณสมบัติด้านกายภาพ-เคมี preservation of mangrove forests helps ของตะกอน (pH, OM, EC and CEC) absorb and filter pollution including heavy คำ�สำ�คัญ: โลหะหนัก, ดินตะกอนป่าชายเลน, metals from upstream locations, is lacking. จังหวัดชุมพร, ประเทศไทย Many researchers have found that excess pollution negatively affects mangrove growth Introduction rates and increases mortality rates(5). This The mangrove tree grows only in study examines the extent of heavy metal tropical and subtropical zones. With the accumulation in the mangrove sediment of expansion of urbaniation, shrimp farms, and Chumphon province. Our results outline future agricultural enclosures have resulted in the benefits of mangrove forests to coastal zone death of mangrove areas(1). Global warming management. problems have affected sea level rise, loss Materials and Methods of biodiversity, and salt-water intrusion of all coastal areas(2). These problems also directly Accumulation of heavy metals in mangrove impact mangrove forest areas. Chumphon sediments of coastal Chumphon province province’s coastal area remains one of The Bang Son bay mangrove forest the world’s most vulnerable areas, with a is located between 10°40' and 10°41' N history of natural catastrophes(3) and human latitude and 99°19' and 99°20' E longitude destruction. Humans have changed this at the mouth of Bang Son canal (B) in the 22 J. Environ. Res. 34 (2): 21-38 Pathio district of Chumphon province. This Kha bay are Chumphon (or Bang Yai), Visai, area is near the Chumphon airport, possibly Sawi, and Sawi Thao canals. The E-let canal receiving wastewater discharge from paddy (T) and Sawi canal (S) flow through these fields, oil palm/coconut fields, para rubber mangrove forests in the Mueang district fields, shrimp farms, and household and the Sawi district of Chumphon province. wastewater(6). These areas receive discharge from Thung Kha bay and Sawi bay originate shrimp farms, oil palm/coconut fields, and from the coastal uplift. The area is located household wastewater. between 10°13' and 10°24' N latitude and Three mangrove forest sediment 99°5' and 99°15' E longitude. The deposition transects (B, T and S) were collected along of river sediment and soil is sandy, muddy, canals (Bang Son, E-let and Sawi). Each and covered by mangroves. With a length transect was sampled at six points, with of more than 20 km, the mangrove forest is each point 300 m away from the mouth of approximately 20.8 km2 (32,880.71 rai), and the canal towards the land. At each the dominant tree species in the area are sampling site, sediment sample was taken Rhizophora sp. and Ceriops tagal. The mud at a level 0-30 cm from the surface. Samples flat is approximately 17.6 km2 (27,822.14 rai), were kept in tightly closed plastic bags and and the main canals that flow into Thung collected in April of 2009 (Figure1) 23 Phumijumnong and Uppadit, 2012 Figure 1 Illustration of the three sampling sites for mangrove sediment collection 24 J. Environ. Res. 34 (2): 21-38 Analyses of sediment properties Analyses of heavy metals Sediment samples were air-dried at Samples were analyzed for Cu, Cr, Ni, room temperature and passed through a Mn and Zn contents using an air-acetylene 2 mm sieve to remove larger particles. Soil flame atomic absorption spectrophotometer texture analyses were performed using the (FASS, Model Varian SpectrAA 220FS). hydrometer method(7). The soil reaction (pH) Cd and Pb were analysed with a graphite was measured (soil: water 1:1) using a pH furnace atomic absorption spectrophotometer meter and glass electrode. The electrical (GASS, Model Varian SpectrAA 220). Data is conductivity (EC) was measured using a presented as mg kg-1 dry weight (dw). conductivity meter in an extracted solution Results and Discussion of a 1:5 ratio of sediment to distilled water. The organic matter (OM) content was Physiochemical parameters of the mangrove determined by the Walkley and Black Rapid sediment Tritration Method(8). The cation exchange Sediment sample were taken at three capacity (CEC) in me/100 g was determined transect lines: the first at Bang Son canal using a NaOAC 1N, pH 8.2, and processed (B1-B6), and the second and third lines at with a mechanical vacuum extractor(8). All E-let canal (T1-T6) (Thung Kha Bay) and Sawi samples were analyzed in triplicate. canal (S1-S6) (Sawi bay). These results are For heavy metal analysis, approximately shown in Table 1. 0.5 g of dried, homogenized sediment At Bang Son canal (B1-B6), sandy samples was transferred into digestion loam was the most common sediment vessels. Sediments were digested with texture found. The pH of sediments ranged HNO3 and HCl using a milestone microwave from 2.39 to 5.02, with B2 and B4 having digestion system (model MLS-1200 MEGA). the lowest pH (2.39 and 2.65). The % OM The digestates were left to cool at room fluctuated from the riverbank toward land. temperature and then filtered through The highest % OM was found at B3. The EC Whatman filter paper No. 42. Filtered fluctuated from the riverbank toward land digestates were diluted with distilled (3.86 to 4.20 mS/cm), with B3 having the deionised water to 50 ml in a volumetric highest EC (9.46 mS/cm). The CEC is related flask, stored in acid-washed 60 ml polyethylene to the % OM(10); when the % OM increased, bottles, and kept in the refrigerator until CEC also increased. The highest CEC was analysis(9). found at B3 (8.48 Cmol/kg). 25 Phumijumnong and Uppadit, 2012 Sandy loam was found to be the most from 4.25 to 9.08 mS/cm, and CEC from 2.50 common sediment texture at E-let canal to 8.20 Cmol/kg. (Thung Kha bay), with the exceptions of T4 Water levels of Thung Kha and Sawi and T6, which had sediment textures of bays are low, with weak current and principle loam and clay loam, respectively. This diurnal tidal. Beinkman et al(3) found that texture difference most likely exists due to at the Sawi bay, currents were primarily the interaction between freshwater inflow controlled by prevailing circulation of the and sea waves. Sediment pH ranged from adjoining Gulf of Thailand and river runoff, 2.67 to 5.49. The % OM of the sediment and most of sediment was fine silt and clay. ranged from 1.70 to 5.76. T3 had the highest The pH of the sediments ranged from 2.39 % OM. The EC value ranged from 4.93 to to 5.49. The sediment samples located close 11.44 mS/cm, with T3 having the highest to the estuary were more due to intrusion of (11.44 mS/cm). CEC values fluctuated from salt water during high tide. OM content in 2.57 to 10.75 Cmol/kg.