Predicted global figures for plastic debris accumulation in the ocean surface layer range on the order of hundreds of thousands of metric tons, representing only a few percent of estimated annual ...emissions into the marine environment. The current accepted explanation for this difference is that positively buoyant macroplastic objects do not persist on the ocean surface. Subject to degradation into microplastics, the major part of the mass is predicted to have settled below the surface. However, we argue that such a simple emission-degradation model cannot explain the occurrence of decades-old objects collected by oceanic expeditions. We show that debris circulation dynamics in coastal environments may be a better explanation for this difference. The results presented here suggest that there is a significant time interval, on the order of several years to decades, between terrestrial emissions and representative accumulation in offshore waters. Importantly, our results also indicate that the current generation of secondary microplastics in the global ocean is mostly a result of the degradation of objects produced in the 1990s and earlier. Finally, we propose a series of future emission scenarios until 2050, discussing the necessity to rapidly reduce emissions and actively remove waste accumulated in the environment to mitigate further microplastic contamination in the global ocean.
River plastic emissions to the world's oceans Lebreton, Laurent C M; van der Zwet, Joost; Damsteeg, Jan-Willem ...
Nature communications,
06/2017, Letnik:
8, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Plastics in the marine environment have become a major concern because of their persistence at sea, and adverse consequences to marine life and potentially human health. Implementing mitigation ...strategies requires an understanding and quantification of marine plastic sources, taking spatial and temporal variability into account. Here we present a global model of plastic inputs from rivers into oceans based on waste management, population density and hydrological information. Our model is calibrated against measurements available in the literature. We estimate that between 1.15 and 2.41 million tonnes of plastic waste currently enters the ocean every year from rivers, with over 74% of emissions occurring between May and October. The top 20 polluting rivers, mostly located in Asia, account for 67% of the global total. The findings of this study provide baseline data for ocean plastic mass balance exercises, and assist in prioritizing future plastic debris monitoring and mitigation strategies.
Here we report concentrations of pollutants in floating plastics from the North Pacific accumulation zone (NPAC). We compared chemical concentrations in plastics of different types and sizes, ...assessed ocean plastic potential risks using sediment quality criteria, and discussed the implications of our findings for bioaccumulation. Our results suggest that at least a fraction of the NPAC plastics is not in equilibrium with the surrounding seawater. For instance, “hard plastic” samples had significantly higher PBDE concentrations than “nets and ropes” samples, and 29% of them had PBDE composition similar to a widely used flame-retardant mixture. Our findings indicate that NPAC plastics may pose a chemical risk to organisms as 84% of the samples had at least one chemical exceeding sediment threshold effect levels. Furthermore, our surface trawls collected more plastic than biomass (180 times on average), indicating that some NPAC organisms feeding upon floating particles may have plastic as a major component of their diets. If gradients for pollutant transfer from NPAC plastic to predators exist (as indicated by our fugacity ratio calculations), plastics may play a role in transferring chemicals to certain marine organisms.
Most studies on buoyant microplastics in the marine environment rely on sea surface sampling. Consequently, microplastic amounts can be underestimated, as turbulence leads to vertical mixing. Models ...that correct for vertical mixing are based on limited data. In this study we report measurements of the depth profile of buoyant microplastics in the North Atlantic subtropical gyre, from 0 to 5 m depth. Microplastics were separated into size classes (0.5-1.5 and 1.5-5.0 mm) and types ('fragments' and 'lines'), and associated with a sea state. Microplastic concentrations decreased exponentially with depth, with both sea state and particle properties affecting the steepness of the decrease. Concentrations approached zero within 5 m depth, indicating that most buoyant microplastics are present on or near the surface. Plastic rise velocities were also measured, and were found to differ significantly for different sizes and shapes. Our results suggest that (1) surface samplers such as manta trawls underestimate total buoyant microplastic amounts by a factor of 1.04-30.0 and (2) estimations of depth-integrated buoyant plastic concentrations should be done across different particle sizes and types. Our findings can assist with improving buoyant ocean plastic vertical mixing models, mass balance exercises, impact assessments and mitigation strategies.
Land-based macroplastic is considered one of the major sources of marine plastic debris. However, estimations of plastic emission from rivers into the oceans remain scarce and uncertain, mainly due ...to a severe lack of standardized observations. To properly assess global plastic fluxes, detailed information on spatiotemporal variation in river plastic quantities and composition are urgently needed. In this paper, we present a new methodology to characterize riverine macroplastic dynamics. The proposed methodology was applied to estimate the plastic emission from the Saigon River, Vietnam. During a two-week period, hourly cross-sectional profiles of plastic transport were made across the river width. Simultaneously, sub-hourly samples were taken to determine the weight, size and composition of riverine macroplastics (>5cm). Finally, extrapolation of the observations based on available hydrological data yielded new estimates of daily, monthly and annual macroplastic emission into the ocean. Our results suggest that plastic emissions from the Saigon River are up to 4 times higher than previously estimated. Importantly, our flexible methodology can be adapted to local hydrological circumstances and data availability, thus enabling a consistent characterization of macroplastic dynamics in rivers worldwide. Such data will provide crucial knowledge for the optimization of future mediation and recycling efforts.
Here, we present a proof-of-concept on remote sensing of ocean plastics using airborne shortwave infrared (SWIR) imagery. We captured red, green, and blue (RGB) and hyperspectral SWIR imagery with ...equipment mounted on a C-130 aircraft surveying the “Great Pacific Garbage Patch” at a height of 400 m and a speed of 140 knots. We recorded the position, size, color, and type (container, float, ghost net, rope, and unknown) of every plastic piece identified in the RGB mosaics. We then selected the top 30 largest items within each of our plastic type categories (0.6–6.8 m in length) to investigate SWIR spectral information obtained with a SASI-600 imager (950–2450 nm). Our analyses revealed unique SWIR spectral features common to plastics. The SWIR spectra obtained (N = 118 items) were quite similar both in magnitude and shape. Nonetheless, some spectral variability was observed, likely influenced by differences in the object optical properties, the level of water submersion, and an intervening atmosphere. Our simulations confirmed that the ∼1215 and ∼1732 nm absorption features have potential applications in detecting ocean plastics from spectral information. We explored the potential of SWIR remote sensing technology for detecting and quantifying ocean plastics, thus provide relevant information to those developing better monitoring solutions for ocean plastic pollution.
The ubiquity of plastics in oceans worldwide raises concerns about their ecological implications. Suspended microplastics (<5 mm) can be ingested by a wide range of marine organisms and may ...accumulate up the food web along with associated chemicals. Additionally, plastics provide a stable substrate to a wide range of organisms and, owing to their widespread dispersal, may function as vectors for harmful and invasive species. Despite the growing application of molecular techniques to study ocean microplastic colonizers, to date there is no comparative study on DNA extraction methods for ocean plastic biofilms. The present study aims to fill this gap by comparing DNA yield, amplification efficiency, costs and processing time of different DNA extraction techniques applied to oceanic microplastics. DNA was extracted with five methods (four extraction kits, and standard phenol:chloroform purification) using two mechanical lysis techniques (bead beating and cryogenic grinding with liquid nitrogen) applied to three plastic quantities (1, 15, and 50 fragments per extraction) and size classes (0.05-0.15 and 0.15-0.5 mm). All methods resulted in DNA suitable for downstream applications and were successfully amplified. Overall, the Qiagen Puregene Tissue kit yielded relatively high DNA concentrations for most sizes and amounts of plastics at relatively low costs and short processing time. This study provides a detailed evaluation of DNA extraction methods from ocean plastics, and may assist future research using molecular techniques to study ocean plastic biofilms.
Here, we report cetacean sightings made within a major oceanic accumulation zone for plastics, often referred to as the ‘Great Pacific Garbage Patch’ (GPGP). These cetacean records occurred in ...October 2016 and were made by sensors and trained observers aboard a Hercules C-130 aircraft surveying the GPGP at 400 m height and 140 knots speed. Four sperm whales (including a mother and calf pair), three beaked whales, two baleen whales, and at least five other cetaceans were observed. Many surface drifting plastics were also detected, including fishing nets, ropes, floats and fragmented debris. Some of these objects were close to the sighted mammals, posing entanglement and ingestion risks to animals using the GPGP as a migration corridor or core habitat. Our study demonstrates the potential exposure of several cetacean species to the high levels of plastic pollution in the area. Further research is required to evaluate the potential effects of the GPGP on marine mammal populations inhabiting the North Pacific.
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