We studied the chemical composition of As and Pb in total (<2 mm) and fine fractions (<50 μm) of 52 urban soil samples from Minas de Riotinto (mining area) and Aracena (non-exposed area) in SW Spain. In addition to a soil phytotoxicity bioassay using Lactuca Sativa L., we modelled and performed carcinogenic and non-carcinogenic human health risk assessment, later comparing our data with relative cancer mortality rates reported at the municipal level. This study demonstrates that mineralized bedrock and natural soil-forming processes affect the geochemistry of natural (in-situ) urban soils, which in many cases surpass the regulatory levels for As (36 mg/kg) and Pb (275 mg/kg). Fine fractions of in-situ and mixed urban soils -susceptible of inhalation- are significantly enriched in As and Pb with respect to fine fractions of aggregate materials (ex-situ soils of chalky sands and gravel) in Minas de Riotinto. The soils in Minas de Riotinto are significantly enriched in As (total and fine fractions) and Pb (total fraction) with respect to Aracena. Despite elevated bulk concentrations of As and Pb, only one in-situ sample exhibits phytotoxic effects of the soil-water extracts on Lactuca Sativa L. seeds. Health risk assessment of these towns as exposure areas indicates that the soils of Minas de Riotinto are indeed a health risk to the residents, whereas there is no potential risk in Aracena. The reported relative mortality rates in Minas de Riotinto show a greater mortality of carcinogenic tumors potentially related to As and Pb exposure, including lung cancer. Both soil type and use must be considered when administrators or policy-makers evaluate health risks involved in urbanistic decision-making. To minimize exposure risk and adverse health outcomes, we recommend that in-situ soils surpassing regulatory levels for As and Pb in public playgrounds and passing areas should be covered with aggregate materials.

The mechanisms of trace element uptake by seaweeds are still unknown, despite being key to understand the impact of pollution in coastal environments. This knowledge gap, in addition to the lack of standardization, have also hindered the use of seaweeds to monitor seawater pollution. To address these shortcomings, we tested the use of devitalization as a pre-exposure treatment for brown seaweed transplants, and we compared devitalized and fresh transplants to gain some insights into the mechanisms of element uptake. We exposed four types of Fucus vesiculosus transplants in 6 sites for 4, 8 and 20 days: fresh and devitalized (dried or boiled) algal segments held in mesh bags, and whole algal thalli imitating natural conditions. We then determined he concentrations of 11 trace elements in the algal tissues. The element concentrations were highest in the devitalized transplants, but the material lost consistency and weight throughout the exposure period, limiting their use to short periods. We proposed several factors that may contribute to the different accumulation patterns between treatments, and examined the implications for the uptake mechanisms, revealing that two of the most important are surface adsorption of sediment particles and chemical bounds to extracellular components.

The leaves of trees and shrubs can capture atmospheric pollutants such as polycyclic aromatic hydrocarbons (PAHs), and the capacity of uptake depends on the leaf traits. Although numerous studies have measured PAH concentrations in leaves of woody plants and the variability in leaf traits, few have investigated the relationship between these factors. We conducted a literature review to summarize the available information on this topic and found that five types of leaf traits have been studied, with those associated with leaf morphology and gas exchange being the most common. However, the results of the studies are often contradictory. To address these discrepancies, we conducted a meta-analysis to examine how PAH uptake by woody species is affected by leaf ecological traits associated with morphology (leaf area, specific leaf area [SLA], leaf thickness and leaf width/length ratio [W/L]) and with gas exchange (stomatal conductance, leaf carbon isotopic signature [δ¹³C] and stomatal density). The meta-analysis included studies involving at least two different species with comparable PAH concentrations. Many of the studies did not examine the relationship between ecological traits and PAH concentration, and those that did often involve different traits. We therefore used the TRY Plant Trait Database data as the standard source of trait data. Relationships were analyzed by determining differences regarding PAHs and traits and calculating Spearman correlations and their significance. The leaf morphology traits were more closely correlated with PAH concentrations than the gas exchange traits. Thus, morphological traits such as SLA and leaf area can be considered significant predictors of PAH uptake, especially for particulate-associated PAHs. Gas exchange traits showed less consistent correlations, indicating the complexity of factors influencing PAH uptake in leaves. This study highlights the importance of considering multiple leaf traits in order to better understand and predict PAH uptake in woody plants.

Mosspheres are a kind of moss transplants which offer a novel approach for detecting atmospheric pollution using devitalized mosses, as they reflect the atmospheric deposition of certain elements and polycyclic hydrocarbons. However, due to the unique features of the mosspheres such as the low elemental concentrations in the cultured material, the data treatment needs to be different from that of conventional biomonitoring studies. In this article, our objectives are to identify the best parameter for expressing the levels of chemical elements accumulated by mosspheres, and to apply a recently developed method to assess the probability of pollution of each sample and of the study area. To do this, we used data from a study in which 81 mosspheres were exposed in a medium-sized city in southwestern Europe. Comparing different pollution indices, we selected the enrichment rate (ER) as the most useful, as it is resilient to fluctuations in the initial concentrations and takes into account the time factor, allowing for greater comparability among studies. Then, we determined that the statistical distribution of the ERs of most elements fitted a normal distribution, showing that most samples did not differ significantly from the background concentrations for these elements. On the other hand, for Ni, Pb and Zn there was a subpopulation of samples above background values. In these cases, we determined the probability of pollution of each sample. Finally, we used indicator kriging to calculate the probability of pollution across the study area, identifying the polluted areas, which for some elements match the distribution of the main industries and highways, indicating that this is a suitable protocol to map elemental pollution in urban areas.

Seaweed transplants have been widely used to monitor coastal marine pollution, yet their effectiveness in reflecting seawater elemental concentrations remains uncertain. This study investigated the relationship between elemental concentrations in Fucus vesiculosus transplants (both fresh and dried) and seawater samples representative of the transplants' exposure period collected using autosamplers. The transplants were deployed across 22 coastal sites in northwest Spain over 14 days. No significant correlations were found between seawater elemental concentrations and those in transplants for any element. Similarly, seawater physicochemical properties (pH, dissolved oxygen, conductivity, and temperature) and the pre-exposure concentrations in transplants had minimal influence on post-exposure levels. Elemental concentrations in native seaweeds at the exposure sites were not correlated with those in transplants (except for Zn in the fresh transplants) and did not reflect seawater concentrations either. These findings highlight that element concentrations in seaweed do not follow a straightforward linear relationship between exposure and tissue concentrations. Instead, they result from a complex interplay of various, yet unknown environmental factors that influence element bioavailability in the water and the physicochemical properties of the seaweed. This complexity calls into question the suitability of seaweed transplants as effective biomonitors for marine pollution.