Quantity and type of plastic debris flowing from two urban rivers to coastal waters and beaches of Southern California

Abstract

Plastic debris is a common persistent pollutant in marine and coastal environments worldwide. Questions naturally arise among those dealing with the debris as to its source. Here we quantify the contribution of a large urban area, the Los Angeles basin, to the problem via the two main rivers draining its watershed. Samples of river water were taken with a variety of nets during both rainy and dry conditions from mass emission sites above the reach of tidal influence in the Los Angeles and San Gabriel Rivers. The samples were from different strata in the flowing rivers using nets with less than 1mm mesh. Laboratory analysis of the samples divided the plastic debris into two size classes: >=1mm, <4.75mm, and >=4.75mm. A reason for the two size classes, in addition to providing a distinction between macro and micro debris, was that under California law, debris less than 5mm is not considered trash subject to regulation. The debris was first sorted into natural, plastic, and non-plastic manmade items. The plastic debris was then classified by type; either fragments, foams (mainly polystyrene), pre-production resin pellets, line, or films. Results extrapolated for 24 hours of flow from one moderate and one heavy rain day and one dry day when added together produced the following for 72 hours: Total number of plastic objects and fragments, 2,333,871,120.0 (2.3 billion), total weight of plastic objects and fragments 30, 438.52 kg (30 metric tons). In terms of the number of pieces, the majority, 71% were foams, with miscellaneous fragments at 14%, pre-production resin pellets at 10% and whole items at 1%. In terms of weight, however, whole items were the heaviest, at 37% of the total, followed by fragments at 29%, pellets at 13% and foamed polystyrene at 11%.

Micro- and Nanoplastic Pollution of Freshwater and Wastewater Treatment Systems

“…In the Danube, plastic load at mean flow and a correction factor for population density were used to calculate plastic inputs to the Black Sea [57]. Flow rate data from two California rivers were also used to estimate yields of [2 billion particles over a 72 h period [69]. In Venice, high correlations were observed between small microplastics and fine grain size, indicating both follow similar sinking and accumulation processes, with higher accumulation of MNP in low energy sites [93].…”

Sources and sinks of microplastics in Canadian Lake Ontario nearshore, tributary and beach sediments

“…Rivers and urban tributaries, however, have been shown to be major transport pathways for microplastics and macroplastics (Moore et al, 2011;Gasperi et al, 2014;Lechner et al, 2014;Rech et al, 2014;Zhao et al, 2014;Corcoran et al, 2015;Naidoo et al, 2015). Whereas buoyant materials are transported on surface waters (Gasperi et al, 2014), non-buoyant materials are transported along the tributary bed (Moore et al, 2011;Morritt et al, 2014).…”

“…Rivers and urban tributaries, however, have been shown to be major transport pathways for microplastics and macroplastics (Moore et al, 2011;Gasperi et al, 2014;Lechner et al, 2014;Rech et al, 2014;Zhao et al, 2014;Corcoran et al, 2015;Naidoo et al, 2015). Whereas buoyant materials are transported on surface waters (Gasperi et al, 2014), non-buoyant materials are transported along the tributary bed (Moore et al, 2011;Morritt et al, 2014). Microplastic debris loads can be introduced into tributaries via non-point spill and litter sources as well as point sources such as effluent pipes (Lechner & Ramler 2015), storm water drainage outlets (Armitage & Rooseboom 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 Ballent, Anika Manuscript page 3 2000) and possibly wastewater treatment plants, particularly during combined sewage overflow and bypass events during heavy precipitation conditions (MacDonald and Podolsky, 2009).…”

Sources and Fate of Microplastics in Urban Areas: A Focus on Paris Megacity

“…However, microplastics in freshwater environments represent only a small fraction of this amount. The first articles on microplastics in freshwater were published in 2011 and focus mainly on Lake Huron [6] and Los Angeles rivers [7] in the USA. Since that period, numerous studies have been published covering all continents, with the exception of Antarctica, and all the potentially impacted environments (water and sediment for the aquatic environment, banks for the terrestrial environment).…”