Application of lead isotopic methods to the study of the anthropogenic lead provenance in Spanish overbank floodplain deposits

Changes in the principal sources of Pb in overbank sediment profiles have been documented for two Spanish areas by using Pb isotopes and Pb concentrations. These locations (Madrid and Tinto–Odiel basin) represent two of the most contaminated regions in Spain. The Community of Madrid is characterized by heavy industrial and urban activity, focused mainly in Madrid City. The Tinto–Odiel basin drains the Iberian Pyrite Belt, which hosts many polymetallic massive sulphides and is heavily affected by mining activities in their headwaters. It has been proven that the influence of anthropogenic activity is reflected in these overbank deposits by variations in Pb concentrations that, in general, correlate with shifts in the ²⁰⁶Pb/²⁰⁷Pb ratio. Rivas profile (downstream of Madrid) was found to be the most anthropogenically influenced site. The sediments within this profile which were recently deposited (170 ± 40 years BP) have the least radiogenic signatures. ²⁰⁶Pb/²⁰⁷Pb ratios ranged between 1.1763 and 1.1876 indicating significant contributions of anthropogenic Pb. In contrast, profiles upstream of Madrid possess an average ²⁰⁶Pb/²⁰⁷Pb ratio of 1.2272. It is difficult to clearly identify the most prominent source as the sediments appear to be characterized by an input from several sources. The floodplain profiles in the Tinto–Odiel basin exhibit uniform ²⁰⁶Pb/²⁰⁷Pb ratios ranging from 1.1627 (Odiel river) to 1.1665 (Tinto river). These ratios are similar to the ones possessed by sulphide ores in the area and differ from the ratios of other nonmineralized formations in the basin, indicating that mining activities are the primary, if not sole, source of Pb to the sediments.     

Radon in indoor air of primary schools: determinant factors,their variability and effective dose

Radon is a radioactive gas, abundant in granitic areas, such as in the city of Porto at the north-east of Portugal. This gas is a recognized carcinogenic agent, being appointed by the World Health Organization as the leading cause of lung cancer after smoking. The aim of this preliminary survey was to determine indoor radon concentrations in public primary schools, to analyse the main factors influencing their indoor concentration levels and to estimate the effective dose in students and teachers in primary schools. Radon concentrations were measured in 45 classrooms from 13 public primary schools located in Porto, using CR-39 passive radon detectors for about 2-month period. In all schools, radon concentrations ranged from 56 to 889 Bq/m³ (mean = 197 Bq/m³). The results showed that the limit of 100 Bq/m³ established by WHO IAQ guidelines was exceeded in 92 % of the measurements, as well as 8 % of the measurements exceeded the limit of 400 Bq/m³ established by the national legislation. Moreover, the mean annual effective dose was calculated as 1.25 mSv/y (ranging between 0.58 and 3.07 mSv/y), which is below the action level (3–10 mSv). The considerable variability of radon concentration observed between and within floors indicates a need to monitor concentrations in several rooms for each floor. A single radon detector for each room can be used, provided that the measurement error is considerably lower than variability of radon concentration between rooms. The results of the present survey will provide useful baseline data for adopting safety measures and dealing effectively with radiation emergencies. In particular, radon remediation techniques should be used in buildings located in the highest radon risk areas of Portugal. The results obtained in the current study concerning radon levels and their variations will be useful to optimize the design of future research surveys.     

Effect of two TiO2 nanoparticles on the growth of unicellular green algae using the OECD 201 test guideline: influence of the exposure system

This work aimed at assessing the influence of different exposure systems to perform the commonly used OECD 201 freshwater algal growth inhibition test in the context of nanoparticles hazard assessment. Two distinct TiO₂ nanoparticles were considered and three different exposure systems were investigated: Erlenmeyers flasks and 24-well microplates (both using an orbital shake system), and an alternative system using cylindrical vials and magnetic stirring. All three systems are in accordance with the OECD 201 test guideline recommendations. We concluded that the exposure systems applied to achieve the test can substantially affect the ecotoxicological results and the subsequent calculated ECx. The selected systems influenced both the interaction between algal cells and TiO₂ nanoparticles as well as the growth inhibition recorded. Disparities in ecotoxicity relative to the TiO₂ nanoparticles tested were also observed and are finally discussed.     

Identification of a floral-derived kairomone for currant clearwing, <Emphasis Type="Italic">Synanthedon tipuliformis</Emphasis>

The currant clearwing Synanthedon tipuliformis (Clerck) (Sesiidae) is a worldwide pest of black currants, Ribes nigrum. This moth has been observed to feed on nectar of inflorescences of Canada thistles, Cirsium arvense (L.) Scop. This work was undertaken to identify floral compound(s) produced by Canada thistles inflorescences that mediate the response of the currant clearwing. Floral volatiles were collected during the day and analysed by coupled gas chromatography/electroantennographic detection (GC/EAD) and gas chromatography/mass spectrometry (GC/MS). Three compounds consistently elicited EAD response from moth antennae and were identified by GC/MS as phenylacetaldehyde, methyl salicylate and dimethyl salicylate. When the compounds were tested individually or in various combinations in field trapping experiments, a 3-component blend attracted the largest number of female and male currant clearwings. Subsequent field trapping experiments were conducted to determine the optimal attraction dose for the ternary blend using three loadings of 1, 10 and 100 mg loaded into a polyethylene sachet. The highest catches were in traps baited with the 100 mg loading. In all trials, males and mated females were caught in significant numbers, while very low numbers of virgin females were found in the traps. In recent years the efficacy of mating disruption against currant clearwing has been reported as declining. The new kairomone blend identified in this study can be used with the sex pheromone to provide an effective control option for this important pest.