Nondetrital and total metal distribution in core sediments from the U-Tapao Canal, Songkhla, Thailand

The U-Tapao Canal is the main source of freshwater draining into the outer part of Songkhla Lake, which is the most important estuarine lagoon in Thailand. Songkhla Lake is located in southern Thailand between latitudes 7 08 and 7 50 N and longitudes 100 07 and 100 37 E. Acetic acid (HOAc)-soluble Cu, Fe, Mn, Pb, and Zn and the total concentration of these metals along with Al concentration, organic carbon, carbonate, sand, silt, and clay contents were determined in 4 sediment cores obtained at selected intervals from the mouth of the canal to 12 km upstream. Readily oxidizable organic matter in the cores varies from 1.52% to 7.30% and is generally found to decrease seaward. Total concentrations of Al (61.7 99.0 g kg 1; 2.293.67 mol kg 1), Cu (12.4 28.2 mg kg 1; 195 444 Amol kg 1), Fe (25.2 42.0 g kg 1; 451 752 mmol kg 1), Mn (0.220.49 g kg 1; 4.08.9 mmol kg 1), Pb (16.743.1 mg kg 1; 80.6208 Amol kg 1), and Zn (48.6122.7 mg kg 1; 0.741.88 mmol kg 1) vary to a certain extent vertically and seaward in the U-Tapao Canal core sediments. These concentrations are at or near natural levels and show no indication of anthropogenic contamination. Overall, the data show that total metal concentrations in the surface and near surface core sediments are enriched in varying degrees relative to Al in the order of ~ZnNMnNPbNFeNCu. Chemical partitioning shows that the enrichment in the surface and near surface sediments is related to the relatively high proportion of the total metal concentrations (MnNZnNFeNCuNPb) that occur in the acetic acid-soluble (nondetrital) fraction, and they generally decrease with depth. Nondetrital Cu, Pb, and Zn likely derive from those metals held in ion exchange positions, certain carbonates, and from easily soluble amorphous compounds of Mn and perhaps those of Fe. Diagenetic processes involving Mn and to a lesser extent, Fe compounds, as well as the vertical changes in the oxidizing/reducing boundaries, appear to be the most important factors controlling the behavior of the metals in these cores. Organic matter and the aluminosilicate minerals, however, appear to be less important carriers of the metals studied

Source and Distribution of Polycyclic Aromatic Hydrocarbons (PAHs) in Surface Sediment from Chalong Bay, Phuket, Thailand

This study aimed to investigate the spatial distribution and apportionment of potential sources of the 16 US-EPA priority PAHs in surface sediments of Chalong Bay, Phuket, Thailand. A total 28 of sediment samples were collected from areas with high maritime activity in Chalong Bay, subjected to conventional high recovery Soxhlet extraction, purified with SiO2 column chromatography, and quantified by Gas Chromatography-Mass Spectrometry (GC/MS). Total concentration of PAHs (Σ16PAHs) ranged from 31.15 to 1696 ng g−1 dry weight, with an average of 198.2 ± 318.5 ng g−1 dry weight. Binary diagnostic ratios plots were used to distinguish between petrogenic and pyrogenic sources. Most of the PAHs in sediments originated from pyrolytic sources. PCA analysis explained 82.3 % of the variance by only 4 predominant components. The first principal component (PC1) (26.7 %) was mainly contributed to urban street runoff and municipal wastewater discharge. PC2 (25.8 %) represented vehicular combustion sources, PC3 (19.1 %) was attributed to petrogenic sources, and PC4 (10.7 %) was only associated with Naphthalene. The sources of PAHs distributed around Chalong Bay included oil spills, combustion of fossil fuels by shipping, urban street runoff, and municipal wastewater discharge. Each type of sources affected different locations along shores of Chalong Bay. 

Risk Assessment of Total Mercury (T-Hg) in Commercial Seafood Marketed in Bangkok, Thailand

Seafood is recognized as the high protein source of human consumption. However, it is hampered by mercury contamination. The objectives of this study are to determine total mercury (T-Hg) levels in edible portions of commercial seafood available in Bangkok’s supermarkets, and to evaluate the potential risks from mercury through seafood consumption. Total 32 species, including 22 fish, 4 cephalopod and 6 shellfish, were purchased from super-markets. Fish samples were dissected in 3 parts comprised of flesh, gill and viscera. While, cephalopod and shellfish were separated for edible tissues. The samples were digested in hot acid and were determined using cold-vapor atomic absorption spectrometry technique. The results revealed that T-Hg contained in the fish flesh > cephalopod > shellfish. In addition, T-Hg was accumulated in flesh > viscera > gill. Statistical analysis suggested that T-Hg accumulated in flesh was related positively with species, feeding habit, and habitat (p < 0.05). For risk analysis, estimated daily intake (EDI) of flesh ranged from 0.01 to 0.42 µg kg-1 bodyweight d-1, the lowest and highest EDI values were in salmon and yellowfin tuna, res-pectively. Yellowfin tuna, narrow-barred Spanish mackerel, fourfinger threadfin, and silver sillago were the 4 species that having the EDI values of T-Hg higher than the FAO/WHO recommended provisional tolerable daily intake (PTDI) of 0.23 µg kg-1 bodyweight d-1. Thus, the frequent consumption of these seafood are not recommended. In addition, the daily consumption of seafood should not exceed the maximum safe daily intake (MSDC). The MSDC of seafood in this study ranged from 15.5 (yellowfin tuna) to 474 (salmon) g d-1

Acid volatile sulphide estimation using spatial sediment covariates in the Eastern Upper Gulf of Thailand: Multiple geostatistical approaches

Summary: Acid volatile sulphide (AVS), one of the most reactive phases in sediments, is a crucial link in explaining a dynamic biogeochemical cycle in a marine ecosystem. Research gaps exist in describing the spatial variation of AVS and interconnections with sediment covariates in the Eastern Upper Gulf of Thailand. Measurements of AVS and auxiliary parameters followed the standard protocol. A comparison of ordinary kriging (OK), cokriging (CK), and regression kriging (RK) performance was evaluated based on the mean absolute error (MAE) and root mean square error (RMSE). The concentrations of AVS ranged from 0.003 to 0.349 mg g−1 sediment dry weight. Most parameters contained short range spatial dependency except for oxidation–reduction potential (ORP) and pH. The AVS tended to be both linearly and non-linearly related to ORP and readily oxidisable organic matter (ROM). The RK model, using inputs from the tree-based model, was the most robust of the three kriging methods. It is suggested that nonlinear interactions should be taken into account when predicting AVS concentration, and it is expected that this will further increase the model accuracy. This study helps establish a platform for ecological health and sediment quality guidelines. Keywords: Spatial estimation, Acid volatile sulphide, Sediment, Geostatistical analysis, Gulf of Thailan

Mercury content and consumption risk of 8 species threadfin bream (Nemipterus spp.) caught along the Gulf of Thailand

Total mercury (T-Hg) was examined in 8 threadfin bream species (Nemipterus spp.) caught in the Gulf of Thailand (GoT). The T-Hg contents ranged from 11.3 to 374 μg kg−1 wet weight, with the lowest in Nemipterus peronii and the highest in Nemipterus nemurus and Nemipterus tambuloides. Accumulation of T-Hg in fish tissue was found to be related to fish size, trophic levels, feeding habits and habitat. Threadfin bream caught in the upper GoT exhibited significantly (p −1 bodyweight day−1. All threadfin breams in the GoT have HQ −1

Feeding Habits and the Occurrence of Anthropogenic Debris in the Stomach Content of Marine Fish from Pattani Bay, Gulf of Thailand

This study assessed the feeding habits and ingestion of anthropogenic debris in 34 marine fish species from the southern Gulf of Thailand. A total of 5478 fish samples of 12 families were categorised into seven groups: planktivore, Lucifer feeder, fish feeder, Acetes feeder, shrimp feeder, piscivore, and zoobenthivore fish. A total of 2477 anthropogenic debris items were extracted from 12 fish species by visual inspection. Their ingestion of anthropogenic debris was influenced by season (p p = 0.022). Blue-coloured anthropogenic debris was commonly detected in the stomachs of fish and significantly differed between species (p > 0.001). Water depth and season significantly influenced the availability of food types (AF) for fish (p < 0.001). These findings provide evidence of the ingestion of anthropogenic debris by fish inhabiting a natural bay and signal the future anthropogenic pollution of marine fish

Metal concentrations and source apportionment of PM2.5 in Chiang Rai and Bangkok, Thailand during a biomass burning season

One of the persistent environmental problems in the provinces of northern Thailand is severe air pollution during the dry season because of open vegetation burning by farmers for land clearance purpose. Aerosol optical depth and Ångström exponent data from MODIS-Terra satellite indicated that from mid-March to April, 2019, entire Thailand was covered with a high concentration of fine-sized aerosols. Trace metal concentrations of PM2.5 collected from Chiang Rai in northern Thailand and Bangkok in southern Thailand between January and April 2019 were analyzed. Average concentrations of crustal metals such as Al, Ca, and Fe are higher in Chiang Rai compared to that in Bangkok. The Fe/Al ratio in Chiang Rai decreases from 1.65 during the onset of haze to 0.87 during the peak haze approaching a crustal ratio of 0.48. In contrast, Bangkok has higher Na, Mg, and Zn with an average Na/Mg ratio of 6.07 indicative of a sea spray (Na/Mg ∼ 8) origin. Principal component analysis identifies three possible sources in Chiang Rai: (1) crustal dust and biomass burning, (2) industrial source, and (3) refuse incineration mixed with road dust; and for Bangkok (1) natural background, industrial emissions, and coal combustion, (2) traffic emission, and (3) sea spray. The ranges of Pb isotope ratios in the bulk fraction of PM2.5 in Chiang Rai (206Pb/207Pb = 1.1445–1.1657 and 208Pb/207Pb = 2.4244–2.4468) and Bangkok (206Pb/207Pb = 1.1343–1.1685 and 208Pb/207Pb = 2.4138–2.4450) are not significantly different. However, in a time series plot, 206Pb/207Pb ratios in Chiang Rai follow PM2.5 during the peak burning season and correlate well with the Al/Pb (r2 = 0.61) ratios, indicating that at least part of the Pb is derived from crustal dust during peak fire. Using a binary mixing model, the most radiogenic Pb isotopes in Chiang Rai during the peak haze can be explained by ∼5 to 30% mixing of crustal dust with ∼35–40% biomass burning generated aerosols with the background. From the trace metal systematics and Pb isotope ratios, it is evident that (1) during the biomass burning season, trace metals from Chiang Rai are not transported down south to Bangkok and (2) in addition to metals released from biomass burning, the raging fire remobilizes crustal dust that forms an important source of Pb and other trace metals in the Chiang Rai aerosol.Ministry of Education (MOE)Accepted versionThis research has been supported by a Singapore Ministry of Education (MOE) Tier 1 grant (MOE-NTU_RG125/16-(S)), Department of Science & Technology (DST, Govt of India) (RTF/2019/000052), Centre of Excellence on Hazardous Substance Management and the 90th Anniversary (Ratchadaphiseksomphot Endowment Fund) of Chulalongkorn University Funds. JK was supported by the Science Achievement Scholarship of Thailand (SAST). The authors also thank the research groups of MODIS for providing the data and HYSPLIT for providing software for back-trajectory computations. The authors would also like to thank Mr. Pornsak Bureekul for collecting the sample from Chiang Rai and Ms. Lin Ke for keeping the chemistry lab and instruments in impeccable conditions. Baan Hom Muen Lee Resort in Chiang Rai (http://www.baanhommuenlee.com/) kindly provided us with the pictures of clear day and hazy day in Chiang Rai used in the TOC graphics