Assessing the Potential Microplastic Sources and Retention Efficiency in Valencia's Tancat de la Pipa Wetland

Caprar, I., Monerris, M. M., Hernandez-Crespo, C., Cabrera, D. C., & Baciu, C. (2026). Assessing the Potential Microplastic Sources and Retention Efficiency in Valencia's Tancat de la Pipa Wetland. Applied Sciences, 16(17), 8748. https://doi.org/10.3390/app16178748

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Abstract

Constructed wetlands are promising nature-based solutions for mitigating environmental pollution, able to retain suspended solids as microplastic (MP) particles. This study aims (i) to identify potential sources and transport pathways of MPs in the Tancat de la Pipa constructed wetland (Spain), using a conceptual source-attribution approach based on spatial distribution, particle characteristics, catchment characteristics, hydrological connections, and the available literature and official information, as well as (ii) to evaluate the effectiveness of the wetland in retaining MPs within the investigated size range. Sampling was conducted at six locations representing two inlet canals, two internal sites, and two outlet points of the wetland towards Albufera Lake. Higher MP abundances were recorded at the inlet, while lower concentrations at internal and outlet sites indicated partial retention, with apparent removal efficiencies ranging from 24% to 50%, depending on the sampling campaign. Blue and transparent MPs predominated, while polyethylene (47%) and polyester (18%) were the dominant polymers, followed by polymethyl methacrylate (10%), polystyrene (8%), and polypropylene (7%). The spatial distribution and particle characteristics, together with catchment land use and hydrological connections, indicated potential contributions from mixed sources, including packaging, agricultural activities, wastewater, traffic runoff, fisheries, and industrial activities. These findings provide an initial assessment of potential MP sources and transport pathways in a Mediterranean wetland and indicate partial retention of MPs within the investigated size range, supporting the need for longer-term and source-specific monitoring to improve source attribution and evaluate seasonal variability. (text copied from the article)

Keywords: microplastics; wetland; Albufera; pollution; nature-based solutions

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Objective

This study aimed (i) to identify potential sources and transport pathways of MPs in the Tancat de la Pipa constructed wetland (Spain) using a conceptual source-attribution approach based on short-term spatial distribution, particle characteristics, catchment characteristics, hydrological connections, and available literature and official information, and (ii) to evaluate the effectiveness of the wetland in retaining MPs within the investigated size range.

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Study Area

The present study was conducted in the Tancat de la Pipa wetland (39.368046, –0.345619 to 39.359275, –0.346540 area) (Figure 1), a 40-ha restored wetland located on the northern side of Albufera Natural Park (Valencia, Spain), a park declared as a Ramsar site, a Zone of Special Protection for Birds and a Natura2000 site. Tancat de la Pipa, an area previously used for rice cultivation, was restored between 2007 and 2009 as part of an ecological restoration project aimed at improving the water quality of Albufera Lake while increasing biodiversity. The design of Tancat de la Pipa follows nature-based solution principles, integrating shallow lagoons, sedimentation areas, and vegetated zones dominated by emergent macrophytes. These elements collectively promote hydrodynamic slowing down, particle settling, and biological processing of contaminants before water is discharged into the lagoon. The system comprises approximately 9–10 ha of free water surface-flow wetlands, divided into four vegetated basins, together with two shallow lagoons (the Educative Lagoon, ~6 ha, and the Reserve Lagoon, ~8 ha) and an artificial pool of approximately 4.5 ha supplied by groundwater. Water enters from agricultural drainage channels and the Albufera lagoon, flows through the vegetated basins, passes into the lagoons, and is finally discharged back to the lake. The wetland is dominated by emergent macrophytes, including common reed (Phragmites australis), cattails (Typha spp.), bulrushes, rushes (Juncus spp.), sedges (Carex spp.), and yellow flag iris (Iris pseudacorus), while the lagoons support extensive communities of submerged macrophytes and charophytes. This diverse vegetation promotes sedimentation, nutrient uptake, and habitat creation, making Tancat de la Pipa an important example of a nature-based solution for improving water quality and supporting aquatic biodiversity in the Albufera ecosystem. Together, these processes contribute to the removal of nutrients, suspended solids, organic contaminants, and emerging pollutants, including microplastics, from incoming waters.

Figure 1. Location of Tancat de la Pipa wetland. (a) Continental Spain, Valencian Community (the community boundary is marked in orange); (b) Albufera Natural Park (the park demarcation area is marked in orange); (c) the Tancat de la Pipa wetland (the wetland demarcation area is marked in orange).Tancat de la Pipa receives water from two main tributaries: the Catarroja Canal/Acequia del Puerto de Catarroja (PC) and the 43.5 km long Poyo stream/Barranco del Poyo (BP) (Figure 2), which drains urban, industrial, and agricultural areas. Tancat de la Pipa discharges water into the Albufera Lake through a system of managed cells with inlets and outlets.

:Figure 2. The pathways of the Poyo Stream (marked in dark blue) and the Catarroja Canal (marked in purple) from the formation area to the overflow into Lake Albufera.At the inlet points, where water enters from the Catarroja canal (PC) and from Poyo stream (BP), flow velocities are relatively high, favouring the transport of suspended particles, including microplastics. As water moves into the internal basins, flow velocities decrease due to basin widening, vegetation density, and increased hydraulic residence time. These conditions enhance sedimentation, filtration by macrophytes, and particle interception, which are recognized mechanisms for MP retention in constructed and natural wetlands.Vegetated zones, in particular, act as physical barriers that trap particles through stem interception and biofilm adhesion, a process shown to be effective for both MPs and fine suspended matter. The outlet points represent the final control points of the system, where only a fraction of the incoming microplastics is released back into Lake Albufera. Previous studies on constructed wetlands have demonstrated that such multi-cell designs significantly reduce microplastic abundance between inlet and outlet, with reported retention efficiencies often exceeding 50%, depending on particle size and hydrodynamic conditions.Hydraulic travel time between the inlet and outlet zones was considered in the interpretation of the sampling design. Martin et al. (2014) in previous hydraulic management documentation for Tancat de la Pipa reported a nominal hydraulic retention time (HRT) of approximately 3.3 days under the specified hydraulic loading conditions. This value represents the theoretical water residence time of the wetland and should not be interpreted as a direct measurement of the travel time of individual water volumes or microplastic particles from the inlet to the outlet. Martin et al. (2013) stated that the hydraulic retention time of Tancat de la Pipa is dependent on the hydraulic loading and operational configuration of the wetland.Smaller particles may remain in suspension and pass through the system, while larger fragments and fibres are preferentially retained in sediments and vegetation mats. This spatial organization makes Tancat de la Pipa particularly suitable for investigating not only the presence of microplastics, but also their potential sources, transport pathways, and retention efficiency within a wetland system.The wetland is surrounded by a complex mosaic of land uses that exert diverse pressures on water quality, potentially contributing to MP transport and resuspension.

Industry

The industrial belt surrounding the Albufera Natural Park, particularly within the municipality of Catarroja (l'Horta Sud, Valencia), represents a relevant potential source of microplastic pollution to the Tancat de la Pipa wetland. This area hosts a dense concentration of plastic manufacturing, plastic packaging, chemical processing, logistics, and material manipulation companies. The Catarroja Industrial Park hosts approximately 450 companies, with a notable share engaged in chemical, rubber, and plastics-related activities (≈6% of enterprises) alongside broader manufacturing and supply sectors. Plastic pellets, fragments, films, and fibres can be unintentionally released during manufacturing, cutting, storage, transport, and waste handling phases. These losses are widely recognised as an important source of primary and secondary microplastics in aquatic environments, particularly in industrialised catchments. The Catarroja Canal receives water from urban runoff and agricultural drainage, including rice fields and horticultural land, across municipalities such as Catarroja, Paiporta, and Torrent. Furthermore, runoff from the Port of Catarroja may contribute additional synthetic particles originating from urban runoff, combined sewer overflows (CSOs), and industrial activities. The Poyo stream (43.5 km) functions as an intermittent but highly effective drainage corridor that integrates runoff from urban, agricultural, and peri-urban industrial areas of the southern Valencia metropolitan region municipalities (e.g., Torrent, Picanya, Paiporta, Massanassa, and Catarroja). The Poyo stream is likely influenced by multiple microplastic input pathways, namely municipal wastewater, stormwater runoff, industrial and port-related activities with plastic manufacturing, packaging industries, construction material production, other polymer-processing facilities, and agricultural activities. Wastewater Treatment Plant (WWTP) effluents are commonly discharged into nearby irrigation/drainage channels, which then connect to the Albufera system, and these discharges are typically treated wastewater (secondary or tertiary treatment depending on the plant), reused for irrigation or released when excess flow occurs. Even when wastewater is treated, significant quantities of microplastics, especially fine fibres from synthetic textiles and small fragments, can pass through treatment processes and enter connected waterways. Given this hydrological configuration, MPs originating from industrial activities may reach Tancat de la Pipa through indirect WWTP effluent discharges into the Catarroja canal and Poyo stream. In addition, CSOs during intense rainfall can introduce untreated domestic sewage, increasing MP loads rapidly during storm events. During rainfall events, this channel rapidly mobilises surface materials accumulated in its catchment, including sediments, nutrients, and anthropogenic debris such as plastics. Hydrological studies of the basin highlight its role as a conduit linking densely urbanised zones with downstream wetland environments, ultimately contributing inflows toward the Albufera system through connected drainage networks. Navigable canals and boat traffic may contribute to microplastic inputs through paint abrasion, rope and net degradation, and resuspension of previously deposited plastic particles.

Agriculture

To the west and northwest, extensive rice cultivation areas dominate the Albufera Natural Park landscape, where plastic films, irrigation infrastructure, and agricultural inputs represent potential sources of microplastics transported through irrigation return flows and drainage canals. Albufera Natural Park consists of an interconnected landscape of shallow lagoons, marshes, and extensive rice-growing areas that occupy approximately 223 km2 around the lagoon. In the context of Tancat de la Pipa, rice fields surrounding the wetland are frequently irrigated through a network of canals and drainage channels connected to the wetland system. Rice paddies create a distinct seasonal cycle of flooding and desiccation, as fields are intentionally flooded during the growing season and drained in spring and autumn, which influences water movement, sediment transport, and nutrient dynamics across the wetland landscape. Given the shallow nature of Albufera lake and its connectivity with surrounding irrigation networks, cultivated rice lands represent a critical interface between terrestrial agriculture and aquatic ecosystems. Studies of organic contaminants have documented the presence of multiple agrochemicals, including herbicides, insecticides, and fungicides, throughout water and sediment matrices during the rice cultivation period, with herbicides frequently detected at high concentrations. Approximately 35 tonnes of pesticides are yearly applied in the Albufera Natural Park, and on average, more than 2 ± 0.6 (mean ± standard deviation) tonnes of pesticides are discharged annually from rice paddies to ditches. Bentazone, a widely used herbicide, was identified as the single most applied compound in this regime. The hydrological connectivity maintained through irrigation networks ensures that these agricultural signals propagate across the wetland, affecting ecological processes well beyond the cultivated fields. Plastic mulch films, irrigation pipes, greenhouse materials, and fertilizer or pesticide packaging can degrade into microplastics and be transported through irrigation return flows and drainage canals. Plastic films used for mulching and soil covering are particularly relevant because they are often made of polyethylene (PE) and are exposed to UV radiation, temperature changes, and physical abrasion, which accelerate fragmentation into micro-sized particles. (text copied from the article)

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Methods

Field sampling and laboratory analysis were conducted across Tancat de la Pipa, a restored wetland within the Albufera de Valencia Natural Park. The vegetation in Tancat de la Pipa consists of a mix of aquatic (like Common reed, Bulrushes, Water lilies, and Hornwort), riparian (Rushes and sedges), and marshland plant species, which support a wide variety of wildlife.

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Results

Findings from Tancat de la Pipa Wetland indicate that it reduces microplastic loads. 

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Conclusion

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The article:

Caprar, I., Monerris, M. M., Hernandez-Crespo, C., Cabrera, D. C., & Baciu, C. (2026). Assessing the Potential Microplastic Sources and Retention Efficiency in Valencia's Tancat de la Pipa Wetland. Applied Sciences, 16(17), 8748. https://doi.org/10.3390/app16178748