Differential Organic Contaminant Ionization Source Detection and Identification in Environmental Waters by Nontargeted Analysis

Unraveling the chemical fingerprint of the Miami River sources: Insights from high-resolution mass spectrometry and nontarget analysis

This study investigated the chemical composition of waters in the heavily urbanized and historically polluted Miami River, Florida. The goal was to assess the different water sources and anthropogenic influence in this managed area using nontarget analysis (NTA) combined with high-resolution mass spectrometry (HRMS). Surface water samples were collected from 10 sites during five sampling events in the wet season of 2021 and 2022. The HRMS data was processed using Compound Discoverer™ version 3.3, and the results were analyzed using techniques including Principal Component Analysis and Kendrick Mass Defect plots. Results showed a gradient change in the chemical composition from the Everglades to Biscayne Bay endmembers. The Seybold Canal, an adjacent canal, was consistently identified as a unique source of contaminants, contributing its own specific set of tracers. Increased presence and intensity of organic contaminants along the waterway was observed, indicating significant anthropogenic influence in the area. The NTA and post-processing were evaluated for reproducibility, demonstrating robustness with a 71.2% average reproducibility for compounds detected in 3 out of 5 sampling trips. A detection frequency of 80% (4 out of 5) was the set criterion for detected compounds suggested as tracers. To prioritize samples, hierarchical cluster analysis was employed, and potential tracers for each water source were determined. Tracers included natural products and agricultural herbicides and insecticides for the Everglades, anthropogenic contaminants for the Seybold Canal, and a lack of unique tracers for Biscayne Bay. Additionally, urban-influenced contaminants such as flame retardants, insect repellents, pharmaceuticals, and non-agricultural herbicides were identified along the river. This study highlights the impact of human activities on the Miami River and demonstrates the effectiveness of NTA in differentiating and tracking water sources. The results emphasize the importance of reproducibility in NTA and provide guidance on implementing monitoring strategies by prioritizing samples based on chemical compositions.

Dispersion and stratification of Per-and polyfluoroalkyl substances (PFAS) in surface and deep-water profiles: A case study of the Biscayne Bay area

Per-and polyfluoroalkyl substances (PFAS) are a group of synthetic chemical compounds known for their persistent, bioaccumulation and toxic characteristics in all environmental compartments. As industrial and domestic applications of PFAS increase, their discharge into water bodies becomes of human and ecological concerns. Our research focuses on providing better understanding on the occurrence, vertical distribution, and dispersion of PFAS in surface and bottom water from inshore and offshore area of Biscayne Bay, Miami, Florida. We screened a total of 30 PFAS from inshore (N = 38) and offshore (N = 48) water samples using a semi-automated solid phase extraction (SPE) followed by instrumental analysis using Liquid chromatography-mass spectrometry techniques (LC-MS/MS). Our findings show a general surface-enrichment and depth-depletion pattern from inshore to offshore area. Average ∑PFAS loadings inshore (surface vs bottom; 29.52 ± 15.26 ng/L vs 21.45 ± 7.85 ng/L) is significantly greater than offshore (surface vs bottom; 5.18 ± 2.68 ng/L vs 2.42 ± 2.11 ng/L). PFOS had the highest mean concentration both inshore (6.36 ± 4.23 ng/L) and offshore (0.83 ± 0.87 ng/L). The most frequently detected (D·F > 91 %) PFAS are Perfluorooctane sulfonic acid (PFOS), Perfluorooctanoic acid (PFOA), Perfluoroheptanoic acid (PFHpA), Perfluorohexanoic acid (PFHxA), Perfluorobutanoic acid (PFBA), Perfluorobutane sulfonic acid (PFBS) and Perfluorohexane sulfonic acid (PFHxS) in surface water samples. PFOS/PFOA >1 suggests that point sources are the major contribution to PFAS burden in the Biscayne Bay. An innovative Inverse distance weighted interpolation (IDW) special modelling approach was implemented to predict the potential contribution of oceanic current on the dispersion of ∑PFAS loadings in surface and bottom profiles from canals (inshore) to offshore areas. This will provide insights into transport mechanisms of PFAS from source emissions, and risk assessments of potential impacts on human and aquatic life in the Bay.

Non-targeted analysis for the screening and semi-quantitative estimates of per-and polyfluoroalkyl substances in water samples from South Florida environments

Per- and polyfluoroalkyl substances (PFAS) are a group of anthropogenic pollutants that are found ubiquitously in surface and drinking water supplies. Due to their persistent nature, bioaccumulative potential, and significant adverse health effects associated with low concentrations, they pose a concern for human and environmental exposure. With the advances in high-resolution mass spectrometry (HRMS) methods, there has been an increasing number of non-targeted analysis (NTA) approaches that allow for a more comprehensive characterization of total PFAS present in environmental samples. In this study, we have developed and compared NTA workflows based on an online solid phase extraction- liquid chromatography high resolution mass spectrometry (online SPE-LC-HRMS) method followed by data processing using Compound Discoverer and FluoroMatch for the screening of PFAS in drinking waters from populated counties in South Florida, as well as in surface waters from Biscayne Bay, Key west, and Everglades canals. Tap water showed the highest number of PFAS features, indicating a poor removal of these chemicals by water treatment or perhaps the breakdown of PFAS precursors. The high number of PFAS features identified only by CD and FluoroMatch emphasizes the complementary aspects of these data processing methods. A Semi-quantitation method for NTA (qNTA) was proposed using a global calibration curve based on existing native standards and internal standards, in which concentration estimates were determined by a regression-based model and internal standard (IS) response factors. NTA play a crucial role in the identification and prioritization of non-traditionally monitored PFAS, needed for the understanding of the toxicological and environmental impact, which are largely underestimated due to the lack of such information for many PFAS.

Evaluating non-targeted analysis methods for chemical characterization of organic contaminants in different matrices to estimate children's exposure

BACKGROUND

Children are vulnerable to environmental exposure of contaminants due to their small size, lack of judgement skills, as well as their proximity to dust, soil, and other environmental sources. A better understanding about the types of contaminants that children are exposed to or how their bodies retain or process these compounds is needed.

OBJECTIVE

In this study, we have implemented and optimized a methodology based on non-targeted analysis (NTA) to characterize chemicals in dust, soil, urine, and in the diet (food and drinking water) of infant populations.

METHODS

To evaluate potential toxicological concerns associated with chemical exposure, families with children between 6 months and 6 years of age from underrepresented groups were recruited in the greater Miami area. Samples of soil, indoor dust, food, water, and urine were provided by the caregivers, prepared by different techniques (involving online SPE, ASE, USE, QuEChERs), and analyzed by liquid chromatography-high resolution mass spectrometry (LC-HRMS). Data post-processing was performed using the small molecule structure identification software, Compound Discoverer (CD) 3.3, and identified features were plotted using Kendrick mass defect plot and Van Krevelen diagrams to show unique patterns in different samples and regions of anthropogenic compound classifications.

RESULTS

The performance of the NTA workflow was evaluated using quality control standards in terms of accuracy, precision, selectivity, and sensitivity, with an average of 98.2%, 20.3%, 98.4% and 71.1%, respectively. Sample preparation was successfully optimized for soil, dust, water, food, and urine. A total of 30, 78, 103, 20 and 265 annotated features were frequently identified (detection frequency >80%) in the food, dust, soil, water, and urine samples, respectively. Common features detected in each matrix were prioritized and classified, providing insight on children's exposure to organic contaminants of concern and their potential toxicities.

IMPACT STATEMENT

Current methods to assess the ingestion of chemicals by children have limitations and are generally restricted by specific classes of targeted organic contaminants of interest. This study offers an innovative approach using non-targeted analysis for the comprehensive screening of organic contaminants that children are exposed to through dust, soil, and diet (drinking water and food).

Critical assessment of the Kendrick mass defect analysis as an innovative approach to process high resolution mass spectrometry data for environmental applications

The growing application of high resolution mass spectrometry (HRMS) over the last decades has dramatically improved our knowledge about the occurrence of environmental contaminants. However, most of the compounds detected remain unknown and the large volume of data generated requires specific processing approaches. Therefore, this study presents the concepts of mass defect (MD), Kendrick mass (KM) and Kendrick mass defect (KMD) to the expert and non-expert reader along with relevant examples of applications in environmental HRMS data processing. A preliminary bibliometric overview indicates that the potential benefits of KMD analysis are rather overlooked in environmental science. In practice, a simple calculation allows transforming a mass from the IUPAC system (normalized so that the mass of ¹²C is exactly 12) to its corresponding KM normalized on a specific moiety such as CH₂ (the mass of CH₂ is exactly 14). Then, plotting the KMD according to the nominal KM allows revealing groups of compounds that differ only by their number of CH₂ moieties. For instance, data processing using KM and KMD was proven particularly useful to characterize natural organic matter in a sample, to reveal the occurrence of polymers as well as poly/perfluorinated alkylated substances (PFASs), and to search for transformation products (TPs) of a given chemical.

Rubber Antioxidants and Their Transformation Products: Environmental Occurrence and Potential Impact

Antioxidants are prevalently used during rubber production to improve rubber performance, delay aging, and extend service life. However, recent studies have revealed that their transformation products (TPs) could adversely affect environmental organisms and even lead to environmental events, which led to great public concern about environmental occurrence and potential impacts of rubber antioxidants and their TPs. In this review, we first summarize the category and application of rubber antioxidants in the world, and then demonstrate the formation mechanism of their TPs in the environment, emphasizing their influence on the ozone oxidative degradation. The potential toxic effects of antioxidants and their TPs are further reviewed to improve understanding of their biological health impact and environmental risks. Finally, the environmental occurrences of antioxidants and their TPs are summarized and their environmental impacts are demonstrated based on the recent studies. Due to the currently limited understanding on the toxic and biological effects of these compounds, further studies are required in order to better assess various TPs of these antioxidants and their environmental impact. To our knowledge, this is the first review on antioxidants and their TPs in the environment, which may elevate the environmental risk awareness of rubber products and their TPs in the near future.