No description available.

No description available.

No description available.

In urban environments, ozone air pollution, poses significant risks to respiratory health. Fixed site monitoring is the primary method of measuring ozone concentrations for health advisories and pollutant reduction, but the spatial scale may not reflect the current population distribution or its future growth. Moreover, formal methods for the placement of ozone monitoring sites within populations potentially omit important spatial criteria, producing monitoring locations that could unintentionally underestimate the exposure burden. Although air pollution affects all people, the combination of underlying health, socioeconomic and demographic factors exacerbate the impact for socially vulnerable population groups. A need exists for assessing the spatial representativeness and data gaps of existing pollution sensor networks and to evaluate future placement strategies of additional sensors. This research also seeks to understand how air pollution monitor placement strategies may neglect social vulnerabilities and therefore, potentially underestimate exposure burdens in vulnerable populations.

Polychlorinated biphenyls (PCBs) are toxic and persistent chemicals that have been largely dispersed into the environment. The biological and abiotic transformations of PCBs often generate hydroxylated derivatives, which have been detected in a variety of environmental samples, including animal tissues and feces, water, and sediments. Because of their toxicity and widespread dispersion in the environment, hydroxylated PCBs (OH-PCBs) are today increasingly considered as a new class of environmental contaminants. Although PCBs are known to be susceptible to microbial degradation under both aerobic and anaerobic conditions, bacterial degradation of OH-PCBs has received little attention. The overall objective of this study is therefore to evaluate the transformation of mono-hydroxylated PCBs by the well characterized aerobic PCB-degrading bacterium, Burkholderia xenovorans LB400. In order to achieve our overall objective, a series of model mono-hydroxylated PCBs have been selected and they are used to determine the toxicity of hydroxylated congeners toward the bacterium B. xenovorans LB400. The biodegradation kinetics and metabolic pathways of the selected OH-PCBs by B. xenovorans LB400 are then characterized using GC/MS. To understand further the molecular basis of the metabolism of OH-PCBs by B. xenovorans LB400, gene expression analyses are conducted using reverse-transcription real-time (quantitative) polymerase chain reaction (RT-qPCR) and microarray technology. More formally, the specific aims of the proposed research are stated as follows: (1) To evaluate the toxicity of selected mono-hydroxylated derivatives of lesser-chlorinated PCBs toward the bacterium B. xenovorans LB400. (2) To assess the degradation of the selected OH-PCBs by B. xenovorans LB400. (3) To gain further understanding of the molecular bases of the metabolism of the selected OH-PCBs by B. xenovorans LB400. Three hydroxylated derivatives of 4-chlorobiphenyl and 2,5-dichlorobiphenyl, including 2'-hydroxy-, 3'-hydroxy-, and 4'-hydroxy- congeners, were significantly transformed by Burkholderia xenovorans LB400 when the bacterium was growing on biphenyl (biphenyl pathway-inducing conditions). On the contrary, only 2'-OH-4-chlorobiphenyl and 2'-OH-2,5-dichlorobiphenyl were transformed by the bacterium growing on succinate (conditions non-inductive of the biphenyl pathway). Gene expression analyses showed that only exposure to 2'-OH-4-chlorobiphenyl and 2'-OH-2,5-dichlorobiphneyl resulted in induction of key genes of the biphenyl pathway, when cells grown on succinate. These observations suggest that 2'OH-PCBs were capable of inducing the genes of biphenyl pathway. These results provide the first evidence that bacteria are able to cometabolize PCB derivatives hydroxylated on the non-chlorinated ring. Genome-wide transcriptional analyses using microarrays showed that 134 genes were differentially expressed in cells exposed to biphenyl, 2,5-dichlorobiphenyl, and 2'-OH-2,5-dichlorobiphneyl as compared to non-exposed cells. A significant proportion of differentially expressed genes were simultaneously expressed or down regulated by exposure to the three target compounds i.e., biphenyl, 2,5-DCB, and 2'-OH-2,5-DCB, which suggests that these structurally similar compounds induce similar transcriptional response of B.xenovorans LB400. Results of this study may have important implications for the natural attenuation of PCBs and fate of OH-PCBs in the environment. The recalcitrance to biodegradation and the high toxicity of some OH-PCBs may provide a partial explanation for the persistence of PCBs in the environment. / Civil Engineering

Polychlorinated biphenyls (PCBs) are widespread persistent organic pollutants. The metabolism of PCBs by various organisms involves many steps that can lead to the formation of a wide range of metabolites. These metabolites frequently exhibit a toxicity and biodegradability different than the parent compounds. There is currently little information available about the biological effects of PCB hydroxylated metabolites that can be generated by various organisms and potentially released into the environment. The objective of the present research is to compare the toxicity of selected PCB congeners and their corresponding mono-hydroxylated metabolites. To achieve this objective, the following specific aims were performed: (1) to determine the effect of selected PCBs and PCB hydroxylated metabolites on the growth rate of a model PCB-degrading bacterium, Burkholderia xenovorans LB 400, (2) to determine the microbial toxicity of PCBs and PCB metabolites using the bioluminescent assay Microtox®, and (3) to determine the estrogenicity of PCBs and PCB metabolites using the Yeast Estrogen Screen assay (YES). The effects of a range of PCBs (PCB-2, -3, -8, -9, -30, -35, -36, -39, -61, -68, and -79) and their mono-hydroxylated metabolites on the growth rate of the PCB degrader, Burkholderia xenovorans LB400, were recorded. The results showed that the parent PCBs (50 mg L-1) did not affect the growth rate of LB400 although their hydroxylated metabolites strongly inhibited microbial growth. Using Microtox® assay, Parent PCBs (50 mg L-1) did not exhibit observable toxicity, while their hydroxylated metabolites showed a high level of toxicity (EC50 ranges from 2 mg L-1 to 46 mg L-1). Results using the YES assay also showed that the estrogenicity of hydroxylated metabolites of PCBs (50 mg L-1) was higher than the parent PCBs. The results obtained from the present study show that mono-hydroxylated metabolites of PCBs are more toxic than the corresponding parent PCBs. Because hydroxylated PCB derivatives are produced by a range of organisms and potentially released into the environment, this work raises new concerns associated with the environmental fate of PCBs. / Civil Engineering

Heavy metals like cadmium, lead and zinc pose a significant threat to human health and environment. Several factors such as pH, EH, organic matter and clay content of the soil affect the bioavailability of such heavy metals in the environment. The presence of several naturally occurring minerals such as calcite (calcium carbonate, CaCO3) and calcium oxalate (CaC2O4.) in the environment significantly influence the fate and transport of some of the heavy metal cations. Sequestration of heavy metals such as cadmium (Cd) and zinc (Zn) from solution by calcite has been clearly demonstrated in the literature. However, studies on heavy metal sequestration by calcite and calcium oxalate from a multi-metal environmental that represents real world situations are rare. In this contribution, column flow studies of Cd and Zn sequestration by calcite exposed to influent solutions saturated or non-saturated with calcite and containing either 1 mg/L of Cd, 1 mg/L of Zn or combined 1 mg/L of Zn and Cd, followed by desorption of the sequestered metals were conducted. Complementary scanning electron microscopy (SEM) coupled with electron dispersive x-ray spectroscopy (EDS) data were generated. Kinetic studies show that reaction rates of Cd and Zn with calcite are governed by a simple rate law with reaction orders of less than 1 (0.02 - 0.07) indicating at least mathematically, the occurrence of reactions that went to completion if the reaction orders did not change. When the influent solution contains a single cation, the rate of Zn removal from solution by calcite and calcium oxalate is greater than Cd removal rate. However in a multi-cation environment, cadmium removal rate was greater than zinc removal rate. MINTEQA2 a geochemical equilibrium speciation model was used to compute the equilibrium between the various species in the cation-calcite environment. Complimentary desorption studies and surface SEM/EDS analysis indicate that the removal of Cd and Zn from solution by calcite and calcium oxalate is probably due to precipitation/complexation reaction. The SEM and EDS results appear to confirm the presence of a precipitate on the mineral surface in the case of the influent solution containing Zn. The current research also examines the effect of citrate, a commonly present urinary tract species on calcium oxalate dissolution. The dissolution studies indicate that citrate solution is capable of dissolving sodium oxalate at high pH. The dissolution of calcium oxalate results in the release of heavy metals that were previously sequestered within the mineral. Results show that a greater percentage of zinc was removed than cadmium, from calcium oxalate due to its dissolution by citrate. / Engineering

Steroid hormones confer biological activity to effluents of wastewater treatment plants (WWTPs). The occurrence of estrogen and androgen hormones in addition to their biological effects in the environment have been widely studied and there is a growing consensus that mixtures of steroid hormones; albeit at low ng L-1concentrations, lead to endocrine disruption in some aquatic organisms. These mixtures may also be influenced by the contributions of synthetic estrogens and androgens, which may display either additive or antagonistic activity. In order to measure the ability of a single compound, or complex mixture to influence the function of estrogenic or androgenic signaling pathways bioassays are used. Most commonly, these tests are in vitro and may quantify the ability of a compound to bind and/or (in) activate the steroid receptors. Two commonly used bioassays for estrogenicity detection are the Yeast Estrogen Screen (YES) and the E-Screen assay. The Yeast Androgen Screen (YAS) is commonly used to measure androgenic activity. The yeast (Saccharomyces cerevisiae) are genetically transformed and express either the human Estrogen Receptor (ER) or Androgen Receptor (AR), and contain Estrogen or Androgen Responsive Elements (ERE/ARE) and Lac Z reporting plasmids. Once the receptors become activated, beta-Galactosidase is secreted into the assay medium and the level of beta-Galactosidase secretion relates to the estrogenicity or androgenicity of the sample tested. Due to its simplicity and the moderately fast assay time, the YES and YAS are commonly used assays in the analysis of complex mixtures to identify the major contributors to both estrogenic and (anti)-androgenic activity in environmental water. The effect directed approach combines both chemical methods and bioassays in a chemical fractionation scheme that is directed by the bioassays. In order to confirm the identity of the key contributors, it is important to compare the biological activities that are calculated from the concentrations of the identified hormones (given their individual biological responses) and the total biological activity measured through the use of bioassays, Equation 1. RPsCs+ RP2C2+ ...+RPnCn = IEQ (1) where Cn is the concentration of the nth mixture constituent, RP is the relative (estrogenic or androgenic) potential of the nth mixture constituent as determined in the bioassay, and IEQ is the estimated total induction equivalent concentration of the mixture by chemical methods. Cs and RPs represents the concentration and relative potential of a standard compound respectively. Agreement between the chemically and biologically derived IEQs means that the major contributors to the biological effect have been successfully identified. However, the biological assays measure the contribution of additive, antagonistic and synergistic activity in the mixture; therefore, the biologically derived IEQs represent the net biological activity. Chemical methods are unable to predict these interactions and as such the result of the concentration addition (CA) approach (Equation 1) is often inconclusive and suggestive of interacting components. An interaction model that can estimate the net biological activity of a mixture from the concentrations of individual mixture constituents (chemical methods) is thus necessary. An interaction model that combines both the relative potential (RP) as well as the interaction index (γ) in a parameter called aRP was developed. The aRP is defined by Equation 2 and is used similarly to the CA approach, Equation 3. aRP = interaction index-1RP (2) aRPsCs+ aRP2C2+ ...+aRPnCn = IEQ (3) The aRP can be calculated for any nth mixture constituent by measuring the degree to which the mixture components altered the activity of the standard and assessing those changes as a function of mixture ratios. The interaction method was validated using a mixture of testosterone, with two anti- androgens, di-n-butyl phthalate, and bisphenol A in the YAS. Mixtures of 17ß;-estradiol, estriol, 17α-dihydroequilin and di-n-butyl phthalate were evaluated in the YES assay. Using Equation 3 the net estrogenic and androgenic activity of the mixtures was estimated. There was a significant improvement over the CA based approach in Equation 1. Overall, in 24 out of 32 mixtures tested there was no significant difference between the aRP and observed responses. Large percent errors were observed in the CA model, particularly when the proportion of antagonists was high as the CA model tended to over-predict the responses. On the contrary, only two aRP model predictions exceeded 50% error. Risk assessors should use the CA model with caution as it could over-predict biological responses and an alternative approach such as the aRP model could be used. In this regard, a database of aRP values for identified antagonistic/synergistic compounds could be assembled and estimations of biological activity could be made using these aRP values. The aRP interaction model could also be used to provide fundamental understanding to the behavior of the constituents in a complex mixture. Although the interaction model presented may account for possible deviations from additivity in environmental mixtures, predictions of mixture effects may be complicated by matrix interferences. In this regard, a sensitive bioassay; such as the E-Screen, which is capable of detecting concentrations as low as 0.27 ng L-1 of 17β-estradiol equivalents is beneficial. However, one major drawback to the E-Screen assay is the 6-day analysis time. In order to maintain the sensitivity of the assay and reduce the analysis time, Fourier Transform Infra-red Imaging Spectroscopy (FT-IRIS) was used to probe the bio-molecular level events that occur in single cells prior to a detectable response in cellular proliferation. The investigation revealed that changes occur on the sub-cellular level at 48-hours after incubation which are comparable to the 6 day E-Screen responses (Pearson R = 0.978). The FT-IRIS response appears to be due to the increase in mucins which are known to play a role in cellular signaling and proliferation. The EC50 values for the E-screen and FT-IRIS assay were 2.29 and 2.56 ppt respectively, indicating that the molecular changes, which are observed at the single cell level using FT-IRIS, are reflective of physiological changes that are observed as the cell population responds to 17ß-estradiol. The study indicates that sophisticated imaging and microscopy techniques such as FT-IRIS may play a role in environmental bio-analytical methods. / Civil Engineering

The emerging contaminants (ECs) such as estrogen hormones, perfluorinated compounds (PFCs), bisphenol A (BPA) and 1, 4-dioxane have been detected in natural water bodies at a noticeable level worldwide. The presence of ECs in the aquatic environment can pose potential threats to aquatic organisms as well as human world. Ion-exchange is a highly efficient technology for the removal of heavy metal ions and natural organic materials (NOMs) due to the nature of exchanging similar charged ions. However, this technology has not been explored for removing ECs. In this study, four categories of ECs: estrogen hormones (12), perfluorinated compounds (10), bisphenol A and 1, 4-dioxane were used as model contaminants. The adsorption of each category of ECs onto various types of polymeric resins (MN100, MN200, A530E, A532E and C115) was investigated. The removal of ECs was tested under batch and column mode. The effects of pH, resin dosage, and contact time on the removal of ECs were studied in batch mode; isotherm and kinetics models were applied to fit the experimental data. Column experiments were conducted to verify the practicability of the polymeric resins. Adsorption results have shown that both MN100 and MN200 resins could efficiently remove estrogen hormones mixture (more than 95%), and bisphenol A (more than 80%) with the initial concentration of 100 ìg/L; A532E and A530E could remove perfuorinated compounds mixture (more than 99%) with the initial concentration of 100 ìg/L. As pH increased from 9 to 11, the adsorption capacity onto polymeric resins decreased dramatically for estrogen hormones such as 17á-ethinylestradiol, estriol, 17â-estradiol, 17á-estradiol, estrone, 17á-dihydroequilin and equilin as well as bisphenol A. The adsorption of estrogen hormones and bisphenol A onto MN100 and MN200 resins reached the equilibrium within 24 hours, whereas the adsorption of perfluorinated compounds onto A532E and A530E reached the equilibrium within 8 hours. It was also observed that the adsorption of PFCs largely depends on the C-C chain length. PFCs with longer chain yielded lower adsorption efficiency onto the ion-exchange resins A532E and A530E. Adding salinity decreased the first-order rate constants for the adsorption of bisphenol A onto MN100 and MN200 resins. Fixed-bed column experiment results with estrogen hormones mixtures confirmed that the polymeric resins were good candidates in the removal of estrogen hormones. Trimegestone was the first compound detected in the effluent in the column test while 17â-estradiol, 17á-estradiol were the last. 80% of the exhausted resins (MN100 and MN200) by bisphenol A were regenerated by using pure methanol as regeneration solution. Polymeric resins were not effectively removing 1, 4-dioxane from the aqueous solution. / Civil Engineering

The presence of emerging contaminants (ECs) in water and wastewater systems has become a subject of significant concern worldwide. These emerging contaminants are complex organic molecules which potentially affect human health and environment. Conventional wastewater treatment plants are unable to completely remove these contaminants from water and therefore can discharge them into environment. The need to develop effective methods for ECs removal is essential. This study assess the potential of ozone based advanced oxidation processes (AOP) to oxidize number of emerging contaminants. Different combinations of ozone with hydrogen peroxide and sodium persulfate were tested. For this study 1-4, dioxane, perfluorinated compounds (PFCs), N,N-Diethyl-metatoluamide, and three pharmaceuticals sulfamethoxazole, trimethoprim and carbamazepine have been selected. The effect of different process parameters such as chemical dosages, ozone weight percent, ozone flow rates, etc. on destruction of ECs were examined. It was observed that 1, 4-dioxane were persistent to direct ozone reaction, however were easily oxidized by hydroxyl radical. However, ozonation was solely very effective (> 99 %) in removing pharmaceuticals such as sulfamethoxaole, trimethoprim and carbamazepine. It was not very efficient for the removal of perfluorinated compound and N,N-Diethylmeta-toluamide. The operational conditions were optimized for maximum removal of every compound and their influence on the degradation process is discussed. / Civil Engineering