PURPOSE OF REVIEW: Black carbon (BC) deposition in snow can trigger a significant reduction in snow albedo and accelerate snowmelt. As a result, numerous snow surveys have performed to measure BC concentrations in snow across the polar regions, the Tibetan Plateau, and other high-mountain regions. This review is aimed to synthesize the current progresses of the potential feedbacks of snow albedo and its sensitivity by BC in snow across the Northern Hemisphere. RECENT FINDINGS: Generally, BC concentrations in snow are highest in the mid-latitudes of Northern China and North America, and reduce toward higher latitudes (e.g., Greenland and the rest of the Arctic). We found that the snow albedo reduction attributed to low BC contamination (< 20 ng g⁻¹) in older snow (200 μm snow grains) is 1.2%, compared with 0.6% in fresh snow (50 μm snow grains). Non-spherical snow grains exhibit a significantly lower snow albedo reduction (2–6%) due to BC contamination compared with spherical snow grains with 100–500 ng g⁻¹ of BC in the snowpack. Snow–BC–internal mixing reduces the snow albedo (< 10%) more substantially than does external mixing in the case of 50–200 μm snow grains and a given BC concentration (< 2000 ng g⁻¹). Besides the BC and other light-absorbing particles (LAPs), the mixing state of LAPs in snow, snow grain properties, and the scavenging\washing effects are also major challenges in determining snow albedo, which need to be further investigated on a global scale.

Black carbon (BC) exerts profound impacts on air quality and climate because of its high-absorption cross section over a broad band of solar spectrum. Non-BC materials coated on BC could alter the mixing state of BC particles and can considerably enhance its mass absorption coefficient. Quantification of this absorption enhancement remains a challenge due to incomplete understanding of the complex physical and chemical properties related to mixing states. In this paper, we summarize the recent progress in measurement and modeling studies on the BC mixing state and their effects on optical properties. Laboratory and field-based observations have shown that the transformation of a mixing state from a highly fractal nature to a more compact shape exhibits a decrease in electric mobility diameter but an increase in fractal dimension and effective density. Meanwhile, the transition behavior is also obviously influenced by emission source which can determine the components of BC mixtures. Based on the empirically determined parameters, accurate numerical modeling shows great capability on calculating BC optical properties. However, considering the significant uncertainties related to BC microphysical properties, proper parameterization considering realistic BC aggregates and coating fraction can help to understand the progress from an externally to internally mixed state.

Aquatic biota including fish, shrimp and bivalves were collected from the Yellow River Delta (YRD), China to investigate the levels, composition profile and dietary exposure of polybrominated diphenyl ethers (PBDEs), decabromodiphenyl ethane (DBDPE) and dechlorane plus (DP). The concentrations of PBDEs, DBDPE and DP in the organisms ranged from 5.3 to 149, not detected (nd) - 49, and 0.5–29 ng/g lipid weight, respectively. Higher levels of PBDEs and DP were found in mullet (Liza haematocheila).PBDEs were the major pollutants and BDE 209 was the predominant congener of PBDEs suggesting the great production and application of deca-BDE in YRD. The average fₐₙₜᵢ values for different species were similar to or a little lower than that of the commercial DP, suggesting syn-DP might be selectively accumulated by the organisms. The estimated daily intake values of HFRs suggested consuming fish was the main pathway for the exposure of halogenated flame retardants.

A comprehensive evaluation system and model of Coastal Wetland Ecological Vulnerability (CWEV) was constructed and applied to reveal spatial heterogeneity of the ecological vulnerability of the Yellow River Delta Wetland (YRDW). The results showed that the score of the ecological vulnerability (EVS) of the YRDW was 0.49, which was generally at a medium vulnerability level. The wetland area of high vulnerability was up to 943km², accounting for 35.2% of the total area, followed by the medium vulnerable area with an area of 750km², accounting for 28.1% of the total area. From the coastline perpendicularly to the land, the “seaward” gradient effect gradually decreased, the vulnerability-increasing “hydrologic connectivity” effect increased with the distance from the river channel, and the “land source influence” effect gradually decayed along with the vulnerability of population and economy gathering areas.

Few systematic and scientific assessments have been conducted on marine environmental quality in the coastal waters of Macao, a major city in the Pearl River Delta, China. In this study, we investigated the spatial distribution of trace metals (TMs) and comprehensive contamination indicators of marine water in Macao and evaluated their ecological risks. The total amount of typical TMs (∑TMs) in surface water ranged from 2.71 μg/L to 201 μg/L. ∑TMs (Hg, As, and Cd) in sediments ranged from 0.34 mg/kg to 54.8 mg/kg. TM contamination in surface water was influenced by spatial position and tidal current direction. The spatial distribution and correlation analysis of TMs and comprehensive contamination indicators were assessed, and ecological risk assessment indicated that the surface water and sediments in coastal waters of Macao are of relatively good quality, although high sulfide levels could be detected in surface water.

Eutrophication is a major threat to world's coral reefs. Here, we mapped the distribution of the anthropogenic nitrogen footprint around Nouméa, a coastal city surrounded by 15,743 km² of UNESCO listed reefs. We measured the δ¹⁵N signature of 348 long-lived benthic bivalves from 12 species at 27 sites and interpolated these to generate a δ¹⁵N isoscape. We evaluated the influence of water residence times on nitrogen enrichment and predicted an eutrophication risk at the UNESCO core area. Nitrogen isoscapes revealed a strong spatial gradient (4.3 to 11.7‰) from the outer lagoon to three highly exposed bays of Nouméa. Several protected reefs would benefit from an improved management of wastewater outputs, while one bay in the UNESCO core area may suffer a high eutrophication risk in the future. Our study reinforces the usefulness of using benthic animals to characterize the anthropogenic N-footprint and provide a necessary baseline for both ecologists and policy makers.

There is an increasing awareness of microplastics within the global problem of marine plastic pollution. In 2018, small plastic pellets or “nurdles” were observed on the beaches of Corpus Christi, Texas. A citizen science project, “Nurdle Patrol,” was established by the Mission-Aransas National Estuarine Research Reserve to monitor the presence of nurdles, with volunteer interest enabling this project to expand across the Gulf of Mexico region. This case study describes the sampling methodology, the policy framework, and initial quantitative data from the citizen science project on nurdle distribution along the Gulf coast. A total of 2042 Nurdle Patrol surveys have been conducted by 744 citizen scientists covering shorelines from Mahahual, Mexico to Fort Jefferson, Florida. All 20 of the highest standardized nurdle counts were recorded at sites in Texas. Results can inform decision-maker response across regulatory scales and further research on nurdle pollution.

Few investigations of iron speciation exist in intertidal conditions with little attention given to understanding the geochemical behavior of Fe³⁺–Fe²⁺ and its biogeochemical processes. Here, one sediment core was collected in Yunxiao mangrove forests, Zhangjiang estuary, China and iron mineralogy was determined by magnetic methods and Mössbauer spectroscopy. Changes in magnetic susceptibility, susceptibility of anhysteretic remanent magnetization, and saturation isothermal remanent magnetization were linked to changes of pseudo-single domain soft coercive components with minor antiferromagnetic fractions and the presence of minimal concentrations of superparamagnetic particles was confirmed by the no frequency dependent of AC magnetization. A positive correlation between L-ratio and hard isothermal remanent magnetization is congruent with the distribution of high-coercivity antiferromagnetic minerals. At 295 K, the Mössbauer spectrum of specimens was well fitted with a single magnetic sextet, hematite and two magnetic doublets, paramagnetic Fe²⁺ and paramagnetic Fe³⁺. The usefulness of magnetic data and Mössbauer spectroscopy could offer valuable analytical tools for tracking changes of iron speciation and phase in the intertidal conditions.

Monitoring Floating Marine Macro Litter (FMML) is a global priority, stressed within international programs, and regulated for the European Seas by the Marine Strategy Framework Directive. Although some well-defined common protocols exist for the assessment of beach litter and ingested litter, methodologies for FMML monitoring still vary, leading to some inconsistent results and hampering the global assessment of this threat. Within the MEDSEALITTER project (2016–2019), field experiments were implemented to define optimal monitoring parameters for FMML visual monitoring at different spatial scales, by assessing the influence of platform speed, strip width, observers experience, weather conditions, and litter size on its detectability. Along with the results of these experiments, we present the FMML density ranges detected across the over 20,000 km surveyed, highlighting a decreasing gradient from river mouths to coastal areas and the open sea, and providing a valuable contribution to the assessment of FMML in the Mediterranean Sea.

A preliminary report on the abundance of microplastic in the coastal waters in the depth zone 5 to 20 m in the surface waters, sediment and in selected fishes occurring off Kochi, India is presented. Spatial and temporal variation in microplastic abundance was observed with higher abundance in surface water indicating threats to pelagic ecosystem. The relative concentration of microplastic was highest during monsoon season. The major microplastics were fragments of 1-5 mm in white and blue colours. Gut content analysis of 16 species (653 individuals) comprising pelagic (8 species) and demersal (8 species) indicated occurrence (4.6%) of microplastics (fragment>filament>pellet) of size 0.27mm to 3.2 mm in Sardinella longiceps, S. gibbosa, Stolephorus indicus Rastrelliger kanagurta and Cyanoglossus macrostomus. Raman spectroscopy indicated that Polyethylene (PE) and Polypropylene (PP) were the polymer types of microplastics from the fish gut.