Applied Geochemistry (v.44, #C)

Preface by Eduardo Ferreira da Silva; Amélia Paula Reis; Carla Patinha (1-2).

Heavy metal distribution in mine-soils and plants growing in a Pb/Zn-mining area in NW Spain by C. Monterroso; F. Rodríguez; R. Chaves; J. Diez; C. Becerra-Castro; P.S. Kidd; F. Macías (3-11).
The aim of this study was to identify metal-tolerant plants with potential application in phytoremediation strategies. For this we evaluated the distribution and chemical fractionation of heavy metals in soils and their accumulation or exclusion by native plant species growing in an abandoned Pb/Zn mine in NW Spain. Mine-soils (I = 0–20 cm, II = 20–40 cm) and shoots of the dominant plants were sampled at 39 sampling points in a (100 m × 100 m) regular grid at two sites (mine zone (MZ) and tailing ponds (TP)).Total metal contents in mine-soils presented a high heterogeneity and the principal contaminants were Cd, Hg, Pb and Zn (in agreement with the mineralogy of the site). Total concentrations varied from 2 to 95 mg Cd kg−1, 0.2 to 24.8 mg Hg kg−1, 46 to 6100 mg Pb kg−1, and 340 to 52,000 mg Zn kg−1. Soil metal distribution did not vary significantly with depth, but total and EDTA-extractable metal concentrations were higher in MZ than TP. On the other hand, the relative extractability of soil metals (EDTA-extractable concentration expressed as a % of total concentration) was higher in TP. The residual fraction was dominant for Co, Cr, Cu, and Ni, representing generally more than 50% of total concentration. Pb was preferentially associated with the oxidisable fraction, followed by the acid-extractable fraction. Both Cd and Zn were amply represented by the oxidisable, reducible and acid-extractable fractions. All the studied plant species were metal-tolerant (pseudometallophytes), although differences were found between species. Significant differences were found in plant accumulation of Cd and primarily, Zn. Cytisus scoparius and C. multiflorus were efficient metal-excluding species, and could be interesting candidates for phytostabilisation techniques and/or revegetation of heavily contaminated soils. Salix atrocinerea, presented significantly higher concentrations of Zn in its aerial biomass (543 ± 108 mg Zn kg−1) than the remaining species and bioconcentration factors (BCF) of up to 2.35 for Zn and 4.17 for Cd, respectively. This population could be interesting in the phytoextraction of low to moderately-contaminated soils.

Heavy metal pollution in mine–soil–plant system in S. Francisco de Assis – Panasqueira mine (Portugal) by Carla Candeias; Rita Melo; Paula Freire Ávila; Eduardo Ferreira da Silva; Ana Rita Salgueiro; João Paulo Teixeira (12-26).
The active Panasqueira mine is a tin–tungsten (Sn–W) mineralization hosted by metasediments with quartz veins rich in ferberite. The economic exploitation has been focused on wolframite, cassiterite and chalcopyrite. The mineralization also comprises several sulphides, carbonates and silver sulphosalts. The mining and beneficiation processes produces arsenic-rich mine wastes laid up in huge tailings and open air impoundments that are the main source of pollution in the surrounding area, once the oxidation of sulphides can result in the mobilization and migration of trace metals/metalloids from the mining wastes into the environment, releasing contaminants into the ecosystem.A geochemical survey was undertaken, in order to investigate the environmental contamination impact on agricultural and residential soils in S. Francisco de Assis village due to the mining activities. Rhizosphere samples, vegetables (Solanum tubersum sava and Brassica olerácea L.) which constitute an important part of the local human diet), irrigation waters and road dusts were collected in private residences in S. Francisco de Assis village. According to the Ontario guidelines (Ministry of Environment, 2011), the Arsenic contents in the rhizosphere soils exceed 20 times the reference value for agricultural soils (11 mg kg−1). The result obtained showed that some edible plants frequently used in the region could be enriched in these metals/metalloids and may represent a serious hazard if consumed. The potatoes tend to have a preferential accumulation in the leaves and roots while in cabbages most elements have a preferential accumulation in the roots. An index of the risk for residents, due to ingesting of these metals/metalloids, by consuming vegetables grown around the sampling area, was calculated and the result indicates that the inhabitants of S. Francisco de Assis village are probably exposed to some potential health risks through the intake of arsenic, cadmium and also lead via consuming their vegetables.

Urban agriculture in Portugal: Availability of potentially toxic elements for plant uptake by N. Cruz; S.M. Rodrigues; C. Coelho; L. Carvalho; A.C. Duarte; E. Pereira; P.F.A.M. Römkens (27-37).
Soils from urban areas often contain enhanced pseudo-total levels of potentially toxic elements (PTEs). Considering the expanding tendency of urban agricultural practices it is necessary to understand if these contaminants are available for plant uptake and if they pose risks to animal and human health.This study showed that estimates of Daily Intakes (DIs) of Cu, Pb and Zn for grazing animals were above animal Acceptable Daily Intakes (ADIs) at specific sites under the influence of an airport, an oil refinery and near highways with high traffic rates in the “Grande Porto” urban area (Portugal). These results suggest that there is a potential for dietary transfer of contaminants associated with the ingestion of both contaminated soil and feed by cows and sheep at unacceptably high concentrations.Furthermore, results showed that 40% of variability of ryegrass shoot contents of Cu, Pb and Ni; 60% for Ba; 70% for Zn; and 80% for Cd can be significantly (p  < 0.01) explained by the variability of the corresponding chemical available pools in soils. Since the chemical available pools of PTEs in urban soils were rather low when compared with the corresponding pseudo-total pools (median 0.1–5%) and even when compared with the corresponding reactive pools it is advised to perform further research on the conditions and time span for the limited availability of PTEs in urban soils, and to determine under which conditions PTEs on reactive forms may become available.

This study was carried out to analyze the distribution and soil–plant transfer of selected potential harmful elements (PHEs: As, Hg and Zn) in soils and in two edible horticultural crops (cabbage, Brassica oleracea L., and tomato, Lycopersicon esculentum Mill). randomly sampled in kitchen gardens/small farms around one of the most important and old Portuguese industrial areas (Estarreja Chemical Complex-ECC). The results show that 46% and 11.5% of the soils present high total As (12–532 mg/kg) and Hg (6.6–13.65 mg/kg) concentrations that exceed protective health Canadian soil quality guidelines. Soil As and Zn available fractions are also of concern for groundwater and crops contamination as more than 84% of the samples were above the trigger value proposed by the German legislation for both elements (0.4 and 2 mg/kg, respectively). In the horticultural crops the cabbage leaves concentrate more the PHEs (max.: 3.5, 0.08 and 746 mg/kg dw for As, Hg and Zn, respectively) than the tomato fruit (max.: 0.4, 0.02 and 82 mg/kg dw, respectively). The highest concentration of the study PHEs in soils and horticultural crops were found near sewage outlets that are chiefly related to historical industrial activities mostly from arsenopyrite roasting and a chloralkali plant. The values of estimated bioaccumulation and bioconcentration coefficients suggested exclusion mechanisms for transfer of As to edible cabbage and tomato tissues and cabbage Zn tolerance capacity. The concentration of the PHEs in the edible horticultural crops tissues were not directly related with respective soil total concentration or available fractions, specially for As and Hg. Sampling locations with the highest concentrations of As, Hg, Zn in soil and vegetable foodstuffs should be sites to foregoing research and human daily intakes should be investigated in order to evaluate potential health risks.

Urban geochemistry of lead in gardens, playgrounds and schoolyards of Lisbon, Portugal: Assessing exposure and risk to human health by A.P. Reis; C. Patinha; J. Wragg; A.C. Dias; M. Cave; A.J. Sousa; M.J. Batista; C. Prazeres; C. Costa; E. Ferreira da Silva; F. Rocha (45-53).
To assess the impact of potentially harmful elements in soil/dust on the health of children that use urban recreational areas to play outdoors, an urban survey of Lisbon, the largest city in Portugal was carried out, collecting soils and dusts from public gardens, parks, playgrounds and schoolyards. An exposure and risk assessment study for the incidental soil/dust ingestion of lead was carried out based on US EPA guidelines using a sub-set of 19 topsoil and 8 outdoor dusts, out of a total of 51 samples, incorporating oral bioaccessibility measurements using the Unified BARGE Method developed by the Bioaccessibility Research Group of Europe. The objectives are: (i) interpretation of soil and dust oral bioaccessibility measurements; (ii) assessment of site-specific exposure and non-carcinogenic risk posed by lead; (iii) hazard assessment for urban soil and dust with respect to children playing in outdoor recreational areas. The results show that significant fractions of Pb occur in bioaccessible forms, 24–100% in soils and 35–100% in dusts and the associated risk is greater for dust ingestion than for soil ingestion in Lisbon city recreational areas.

Spatial distributions and sources of heavy metals in sediment from public park in Shanghai, the Yangtze River Delta by Jing Yang; Xiang-Zhou Meng; Yan-Ping Duan; Li-Zao Liu; Ling Chen; Hefa Cheng (54-60).
Display OmittedAs one of the largest and most modern cities in China, Shanghai has experienced rapid urban expansion over the last three decades, which may cause environmental pollution. This study collected the surface sediments from 35 lakes in public parks in different areas of Shanghai and explored the relationship between heavy metals (HM; Co, Cr, Ni, Cd, Cu, Pb, and Zn) distribution and city urbanization factors. The concentrations of Co, Cr, and Ni in sediment were similar to those in background soil of shanghai, whereas the levels of Cd, Cu, Pb, and Zn were elevated. Overall, sediments from the central urban core area (CUC; inside the inner-ring highway) contained significantly higher levels of Cd, Cu, Pb, and Zn than those from the developed urban area (DDU; between the inner- and middle-ring highway), the developing urban area (DIU; between the middle- and outer-ring highway), and the suburban area (SU; outside the outer-ring highway), suggesting potentially large contributions from point sources related to human activities in the highly urbanized regions. For Co, Cr, and Ni, no significant differences of concentration and enrichment were found among different areas. The levels of Cd, Cu, Pb, and Zn showed strong associations with density of road network (R 2  > 0.84) in six urban administration districts of Shanghai, quantitatively confirming that these four metals mainly originated from traffic emission. However, the percent of residential and industrial lands had no correlation with HM (Cd, Cu, Pb, and Zn) concentrations in sediment from Shanghai.

Identifying environmental and geochemical variables governing metal concentrations in a stream draining headwaters in NW Spain by F. Soto-Varela; M.L. Rodríguez-Blanco; M.M. Taboada-Castro; M.T. Taboada-Castro (61-68).
Headwater stream, draining from a rural catchment in NW Spain, was sampled during baseflow and storm-event conditions to investigate the temporal variability in dissolved and particulate Al, Fe, Mn, Cu and Zn concentrations and the role of discharge (Q), pH, dissolved organic carbon (DOC) and suspended sediment (SS) in the transport of dissolved and particulate metals. Under baseflow and storm-event conditions, concentrations of the five metals were highly variable. The results of this study reveal that all metal concentrations are correlated with SS. DOC and SS appeared to influence both the metal concentrations and the partitioning of metals between dissolved and particulate. The SS was a good predictor of particulate metal levels. Distribution coefficients (KD ) were similar between metals (4.72–6.55) and did not change significantly as a function of discharge regime. Stepwise multiple linear regression analysis reveals that the most important variable to explain storm-event KD for Al and Fe is DOC. The positive relationships found between metals, in each fraction, indicate that these elements mainly come from the same source. Metal concentrations in the stream were relatively low.

The study area is located in the transboundary River Douro basin (northern Portugal); it comprises the River Corgo fluvial network, which drains a meso-scale rural catchment with an area of 295 km2, underlain by crystalline rocks, in a temperate climate. The results reported in this study derive from a geochemical survey of active fluvial sediments, with the aim of characterising the spatial and temporal distribution of the contents of As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn in a basin with mountainous features. To assess total contents of metals and their potential availability, as well as possible different origins of metals (natural vs. anthropogenic), a sequential chemical approach was used (modified BCR procedure). Multivariate data analysis (PCA) was used to assist the interpretation of datasets.The results show that, on the one hand, the metal contents distribute among all the geochemical phases studied. For the most relative labile fractions the reducible fraction is the most significant. The element-partitioning among geochemical phases indicates: (a) Co and Mn are transported in greater proportions in the most labile fraction, as exchangeable ions, as well as important proportions of Ni, Zn and Cu; (b) Cd and Pb associate preferentially with the hydroxides of Fe and Mn; (c) Cr and Cu are also transported by the organic phase; (d) the residual phase transport important proportions of Cr, Ni, Zn, Cu, Fe and Pb. The higher concentrations of Cu, Zn and, in particular, Pb, in the most labile fractions, which are higher where the total contents are also higher (and not concomitant with a correspondent increase in the residual fraction), suggest an important contribution of anthropogenic activities to the total contents of these elements in the sediments. Chromium and Ni are the main metals from a lithological source, with relatively higher contents in the residual fraction, and the lowest in the most mobile fractions. On the other hand, the spatial distribution pattern of metal contents in the mobile and semi-mobile fractions (available + reducible + oxidisable), shows that, in general, higher contents of metals in the most mobile fractions occur along the main courses of the major tributaries, in particular in the flatter reaches. The patterns of seasonal occurrence and distribution of metals show, in general, that the relative contents associated with the potentially available fraction increase during the period of low flow, which extends from April to September.

In recent years, shipping activities developed in Ninh Hoa district (south-central Vietnam), have raised an urgent environmental concern related to the use of copper slag as abrasive material for removing rust from the surface of the ships. This study was conducted to investigate the characteristics of the blasted copper slag (BCS). Enrichment Factors (EF) were used to assess the contamination status of sediments and soils in the surroundings of the BCS dump site. The potential release of As and heavy metals (HMs) from BCS was examined through pHstat and cascade leaching tests in combination with XRD analysis. From the results, As, Cr, Ni, Pb and Zn were characterized as moderate severely enriched to severely enriched while Cu showed extremely severe enrichment in the sediments. Regarding the soil collected at the dump site, it was strongly contaminated with As, Cu and Zn (extremely severe enrichment) whereas Cr, Ni and Pb were ranked as severely enriched. This study also demonstrates that it is important to use local background values of As and HMs in soils and sediments for a correct estimation of the degree of As or HM contamination. The cascade leaching test results from the BCS showed that the concentrations of the regulated HMs leached were lower than the EU limit for non-hazardous waste; except for Cu. Results from pHstat leaching tests at pH 4 with BCS indicated that upon acidification, HM release from the <1 mm fraction is higher compared to the bulk sample. A significant release of Cu from BCS was also observed for both fractions (<1 mm fraction and bulk sample) in pHstat leaching tests. In view of the elevated Cu concentrations found in the slag, the potential recovery of Cu from BCS should be investigated.

Wildfires transform the landscape, leading to changes in surface cover and, potentially, in water quality. The purpose of this study was to assess changes in the chemical composition of soils and surface water as a result of a wildfire that burned in 2006 in the Marão Mountains, NE Portugal, by comparing pre- and post-fire hydrochemical data and burned/unburned soil data, and to examine the recovery of vegetation over time using Landsat TM imagery. Studies that have access to pre-fire data are rare and even fewer studies document changes in biomass as a result of fire and during the postfire recovery period. Samples of ash, soil and water, from within and outside the burned area, were collected 5 months, and one year after the fire, for chemical analyses. Landsat TM Images were downloaded and transformed into a vegetation index, in order to analyze landcover dynamics and to calculate biomass. The wildfire effects on the Marão River water quality, resulted in an increase in the total mineralization of water. Five months after the wildfire the electrical conductivity (E.C.) at the mainstem was about 56% higher than pre-fire values (E.C. increased from 25 to 39 μS/cm) and still higher one year after (36 μS/cm). Cations of Ca, Na, Mg and Mn showed the greatest increase. This increase was probably triggered by the movement of ash to the watercourses. This disturbance had already attenuated one year after wildfire to values closer to pre-fire data except for manganese. Manganese had anomalous concentrations in the water within the burned area. The concentration of Mn in ash samples reached values up to 5 times more than values found in underlying soils. One year after the wildfire, almost all the burned area had recovered with herbaceous vegetation and patches of shrub vegetation. The wildfire burned 1194.7 dry tons of biomass which means, on average, 4.9 dry ton/ha. Based on the mass of burned biomass, we calculated approximately 350 g/ha of Mn were released as a result of the fire. We suggest that this type of calculation can be conducted before a fire to help resource managers understand worst-case scenarios for changes in water quality that have the potential to affect aquatic biotic and the suitability of water for drinking water purposes and agriculture.

Fly ash from coal combustion – An environmental source of organic compounds by J. Ribeiro; T.F. Silva; J.G. Mendonça Filho; D. Flores (103-110).
The fly ash resulting from coal combustion (anthracite A coal type) for power generation was investigated. The fly ash produced during the coal combustion was emplaced in surface landfills near the thermal power plant facilities. A total of six samples were collected in the fly ash landfills which were therefore analyzed for their geochemical characterization. The analysis comprised the determination of total organic carbon and total sulfur, the identification of aliphatic hydrocarbons, and the identification and quantification of the sixteen priority polycyclic aromatic hydrocarbons (PAHs). This study provides information about the potential environmental impacts associated with the disposal of fly ash and, in addition, it also provides scientific knowledge about the effects of combustion process in the soluble fraction of coal organic matter and about the behavior of these compounds during combustion. The results about the aliphatic compounds demonstrated that the long-chain n-alkanes, the pentacyclic terpanes, and the regular steranes (C-27, C-28, C-29) increase in fly ash samples comparatively to coal. The PAHs with two and three aromatic rings (low molecular weight PAHs – LMW PAHs) were not detected in fly ash while fluoranthene (four rings) was detected in all samples, and benzo[a]anthracene (four rings), benzo[b]fluoranthene (four rings), indeno[123-cd]pyrene (five rings), benzo[ghi]perylene (five rings), and dibenzo[ah]anthracene (six rings) were detected in some of the samples. The absence of LMW PAHs and the presence of some high molecular weight (HMW) PAHs, with four to six rings, are attributed to the combustion process. The low sum of the priority PAHs in fly ash samples can be related with both, the high rank of the coal burned in the thermal power plant (anthracite A), with the technical combustion conditions and/or leaching process in the fly ash landfills. The organic compounds adsorbed in fly ash particles may be released into the environment and therefore can represent a potential source of contamination of soils and waters and human health problems.

Study of an aplite dyke from the Beira uraniferous province in Fornos de Algodres area (Central Portugal): Trace elements distribution and evaluation of natural radionuclides by Maria José Trindade; Maria Isabel Prudêncio; Christopher Ian Burbidge; Maria Isabel Dias; Guilherme Cardoso; Rosa Marques; Fernando Rocha (111-120).
A uranium-rich aplite dyke with spheroidal alteration sited in the Beira uraniferous province, in Fornos de Algodres area (Northern Central Portugal) was studied, focusing on trace element distributions, especially U, in the aplite. A vertical profile, different size fractions, and various concentrically weathered layers of rock, were examined. The main goal of the work is to better understand the geochemical behavior and distribution of natural radionuclides in fine-grained granitic rocks, and changes that occur during weathering. The rock samples obtained from this site were examined using chemical and mineralogical methods: instrumental neutron activation analysis (INAA) and the X-ray diffraction (XRD). Field gamma spectrometry (FGS) and high resolution gamma spectrometry (HRGS) in the laboratory were also performed in order to determine concentrations of the natural radionuclides (K, Th and U) responsible for terrestrial gamma radiation, and for comparison of results with INAA measurements, enabling some information concerning radon losses.The U concentration in the studied samples vary between 4.5 and 83 ppm (always higher than upper continental crust value), with the higher values detected in the clay and sand fractions of weathered aplite (residual clay) and in the rounded boulders of aplite with spheroidal weathering, especially in the core. Strong variations in natural radionuclide contents, especially observed between residual clay and soil, relate to differences in source material. The large difference between pre-Rn and post-Rn values obtained by HRGS suggests high loss of radon (40% minimum), which is in accordance with field measurements. Due to generally high concentration of U, the aplite is a potentially strong source of emission of radon to the atmosphere with consequent radiological hazards.