•Toxicity test results are influenced by exposure media preparation conditions.•Oil water mixtures were prepared at different conditions and fully characterized.•Droplet formation was governed by oil type, mixing energy and oil loading.•Droplets play a critical role in the stability and composition of the mixtures.•High energy preparations were highly dynamic and require further standardization.Comprehensive characterization of exposure media used in toxicology studies is still an area of significant divergence when evaluating potential oil spill impacts. When preparing exposure media used for toxicology testing, small variations in simple parameters such as mixing energy, oil type and loading can significantly affect the concentration of the oil components to which test organisms are exposed. The key goal of this study was compare and contrast the physical and chemical compositions of oil water mixtures prepared using fresh and weathered Macondo-related oils under different conditions of mixing and in the presence/absence of chemical dispersants. All samples were assessed for the presence of droplets, droplet size distribution, and detailed chemical composition including polycyclic aromatic hydrocarbons (PAHs) and total petroleum hydrocarbon by fluorescence (TPHF). Preparations were also tested for stability over a 96 h period relevant to acute toxicity tests. The results indicate that water accommodated fractions (WAFs) produced consistent, droplet free solutions with concentration that represented the soluble components of the oil used. As expected, chemically-enhanced WAFs (CEWAFs) and high-energy WAFs (HEWAFs) generated large amounts of micron-size droplets and their chemical composition corresponded closely with that of the whole oil. However, the HEWAFs were highly dynamic, and unlike CEWAFs, much of the oil resurfaced within few hours of the initial preparation. Viscosity and lack of dispersability are the limiting factors for preparation of CEWAFs with weathered oils, in contrast HEWAFs did effectively introduce large amounts of weathered oil droplets in the test media. Despite this benefit, droplet sizes significantly decreased in HEWAFs with increase in weathering of the oil creating an additional variable to consider. Because the contribution of small droplets to toxicity is a topic that needs further investigation, the interpretation of results from high-energy preparations needs to be further evaluated. When the TPAHs concentrations of all preparations at all loadings were compared with the publicly available water-column data for samples analyzed during and after the DWH incident response they all ranked above the vast majority of the 10,828 samples reported. Until a better characterization of all the available DWH water column individual-component chemistry data is produced the question of environmental relevance and the pursuit of toxicological studies under more realistic conditions continues to be a significant challenge that should be further explored.Download high-res image (419KB)Download full-size image

Over the past 30 years, endosulfan, one of the last polychlorinated pesticides still in use, has received considerable attention and has been the subject of a number of international regulations and restriction action plans worldwide. This study aimed to monitor the presence and to assess the potential transport of endosulfan within the protected areas of Everglades National Park, Biscayne National Park, and Big Cypress National Preserve, South Florida, USA. Endosulfan sulfate was the major metabolite detected in all matrices in areas along the C-111 and C-111E canals, which drain the Homestead agricultural area and discharge to either Florida or Biscayne Bays, both of which are critical wildlife habitats. Endosulfan concentrations of up to 158 ng L–1 and 57 ng g–1 were observed in surface water and sediments, respectively, which exceeded the U.S. EPA’s chronic water quality criteria (56 ng L–1). Elevated levels of up to 371 ng g–1 of endosulfan sulfate were detected in whole fish tissue.

An online SPE-HPLC-HESI-MS/MS method and an online SPE-HPLC-APPI-MS/MS method were developed to analyze 72 microconstituents in reclaimed water. In this study, 55 reclaimed water samples were collected from the sprinkler system for a year-long period at Florida International University Biscayne Bay Campus, where reclaimed water was reused for daily irrigation. Analysis results showed that several analytes were continuously detected in all reclaimed water samples and others will show rather transient signal increases. Coprostanol, bisphenol A, and DEET’s maximum concentration exceeded 10,000 ng/L. The four most frequently detected compounds were diphenhydramine (100 %), DEET (98 %), atenolol (98 %) and carbamazepine (96 %).

An online solid-phase extraction and liquid chromatography in combination with tandem mass spectrometry method was developed for the simultaneous determination of 31 antibiotics in drinking water, surface water and reclaimed waters. The developed methodology requires small sample volume (10 mL), very little sample preparation and total sample run time was 20 min. An Ion Max API heated electrospray ionization source operated in the positive mode with two selected reaction monitoring transitions was used per antibiotic for positive identity and quantification performed by the internal standard approach, to correct for matrix effects and any losses in the online extraction step. Method detection limits were in the range of 1.2–9.7, 2.2–15, 5.5–63 ng/L in drinking water, surface water and reclaimed waters, respectively. The method accuracy in matrix spiked samples ranged from 50–150 % for the studied antibiotics. The applicability of the method was demonstrated using various environmental and reclaimed water matrices. Erythromycin was detected in more than 85 % of the samples in all matrices (28–414, n.d.–199, n.d.–66 ng/L in reclaimed, river and drinking waters respectively). The other frequently detected antibiotics in reclaimed waters were nalidixic acid, clarithromycin, azithromycin, trimethoprim, and sulfamethoxazole.

A comprehensive environmental evaluation was completed on 20 metals: two reference metals (Fe, Al) and several minor trace metals (As, Ba, Co, Cr, Cu, Mn, Ni, Pb, V, and Zn) for surface soils and sediments collected from 50 sites in Everglades National Park (ENP), the coastal fringes of Biscayne National Park (BNP), and Big Cypress National Preserve. Samples were prepared by acid digestion (EPA3050) and analyzed by ICP/MS detection (EPA6020). Although no widespread contamination was detected across the two parks and one preserve, there were some specific areas where metal concentrations exceeded Florida’s ecological thresholds, suggesting that some metals were of concern. A screening-level evaluation based on a proposed effect index grouped trace metals by their potential for causing negligible, possible, and probable effects on the biota. For example, Cu in BNP and Cr and Pb in ENP were considered of concern because their adverse effect likelihood to biota was assessed as probable; consequently, these trace metals were selected for further risk characterization. Also, stations were ranked based on a proposed overall contamination index that showed that: site BB10 in BNP and sites E3 and E5 in ENP had the highest scores. The first site was located in a marina in BNP, and the other two sites were along the eastern boundary of ENP adjacent to current or former agricultural lands. An assessment tool for south Florida protected lands was developed for evaluating impacts from on-going Everglades restoration projects and to assist State and Federal agencies with resource management. The tool consists of enrichment plots and statistically derived background concentrations based on soil/sediment data collected from the two national parks and one preserve. Finally, an equally accurate but much simplified approach is offered for developing enrichment plots for other environmental settings.

A simple, rapid and sensitive method was developed for the routine analysis of trace elements on sediments and soils by UV-ns-LA-ICP-MS. The homogenization procedure that reduces the particle size of the samples to less than 1 µm diameter was found to be a key factor to allow for a representative sampling of the bulk soil at the micro-scale and to improve reproducibility and cohesion of the sample without requiring the use of any binder. The elimination of binders simplified the sample preparation and avoided any undesirable dilution of the sample. SEM/EDX analyses were conducted to evaluate the efficiency of laser to sample interaction. Matrix effects and different quantitation strategies were employed to demonstrate the utility of the analytical technique. Sixteen elements were analyzed on soil and sediment samples and certified reference materials. Analytical results obtained by LA-ICP-MS were comparable to solution ICP-MS analysis in terms of accuracy, precision and limits of detection. Two independent proficiency tests for trace metals in soils were conducted to compare the performance of the method versus conventional digestion ICP and AA methods, obtaining z scores ≤ 3 for all elements measured by LA-ICP-MS. An overall bias between 8 and 15% was found, depending on the sample while the overall precision was found to be better than 5% RSD for all samples. Limits of detection were as low as 0.01 mg kg− 1.

The halonitromethanes (HNMs) are byproducts of the ozonation and chlorine/chloramine treatment of drinking waters. Although typically occurring at low concentrations HNMs have high cytotoxicity and mutagenicity, and may therefore represent a significant human health hazard. In this study, we have investigated the radical based mineralization of fully-halogenated HNMs in water using the congeners bromodichloronitromethane and chlorodibromonitromethane. We have combined absolute reaction rate constants for their reactions with the hydroxyl radical and the hydrated electron as measured by electron pulse radiolysis and analytical measurements of stable product concentrations obtained by 60Co steady-state radiolysis with a kinetic computer model that includes water radiolysis reactions and halide/nitrogen oxide radical chemistry to fully elucidate the reaction pathways of these HNMs. These results are compared to our previous similar study of the fully chlorinated HNM chloropicrin. The full optimized computer model, suitable for predicting the behavior of this class of compounds in irradiated drinking water, is provided.Highlights► Radical-based mineralization of aqueous halonitromethane disinfection byproducts. ► Constructed kinetic computer model for tri-halogenated halonitromethane removal. ► Model predicted that superoxide reaction is unimportant for halonitromethanes. ► Measured superoxide reaction with chloropicrin was negligibly slow, <2×104 M−1 s−1. ► Determined that superoxide reaction with nitrate also insignificant at ∼104 M−1 s−1.

•A total of 54 phase I and II metabolites of illicits were reported.•Data dependent scan and targeted MS2 were explored for confirmation of metabolites.•%mol fraction of each identified metabolite was reported.A QExactive Orbitrap was used for the identification of phase I and II transformation products (TPs) of illicit drugs in raw sewage influents. Two operating modes (targeted MS2 and Data-dependent screening) were used for data acquisition. Even though, data-dependent scan is a faster route towards the potential identification of metabolites, it suffered from its limitation to provide enough data points across the chromatographic peak during the MS2 cycle in contrast to targeted MS2. Therefore, the later technique was implemented as the method of choice in this study for the positive confirmation and quantitation of TPs (n = 54). The vast majority of the identified TPs were products of phase I transformation reactions, with the latter being more prevalent in the nature. Estimated mole fractions showed that for a large number of the analytes, TPs must also be monitored in order to fully understand their environmental fate and calculate potential consumption.