323,107 research outputs found
Oxidative potential sensitivity to metals, Br, P, S, and Se in PM10 samples: New insights from a monitoring campaign in Southeastern Italy
No full textDifferent analytical techniques were used in this work to investigate the relationships between oxidative potential (OP) and metal, Br, P, S, and Se concentration in PM10 samples. Dithiothreitol and ascorbic acid acellular assays were used to determine the oxidative potential (OP) in PM10 samples. The particle-induced X-ray emission technique was used to estimate the mass concentration of specific chemical elements. PM10 samples were collected in Lecce, a coastal site of the Central Mediterranean away from large sources of local pollution. Both winter and spring samples were analyzed to study the seasonal dependence of the relationships between OP values and chemical element concentrations. The Redundancy Discriminant Analysis (RDA) was applied to (volumeand mass-normalized) OP values as response variables and metal, Br, P, S, and Se concentrations as explanatory variables. RDA triplots allowed to visualize the main relationships between PM10 OP values and corresponding chemical element concentrations. Spearman correlation coefficients were also used to investigate the relationships between OP values and metal, Br, P, S, and Se concentrations, besides comparing RDA outcomes. The integrated approach based on two different techniques allowed to better highlight the potentially harmful effects associated with specific metals and other chemical elements in PM10 samples
Soil and Foliar Applications of Wood Distillate Differently Affect Soil Properties and Field Bean Traits in Preliminary Field Tests
No full textNatural products such as wood distillate (WD) are promising alternatives to xenobiotic products in conventional agriculture and are necessary in organic farming. A field study gave insight into the effectiveness of WD applied as foliar spray (F-WD), soil irrigation (S-WD), and their combination as growth promoters for field beans. The soil fertility and quality parameters, plant growth, nutrient uptake, and resource partitioning within plants were evaluated. In a pot trial, we tested the effect of S-WD on root nodule initiation and growth. S-WD increased DOC and microbial biomass by approximately 10%, prompted enzyme activities, and increased nitrate and available phosphorus in soil, without affecting the number and growth of nodules in field beans. In contrast, the F-WD slightly reduced the DOC, exerted a lower stimulation on soil enzymes, and lowered the soil effect in the combined distribution. In field beans, the F-WD reduced the stem height but increased the number of pods per stem; S-WD increased the N and P concentrations of leaves and the N concentration of the pods. Moreover, all WD treatments retarded plant senescence. The WD revealed itself to be promising as a growth promoter for grain legumes, but further research is needed to understand the interference between the combined soil and foliar applications
Weekly cycle assessment of PM mass concentrations and sources, and impacts on temperature and wind speed in Southern Italy
No full textA methodology to detect the weekly cycle impact of the particulate matter (PM), and PM sources on the nearsurface temperature and wind speed is discussed in the paper. Chemically-speciated PM10 and PM2.5 samplesare analyzed to detect the weekly cycle of both the PM mass concentrations and the PM sources identified by thePositive Matrix Factorization technique. The average percent departure (APD) of the PM mass concentrationfrom the mean value calculated for each day of the week shows that a positive (higher values during midweek)and a negative (higher values during weekend) weekly cycle characterizes the PM10 and PM2.5 mass con-centrations in Autumn-Winter (AW, September–February) and Spring-Summer (SS, March–August), respectively.The westerly transport of pollution seems to have a role on the negative PM weekly cycle found in SS. Theanalysis of the six identified aerosol sources indicates that in SS the mixed anthropogenic and the reacted dustsources likely impact the PM10 negative weekly cycle and that the mixed anthropogenic source likely impactsthe PM2.5 negative weekly cycle. The mixed anthropogenic and soil dust sources likely affect in AW the positiveweekly cycle of the PM10 mass concentration. Both sources in addition to the reacted dust source seem to affectthe PM2.5 mass concentration in AW. The APD analysis of the temperature (T) and wind speed (WS) at thesurface from measurements co-located in space and time with the PM ones reveals that the WS and T values arecharacterized by a negative weekly cycle in AW. Conversely, in SS, the WS-APD value decreases on Sunday andthe T-APD values increase in the second half of the week. These last results likely give evidence of the PM impacton the near-surface temperature and wind speed at the study site
High resolution chemical stratigraphies of atmospheric depositions from a 4 m depth snow pit at dome C (East Antarctica)
No full textIn this work, we present chemical stratigraphies of two sampling lines collected within a 4 m depth snow pit dug in Dome C during the Antarctic summer Campaign 2017/2018, 12 years after the last reported snow pit. The first sampling line was analyzed for nine anionic and cationic species using Ion Chromatography (IC); the second sampling line was analyzed for seven major elements in an innovative way with Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) after sample pre-concentration, allowing the study of deposition processes of new markers especially related to crustal source. This coupled analysis, besides confirming previous studies, allowed us to investigate the depositions of the last decades at Dome C, enriching the number of the detected chemical markers, and yielding these two techniques complementary for the study of different markers in this kind of matrix. As a result of the dating, the snow layers analyzed covered the last 50 years of snow depositions. The assessment of the accumulation rate, estimated about 9 cm yr−1, was accomplished only for the period 1992–2016, as the eruption of 1992 constituted the only tie-point found in nssSO42− depth profile. Na, the reliable sea salt marker, together with Mg and Sr, mainly arose from marine sources, whereas Ca, Al and Fe originated from crustal inputs. Post-depositional processes occurred on Cl− as well as on NO3− and methanesulfonic acid (MSA); compared to the latter, Cl− had a more gradual decrease, reporting a threshold at 2.5 m for the post-depositional process completion. For NO3− and MSA, instead, the threshold was shallower, at about 1 m depth, with a loss of 87% for NO3− and of 50% for MSA
Diffusive author(s), cohesive author: Analysis of S/N (1994)
No full textThis study indicates the ways in which various aspects of the author(s) are brought forth in Dumb type’s performance art, the S/N production. Previous research has suggested a non-hierarchical organization of Dumb type and the absence of a “privileged author” in Dumb type’s collaborative work, S/N. However, the results that I have investigated from member’s interviews on the creative process of S/N along with my analysis of the recorded images of S/N, indicate a different aspect of the author(s). First, S/N was created through, so to speak, the collective ideas of the members of Dumb type. Further, S/N has at least nine quotations from previous performances, installations, and printed writings, besides the work-in-progress technique. Explicating one of the “author functions” as given by Michel Foucault, each text has plural subjects of the author. However, it has been revealed from members’ interviews that Teiji Furuhashi had a decision-making role in selecting the members’ ideas within the performance. Since then, S/N has had plural subjects of creation; however, Furuhashi is one of the subjects of creation along with the “privileged author.” S/N has plural authors (diffusive authors) yet at the same time, it has a “privileged author,” Teiji Furuhashi (cohesive author)
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Airborne bacteria structure and chemical composition relationships in winter and spring PM10 samples over southeastern Italy
No full textThe Redundancy Discrimination Analysis (RDA) and Spearman correlation coefficients were used to investigate relationships between airborne bacteria at the phylum and genus level and chemical species in winter and spring PM10 samples over Southeastern Italy. The identification of main chemical species/pollution sources that were related to and likely affected the bacterial community structure was the main goal of this work. The 16S rRNA gene metabarcoding approach was used to characterize airborne bacteria. Seventeen phyla and seventy-nine genera contributing each by mean within-sample relative abundance percentage > 0.01% were identified in PM10 samples, which were chemically characterized for 33 species, including ions, metals, OC, and EC (organic and elemental carbon, respectively). Chemical species were associated with six different pollution sources. A shift from winter to spring in both bacterial community structure and chemical species mass concentrations/sources and the relationships between them was observed. RDA triplots pointed out significant correlations for all tested bacterial phyla (genera) with other phyla (genera) and/or with chemical species, in contrast to correlation coefficient results, which showed that few phyla (genera) were significantly correlated with chemical species. More specifically, in winter Bacillus and Chryseobacterium were the only genera significantly correlated with chemical species likely associated with particles from soil-dust and anthropogenic pollution source, respectively. In spring, Enterobacter and Sphingomonas were the only genera significantly correlated with chemical species likely associated with particles from the anthropogenic pollution and the marine and soil-dust sources, respectively. The results of this study also showed that the correlation coefficients were the best tool to obtain unequivocal identifications of the correlations of phyla (genera) with chemical species. The seasonal changes of the PM10 chemical composition, the microbial community structure, and their relationships suggested that the seasonal changes of atmospheric particles may have likely contributed to seasonal changes of bacterial community in the atmosphere
Oxidative Potential Dependence on the Chemical Composition of PM2.5 and PM10 Samples
No full textEpidemiological and toxicological studies have shown that the exposure to ambient particulate matter (PM) leads to adverse health effects in humans. The most accredited pathophysiological mechanisms involve several oxidative mechanisms leading to high concentrations of reactive oxygen species (ROS) in vivo. Such an imbalance toward a ROS excess translates into numerous health outcomes. Two common acellular techniques based on low-cost spectrophotometric UV-Vis measurements were used in this study to assess the oxidative potential (OP) of PM10 and PM2.5 samples. One is the dithiothreitol (DTT) assay, where DTT acts as a surrogate for biological reducing agents owing to its two sulfhydryl groups. The other assay is based on the ascorbic acid (AA), that is a physiologically antioxidant found in lung fluid. In order to investigate the association of the measured oxidative responses with the PM chemical composition, inorganic and organic ions, metals, organic and elemental carbon were quantified in simultaneously collected PM2.5 and PM10 samples.
The DTT and AA assays provided DTT-OP and AA-OP responses very similar in mean values and variability range, but different in association with chemical species and seasonal variation. More specifically, the AA-OP was strongly positively correlated with the main tracers of traffic and/or combustion emissions in Autumn-Winter (AW). In Sprin-Summer (SS) AA-OP was mainly correlated with species related with secondary aerosol and resuspended soil from vehicular traffic and/or long-range transport of Sahara dust. The DTT-OP of AW samples was well correlated with tracers of the resuspended reacted dust source, vehicle-related metals, and EC and OC associated with combustion sources. Conversely, in SS the DTT-OP of SS was correlated only with NH4+,Cu, EC and POC.
In conclusion, our study has highlighted the differences between the responses of the two commonly utilized DTT and AA assays to assess aerosol OP in both PM10 and PM2.5. Moreover, paper’s results have confirmed that the toxicity of ambient PM is a multifaceted phenomenon caused by a multiplicity of redox-active species and depending on the activity and concentration level of the individual components as well as on possible interaction/synergic effects
Chemical characterisation of the last 250 years of snow deposition at Talos Dome (East Antarctica)
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