In this study, nine congeners of polybrominated diphenyl ethers (PBDEs) and sixteen congeners of polycyclic aromatic hydrocarbons (PAHs) were measured in water samples to elucidate their spatial distribution, congener profiles, sources and ecological risks in the Guanlan River during both the dry season (DS) and the wet season (WS). The concentration of Σ9PBDE ranged from 58.40 to 186.35 ng/L with an average of 115.72 ng/L in the DS, and from 8.20 to 37.80 ng/L with an average of 22.15 ng/L in the WS. Meanwhile, the concentration of Σ16PAHs was ranged from 121.80 to 8371.70 ng/L with an average of 3271.18 ng/L in the DS and from 1.85 to 7124.25 ng/L with an average of 908.11 ng/L in the WS. The concentrations of PBDEs and PAHs in the DS were significantly higher than those in the WS, probably due to the dilution of the river during the rainy season. Moreover, the spatial distribution of pollutants revealed decreasing trend in the concentration from upstream to downstream and almost identical pattern was observed during both seasons. The source apportionment suggested that penta-BDE and to some extent octa-BDE commercial products were major sources of PBDEs in the study area. However, the sources of PAHs were mainly comprised of fossil fuels and biomass burning, followed by the petroleum products and their mixtures. The results of the ecological risk assessment indicated PBDEs contamination posed high ecological risks, while PAHs exhibited low or no ecological risks in the study area. Consistent with the environmental levels, the ecological risks of pollutants were relatively lower in the WS, compared to that in the DS. The results from this study would provide valuable baseline data and technical support for policy makers to protect the ecological environment of the Guanlan River.

Flame retardants (FRs), such as brominated flame retardants (BFRs) and organophosphorus flame retardants (OPFRs), are diverse groups of compounds used in various products related to the indoor environment. In this study concentrations of eight polybrominated diphenyl ethers (PBDEs), two alternative BFRs and ten OPFRs were determined in indoor dust (n = 20) and pet cat hair (n = 11) from South Africa. The OPFRs were the major FRs, contributing to more than 97% of the total FR concentration. The median Ʃ₁₀OPFRs concentrations were 44,800 ng/g in freshly collected dust (F-dust), 19,800 ng/g in the dust collected from vacuum cleaner bags (V-dust), and 865 ng/g in cat hair (C-hair). Tris(1-chloro-2-propyl) phosphate (TCIPP) was the dominant OPFR in the dust samples with median concentrations of 7,010 ng/g in F-dust and 3,590 ng/g in V-dust. Tris(2-butoxyethyl) phosphate (TBOEP) was the dominant OPFR in C-hair, with a median concentration of 387 ng/g. The concentrations of Ʃ₈PBDEs were higher in F-dust than in V-dust. BDE209 was the dominant BFR in all three matrices. Bis(2-ethylhexyl)-3,4,5,6-tetrabromo-phthalate (BEH-TEBP) and 2-ethylhexyl-2,3,4,5- tetrabromobenzoate (EH-TBB) showed notable contributions to the BFR profile in cat hair. A worst-case dust exposure estimation was performed for all analytes. The estimated TCIPP daily intake through dust ingestion was up to 1,240 ng/kg bw for toddlers. The results indicate that OPFRs are ubiquitous in South African indoor environment. Indoor dust is a major source of human exposure to environmental contaminants. This can for example occur through hand-to-mouth contact of toddlers, and is an important route of exposure to currently used FRs accumulated on dust particles. The presence of FRs, in particular high concentrations of OPFRs, suggests that children and indoor pet cats may have greater exposure to FRs than adults.

Understanding the mercury (Hg) methylation process is important for the management of paddy soils contaminated by Hg. In this work, samples of eighteen paddy soils with varying soil properties were spiked with inorganic Hg and subjected to a 90 d flooding period. Soil pH and redox potential (Eh) were measured in situ at intervals, and soils were sampled for the analysis of methylmercury (MeHg). The Hg methylation efficiency increased with flooding time and reached a relatively steady state at 30 d of incubation, ranging from 0.08% to 2.52%, and was significantly correlated with the in situ soil pH and Eh. The Elovich equation could adequately describe the kinetic production of MeHg. MeHg production was well predicted by the in situ soil pH and Eh of flooded soils, in addition to the organic matter content of air-dried soil samples and flooding time. The two predictive models explained 78% and 68% of the variability of the Hg methylation efficiency. The results suggested that the methylation of inorganic Hg in paddy soils after flooding can be predicted as a function of routinely measured soil properties and flooding time, a correlation that can be utilized to improve understanding of the extent of Hg methylation and the management of Hg-contaminated paddy soils.

Though the toxicity of strobilurins on non-target aquatic organisms has been characterized, the associated toxic mechanisms have not been fully explored. The present study showed that the larval stage was the most sensitive developmental stage in zebrafish, and pyraclostrobin (PY) had the highest acute toxicity to embryos, larvae, juvenile and adult with 96 h-LC₅₀ at 0.048 mg/L, 0.029 mg/L, 0.039 mg/L, 0.031 mg/L respectively, when compared with the toxicity of trifloxystrobin (TR), kresoxim-methyl (KM) and azoxystrobin (AZ) at corresponding developmental stage. Then we investigated the transcriptomics and developmental toxicity of TR, KM, AZ and PY on zebrafish embryos after 72 h exposure. RNA-seq revealed that the pathways related to cell apoptosis and cancer, and cellular components organelle membrane and mitochondrion, were markedly affected after TR, KM, AZ and PY exposure during zebrafish early life stages. The results were further confirmed by the induction of antioxidant enzymes catalase (CAT) and superoxide dismutase (SOD) activities, the elevation of H₂O₂, malondialdehyde (MDA) and reactive oxygen species (ROS) level, as well as the reduction of intracellular calcium ions (Ca²⁺) and mitochondrial membrane potential (MMP), which indicated that strobilurins could cause mitochondrial dysfunction and cell apoptosis. The present study was performed a systematic analysis of strobilurins to zebrafish at multi-levels, which provided suggestions for further investigation of molecular mechanisms underlying the toxicity induced by strobilurins on aquatic organisms.

Microplastics are a significant issue in the world's oceans. These small plastic particles (<5 mm in size) are becoming globally ubiquitous in the marine environment and are ingested by various fish species. Here we investigate the incidence of microplastics in juvenile Chinook salmon and their nearshore marine environments on the east coast of Vancouver Island, British Columbia. We completed a series of beach seines, plankton tows and sediment cores in nearshore areas of importance to juvenile salmon. Microplastics were extracted from fish, water and sediment samples and concentrations were quantified. Microplastics analysis, consisting predominantly of fibrous plastics, showed juvenile Chinook salmon contained 1.2 ± 1.4 (SD) microplastics per individual while water and sediment samples had 659.9 ± 520.9 microplastics m⁻³ and 60.2 ± 63.4 microplastics kg⁻¹ dry weight, respectively. We found no differences in microplastic concentrations in juvenile Chinook and water samples among sites but observed significantly higher concentrations in sediment at the Deep Bay site compared to Nanaimo and Cowichan Bay sites. Chinook microplastic concentrations were relatively low compared to literature values and, given the size and type of microplastics we observed, are unlikely to represent an immediate threat to fish in this area. However, microplastics less than 100 μm in size were not included in the study and may represent a greater threat due to their ability to translocate through tissues.

This study investigates the dynamics of glyphosate and AMPA in the soil surface layer of two fields growing glyphosate-resistant crops in the loess Pampas of Córdoba Province, Argentina. Glyphosate decay and AMPA formation/decay were studied after a single application, using decay kinetic models. Furthermore, glyphosate and AMPA concentrations were investigated in runoff to evaluate their off-site risk. During a 2.5-month study, cultivations of glyphosate-resistant soybean and maize received an application of 1.0 and 0.81 kg a.e. ha⁻¹, respectively, of Roundup UltraMax©. Topsoil samples (0–1, 1–2 cm) were collected weekly (including before application) and analysed for glyphosate, AMPA and soil moisture (SM) contents. Runoff was collected from runoff plots (3 m²) and weirs after 2 erosive rainfall events, and analysed for glyphosate and AMPA contents (water, eroded-sediment). Under both cultivations, background residues in soil before application were 0.27–0.42 mg kg⁻¹ for glyphosate and 1.3–1.7 mg kg⁻¹ for AMPA. In the soybean area, the single-first-order (SFO) model performed best for glyphosate decay. In the maize area, the bi-phasic Hockey-Stick (HS) model performed best for glyphosate decay, due to an abrupt change in SM regimes after high rainfall. Glyphosate half-life and DT₉₀ were 6.0 and 19.8 days, respectively, in the soybean area, and 11.1 and 15.4 days, respectively, in the maize area. In the soybean area, 24% of the glyphosate was degraded to AMPA. In the maize area, it was only 5%. AMPA half-life and DT₉₀ were 54.7 and 182 days, respectively, in the soybean area, and 71.0 and 236 days, respectively, in the maize area. Glyphosate and AMPA contents were 1.1–17.5 times higher in water-eroded sediment than in soil. We conclude that AMPA persists and may accumulate in soil, whereas both glyphosate and AMPA are prone to off-site transport with water erosion, representing a contamination risk for surface waters and adjacent fields.

This study analyzes microplastic ingestion by three deep-water elasmobranch species (Galeus melastomus, Scyliorhinus canicula and Etmopterus spinax) from the Tyrrhenian Sea, discriminating between stomach and intestine contents. The absence of significant differences in frequency and abundance of plastic items into stomachs seems to suggest that ecological diversity among the three sharks does not strongly influence the probability of plastic ingestion in the study area. On the other hand, the detected differences in the microplastic content into the intestine might be due to a different retention time of microplastics, suggesting how feeding habits could influence metabolic features, and therefore affect the recovery of ingested plastic items. This information would improve the future development of marine micro-litter monitoring systems, following the MSFD requirements. Moreover, this study shows that all the three examined elasmobranch species can give important information even with relatively small sample sizes (N ≈ 30), and they could be used as target species for monitoring micro-litter ingestion in deep-water habitats.

The intensive use of Cu-based pesticides in agriculture could have an unintended impact on the ecosystems and human health via different exposure pathways. This paper presents the results of experiments involving colloidal stability, aggregation, and dissolution of Cu₂O commercial pesticide under various environmental conditions in view of ecological implications. The investigated pesticide contains ∼750 g kg⁻¹ Cu (75% weight of product), Cu₂O particles with sizes < 1 μm, and nominal size fraction of Cu₂O nanoparticles. The co-presence of Ca²⁺ (20 mM) and humic acid (HA, 15 mg L⁻¹) significantly modulates (p < 0.001) the colloidal stability and mobility of particles. The dissolution of Cu at pH 5.5 was about 85%, 90%, and 75% weight more than the dissolution of Cu at pH 7.0, pH 8.5, and pH 7.0 and pH 8.5 combined, respectively in all dispersions. However, increasing HA content from 0 to 15 mg L⁻¹ reduced the dissolution of Cu by 56%, 50%, and 40% weight at pH 5.5, 7.0, and 8.5, respectively. Thus, pH below 7.0 is a critical factor to control the dissolution and bioavailability of Cu that may pose ecotoxicity and environmental pollution, whereas pH above 7.0 and the presence of HA attenuate the pH effect. These findings provide insight into how the potential mobility and bioavailability of Cu is modulated by the water chemistry under various environmental scenarios and media.

The low-cost and compact size of light-scattering-based particulate matter (PM) sensors provide an opportunity for improved spatiotemporally resolved PM measurements. However, these inexpensive sensors have limitations and need to be characterized under realistic conditions. This study evaluated two Plantower PMS (particulate matter sensor) 1003s and two PMS 5003s outdoors in Salt Lake City, Utah over 320 days (1/2016–2/2016 and 12/2016–10/2017) through multiple seasons and a variety of elevated PM2.5 events including wintertime cold-air pools (CAPs), fireworks, and wildfires. The PMS 1003/5003 sensors generally tracked PM2.5 concentrations compared to co-located reference air monitors (one tapered element oscillating microbalance, TEOM, and one gravimetric federal reference method, FRM). The different PMS sensor models and sets of the same sensor model exhibited some intra-sensor variability. During winter 2017, the two PMS 1003s consistently overestimated PM2.5 by a factor of 1.89 (TEOM PM2.5<40 μg/m3). However, compared to the TEOM, one PMS 5003 overestimated PM2.5 concentrations by a factor of 1.47 while the other roughly agreed with the TEOM. The PMS sensor response also differed by season. In two consecutive winters, the PMS PM2.5 measurements correlated with the hourly TEOM measurements (R2 > 0.87) and 24-h FRM measurements (R2 > 0.88) while in spring (March–June) and wildfire season (June–October) 2017, the correlations were poorer (R2 of 0.18–0.32 and 0.48–0.72, respectively). The PMS 1003s maintained high intra-sensor agreement after one year of deployment during the winter seasons, however, one PMS 1003 sensor exhibited a significant drift beginning in March 2017 and continued to deteriorate through the end of the study. Overall, this study demonstrated good correlations between the PMS sensors and reference monitors in the winter season, seasonal differences in sensor performance, some intra-sensor variability, and drift in one sensor. These types of factors should be considered when using measurements from a network of low-cost PM sensors.

An anaerobic incubation was launched with varying nitrate (1, 5, 10 and 20 mM exogenous NaNO₃) and molybdate (20 mM Na₂MoO₄, a sulfate-reducing inhibitor) additions to investigate the characteristics of PCP dechlorination, as well as the reduction of natural co-occurring electron acceptors, including NO₃⁻, Fe(III) and SO₄²⁻, and the responses of microbial community structures under a unique reductive mangrove soil. Regardless of exogenous addition, nitrate was rapidly eliminated in the first 12 days. The reduction process of Fe(III) was inhibited, while that of SO₄²⁻ reduction depended on addition concentration as compared to the control. PCP was mainly degraded from orth-position, forming the only intermediate 2,3,4,5-TeCP by anaerobic microbes, with the highest PCP removal rate of average 21.9% achieved in 1 and 5 mM NaNO₃ as well as 20 mM Na₂MoO₄ treatments and the lowest of 7.5% in 20 mM NaNO₃ treatment. The effects of nitrate on PCP dechlorination depended on addition concentration, while molybdate promoted PCP attenuation significantly. Analyses of the Illumina sequencing data and the relative abundance of dominant microorganisms indicated that the core functional groups regulated PCP removal at genera level likely included Bacillus, Pesudomonas, Dethiobacter, Desulfoporosinus and Desulfovbrio in the nitrate treatments; while that was likely Sedimentibacter and Geosporobacter_Thermotalea in the molybdate treatment. Nitrate supplement but not over supplement, or addition of molybdate are suggested as alternative strategies for better remediation in the nitrate-deficient and sulfur-accumulated soil ecosystem contaminated by PCP, through regulating the growth of core functional groups and thereby coordinating the interaction between dechlorination and its coupled soil redox processes due to shifts of more available electrons to dechlorination. Our results broadened the knowledge regarding microbial PCP degradation and their interactions with natural soil redox processes under anaerobic soil ecosystems.