Pseudo-total Concentrations Research Articles

Geochemical Background for Potentially Toxic Elements in Forested Soils of the State of Pará, Brazilian Amazon

The objectives of this study were to establish geochemical background values of aluminum (Al), iron (Fe), arsenic (As), barium (Ba), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), manganese (Mn), nickel (Ni), lead (Pb), vanadium (V), and zinc (Zn) for eastern Amazon soils and to assess the relationship between soil chemical and granulometric attributes using univariate and multivariate procedures. Samples from the topsoil (0–0.2 m) were collected in several areas with minimal or no human intervention. Pseudo total concentrations of potentially toxic elements were extracted via acid digestion and quantified via inductively coupled plasma optical emission spectrometry (ICP-OES). The results revealed that the soils present high acidity, low levels of cations and organic carbon, and highly heterogeneous geomorphological characteristics. The elements Fe (9300 mg kg−1) and Al (8200 mg kg−1) showed the highest mean concentrations in the study, while As (0.8 mg kg−1) and Cd (0.1 mg kg−1) presented the lowest levels. The results of this study indicate that the 90th percentile can be used to formalize quality reference values for the State of Pará and that the 98th percentile can be considered for areas rich in mineral deposits.

The influence of agricultural soil preparation methods on the pseudo-total element content determined by ICP-OES

The influence of agricultural soil preparation methods on the pseudo-total element content determined by ICP-OES

Sediment quality of the Ridracoli fresh water reservoir in Italy: Insights from aqua regia digestion and sequential extractions

The inter-element relationships and the forms in which metals exist strongly influence their mobility and, in turn, have a signature on the environment and human health. Located in the northern Apennines within the Emilia-Romagna region, the Ridracoli artificial lake is one of Italy's most important reservoirs that provides drinking water for about one million people. This work characterized the reservoir sediments by ICP-MS after aqua regia digestion (ARD), comparing the limits by law to assess environmental compliance and XRF data from the same sample-set taken as total concentrations. The Degree of Extraction (DE) from pseudo-total concentrations of ARD analysis allows assessing elements mobility and the associated environmental risk. Principal Component Analysis (PCA) on the obtained data helped to investigate inter-element relationships better; for example, we observed carbonate-sourced sediments, many trace elements (e.g., Ni, Zn) linked to FeMn oxyhydroxides, the importance of the grain size in elements distribution, and the central role of the organic matter in element partitioning. In addition, a Sequential Extraction Procedure (SEP) was applied to the sediment samples to understand the partitioning of many analytes, including Potentially Harmful Elements (PHE) such as Fe, Mn, Cu, Cr, Ni, Pb, and Zn. The results indicated that the most easily mobilized forms were predominant in the area near the dam, in correspondence to sediments affected by the formation of a seasonal anoxic layer.

Assessing the risk of toxic metals contamination and phytoremediation potential of mangrove in three coastal sites along the Red Sea

Assessing toxic metals (TMs) contamination and phytoremediation potentiality in coastal mangrove lagoons is needed for applying sustainable management of this ecosystem. Consequently, here we determined the pseudo-total content of TMs in the sediments and mangrove plants (leaves, stems, aerial roots, and fine roots) collected from Al-Shuaiba, Yanbu, and Jeddah lagoons, along the coast of Red Sea. The contamination degree was assessed using different indices and the potentiality of mangroves for TMs phytoremediation was determined. The average total metals content (mg kg−1) in the sediments ranged from 1806 to 9580 for Fe, 65 to 195 for Mn, 3.9 to 25.9 for Cu, 5.5 to 16.4 for Zn, 0.09 to 0.42 for Cd, 8.9 to 20.9 for Cr, 32.8 to 37.9 for Ni, and from 0.69 to 6.7 for Pb. The sediments of Yanbu site contained the highest content of all metals (except for Cu), while Al-Shuaiba sediments contained the lowest values. The contamination factor (CF) showed that the sediments of Yanbu and Jeddah suffer from high and moderate contamination degree of Cd. These sites suffer from moderate grade of Ni contamination. The CF values of Fe, Mn, Cr, Cu, and Zn in the three sites were lower than unity, which show low contamination degree. Iron, Cr, Cu, Ni, Pb, and Zn were concentrated in the fine roots, while Cd was concentrated in the stems. Mangrove plants at Yanbu site contained significantly higher content of all metals than the grown plants in Jeddah and Al-Shuaiba sites, which can be explained by the high metal content in the sediments and the anthropogenic metal sources such as the petrochemical industries, and the industrial and municipal wastewater discharged into this site. Sediment-to-plant transfer coefficients values were higher than unity, which indicate that the mangrove plants have the potential to accumulate the metals. The results highlight a potential risk at Yanbu and Jeddah sites and may help for applying sustainable trials for phyto-management of these lagoons.

Iron hazard in an impacted estuary: Contrasting controls of plants and implications to phytoremediation

Due to its abundance and role as a micronutrient for plants iron (Fe) is rarely perceived as a contaminant. However, in redox active environments, Fe bioavailability increases sharply representing an environmental risk. In this study, a recent catastrophic mining dam failure is used as a field framework to evaluate the role of wetland plants on Fe biogeochemistry and assess their potential for phytoremediation programs. To achieve these objectives, a Fe geochemical partitioning and the concentration of Fe in different plant compartments (iron plaque on root surfaces, roots, and leaves) were determined in two sites vegetated by different wetland species. Soils exhibited contrasting Fe biogeochemical dynamics. Lower pseudo-total contents and more reactive Fe oxides were observed in the soil vegetated by Typha domingensis. Iron plaque was present on both species but more concentrated in Fe in T. domingensis. T. domingensis showed Fe shoot concentrations (3874 mg kg−1) 10-fold higher than in Hibiscus tiliaceus, which prevented Fe absorption through iron plaque formation and root accumulation. In conclusion, contrasting biogeochemical effects on Fe (e.g., rhizosphere acidification) lead to different phytoremediation abilities. T. domingensis showed a high potential for Fe phytoremediation on sites affected by Fe-enriched wastes and should be tested in assisted phytoremediation approaches.

Quality reference values for trace metals in Podzols, Ferralsols, and Acrisols of Brazilian Atlantic rainforest

In tropical coastal forest ecosystems, human activities spread rapidly. It is, therefore, necessary to define soil quality. For this, the determination of the natural content of trace metals is an essential step. This study aims to understand the distribution of trace metals in the main soils of tropical coastal rainforest ecosystems: Ferralsols, Acrisols, and Podzols, in Bahia state, Brazil. After morphological, chemical, and physical characterization and classification of the soils, the concentration of trace metals was investigated both in soil profiles and in surface composite samples (national guideline recommendation), in five locations for each soil class. The soils were classified as Geric Ferralsol, Haplic Acrisol, Chromic Acrisol, and Ortsteinic Carbic Albic Endogleyic Podzol. Concentrations of metals differed significantly between soil classes. Even under tropical rainforest climate during soil formation, the parent rock material still influences geochemistry. Al, Fe, Mo, Ni, V, and Zn accumulate in Ferralsols, while Ba, Co, Cr, Cu, and Mn accumulate in Acrisols. In the Podzols, metals highly accumulate in B spodic horizon. The data highlights that composite sampling strictly based on soil layers and not horizons (as the national guideline recommends) can cause significant misinterpretations. Instead, the multivariate regression models provided consistent data, accurately predicting the pseudo-total concentrations of trace metals in individual soil samples. The regression method is fast and low cost and provides a reliable geochemical baseline for the definition of reference values.

Dust Characterization and Its Potential Impact during the 2014–2015 Fogo Volcano Eruption (Cape Verde)

Fogo (Fogo Island) is the youngest and most active volcano of Cape Verde. The last eruption occurred in 2014–2015. Aiming to assess the dust sources that impacted the air quality during the present study period, fresh lava samples were collected, while Saharan dust intrusions and transport were modeled. Rooftop dust was also collected on the island dwellings and a mineralogical and chemical characterization was undertaken. Air quality monitors were used to obtain concentrations of atmospheric particulate matter (PM) and gaseous pollutants. The mineralogical constitution was assessed by XRD and Electron Microprobe. The pseudototal chemical concentration was performed by XRF, ICP-MS and SEM; the latter includes particles morphology. During the study, WRF-CHIMERE results showed the intrusion of desert dust which affected the air quality. Lava was classified as tephritic to basanitic, with high potassium content. The Pollution Load Index for rooftop dust was >1 in all samples, suggesting an enrichment. Higher values were found in dust size fraction <63 µm, with contamination factor pointing to high enrichment of As, Ni and Pb, and very high enrichment of Cd. The non-carcinogenic hazard estimated for children suggested that health problems may arise. The carcinogenic risk was above the target risk, mostly due to As > Pb > Co. Ingestion was the main exposure route. PM10 concentrations exceeded the 24-h mean of 50 µg/m3 recommended by WHO. Nevertheless, TVOCs displayed levels lower than guidelines. The highest levels of CO2 were recorded in more populated villages and farthest from the volcano.

Characterization of Mine Waste from a Former Pb–Zn Mining Site: Reactivity of Minerals During Sequential Extractions

An integrated mineralogical and chemical characterization approach was applied to different types of mine waste collected from the ancient Pb–Zn mining area of Plombières. The combination of different methods to determine (pseudo-)total element concentrations, sequential extractions, and quantitative mineralogical analysis provided detailed information on the reactivity of minerals in the waste, as well as the associated metal(loid) release under different experimental conditions. Lithium borate (LiBO2) fusion was not suited to determine total metal(loid) concentrations in the investigated mine waste samples, due to the incomplete dissolution of the samples, and the volatilization of As and Cd during the fusion. Because some elements were below detection limit of X-ray fluorescence spectrometry (e.g., Cd), aqua regia digestion was useful to complement the chemical sample characterization, bearing in mind that only pseudo-total concentrations could be determined. Galena (PbS) and its alteration products, cerussite and anglesite (PbSO4), were the main lead minerals associated with the mining waste. Because of the high cerussite (PbCO3) content of the investigated samples (2–5 wt%), Pb not only shows the highest potential for recovery from the mining waste, but it also poses the highest environmental and human health risk. Zinc minerals showed a lower reactivity towards the BCR sequential extraction (sphalerite, ZnS) or were less abundant (willemite, Zn2SiO4). Quantitative XRD analysis allowed for better evaluation of the incomplete dissolution of some minerals, improving the interpretation of the sequential extraction results.

Modern Dinoflagellate Cyst Abundance and Trace Metals as Biomonitoring Tools in a Tropical Bay in Brazil

Freitas, A.S.; Aguiar, V.M.C., and Baptista Neto, J.A., 2021. Modern dinoflagellate cyst abundance and trace metals as biomonitoring tools in a tropical bay in Brazil. Journal of Coastal Research, 37(6), 1247–1259. Coconut Creek (Florida), ISSN 0749-0208. The spatial distribution of the dinoflagellate cyst assemblages in 11 surface sediment samples collected in Guanabara Bay embayments and associated trace metals revealed the applicability of dinocysts as bioindicators of environmental conditions in estuarine systems. The surface sediment samples presented coarse to fine granulometry. The dinoflagellate cyst analysis followed the standard methodology through the elimination of carbonates and silica. Trace metals were extracted by the evaluation of 1 g of sediment plus a mixture of HNO3 and HCl in a microwave digestion system. Dinoflagellate cyst assemblages were dominated by Operculodinium centrocarpum, Spiniferites spp., and Lingulodinium machaerophorum. Trace metals (Cu, Zn, Pb, Cr, and Ni) showed variations at the different sampling points. The values obtained were Cu (6.7–82.8 mg kg–1), Zn (29.5–355.4 mg kg–1), Pb (18.3–86.2 mg kg–1), Cr (5.1–196.2 mg kg–1), and Ni (19.6–286.0 mg kg–1). Several samples showed high pseudototal concentrations of trace metals, which were above the natural concentrations found in nature. Statistical analysis showed a strong correlation between dinocysts species and some trace metals. Lingulodinium machaerophorum showed a high correlation with 4/5 analysed trace metals and is a eutrophication-sensitive species. However, Brigantedinium sp. presented a positive correlation with all trace metals analysed. The high frequency of L. machaerophorum cysts in all analysed samples associated with several trace metals is indicative of environmental eutrophication. The high availability of trace metals in the surface sediments of Guanabara Bay may be related to the untreated industrial wastes that are dumped directly into the bay.

Soil amendments affect the potential of Gomphrena claussenii for phytoremediation of a Zn- and Cd-contaminated soil

This study assessed the impact of inorganic and organic amendments upon zinc (Zn) and cadmium (Cd) availabilities in leachates collected from a Cd- and Zn-contaminated soil, while also evaluating the beneficial use of the tested amendments for decreasing metal availability, hence improving the phytoremediation potential of Gomphrena claussenii Moq. Plants were grown for 60 days in a Zn-smelting-affected soil containing 45,000 and 621 mg kg−1 of Zn and Cd, respectively (pseudo-total concentrations), after application of the following amendments: limestone, calcium silicate, sewage sludge, triple superphosphate, and red mud. Zinc and Cd availabilities in the soil decreased following the addition of limestone, calcium silicate, and red mud. These amendments were effective in reducing metal mobility and availability, positively affecting plant growth. Plants grown in the soil amended with limestone and calcium silicate accumulated Zn mainly in the roots, while Cd was translocated to plant shoots, with smaller amounts being detected in the roots. Reductions of Zn and Cd concentrations in the leachate were found by adding red mud, with this decrease for Zn being less pronounced compared to what was verified after the application of limestone and calcium silicate. Moreover, the use of red mud resulted in a higher Zn:Cd ratio in the leachate, which favored a greater absorption and transport of Zn from root to shoot. In conclusion, the tested soil amendments reduced the availability of excessive concentrations of Cd and Zn in naturally contaminated soil, which resulted in improved growth and survival of Zn- and Cd-tolerant G. claussenii plants, with the application of limestone, calcium silicate, and red mud - i.e., alkaline amendments - standing out as the best combinations with G. Claussenii when designing a strategy to achieve optimal phytoremediation.

Occurrence and distribution of heavy metals in the tissues of Physa acuta (D.) in relation to the contamination level of sediments from Boumerzoug wadi (Algeria)

The aim of this study was to assess the metallic contamination of sediments, and metals bioaccessibility via their distribution in the gastropod Physa acuta (Pulmonata). The concentrations of Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn in the soft tissue and shell of P. acuta, as well as in fresh surface sediments from the Boumerzoug wadi and its tributaries, northeastern Algeria, were determined by flame atomic absorption spectrophotometry. The samples were collected from ten sites on five occasions (May, September and December 2016, March and July 2017). Results showed that the trace metal mean concentrations in sediments, tissues and shells of the gasteropod, followed a decreasing order: Mn > Zn > Cr > Cu > Ni > Pb > Co > Cd. The pseudo-total contents of Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn in sediment were about 0.45 ± 0.43, 12.19 ± 2.49, 51.70 ± 19.82, 46.70 ± 39.60, 296.15 ± 105.83, 36.50 ± 10.93, 32.40 ± 9.10, and 186.72 ± 118.93 mg/kg dw, respectively. The concentrations of the metals studied in P. acuta were age dependent, with adults having significantly higher concentrations than juveniles. All heavy metal concentrations detected were higher in soft tissue with the lowest coefficient of variation than in shells for both adults and juveniles. The presence of a significant direct relationship between the Cd content in the sediment and in the soft tissues of P. acuta in both adults (r = 0.83; P < 0.01) and juveniles (r = 0.53; P < 0.01), and the high bioaccumulation factor observed make this gastropod a good indicator for the monitoring of freshwater sediment contamination by this metal.

Fractionation of heavy metals in soils cultivated with tobacco in Pinar del Río, Cuba

Knowledge of the presence of heavy metals in soils of agricultural areas is important to prevent their accumulation in cultivated plants. The objective of the present investigation was to evaluate the total concentrations and fractions of heavy metals Cd, Pb, Zn, Fe, Mn, Ni, Cu, Cr and Co in the tobacco-growing area of Pinar del Río, Cuba and their relationship with the physicochemical properties of soil. For the study, 59 samples of three types of soils were collected at 20 cm depth. The pseudo-total concentrations of metals in the soils are low and lower than the prevention values registered for Cuban soils. In general, the heavy metals studied present a high affinity for the most stable fractions of the soil, which means a low risk of transfer to the tobacco crop or accumulation in groundwater. The pseudo-total concentrations of heavy metals were low, below the alert values established for soils in the region. The heavy metals studied were mainly associated with the residual fraction, the second fraction with the highest association with metals was that linked to manganese and iron oxides. The principal component analysis showed that their main source is pedogenetic and that these elements are closely related to cation exchange capacity and calcium content.

Impact of copper mining wastes in the Amazon: Properties and risks to environment and human health

Improper disposal of copper mining wastes can threaten the ecosystem and human health due to the high levels of potentially toxic elements released into the environment. The objective of this study was to determine the properties of Cu mining wastes generated in the eastern Amazon and their potential risks to environment and human health. Samples of forest soil and artisanal/industrial Cu mining wastes were collected and subjected to characterization of properties and pseudo-total concentrations of Al, As, Ba, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, and Zn, in addition to chemical fractionation of Cu. The pH ranged from near neutrality to alkaline. Pseudo-total concentrations of Cu were high in all wastes, mainly in the artisanal rock waste, with 19,034 mg kg−1, of which 61% is concentrated in the most reactive fractions. Pollution indices indicated that the wastes are highly contaminated by Cu and moderately contaminated by Cr and Ni. However, only the artisanal rock waste is associated with environmental risk. Non-carcinogenic and carcinogenic human health risks were detected, especially from exposure to Cr in the artisanal rock waste. Prevention actions and monitoring of the artisanal mining area are necessary to avoid impacts to the local population.

Phytoremediation Potential of Native Herbaceous Plant Species Growing on a Paradigmatic Brownfield Site

Phytomanagement techniques using native species allow the recovery of contaminated soils at low cost and circumvent the ecological risks associated with the use of non-native species. In this context, a paradigmatic brownfield megasite highly contaminated by As and Pb was sampled in order to analyze soil–plant interactions and identify plant species with phytoremediation potential. A survey was first carried out in a 20-ha area to obtain an inventory of species growing spontaneously throughout the site. We then performed another survey in the most polluted sub-area (1 ha) within the site. Pseudototal concentrations of contaminants in the soil, aerial parts of the plants, and roots were measured by ICP-MS. A detailed habitat classification was done, and a specific index of coverage was applied by means of a 1-year quadrat study in various sampling stations. Results converged in the selection of six herbaceous species (Dysphania botrys, Lotus corniculatus, Lotus hispidus, Plantago lanceolata, Trifolium repens, Medicago lupulina). All of these plants are fast-growing, thereby making them suitable for use in phytostabilization strategies. Furthermore, they are all easy to grow and propagate and are generally self-sustaining. All six plants showed accumulation factors below 1, thus revealing them as pseudomethallophytes and excluders. However, L. hispidus and M. lupulina showed translocation capacity and are considered worthy of further study.

Partitioning of heavy metals in different particle-size fractions of soils from former mining and smelting locations in Austria

Austrian soils from mainly historical mining and smelting sites were separated into four particle size fractions (coarse sand, fine sand, silt and clay) to distinguish the possible origins and pathways of heavy metals. Each fraction was extracted with aqua regia to determine the pseudo-total content and with CaCl2 to determine the available content of metals. The soil mineralogical composition of the < 2000 µm fraction was determined by X-ray diffraction (XRD). In general, the concentration of heavy metals and metalloids increased as soil particle size decreased. Based on the correlations of concentrations vs. the log of the mean particle size, obtained from each fraction the presence of unweathered allochthonous minerals were especially present in samples from locations at Rabenstein for most trace elements, at Arzwaldgraben for Cd, Co, Mn and Pb, at Johnsbach for Cd, Co, Mn, Pb and Zn and at Pilgersdorf for Cr. The opposite trend was found for the samples of the industrial area of Arnoldstein, Zeltweg and Hinterlobming suggesting that their metal load was derived from the discharge of effluents or from weathered phases.

New Topsoil Sampler for the Assessment and Monitoring of Forest Soil Contamination

The forest litter and underlying mineral topsoil are typically sampled and analyzed separately although they are in a dynamic balance, which ensures macro- and microelement cycling in the forest ecosystem, including the flux and accumulation of xenobiotics in the contaminated sites. Although the national legal regulations specify single limits of element concentration for the entire “topsoil” layer, irrespectively of the kind of materials resting at the earth surface down to the specified depth, the direct analysis of bicomponent forest topsoil (litter + mineral topsoil) was problematic because of the lack of a suitable sampler. The paper presents a comparative analysis of Cu, Pb, and Zn concentrations in the forest topsoil layers (0–25 cm), sampled using a new construction sampler invented for a joint collection of the litter layer and underlying mineral layer (to the specified depth). Litter samples (using a steel frame), mineral topsoil samples (0–25 cm, using gouge auger after litter removal), and mixed topsoil samples (0–25 cm, including litter) were collected in 16 replicates from four variably contaminated plots (copper mining and smelting area) afforested with poplar or pine. Pseudo-total concentration of Cu, Pb, and Zn was analyzed after sample digestion in aqua regia. The concentration of elements in the samples consisting of jointly collected litter and mineral layer was noticeably higher than in the samples consisting of the mineral topsoil only, which confirmed the effective inclusion of the litter. The concentrations of trace elements measured in the samples of jointly collected litter and mineral topsoil did not differ (NIR Fisher test at p &lt; 0.05) from the concentrations calculated using the data for litter and mineral soil separately collected and analyzed, which confirmed the usefulness of the new sampler for reliable collection of the forest topsoil samples without skipping any material which may influence the results of soil contamination assessment and risk assessment.

Sadržaj elemenata u tragu u urbanom zemljištu Šapca i procena ekološkog rizika

This study deals with the assessment of trace elements pollution of urban soil in Šabac. A total of 32 samples of the surface layer of soil (up to 10 cm deep) were collected from the locations of three city parks in the urban zone. Pseudototal concentrations of seven elements: copper (Cu), lead (Pb), cobalt (Co), nickel (Ni), manganese (Mn), cadmijum (Cd) and chrome (Cr) were determined in the samples after aqua regia digestion, using atomic absorption spectrophotometry. The abundance of elements in the analyzed soil samples was: Mn &gt;&gt; Pb&gt; Cr&gt; Ni&gt; Cu&gt; Co&gt; Cd. The conducted correlation analysis showed good correlation of the pairs of Cu - Pb, Cu - Cd and Pb - Cd elements, while the cluster analysis singled out two main groups of elements. The first group included Pb, Cd, and Cu, indicating that these elements originated from anthropogenic sources, while the remaining elements were probably of geogenic origin. Based on the obtained results, the assessment of the level of soil contamination with trace elements was performed, as well as the assessment of the ecological risk. Mean values of contamination factors indicate that the soil from all three examined sites is contaminated with Pb and Cd. The Cd has the higher individual potential ecological risk then the other elements.

Bioaccessibility of potentially toxic metals in soil, sediments and tailings from a north Africa phosphate-mining area: Insight into human health risk assessment

The risk assessment of phosphate mining/processing industrial activities on the environment and human health is crucial to properly manage and minimize the risks over time. In this work, we studied the inhalation and dermal bioaccessibility of potentially toxic metals (PTM) in different particle-size fractions of urban soil, sediments and tailings from Gafsa-Metlaoui phosphate mining area, to assess afterwards the non-carcinogenic (NCR) and carcinogenic (CR) risks for the health of local citizens and workers constantly exposed to airborne particulate matter (PM) originating from these sources of contamination. Samples were separated in particle-size fractions by centrifugation and consecutive cycles of sedimentation and decanting. The pseudo-total concentrations and bioaccessible fractions of PTM were extracted by aqua regia and in vitro bioaccessibility tests, respectively. Both sediments and tailings showed higher-than-background concentrations of PTM (mainly Cd, Zn and Cr), with a tendency to accumulate these metals in fine particles (<10 μm). In urban soil, only Cd was above the background concentration. The bioaccessibility of PTM via inhalation was significantly higher in artificial lysosomal fluid (ALF) than in simulated epithelial lung fluid (SELF): basically, Cd was the most bioaccessible metal (relative bioaccessibility up to 80%), followed by the medium-to-high bioaccessible Zn (47%), Pb (46%) and Cu (39%), and the least bioaccessible Cr (16%). In synthetic skin surface liquid (NIHS 96-10), only Cd was bioaccessible at worrying extent (20–44%). On the basis of US.EPA risk assessment, the exposure to PTM bioaccessible fractions or pseudo-total concentrations would not cause serious NCR and CR risks for human health. Significant health risks (Hazard Index >1 and CR > 10−4), especially for children, can occur if ingestion route is also considered. The findings underline the need for adequate protection of contaminated soil, sediments and mine tailings laying nearby urban agglomerates, to reduce the health risks for inhabitants and workers of Gafsa-Metlaoui mining area.

Geochemical fractions of trace metals in surface and core sections of aggregates in agricultural soils

Agrochemicals containing trace metals such as pesticides and fertilizer are intensively used in apple production systems in many countries. There is a risk of accumulation of trace metals, particularly in the sensitive root rhizosphere area. In this study, the trace metal concentrations of soils were determined in macroaggregates at the “mm scale” sampled from apple orchards. Soil samples were taken from five different locations at 0–20 cm soil depths in an apple orchard. Pseudo-total trace metal (Cd, Cr, Cu, Ni, Pb, and Zn) concentrations of soil samples separated from the surface and core sections of the soil aggregate were determined by digestion with Aqua regia. The modified BCR sequential extraction method was used to determine four operationally defined geochemical trace metal fractions in soil samples. The pseudo-total concentrations of Cd and Cu were significantly higher, and Zn was lower at the surface than in the core sections (paired-t test, p < 0.05) of soil aggregates. The concentrations of all trace metals in the acid-soluble fraction and reducible fractions were significantly higher at the surface of soil aggregates than those in the core section. The same was true for the sum of trace metal concentrations in the extracts of the three fractions considered potentially mobilizable, except for Cr. Our results demonstrated that Cd and Cu originated probably from agrochemicals accumulating significantly on aggregate surfaces, where they were in close contact with plant roots. The generally higher extractability of all trace metals on the surface of aggregates can be attributed to the preferential accumulation of newly-added trace metals in comparatively weakly bound chemical forms.

Influence of roadways on heavy metal content in soils and yerba mate tissue in southern Brazil

PurposeVehicular road traffic may represent an important soil and plant contamination source. In this context, the concentration of heavy metals (Cd, Pb, As, Sb, Ni, Cu, Fe, Al, Mn and Zn) and macronutrients (Ca, Mg, K and P) was evaluated in yerba mate (Ilex paraguariensis St. Hil.) cultivations and in soils adjacent to highways.Design/methodology/approachThe investigated yerba mate cultivations were located in southern Brazil. Plant tissue (young and old leaves and branches) and soil (0–10 cm) samples were collected at five distances from the highway (0–10, 10–20, 20–30, 30–40 and 40–50 m). Plant tissue was analyzed with and without washing to evaluate contributions from particulate deposition.FindingsAlthough increases in soil pseudo-total concentrations of Cd, Cu, Ni, Zn, Fe, Mn, Ca and Mg were observed only at the Erechim site, geoaccumulation indices and enrichment factors (EFs) did not indicate any heavy metal pollution. These results indicate the existence of natural variation in soil. Cadmium was more concentrated in branches than in leaves, while the opposite was observed for Pb. High levels of Mn and Al were found in foliar tissue. In summary, highway proximity did not lead to heavy metal contamination of yerba mate under the evaluated conditions.Originality/valueThis research explores the possibility of heavy metal pollution in plantations of yerba mate adjacent to highways and indicates natural concentrations of toxic elements that exceed current legislation, which was an important discovery regarding the yerba mate production chain.