Leaf trapping and retention of particles by holm oak and other common tree species in Mediterranean urban environments

Holm oak (Quercus ilex), a widespread urban street tree in the Mediterranean region, is widely used as biomonitor of persistent atmospheric pollutants, especially particulate-bound metals. By using lab- and field-based experimental approaches, we compared the leaf-level capacity for particles’ capture and retention between Q. ilex and other common Mediterranean urban trees: Quercus cerris, Platanus × hispanica, Tilia cordata and Olea europaea. All applied methods were effective in quantifying particulate capture and retention, although not univocal in ranking species performances. Distinctive morphological features of leaves led to differences in species’ ability to trap and retain particles of different size classes and to accumulate metals after exposure to traffic in an urban street. Overall, P. × hispanica and T. cordata showed the largest capture potential per unit leaf area for most model particles (Na+ and powder particles), and street-level Cu and Pb, while Q. ilex acted intermediately. After wash-off experiments, P. × hispanica leaves had the greatest retention capacity among the tested species and O. europaea the lowest. We concluded that the Platanus planting could be considered in Mediterranean urban environments due to its efficiency in accumulating and retaining airborne particulates; however, with atmospheric pollution being typically higher in winter, the evergreen Q. ilex represents a better year-round choice to mitigate the impact of airborne particulate pollutants

Tree-rings analysis to reconstruct atmospheric mercury contamination at a historical mining site

Mercury (Hg) is a global environmental concern due to its toxicity (especially high in methylated form) and the long-range distribution of its gaseous elemental form (GEM). Hg-contaminated areas, such as abandoned mining sites, pose intrinsic difficulties for their management and heavy monitoring costs. In these environments, plant-based solutions may play a key role in the ecosystem quality assessment and support remediation strategies, combining reliability and costeffectiveness. In this study, we adopted a biomonitoring approach by using tree rings of four different species collected in the proximity of the miningmetallurgical area of Abbadia San Salvatore, central Italy, a major former Hg mining district whose reclamation is currently in progress. Our dendrochemical analysis was aimed at identifying the historical changes of local atmospheric Hg contamination and at singling out, for the first time in the study area, other potentially toxic elements (PTEs) associated with the past mining activity. Collected cores dated back to early as 1940 and provided the temporal patterns of atmospheric Hg emission vs the produced liquid quantities, so reconstructing the historical impact of the mining site on nearby terrestrial ecosystems and resident human population. Current GEM contamination was found about twenty times lower than that of the fully operational mine periods. From a first survey on other PTEs, thallium (Tl) and lead (Pb) appeared to be potentially associated with the mining activity, thus suggesting new working assumptions for further dendrochemical analyses and for the inclusion of Pb in human biomonitoring surveys of the Mt. Amiata area, actually not present in the control list. The results prompt a more thorough assessment by tracking for a longer time span a critical site that is an ideal open-field lab to study the ecophysiology of different tree species in relation to environmental behavior of PTEs for better-assessing wildlife and human exposures

Influence of Moderate Cd and Pb Soil Pollution on Seed Development, Photosynthetic Performance and Foliar Accumulation in the Medicinal Plant Hypericum perforatum

This study investigated whether moderate soil contamination by Cd and Pb may negatively affect seed germination, photosynthesis and foliar accumulation in the medicinal plant Hypericum perforatum. Seeds were incubated with Cd and Pb solutions of 10 and 100 µM, and two-month-old plants were watered weekly for three weeks with the same solutions. Control samples were treated with deionized water. The percentage of seed germination and seedling length, as well as chlorophyll content, chlorophyll fluorescence and foliar reflectance, were measured, along with the foliar Cd and Pb concentrations. The results indicated that seed germination is not affected, while seedling length is decreased by approximately 81% by high Cd levels. Cadmium was subjected to foliar translocation from the soil depending on the supplied concentration, thus causing reductions in the chlorophyll content (−24%). It is of interest that foliar Cd levels in Cd-treated plants were close to or above the limit for the European Pharmacopoeia. Negative effects of Pb were not detected, but accumulation and blockage of this metal at the root level, although not approached experimentally, cannot be ruled out

Identification of present-day and historical sources of mercury in a complex industrial area

Mercury levels were measured in soils and earthworms on behalf of a long-term surveillance program of the emissions from the industrial area of Scarlino (Southern Tuscany, Central Italy), where a municipal solid waste incinerator and two main chemical plants are currently operating. The study aimed at establishing preliminary soil data to be used as baseline for long-term monitoring of mercury contamination of soil and soil biota and to assess eventual contribution of the industrial emissions. Overall total mercury concentration of superficial soils (0-5 cm), collected from 44 sampling sites randomly selected within a circular area up to 1.5 km from the center of the industrial area, was in average 0.29 ± 0.27 µg g-1 . This value, which remains well below the screening values (1 µg g-1 ) for contaminated soils set by the Italian regulatory framework for residential areas, is approximately 4-5 times higher than the European topsoil baseline (FOREGS) for mercury and highlights a general enrichment of the metal in the area. This is mainly attributable to widespread geochemical anomalies characterizing the Southern Tuscany and to the historical mineral processing and smelting activities that have been carried out in the Scarlino area until the mid-90s. The highest mercury concentrations were found in soils from sampling sites in direct proximity of industrial/artisanal activities, where concentrations up to 1.59 µg g-1 were reached. Average mercury concentrations (0.25 ± 0.10 µg g-1 ) from agricultural and grazing land soils were also noticeable, although earthworms from the same sites did not show a significant bioaccumulation of the metal (0.11 ± 0.09 µg g-1 ). The generally elevated concentrations and the high variability (overall coefficient of variation = 93%) of mercury soil data from the Scarlino area are questioning the possibility to isolate the influence of a single source of contamination in an environment with a long industrialization history. This is currently prompting further research supported by techniques for monitoring atmospheric depositions (i.e. biomonitoring, passive sampling) to improve estimation of mercury contamination arising from different possible sources in the Scarlino are

Air quality in post-mining towns: tracking potentially toxic elements using tree leaves

In this study, leaves of the evergreen holm oak Quercus ilex were used to assess airborne contamination of potentially toxic elements (PTEs) at five towns located on the slopes of the Mt. Amiata (central Italy), an area with a long history of mining and, more recently, an important district for the industrial exploitation of geothermal energy. PTE composition and covariance of washed and unwashed Q. ilex leaves of three different ages (6, 12 and 24 month-old) were used to identify atmospheric inputs of PTEs at residential areas, evaluate long-term adsorption and retention of PTEs by the leaves, thus providing an indication of potential human exposure. Moreover, the determination of foliar concentrations of major elements (C, N, S and P) allowed an assessment of the nutritional status of the investigated urban tree stands which excluded the existence of stress condition caused by air pollution or other disturbances. Results indicated that overall Pb, Cu, and Cd concentration were low in the investigated urban sites, if compared with similar studies conducted in larger Italian cities, denoting a low contribution of vehicular traffic to the atmospheric pathway. The five urban settlements were characterized by a specific profile of elements (Al, Ba, Hg and Sb) enriched in unwashed leaves, resulting from the distinct geochemical characteristics of the area and from diffuse (i.e., urban activity) and point sources of PTEs emission (i.e., brownfields, geothermal power plants). The latter sources primarily govern the distribution of Hg, whose contamination was found to be very localized close to a major abandoned mining area. Our data provided quantitative evidence of the spectrum of PTEs potentially impacting resident population and may prove useful in support of follow-up instrumental monitoring campaigns of air quality, as well as for human health and ecological risk assessments

Bio-Based Solutions for Agriculture: Foliar Application of Wood Distillate Alone and in Combination with Other Plant-Derived Corroborants Results in Different Effects on Lettuce (Lactuca Sativa L.)

Bio-stimulants are showing growing success and are gradually replacing synthetic fertilizers in agriculture. Wood distillate (WD), also known as wood vinegar or pyroligneous acid, is a byproduct of biomass pyrolysis and is increasingly used as a bio-stimulant for crop production. This study investigated whether weekly foliar applications of 0.25% and 0.50% WD have a differential effect on the chlorophyll and sugar content as well as biomass production in lettuce (Lactuca sativa L.). Moreover, the additional beneficial effect from the addition of corroborants of plant origin such as 3% soy lecithin and 5% flavonoid-rich wood glycolic extract to WD (BF) was investigated. Moreover, the possible toxicological concern from some potentially toxic elements (PTEs), namely Cd, Cu, Fe, Pb, and Zn, which may be abundant in WD was verified. After four weeks, we found that 0.25% WD not only increases lettuce biomass, which has an economic value, but also has beneficial effects on other qualitative parameters such as sugars and total sweetness. On the other hand, the use of 0.5% WD decreased the content of soluble sugars, suggesting a hormetic-type effect. We did not find evidence of further beneficial effects from the addition to WD of plant-derived corroborants, nor of any enrichment in the content of the investigated PTEs

Metal(loid) enriched topsoils in a multiple land-use area in Tuscany (Italy): geogenic vs. anthropogenic contributions and associated health risk

The Piana di Scarlino is a partially refilled wetland in the SW of Tuscany (Central Italy) which has hosted chemical and power plants since the 1960s. Presently, in the area there are urban settlements (the main urban center, Follonica, has a population of approx. 25.000), farms, tourist facilities, and industrial districts, mainly based on H2SO4 and TiO2 production as well as waste incineration. In the last two decades the soil and groundwater of the Piana di Scarlino, have been found polluted with arsenic (As) and heavy metals. This prompted local authorities to implement remediation measures and environmental monitoring programs to protect the resident population and the local agricultural produce. In 2013, we initiated an environmental surveillance program in the area within an IPPC permitting procedure for monitoring As and heavy metals and assessing human health implications. The study initially aimed at establishing topsoil data to be used as baseline for long-term monitoring. Overall total As concentration of superficial soils (0-5 cm), collected from 44 sampling sites randomly selected within a circular area up to 1.5 km around the industrial district, was on average 33.8 ± 35.9 µg/g. This value, is approximately 3 times higher than the European baseline and highlights a general enrichment of topsoil As content. This is mainly attributable to widespread geochemical anomalies characterizing Southern Tuscany and to the historical mineral processing and smelting activities carried out in the Scarlino area until the mid-90s. The highest As concentrations were found in soils from sampling sites in the proximity of a pyrite ash dump, where concentrations over 200 µg/g were reached. Average concentrations (32.9 µg/g) from agricultural and grazing soils were also much higher than the baseline for Italian agricultural lands (7.56 µg/g). Although soils from urban sites generally showed the lowest As concentrations, average As concentrations for the urban area (21.8 µg/g) remained over the screening values (20 µg/g) for contaminated soils set by the Italian regulatory framework for residential areas. In this context, we used multi-element analysis supported by techniques for monitoring atmospheric depositions to improve estimation of exposure and related health risks arising from the nearby industrial activities as well as to assess the relative contribution of historical and present-day As sources in the Scarlino area