No abstract

Dili is the capital city of Timor-Leste and has the highest population comparing to other cities. The quality of fresh water streams in Dili was evaluated using the larval himedaka acute toxicity assay combined with active sampling. Ten liters of grab water samples were collected from the Fatuhada, Campo Alor, Caicoli, and Kuluhun streams, filtered and thereafter concentrated using the Sep-Pak ® Plus PS-2 cartridges. Subsequently, the sorbed chemicals were eluted from the Sep-Pak cartridges and prepared for toxicity assays and gas chromatography/mass spectrometry (GC/MS) analysis. Toxicity was evaluated by exposing the larval himedaka (Oryzias Latipes var.) to different concentration ratios (100, 50, 20, and 10 folds) of eluted chemicals and then counting the number of dead himedaka at 0.5, 1, 2, 3, 6, 12, 24, and 48 h during the test. Toxicity results showed that Caicoli had the highest toxicity level, followed by Campo Alor, and then Kuluhun. However, no toxicity was detected in Fatuhada. The lethal dilution ratio (LDR50) values for these streams were; >0.10, 0.07, 0.03, and <0.01, respectively. A comparison was made between Japan and Timor-Leste to show the difference in the toxicity levels of the water streams between the developed and developing countries. The toxicity level in both Timor-Leste and Japanese water streams was high. According to the GC/MS analysis, the detection of coprostanol and many hydrocarbon components of fuel oils in Timor-Leste streams reflects the negative effects of anthropogenic activities on water streams. GC/MS analysis is limited by the number of chemicals that can be identified, and it cannot explain about the effect of the detected chemicals. A further bioassay test is required to assay the toxicities from river water with multicomponent chemicals or chemicals whose toxicity has not yet been evaluated.

The applicability of Empore TM styrene-divinylbenzene reverse-phase sulfonated (SDB-RPS) passive sampler disks for integrative sampling of organic chemicals in river water was investigated to evaluate toxicity levels via bioassay using larval medaka (Oryzias latipes). Those disks were deployed for periods of 1, 2, 3, 7, and 10 days (PS different period), and at 2-day intervals over the 10-day sampling period (PS interval). Six 10-L grab samples were collected at the same time as PS interval sampling, and thereafter concentrated using Sep-Pak ® Plus PS-2 cartridges (GS). Adsorbed chemicals were subsequently eluted from Sep-Pak cartridges and SDB-RPS disks and prepared for toxicity tests and gas chromatography/mass spectrometry analysis. Compared with all PS samples, GS samples showed strong toxicity results. None of the PS interval samples showed toxicity, even though the amount of adsorbed chemicals in the 2nd interval sample was higher than in PS 7-and 10-day samples, which showed toxicity. Furthermore, the PS 10-day sample contents were not equivalent to the accumulated amounts of adsorbed chemicals in PS interval samples. On the basis of these results, it is assumed that during long-term sampling, chemicals adsorbed on disks might be affected by desorption or decomposition, and that some might be converted to more toxic compounds.