Deposition fluxes of PCDD/Fs in a reservoir system in northern Taiwan

In this study, polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/F) concentrations and depositions in ambient air, water column and sediment were measured at a coupled reservoir-watershed system in northern Taiwan. The atmospheric PCDD/F concentration measured in the vicinity of the reservoir ranged from 4.9 to 39 fg I-TEQ m⁻³ and the Asian dust storm in February accounted for the peak value, which corresponded to a total suspended particle concentration of 128 μg m⁻³. The atmospheric PCDD/F deposition ranged from 1.4 to 19 pg I-TEQ m⁻² d⁻¹, with higher deposition occurring during winter and spring (long-range transport events). During summer, when atmospheric deposition is lower, consecutive tropical cyclones (typhoons) bring heavy rainfall that enhances soil erosion and creates turbidity-driven intermediate flow. This results in significantly higher PCDD/F deposition in water column of the reservoir at 70 m water depth (179 pg I-TEQ m⁻² d⁻¹) than at 20 m (21 pg I-TEQ m⁻² d⁻¹) during typhoon event. The accumulation rate of PCDD/Fs (9.1 ng I-TEQ m⁻² y⁻¹) in the reservoir sediments (depth: 0-2 cm) was consistent with PCDD/F deposition obtained from water column (6.1 and 8.3 ng I-TEQ m⁻² y⁻¹); however, it is significantly higher when compared to the atmospheric deposition (2.0 ng I-TEQ m⁻² y⁻¹). Based on the mass balance between the measurements of atmospheric deposition and sinking particles in water column, around 54-74% of PCDD/F inputs into the reservoir were contributed by the catchment erosion during normal period. However, the PCDD/F input contributed by the enhanced catchment erosion significantly increased to 90% during intensive typhoon events.     

Pressure-assisted ozonation of PCB and PAH contaminated sediments

Sediment contamination by recalcitrant organics such as polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) is prevalent and of a great concern. Remediation efforts are hampered by the hydrophobic nature of the contaminants that limits their availability as well as by the sediment matrix that limits their exposure to treatment agents. Using contaminated sediment samples from the Passaic River, St. Louis River, Waukegan Harbor, and Wells National Estuarine Research Reserve, this research demonstrated a new ozonation technique that incorporates rapid, successive cycles of pressurization (690 kPa) and depressurization, enabling more effective treatment than conventional ozonation would. Conventional ozonation reached maximum 60% and 40% removal of PAHs from the Passaic River (40 mg kg(-1) initially) and St. Louis River sediment (520 mg kg(-1) initially), respectively, in 1h; however, removals ceased despite prolonged treatment for 2h. The pressure-assisted technique removed 96% of PAHs from both river sediments within 1h; it completely removed both PAHs (16 mg kg(-1) initially) and PCBs (5.1 mg kg(-1) initially) from the Waukegan Harbor sediment in 0.5 h. The heightened treatment is explained by soil aggregate fracturing upon pressure cycles that exposes the contaminants as well as by the confluence of hydrophobic contaminants and O(3) at the gas-liquid interface in the presence of microbubbles. The technique is expected to accelerate O(3) treatment of a wide range of organic contaminants, and it may provide treatment to dredged and stored contaminated sediment.     

制备条件对Mn-Fe/TiO2催化剂低温脱硝性能的影响

通过浸渍法制备了一系列Mn-Fe/TiO2催化剂,并采用XRD技术对其进行了表征,考察了锰前体种类、负载量（活性组分质量占载体质量的百分比）、Fe含量（Fe物质的量占活性组分物质的量的百分比）、焙烧温度等因素对催化剂低温选择性催化还原NO性能的影响。实验结果表明：以乙酸锰为前体制备的催化剂的脱硝活性明显高于以硝酸锰为前体制备的催化剂;负载量的增加有利于脱硝活性的提高,而Fe的添加对提高催化剂的活性有重要作用,但Fe含量超过15%后,对催化剂脱硝性能的影响并不明显;焙烧温度超过650 ℃时会使活性组分的结晶度提高,导致脱硝活性的降低。在锰前体为乙酸锰、负载量为15%、Fe含量为15%、焙烧温度为500 ℃、焙烧时间为6 h、反应温度为200 ℃的条件下,Mn-Fe/TiO2催化剂的NO转化率约为95%。     

Siting analyses for water quality sampling in a catchment

Pollution loads discharged from upstream development or human activities significantly degrade the water quality of a reservoir. The design of an appropriate water quality sampling network is therefore important for detecting potential pollution events and monitoring pollution trends. However, under a limited budgetary constraint, how to site an appropriate number of sampling stations is a challenging task. A previous study proposed a method applying the simulated annealing algorithm to design the sampling network based on three cost factors including the number of reaches, bank length, and subcatchment area. However, these factors are not directly related to the distribution of possible pollution. Thus, this study modified the method by considering three additional factors, i.e. total phosphorus, nitrogen, and sediment loads. The larger the possible load, the higher the probability of a pollution event may occur. The study area was the Derchi reservoir catchment in Taiwan. Pollution loads were derived from the AGNPS model with rainfall intensity estimated using the Thiessen method. Analyses for a network with various numbers of sampling sites were implemented. The results obtained based on varied cost factors were compared and discussed. With the three additional factors, the chosen sampling network is expected to properly detect pollution events and monitor pollution distribution and temporal trends.     

Application of integrated GIS and multimedia modeling on NPS pollution evaluation

In Taiwan, nonpoint source (NPS) pollution is one of the major causes of the impairment of surface waters. I-Liao Creek, located in southern Taiwan, flows approximately 90 km and drains toward the Kaoping River. Field investigation results indicate that NPS pollution from agricultural activities is one of the main water pollution sources in the I-Liao Creek Basin. Assessing the potential of NPS pollution to assist in the planning of best management practice (BMP) is significant for improving pollution prevention and control in the I-Liao Creek Basin. In this study, land use identification in the I-Liao Creek Basin was performed by properly integrating the skills of geographic information system (GIS) and global positioning system (GPS). In this analysis, 35 types of land use patterns in the watershed area of the basin are classified with the aid of Erdas Imagine process system and ArcView GIS system. Results indicate that betel palm farms, orchard farms, and tea gardens dominate the farmland areas in the basin, and are scattered around on both sides of the river corridor. An integrated watershed management model (IWMM) was applied for simulating the water quality and evaluating NPS pollutant loads to the I-Liao Creek. The model was calibrated and verified with collected water quality and soil data, and was used to investigate potential NPS pollution management plans. Simulated results indicate that NPS pollution has significant contributions to the nutrient loads to the I-Liao Creek during the wet season. Results also reveal that NPS pollution plays an important role in the deterioration of downstream water quality and caused significant increase in nutrient loads into the basin's water bodies. Simulated results show that source control, land use management, and grassy buffer strip are applicable and feasible BMPs for NPS nutrient loads reduction. GIS system is an important method for land use identification and waste load estimation in the basin. Linking the information of land utilization with the NPS pollution simulation model may further provide essential information of potential NPS pollution for all subregions in the river basin. Results and experience obtained from this study will be helpful in designing the watershed management and NPS pollution control strategies for other similar river basins.     

Biotransformation of cyanide to methane and ammonia by Klebsiella oxytoca

Klebsiella oxytoca, isolated from cyanide-containing industrial wastewater, was shown to be able to biodegrade cyanide to non-toxic endproducts using cyanide as the sole nitrogen source. In this study, ammonia was one of the detected endproduct of cyanide biodegradation by the concentrated resting cells of K. oxytoca. Moreover, cyanide has been shown to be biotransformed to methane through the actions of concentrated resting cells. Biodegradation of cyanide by cell-free extracts was not observed, which might be due to the inactivation of nitrogenase (an oxygen-labial enzyme) caused by the oxygen exposure after cell disruption. Results show that the cyanide consumption by resting cells of K. oxytoca was induced when the pretreatment of these cells with cyanide was conducted. However, the cyanide-degrading capability of resting cells pretreated with ammonia was inhibited. The inhibition of cyanide degradation by resting cells of K. oxytoca was affected by the ammonia concentration. This might result from the suppression of nitrogenase activity of K. oxytoca by ammonia since nitrogenase was suggested to be the sole cyanide-degrading enzyme during the cyanide degradation process. Results from this study also show that the processes of cyanide biodegradation and ammonia production by resting cells occurred simultaneously. This suggests that the utilization of cyanide as nitrogen source by K. oxytoca might proceed using ammonia as an assimilatory substrate.     

Laboratory column studies for evaluating a barrier system for providing oxygen and substrate for TCE biodegradation

The industrial solvent trichloroethylene (TCE) is among the most ubiquitous chlorinated compounds found in groundwater contamination. The objective of this study was to develop a biobarrier system containing oxygen-organic releasing material to enhance the aerobic cometabolism of TCE in situ. The oxygen-organic material, which contains calcium peroxide and peat, is able to release oxygen and primary substrates continuously upon contact with water. Batch experiments were conducted to design and identify the components of the oxygen-organic releasing material, and evaluate the oxygen and organic substrate (presented as COD equivalent) release from the designed oxygen-organic material. The observed oxygen and chemical oxygen demand (COD) release rates were approximately 0.0246 and 0.052 mg/d/g of material, respectively. A laboratory-scale column experiment was then conducted to evaluate the feasibility of this proposed system for the bioremediation of TCE-contaminated groundwater. This system was performed using a series of continuous-flow glass columns including a soil column, an oxygen-organic material column, followed by two consecutive soil columns. Aerobic acclimated sludges were inoculated in all three soil columns to provide microbial consortia for TCE biodegradation. Simulated TCE-contaminated groundwater with a flow rate of 0.25 l/day was pumped into this system. Effluent samples from each column were analyzed for TCE and other indicating parameters (e.g., pH, dissolved oxygen). Results show that the decreases in TCE concentrations were observed over a 4-month operating period. Up to 99% of TCE removal efficiency was obtained in this passive system. Results indicate that the continuously released oxygen and organic substrates from the oxygen-organic materials enhanced TCE biotransformation. Thus, the biobarrier treatment scheme has the potential to be developed into an environmentally and economically acceptable remediation technology.     

Estimating the ozone formation potential of volatile aromatic compounds in vehicle tunnels.

Two vehicle tunnels located in the Taipei area were selected to study the ozone formation potential of volatile aromatic compounds (VACs). Air samples in the two tunnels were collected using canisters. Analysis of VACs was conducted with a gas chromatograph equipped with a mass spectrometer. The total VOCs concentrations in Zefun tunnel ranged from 483.5 to 1032.2 (micrograms/m3) which increased with the increase in traffic volume. In the Lishin tunnel, the total VACs concentration ranged from 356.6 to 1961.3 (micrograms/m3) which was not well correlated with the traffic volume. The most predominant VACs in these vehicle tunnels were toluene and xylenes. Although the traffic volume and types of vehicles were not exactly the same, the characteristic ratios of the VACs concentrations were found to be similar. These results indicated that the existence of a specific characteristic ratio of VAC concentration was affected by the mobile sources. The maximum ozone formation potential resulted from the vehicles in the Lishin motorcycle tunnel which had higher values than the Zefun tunnel and much higher than the SPECIATE databases in the US via weighting the maximum incremental reactivity (MIR) scale.     

Effect of formaldehyde on Cu(II) removal from synthetic complexed solutions by ion exchange

The effect of formaldehyde (HCHO) on the ion exchange of Cu(II) from an equimolar EDTA (ethylenediaminetetraacetic acid, H(4)L) solution with a strong-base Amberlite IRA-400 resin was studied. Experiments were conducted as a function of the initial concentration of Cu(II) (0.5-10 mM), solution pH (1.0-6.0), HCHO concentration (0-6 vol%), and temperature (15-35 degrees C). It was shown that the amount of exchange of Cu(II), which exists in the form of complexed anions CuL(2-), increased with increasing solution pH and reached a plateau at an equilibrium pH (pH(e)) of 3.5. However, the amount of exchange decreased with increasing HCHO concentration up to 3 vol% but then slightly decreased with a further increase in HCHO concentration. Such effect of added HCHO was determined by the following two factors: the competitive exchange of HCOO(-) anions and the enhanced exchange of Cu(I) in the form of complexed anions CuL(3-). The exchange isotherm obtained at a fixed pH(e) could be well described by the Langmuir equation. The isosteric enthalpy change for the present ion exchange process was also evaluated and discussed.     

Dietary separation between two blennies and the Pacific gregory in northern Taiwan: evidence from stomach content and stable isotope analyses

Two blennies, Ecsenius lineatus Klausewitz and Ecsenius namiyei (Jordan and Evermann), and a cohabiting territorial damselfish, the Pacific gregory, Stegastes fasciolatus (Ogilby), were collected from shallow reefs in northern Taiwan between September and November 2004, and in October 2005 for stomach content and δ ¹³C and δ ¹⁵N analyses in an effort to study how extensively their food sources overlapped and to delineate the pattern of cohabiting interactions. These analyses showed differences in food use between the Ecsenius blennies and S. fasciolatus. However, there were inconsistencies. Epiphytic algae were their major food items of E. namiyei and E. lineatus. Macroalgae were rarely taken. Nevertheless, δ ¹³C and δ ¹⁵N signatures suggested that E. namiyei and E. lineatus might have assimilated mainly macroalgae-derived detritus instead of epiphytic algae. In contrast, macroalgae were the major food items of S. fasciolatus, followed by epiphytic algae. Differences in both δ ¹³C and ¹⁵N values indicated that for S. fasciolatus, algae (both macroalgae and epiphytic algae) might not be as important as the stomach contents showed. Instead, polychaetes were possibly its major food source. Differences between stomach contents and evidence from the separation of stable isotope signatures between blennies and the Pacific gregory indicate that some of the interspecific interactions derived from exploitative competition may have been alleviated. Moreover, their widespread territory overlap is possibly a sign of mutualism: S. fasciolatus allows territory sharing, while Ecsenius blennies, in return, clean up the algal mat by removing sand and detritus.