Attenuation of organic pollutants and the effects of salinity and seasonality in a Mediterranean micro-estuary

Sedimentary co-exposure to bis(2-ethylhexyl) phthalate and titanium dioxide nanoparticles aggravate ecotoxicity and ecological risks through disrupted bioenergetics in Caenorhabditis elegans

Emerging contaminants in estuarine sediments, such as bis(2-ethylhexyl) phthalate (DEHP) and titanium dioxide nanoparticles (nTiO2), pose ecotoxicological risks that may be exacerbated by co-contamination. This study investigated the impacts of DEHP, nTiO2, and their combinations at environmentally relevant concentrations (1, 10, and 100 μg/g) on the soil nematode Caenorhabditis elegans in estuarine-like sediment (14.25‰ salinity). Life history traits and bioenergetics endpoints were examined, with a sample size of ≥ 45 worms or 9 technical repeats per treatment. While individual exposures did not affect growth, the combination of DEHP (1 μg/g) and nTiO2 (100 μg/g) significantly reduced body length by 19%. Single exposure reduced total offspring by 18-41%, whereas the combination of DEHP and nTiO2 synergistically worsened reproductive toxicity (52-74% inhibition), as revealed by Loewe's additivity model and Bliss's independence. DEBtox modeling revealed a shift in physiological mode of action from "increased reproductive costs" in singular exposures to "increased growth and reproductive cost" in co-exposure. Moreover, co-exposure significantly intensified the impacts on bioenergetics-related endpoints, including ATP level (single exposure: 33-34%; co-exposure: 56%), mitochondrial damage (single exposure: 15-17%; co-exposure: 40%), and oxidative stress (single exposure: 5-7%; co-exposure: 13%). Risk quotients based on reproductive toxicity EC10 and DEBtox-derived zb suggested that environmental concentrations of DEHP and nTiO2 pose high risks in global estuarine sediments, with a 2-fold increase during co-exposure. This study demonstrates that co-contamination of DEHP and nTiO2 synergistically aggravates ecotoxicities through disrupted energy allocation, highlighting the importance of assessing mixture toxicity in environmental risk assessment of estuarine sediments.

Fractionation and tidal characteristics of per- and polyfluoroalkyl substances in the estuarine maximum turbidity zone

Complex tidal processes and suspended particulate matter (SPM) behavior influence the land-sea transport of terrestrial contaminants in estuaries. Contaminants are generally trapped within the estuarine maximum turbidity zone (MTZ), where SPM concentrations peak, misleading flux estimation. Here, we conducted high-resolution continuous sampling over two tidal cycles within the MTZ of a semidiurnal estuary. Tidal variations of per- and polyfluoroalkyl substances (PFAS), a class of persistent organic pollutants, were analyzed in dissolved water and size-fractionated SPM. Results showed that variations in dissolved PFAS may related to the mixing of upstream and downstream. The predominant size range for SPM was found in 1-31 μm (75 %, mainly 10-31 μm), but the PFAS tended to be sorbed by 0.22-1 μm (60 %) and > 31 μm (37 %) fractions. Except during periods of sediment resuspension when particulate PFAS concentration decreased, the PFAS concentration in the 1-31 μm increased during flood tides and decreased during ebb tides, which may not be related to organic carbon/elemental carbon levels. The hourly dynamic flux of dissolved-phase and particulate-phase PFAS transport to the sea in the MTZ was calculated by combining it with a hydrodynamic model. This study first highlights the size-fractionated PFAS transport under tidal influences and provides hourly flux estimation with a hydrodynamic model.

Insights into pollution characteristics and human health risks of plasticizer phthalate esters in shellfish species

The ubiquitous application of phthalate esters (PAEs) as plasticizers contributes to high levels of marine pollution, yet the contamination patterns of PAEs in various shellfish species remain unknown. The objective of this research is to provide the first information on the pollution characteristics of 16 PAEs in different shellfish species from the Pearl River Delta (PRD), South China, and associated health risks. Among the 16 analyzed PAEs, 13 were identified in the shellfish, with total PAE concentrations ranging from 23.07 to 3794.08 ng/g dw (mean = 514.35 ng/g dw). The PAE pollution levels in the five shellfish species were as follows: Ostreidae (mean = 1064.12 ng/g dw) > Mytilus edulis (mean = 509.88 ng/g dw) > Babylonia areolate (mean = 458.14 ng/g dw) > Mactra chinensis (mean = 378.90 ng/g dw) > Haliotis diversicolor (mean = 335.28 ng/g dw). Dimethyl phthalate (DMP, mean = 69.85 ng/g dw), diisobutyl phthalate (DIBP, mean = 41.39 ng/g dw), dibutyl phthalate (DBP, mean = 130.91 ng/g dw), and di(2-ethylhexyl) phthalate (DEHP, mean = 226.23 ng/g dw) were the most abundant congeners. Notably, DEHP constituted the most predominant fraction (43.98 %) of the 13 PAEs detected in all shellfish from the PRD. Principal component analysis indicated that industrial and domestic emissions served as main sources for the PAE pollution in shellfish from the PRD. It was estimated that the daily intake of PAEs via shellfish consumption among adults and children ranged from 0.004 to 1.27 μg/kgbw/day, without obvious non-cancer risks (< 0.034), but the cancer risks raised some alarm (2.0 × 10-9-1.4 × 10-5). These findings highlight the necessity of focusing on marine environmental pollutants and emphasize the importance of ongoing monitoring of PAE contamination in seafood.

Accumulation and elimination properties and comparative toxicity of fluxapyroxad in juvenile and adult large yellow croaker (Larimichthys crocea)

Fluxapyroxad (FX), a succinate dehydrogenase inhibitor fungicide, has been detected in global marine and aquatic organisms. However, as a new pollutant, its biotoxicity and ecological risks to marine aquatic organisms are unclear. The accumulation and elimination processes and toxic effects of FX on Larimichthys crocea (L. crocea) at environmental concentrations were assessed. FX (1.0 μg/L) was rapidly enriched and persisted prolonged in L. crocea muscle and FX is highly toxic to juvenile L. crocea with the 96 h LC50 of 245.0 μg/L. Furthermore, the toxic effects of FX on juvenile L. crocea and adults L. crocea were compared and analyzed. In contrast to those of adult L. crocea, juvenile L. crocea showed a stronger oxidative stress response and rescued liver damage in terms of antioxidant enzyme activity, energy supply, and liver damage to FX. Transcriptomic analysis also showed that drug metabolism was activated. In the adult L. crocea, the disturbance of the energy metabolism, oxidative respiration, TCA cycle, and lipid metabolism genes were firstly found. The results revealed the accumulation and elimination pattern and ecotoxicological hazards of FX to L. crocea, which provided important theoretical basis for the study of environmental risks caused by new pollutants to marine organisms.

Pesticides and pharmaceuticals data collected during two consecutive years in a Mediterranean micro-estuary

The Alexander micro-estuary, located at the eastern edge of the Mediterranean Sea, is a typical example of small water bodies that suffer from a combination of urban and agricultural pollution, and overuse of its natural water sources. It is∼6.5 km long, with maximum depth of 3 m and maximum width of 45 m. To evaluate the anthropogenic stress on the system and its ability to mitigate pollution, water samples were collected within the framework of Ruppin's Estuarine and Coastal Observatory [1]. Water samples were collected from the estuary head, which drains about 510 km2, and at a point 300 m upstream from the estuary mouth before water flows into the Mediterranean Sea. A total of 236 stormwater and 44 base-flow water samples between December 2016 and December 2018. Stormwater samples were collected every 0.25 - 4 h along the entire course of the flow events using an automated samplers (Sigma 900, Hach Company, Loveland CO, USA; and ISCO 3700 Full-Size Portable Sampler, Teledyne, Lincoln, NE, USA). Base-flow samples were taken once a month using a horizontal grab sampler (5 L, model 110B, OceanTest Equipment, Fort Lauderdale, FL, USA). All samples were filtered using 90mmGF/F filters (nominal pore size of 0.7 µm, MGF, Sartorius, Göttingen, Germany) and immediately frozen (-20°C) before chemical analysis. Chemical analysis was performed using liquid chromatography with high-resolution mass spectrometry (LC-HRMS) analysis using a QExactive Plus hybrid FT mass spectrometer coupled with a Dionex Ultimate 3000 RS UPLC (Thermo Fisher Scientific, Waltham, MA, USA). The targeted analysis, which included 15 fungicides, 25 herbicides, 18 Insecticides, and 19 pharmaceuticals, concluded with a total of 21,142 entries. All entries are organized in a worksheet, along with location, date, flood section duration, discharge rate, and the total water volume discharged during the relevant period. The provided data offers an opportunity to explore the sources, transport, and impact of a large mixture of organic pollutants in a confined aquatic system located in an urbanized coastal environment.

Investigation and comparative analysis of ecological risk for heavy metals in sediment and surface water in east coast estuaries of India

The sediments and surface water from 8 stations each from Dhamara and Paradeep estuarine areas were sampled for investigation of heavy metals, Cd, Cu, Pb, Mn, Ni, Zn, Fe, and Cr contamination. The objective of the sediment and surface water characterization is to find the existing spatial and temporal intercorrelation. The sediment accumulation index (I_sed), enrichment index (I_En), ecological risk index (I_EcR) and probability heavy metals (p-HMI) reveal the contamination status with Mn, Ni, Zn, Cr, and Cu showing permissible (0 ≤ I_sed ≤ 1, I_En ˂ 2, I_EcR ≤ 150) to moderate (1 ≤ I_sed ≤ 2, 40 ≤ R_f ≤ 80) contamination. The p-HMI reflects the range from excellent (p-HMI = 14.89-14.54) to fair (p-HMI = 22.31-26.56) in off shore stations of the estuary. The spatial patterns of the heavy metals load index (I_HMc) along the coast lines indicate that the pollution hotspots are progressively divulged to trace metals pollution over time. Heavy metal source analysis coupled with correlation analysis and principal component analysis (PCA) was used as a data reduction technique, which reveals that the heavy metal pollution in marine coastline might originate from redox reactions (FeMn coupling) and anthropogenic sources.