Plastic debris forms: Rock analogues emerging from marine pollution.

Continuous input of plastic litter in ocean and coastal environments achieved alarming levels that are exposing new settings in natural systems. While novel plastic debris pollution, with rock-like appearance, has been reported worldwide, fundamentally geological analyses are still lacking. We surveyed the first occurrence of multiple associated plastic debris on a single outcrop located in a remote site (Trindade Island, SE Atlantic Ocean). Even though all plastic debris forms consisted of polypropylene and polyethylene, through a sedimentary approach (cross section, macro, and micro analyses) distinct types were identified. We detected plastiglomerates, geogenic analogous to conglomerates, divided into in situ and clastic types, and formed over beach sediment. We identified plastistones as a new type with homogeneous composition (lacking incorporated materials), geogenic-looking igneous rocks, divided into in situ and clastic types, and formed over rock surfaces. We linked pyroplastics, geogenic analogous to clasts, to clastic plastiglomerates/plastistones, therefore representing clastic types of plastic debris forms. This association was correlated in a depositional system model, which suggests that plastic debris forms are rock synthetic equivalents in which humans act as depositional and post-depositional agents.

Quality and Disposal of Dredged Sediments from Tidal Deltas in Subtropical Bays in Southern Brazil.

In order to measure the contamination of dredged and beach sediments and the applicability of sediment quality guidelines in a wet subtropical region of southern Brazil, the areas surrounding both the Paranaguá and Babitonga estuaries were studied, including their harbour zones and adjacent beaches. Investigation of the sampled sediments comprised optical and electron microscopy, energy-dispersive X-ray spectroscopy, inductively coupled plasma mass spectrometry, and physicochemical and toxicological analyses. Additionally, data provided by the harbours administrations on dredged volumes, sedimentology, and coastal dynamics were compared. It was determined that the studied sediments, especially the ones from both tidal deltas, have similar characteristics, including physical and chemical parameters. It was also confirmed that tidal deltas are depositional areas with low potential to accumulate pollutants. Therefore, the current disposal of this scarce sandy material during dredging might not be beneficial, considering the significant sand removal amount from the coastal depositional system.