Export of Plastic Debris by Rivers into the Sea

Schmidt, Christian; Krauth, Tobias; Wagner, Stephan

doi:10.1021/acs.est.7b02368

Cited by 1,026 publications

(646 citation statements)

References 36 publications

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“…It is not yet clear why this accumulation is so stable. Third, large amounts of plastics are estimated to enter the northern IO (Jambeck et al, ; Lebreton et al, ; Schmidt et al, ). If these plastics do not accumulate in the subtropics (because there is no northern IO subtropical gyre and buoyant debris is unlikely to cross the equator), an important question is what does happen to these plastics.…”

Section: Discussionmentioning

confidence: 99%

Role of Indian Ocean Dynamics on Accumulation of Buoyant Debris

2019

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Buoyant marine plastic debris has become a serious problem affecting the marine environment. To fully understand the impact of this problem, it is important to understand the dynamics of buoyant debris in the ocean. Buoyant debris accumulates in “garbage patches” in each of the subtropical ocean basins because of Ekman convergence and associated downwelling at subtropical latitudes. However, the precise dynamics of the garbage patches are not well understood. This is especially true in the southern Indian Ocean (SIO), where observations are inconclusive about the existence and numerical models predict inconsistent locations of the SIO garbage patch. In addition, the oceanic and atmospheric dynamics in the SIO are very different from those in the other oceans. The aim of this paper is to determine the dynamics of the SIO garbage patch at different depths and under different transport mechanisms such as ocean surface currents, Stokes drift, and direct wind forcing. To achieve this, we use two types of ocean surface drifters as a proxy for buoyant debris. We derive transport matrices from observed drifter locations and simulate the global accumulation of buoyant debris. Our results indicate that the accumulation of buoyant debris in the SIO is much more sensitive to different transport mechanisms than in the other ocean basins. We relate this sensitivity to the unique oceanic and atmospheric dynamics of the SIO.

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Section: Discussionmentioning

confidence: 99%

Role of Indian Ocean Dynamics on Accumulation of Buoyant Debris

2019

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“…Hydrologic science and water management are increasingly driven by future challenges including global climate change and rapid urbanization, and the further necessity to actively incorporate the dynamics of human society is demonstrated by the introduction of sociohydrology science (Sivapalan, 2018;Sivapalan et al, 2012). Basin-wide water quality modeling mostly considers population as the major stressor and aggregates the total basin population loadings of pollutants without accounting for their spatial patterns (Schmidt et al, 2017;Van Drecht et al, 2009). Basin-wide water quality modeling mostly considers population as the major stressor and aggregates the total basin population loadings of pollutants without accounting for their spatial patterns (Schmidt et al, 2017;Van Drecht et al, 2009).…”

Section: Earth's Futurementioning

confidence: 99%

“…Human activities have caused substantial alterations to the Earth, affecting ecosystem patterns and processes, altering global hydrological and biogeochemical cycles, amplifying resource exploitation and environmental deterioration, and contributing to climate change (Vitousek et al, 1997). River networks can connect and facilitate the transport of pollutants between, human settlements, and terrestrial and marine environments (Schmidt et al, 2017). River networks can connect and facilitate the transport of pollutants between, human settlements, and terrestrial and marine environments (Schmidt et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Globally Universal Fractal Pattern of Human Settlements in River Networks

et al. 2018

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River networks play a key role in the spatial organization of human settlements. Both river networks and human settlements have been found to exhibit regular self-similar patterns, but little is known about the generalized spatial patterns of human settlements embedded within river networks. Here based on night light data, we find a universal fractal structure at the global scale, with both robust Hortonian scaling relationships with the extent of human settlements and statistically significant power law scaling of the power spectra of human area functions. Globally, we find consistent patterns of power law preferential downstream clustering of human settlements across all six populated continents, typically up to 40% of the maximum flow length. This downstream clustering suggests an optimum distribution of humans in large river basins for trade, transport, and natural resource utilization but with attendant implications for human impacts on rivers. Recognition of such spatial patterns helps generalize assessments of human impacts on rivers, with direct implications for management of water quality and biological diversity in river networks. Plain Language SummaryWhere do people live in relation to rivers? Human societies evolved alongside rivers, but how are modern human societies related to rivers? We conducted a global analysis to assess the linkages between river geomorphologic structure and human settlement patterns. We found globally consistent patterns of preferential downstream clustering of human settlements. Across all six populated continents, human settlements are clustered near the outlets of major river basins, with settlement density decreasing exponentially with distance upstream. This downstream clustering suggests an optimum distribution of humans in large river basins for trade, transport and resource utilization. However, there are also attendant implications for human impacts on rivers. Recognition of such spatial patterns helps generalize management of river water quantity, quality, and biological. River networks are characterized by bifurcating and hierarchical geometries with universally consistent scale-free topological features, resulting from self-organization driven by similar generating processes (Dodds & Rothman, 2000). One descriptor of such organizational structure is stream order, which describes the relative size of a stream in a tree-like river network (Horton, 1945). Generalized Horton's laws refer to scaling relationships of topologic and geometric variables (e.g., stream number, basin area, and stream FANG ET AL.

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“…This lag between the real-time environmental changes and scientific assessments based on outdated data is quite surprising, given the magnitude and pace of the environmental changes occurring across Asia. A recent report on the riverine export of 135 plastic debris illustrated alarming trends of environmental changes occurring in Asian river systems by showing that 8 of top 10 rivers exporting the highest loads of plastics to the oceans drain the rapidly urbanizing watersheds across Asia (Schmidt et al, 2017). …”

Section: 1mentioning

confidence: 99%

“…The Asia total discharge provided by Milliman and 955 Farnsworth (2011) was estimated for all rivers of Asia and Oceania, excluding Arctic rivers in Russia. Population data were taken from various sources including Schmidt et al (2017) and CIA World Factbook (https://www.cia.gov/library/publications/the-world-factbook/index.html/; last accessed on 10 January 2018). Asia total population is the population for all countries belonging to Asia and Oceania excluding Russia.…”

Section: Acknowledgements 550mentioning

confidence: 99%

Reviews and syntheses: Anthropogenic perturbations to carbon fluxes in Asian river systems: Concepts, emerging trends, and research challenges

Park¹,

Nayna²,

Begum³

et al. 2018

Preprint

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Abstract. Human activities are drastically altering water and material flows in river systems across Asia. These anthropogenic perturbations have rarely been linked to the carbon (C) fluxes of Asian rivers that may account for up to 40-20 50% of the global fluxes. The primary object of this review was to provide a conceptual framework for assessing human impacts on Asian river C fluxes, along with a latest update on anthropogenic alterations of riverine C fluxes, focusing on the impacts of water pollution and river impoundments on CO2 outgassing from the rivers draining South, Southeast, and East Asian regions that account for the largest fraction of river discharge and C exports from Asia and Oceania. Recent booms in dam construction across Asia have created a host of environmental problems; yet only a small number of studies have 25 explicitly investigated altered rates of greenhouse gas (GHG) emissions and organic C transport. There have been contrasting reports on impoundment effects: decreases in GHG emissions in the reservoirs exhibiting enhanced primary production vs. increased emissions from the flooded vegetation and soils in the early years following dam construction or from the impounded river reaches and downstream estuaries during the monsoon period. These contrasting results suggest that the rates of metabolic processes in the impounded and downstream reaches can greatly vary longitudinally over time, as 30 a combined result of diel shifts in the balance between autotrophy and heterotrophy, seasonal fluctuations between the dry and monsoon periods, and a long-term change from a leaky post-construction phase to a gradual C sink. Rapid pace of urbanization across southern and eastern Asian regions has dramatically increased municipal water withdrawal, generating annually 120.2 km 3 of wastewater in 24 countries, which comprises 38.6% of the global municipal wastewater production disproportionately affect the receiving river water, particularly downstream of rapidly expanding metropolitan areas, including eutrophication, increases in the amount and lability of organic C, and pulse emissions of CO2 and other greenhouse gases (GHGs). As reviewed for three representative rivers (the Ganges, Mekong, and Yellow River), the lower reaches of these rivers and their polluted tributaries tend to exhibit higher levels of organic C and the partial pressure of CO2 (pCO2) than the eutrophic reservoirs and less impacted upstream reaches. More field measurements of pCO2, together with accurate 40 flux calculations based on river-specific model parameters, are urgently required to provide more accurate estimates of GHG emissions from the Asian rivers that are now underrepresented in the global C budgets. Researchers working on individual river systems need to be linked to collaborative research networks to facilitate global synthesis of local field data. These synthesis efforts, combined with conceptual and mathematical models, will contribute to a better understanding of how anthropogenic perturbations in rapidly urb...

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Export of Plastic Debris by Rivers into the Sea

Cited by 1,026 publications

References 36 publications

Role of Indian Ocean Dynamics on Accumulation of Buoyant Debris

Role of Indian Ocean Dynamics on Accumulation of Buoyant Debris

Globally Universal Fractal Pattern of Human Settlements in River Networks

Reviews and syntheses: Anthropogenic perturbations to carbon fluxes in Asian river systems: Concepts, emerging trends, and research challenges

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