Effects of organic nutrients and growth factors on biostimulation of tributyltin removal by sediment microorganisms and Enterobacter cloacae.

Natural attenuation can reduce contamination of tributyltin (TBT), but persistence of the xenobiotic can cause long-term issues in the environment. Biostimulation is used to accelerate biodegradation. This study investigated the ability of individual organic nutrients and growth factors to enhance TBT biodegradation by sediment microorganisms (SED) and Enterobacter cloacae strain TISTR1971 (B3). The supplements that produced high biomass yield were selected for degradation enhancement. For TBT degradation at initial concentration of 0.1 mg/l, negative or limited degradation was observed in some selected supplements indicating that increasing the biomass did not necessarily promote degradation. Consequently, the addition of nutrients was expected to increase both dioxygenase activity and the degrader population. At different concentrations of supplements, a mixture of succinate/glycerol showed the highest removal for SED which reduced TBT by 77%, 75%, and 68% for 0.1×, 1×, and 10× supplement concentration, respectively. For B3, the addition of succinate showed degradation of 49% (0.1×), 75% (1×), and 77% (10×). Most nutrients and amino acids had an inhibitory effect at 1× or 10× levels. Excess amount of the nutrients added can inhibit the initial degradation of TBT. Therefore, TBT biostimulation requires supplements that increase the capability of TBT degraders at an appropriate amount.

The ecological complexity of the Thai-Laos Mekong River: II. Metals and polyaromatic hydrocarbons (PAHs) monitoring, modelling and environmental fate.

The Mekong is an essential source of water and protein for the denizens of Thai Laos countries. It is hypothesized that pollution may be adversely affecting the water and sediment quality, which threatens the short and long-term use of this major river system. This directly impacts on the health and population of the aquatic life and ultimately human health and the economy for both countries is affected. The quality of the river can be assessed from various chemical and physical parameters, such as PAHs and metals content of both the water and the sediment. The introduction of Environmental Quality Standards (EQS) allows comparison of the values obtained with the guidelines. Furthermore the modelling program EPISUITE was used to determine the environmental partitioning of pollutants within the different environmental compartments. Using the data produced for PAHs and metals the experimental model was compared to the default model. This involved experimentally measuring the log K(oc) for Mekong sediments and from this determining the log K(ow). High availability in sediment of pollutants may lead to greater biomagnification in bethnic fish, which may then be hazardous for human consumption even if it is safe for the species that is accumulating pollutants. The potential for this is shown by the calculated accumulation in biota C(bio) values exceeding both the Chronic value (ChrV) and Lethal Concentration 50 (LC(50)) for fish in the Mekong River. When compared to the EQS guidelines the amount of some PAHs, cadmium and lead in sediment were above the lowest effect level but below the severe effect level.

The ecological complexity of the Thai-Laos Mekong River: III. Health status of Mekong catfish and cyprinids, evidence of bioaccumulative effects.

Histopathology of fish organs was used as biomarkers of toxicity from environmental pollutants. A total of 117 fishes comprising of 52 cyprinids and 65 catfishes were randomly collected from the Mekong River from 5 stations: Chiang Rai, Loei, Nongkhai, Nakhon Phanom and Ubonratchathani. The health of the fish collected in December and April, winter and summer respectively, was evaluated. All fish from the 5 stations developed pathologic lesions with the same characteristics in their livers, kidneys and spleen. In the liver, there was vacuolation of hepatocytes, accumulation of brownish-green granules in the cytoplasm of hepatocytes, necrosis of hepatocytes, granuloma formation and angiogenesis. Kidney lesions consisted of glomerular degeneration, necrosis and focal hyperplasia of renal tubules. In the spleen, there were haemorrhage, melanomacrophage centre infiltration and necrosis of the red pulp and white pulp. The pathologic severity of the catfish was found to be more severe than in the cyprinids and the catfish collected in summer were less healthy than the catfish collected in the winter. These histopathological appearances might arise from the fish feeding on the benthos and thereby accumulating toxic pollutants in their organs. The activities of the serum enzymes, Glutamic Oxalacetic Transaminase (GOT) and Glutamic Pyruvic Transaminase (GPT), were markedly increased, indicating detoxification activity. The highest activity of GOT found in the cyprinids from Chiang Rai 365.30 U/L whereas in the catfish from Nakhon Phanom the activity was 300.73 U/L. The highest GPT activity found in the cyprinids from Nakhon Phanom was 203.23 U/L where as in the catfish from the same station was GPT 389.77 U/L. According to the results from this study, catfish collected from Chiang Rai, Nakhon Phanom and Ubonratchathani showed more severe pathological changes than catfish from the other stations. Fish organs and river water were analysed for Polyaromatic Hydrocarbons (PAHs) and metals. The fish organs showed bioaccumulation of these toxic pollutants. BioConcentration Factors (BCFs) were calculated. Therefore an attempt is made to correlate these findings to the Mekong study in general.

The ecological complexity of the Thai-Laos Mekong River: I. Geology, seasonal variation and human impact assessment on river quality.

The objective of this study is to assess the variation of pollution in the Thai-Laos Mekong associated with seasonal dynamics concomitant with the natural geological features and human activities that impact on the adverse quality of the river. The complex ecology of the 1500 km stretch of the Thai-Laos Mekong River has been studied in this paper to understand the relationship with the geomorphology, with the sub-tropical monsoonal climate and the impact of human activity. Sub-surface geology controls the nature and extent of the drainage basin and of the river channel. The volume flow of the river varies naturally and dynamically in phase with the rainfall; traditional models based on steady state hydraulics are inappropriate. Continuous erosion of the river banks and bed generates a sediment load of impure silt, mica, quartz and clay minerals that inhibits light penetration and limits the primary productivity of the river. The river separates two countries at different stages of development; it flows through or close to eight non-industrial conurbations (Populations 350,000-2,000,000) but is otherwise sparsely populated. The river is used for subsistence agriculture, village transport, fishing including aquaculture and as a source of domestic water. Hydroelectricity is generated from the Laos tributaries. The river is a depository for partially treated urban waste and untreated village waste, hence populations of E.coli bacteria sometimes render the water unsuitable for drinking unless treated with the highest value of 240/100 ml found at station 7 during the summer season of 2003. Furthermore the river is polluted by trace metals, notably cadmium and mercury, and by Polycyclic Aromatic Hydrocarbons (PAHs), which are particularly concentrated in the sediments. Previous work has shown that cadmium and mercury exceed the Probable Effect Level (PEL) values of Canadian Environmental Quality Guidelines and that the PAH concentrations were also greater than the Interim Sediment Quality Guidelines (ISQG). Consequently the fish stock, a vital source of protein for the local human population maybe seriously affected. As conflict between the demands of human activities will be exacerbated by the continuing development of the basin; monitoring must be continued and a better model of the river's ecology is needed to predict the impact of development.

Development of a low-cost method of analysis for the qualitative and quantitative analysis of butyltins in environmental samples.

Most analytical methods for butyltins are based on high resolution techniques with complicated sample preparation. For this study, a simple application of an analytical method was developed using High Performance Liquid Chromatography (HPLC) with UV detection. The developed method was studied to determine tributyltin (TBT), dibutyltin (DBT) and monobutyltin (MBT) in sediment and water samples. The separation was performed in isocratic mode on an ultra cyanopropyl column with a mobile phase of hexane containing 5% THF and 0.03% acetic acid. This method was confirmed using standard GC/MS techniques and verified by statistical paired t-test method. Under the experimental conditions used, the limit of detection (LOD) of TBT and DBT were 0.70 and 0.50 microg/mL, respectively. The optimised extraction method for butyltins in water and sediment samples involved using hexane containing 0.05-0.5% tropolone and 0.2% sodium chloride in water at pH 1.7. The quantitative extraction of butyltin compounds in a certified reference material (BCR-646) and naturally contaminated samples was achieved with recoveries ranging from 95 to 108% and at %RSD 0.02-1.00%. This HPLC method and optimum extraction conditions were used to determine the contamination level of butyltins in environmental samples collected from the Forth and Clyde canal, Scotland, UK. The values obtained severely exceeded the Environmental Quality Standard (EQS) values. Although high resolution methods are utilised extensively for this type of research, the developed method is cheaper in both terms of equipment and running costs, faster in analysis time and has comparable detection limits to the alternative methods. This is advantageous not just as a confirmatory technique but also to enable further research in this field.

Optimization of microwave-assisted extraction of polycyclic aromatic hydrocarbons from sediments.

The extraction methods for the determination of polycyclic aromatic hydrocarbons (PAHs) from spiked sediment containing benzo[k]fluoranthene, chrysene, acenaphthene, anthracene, carbazole and indeno[1,2,3-c,d]pyrene, using pressurised microwave-assisted extraction (PMAE) and sonication extraction were optimised. Each PAH in the spiked sediment was quantified by using the spectrofluorometric method. The optimised methods were compared on the extraction efficiency of 14 PAHs in a certified sediment reference material, LGC6188. Recoveries of 14 PAHs were performed by HPLC-DAD at 254 nm using the standard addition method. The results showed that the most extraction efficient method was pressurised microwave-assisted extraction with cyclohexane:acetone (3:2) for 15 min at 140% boiling point of acetone. Under this condition for the extracted certified sediment reference material recovery was 96.55%. It can be concluded from the experimental results that pressurised microwave-assisted extraction in a closed system provides a good alternative to sonication extraction for the extraction of PAHs from sediments. Furthermore, the PMAE was also applied to determine PAHs from sediments taken from the main entrance of Kasetsart University on Paholyotin road in Bangkok.