Phosphorus Load Reduction Goals for Feitsui Reservoir Watershed, Taiwan

The present paper describes an effort for developing the total maximum daily load (TMDL) for phosphorus and a load reduction strategy for the Feitsui Reservoir in Northern Taiwan. BASINS model was employed to estimate watershed pollutant loads from nonpoint sources (NPS) in the Feitsui Reservoir watershed. The BASINS model was calibrated using field data collected during a 2-year sampling period and then used to compute watershed pollutant loadings into the Feitsui Reservoir. The simulated results indicate that the average annual total phosphorus (TP) loading into the reservoir is 18,910 kg/year, which consists of non-point source loading of 16,003 kg/year, and point source loading of 2,907 kg/year. The Vollenweider mass balance model was used next to determine the degree of eutrophication under current pollutant loading and the load reduction needed to keep the reservoir from being eutrophic. It was estimated that Feitsui Reservoir can becoming of the oligotrophic state if the average annual TP loading is reduced by 37% or more. The results provide the basis on which an integrated control action plan for both point and nonpoint sources of pollution in the watershed can be developed.     

Effects of the Heavy Metals Copper and Zinc on Zooxanthellae Cells in Culture

The growth of symbiotic algal cells (zooxanthellae) isolated from the coral, Montipora verrucosa under the influence of the heavy metals copper (Cu) and Zinc (Zn) was investigated. Zooxanthellae cells cultured in f/2 enriched seawater medium were subjected to a maximum Cu level of 42µg.l-1, Zn concentration of 509µg.l-1, and various combinations of the two metals, in ecotoxicological bioassays lasting up to 28 days. A Cu level of 40µg.l-1 caused significantly depressed specific growth rates of cell cultures obtained using a standard growth model. Low concentrations of the metals Cu and Zn in combination elicited synergistic effects of sublethal toxicity. The use of cultured zooxanthellae cells in bioassays investigating sublethal effects of heavy metal stress has relevant applications in the field of pollution monitoring.     

Pomacentrid Population Dynamics on Singapore Coral Reefs

Spatial distribution of the pomacentrids on Singapore reefs was assessed visually, while temporal change was studied within permanent quadrats established on a patch reef between 4 Jul and 30 Nov 1989. Partitioning of space, both horizontally and vertically, on the reef was observed in 15 species. The population of territorial damselfishes on the reef flat was less stable than on the reef slope over time, due to the seasonal occurrence of dense stands of the brown macroalgae, Sargassum. Space was found to be a limiting factor at the reef flat due to the high density of pomacentrids found there. Food resource was the limiting factor on the reef slope, where low light intensity due to sedimentation and lack of suitable substrate inhibited turf algal growth. Multi-specific recruitment of juveniles occurred in April and between mid-October and early November.     

Bio-oxidation of airborne volatile organic compounds in an activated sludge aeration tank

An activated sludge aeration tank (40 x 40 x 300 cm, width x length x height) with a set of 2-mm orifice air spargers was used to treat gas-borne volatile organic compounds (VOCs; toluene, p-xylene, and dichloromethane) in air streams. The effects of liquid depth (Z), aeration intensity (G/A), the overall mass-transfer rate of oxygen in clean water (KLaO2), the Henry's law constant of the tested VOC (H), and the influent gaseous VOC concentration (C0) on the efficiency of removal of VOCs were examined and compared with a literature-cited model. Results show that the measured VOC removal efficiencies and those predicted by the model were comparable at a G/A of 3.75-11.25 m3/m2 hr and C0 of approximately 1000-6000 mg/m3. Experimental data also indicated that the designed gas treatment reactor with KLaO2 = 5-15 hr(-l) could achieve > 85% removal of VOCs with H = 0.24-0.25 at an aerated liquid depth of 1 m and > 95% removal of dichloromethane with H = 0.13 at a 1-m liquid depth.     

Determination of source contributions to ambient PM2.5 in Kaohsiung, Taiwan, using a receptor model

Ambient particulates of PM2.5 were sampled at three sites in Kaohsiung, Taiwan, during February and March 1999. In addition, resuspended PM2.5 collected from traffic tunnels, paved roads, fly ash of a municipal solid waste (MSW) incinerator, and seawater was obtained. All the samples were analyzed for twenty constituents, including water-soluble ions, organic carbon (OC), elemental carbon (EC), and metallic elements. In conjunction with local source profiles and the source profiles in the model library SPECIATE EPA, the receptor model based on chemical mass balance (CMB) was then applied to determine the source contributions to ambient PM2.5. The mean concentration of ambient PM2.5 was 42.69-53.68 micrograms/m3 for the sampling period. The abundant species in ambient PM2.5 in the mass fraction for three sites were OC (12.7-14.2%), SO4(2-) (12.8-15.1%), NO3- (8.1-10.3%), NH4+ (6.7-7.5%), and EC (5.3-8.5%). Results of CMB modeling show that major pollution sources for ambient PM2.5 are traffic exhaust (18-54%), secondary aerosols (30-41% from SO4(2-) and NO3-), and outdoor burning of agriculture wastes (13-17%).     

Effect of wastewater composition on the calcium carbonate precipitation in upflow anaerobic sludge blanket reactors

Calcium carbonate often precipitates in anaerobic reactors treating wastewater with high calcium content. The aim of this paper is to study the effect of wastewater composition on calcium carbonate precipitation in upflow anaerobic sludge blanket (UASB) reactors. Two laboratory-scale UASB reactors were operated with calcium-containing influents using acetate and carbohydrate as substrate, respectively. There was an obvious accumulation of inorganic precipitate observed in the biogranules. Observations via scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) showed that the acclimated biogranules in the two reactors differed in microstructure. Calcium carbonate was found to have precipitated on the surface of acetate-degrading biogranules, but precipitated at the core of the carbohydrate-degrading biogranules. The results indicated that substrates had significant influence on the location of calcium carbonate precipitation in anaerobic granular sludge, which was expected due to the different methanogens distribution and pH gradient within the granular sludge degrading various substrates. Moreover, the location of calcium carbonate precipitation substantially affected the specific methanogenic activity (SMA) of the granular sludge. The SMA of the acetate-degrading biogranules dropped from $ 1.96 gCOD_{CH_4 } \cdot gVSS^{ - 1} \cdot d^{ - 1} $ 1.96 gCOD_{CH_4 } \cdot gVSS^{ - 1} \cdot d^{ - 1} to $ 0.61 gCOD_{CH_4 } \cdot gVSS^{ - 1} \cdot d^{ - 1} $ 0.61 gCOD_{CH_4 } \cdot gVSS^{ - 1} \cdot d^{ - 1} after 180-d of operation in the reactor. However, the SMA of the carbohydrate-degrading biogranules was not adversely affected by calcium carbonate precipitation.     

Selective reduction of NO by photo-SCR with ammonia in an annular fixed-film photoreactor

Gaseous NO was photocatalytically reduced at room temperature by photo-assisted selective catalytic reduction (photo-SCR) with ammonia over TiO₂ in this study. NO reduction efficiency and N₂ selectivity were determined from gases composition at the outlet stream of photoreactor. Effect of operating conditions, e.g. light intensity and inlet concentrations of ammonia and oxygen, on the NO reduction efficiency and N₂ selectivity were discussed to determine the feasible operating condition for photocatalytic reduction of NO. Experimental results showed that selective catalytic reduction of NO with ammonia over TiO₂ in the presence of oxygen was a spontaneous reaction in dark. The photoirradiation on the TiO₂ surface caused remarkable photocatalytic reduction of NO to form N₂, NO₂, and N₂O under 254 nm UV illuminations, while almost 90% of N₂ selectivity was achieved in this study. The ammonia and oxygen molecules played the roles of reductant and oxidant for NO reduction and active sites regeneration, respectively. The reduction of NO was found to be increased with the increase of inlet ammonia and oxygen concentrations until specific concentrations because of the limited active sites on the surface of TiO₂. The kinetic model proposed in this study can be used to reasonably describe the reaction mechanism of photo-SCR.     

星载SAR差分干涉测量提取汶川地震同震形变场

采用合成孔径雷达差分干涉测量技术对2008年5月12日四川汶川地震(Ms=8.0)的形变信息进行了提取,并开展了研究,利用地震前后ALOS/PALSAR数据,进行重复轨道差分干涉处理,得到了震前—震后的干涉条纹图和形变结果图。由雷达视向形变图可知,此次地震造成了隆起形变,最大形变出现在北川—映秀断裂带上,最大雷达视向形变量超过了90 cm,形变范围较大,川西的大部分地方都出现了不同程度的地表形变。结合川西的地质和地型构造情况,根据地震同震形变场的空间分布特征,对形变特征和震源构造进行了分析,发现二者有很好的一致性。     

Microbial dechlorination of polychlorinated biphenyls in anaerobic sewage sludge.

The potential of a chlorophenol (CP)-adapted consortium to dechlorinate polychlorinated biphenyls (PCBs) in sewage sludge was investigated. Results show that dechlorination rates differed significantly depending on sludge source and PCB congener. Higher total solid concentrations in sewage sludge and higher concentrations of chlorine in PCB resulted in slower dechlorination rates. No significant difference was found for 2,3,4,5-CB dechlorination from pH 6.0 to pH 8.0; however, dechlorination did not occur at pH 9.0 during a 41-day incubation period. Results show that at concentrations of 1 to 10 mg/L, the higher the PCB concentration, the faster the dechlorination rate. In addition, dechlorination rates were in the following order: methanogenic conditions > sulfate-reducing conditions > denitrifying conditions. The addition of acetate, lactate, pyruvate, and ferric chloride decreased lag times and enhanced dechlorination; however, the addition of manganese dioxide had an inhibitory effect. Dechlorination rates were also enhanced by the addition of PCB congeners, including 2,3,4-CB, 2,3,4,5-CB and 2,3,4,5,6-CB in mixture. Overall results show that the CP-adapted consortium has the potential to enhance PCB dechlorination. The optimal dechlorination conditions presented in this paper may be used as a reference for feasibility studies of PCB removal from sludge.     

N263溶剂萃取分析环境样品中微量放射性钍

本文用阴离子交换剂N_(263)作为钍的萃取剂,使待测样品中的钍与铀、镭、铁、稀土等杂质元素分离,并对萃取与反萃取,干扰离子,回收率等因素进行了研究.拟定了硝酸体系萃取,盐酸反萃取,偶氮胂Ⅲ比色测定的分析方法,同时测定了土壤、植物、煤及水样中钍含量.