Assessing the effect of different natural dissolved organic matters on the cytotoxicity of titanium dioxide nanoparticles with bacteria

Titanium dioxide nanoparticles(TiO_2 NPs) are among the most widely manufactured nanomaterials on a global scale. However, prudent and vigilant surveillance, incumbent upon the scientific community with the advent of new technologies, has revealed potentially undesirable effects of TiO_2 NPs on biological systems and the natural environment during their application and discharge. Such effects are likely best evaluated by first assessing the fate of the TiO_2 NPs in natural environments. In this study, the effects of terrestrial humic acid(HA) and tannic acid(TA), two major members of the collective:dissolved organic matter(DOM), on the cytotoxicity of TiO_2 NPs to Escherichia coli were investigated in the presence and absence of natural sunlight. Qualitative(transmission electron microscopy(TEM)) and quantitative(LC50) analyses were employed in this study. In addition, the production of reactive oxygen species(ROS) in the form of UOH was further assessed—as HA or TA increased the production of ROS decreased. The inhibition of bacterial viability in the light treatment groups, with respective treatment organics at concentrations of 10 ppm, was less in TA than in terrestrial HA. SAS was used to analyze the treatment effect of individual factors of light irradiation, DOM, and concentration of TiO_2 NPs.     

Photodegradation of Benthiocarb

The photodegradation of ¹⁴C-benthiocarb in water, on a glass surface, on soil and silica gel TLC plates was studied. the study was designed to obtain some information of its dissipation and photodegradation under various laboratory conditions. Benthiocarb degrades readily when exposed to either sunlight or UV light (254 nm). However, it is degraded much faster by UV light than by sunlight. Also, benthiocarb decomposes faster in water or on a glass surface or silica gel surface than on a soil surface. the half-life of benthiocarb exposed to UV light was: 1 hr on glass surface; 1.5 hrs in water; 2 hrs on silica gel TLC plate; 20 hrs on soil TLC plate. Benthiocarb in water, and exposed to sunlight, had a half-life of approximately 3 days. the following major photodegradation products were identified: 4-chlorobenzyl alcohol; 4-chlorobenzaldehyde; 4-chlorobenzoic acid.     

Fine particle removal performance of a two-stage wet electrostatic precipitator using a nonmetallic pre-charger

A novel two-stage wet electrostatic precipitator (ESP) has been developed using a carbon brush pre-charger and collection plates with a thin water film. The electrical and particle collection performance was evaluated for submicrometer particles smaller than 0.01- 0.5 micrometer in diameter by varying the voltages applied to the pre-charger and collection plates as well as the polarity of the voltage. The collection efficiency was compared with that calculated by the theoretical models. The long-term performances of the ESP with and without water films were also compared in tests using Japanese Industrial Standards dust. The experimental results show that the carbon brush pre-charger of the two-stage wet ESP had approximately 10% particle capture, while producing ozone concentrations of less than 30 ppb. The produced amounts of ozone are significantly lower than the current limits set by international agencies. The ESP also achieved a high collection rate performance, averaging 90% for ultrafine particles, as based on the particle number concentration at an average velocity of 1 m/sec corresponding to a residence time of 0.17 sec. Higher particle collection efficiency for the ESP can be achieved by increasing the voltages applied to the pre-charger and the collection plates. The decreased collection efficiency that occurred during dust loading without water films was completely avoided by forming a thin water film on the collection plates at a water flow rate of 6.5 L/min/m(2).     

Effect of granular porous media on the composting of swine manure

This study investigated the feasibility of a bulking agent of granular porous media (GPM) for the composting of swine manure. Two lab-scale composting reactors were operated to evaluate the general performances and maturity parameters using GPM made of wastes from the Portland cement manufacturing processes as an alternative bulking agent. The overall volatile solid (VS) removal was 38.5% (dry basis). During the experiments, moisture content ranged between 41% and 53%, ensuring feasibility of microbial activity in composting. Cured compost showed proper maturity and low phytotoxicity, despite the slight decreases of CO(2) production and VS removal at the second batch operation. Various physico-chemical parameters of the cured compost met the regulatory standards reported elsewhere. The pH, carbon-to-nitrogen ratio, ammonia nitrogen and soluble organic carbon (SOC) of the cured compost were significantly correlated to the germination index (GI) using the seeds of Chinese cabbage and lettuce, indicating the progressive biodegradation of phytotoxins as well as organic matter. Consequently, the results obtained in this study demonstrate that GPM could contribute to the environmentally friendly and economical composting of problematic swine manure as a recyclable bulking agent.     

Isotopic evidence of nitrate sources and denitrification in the Mississippi River, Illinois

Anthropogenic nitrate (NO3-) within the Mississippi-Atchafalaya River basin and discharge to the Gulf of Mexico has been linked to serious environmental problems. The sources of this NO3- have been estimated by others using mass balance methods; however, there is considerable uncertainty in these estimates. Part of the uncertainty is the degree of denitrification that the NO3- has undergone. The isotopic composition of NO3- in the Mississippi River adjacent to Illinois and tile drain (subsurface drain) discharge in agricultural areas of east-central Illinois was examined using N and O isotopes to help identify the major sources of NO3- and assess the degree of denitrification in the samples. The isotopic evidence suggests that most of the NO3- in the river is primarily derived from synthetic fertilizers and soil organic N, which is consistent with published estimates of N inputs to the Mississippi River. The 1:2 relationship between delta18O and delta15N also indicate that, depending on sample location and season, NO3- in the river and tile drains has undergone significant denitrification, ranging from about 0 to 55%. The majority of the denitrification appears to have occurred before discharge into the Mississippi River.     

Evaluation and comparison of alarm reset modes in advanced control room of nuclear power plants

An automation function has been widely applied in main control room of nuclear power plants (NPPs). The alarm system of fourth nuclear power plant (FNPP) in Taiwan is also going to be developed with automatic technology that is expected to support the operators’ performance and reduce the number of alarms. In this study, an experiment with a training simulator as an advanced alarm system was conducted to compare the effects of different alarm reset modes on performance and subjective ratings. The objective was to evaluate the practicability of alarm system with only auto-reset function in FNPP. Results revealed that, using the auto-reset mode, participants had lower task load index (TLX) on effort in the first test trial and was more satisfied under multi-task condition. In contrast, using manual reset mode, participants were more satisfied on alarm handling, monitoring, and decision making. In other words, both reset modes are necessary to assist the operator in different aspects, but with only single reset mode is insufficient. The reset function in advanced alarm system therefore should be very flexible.     

Effects of arsenic on osmoregulation in the tilapia Oreochromis mossambicus reared in seawater

The effects of arsenic (As₂O₃) on plasma osmolarity, Na and K concentrations, the activity of gill Na–K-ATPase, and on the ultrastructure of gill chloride cells were compared between seawater tilapia (Oreochromis mossambicus) and freshwater tilapia in the Institute of Zoology, Academia Sinica, between 1989 and 1991. Arsenic was found to be more lethal in seawater tilapia [96 h LC₅₀ (median lethal concentration): 26.5 ppm] than in freshwater ones (71.7 ppm). No significant effect was found on plasma ion concentrations and osmolarity, enzyme activity or the ultrastructure of chloride cells in freshwater tilapia after 96 h exposure to 70 ppm arsenic. In contrast, 96 h exposure to 15 ppm arsenic caused evident effects in seawater tilapia: an increase in plasma osmolarity and activity of gill Na–K-ATPase, as well as better development of the chloride cell tubular system. These data suggest that the lethal effect of arsenic may be partially attributed to a hydromineral disturbance in seawater tilapia, but in freshwater tilapia arsenic perhaps causes destruction in some physiological mechanisms other than osmoregulation. The activation of gill Na–K-ATPase and chloride cells in seawater tilapia appears to indicate an adaptation in the osmoregulatory mechanism to arsenic exposure, i.e., to enhance secreting ions or arsenic in the gills.     

Shift in nutrient and plankton community in eutrophic lake following introduction of a freshwater bivalve

The impact of the freshwater bivalve Corbicula leana on plankton community dynamics was examined during a cyanobacterial bloom period. Nutrient and chlorophyll concentrations, primary productivity, and phytoplankton and zooplankton communities in the experimental enclosures were measured at 2-3 day intervals. The introduction of mussels reduced net primary productivity and phytoplankton and chlorophyll. Chlorophyll decreased immediately following addition of 100 mussels and then increased over time. After 600 mussels were added, chlorophyll decreased continuously from 87to 25 microg l(-1), approaching that in the mussel-free enclosure. Simultaneously, water transparency increased and concentrations of suspended solids and total phosphorus decreased. Mussel addition caused short-term increases in nutrient concentrations, especially following high-density treatment: phytoplankton density decreased, while cell density in the mussel-free enclosure increased. Zooplankton densities in the two enclosures were similar; however, carbon biomass in the mussel enclosure increased, associated with an increase in large zooplankton. The trophic relationship between phytoplankton and zooplankton was positive in the mussel-free enclosure and negative in the mussel-treatment enclosure, possibly reflecting effects of mussels on both consumer and resource control in the plankton community. Thus, filter feeding by Corbicula affects nutrient recycling and plankton community structure in a freshwater ecosystem through direct feeding and competition for food resources.     

Vibrio alginolyticus,a tetrodotoxin-producing bacterium,in the intestines of the fish Fugu vermicularis vermicularis

The influence of nutrient deprivation on cell-cycle progression was examined in two phytoplankton species, the diatom Thalassiosira weissflogii (actin) and the coccolithophorid Hymenomonas carterae (cocco II). The diatom was starved for nitrogen, silicon or both, whereas only nitrogen limitation was examined in H. carterae. In both species, nitrogen-starved cells were arrested in the early part of the cell cycle (G₁ phase). In the diatom, silicon-starvation arrested cells in late G₁ phase and also in the last part of the cell cycle (G₂+M). In all cases, cell-cycle arrest could be reversed by addition of fresh medium, but cell-cycling times during the first generation were increased in comparison to those in nutrient replete, steady-state growth conditions. These results supply evidence for simultaneous dual-nutrient limitation of population growth and provide a mechanistic interpretation for the division patterns observed in cultures where nutrients are supplied periodically.