An enhancement approach of fluorescence signatures in excitation emission matrixes for water contaminant analysis

Authors

Yingtian Hu, Dongdong Zhao, Yali Qin, Xiaoping Wang

Three-dimensional fluorescence spectroscopy has been widely used for the analysis of water contaminants. However, the problems of weak signals and overlapping fluorescence peaks remain unresolved. In this work, we studied the impact of absorption on the spectral shape of fluorescence and found that it is a major cause of overlapping peaks and weak signals. An approach is proposed to purify fluorescent signals and enhance fluorescence signatures based on the theory of fluorescence quantum yield. Using this theory, the problems of noise amplification and singularity points were identified, and an optimization algorithm was proposed related to Wiener filtering. For practical application to multiple compounds, three overlapping cases were discussed theoretically. The effectiveness of this procedure in subsequent parallel factor analysis was assessed and compared with original data by conducting experiments with six typical compounds and real water samples. The results indicate that overlapping along the excitation wavelength axis can be reduced despite the existence of multiple compounds, and the sensitivity of weak fluorescent signals can be significantly improved. The proposed method can enhance fluorescence signatures for the separation and analysis of fluorescent components in water contaminants.

Toxicity of single steroid hormones and their mixtures toward the cyanobacterium Microcystis aeruginosa

Authors

Karolina Czarny, Dominik Szczukocki, Barbara Krawczyk, Renata Gadzała-Kopciuch, Sławomira Skrzypek

Several compounds, such as hormones, are released uncontrolled into the aquatic environment, and some of these pollutants have an adverse effect on endocrine systems of humans and other organisms. However, there is insufficient information about the effect of natural and synthetic hormones on non-target organisms, such as cyanobacteria. Therefore, in this study, the adverse effects of hormones, singly and in combination, on Microcystis aeruginosa were explored for the first time. Chronic toxicity was evaluated based on biomass and chlorophyll ameasurements during 14 days of exposure. Growth of cyanobacteria after exposure to 0.1–100 mg L⁻¹ of hormones was inhibited in a concentration-dependent manner. In most cases, a low concentration of hormones (0.1–1 mg L⁻¹) did not affect the growth of cyanobacteria, but a higher concentration (> 10 mg L⁻¹) inhibited the growth. The obtained 14-day EC₅₀ values were 88.92–355.15 mg L⁻¹. According to these values, the decreasing order of the toxicity of the eight hormones to tested cyanobacteria was 17-α-ethinylestradiol > progesterone > 17ß-estradiol > 5-pregnen-3β-ol-20-one > testosterone> estrone > levonorgestrel > estriol. Moreover, data show that mixed hormones were more toxic than single compounds and more than additive effect was observed. The achieved 14-day EC₅₀ values for mixed hormones were 56.66–166.83 mg L⁻¹. Simultaneous presence of several hormones in the aquatic environment may lead to increased toxicity (more than additive effect) and cause serious ecological effects, more harmful than expected.

Estimating the eco-toxicological risk of estrogens in China’s rivers using a high-resolution contaminant fate model

Authors

Günther Grill, Jing Li, Usman Khan, Yan Zhong, Bernhard Lehner, Jim Nicell, Joseph Ariwi

The contamination of freshwater systems arises in many river basins due to industrialization and population growth, posing risks to ecosystems and human health. Despite these concerns, the fate and potential impact of many emerging pollutants are currently unknown, especially when the compounds are released into surface waters from populations distributed across large spatial scales. In order to address this shortcoming, a spatially-explicit contaminant fate model was developed as an extension of the global, vector-based river routing model HydroROUT. HydroROUT operates at very high spatial resolution (∼500 m), simulates river and stream chemical transport with in-stream removal, and contains links to a set of lakes and reservoirs, which act as a partial sink during the transport. The chemical fate model was applied to China and includes a consumption and release module based on county-level population demographics, considers point-source contributions from 2547 wastewater treatment plants, and accumulates contributions of rural and urban populations not connected to sewage treatment plants. As a case study, the sources and fates of the estrogens estrone (E1), 17β-estradiol (E2), estriol (E3), as well as the synthetic estrogenic steroid hormone 17α-ethinylestradiol (EE2) were modelled in Chinese surface water bodies. Preliminary validation of the results showed predictions to be within the ranges of concentrations reported in literature, with exception of EE2. The total estrogenic mass in the entire river and lake system amounted to 370 tonnes of estrogens, with about 1.3 tonnes per year discharged to the ocean, neighboring countries or to inland sinks. Under a selected baseline scenario, eco-toxicological risk—i.e., contaminant concentrations in excess of the predicted no effect concentration (PNEC)—is found in 23.6% of all analyzed rivers of China with an average flow > 0.1 m3/s. Out of these, about 4% of rivers showed a high level of risk of 10 times or more above PNEC. Medium-to-large rivers are disproportionally affected; for example, 23.6%, 37.3%, 29.0% and 21.6% of river length are at risk in rivers of 1–10, 10–100, 100–1,000, and 1,000–10,000 m3/s of discharge, respectively, whereas no risk was predicted in the largest rivers (i.e., >10,000 m3/s) of China. Wastewater treatment plants process 22.5% of the total hormone load and thus play an important role in water quality control by reducing the risk in substantial portions of the river network, which would otherwise show elevated risk. Releases from untreated population dominate by far the overall contribution to risk.

Diversity of potential antibiotic-resistant bacterial pathogens and the effect of suspended particles on the spread of antibiotic resistance in urban recreational water

Authors

Tingting Fang, Hui Wang, Qijia Cui, Matt Rogers, Peiyan Dong

Evidence of the increasing incidence of antibiotic resistance in watersheds has attracted worldwide attention. Limited in formation is available on the occurrences of health-related antibiotic-resistant bacterial pathogens (ARBPs) in recreational waters. The effects of certain environmental factors (e.g., suspended particles) on the spread of resistance also has not been characterized to date. In this study, a combination of culture and molecular methods was employed to comprehensively investigate the patterns of microbial resistance to representative antibiotics in samples from three recreational lakes in Beijing. The antibiotic resistance index (ARI) based on the gradient concentration assay revealed that samples showed high resistance to penicillin-G, moderate resistance to ampicillin, vancomycin and erythromycin and low resistance to ceftriaxone, gentamycin, tetracycline and chloramphenicol. Antibiotic-resistant bacteria (ARB) were cultured and collected, and the diversity of potential ARBP species was further explored using next-generation sequencing (NGS). The results showed that most of the identified ARBPs were environmental opportunistic pathogens with emerging clinical concerns, e.g., the multidrug-resistant Acinetobacter junii. Furthermore, particle-attached (PA) fractions presented higher ARI values than free-floating (FL) fractions did, indicating that the PA fractions were more resistant to selected antibiotics. And the NGS results revealed that the PA fractions showed higher similarity in the screened ARB community compositions in comparison with the FL fractions, primarily due to a protective effect provided by the particles. Accordingly, ARBPs could persist for a longer time in protective particle matrices. However, quantification of antibiotic-resistant genes (ARGs) by qPCR showed no significant abundance differences between the two fractions. Overall, these findings suggest a potential health risk from the prevalence of ARBPs in recreational waters and provides a better understanding of the contribution of particles in the spread of antibiotic resistance in aquatic systems, with implications for the control of excessive suspended particles by water management.

Microplastics in freshwater river sediments in Shanghai, China: A case study of risk assessment in mega-cities

Authors

Guyu Peng, Pei Xu, Bangshang Zhu, Mengyu Bai, Daoji Li

Microplastics, which are plastic debris with a particle diameter of less than 5 mm, have attracted growing attention in recent years. Its widespread distributions in a variety of habitats have urged scientists to understand deeper regarding their potential impact on the marine living resources. Most studies on microplastics hitherto are focused on the marine environment, and research on risk assessment methodology is still limited. To understand the distribution of microplastics in urban rivers, this study investigated river sediments in Shanghai, the largest urban area in China. Seven sites were sampled to ensure maximum coverage of the city’s central districts, and a tidal flat was also included to compare with river samples. Density separation, microscopic inspection and μ-FT-IR analysis were conducted to analyze the characteristics of microplastics and the type of polymers. The average abundance of microplastics in six river sediment samples was 802 items per kilogram of dry weight. The abundance in rivers was one to two orders of magnitude higher than in the tidal flat. White microplastic spheres were most commonly distributed in river sediments. Seven types of microplastics were identified, of which polypropylene was the most prevailing polymers presented. The study then conducted risk assessment of microplastics in sediments based on the observed results, and proposed a framework of environmental risk assessment. After reviewing waste disposal related legislation and regulations in China, this study conclude that in situ data and legitimate estimations should be incorporated as part of the practice when developing environmental policies aiming to tackle microplastic pollution.

Secondary microplastics were prevalent in sediment in a freshwater UK urban river

Authors

Reina Blair, Susan Waldron, Vernon Phoenix, Caroline Gauchotte-Lindsay

Plastic pollution has been documented in terrestrial and aquatic environments worldwide, with growing concern for ‘microplastics’ (MPs, <5 mm). Understanding of the sources, fate, and impact of MPs remains limited, particularly in freshwater environments. Furthermore, their small sizes and a lack of standardised methodology hinders monitoring and risk assessment of these emerging contaminants. Here, the distribution of microscopic debris in an urban river close to the marine environment in the West of Scotland was investigated to assess the prevalence of MPs. Bank sediment samples were collected twice from the River Kelvin in Glasgow and were size-fractionated and processed for extraction of MPs by density separation. Light microscopy and scanning electron microscopy with energy dispersive spectroscopy, were employed for characterisation and quantification of microdebris of sizes ranging from 2.8 mm to 0.45 µm. Sample MP spiking and use of procedural blanks allowed the influence of processing on field data quality to be considered. The predominant type of MPs were fibres, comprising >88% of total MP counts, but fibre content in blanks suggested potential contributions from background contamination. Final MP abundances were estimated at 161-432 items per kg dry sediment. In addition, metallic and glass pellets were observed in high abundances in settled material and could be easily misidentified by visual inspection. Thus, compositional analysis is needed to avoid analytical errors from MP misidentification and overestimation.

Occurrence, Fate, and Effect of Microplastics in Freshwater Systems

Authors

Dafne Eerkes-Medrano, Richard Thompson

Concern about the presence of small plastic particles in marine environments was first noted in the late 20th century. Microscopic sized particles “microplastics” became a topic of active discussion in the early 21st century and had exponential growth in scientific publications in the last decade. In freshwater environments, investigation into microplastics only gained momentum after studies in 2011 and 2012. Microplastics are now documented in natural (e.g., lakes, rivers, and estuaries) and man-made freshwater bodies worldwide and within organisms that inhabit or interact with these environments.

This chapter guides the reader through relevant aspects of the topic of microplastic in freshwaters. This chapter presents and discusses the sources and types of microplastics occurring in freshwater systems and their distributions in global freshwater habitats. The conditions influencing the quantity of microplastics in the environment, factors affecting dispersal, and aspects of detection and quantification of microplastics are also discussed. Information is provided on interactions between biota and microplastics and on the potential impacts of microplastics on biota and humans. Examples from the marine literature are drawn where limited information on freshwaters exist. The chapter closes with considerations for future work.

A comparison of equilibrium and kinetic passive sampling for the monitoring of aquatic organic contaminants in German rivers

Authors

Yoonah Jeong, Andreas Schäffer, Kilian Smith

The performances of an equilibrium and a kinetic passive sampler for monitoring a range of organic contaminants (Log K_OW from −0.03 to 6.26) were evaluated in the effluent of a wastewater treatment plant, the receiving river Saar as well as the river Mosel in Germany. The polar organic chemical integrative sampler (POCIS) and a new mixed polymer sampler (MPS) were selected as kinetic and equilibrium passive samplers, respectively. Concentrations were described in terms of a time-weighted average concentration (C_TWA) from the POCIS measurements and as an equilibrium concentration from the MPS (C_Equil-MPS) and POCIS membrane (C_Equil-PES) analyses. Twenty-seven compounds could be detected, including eight priority substances of the EU Water Framework Directive. Both sampler types detected a similar range of compounds in the low ng/L to μg/L range, with a high proportion of pharmaceuticals being detected at all sampling sites. To account for uncertainty in the POCIS sampling rates, a range in C_TWA was estimated by applying low and high sampling rates. For the compounds that were detected in the POCIS this range was within a factor of 3.5. Interestingly, the MPS extracts showed lower ionisation artefacts than the POCIS extracts during the LC-MS/MS analysis. Finally, total water concentrations (C_Total) were estimated from the dissolved concentrations, literature organic carbon partition coefficients (K_OC) and the total organic carbon levels measured in the rivers. For the compounds in this study, negligible differences between C_Total and the passive sampler-derived dissolved concentrations were found with a maximum difference of 15% for diclofenac. Overall, this study demonstrated that the parallel application of kinetic and equilibrium passive samplers can improve the description of water quality.

Spatial and Seasonal Distributions of Current Use Pesticides (CUPs) in the Atmospheric Particulate Phase in the Great Lakes Region

Authors

Shaorui Wang, Amina Salamova, Ronald A. Hites , and Marta Venier

This study examined spatial and seasonal variations of current use pesticdes (CUPs) CUPs levels in the atmospheric particulate phase in the Great Lakes basin. Twenty-four hour air samples were collected at six sites (two urban, two rural, and two remote) in 2015. The concentrations of 15 CUPs, including nine pyrethroid insecticides, four herbicides, one organophosphate insecticide, and one fungicide, were measured. The total CUPs concentrations were higher at the urban sites (0.38–1760 pg/m³) than at the rural and remote sites (0.07–530 pg/m³). The most abundant CUPs were pyrethroid insecticides at the urban sites. The levels of the other CUPs did not vary much among the six sites, except at the most remote site at Eagle Harbor, where the levels were significantly lower. Chlorothalonil was the most frequently detected CUPs, which was detected in more than 76% of the samples. The atmospheric concentrations of total pyrethroid insecticides and total herbicides were correlated with local human population and developed land use. Significantly higher concentrations of most CUPs were observed in the warmer months than in the colder months at all sites. In addition to agricultural applications, which occur during the warmer months, the CUPs atmospheric concentrations may also be influenced by nonagricultural activities and the urban development.

Glyphosate dose modulates the uptake of inorganic phosphate by freshwater cyanobacteria

Authors

Damian Drzyzga, Jacek Lipok

The usefulness of glyphosate [N-(phosphonomethyl)glycine] as a source of nutritive phosphorus for species of halophilic cyanobacteria has been postulated for years. Our results indicate a stimulating effect of glyphosate on the growth of four out of five examined freshwater species, Anabaena variabilis (CCALA 007), Chroococcus minutus (CCALA 055), Fischerella cf. maior (CCALA 067) and Nostoc cf. muscorum (CCALA 129), in a manner dependent on the applied concentration. The most significant stimulation was observed at a dose of 0.1 mM glyphosate. The decrease in the amount of phosphonate, which correlated with microbial growth, demonstrated that glyphosate may play an important role in cyanobacterial nourishment. Surprisingly, the consumption of organic phosphorus did not start when concentrations of inorganic phosphate (PO₄ ³⁻) had fallen dramatically; instead, the assimilation of both types of phosphorus occurred simultaneously. The greatest decrease in the amount of glyphosate was observed during the first week. The uptake of the standard nutrient-phosphate (PO₄ ³⁻), was strongly dependent on the xenobiotic concentration. When a concentration of 0.1 mM glyphosate was used, the consumption of phosphate decreased in favour of glyphosate assimilation. Our study revealed for the very first time that the presence of inorganic phosphate significantly enhances the bioavailability of glyphosate. Statistical analysis confirmed that the nutritive usage of glyphosate and the absorption of phosphate are features associated with the herbicide concentration rather than features related to the species of freshwater cyanobacterium. This finding supports the thesis of an important role of organic phosphorus in the formation of cyanobacterial blooms and creates the opportunity of using these cyanobacteria to bind both organic and inorganic forms of phosphorus in microalgal biomasses.