The behaviour of arsenic (As) from geogenic soil exposed to aerobic conditions is critical to predict the impact of As on the environment, which processes remain unresolved. The current study examined the depth profile of As in geologically derived subsoil cores from Hong Kong and investigated the mobilization, plant availability, and bioaccessibility of As in As-contaminated soil at different depths (0–45.8 m). Results indicated significant heterogeneity, with high levels of As in three layers of soil reaching up to 505 mg/kg at a depth of 5 m, 404 mg/kg at a depth of 15 m, and 1510 mg/kg at a depth of 27–32 m. Arsenic in porewater samples was <11.5 μg/L in the study site. X-ray absorption spectroscopy (XAS) indicated that main As species in soil was arsenate (As(V)), as adsorbed fraction to Fe oxides (41–69% on goethite and 0–8% on ferrihydrite) or the mineral form scorodite (30–57%). Sequential extraction procedure demonstrated that 0.5 ± 0.4% of As was exchangeable. Aerobic incubation experiments exhibited that a very small amount (0.14–0.48 mg/kg) of As was desorbed from the soil because of the stable As(V) complex structure on abundant Fe oxides (mainly goethite), where indigenous microbes partly (59 ± 18%) contributed to the release of As comparing with the sterilized control. Furthermore, no As toxicity in the soil was observed with the growth of ryegrass. The bioaccessibility of As was <27% in the surface soil using simplified bioaccessibility extraction test. Our systematic evaluation indicated that As in the geogenic soil profile from Hong Kong is relatively stable exposing to aerobic environment. Nevertheless, children and workers should avoid incidental contact with excavated soil, because high concentration of As was present in the digestive solution (<0.1–268 μg/L).

Oligomeric organophosphate esters (OOPEs) like 2,2-bis(chloromethyl)-propane-1,3-diyltetrakis (2-chloroethyl) bisphosphate (V6), resorcinol bis(diphenylphosphate) (RDP) and bisphenol A bis(diphenylphosphate) (BDP), are widely used as alternatives of Deca-BDE in plastic and electronic consumer products. However, studies on the environmental occurrence and fate of OOPEs are very scarce. This work studied the occurrence, distribution and fate of V6, BDP and RDP during the different treatment stages of a sewage treatment plant (STP) in Beijing, China. To accomplish this, a method to analyze trace V6, BDP and RDP in suspended solids samples and aqueous samples of sewage and sludge was developed by using liquid chromatography tandem mass spectrometry (LC-MS/MS). Using this method, BDP and RDP were detected for the first time in suspended solids of sewage and sludge with a concentration of 2.06–5.82 ng/g dry weight and 0.44–3.45 ng/g dry weight, respectively, whereas their concentration level in the aqueous phase of these samples were below the detection limits of the method. However, V6 was detected in all treatment stages of the STP, with concentrations in the range of 10.2–27.1 ng/L in aqueous phase and 0.40–1.73 ng/g dw in solid phase. Mass balance results indicated that 75.6% of the original V6 mass flow was discharged along with effluent, while 83.3% and 72.2% of the initial RDP and BDP mass flow were lost due to biodegradation, respectively. Nevertheless, compared to the 14 widely used monomeric organophosphate esters (MOPEs), the concentration levels of OOPEs in this studied STP were relatively low.

Toxic cyanobacterial blooms have been implicated for their negative consequences on many terrestrial and aquatic organisms. Water birds belong to the most common members of the freshwater food chains and are most likely to be affected by the consumption of toxic cyanobacteria as food. However, the contribution of cyanotoxins in bird mortalities is under-studied. The aim of the study was to investigate the likely role of cyanotoxins in a mass mortality event of the Dalmatian pelican (Pelecanus crispus) in the Karla Reservoir, in Greece. Water, scum, tissues and stomach content of dead birds were examined for the presence of microcystins, cylindrospermopsins and saxitoxins by an enzyme-linked immunosorbent assay. High abundances of potential toxic cyanobacterial species and significant concentrations of cyanotoxins were recorded in the reservoir water. All examined tissues and stomach content of the Dalmatian pelicans contained significant concentrations of microcystins and saxitoxins. Cylindrospermopsin concentrations were detected in all tissues except from the brain. Our results suggest that cyanotoxins are a plausible cause for this bird mass mortality episode in the Karla Reservoir.

This study tested the hypothesis that different diets could modulate mercury (Hg) trophic transfer by concurrently altering the transfer of energy (in terms of growth) and transfer of Hg (in terms of biodynamic process). Firstly, we conducted a 40-d laboratory bioaccumulation experiment, in which tilapia (Oreochromis niloticus) was exposed to inorganic mercury (Hg[II]) and methylmercury (MeHg) via feeding on three distinct diets (macrophyte, freshwater shrimp, and commercial pellets) at a fixed ingestion rate of 0.065 g g⁻¹ d⁻¹. During the dietary exposure period, tilapia exhibited Hg species- and diet-dependent Hg trophic transfer patterns and diet-specific growth rates. We then employed a biokinetic model to assess how diet-specific biodynamics and/or diet-specific growth rates modulated the overall Hg bioaccumulation and trophic transfer. The diet-specific assimilation efficiencies (AEs) were monitored using radioisotope technique, and the determined AEs of Hg(II) (8.6%–29.7%) varied by 3.5 times among diets whereas the MeHg AEs (94.4%–97.1%) were not affected. The biokinetic modeling further revealed that Hg(II) trophic transfer in tilapia was controlled by the diet-specific AEs, while MeHg trophic transfer was governed by the diet-specific growth rates. Specifically, a diet-derived high growth rate reduced the MeHg trophic transfer in pellets-fed tilapia, and the overall accumulated MeHg level in fish was under the control of both somatic growth dilution and dietary MeHg influx. Moreover, we observed that the Hg levels (mainly as MeHg) in fast-growing farmed tilapia were significantly lower than wild-living tilapia after 100 d exposure in the field, attributed to somatic growth dilution (SGD). Both the laboratory and field study therefore demonstrated the importance of diet-derived SGD in modulating mercury trophic transfer in aquatic food webs.

This study reports a spatiotemporal characterization of formaldehyde and acetaldehyde in the summer and winter of 2017 in the urban area of Shiraz, Iran. Sampling was fulfilled according to EPA Method TO-11 A. The inverse distance weighting (IDW) procedure was used for spatial mapping. Monte Carlo simulations were conducted to evaluate carcinogenic and non-cancer risk owing to formaldehyde and acetaldehyde exposure in 11 age groups. The average concentrations of formaldehyde/acetaldehyde in the summer and winter were 15.07/8.40 μg m⁻³ and 8.57/3.52 μg m⁻³, respectively. The formaldehyde to acetaldehyde ratios in the summer and winter were 1.80 and 2.43, respectively. The main sources of formaldehyde and acetaldehyde were photochemical generation, vehicular traffic, and biogenic emissions (e.g., coniferous and deciduous trees). The mean inhalation lifetime cancer risk (LTCR) values according to the Integrated Risk Information System (IRIS) for formaldehyde and acetaldehyde in summer and winter ranged between 7.55 × 10⁻⁶ and 9.25 × 10⁻⁵, which exceed the recommended value by US EPA. The average LTCR according to the Office of Environmental Health Hazard Assessment (OEHHA) for formaldehyde and acetaldehyde in summer and winter were between 4.82 × 10⁻⁶ and 2.58 × 10⁻⁴, which exceeds recommended values for five different age groups (Birth to <1, 1 to <2, 2 to <3, 3 to <6, and 6 to <11 years). Hazard quotients (HQs) of formaldehyde ranged between 0.04 and 4.18 for both seasons, while the HQs for acetaldehyde were limited between 0.42 and 0.97.

Five Descriptors (D) of Marine Strategy Framework Directive (MSFD): marine litter (D10), non-indigenous species (D2) and organic and inorganic pollutants (D8), were estimated in a coastal area of GSA 16 (Augusta harbour, Central Mediterranean Sea) in order to study their effects on the biodiversity (D1) of the benthic community D6) and to improve data for the MSFD. Investigation of plastic debris had led to the identification of 38 fragments divided into four categories, among which microplastics resulted as the most abundant. Six non-indigenous species, belonging to Polychaeta (Kirkegaardia dorsobranchialis, Notomastus aberans, Pista unibranchia, Pseudonereis anomala, Branchiomma bairdi) and Mollusca (Brachidontes pharaonis) were found. Biodiversity and benthic indices suggested a generalised, slightly disturbed ecological status. Anthracene, Zinc and Chrome were the most abundant chemical compounds in analysed sediments. Significant correlations were found between the abundance of trace elements vs biotic indices and between plastic debris vs biodiversity and benthic indices. This study represents the first report about the abundance of plastic debris and its relationship to contaminants and infauna in Augusta harbour. Our results can provide useful information for national and international laws and directives.

Heavy metal pollution of urban stormwater poses potential risks to human and ecosystem health. The design of reliable pollution mitigation strategies requires reliable stormwater modelling approaches. Current modelling practices do not consider the influence of urbanisation characteristics on stormwater quality. This could undermine the accuracy of stormwater quality modelling results. This research study used a database consisting of over 1000 datasets to compare the characteristics of heavy metal build-up (one of the most important stormwater pollutant processes) on urban surfaces under the influence of anthropogenic and natural factors specific to different urban regions from China (Shenzhen) and Australia (Gold Coast), using Bayesian Networks. The outcomes show that the differences in heavy metals build-up loads between the two regions (mean value for Shenzhen – mean value for Gold Coast)/mean value for Shenzhen) were 0.45 (Al), 0.88 (Cr), 0.99 (Mn), 0.68 (Fe), 0.98 (Ni), 0.24 (Cu), 0.47 (Zn) and 0.13 (Pb), respectively. The research outcomes also confirmed that the influence of traffic on the build-up of different sized particles varies between Shenzhen and Gold Coast, and traffic plays distinct roles as a source and as a factor that drives heavy metal re-distribution. The road surface roughness was also found to influence build-up process differently between the two regions. More importantly, the assessment of inherent process uncertainty revealed that heavy metal build-up between different road sites in Shenzhen varies over a wider range than in Gold Coast. The study highlighted a clear distinction in the influence of sources and key anthropogenic factors on the variability of particle-bound heavy metals build-up between geographically different urban regions. The study outcomes provide new knowledge to enhance the accuracy of urban stormwater quality modelling.

Microplastics may lose buoyancy and occur in deeper waters and ultimately sink to the sediment and this may threaten plankton inhabiting in various water layers and benthic organisms. Here, we conduct the first survey on microplastics in the water column and corresponding sediment in addition to the surface water in the Bohai Sea. A total of 20 stations covering whole Bohai Sea were selected, which included 6 stations specified for water column studying. Seawater was sampled every 5 m, with maximal depth of 30 m in the water column using Niskin bottles coupled with a ship-based conductivity, temperature and depth sensor (CTD) system and surface sediment samples were collected using box corer. The results indicated that higher microplastic levels accumulated at a depth range of 5–15 m in the water column in some stations, suggesting the surface water survey was not sufficient to reflect microplastics loading in a water body. Fibers predominated microplastic types in both seawater and sediment of the Bohai Sea, which accounted for 75%–96.4% of the total microplastics. However the relatively proportion of the fibers in the deeper water layers and sediment was lower than that in the surface water. Microplastic shapes are more diverse in the sediment than in the seawater in general. The microplastic sizes changed with depth in the water column and the proportion of the size-fraction < 300 μm increased with depth, probably as a result of rapid biofouling on the small microplastics due to their higher specific surface area. Such depth distribution also implied that sampling with manta net (>330 μm) that commonly used in the oceanographic survey might underestimate microplastics abundance in the water column. Further studies are recommended to focus on the sinking behavior of microplastics and their effects on marine organisms.

We examine the spatio-temporal trends of mercury, a well-known global legacy contaminant, in eleven fish species across all of the Canadian Great Lakes. These particular fish species are selected based on their ecological, commercial, and recreational importance to the biodiversity and fishing industry of the Great Lakes. We present a two-pronged Bayesian methodological framework to rigorously assess mercury temporal trends across multiple fish species and locations. In the first part of our analysis, we develop dynamic linear models to delineate the total mercury levels and rates of change, while explicitly accounting for the covariance between fish length and mercury levels in fish tissues. We then use hierarchical modelling to evaluate the spatial variability of mercury contamination between nearshore and offshore locations, as well as to examine the hypothesis that invasive species have induced distinct shifts on fish mercury contamination trends. Our analysis suggests that the general pattern across the Great Lakes was that the elevated mercury concentrations during the 1970s had been subjected to a declining trend throughout the late 1980s/early 1990s, followed by a gradual stabilization after the late 1990s/early 2000s. The declining trend was more pronounced with top fish predators, whereas benthivorous fish species mainly underwent wax-and-wane cycles with a weaker evidence of a long-term declining trend. Historically contaminated regions, designated as Areas of Concern, and bays receiving riverine inputs are still characterized by mercury concentrations that can lead to consumption restrictions. Lake Erie displayed the lowest mercury levels across all the fish species examined. However, several species of commercial importance showed a reversing (increasing) trend in the 2000s, although their current levels do not pose any major concerns for consumption advisories. These recent trend reversals can be linked with systematic shifts in energy trophodynamics along with the food web alterations induced from the introduction of non-native species, and the potentially significant fluxes from the atmosphere.