Microalgae can excrete exopolymer substances (EPS) with a potential to form hetero-aggregates with microplastic particles. In this work, two freshwater (Microcystis panniformis and Scenedesmus sp.) and two marine (Tetraselmis sp. and Gloeocapsa sp.) EPS producing microalgae were exposed to different microplastics. In this study, the influence of the microplastic particles type, size and density in the production of EPS and hetero-aggregates potential was studied. Most microalgae contaminated with microplastics displayed a cell abundance decrease (of up to 42%) in the cultures. The results showed that the formed aggregates were composed of microalgae and EPS (homo-aggregates) or a combination of microalgae, EPS and microplastics (hetero-aggregates). The hetero-aggregation was dependent on the size and yield production of EPS, which was species specific. Microcystis panniformis and Scenedesmus sp. exhibited small EPS, with a higher propension to disaggregate, and consequently lower capabilities to aggregate microplastics. Tetraselmis sp. displayed a higher ability to aggregate both low and high-density microplastics, being partially limited by the size of the microplastics. Gloeocapsa sp. had an outstanding EPS production and presented excellent microplastic aggregation capabilities (adhered onto the surface and also incorporated into the EPS). The results highlight the potential of microalgae to produce EPS and flocculate microplastics, contributing to their vertical transport and consequent deposition. Thus, this work shows the potential of microalgae as biocompatible solutions to water microplastics treatment.

Apoplastic ascorbate (ASCapo) is an important contributor to the detoxification of ozone (O3). The objective of the study is to explore whether ASCapo is stimulated by elevated O3 concentrations. The detoxification of O3 by ASCapo was quantified in tobacco (Nicotiana L), soybean (Glycine max (L.) Merr.) and poplar (Populus L), which were exposed to charcoal-filtered air (CF) and elevated O3 treatments (E-O3). ASCapo in the three species were significantly increased by E-O3 compared with the values in the filtered treatment. For all three species, E-O3 significantly increased the malondialdehyde (MDA) content and decreased light-saturated rate of photosynthesis (Asat), suggesting that high O3 has induced injury/damage to plants. E-O3 significantly increased redox state in the apoplast (redox stateapo) for all species, whereas no effect on the apoplastic dehydroascorbate (DHAapo) was observed. In leaf tissues, E-O3 significantly enhanced reduced-ascorbate (ASC) and total ascorbate (ASC+DHA) in soybean and poplar, but significantly reduced these in tobacco, indicating different antioxidative capacity to the high O3 levels among the three species. Total antioxidant capacity in the apoplast (TACapo) was significantly increased by E-O3 in tobacco and poplar, but leaf tissue TAC was significantly enhanced only in tobacco. Leaf tissue superoxide anion (O2•-) in poplar and hydrogen peroxide (H2O2) in tobacco and soybean were significantly increased by E-O3. The diurnal variation of ASCapo, with maximum values occurring in the late morning and lower values experienced in the afternoon, appeared to play an important role in the harmful effects of O3 on tobacco, soybean and poplar.

The effect of selenium (Se) on the reproductive system has been investigated in both humans and vertebrates, but few studies of female fertility and reproduction in invertebrate have been reported. This study is aimed to investigate the effect of SeMet on growth performance and reproductive system after crayfish were fed with graded levels of dietary SeMet (0, 1.49, 3.29, 10.02, 30.27 or 59.8 μg Se/g dry weight) for 60 days. Crayfish treated with the high levels of SeMet (10.02, 30.27 and 59.76 μg Se/g) exhibited decreasing FW and CL in both male and female. Interestingly, Se accumulation was higher in ovary than in other tissues, suggesting that ovary may serve as a target organ for Se accumulation. We found that dietary Se concentration of 10.02 μg Se/g significantly improved the spawning rate, promoted the synchronized spawning, and up-regulated the expressions of mRNA of cdc2 and vitellogenin, with significantly increased E2 and VTG concentrations in hemolymph of female crayfish. However, a marked decrease of the E2 contents and spawning rate was observed in the groups treated with 30.27 and 59.76 μg Se/g diets. In conclusion, the results of this study indicated that the Se had maximum accumulation in ovary, affecting the reproductive capacity by intervening the expression of cdc2 and vitellogenin in the reproductive system. The LOAEL to induce FW was observed in crayfish fed with 10.02 μg Se/g diet, and its value can cause toxicity within the range of natural concentration, so the addition of Se in the feed should be within 10.02 μg Se/g.

The presence of xenobiotics in the aquatic environment has drawn scientific concern due to possible detrimental effects on the ecosystems. With EU Decision 2015/495, a first Watch list of compounds that could potentially represent a threat for the environment was created, with the objective of gathering high quality monitoring data and support their prioritization. Literature data are still very scarce and the presence of many of the compounds has not been investigated thoroughly. In this study, all the 17 compounds of the EU Watch list 2015/495 were monitored in 14 sampling locations, comprised of freshwater and, for the first time, wastewater. The study was carried out in the Ebro delta, in the north east of Spain, a representative and crucial area not only for its environmental and naturalistic significance, but also for Spain’s productivity, especially as regards rice agriculture. Results show that contamination originates both from wastewater treatment plants (WWTPs) and agricultural activities. High levels of pharmaceuticals were detected in wastewater, with azithromycin and diclofenac present at mean concentrations of 1.65 μg/L and 636 ng/L respectively. In freshwater samples, besides antibiotics and diclofenac, substantial contamination by pesticides was reported, with oxadiazon reaching up to 591 ng/L and imidacloprid being present in 93% of samples. Moreover, the study provided insight into the origin of the selected contaminants. The removal of the studied micropollutants in WWTPs was low to moderate. The assessment of risk quotients, calculated based on the available PNECs, demonstrated that the concentrations recorded for these compounds may pose a significant risk in most sampling sites.

659 water samples from springs and wells in the Sabatini and Vicano-Cimino Volcanic Districts (central Italy) were analyzed for arsenic (As), fluoride (F⁻) and radon (²²²Rn) concentrations. Waters mostly sourced from a shallow and cold aquifer hosted within volcanic rocks, which represents the main public drinking water supply. Cold waters from perched aquifers within sedimentary formations and thermal waters related to a deep hydrothermal reservoir were also analyzed. The highest concentrations of As and F⁻ were measured in the thermal waters and attributed to their enhanced mobility during water-rock interaction processes at hydrothermal temperatures. Relatively high concentrations of As and F⁻ were also recorded in those springs and wells discharging from the volcanic aquifer, whereas waters hosted in the sedimentary units showed significantly lower contents. About 60% (As) and 25% (F⁻) of cold waters from the volcanic aquifer exceeded the maximum allowable concentrations for human consumption. Such anomalously high levels of geogenic pollutants were caused by mixing with fluids upwelling through faulted zones from the hydrothermal reservoir. Chemical weathering of volcanic rocks and groundwater flow path were also considered to contribute to the observed concentrations. Cold waters from the volcanic aquifer showed the highest ²²²Rn concentrations, resulting from the high contents of Rn-generating radionuclides in the volcanic units. Approximately 22% of these waters exceeded the recommended value for human consumption. A specific Quality Index (QI), comprised between 1 (very low) and 4 (very high), was computed for each water on the basis of As, F⁻ and ²²²Rn concentrations and visualized through a spatial distribution map processed by means of geostatistical techniques. This map and the specific As, F⁻ and ²²²Rn maps can be regarded as useful tools for water management by local authorities to both improve intervention plans in contaminated sectors and identify new water resources suitable for human consumption.

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.

Polycyclic aromatic hydrocarbons (PAHs) are organic compounds composed of at least two benzene rings. This paper reviews the characteristics, sources and health risk of airborne particulate PAHs in Chinese cities. The airborne particulate PAH concentrations varied from 3.35 to 910 ng m⁻³, with an average of 75.0 ng m⁻³, and the pollution level of PAHs in northern cities was generally higher than that in southern cities. The PAH concentrations in different cities underwent similar seasonal variations, with high concentrations in the winter and relatively low concentrations in the summer. Many factors, such as meteorological conditions and source emissions, influenced the spatiotemporal pattern of PAHs. High temperatures, frequent flow exchanges, abundant rainfall and strong solar radiation reduced the level of particulate PAHs in the atmosphere. The historical changes in the level of airborne particulate PAHs in four cities were analyzed. The PAH concentrations in Beijing and Taiyuan presented a trend of first increasing and then decreasing, while the level of particulate PAHs in Nanjing and Guangzhou had a decreasing tendency from year 2000–2015. The airborne particulate PAHs in cities were derived from several sources, including coal combustion, vehicle emissions, coking industries, biomass burning and petroleum volatilization. The results of a health risk assessment indicated that the incremental lifetime cancer risk (ILCR) for people in the northern cities was higher than that for people in the other regions, especially during the cold season. Moreover, adults were at greater risk than people in other age groups, and the health risk to females was slightly higher than that to males. The potential risk of airborne particulate PAH exposure was relatively high in some cities, and controlling PAH emissions at the source should be required to prevent pollution.

Adsorption and fractionation of Pt, Pd and Rh (defined here as platinum group elements, PGEs) onto the representative inorganic microparticles, including Fe2O3, MnO2, CaCO3, SiO2, Al2O3 and kaolinite in seawater were investigated. The effects of macromolecular organic compounds (MOCs) as the representatives of organic matter, including humic acids (HA), bovine serum albumin (BSA) and carrageenan, on the adsorption were also studied considering that organic matter is ubiquitous in seawater and indispensable to marine biogeochemical cycles. In the absence of MOCs, the representative mineral particles Fe2O3 and MnO2 had the strongest interaction with PGEs. The adsorption of PGEs onto the representative biogenic particles SiO2 and CaCO3 and lithogenic particles Al2O3 and kaolinite was similar or weaker than onto the mineral particles. MOCs inhibited the interaction between PGEs and the particles except for Pt and Pd onto the biogenic particles in artificial seawater. This impediment may be closely related to the interaction between particles, MOCs and elements. The partition coefficient (log Kd) of Pt was similar (∼4.0) in the presence of MOCs, indicating that the complexation between Pt and MOCs was less important than hydrolysis or adsorption onto the acid oxide particle surface. Rh tended to fractionate onto the mineral and lithogenic particles in the presence of HA and carrageenan, while Pd was more likely to fractionate onto the biogenic particles. However, BSA enhanced the fractionation tendency of Pd onto the mineral particles. The results indicate that the adsorption behavior of Pd onto inorganic particles was significantly affected by the composition or the type of MOCs. Hence, the interaction between PGEs and inorganic particles may be greatly affected by the macromolecular organic matter in the ocean.

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.

Microplastics can enter freshwater lakes through many sources. They can act as carriers to adsorb bacteria, virus, or pollutants (e.g., heavy metal and toxic organic compounds) that threaten human health through food chain. Microplastics can exist in surface water and sediments in freshwater lakes after they enter the lakes through discharge points. Wastewater discharge is the main cause of lake eutrophication and is the main emission source of microplastics. The correlation between lake trophic state and microplastic abundance has been rarely reported. This study investigated the microplastic contamination in surface water and sediments of 18 lakes along the middle and lower reaches of the Yangtze River Basin in the period of August–September 2018. The correlation between lake trophic state and microplastic abundance in surface water and sediments was investigated and discussed. The microplastic abundance in surface water was approximately two orders of magnitude lower than that in sediments in all 18 lakes. Hong Lake had the highest microplastic abundance in surface water sample, and Nantaizi Lake had the highest microplastic abundance in sediment sample. The dominant microplastic shape was fiber of 93.81% in surface water sample and 94.77% in sediment sample. Blue-colored microplastics were dominant in nearly all lakes in surface water sample (around 40%–60%) and sediment sample (around 60%–80%), followed by purple- and green-colored ones. The microplastics size <1 mm was dominant in surface water sample (around 40%–60%) and sediment sample (around 50%–80%). The dominant material was polypropylene in surface water sample (around 60%–80%) and sediment sample (around 40%–60%).