Influence of water quality parameters on occurrence of polybrominated diphenyl ether in sediment and sediment to biota accumulation

Polybrominated diphenyl ether (PBDE) concentrations in sediment and fish from 12 principal rivers in Taiwan were investigated to determine their association with water quality parameters as well as the biota-sediment accumulation factor (BSAF) in fish with different living patterns. The highest PBDE concentration in sediment was found in the Bajhang River (261 ng g^?1 dry weight (d.w.)) and the lowest in the Beinan River and the Da-an River (0.17 ng g^?1 d.w.). The PBDE concentrations in fish samples ranged from 1.28 ng g^?1 d.w. (Oreochromis niloticus niloticus) in the Yanshuei River to 33.7 ng g^?1 d.w. (Varico rhinos barbatulus) in the Da-an River. We conclude that PBDEs contamination in sediment was significantly affected by NH₃–N, pH, and DO. The BSAF results showed a parabolic trend from low- to high-brominated BDEs. Fish easily accumulated the congeners BDE-47, -100, -119, -126, and -154 from sediment. The BSAF decreased in the following order: PeBDE > HxBDE > TeBDE > other BDEs. Principle component analysis showed that demersal fish have different PBDE sources than do pelagic fish. We conclude that living and feeding habits are critical factors affecting PBDE accumulation in fish.     

Assessing the potential exposure risk and control for airborne titanium dioxide and carbon black nanoparticles in the workplace

Purpose  

This study assessed the potential exposure risks for workers in the workplace exposed to airborne titanium dioxide nanoparticles (TiO₂-NPs) and carbon black nanoparticles (CB-NPs). The risk management control strategies were also developed for the NP engineering workplace.     

Detrital flows through the feeding pathway of the oyster (Crassostrea gigas) in a tropical shallow lagoon: δ13C signals

The spatial relationships and linkage of the detrital flows among the water column, the sediment and the oyster Crassostrea gigas cultured in the water column were examined by using stable carbon isotopes (δ¹³C) in a tropical shallow lagoon from October 1996 to June 1997. The lagoon is located in southwestern Taiwan and is isolated from the sea by sand barriers except at two tidal inlets. It receives freshwater mainly from two rivers. A total of 12 stations were set up along three transect lines, each running across the lagoon from riverine to tidal inlet localities. The δ¹³C values of the water-column POM exhibited a marked sea–river gradient, with values depleted from a high of −21.7‰ at seaward stations to a low of −28.2‰ at riverine stations; those in the sedimentary POM (<62 μm grain size) also revealed this trend, but to a lesser extent. Oysters of two known ages, 6 months old (“old oysters”) and newly settled individuals (“young oysters”), were transplanted from one station to each of the remaining stations, while some were left at the original station. Values of δ¹³C in the muscle of transplanted oysters changed in parallel with the sea–river gradient of δ¹³C in POM (decreasing from −16.0 to −18.5‰ in old oysters and from −16.8 to −21.9‰ in young ones). The spatial sea–river gradient of the oyster's δ¹³C is related not only to the distance between the site that the oyster inhabits and sea or riverine environment, but also to the tidal flow pattern that surrounds its feeding place. Although the δ¹³C value of the sedimentary POM was correlated with that of the water-column POM, the δ¹³C value of the oyster tissue was significantly correlated with that of the water-column POM, but not with that of the sedimentary POM. This suggests that the oyster feeds primarily on water-column rather than sedimentary POM. Received: 30 April 1999 / Accepted: 15 December 1999     

Relationships between pesticides and organic carbon fractions in sediments of the Danshui River estuary and adjacent coastal areas of Taiwan

In order to understand the fate of pesticides in marine environments, concentrations of pesticides and different carbonaceous fractions were determined for surface sediments in the Danshui River and nearby coastal areas of Taiwan. The major compounds detected were tetrachlorobenzene, HCHs, chlordane, aldrin, DDDs, DDEs and DDTs. Total concentrations of pesticides in the sediments ranged from not detectable to 23 ng g(-1), with the maximum value detected near the discharge point of the marine outfall from the Pali sewage treatment plant. These results confirm that pesticides persist in estuarine and nearby coastal environments of the Danshui River well after their ban. Concentrations of total pesticides significantly correlate with concentrations of total organic carbon and black carbon in these sediments, suggesting that total organic carbon and black carbon regulate the distribution of trace organic pollutants in fluvial and coastal marine sediments.     

Effects of CH4 and CO on the reduction of nitric oxide to nitrogen in a discharge reactor

Additives are often added to enhance the efficiency of NO removal. This study uses a radio frequency (rf) discharge to consider the effect of added CH4 and CO to simulated NO/N2/O2/H2O mixtures on the elevation of NO conversion and the reduction of NO into N2. The enhancement levels of NO conversion when using various additives were found to be in this order: +CH4 > +CO > no additive. NO conversion reached 99.3%, 86.2%, and 77.6% when adding CH4, CO, and without additive, respectively, at inlet additive/NO molar ratio (R) = 5 and at 120 W. Moreover, the fraction of total N atoms converted from NO into N2 (FN2) was very high, reaching 99.4% and 99.5% when adding CH4 and CO, respectively, at R = 1 and at 120 W. The better operating conditions are using CH4 as the additive at R > or = 1 and a power of > 60 W to reach a higher NO conversion with a higher FN2. However, it should be noted that this rf plasma approach is not practical at this stage because of its relative low pressure.     

Decomposition of perfluorooctanoic acid by microwaveactivated persulfate: Effects of temperature, pH, and chloride ions

Microwave-hydrothermal treatment of persistent and bioaccumulative perfluorooctanoic acid (PFOA) in water with persulfate (S₂O₈²⁻) has been found effective. However, applications of this process to effectively remediate PFOA pollution require a better understanding on free-radical scavenging reactions that also take place. The objectives of this study were to investigate the effects of pH (pH = 2.5, 6.6, 8.8, and 10.5), chloride concentrations (0.01–0.15 mol·L⁻¹), and temperature (60°C, 90°C, and 130°C) on persulfate oxidation of PFOA under microwave irradiation. Maximum PFOA degradation occurred at pH 2.5, while little or no degradation at pH 10.5. Lowering system pH resulted in an increase in PFOA degradation rate. Both high pH and chloride concentrations would result in more scavenging of sulfate free radicals and slow down PFOA degradation. When chloride concentrations were less than 0.04 mol·L⁻¹ at 90°C and 0.06 mol·L⁻¹ at 60°C, presence of chloride ions had insignificant impacts on PFOA degradation. However, beyond these concentration levels, PFOA degradation rates reduced significantly with an increase in chloride concentrations, especially under the higher temperature.     

1985 Directory of Governmental Air Pollution Control Agencies

Abstract

Clay that contains kaolinite has been used extensively as a raw material for manufacturing of bricks and china at 900–1100 °C. This study used clay to stabilize the contaminant chromium(VI) [Cr(VI)] through a heating process at 500–1100 °C. X-ray absorption spectroscopic results indicated that the 500–900 °C heating process transformed hazardous Cr(VI) to nontoxic Cr(III); Cr₂O₃ was the species detected as most abundant. The 1100 °C heating process caused the formation of Cr₂SiO₅, which was not detected in the samples heated at 500–900 °C. Fourier transformed extended X-ray absorption fine structure spectra were fitted by use of WinXAS software. Phase shifts and backscatter(ing) amplitudes for specific atom pairs, based on the crystallographic data for CrO₃ and Cr₂O₃, were theoretically calculated with the FEFF software. The processed XAS data show that the first shell coordination numbers were similar to each other as the temperature was increased from 500 to 900 °C and 1100 °C, implying that their Cr(III) crystallite size was relatively similar. The interatomic distance between the target center element and the first shell for the 500– 1100 °C samples was 1.98Å. The Debye-Waller factor for the 1100 °C sample was increased compared with the 500 and 900 °C samples and probably indicates the formation of Cr₂SiO₅.