Mutagenicity, genotoxicity and carcinogenic risk assessment of indoor dust from three major cities around the Pearl River Delta

The mutagenicity and genotoxicity of workplace dust including commercial office, secondary school, shopping mall, hospital, electronics factory and manufacturing plant in Hong Kong and settled house dust from Hong Kong, Shenzhen and Guangzhou were measured. Results indicated that indoor dust contained both frameshift and base pair substitution mutagens. Dust from manufacturing plant showed highest mutagenic potency on TA98±S9 and TA100±S9 activation, whereas, electronics factory showed highest genotoxicity with and without S9 activation. TA100 (-S9) mutagenic potency was significantly correlated with genotoxicity expressed as SOSIP (-S9) of workplace dust (r(2)=0.37, p<0.01). The total PAHs concentration of settled house dust from PRD ranged from 1.63 to 29.2μg/g. Linear regression analyses indicated that the PAHs likely accounted for about 45% of the TA98 with S9 mutagenic activity of workplace dust. TA98 (-S9) mutagenicity (r(2)=0.27, p<0.05) and SOSIP (-S9) of house dust (r(2)=0.41, p<0.01) were both significantly correlated with the number of inhabitants in the house. To achieve a more accurate cancer risk assessment, the oral bioaccessibility of B(a)A, Chry, B(b+k)F, B(a)P, D(ah)A and I(cd)P in different dust ranging from 1.3% to 17% was taken into account. Risk assessments indicated that about 26% of house dust samples resulted in unacceptable cancer risk (>1×10(-6)) for preschool children.     

Comparison of endotoxin levels and gram-negative bacteria under different conditions in microbial laboratories and a biowaste site

In this study, we assessed airborne endotoxin levels in university laboratories, hospital diagnostic laboratories, and a biowaste site. We also investigated indoor and outdoor sampling, sampling site, type of ventilation system, presence of open biowaste boxes, weather, and detection of Gram-negative bacteria (GNB). A total of 69 air samples were collected from 11 facilities in three institutions. Average total airborne endotoxin levels ranged from <0.01 to 10.02 EU m⁻³, with an overall mean of 1.03 EU m⁻³. Endotoxin levels were high in window-ventilated facilities, in facilities in which GNB were detected; levels were also high when it was rainy (all ps < 0.05). Endotoxin levels were significantly correlated with humidity (r = 0.70, p < 0.01). The presence of HVAC; humidity; and the presence of open biowaste boxes affect endotoxin levels in laboratories.     

Applying Zonation Methods and Tabu Search to Improve the Ground‐Water Modeling1

Abstract: An optimization procedure combining zonation methods with the Tabu Search method is proposed to identify the spatial distribution of hydraulic conductivity field. Three zonation methods, Voronoi diagram (VD), multiplicatively weighted Voronoi diagram (MWVD), and pattern zonation are adopted for the parameterization purposes. With the consideration of the homogeneity and the heterogeneity, there are four spatial distributions of hydraulic conductivity designed to test whether the parameter structure can be successfully identified. The fitting residual error is first considered to determine an adequate number of zones without over parameterization. Then, the parameter uncertainty is evaluated the decision of the number of zones. The results indicate that the MWVD performs better than other two methods because the MWVD has better flexibility in describing the zonal boundaries with small number of decision variables.     

Characterizing dissolved organic matter and evaluating associated nanofiltration membrane fouling

Natural organic matter (NOM) characteristics were determined for three ground waters exhibiting different water quality conditions. The water quality of the three feed waters collected at various water table depths was characterized by XAD-8/-4 resin adsorption, high performance size exclusion chromatography with ultraviolet and dissolved organic carbon (DOC) detections, and Fourier transform infrared spectroscopy (FTIR) to determine NOM fractionation, molecular weight, and NOM functional groups, respectively. Systematic studies were conducted to identify potential NOM foulants in ground water for nanofiltration (NF) membrane fouling. The results show that the hydrophobic fraction of NOM in all of the samples was significantly high (71-93%) compared to the hydrophilic (1.7-22.6%) and transphilic (5.3-6.6%) fractions. However, insignificant flux-decline (less than 5%) was observed for the highest DOC (36.9 mg l(-1)) and hydrophobic NOM (93%) containing groundwater compared to the other lesser DOC and hydrophobic NOM containing ground waters. This is presumably due to either higher fractions of hydrophilic and transphilic NOM or inorganic interactions that may be major foulants. Based on FTIR, aromatic foulants were observed at 1662 cm(-1) (CO-NH2 or CO conjugated with aromatic rings) for the fouled NF membrane with the relatively low DOC source waters. The contact angle of the clean membrane (52 degrees ) decreased with fouling up to 42-47 degrees for fouled membranes with the various samples.     

Practices in dioxin emission reduction by special regulatory enforcement and utilizing advanced control technologies for incinerators in Korea

This study strives to estimate the emission of dioxin and furthermore attempts to find the best technological control methods available for waste incinerators by investigating the emission status thereof. In order to incorporate the Stockholm Convention, a particular stringent law was promulgated in Korea and in recent years incinerators were forced to utilize better technological control. After the enforcement of special dioxin emission regulation in 2003, the average concentration of dioxin emitted from municipal and industrial waste incinerators decreased from 15.25 and 12.86 ng TEQ Nm(-3) to 5.53 and 4.96 ng TEQ Nm(-3) in 2001 and 2004, respectively. Based on test results at commercial plants, several best arranged sets of air pollution control devices (APCDs) were suggested in order to provide guidelines to help operators. These sets included combinations of spray dry absorbers, bag type filters, wet scrubbers, selective catalytic reductions and electrostatic precipitators. Different suggestions and real installations of APCD arrangement were investigated during the years around the regulation in effective. The results were presented depending on the capacity of the incinerators and different waste streams to observe the efforts to reduce dioxin emission by operators of incineration plants. The annual amount of dioxin emission from the incinerators is expected to be 212.5 g-TEQ in 2011 and 234.3g-TEQ in 2015, respectively, compared to 891.6g-TEQ recorded in 2001. The enforcement of new regulation and the installation of better APCDs showed the significant effect on such reduction. This reduction in dioxin emission from incinerators confirmed the nation's commitment to the regulatory requirement set by the Stockholm Convention.     

Studies on electrochemical recovery of silver from simulated waste water from Ag(II)/Ag(I) based mediated electrochemical oxidation process

In the Ag(II)/Ag(I) based mediated electrochemical oxidation (MEO) process, the spent waste from the electrochemical cell, which is integrated with the scrubber columns, contains high concentrations of precious silver as dissolved ions in both the anolyte and the catholyte. This work presents an electrochemical developmental study for the recovery of silver from simulated waste water from Ag(II)/Ag(I) based MEO process. Galvanostatic method of silver deposition on Ti cathode in an undivided cell was used, and the silver recovery rate kinetics of silver deposition was followed. Various experimental parameters, which have a direct bearing on the metal recovery efficiency, were optimized. These included studies with the nitric acid concentration (0.75-6M), the solution stirring rate (0-1400 rpm), the inter-electrode distance between the anode and the cathode (2-8 cm), the applied current density (29.4-88.2 mA cm(-2)), and the initial Ag(I) ion concentration (0.01-0.2M). The silver recovered by the present electrodeposition method was re-dissolved in 6M nitric acid and subjected to electrooxidation of Ag(I) to Ag(II) to ascertain its activity towards Ag(II) electrogeneration from Ag(I), which is a key factor for the efficient working of MEO process. Our studies showed that the silver metal recovered by the present electrochemical deposition method could be reused repeatedly for MEO process with no loss in its electrochemical activity. Some work on silver deposition from sulfuric acid solution of different concentrations was also done because of its promising features as the catholyte in the Ag(II) generating electrochemical cell used in MEO process, which include: (i) complete elimination of poisonous NO(x) gas liberation in the cathode compartment, (ii) reduced Ag(+) ion migration across Nafion membrane from anolyte to catholyte thereby diminished catholyte contamination, and (iii) lower cell voltage and hence lesser power consumption.     

Toxicity of carbaryl, diquat dibromide, and fluoranthene, individually and in mixture, to larval grass shrimp, Palaemonetes pugio

This study examined the toxicity of two pesticides (carbaryl and diquat dibromide) and one polycyclic aromatic hydrocarbon (fluoranthene), both singly and in mixture, to grass shrimp larvae (Palaemonetes pugio). These three chemicals are all present in coastal environments and can easily enter estuarine ecosystems. Fluoranthene was the most toxic chemical with a 96-h LC50 value of 32.45 microg/L, followed by carbaryl (43.02 microg/L) and diquat dibromide (1624 microg/L). In the chemical mixture tests, the binary carbaryl/diquat dibromide mixture and the ternary carbaryl/diquat dibromide/fluoranthene mixture had additive results.     

Suppression of Soot by Metal Additives During the Combustion of Polystyrene

This paper describes an experimental study on the suppression of soot by metal additives during the combustion of polystyrene (PS). A two-dimensional flame generated by using a Wolfhard-Parker type diffusion flame burner was used to simulate practical combustion situations. The PS was continuously fed to the burner and, by controlling the feed rate, the combustion was maintained at a steady state. The additives tested were the salts of Li, Na, K, Mg, Ca, Sr, and Ba, and the combinations of the salts of K and Ca, Sr, or Ba. These additives were added to the flame in the form of small drops of their aqueous solutions generated by an ultrasonic atomizer. Since the flow rate of the carrier gas (air) is very small, this addition causes no noticeable disturbance to the flame. The effectiveness of the alkali metals follows the order of their ease of ionization, i.e., K > Na > Li, and that of the alkaline-earth metals: Ba > Sr > Ca > Mg. At low addition rates, the effectiveness increases with increasing addition rate but becomes unaffected at high addition rates and the maximum percentage of soot suppressed is approximately 50 percent. The combinations of the two metals (i.e., K and Ca, Sr, or Ba) are much more effective than each single metal at the same addition rates and the maximum percentage of soot suppressed reaches approximately 90 percent. It is proposed that the alkaline-earth metals catalyze the ionization of the alkali metals, thus significantly enhancing the effect on soot suppression.     

Comparison of Real-Time Instruments Used To Monitor Airborne Particulate Matter

ABSTRACT

Measurements collected using five real-time continuous airborne particle monitors were compared to measurements made using reference filter-based samplers at Bakers-field, CA, between December 2, 1998, and January 31, 1999. The purpose of this analysis was to evaluate the suitability of each instrument for use in a real-time continuous monitoring network designed to measure the mass of airborne particles with an aerodynamic diam less than 2.5 μm (PM_2.5) under wintertime conditions in the southern San Joaquin Valley. Measurements of airborne particulate mass made with a beta attenuation monitor (BAM), an integrating nephelometer, and a continuous aerosol mass monitor (CAMM) were found to correlate well with reference measurements made with a filter-based sampler. A Dusttrak aerosol sampler overestimated airborne particle concentrations by a factor of ~3 throughout the study. Measurements of airborne particulate matter made with a tapered element oscillating microbalance (TEOM) were found to be lower than the reference filter-based measurements by an amount approximately equal to the concentration of NH₄NO₃ observed to be present in the airborne particles. The performance of the Dusttrak sampler and the integrating nephelometer was affected by the size distribution of airborne particulate matter. The performance of the BAM, the integrating nephelometer, the CAMM, the Dusttrak sampler, and the TEOM was not strongly affected by temperature, relative humidity, wind speed, or wind direction within the range of conditions encountered in the current study. Based on instrument performance, the BAM, the integrating nephelometer, and the CAMM appear to be suitable candidates for deployment in a real-time continuous PM_2.5 monitoring network in central California for the range of winter conditions and aerosol composition encountered during the study.     

Quantification of ventilation on distribution of gaseous pollutants emitted from stored swine manure

Abstract

This paper describes the quantification of the effects of ventilation on distribution of gaseous pollutants as a result of mass transfer from stored manure to ventilation air in a swine confinement building. A multiple airflow regions model is developed and used to simulate the dynamics of gaseous pollutants in any airspace within a ventilated slotted‐inlet enclosure. The model predictions compared favorably with the measured results adapted from a literature research at ventilation rates between 443 and 932 m³/hr (deviations of 5.1 ‐ 14.68%) for carbon dioxide and ammonia concentrations. A comparison between predictions and measured carbon dioxide concentrations derived from an environmental chamber test found deviations ranged from 3.1 ‐ 5.6% at ventilation rates between 281 and 995 m³/hr. The results suggest that the model can be experimentally applied between ventilation rates of 443 and 995 m³/hr. The model also capable of predicting air exchange rate required to maintain acceptable levels of gaseous pollutants in swine confinement buildings based on gas emission rates.