Trivalent chromium solubility and its influence on quantification of hexavalent chromium in ambient particulate matter using EPA method 6800

Measurement of carcinogenic Cr(VI) in ambient PM is challenging due to potential errors associated with conversion between Cr(VI) (a carcinogen) and Cr(III) (an essential nutrient). Cr(III) conversion is a particular concern due to its >80% atomic abundance in total Cr. U.S. Environmental Protection Agency (EPA) method 6800 that uses water-soluble isotope spikes can be used to correct the interconversion. However, whether the enriched Cr(III) isotope spikes can adequately mimic the Cr(III) species originally in ambient PM is unknown. This study examined the water solubility of Cr(III) in ambient PM and discussed its influence on Cr(VI) measurement. Ambient PM₁₀ samples were collected on Teflon filters at four sites in New Jersey that may have different Cr emission sources. The samples were ultrasonically extracted with 5 mL DI-H₂O (pH 5.7) at room temperature for 40 min, and then analyzed by ion chromatography–inductively coupled plasma mass spectrometry (IC-ICPMS). Cr(III) was below detection limit (0.06 ng/m³) for all samples, suggesting water-soluble Cr(III) species, such as CrCl₃, Cr(NO₃)₃, and amorphous Cr(OH)₃, in the ambient PM were negligible. Therefore, the enriched ⁵⁰Cr(III) isotope spike (in the form of Cr(NO₃)₃) could not mimic the original ambient Cr(III). Only the conversion of ⁵³Cr(VI) (in the form of K₂CrO₄) was taken into account when correcting the interconversion. We then used NaHCO₃-pretreated MCE filters (prespiked with enriched isotope species) to measure Cr(VI) in the ambient PM₁₀. The samples were ultrasonically extracted at 60 C pH 9 solutions for 40 min followed by IC-ICPMS analysis. Due to the correction of Cr(VI) reduction, the Cr(VI) concentrations determined by EPA method 6800, 0.26 ± 0.16 (summer) and 0.16 ± 0.11(winter) ng/m³ (n = 64), were significantly greater than those by the external standard curve, 0.21 ± 0.17 (summer) and 0.10 ± 0.07 (winter) ng/m³ (n = 56) (p < 0.01, Student’s t-test). Our study revealed that appropriate application of EPA method 6800 is important because it only applies to soluble fraction of Cr species in ambient PM.

ImplicationsAccurate measurement of carcinogenic Cr(VI) in ambient PM is challenging due to conversion between Cr(VI) (a human carcinogen) and Cr(III) (a human essential nutrient). The conversion of Cr(III) is of particular concern due to its dominant presence in total Cr (>80%). This study examined the water solubility of Cr(III) in ambient PM that was collected at four locations in New Jersey. Then we discussed the influence of Cr(III) solubility on the application of EPA method 6800, which utilizes enriched isotope spikes to correct the interconversion. Our results suggested that appropriate application of EPA method 6800 is important because it only applies to soluble fraction of Cr species.     

Modification of mutagenic activity of benzo[a]pyrene by trace elements in the Ames assay

Benzo[a]pyrene (BaP) is one of the most ubiquitous environmental contaminants and exerts potent carcinogenicity and mutagenicity. In the presence of rat liver S9 mix, four trace elements, germanium (Ge), iron (Fe), zinc (Zn), and molybdenium (Mo), were included in the Ames Salmonella microsome/mutagenic assay to test their inhibitory effects on BaP-induced mutations. All trace elements were found to exert an inhibitory effect in tester TA98 and TA100 strains; Fe was the most potent among the elements tested, whereas Zn was weakly inhibitory to prevent mutations. The present findings demonstrate that the antimutagenic potential of trace elements, notably Fe, may be attributed to its modulatory effect on the bioactivation and detoxification processes of BaP.     

On eco-planning for an eco-demonstration park (EDP) and sustainability—Case study of the Luhua EDP in the Chongming Island of Shanghai, China

The background, concept, connotation, principles, and methods of eco-planning for an Eco-Demonstration Park (EDP) and sustainability were examined based on a case study of the Luhua EDP in the Chongming Island of Shanghai, China, which is an important part of Shanghai Eco-city planning and construction in the 21st century. By analyzing natural, social and economic conditions, calculating population using the land capacity eco-model, eco-function zoning, and eco-construction, an innovative eco-industrial structure and technical chain were formulated. A comprehensive eco-planning scheme for the EDP was proposed, including planning and management strategies for subsystems of efficient industry, good quality human settlement, high standard eco-construction and eco-tourism as well as effective environmental protection and attractive landscape. The EDP should be an area with coordinated and sustainable economic, social and environmental subsystems. Eco-planning for the EDP should be a very important part of eco-city planning and sustainability. The paper aims to set up a theoretical framework and practical basis for eco-planning and promoting harmony between human and nature.     

Characterization of ambient volatile organic compounds at a landfill site in Guangzhou,South China

Ambient air monitoring was conducted at Datianshan landfill, Guangzhou, South China in 1998 to investigate the seasonal and horizontal variations of trace volatile organic compounds (VOCs). Twelve sampling points over the Datianshan landfill were selected and samples were collected simultaneously using Carbontrap(TM) adsorption tubes. Thirty eight VOCs were detected in the winter, whereas 60 were detected in the summer. The VOC levels measured in summer were alkanes, 0.5-6.5 microg/m(3); aromatics, 2.3-1667 microg/m(3); chlorinated species, 0.2-31 microg/m(3); terpines, 0.1-34 microg/m(3); carbonyl species, 0.3-5.6 microg/m(3) and naphthalene and its derivatives, 0.4-27 microg/m(3). Compared to the summer samples the VOC levels in winter were much lower (mostly 1-2 orders of magnitude lower). The aromatics are dominant VOCs in landfill air both in winter and summer. High levels of alkylbenzene and terpines such as methyl-isopropylbenzene (max 1667 microg/m(3)) and limonene (max 162 microg/m(3)) cause undesirable odor. The similar correlation coefficients of BTEX in summer and winter suggest VOCs emissions were from landfill site sources. The variation of BTEX ratio at landfill site is different from that in the urban area of Guangzhou. It shows that the ambient VOCs at landfill site were different from the urban areas.     

The application of forward osmosis for simulated surface water treatment by using trisodium citrate as draw solute

Environmental Science and Pollution Research - In this study, trisodium citrate was used as draw solute in forward osmosis (FO) due to its biodegradability and easy reuse after FO dilution. The...     

Factors influencing silver recovery and power generation in bio-electrochemical reactors

The recovery of silver from Ag⁺ solution coupled with power generation was investigated in bio-electrochemical system (BES). In this system, chemical energy existing in the organic matter in the anode chamber can be converted biologically to electrical energy which can be used for the reduction of Ag⁺ ions in the cathode chamber. Results showed that type of substrate influenced the metabolic pathway and affected the cell voltage progression, and columbic efficiency. Silver recovery was not affected by increasing initial pH (2.0 to 7.0) and Ag⁺ concentration (100 to 1000 mg/L) in the catholyte, whereas power generation was improved. A maximum power density of 8258 mW/m³ and a columbic efficiency of 21.61% could be achieved with 1000 mg/L of Ag⁺. Ag⁺ ions were reduced to form metallic deposits as Ag⁰ crystals on the cathode surface, which were then confirmed by scanning electron microscope (SEM) image and energy dispersive X-ray (EDX) spectrum. The BES reactor had high silver removal (i.e., >96%) after 24 h of operation. When considering the crossover of Ag⁺ ions through the cation exchange membrane, the removal was in the range of 83.73–92.51%. This crossover was not considerable as compared to the Ag⁺ initial concentration. At higher initial Ag⁺ concentration (2000 mg/L), the silver removal decreased to 88.61% and the maximum power density decreased to 5396 mW/m³. This study clearly showed that BES can be employed for silver recovery, wastewater treatment, and also electricity generation.     

Estimating bulk optical properties of aerosols over the western North Pacific by using MODIS and CERES measurements

Over the western North Pacific, a large amount of land aerosols from Asian-Pacific countries is transported by the prevailing westerlies. This transport makes the radiative characteristics of these aerosols diverse, particularly when one compares those characteristics over the coastal sea with those over the open sea. In this paper we discuss a method that uses satellite data to obtain the single-scattering albedo (ω) and asymmetry factor (g) of atmospheric aerosols for two large-scale subdivisions—the coastal sea (within 250 km from the coast) and the open sea (the remaining area)—over the western North Pacific (110°E–180°, 20°N–50°N). Our estimation method uses satellite measurements, obtained over a six-year period (2000–2005), of aerosol optical depth (AOD) and shortwave fluxes at both the surface and the top of the atmosphere (TOA); the measurements are obtained using the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Clouds and the Earth's Radiant Energy System (CERES). For the two subdivisions, the estimated annual means of (ω,g) at 630 nm are significantly different: (0.94, 0.65) over the coastal sea and (0.97, 0.70) over the open sea. From a quantitative viewpoint, this result indicates that in comparison with aerosols over the open sea, those over the coastal sea show greater absorption and lesser forward scattering of solar radiation. The estimated optical properties are responsible for the aerosol surface cooling observed by MODIS and CERES, which is approximately 138 and 108 W m⁻² per AOD over the coastal sea and open sea, respectively.     

Spatial/temporal variations of elemental carbon, organic carbon, and trace elements in PM10 and the impact of land-use patterns on community air pollution in Paterson, NJ

An urban community PM10 (particulate matter < or = 10 microm in aerodynamic diameter) air pollution study was conducted in Paterson, NJ, a mixed land-use community that is interspersed with industrial, commercial, mobile, and residential land-use types. This paper examines (1) the spatial/temporal variation of PM10, elemental carbon (EC), organic carbon (OC), and nine elements; and (2) the impact of land-use type on those variations. Air samples were collected from three community-oriented locations in Paterson that attempted to capture industrial, commercial, and mobile source-dominated emissions. Sampling was conducted for 24 hr every 6 days from November 2005 through December 2006. Samples were concurrently collected at the New Jersey Department of Environmental Protection-designated air toxics background site in Chester, NJ. PM10 mass, EC, OC, and nine elements (Ca, Cu, Fe, Pb, Mn, Ni, S, Ti, and Zn) that had more than 50% of samples above detection and known sources or are toxic were selected for spatial/temporal analysis in this study. The concentrations of PM10, EC, OC, and eight elements (except S) were significantly higher in Paterson than in Chester (P < 0.05). The concentrations of these elements measured in Paterson were also found to be higher during winter than the other three seasons (except S), and higher on weekdays than on weekends (except Pb). The concentrations of EC, Cu, Fe, and Zn at the commercial site in Paterson were significantly higher than the industrial and mobile sites; however, the other eight species were not significantly different within the city (P > 0.05). These results indicated that anthropogenic sources of air pollution were present in Paterson. The source apportionment confirmed the impact of vehicular and industrial emissions on the PM10 ambient air pollution in Paterson. The multiple linear regression analysis showed that categorical land-use type was a significant predictor for all air pollution levels, explaining up to 42% of the variability in concentration by land-use type only.     

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.     

Effects of biodegradation and sorption by humic acid on the estrogenicity of 17β-estradiol

The removal of 17β-estradiol (E2) by biodegradation and sorption onto humic acid (HA) was examined at various HA concentrations. Subsequently, estrogenicity associated with E2 removal was estimated using E-screen bioassay. Results showed that E2 biodegradation and its subsequent transformation to estrone (E1) were significantly reduced with increasing HA concentration. In addition, the presence of nutrients enhanced the biodegradation of E2. Overall, E2 biodegradation was the dominating contributor to its removal, which demonstrated a significantly negative correlation with E2 sorption at various HA concentrations. The sorption of E2 by HA was significantly enhanced with increasing HA concentration. Estrogenicity associated with residual E2 showed that there existed a significant difference among various HA concentrations, with the lowest value in the absence of HA. The findings suggest that the presence of HA and nutrients in natural waters should be considered in assessing estrogenicity of environmental samples due to complex sorption and biodegradation processes.