Research ArticleENVIRONMENTAL STUDIES

More than 1000 rivers account for 80% of global riverine plastic emissions into the ocean

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Science Advances  30 Apr 2021:
Vol. 7, no. 18, eaaz5803
DOI: 10.1126/sciadv.aaz5803
  • Fig. 1 Model framework.

    Plastic emission in a river mouth ME is computed by accumulating of MPW multiplied with the probability of waste leaking into the ocean, P(E) within a river basin. P(E) is constructed with P(M), P(R), and P(O), which contain physical processes accountable for MPW transport.

  • Fig. 2 Observations compared with modeled data for floating macrolitter emissions per river.

    Regression analysis carried out with 136 records from 67 different rivers of different sizes spread across the globe. The dataset was split into a calibration (n = 52) and a validation (n = 84) dataset. The coefficient of determination of the logarithmic regression, r2, is 0.71 for the calibration and 0.74 for the validation dataset. Symbols indicate midpoints of extrapolated measurements (MT month−1) on the x axis versus our best calibrated model prediction on the y axis. The horizontal whiskers indicate the upper and lower values reported for observational data (if published), and the vertical whiskers indicate the upper and lower value of the 68% confidence interval of model predictions. The dark blue symbols correspond to data points used for calibration, and light blue symbols represent the validation data points, while the symbol (triangle, circle, and square) indicates the continent from where the location originates. The logarithm of both the measurements and the model results is presented here. The dotted gray lines represent one-order-of-magnitude deviation from the x = y line in the middle. The Kuantan and Besos rivers (indicated in red) are outliers with more than one order of magnitude difference compared with observational results.

  • Fig. 3 Global distribution of riverine plastic emission into the ocean.

    (A) Contribution of plastic emission to the ocean (ME) (y axis) is plotted against the logarithm of the number of rivers accountable for that contribution (x axis), for previous studies and this study. (B) Distribution of 1656 rivers accountable for 80% of emissions over five discharge classes (x axis). Each river is represented by a dot. Within a discharge class, the position of a river (dot) is determined by the plastic emission (y axis). The boxes contain 50% (Q1 until Q3) of the data, and the solid horizontal line in the box is the median, while the dotted horizontal line represents the average emission per river within the discharge class.

  • Fig. 4 Global emissions of plastic into the ocean.

    (A) The geospatial distribution of plastic entering the ocean through rivers. The 1656 rivers accountable for 80% of the total influx are presented. The gray shading indicates the probability for plastic entering the ocean [P(E)] on a 10 × 10–km resolution. (B) Total emitted plastic into the ocean ME per country divided by the national generation of MPW, globally ranging between 0 and 20%. (C) Total emitted plastic into the ocean ME (MT year−1) per country.

  • Fig. 5 Probability maps.

    (A) The Meycuayan and Tullahan river basins and river network in Manila, Philippines. (B) The distance (km) from a 3 × 3–arc sec grid cell toward the nearest river. (C) The distance (km) from each grid cell to the ocean, through the river network. (D) The probability for a grid cell to emit plastic waste into the ocean P(E), Eq. 1, for a given year, ranging from 0 to 5% for areas further away from a river up to 0.8% for areas near a river and near the coast.

  • Table 1 Country statistics.

    Top 20 countries ranked according to annual plastic emission ME into the ocean, as calculated in this study. The third column contains the annual MPW generated in each country. The fourth column contains the fraction (%) of MPW reaching the ocean (calculated by dividing national ME by MPW) within a year. The fifth column contains the country averaged probability for a plastic particle to reach the ocean within a year, P(E). This sixth column contains the number of rivers accountable for national emission ME, and the last column holds the number of rivers for a country that contribute to the global 80% riverine plastic emission (emitted by 1656 rivers in total).

    CountryME (MT year−1)MPW [MT year−1]Ratio of MPW to
    ocean (ME per

    MPW)
    Average emission
    probability P(E)
    (%)
    Number of rivers
    contributing to
    100% ME
    Number of rivers
    contributing to
    80% ME
    Global1.0 × 1066.8 × 1071.5%0.4%31,9041656
    Philippines3.6 × 1054.0 × 1068.9%7.2%4820466
    India1.3 × 1051.3 × 1071.0%0.5%1169211
    Malaysia7.3 × 1048.1 × 1059.0%4.4%1070105
    China7.1 × 1041.2 × 1070.6%0.2%1309139
    Indonesia5.6 × 1048.2 × 1056.8%4.4%5540105
    Myanmar4.0 × 1049.9 × 1054.0%1.7%159671
    Brazil3.8 × 1043.3 × 1061.1%0.2%124075
    Vietnam2.8 × 1041.1 × 1062.5%1.6%49068
    Bangladesh2.5 × 1041.0 × 1062.4%2.3%58836
    Thailand2.3 × 1041.4 × 1061.7%0.9%62448
    Nigeria1.9 × 1041.9 × 1061.0%0.4%30125
    Turkey1.4 × 1041.7 × 1060.9%0.4%65929
    Cameroon1.1 × 1045.8 × 1051.8%0.5%17614
    Sri Lanka9.7 × 1031.6 × 1056.2%3.4%14716
    Guatemala7.1 × 1033.1 × 1052.3%1.7%7916
    Haiti6.9 × 1032.4 × 1052.9%3.0%23322
    Dominican Republic6.3 × 1031.9 × 1053.2%2.6%18611
    Venezuela6.0 × 1036.7 × 1050.9%0.4%22411
    Tanzania5.8 × 1031.7 × 1060.3%0.2%1028
    Algeria5.8 × 1037.6 × 1050.8%0.1%10920

Supplementary Materials

  • Supplementary Materials

    More than 1000 rivers account for 80% of global riverine plastic emissions into the ocean

    Lourens J. J. Meijer, Tim van Emmerik, Ruud van der Ent, Christian Schmidt, Laurent Lebreton

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