Measurement of elements by portable x-ray fluorescence spectrometry for the study of adsorption processes: the case of Pb2+adsorption on soybean straw biochar.

This study evaluated the reliability of portable X-ray fluorescence (pXRF) in Pb2+adsorption kinetics and isotherm experiments using soybean straw biochar. The research aimed to compare pXRF results with those obtained through traditional atomic absorption spectrometry (AAS). Soybean straw biochar, produced at 400 °C, was employed as the adsorbent for Pb2+. The efficiency of adsorption was assessed using Langmuir and Freundlich models. The kinetics of Pb2+adsorption was analysed through pseudo-first-order and pseudo-second-order models. The pseudo-second-order model described the kinetics of Pb2+adsorption on biochar better than the pseudo-first order model. Importantly, the pXRF technique demonstrated comparable results to those of AAS, making it a reliable and resource-efficient method for studying Pb2+kinetics. The results of the isotherm analyses fit the Langmuir model, indicating a desirable and irreversible adsorption of Pb2+on biochar. PXRF measurements on biochar allowed simultaneous observations of Pb2+adsorption and K+and Ca2+desorption, highlighting ionic exchange as the primary adsorption mechanism. In conclusion, our results showcased the applicability of pXRF for Pb+2adsorption studies in biochars, offering a valuable alternative to traditional methods. The findings contribute to the understanding of biochar as an effective adsorbent for heavy metals, emphasizing the potential of pXRF for cost-effective and efficient environmental research. In this study, we present a novel and detailed procedure that will allow other researchers to continue their studies on Pb2+adsorption on biochar or similar matrices, significantly reducing the resources and time used and enabling the simultaneous study of the behavior of other ions participating in the process.

PM10 correlates with COVID-19 infections 15 days later in Arequipa, Peru.

The emergence of COVID-19 and the spread of this novel disease around the world in 2020 has entailed several cultural changes; some of those changes are positive for the environment, such as the decrease in the concentration of atmospheric particulate matter. We compared the concentrations of PM2.5 and PM10 recorded in October and November 2019 (pre-pandemic period) with the concentrations recorded from May to October 2020 (pandemic period) in the city of Arequipa, Peru. A significant decrease in the concentration of PM2.5 (less than 21.0%) and PM10 (less than 21.5%) was observed on Sundays, when population movement was strongly restricted. First, we observed a significant correlation between PM2.5 and PM10 concentration in the atmosphere and the number of infections reported in Arequipa, Peru. However, when we removed the data of Sundays from the database, these correlations were no longer significant. Subsequently, we correlated PM2.5 and PM10 concentrations with the number of COVID-19 infections on the same day and up to a 20-day delay and found that from day 15 to day 18, PM10 concentration was significantly correlated with COVID-19 infections, suggesting that SARS-CoV-2 might circulate attached to the coarse particle (PM10) and that this fraction would act as infection vector. However, these results may reflect other factors, such as social or economic factors that could explain the dynamics of infection in Arequipa, Peru. Further research is needed to better understand the dynamics of the SARS-CoV-2 pandemic.

Pb tolerance and accumulation capabilities of Bidens pilosa L. growing in polluted soils depend on the history of exposure.

Phytoremediation, especially phytoextraction, is a good alternative for remediation of soils contaminated with heavy metals. This method requires selection of species for their tolerance, high accumulation levels in harvestable parts, and high biomass production. Bidens pilosa L. has been reported as tolerant to and potentially hyperaccumulator of several heavy metals, including Pb, but with variable results in terms of effectiveness. The aim of this study was to analyse the intra- and interpopulation variability of B. pilosa in response to Pb in individuals from two populations: one historically exposed to Pb and another with no history of exposure. Bidens pilosa L. presented tolerance to Pb pollution in soil, evidenced in a higher survival rate, a better antioxidant response, and an efficient reduction in cell membrane damage mainly due to history of exposure. The period of exposure (30 years) was not long enough to obtain a B. pilosa population that provides seeds for phytoextraction projects, since the average value of total extraction was relatively low. Collecting seeds from a historically exposed population will provide some suitable individuals with Pb accumulation and translocation capabilities, but not a sufficient amount to conduct a large phytoremediation project. The individual accumulator profile of B. pilosa is not related to the physiological behaviour or to the Pb entry into the vascular bundle in root, but to the incorporation of other heavy metals that are micronutrients.

Health risk assessment of polycyclic aromatic hydrocarbons (PAHs) adsorbed in PM2.5 and PM10 in a region of Arequipa, Peru.

The concentrations of PM2.5 and PM10, as well as those of the PAHs bound to these particles, were quantified at four sites in the region of Arequipa, Peru, during the year 2018. These samples were collected with high volume samplers, and the concentrations of the PAHs were quantified by liquid chromatography (HPLC). The values found for PM2.5 and PM10 at all the sampling sites in Arequipa exceeded the norms established in Peru (50 µg m-3 annual average value for PM10 and 25 µg m-3 annual average value for PM2.5), with the industrial site presenting the highest values of particulate matter (PM10 max = 235.1 µg m-3; PM2.5 max = 218.4 µg m-3). With respect to seasonality, in the cold season (winter), the concentration of particles was higher compared to the other seasons. Concerning the PAHs, it was found that these had the highest concentrations at the industrial site, followed by the site with high vehicular traffic, with both these sites differing significantly from the rural sites. In addition, at the industrial and high traffic sites, there was a predominance of PAHs with 5 and 6 rings, whereas at the rural sites, PAHs with fewer rings predominated. Finally, the calculated values of lifetime lung cancer risk also revealed a difference between sites with marked emission sources, where irrigation was considered moderate, and the rural sites, where irrigation was considered low. This demonstrated that people living at sites with mobile sources and/or industries had a higher cancer risk compared to the inhabitants of rural sites.

Occurrence of persistent organic pollutants in air at different sites in the province of Córdoba, Argentina.

The occurrence of persistent organic pollutants (POPs) and polycyclic aromatic hydrocarbons (PAHs) in the atmosphere of six sites with different emission sources in the province of Córdoba, Argentina, was analyzed. The sites included urban, industrial, agricultural, and mountain areas. Samples were collected using passive air samplers (PAS) consisting of polyurethane foam disks (PUF). Samples were analyzed for 12 PAHs, 31 polychlorinated biphenyls (PCBs), 12 organochlorine pesticides (OCPs), and 11 polybrominated diphenyl ethers (PBDEs). The concentrations of PAHs in the atmosphere were elevated at urban sites and were even higher at the industrial site. With respect to OCPs, it was observed that the concentrations of endosulfan were greater at the agricultural site (AGR) (416 ± 4 pg m-3). For hexachlorocyclohexanes (HCHs), only the alpha isomer was detected and there were minimal differences between the different sampling sites (5.9-13.3 pg m-3). In the case of dieldrin, the highest concentrations (33.6 pg m-3) were found at the mountain site, which may have been due to its use for insect control. Although heptachlor epoxide was not detected, the concentration of heptachlor was significantly higher at the agricultural and downtown sites (∼ 3.6 pg m-3). Regarding DDTs, the isomers p,p'-DDT and p,p'-DDE showed the highest concentrations at the mountain site (ΣDDT 120 ± 12 pg m-3) and downtown site (ΣDDT 157 ± 62 pg m-3). The relationship between the isomers suggested that at the downtown site, the contribution of this pesticide to the environment was recent, probably for the control of diseases vectors. The congener pattern of PBDEs was dominated by BDE-47, and BDE-99 at all sites, with the downtown site having the highest concentrations of compound esters (ΣPBDEs 118 ± 38 pg m-3). Finally, high concentrations of PCBs were found at the industrial site (ΣPCBs 1677 ± 134 pg m-3), and the predominating homologs were 5-Cl and 6-Cl, in contrast to the other sites where PCBs were dominated by 3-Cl and 4-Cl. This is the first study of POPs carried out in the province of Córdoba.

Elemental composition of PM2.5 in the urban environment of San Juan, Argentina.

This study contributes to the current knowledge about air pollution in the province of San Juan, Argentina. Sampling was carried out to measure the fine particulate matter in the atmosphere (PM2.5) of the city of San Juan. PM2.5 was collected continuously during the winter and spring seasons of 2014 and 2015, and the concentrations of 14 elements (Pb, Ca, K, Cd, Ni, Cr, Mn, V, Cu, Ti, Ba, Co, Sr, and Fe) were determined in PM2.5 filters using the technique of X-ray fluorescence by synchrotron radiation (SR-XRF). The results revealed that PM2.5 presented annual and seasonal variations, showing a higher concentration during the winter seasons. In addition, for the elements quantified in the filters, a multivariate analysis (Positive Matrix Factorization) was performed to identify the main sources of emission of these elements in the study area, with a series of components being obtained that corresponded to their compositions, which were assigned physical meanings. The first factor, which was the most important in contribution of the sum of the measured elements (45%), was determined mainly by the elements K, Ti, V, Mn, and Fe, which came predominantly from soil particles. The second factor contributed 30% to the measured species in PM2.5, with higher Ba and Zn content perhaps being related to emissions from vehicular traffic. Finally, the third factor, in which Pb, Cr, and Ca predominated, may be an indicator of industrial activity and contributed 25% of the sum of the measured elements of PM2.5. The results of this study provide the first PM composition database in the province, and this can now be used in the development of mitigation and prevention programs.

Suitability of Tillandsia usneoides and Aechmea fasciata for biomonitoring toxic elements under tropical seasonal climate.

Aechmea fasciata was evaluated for the first time as a biomonitor of toxic elements, in comparison to the biomonitoring capacity of Tillandsia usneoides, a well-established biomonitor bromeliad species. Plants of both species were exposed to air pollutants from industrial, urban, and agricultural sources, under the tropical seasonal climate, from June/2011 to April/2013, in five sites of São Paulo State, Brazil, for 8 consecutive exposure periods of 12 weeks each. The levels of essential and non-essential elements, including trace metals, were quantified at the end of each exposure. T. usneoides and A. fasciata indicated N, Fe, Zn, Co, Cr, and V as air contaminants in the studied sites, during wet and dry seasons and both species were recommended for qualitative biomonitoring. Concentration levels of N, Ca, S, Fe, Zn, Cu, B, Co, and Ni were significantly higher in T. usneoides than in A. fasciata. However, A. fasciata showed a higher effective retention capacity of Ni, Pb, V, Cu, Fe, Cr, and Co during field exposure, as indicated by the estimate of enrichment factor relative to basal concentrations. This species is more suitable for detecting the atmospheric pollution level of those metals than the T. usneoides. Both species indicated adequately the seasonal differences in the pollution levels of several elements, but T. usneoides presented higher ability for biomonitoring the spatial variations and for indicating more properly the sources of each element in the studied region than the A. fasciata.

Assessment of human health risk related to metals by the use of biomonitors in the province of Córdoba, Argentina.

The evaluation of metal contents in the environment is of vital importance for the assessment of human exposure. Thus the species Usnea amblyoclada, Ramalina celastri and Tillandsia capillaris were tested as bioaccumulators of transition metals in the urban area of Córdoba city, Argentina. The level of metals on biomonitors was compared to that of total deposition samples. All three species discriminated zones within the urban area of Córdoba city with different pollution levels; they revealed high levels of Zn in the downtown area and confirmed high levels of some transition metals in an industrial area. The correlation analysis revealed that the lichen R. celastri had the highest correlation rates with total deposition samples, suggesting it is a valuable biomonitor of atmospheric pollution. A significant relationship was also observed between respiratory diseases in children and the contents of metal accumulated in R. celastri and T. capillaris, indicating their usefulness when assessing human exposure to metals.

Assessment of heavy metal accumulation in two species of Tillandsia in relation to atmospheric emission sources in Argentina.

The ability of Tillandsia capillaris Ruiz and Pav. f. capillaris and Tillandsia permutata A. Cast. to accumulate heavy metals was evaluated in relation to potential atmospheric emission sources in Argentina. The sampling areas (n=38) were chosen in the province of Córdoba, located in the center of Argentina, and categorized according to land use, anthropogenic activities and/or distance to potential heavy metal emission sources. In each sampling site, pools of 40-50 individuals of each species were made from plants collected along the four cardinal directions. The concentrations of V, Mn, Fe, Co, Ni, Cu, Zn, Pb and Br of these samples were measured by Total Reflection X-Ray Fluorescence (TXRF) analysis with Synchrotron Radiation. Each species was submitted to a cluster analysis in order to discriminate different groups of heavy metals as tracers of natural or anthropogenic sources. A Contamination Factor (CF) was calculated using the concentrations of the elements in each sample compared to their concentrations in the control samples. Finally, the rank coefficients of correlation between the CFs and the categorical variables characteristic of each site (land use and anthropogenic load) were analyzed. A positive correlation was found for T. capillaris between the CFs of V, Mn, Co, Ni, Cu and Zn and the urban-industrial category, whereas the CF values for Zn and Pb were positively correlated with the road category. In T. permutata there was a positive correlation between the CF of Zn and the urban-industrial category and the CF of Pb with the road category. We therefore conclude that T. capillaris is a more efficient metal accumulator in passive biomonitoring studies.

The role of urban air pollutants on the performance of heavy metal accumulation in Usnea amblyoclada.

Lichens incorporate heavy metals according to a selectivity sequence; therefore, their uptake rate can be affected when elements with a high affinity for cell wall exchange sites or that provoke harmful alterations to the metabolism of lichen thalli are present in the environment. The aim of this study was to examine the effect of urban pollutants on the accumulation of some heavy metals in Usnea amblyoclada. Lichen samples were transplanted for 1 month to both a polluted and a nonpolluted area in Cordoba, Argentina. They were then collected and soaked in tridistilled water or in solutions containing different concentrations of Cu, Ni, Pb, and Zn salts. The uptake of Cu2+, Ni2+, Zn2+, and Pb2+, and other parameters indicative of lichen damage were measured in all the lichen samples. The thalli retrieved from the polluted area showed significant increases in both the malonaldehyde content and the electrical conductivity of the water in which they had been immersed. These results indicate that the atmospheric pollutants could be responsible for the significant damage to the lichen's cellular membranes, thus altering several mechanisms related to the uptake of heavy metals. Both the area of transplantation and the concentration of the metallic solutions had significant effects on the levels of Cu, Ni, and Pb measured in lichen thalli; however, no significant differences were observed in Zn concentrations. The highest uptakes corresponded to Pb and Cu, suggesting that they probably have a higher affinity with the lichen cell wall exchange sites. This study confirms the fact that, although lichens can be useful biological indicators, the physiological mechanisms involved in metal uptake should be carefully analyzed. Therefore, when estimating the heavy metal content of an environment, the competitive mechanism for cation uptake should be considered especially in areas where the presence of high levels of metals with a strong binding affinity is suspected. The presence of secondary products in the lichens could be responsible for the selective uptake of cations and for a possible tolerance to their presence.