SEGH Articles

Spatial distribution of Pb, Cd and Cr concentrations in moss transplants from urban recreational areas in Lisbon, Portugal

03 December 2012
Metal concentrations in moss were used to assess the contribution of atmospheric pollution to the geochemistry of soil and ground-level dust, and discriminate urban pollution sources.

Sofia Bartolomeu is currently a final year Master student in Meteorology and Oceanography Physics at University of Aveiro, Portugal. She was a Poster Winner at the 9th ISEG meeting in Aveiro, Portugal in July. She is currently working on the “Geochemical survey of Lisbon urban soils” project at the Geosciences Department of the University of Aveiro, supervised by Dr. Paula Marinho. The main aim of her study was to report on spatial patterns for some metal concentrations in moss transplants that were exposed to the urban ambient air in public recreational areas in Lisbon. Metal concentrations in the moss were used to assess the contribution of atmospheric pollution to the geochemistry of soil and ground-level dust, and discriminate urban pollution sources.

Owing to their ability to accumulate heavy metals, mosses are especially suitable to monitor heavy metal airborne pollution. Heavy metals are taken up very fast due to the lack of an epidermis and a cuticle, and they have a large surface-to-weight ratio.

This study presents results from a project entitled “Geochemical survey of Lisbon urban soils: a baseline for future human health studies”, and the main aims are (1) to report on spatial patterns for Pb, Cd and Cr concentrations in moss transplants from public recreational areas in Lisbon; (2) to compare such patterns with those of soil and ground-level dust. Fifty one topsoil and ground-level dust samples were collected in playgrounds, schoolyards, urban parks, public gardens, road-side and airport of Lisbon. At each site, 1 uncontaminated moss transplant was fixed to a horizontal tree limb, which remained in situ for a period of 6 months. Only 44 moss samples were recovered from site. The selected moss species was the Hypnum cupressiforme Hedw and the green part was used for analysis of Pb, Cd and Cr by ICP-MS.

 

For Pb, the results show that concentrations are high, range from 7.2-75.1 mg kg-1 and the higher values occur in the older part of the city. Lead emissions are mainly related to traffic and the physiographic characteristics of the old city explain the higher Pb concentrations in the moss. The element has a similar spatial distribution in soils and dusts, suggesting that airborne Pb-particles settle in the topsoil. For Cd, the results show that concentrations are low, range from 0.08-0.44 mg kg-1 and the spatial distribution is irregular, indicating point sources. However, the airport moss samples have the highest Cd concentrations. Also soil and dust samples form the airport have the highest Cd concentrations, which suggest that air-traffic is a source of Cd in the city. For Cr, the results show that concentrations range from 1.6-8.9 mg kg-1 and the higher values occur in the old city. Soils and dust show different distribution patterns, perhaps due to the fact that in the city Cr has an important geogenic source. 

In conclusion and despite the fact that by its location on the Atlantic coast and winds regime, high levels of pollutants are uncommon in Lisbon, the biomonitoring survey indicates that Pb emissions are probably traffic related, are still significant and have an higher environmental impact in the old city where the housing density is higher, the streets are narrow and have strong slopes, and the traffic is quite intense. Concentrations of Cd and Cr are quite lower and metal-laden airborne particles do not seem to be a significant source to the urban soils.

 

Sofia Bartolomeu

Physics Department, University of Aveiro, Campus de Santiago, 3810-193, Aveiro, Portugal, 1. sofiabartolomeu@ua.pt

Keep up to date

Submit Content

Members can keep in touch with their colleagues through short news and events articles of interest to the SEGH community.

Science in the News

Latest on-line papers from the SEGH journal: Environmental Geochemistry and Health

  • Fertilizer usage and cadmium in soils, crops and food 2018-06-23

    Abstract

    Phosphate fertilizers were first implicated by Schroeder and Balassa (Science 140(3568):819–820, 1963) for increasing the Cd concentration in cultivated soils and crops. This suggestion has become a part of the accepted paradigm on soil toxicity. Consequently, stringent fertilizer control programs to monitor Cd have been launched. Attempts to link Cd toxicity and fertilizers to chronic diseases, sometimes with good evidence, but mostly on less certain data are frequent. A re-assessment of this “accepted” paradigm is timely, given the larger body of data available today. The data show that both the input and output of Cd per hectare from fertilizers are negligibly small compared to the total amount of Cd/hectare usually present in the soil itself. Calculations based on current agricultural practices are used to show that it will take centuries to double the ambient soil Cd level, even after neglecting leaching and other removal effects. The concern of long-term agriculture should be the depletion of available phosphate fertilizers, rather than the negligible contamination of the soil by trace metals from fertilizer inputs. This conclusion is confirmed by showing that the claimed correlations between fertilizer input and Cd accumulation in crops are not robust. Alternative scenarios that explain the data are presented. Thus, soil acidulation on fertilizer loading and the effect of Mg, Zn and F ions contained in fertilizers are considered using recent \(\hbox {Cd}^{2+}\) , \(\hbox {Mg}^{2+}\) and \(\hbox {F}^-\) ion-association theories. The protective role of ions like Zn, Se, Fe is emphasized, and the question of Cd toxicity in the presence of other ions is considered. These help to clarify difficulties in the standard point of view. This analysis does not modify the accepted views on Cd contamination by airborne delivery, smoking, and industrial activity, or algal blooms caused by phosphates.

  • Effects of conversion of mangroves into gei wai ponds on accumulation, speciation and risk of heavy metals in intertidal sediments 2018-06-23

    Abstract

    Mangroves are often converted into gei wai ponds for aquaculture, but how such conversion affects the accumulation and behavior of heavy metals in sediments is not clear. The present study aims to quantify the concentration and speciation of heavy metals in sediments in different habitats, including gei wai pond, mangrove marsh dominated by Avicennia marina and bare mudflat, in a mangrove nature reserve in South China. The results showed that gei wai pond acidified the sediment and reduced its electronic conductivity and total organic carbon (TOC) when compared to A. marina marsh and mudflat. The concentrations of Cd, Cu, Zn and Pb at all sediment depths in gei wai pond were lower than the other habitats, indicating gei wai pond reduced the fertility and the ability to retain heavy metals in sediment. Gei wai pond sediment also had a lower heavy metal pollution problem according to multiple evaluation methods, including potential ecological risk coefficient, potential ecological risk index, geo-accumulation index, mean PEL quotients, pollution load index, mean ERM quotients and total toxic unit. Heavy metal speciation analysis showed that gei wai pond increased the transfer of the immobilized fraction of Cd and Cr to the mobilized one. According to the acid-volatile sulfide (AVS) and simultaneously extracted metals (SEM) analysis, the conversion of mangroves into gei wai pond reduced values of ([SEM] − [AVS])/f oc , and the role of TOC in alleviating heavy metal toxicity in sediment. This study demonstrated the conversion of mangrove marsh into gei wai pond not only reduced the ecological purification capacity on heavy metal contamination, but also enhanced the transfer of heavy metals from gei wai pond sediment to nearby habitats.

  • Cytotoxicity induced by the mixture components of nickel and poly aromatic hydrocarbons 2018-06-22

    Abstract

    Although particulate matter (PM) is composed of various chemicals, investigations regarding the toxicity that results from mixing the substances in PM are insufficient. In this study, the effects of low levels of three PAHs (benz[a]anthracene, benzo[a]pyrene, and dibenz[a,h]anthracene) on Ni toxicity were investigated to assess the combined effect of Ni–PAHs on the environment. We compared the difference in cell mortality and total glutathione (tGSH) reduction between single Ni and Ni–PAHs co-exposure using A549 (human alveolar carcinoma). In addition, we measured the change in Ni solubility in chloroform that was triggered by PAHs to confirm the existence of cation–π interactions between Ni and PAHs. In the single Ni exposure, the dose–response curve of cell mortality and tGSH reduction were very similar, indicating that cell death was mediated by the oxidative stress. However, 10 μM PAHs induced a depleted tGSH reduction compared to single Ni without a change in cell mortality. The solubility of Ni in chloroform was greatly enhanced by the addition of benz[a]anthracene, which demonstrates the cation–π interactions between Ni and PAHs. Ni–PAH complexes can change the toxicity mechanisms of Ni from oxidative stress to others due to the reduction of Ni2+ bioavailability and the accumulation of Ni–PAH complexes on cell membranes. The abundant PAHs contained in PM have strong potential to interact with metals, which can affect the toxicity of the metal. Therefore, the mixture toxicity and interactions between diverse metals and PAHs in PM should be investigated in the future.