The mechanisms of soot’s photochemistry are still unclear, especially, how the microstructure and composition of soot influence its photoactivity. In the current study, we started with the exploration of the microstructure of soot particles and gained new insights. The elemental-carbon fraction of soot (E-soot), considered the core component of soot and can reflect the intrinsic characteristics of soot, was extracted by organic solvents and characterized in terms of structure and chemical reactivity. The intrinsic structure of E-soot was found to be more analogous to reduced graphene oxide than to graphene, in terms of containing similar levels of defective sites such as oxygen-containing functional groups and environmentally persistent free radicals, as well as exhibiting similar optoelectronic performance. The generation of reactive oxygen species via an electron transfer pathway under visible light suggests that reduced graphene oxide-like E-soot can serve as a potential carbo-photocatalyst, which facilitates elucidating the mechanism of E-soot’s role during soot’s photochemical aging. Our study reveals the intrinsic structure of soot and its role in photo-triggered reactive oxygen species production, which is vital for atmospheric and health effects.

Sludge is an inevitable by-product of municipal wastewater treatment processes, and its high moisture content poses a major challenge for its subsequent treatment and disposal. Previous studies have explored the effects of applying modified corn-core powder (MCCP) on dewatering sludge. Here, we characterized the effects of applying both MCCP and sludge-based biochar (SBB) on dewatering sludge. Analysis of the anti-shear ability of SBB revealed that SBB was a skeleton builder with high compressive strength, demonstrating that SBB could maintain the permeability of sludge under high-pressure filtration processes and facilitate the flow of bound water. Dissipative particle dynamics (DPD) was used to simulated the sludge flocculating process and verify the feasibility of the experiment. As the simulation progressed, the reaction in the sludge network reached equilibrium and the simulated structure of the sludge became loose. The dewatering performance and physicochemical properties of the treated sludge were studied to further characterize the effect of this combined technology. Compared with MCCP-sludge, MCCP&SBB-sludge, which was treated by 20% DS (mass of dry solids in sludge) of SBB and 20% DS of MCCP, achieved superior dewaterability. This combined method reduced the specific resistance of filtration by 76% and enlarged the net sludge solids yield by 138%. Further study of the properties of MCCP&SBB-sludge revealed a loose structure that resembled the structure recovered by the simulation, suggesting that the DPD simulation method simulated the sludge flocculating process successfully. Therefore, the combined application of MCCP and SBB was superior for sludge dewatering because of the synergistic effects of MCCP and SBB.

Bisphenol A (BPA) is a widely concerned endocrine disrupting chemical and hard to be removed through conventional wastewater treatment processes. In this study, we developed a TiO2 decorated titanate nanotubes composite (TiO2/TNTs) and used for photocatalytic degradation of BPA. TEM and XRD analysis show that the TiO2/TNTs is a nano-composite of anatase and titanate, with anatase acting as the primary photocatalytic site and titanate as the skeleton. TiO2/TNTs exhibited excellent photocatalytic reactivity and its easy-settling property leaded to good reusability. After 5 reuse cycles, TiO2/TNTs also could photo-degrade 91.2% of BPA with a high rate constant (k1) of 0.039 min⁻¹, which was much better than TiO2 and TNTs. Higher pH facilitated photocatalysis due to more reactive oxygen species produced and less material aggregation. The presence of NaCl and CaCl2 showed negligible effects on BPA degradation, but NaHCO3 caused an inhibition effect resulting from consumption of ·OH. Humic acid inhibited degradation mainly due to blockage of the active sites of TiO2/TNTs. Degradation pathway was well interpreted through theoretical calculation. Hydroxyl radical played the dominate role in BPA photodegradation, and the atoms of BPA with high Fukui index based on density-functional theory (DFT) calculation are the radical easy-attacking (f⁰) sites. Considering the good photocatalytic reactivity, reusability, stability and settle property, TiO2/TNTs promises to be an efficient alternative for removal of organic compounds from wastewaters.

Swift degradation of the coral reef ecosystems urges the need to identify the reef decline drivers. Due to their widespread use, bioaccumulative and toxic characteristics, chlorinated organic compounds, such as chlorinated paraffins (CPs), are regarded as specific pollutants of concern. Yet little is known about the occurrence of CPs in the coral reef ecosystems. This study focuses on the short-chain chlorinated paraffins (SCCPs) and medium-chain chlorinated paraffins (MCCPs). Their distribution and congener pattern were investigated in the water-SPM-sediment system and in the corals of the Larak coral reef for the first time. Chlorinated paraffins were detected in all the coral species. Their total loadings ranged from 42.1 to 178 ng g⁻¹ dw in coral tissue, from 6.0 to 144 ng g⁻¹dw in the skeleton, and from 55.0 to 240 ng g⁻¹dw in zooxanthellae. Soft corals were found to accumulate more CPs than Scleractinian corals. Zooxanthellae and mucus accumulated more CPs than tissue and skeleton. In most cases, congener group patterns were dominated by C₁₃ (for SCCPs) and C₁₇ (MCCPs) groups, respectively. The congener patterns of CPs altered to some extent between mucus and the remaining coral compartments. High loadings of CPs were detected in the skeleton of the bleached corals. Moreover, a significant negative correlation between the levels of CPs and the symbiodinium density was observed.

Fish farming in coastal areas has become an important source of food to support the world’s increasing population. However, intensive and unregulated mariculture activities have contributed to changing seawater carbonate chemistry through the production of high levels of respiratory CO₂. This additional CO₂, i.e. in addition to atmospheric inputs, intensifies the effects of global ocean acidification resulting in localized extreme low pH levels. Marine calcifying macroalgae are susceptible to such changes due to their CaCO₃ skeleton. Their physiological response to CO₂-driven acidification is dependent on their carbon physiology. In this study, we used the pH drift experiment to determine the capability of 9 calcifying macroalgae to use one or more inorganic carbon (Cᵢ) species. From the 9 species, we selected the rhodolith Sporolithon sp. as a model organism to investigate the long-term effects of extreme low pH on the physiology and biochemistry of calcifying macroalgae. Samples were incubated under two pH treatments (pH 7.9 = ambient and pH 7.5 = extreme acidification) in a temperature-controlled (26 ± 0.02 °C) room provided with saturating light intensity (98.3 ± 2.50 μmol photons m⁻² s⁻¹). After the experimental treatment period (40 d), growth rate, calcification rate, nutrient uptake rate, organic content, skeletal CO₃⁻², pigments, and tissue C, N and P of Sporolithon samples were compared. The pH drift experiment revealed species-specific Cᵢ use mechanisms, even between congenerics, among tropical calcifying macroalgae. Furthermore, long-term extreme low pH significantly reduced the growth rate, calcification rate and skeletal CO₃⁻² content by 79%, 66% and 18%, respectively. On the other hand, nutrient uptake rates, organic matter, pigments and tissue C, N and P were not affected by the low pH treatments. Our results suggest that the rhodolith Sporolithon sp. is susceptible to the negative effects of extreme low pH resulting from intensive mariculture-driven coastal acidification.

In this study, coral soft tissue, skeleton and zooxanthellae, as well as their ambient sediment and seawater were analyzed for polycyclic aromatic hydrocarbons (PAHs) with a special focus on perylene. Samples were collected from two different environments: the Kharg Island, which is affected by numerous anthropogenic stressors and Larak Island, which is mainly used for recreational and fishing activities and is characterized by dense vegetation. The heaviest loadings of PAHs were observed on Kharg Island, yet higher concentrations of perylene were detected on Larak Island and it was identified as the prevailing compound in this area. Pyrogenic perylene sources were prevailing on Kharg Island, whereas the perylene on Larak Island was determined to be of natural origin. After analyzing the biological samples, higher perylene concentrations were observed in zooxanthellae than in tissue and skeleton. The lowest and the highest perylene loadings were found in the tissue and skeleton of Platygyra daedalea and Porites lutea, respectively. This applies to both reefs. We found that perylene distribution in the corals and their ambient environment follows an irregular pattern, demonstrating remarkable effects from the local inputs. The lipid content in the coral tissue and the location of the coral colony were deduced to be the main factors affecting perylene distribution in corals. On Larak Island, a significant correlation between perylene loadings in sediment and corals was observed. On Kharg Island, a strong interaction between the water column and the corals was detected. The symbiotic relationship between the corals and zooxanthellae might play the most significant role in bioconcentration and bioaccumulation of perylene. Due to the insolubility of PAHs, they could be transferred through a food chain to zooxanthellae and eventually deposited in the coral bodies.

The role of ecophysiology in mediating marine biological pollution is poorly known. Here we explore how physiological plasticity to environmental stress can explain and predict the context-dependencies of invasive species impacts. We use the case of two sympatric skeleton shrimps, the invader Caprella scaura and its congener C. equilibra, which is currently replaced by the former on the South European coast. We compare their physiological responses to hyposalinity stress under suboptimal low and high temperature, while inferring on hypoxia tolerance. We use an energy-redox approach, analyzing mortality rate, the energetic balance and the consequent effects on the oxidative homeostasis. We found that decreased seawater salinity and/or oxygen levels can weaken biotic resistance, especially in females of C. equilibra, leading to periods of heightened vulnerability to invasion. Our approach provides mechanistic insights towards understanding the factors promoting invader impacts, highlighting the potential of ecophysiology for improving invasive species management.

Biological impairments have been documented on reefs at two national parks in St. Croix, USVI. Although several water quality parameters have been out of compliance with USVI criteria, whether these parameters or other pollutants are responsible for coral health impacts is unknown. Trace elements quantified in sediment showed four sites at SARI, which is closer than BUIS to settlements and land-derived anthropogenic outflows, had Cu mass fractions above sediment quality guidelines for invertebrate toxicity. Trace elements were also analyzed in the skeleton of threatened elkhorn coral, Acropora palmata, to evaluate potential exposure. Heavy metals (Pb, Zn) were significantly greater in coral skeleton at SARI than BUIS. Cu, Pb, and Zn may be impacting coral health in these parks. Potential anthropogenic sources of these metals were revealed by the coral tissue stable isotope levels (δ¹³C and δ¹⁵N). These findings provide a framework for determining heavy metal impacts on these invaluable reefs.

We report the ratios of minor (K/Ca, Na/Ca, P/Ca, S/Ca) and trace elements (Al/Ca, Ba/Ca, Fe/Ca, Mn/Ca and Zn/Ca) in skeletons of five Arctic echinoderm species representing three classes: Asteroidea, Ophiuroidea, Crinoidea. We found that skeletons of Arctic echinoderms show a unique, species-specific trace element composition that may suggest that incorporation of elements into the skeleton is biologically controlled by the organism. On the other hand, the concentration of some minor elements in skeletal parts exhibit patterns that are consistent with elemental concentrations in seawater, indicating that formation of echinoderm skeletons is environmentally controlled. Seawater is the main source of ions and compounds needed for skeletal formation and maintaining similar concentrations most likely reduces the biological cost related to selective uptake of ions. Additionally, Al, Ba, Fe, Mg and Mn showed station specific variation in elemental concentration which again suggests that accumulation of metals can be shaped by environmental concentrations.

For centuries, Bermuda has been challenged with wastewater management for the protection of human and environmental health. By quantifying the δ15N of the common sea fan Gorgonia ventalina sampled from 30 sites throughout Bermuda we show that sewage-derived nitrogen is detectable on nearshore coral reefs and declines across the lagoon to the outer rim. We also sampled gorgonians from two museum collections representing a 50y time-series (1958–2008). These samples revealed an increase in δ15N of >4.0‰ until the mid-1970s, after which δ15N values slowly declined by ~2.0‰. A δ15N chronology from a gorgonian skeleton exhibited a similar decline over the last 30–40years of approximately 0.6‰. We conclude that policies have been effective in reducing sewage impacts to Bermudian reefs. However, significant sources of sewage pollution persist and are likely have a strong impact on harbor and nearshore coral communities and human health.