The spatial distribution of microplastics in topsoils of an urban environment - Coimbra city case-study.

Due to their seemingly ubiquitous nature and links to environmental and human health problems, microplastics are quickly becoming a major concern worldwide. Artificial environments, such as those found in urban environments, represent some of the main sources of microplastic. However, very few studies have focused on the occurrence of microplastics in urban soils. The aim of the current research was to evaluate the microplastic contamination in urban soils from artificial and natural land uses throughout Coimbra city, Portugal. Sixty-seven spaces and ten land use areas were evaluated. The artificial land use areas were dumps, landfills, parking lots, industries and construction areas, and the natural land use areas were forests, urban parks, moors (wetlands), pastures and urban agricultural areas. Microplastic extraction was done by density separation. Quantification and size measurements of microplastics was carried out using a microscope. Polymer types were identified by µ-FTIR for 25% of the samples. The microplastic content ranged from 5 × 103 to 571 × 103 particles·kg-1, with a mean of 106 × 103 particle·kg-1. The green park was the land use with the highest concentration of microplastics (158 × 103 particle·kg-1) and the forest was the one with the lowest concentration (55 × 103 particle·kg-1). The landfill (150 × 103 particle·kg-1), industry (127 × 103 particle·kg-1) and dump (126 × 103 particle·kg-1) were the artificial spaces with the highest levels of microplastics. The main polymers detected were polypropylene and polyethylene, followed by polyvinyl chloride and rubber, and the main sizes measured between 50 and 250 µm. Our results indicate that natural spaces can contain higher amounts of microplastics as compared to artificial spaces in the urban environment. This suggests that microplastics are easily transported through the urban landscape and that urban green spaces can retain microplastics in their soils. Land use planning may present an opportunity to better control the levels of microplastics in urban environments.

Accumulation of airborne microplastics on leaves of different tree species in the urban environment.

Microplastics (MPs) are omnipresent in the environment and they are linked to ecosystem and human health problems. The atmospheric transport of MPs and the role of tree leaves in MP atmospheric deposition has not been adequately studied. MP concentrations on the leaves of different tree species in urban regions of the Netherlands and Portugal, along with related MP deposition, were investigated in this study. We collected leaves from cedar, eucalyptus, oak, pine and willow trees, together with monthly deposition of particles under the trees and in the open space in Coimbra (Portugal). In Wageningen (the Netherlands), we collected leaves from a fir and a holly tree at different heights above the ground and with dry and wet weather conditions. MPs were extracted through density separation and quantified under a microscope. Polymer types were identified using µ-FTIR. The results showed a higher number of MP particles on the needle-shaped leaves from fir (2.52 ± 2.14 particles·cm-2) and pine (0.5 ± 0.13 particles·cm-2) and significantly lower numbers of MPs per cm2 of leaf area on the bigger leaves from eucalyptus (0.038 ± 0.003 particles·cm-2) and cedar (0.037 ± 0.002 particles·cm-2). All tree leaves seemed to filter airborne MPs, especially the smallest particles. A non-significantly higher number of particles on leaves was detected on lower tree branches and after dry periods. The deposition of MPs under trees was generally higher than in the open space. Our results indicated that part of the MPs retained by the tree leaves floats down to lower branches and to the soil surface. We also saw that different tree species had different capacities to retain particles on their leaves over time. To control the transport of MPs through the atmosphere, it is essential to consider the role of different vegetation types in filtering small particles, especially in cities.

Assessing long-term changes in potential ecosystem services of a peri-urbanizing Mediterranean catchment.

Society depends on goods and services provided by ecosystems, not only for survival but also for general wellbeing. Over the last decades, peri-urban areas have been subject to the pressure of urbanization and, thus, land-use changes. These changes modify the natural ecosystems and their ability to support human security and safety, but the extent of these impacts is not well-known. This study investigates the impact of five decades of land-use changes in potential ecosystem services (ESs) supply, in the peri-urban Ribeira dos Covões catchment, located in the periphery of Coimbra one of the largest cities in central Portugal. Based on eight land-use maps from 1958 to 2012, the ESs were estimated through a quantification matrix developed by local stakeholders. The expansion of urban and forest areas from 7% to 40% and from 43% to 55%, respectively, mostly through the occupation of agriculture fields (reduced from 48% to 4%), together with changes in the type of forest area (from mixed to commercial broad-leaved), led to a 73% reduction in the ESs potential supply. This reduction was driven by major losses in regulation but also provisioning services. Catchment management and urban planning should be supported by ESs assessment in order to mitigate the negative impacts on regulation, provisioning and cultural services provided by the ecosystems, and thus maximize the benefits for society.