Humpback whales (Megaptera novaeangliae) from the Southern Hemisphere carry information on persistent organic pollutants (POPs) from their feeding zones in Antarctica to their breeding grounds, making this species a sentinel of contaminants accumulation in the Southern Ocean. This study aimed to evaluate driving factors, namely feeding areas, trophic level, and sex, affecting POP concentrations in the blubber of humpback whales breeding off Mozambique and off Ecuador. Biopsies of free-ranging humpback whales including blubber and skin were collected in 2014 and 2015 from Ecuador (n = 59) and in 2017 from Mozambique (n = 89). In both populations, HCB was the major contaminant followed by DDTs > CHLs > PCBs > HCHs > PBDEs. POP concentrations were significantly higher in males compared to females. HCB, DDTs, HCHs and PBDEs were significantly different between whales from the Mozambique population and the Ecuador population. Sex and feeding habits were important driving factors accounting for POP concentrations in Ecuador whales. The whales from our study had some of the lowest POP concentrations measured for humpback whales in the world. These whales fed predominantly on krill as reflected from the low δ¹³C and δ¹⁵N values measured in the skin. However, the isotopic niches of whales from Mozambique and Ecuador did not overlap indicating that the two populations are feeding in different areas of the Southern Ocean.

Total concentrations of hydrophobic organic contaminants (HOCs) in sediment present a poor quality assessment parameter for aquatic organism exposure and environmental risk because they do not reflect contaminant bioavailability. The bioavailability issue of HOCs in sediments can be addressed by application of multi-ratio equilibrium passive sampling (EPS). In this study, riverbed sediment samples were collected during the Joint Danube Survey at 9 locations along the Danube River in 2013. Samples were ex-situ equilibrated with silicone passive samplers. Desorption isotherms were constructed, yielding two endpoints: pore water (CW:₀) and accessible (CAS:₀) concentration of polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), polycyclic aromatic hydrocarbons (PAHs) and polybrominated diphenyl ethers in sediment. CW:₀ concentrations of DDT and its breakdown products exhibited elevated levels in the low Danube, with the maximum in the river delta. Other investigated HOCs did not show any clear spatial trends along the river, and only a moderate CW:₀ variability. CAS:₀ in sediment ranged from 10 to 90% of the total concentration in sediment. CW:₀ was compared with freely dissolved concentration in the overlaying surface water, measured likewise by passive sampling. The comparison indicated potential compound release from sediment to the water phase for PAHs with less than four aromatic rings, and for remaining HOCs either equilibrium between sediment and water, or potential compound deposition in sediment. Sorption partition coefficients of HOC to organic carbon correlated well with octanol-water partition coefficients (KOW), showing stronger sorption of PAHs to sediment than that of PCBs and OCPs having equal logKOW. Comparison of CW:₀ values with European environmental quality standards indicated potential exceedance for hexachlorobenzene, fluoranthene and benzo[a]pyrene at several sites. The study demonstrates the utility of passive sampling as an innovative approach for risk-oriented monitoring of HOCs in river catchments.

Bisphenol A (BPA) is a harmful environmental contaminant acting as an endocrine disruptor in animals, but it also affects growth and development in plants. Here, we have elucidated the functional mechanism of root growth inhibition by BPA in Arabidopsis thaliana using mutants, reporter lines and a pharmacological approach. In response to 10 ppm BPA, fresh weight and main root length were reduced, while auxin levels increased. BPA inhibited root growth by reducing root cell length in the elongation zone by suppressing expansin expression and by decreasing the length of the meristem zone by repressing cell division. The inhibition of cell elongation and cell division was attributed to the enhanced accumulation/redistribution of auxin in the elongation zone and meristem zone in response to BPA. Correspondingly, the expressions of most auxin biosynthesis and transporter genes were enhanced in roots by BPA. Taken together, it is assumed that the endocrine disruptor BPA inhibits primary root growth by inhibiting cell elongation and division through auxin accumulation/redistribution in Arabidopsis. This study will contribute to understanding how BPA affects growth and development in plants.

A dissolved air flotation (DAF) system is one of the water treatment processes that purifies contaminants through a buoyancy effect by attaching the moiety of micro-bubbles on their free surface. Since the DAF system was first used in the drinking water treatment in the 1960s, it has been recognized as an effective treatment for the water purification process. Most previous works laid great emphasis on the internal flow behaviors of fluid to improve the purification efficiency of the DAF system. Nevertheless, the practical implementation with a pilot plant indeed revealed some technical incompleteness for the DAF system. To circumvent for the technical incompleteness, numerical simulation based on computational fluid dynamics (CFD) has been carried out to understand the in-depth knowledge on internal flow phenomena in the DAF system. However, the standard k-ε turbulence model has been conventionally used in the most studies without any proper consideration process. Accordingly, the objectives of this study were to investigate the major effects on the internal flow behaviors for an efficient numerical simulation of DAF when a different turbulence model and micro-bubble parameters are used. As a result, the present study found that the standard k-ε model would be not proper for the internal flow simulation of the DAF process and a careful consideration would be required for a more accurate prediction. In addition, the present study examined a desirable internal flow pattern with various operating conditions of the micro-bubble. Consequently, the main findings of this study are expected to provide realistic information to related researchers for designing the DAF system with the optimal operating parameters.

Despite the mercury (Hg) control measures adopted by the international community, Hg still poses a significant risk to ecosystem and human health. This is primarily due to the ability of atmospheric Hg to travel intercontinentally and contaminating terrestrial and aquatic environments far from its natural and anthropogenic point sources. The issue of Hg pollution is further complicated by its unique physicochemical characteristics, most noticeably its multiple chemical forms that vary in their toxicity and environmental mobility. This meant that most of the risk evaluation protocols developed for other metal(loid)s are not suitable for Hg. Soil is a major reservoir of Hg and a key player in its global cycle. To fully assess the risks of soil Hg it is essential to estimate its bioavailability and/or availability which are closely linked to its toxicity. However, the accurate determination of the (bio)-available pools of Hg in soils is problematic, because the terms ‘bioavailable’ and ‘available’ are ill-defined. In particular, the term ‘bioavailable pool’, representing the fraction of Hg that is accessible to living organisms, has been consistently misused by interchanging with other intrinsically different terms e.g. mobile, labile, reactive and soluble pools. A wide array of physical, chemical, biological and isotopic exchange methods were developed to estimate the (bio)-available pools of Hg in soil in an attempt to offer a plausible assessment of its risks. Unfortunately, many of these methods do not mirror the (bio)-available pools of soil Hg and suffer from technical drawbacks. In this review, we discuss advantages and disadvantages of methods that are currently applied to quantify the (bio)-availability of Hg in soils. We recommended the most feasible methods and give suggestions how to improve the determination of (bio)-available Hg in soils.

A tropical soil Actinomycete, Gordonia amicalis HS-11, has been previously demonstrated to degrade unsaturated and saturated hydrocarbons (squalene and n-hexadecane, respectively) in an effective manner. In present study, G. amicalis HS-11 degraded 92.85 ± 3.42% of the provided diesel oil [1% (v/v)] after 16 days of aerobic incubation. The effect of different culture conditions such as carbon source, nitrogen source, pH, temperature, and aeration on degradation was studied. During degradation, this Actinomycete synthesized surface active compounds (SACs) in an extracellular manner that brought about a reduction in surface tension from 69 ± 2.1 to 30 ± 1.1 mN m⁻¹ after 16 days. The morphology of cells grown on diesel was monitored by using a Field Emission Scanning Electron Microscope. Diesel-grown cells were longer and clumped with smooth surfaces, possibly due to the secretion of SACs. The interaction between the cells and diesel oil was studied by Confocal Laser Scanning Microscope. Some cells were adherent on small diesel droplets and others were present in the non-attached form thus confirming the emulsification ability of this organism. The fatty acid profiles of the organism grown on diesel oil for 48 h were different from those on Luria Bertani Broth. The genotoxicity and cytotoxicity of diesel oil before and after degradation were determined. Cytogenetic parameters such as mitotic index (MI); mitosis distribution and chromosomal aberration (type and frequency) were assessed. Oxidative stress was evaluated by measuring levels of catalase, superoxide dismutase and concentration of malondialdehyde. On the basis of these studies it was deduced that the degradation metabolites were relatively non-toxic.

The 2011 spill at platforms B and C of the Penglai 19-3 oil field in the Bohai Sea has been the worst oil spill accident in China. To assess long-term effects, a comprehensive monitoring program of chemical and biological variables (within a 2.2 km radius of the spill site) was conducted five years after the spill. Comparison of nutrient, Chl-a and oil concentrations in seawater, TOC, PAHs, heavy metals concentrations within the sediments, and the abundance and biomass of macrobenthic organisms to values obtained before and after the oil spill in previous studies indicate habitat recovery has occurred within the Bohai Sea following the episodic oil release. Observed elevated oil concentration in the water column and higher concentrations of two heavy metals, five PAHs, TOC, TOC/TN and lower values of δ¹³C, together with a reduction in macrobenthic biomass in near-field samples, suggest the influence of contaminants from chronic releases of oil and operational waste discharges within the vicinity of the oil platforms.

The ecotoxicology of surfactants is attracting wide attention due to the rapidly expanding global application. As interspecific relationships play one of the central roles in structuring biological communities, it is necessary to take it into risk assessments on surfactants. With this aim, our study investigated the interference of three common surfactants on the inducible defense of a freshwater phytoplankton Scenedesmus obliquus. Nonlethal environmentally relevant concentrations (10 and 100 μg L⁻¹) of several surfactants were set up. Results showed that growth and photosynthetic efficiency of Scenedesmus were inhibited during first 96 h, but recovered in the later stage. Surfactants interfered inducible defense of Scenedesmus against Daphnia grazing, and the interference was related to chemical characteristics of surfactants. The anionic surfactant sodium dodecyl sulfate (SDS) enhanced the colony formation even without grazing cues, whereas fewer defensive colonies were formed under the effects of cationic surfactant benzalkonium bromide (BZK) and nonionic surfactant polyoxyethylene (40) nonylphenol ether (NPE). These findings highlighted the sensitivity of grazer-induced morphological defense of Scenedesmus to surfactants even at nonlethal concentrations, which potentially affects the energy and information flow between trophic levels. This study appeals for more attention to take interspecific relationships into consideration in assessing the potential ecological risk of pollutants.

Oxygenated volatile organic compounds (OVOCs) are critical precursors of atmospheric ozone (O₃) and secondary organic aerosols (SOA). Although China is experiencing increasing O₃ pollution from north to south, understanding the major sources of OVOCs in this region is still limited due to their active photochemical behaviors. In this study, five critical OVOCs at a northern urban site (Beijing) and a southern urban site (Shenzhen) were monitored in summer using proton transfer reaction-mass spectrometry (PTR-MS). The mean total concentration of VOCs measured in Beijing (39.4 ppb) was much higher than that measured in Shenzhen (16.7 ppb), with methanol and formaldehyde being the most abundant in concentration at both sites. The source apportionment of daytime OVOCs was conducted effectively using a photochemical age-based parameterization method. Biogenic and anthropogenic secondary sources were the main sources of formaldehyde, acetaldehyde, and acetone at both sites, with a total contribution of 46–82%; acetone also had a large regional-scale background contribution (36–38%); methanol and methyl ethyl ketone (MEK) were mainly derived from anthropogenic primary sources (35–55%) at both sites. In addition, the regional background levels of OVOCs measured in North China were shown to be much higher than those measured in South China. The calculation of the total O₃ formation potential (OFP) of OVOCs highlights the comparable contributions from anthropogenic and biogenic sources in both Beijing and Shenzhen, indicating the important role of biogenic OVOC sources even in polluted environments. Since biogenic sources are already important but uncontrollable, anthropogenic emissions in China need to be restricted even more critically in the future.

Via the thermal sintering, a nanocrystalline IrO₂ coating was formed on the Ti substrate to successfully prepare a Ti/IrO₂ electrode. Based on the electrochemical analysis, the prepared Ti/IrO₂ electrode was found to have powerful oxidation effect on the organics in the TNT red water, where the nitro compound was oxidized through an irreversible electrochemical process at 0.6 V vs. SCE. According to the analysis of the nitro compound content, the UV–vis spectra, and the FTIR spectra of 2,4,6-trinitrotoluene (TNT) red water with electrolytic periods, the degradation mechanism of the dinitrotoluene sulfonate (DNTS) was developed. And the intermediates were characterized by UPLC-HRMS. The DNTS mainly occurred one electron transfer reaction on the Ti/IrO₂ electrode. At the early stage of the electrolysis, the polymerization of DNTS was mainly dominated. The generated polymer did not form a polymer film on the electrode surface, but instead it promoted a further reduction. After electrolyzing for 30 h, all NO₂ function group in the TNT red water was degraded completely.