Preparation of needle trap samplers to extract air compounds from indoor electric-vaporizing sources

In this study, gaseous benzene, toluene, ethylbenzene, and o-xylene (BTEX) were extracted by passive needle trap samplers (NTS) using divinylbenzene (DVB) particles (mesh sizes 60–80, 80–100, and 100–120, respectively) as packed sorbents. An aspirating pump measured sampling flow rates of NTS, and the relations between BTEX mass and sampling flow rates were sufficient to maintain the extraction performance of these self-designed DVB-NTS. Furthermore, this investigation compared the extraction efficiency of NTS with that of the 100-µm polydimethylsiloxane solid-phase microextration (PDMS SPME) fiber when applied to sample heating products from electric-vaporization anti-mosquito mats, and the experimental results indicated that NTS effectiveness increased with decreasing adsorbent particle diameter. Substantially less mass of gaseous BTEX was extracted using 100-µm PDMS SPME fiber than with NTS of 100–120 mesh DVB for 60-min TWA sampling of anti-mosquito mats. The 100–120 mesh DVB-NTS primarily adsorbed 4.2 ng acetone, 13.3 ng dichloromethane, and 4.5–25.3 ng C10–C12 alkanes.

Implications: The needle trap sampler (NTS) has been evaluated to be a device for sampling heating products from electric-vaporization anti-mosquito mats. Based on the experimental results, this investigation assessed NTS as suitable for occupational and environmental health applications.     

Toxicity measurements in aqueous solution during ozonation of mono-chlorophenols

The Microtox toxicity and Oxygen Uptake Rate (OUR) inhibition tests were conducted to monitor the variation of toxicity during ozonation of 2-chlorophenol (2-CP), 3-chlorophenol (3-CP) and 4-chlorophenol (4-CP) under neutral conditions. The results revealed that the oxidized 2-CP solution exhibited new toxicity to pure bacteria and mixed microorganisms in the early stage of ozonation. The largest inhibition of OUR appeared at one mol of applied ozone dosage per mol of initial 2-CP, and the percentage of inhibition was 63.8%. In addition, ozonated 3-CP and 4-CP also significantly induced new aqueous toxicity, if these toxic intermediates were not further ozonated. Comparing the variation of toxicity and the hydroxylated/chlorinated intermediates formed, 3-chloro-catechol, 2-chloro-2, 4-hexadienedioic acid and the dimmer compounds may be related to the sources of toxicity during the ozonation of 2-CP.     

Methane emission from fields with differences in nitrogen fertilizers and rice varieties in Taiwan paddy soils

Flooded rice fields are one of the major biogenic methane sources. In this study, methane emission rates were measured after transplanting in paddy fields with application of two kinds of nitrogen fertilizers (ammonium sulfate, NH4+-N and potassium nitrate, NO3(-)-N) and with two kinds of rice varieties (Japonica and Indica). The experiment was conducted in fields located at Tainan District Agricultural Improvement Station in Chia-Yi county (23 degrees 25'08"N, 120 degrees 16'26"E) of southern Taiwan throughout the first and the second crop seasons in 1999. The seasonal methane flux in the first crop season with NH4+-N and NO3(-)-N ranged from 2.48 to 2.78 and from 8.65 to 9.22 g CH4 m(-2); and the values ranged 24.6-34.2 and 36.4-52.6 g CH4 m(-2) in the second crop season, respectively. In the first crop season, there were significantly increased 3.1-3.7-fold in methane emission fluxes due to plantation of Indica rice. In comparison of two rice varieties, the Indica rice variety showed a tendency for larger methane emission than the Japonica rice variety in the second crop season. Moreover, ammonium sulfate treatment significantly reduced CH4 emissions by 37-85% emissions compared to potassium nitrate plots. It was concluded that the CH4 emission was markedly dependent on the type of nitrogen fertilizer and rice variety in Taiwan paddy soils.     

混凝沉淀在石油化工污水回用中的应用研究

在石油化工污水回用中，混凝沉淀是最基本的，也是极为重要的处理过程。用两项专利对混凝沉淀进行改进，使混凝沉淀效果大大提高，并具有很强的抗高浓度高浊度废水冲击的能力。另外，还对最佳停留时间和最佳投药量进行了研究。     

COMPARATIVE STUDY OF DROUGHT PREDICTION TECHNIQUES FOR RESERVOIR OPERATION1

ABSTRACT: Predicting the likelihood of a drought markedly enhances the efficiency of reservoir operations. This study applies the kriging method and time series analysis to predict inflows to Shihmen Reservoir in northern Taiwan. A subsequent reservoir operation simulation is employed to determine the drought lead time (DLT), the time before the onset of a drought. A more efficient reservoir operational strategy can be established with the aid of DLT and the probability of successful drought prediction (P s). Simulation results of reservoir operation over a period of three decades demonstrate that, at one month DLT, the kriging approach achieves 0.86 of P s for moderate droughts and 0.94 of P s for severe droughts. The kriging approach generally outperformed the time series approach in terms of DLT, P s of drought prediction, and the number of correctly predicted drought events.     

Degradation of aqueous carbon tetrachloride by nanoscale zerovalent copper on a cation resin

Nanoscale zerovalent copper supported on a cation resin was successfully synthesized to enhance the removal of carbon tetrachloride (CCl(4)) from contaminated water. The use of the cation resin as a support prevents the reduction of surface area due to agglomeration of nanoscale zerovalent copper particles. Moreover, the cation resin recycles the copper ions resulting from the reaction between CCl(4) and Cu(0) by simultaneous ion exchange. The decline in the amount of CCl(4) in aqueous solution results from the combined effects of degradation by nanoscale zerovalent copper and sorption by the cation resin; thus the amount of CCl(4) both in aqueous solution and sorbed onto the resin were measured. The pseudo-first-order rate constant normalized by the surface-area and the mass concentration of nanoscale zerovalent copper (k(SA)) was 2.1+/-0.1 x 10(-2)lh(-1)m(-2), approximately twenty times that of commercial powdered zerovalent copper (0.04 mm). Due to the exchange between Cu(2+) and the strongly acidic ions (H(+) or Na(+)), the pH was between 3 and 4 in unbuffered solution and Cu(2+) at the concentration of less than 0.1 mg l(-1) was measured after the dechlorination reaction. In the above-ground application, resin as a support would facilitate the development of a process that could be designed for convenient emplacement and regeneration of porous reductive medium.