Eco-restoration of a mine technosol according to biochar particle size and dose application: study of soil physico-chemical properties and phytostabilization capacities of <Emphasis Type="Italic">Salix viminalis</Emphasis>

Purpose

Anthropic activities induce severe metal(loid)s contamination of many sites, which is a threat to the environment and to public health. Indeed metal(loid)s cannot be degraded, and thus accumulate in soils. Furthermore, they can contaminate surrounding ecosystems through run-off or wind erosion. This study aims to evaluate the phytostabilization capacity of Salix viminalis to remediate As and Pb highly contaminated mine site, in a biochar-assisted phytoremediation context and to assess biochar particle size and dose application effects.

Materials and methods

To achieve this, mesocosm experiments were conducted using the contaminated technosol and four different size fraction of one biochar as amendment, at two application rates (2 and 5%). Non-rooted cuttings of Salix viminalis were planted in the different mixtures. In order to characterize the mixtures, soil pore waters were sampled at the beginning and at the end of the experiment and analyzed for pH, electrical conductivity, and metal(loid) concentrations. After 46 days of Salix growth, roots, stems, and leaves were harvested and weighed, and As and Pb concentrations and distributions were measured.

Results and discussion

Soil fertility improved (acidity decrease, electrical conductivity increase) following biochar addition, whatever the particle size, and the Pb concentration in soil pore water decreased. Salix viminalis did not grow on the non-amended contaminated soil while the biochar amendment permitted its growth, with a better growth with the finest biochars. The metal(loid)s accumulated preferentially in roots.

Conclusions

Fine biochar particles allowed S. viminalis growth on the contaminated soil, allowing this species to be used for technosol phytostabilization.

     

Accumulation and phytoremediation of Pb,Zn, and Ag by plants growing on Koshk lead–zinc mining area,Iran

Purpose

This study investigated the extent of metal accumulation by plants colonizing a mining area in Yazd Province in Central Iran. It also investigated the suitability of these plants for phytoextraction and phytostabilization as two potential phytoremediation strategies.

Materials and methods

Plants with a high bioconcentration factor (BCF) and low translocation factor (TF) have the potential for phytostabilization, whereas plants with both BCFs and TFs >1 may be appropriate for phytoextraction. In this study, both shoots and roots of 40 plant species and associated soil samples were collected and analyzed for total concentrations of trace elements (Pb, Zn, and Ag). BCFs and TFs were calculated for each element.

Results and discussion

Nonnea persica, Achillea wilhelmsii, Erodium cicutarium, and Mentha longifolia were found to be the most suitable species for phytostabilization of Pb and Zn. Colchicum schimperi, Londesia eriantha, Lallemantia royleana, Bromus tectorum, Hordeum glaucum, and Thuspeinantha persica are the most promising species for element phytoextraction in sites slightly enriched by Ag. Ferula assa-foetida is the most suitable species for phytostabilization of the three studied metals. C. schimperi, L. eriantha, L. royleana, B. tectorum, M. longifolia, and T. persica accumulated Ag, albeit at low level.

Conclusions

Our preliminary study shows that some native plant species growing on this contaminated site may have potential for phytoremediation.

     

Assessment of the adaptive capacity of plant species in copper mine tailings in arid and semiarid environments

Purpose

The objective of this work was to identify hyperaccumulator plants and evaluate their capacity on copper mine tailings in the Antofagasta Region (Chile), considered one of the most arid in the world.

Materials and methods

Two native plant species, Gazania rigens and Pelargonium hortorum, were grown during 11 weeks on mine tailings. The physico-chemical characterization of the mine tailings under study indicated that the substrate required conditioning to support a phytoremediation system. In this respect, organic and inorganic amendments and mycorrizhal fungi were added to the substrate. Three treatments were designed to assess the effects of the amendments through an analysis of variance.

Results and discussion

Indicators of plant growth and development were measured weekly, and concentrations of Cd, Cu, Fe, Mn, Pb, Al, and Zn in roots of tailing-grown plants and substrate were measured at the end of the experiment.

Conclusions

The results were used to determine the bioconcentration factor (BCF), which demonstrated that both species act as excluders of Fe, Mn, Pb, Al, and Zn. In addition, it was found that both species present characteristics of potential accumulators of Cu.

     

Effects of phosphate on trace element accumulation in rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.): a 5-year phosphate application study

Purpose

Phosphate (P) fertilizers are being widely used to increase crop yield, especially in P-deficient soils. However, repeated applications of P could influence trace element bioaccumulation in crops. The effects of 5-year P enrichment on trace element (Cu, Zn, Cd, Pb, As, and Hg) accumulation in Oryza sativa L. were thus examined.

Materials and methods

Two paddy soils with different initial P availabilities were amended with and without P fertilizer from 2009 to 2013. Trace elements and P levels in rice and soils were analyzed.

Results and discussion

In soil initially with limited P, P amendment enhanced grain Pb, As, and Hg concentrations by 1.8, 1.5, and 1.4-fold, respectively, but tended to decrease the grain Cd level by 0.73-fold, as compared to the control. However, in soil initially with sufficient P, P amendment tended to reduce accumulation of all examined elements in rice grain.

Conclusions

Phosphate amendment in initially P-limited and P-sufficient soils had different effects on trace element availability in soil (as reflected by extractable element) and plant physiology (growth and metal translocation), resulting in contrasting patterns of trace element accumulation in rice between the two types of soils. Our study emphasized the necessity to consider the promoting effects of P on Pb, As, and Hg accumulation in grain in initial P-deprived soil.

     

Factors influencing the organic carbon pools in tidal marsh soils of the Elbe estuary (Germany)

Purpose

Soils of tidal marshes play an important role in regional carbon (C) cycles as they are able to store considerable amounts of organic carbon (OC). However, the C dynamics of marsh soils of the Elbe estuary have not been investigated so far. Therefore, the aim of this study was to identify the sources and distribution of soil organic carbon (SOC) and the factors influencing the SOC pools of tidal marshes of the study region.

Materials and methods

In this study, SOC pools were determined in different salinity zones and elevation classes of the estuarine marshes. The amount of initial allochthonous OC was derived from the OC content in fresh sediments. The difference to the recent OC content in the soils was interpreted as autochthonous accumulation or mineralization by microorganisms.

Results and discussion

Young, low marshes of the study sites seem to be predominantly influenced by allochthonous OC deposition whereas the older, high marshes show autochthonous OC accumulation in the topsoils (0–30 cm) and mineralization in the subsoils (30–70 cm). SOC pools of the whole profile depth (0–100 cm) did not significantly differ between elevation classes, but decreased significantly with increasing salinity from 28.3 kg m^?2 in the most upstream site of the oligohaline zone to 9.7 kg m^?2 in the most downstream site of the polyhaline zone. Even though the areal extent of the investigated salinity zones was similar, the SOC mass within 100 cm soil depth decreased from 0.62 Tg (1 Tg = 10¹² g) in the oligohaline zone to 0.18 Tg in the polyhaline zone.

Conclusions

Elevation was found to be one factor influencing the SOC pools of tidal marshes. However, salinity seems to be an even stronger influencing factor reducing the above-ground biomass and, accordingly, the autochthonous OC input as well as the allochthonous input by enhanced mineralization of OC along the course of the estuary. An upstream shift of the salinity zones by sea level rise could, therefore, lead to a reduction of the SOC storage of the estuarine marshes.

     

Suitability of a municipal solid waste as organic amendment for agricultural and metal(loid)-contaminated soils: effects on soil properties,plant growth and metal(loid) allocation in <Emphasis Type="Italic">Zea mays</Emphasis> L.

Purpose

The use of municipal solid wastes (MSWs) as a low-cost source of organic matter for soils should be considered after discarding the environmental risks related to their metal(loid) load. The goal of this work was to assess the employment of a MSW as an organic amendment in two types of soil (an agricultural soil, A, and a metal(loid)-enriched mine tailings soil, T) attending to changes in soil properties and in plant growth, nutrition and metal(loid) translocation from roots to aerial parts of Zea mays L. (stalk, leaves, tassel, husk, cob and kernel).

Materials and methods

After a comprehensive characterisation of each soil treatment (A, A + MSW, T, T + MSW), a pot-designed experiment was carried out. Soil solution was monthly monitored throughout the experiment, and metal(loid) concentrations were measured.

Results and discussion

The MSW improved some fertility-related parameters in both soils, A and T: increased total and dissolved organic carbon, total nitrogen and soil microbiology. However, an increase in 0.01 M CaCl₂-extractable metal(loid) concentration was also observed. No differences in dry biomass were found between amended and not amended treatments. A fractionation of metal(loid) concentrations among plant organs occurred. For instance, the highest Cu and Pb concentrations were found in roots, while for Zn occurred in the stalk and the cob. The amended treatments favoured the accumulation of Mn in all plant organs. Kernels showed in general the lowest metal(loid) concentrations.

Conclusions

The addition of municipal solid wastes as organic amendment could be a suitable tool to increase soil fertility. However, due to the high metal(loid) content of this particular MSW, its use on agricultural soils would not be appropriate. By other hand, along with the improvement of soil fertility, the MSW was useful to promote plant development in the mine tailings soil which should be then considered as a potential tool to promote plant establishment in those metal(loid)-impacted soils.

     

Rhizosphere effects of <Emphasis Type="Italic">Populus euramericana</Emphasis> Dorskamp on the mobility of Zn,Pb and Cd in contaminated technosols

Purpose

This study aimed at investigating the rhizosphere effects of Populus euramericana Dorskamp on the mobility of Zn, Pb and Cd in contaminated technosols from a former smelting site.

Materials and methods

A rhizobox experiment was conducted with poplars, where the plant stem cuttings were grown in contaminated technosols for 2 months under glasshouse conditions. After plant growth, rhizosphere and bulk soil pore water (SPW) were sampled together. SPW properties such as pH, dissolved organic carbon (DOC) and total dissolved concentrations of Zn, Pb and Cd were determined. The concentrations of Zn, Pb and Cd in plant organs were also determined.

Results and discussion

Rhizosphere SPW pH increased for all studied soils by 0.3 to 0.6 units compared to bulk soils. A significant increase was also observed for DOC concentrations regardless of the soil type or total metal concentrations, which might be attributed to the plant root activity. For all studied soils, the rhizosphere SPW metal concentrations decreased significantly after plant growth compared to bulk soils which might be attributed to the increase in pH and effects of root exudates. Zn, Pb and Cd accumulated in plant organs and the higher metal concentrations were found in plant roots compared to plant shoots.

Conclusions

The restricted transfer of the studied metals to the plant shoots confirms the potential role of this species in the immobilization of these metals. Thus, P. euramericana Dorskamp can be used for phytostabilization of technosols.

     

Metal uptake by wetland plants: implications for phytoremediation and restoration

Purpose

This study was undertaken to determine the feasibility of using three aquatic macrophytes, Phragmites australis, Juncus effusus and Iris pseudacorus, to phytoextract potentially toxic elements (PTEs) from a contaminated area by mining activities.

Materials and methods

An artificial pond was constructed with two topsoils (yellow and black samples) collected from Portman Bay. In order to simulate the mixing with carbonate materials, which naturally occurs in this area, a stabilisation approach was applied by mixing with 30 % of limestone filler. Three replicates of each type of soil have been prepared in pots for the selected species. The total PTEs content (arsenic, cadmium, copper, iron, lead and zinc) was determined and the bioconcentration factor (BCF) and transfer factor (TF) calculated.

Results and discussion

Soil samples showed high PTEs content as a result of mining activities. As regards the root contents, the PTEs is higher in yellow samples (YS) than in black ones, because in these samples the PTEs content that could be mobilised is higher. The BCF results were higher than unity for arsenic, copper, lead and cadmium for I. pseudacorus and P. australis growing on YS soil. Overall, copper and manganese showed a larger number of plants with BCF higher than unity. The PTEs content in leaves is low, and the TF results are lower than unity in almost all samples.

Conclusions

The results indicate that it is possible to use the selected species for phytostabilisation of soils contaminated with PTEs. J. effusus, P. australis and I. pseudacorus could be considered as tolerant, and natural or artificial wetlands containing these species could be used for remediation purposes.

     

Urbanization effects on sediment and trace metals distribution in an urban winter pond (Netanya,Israel)

Purpose

This paper aims to elucidate urban development-induced processes affecting the sediment and the distribution of contaminating metals in a seasonal pond located in the highly populated Israeli Coastal Plain. The paper demonstrates how an integrated approach, including geochemical, sedimentological, geochronological, mathematical, historical, and geographical analyses, may decipher a complicated and dynamic metal pollution history in a sedimentary environment controlled by anthropogenic activity.

Materials and methods

Three short sediment cores were collected from the margins and center of a small urban pond (Dora, Netanya), located within the Israeli Coastal Plain. Profiles of grain size, organic matter (OM), trace metals (Pb, Zn, V, Ni, Cu, Cr and Co), Pb isotopic ratios, and ²¹⁰Pb activities (center and southern cores) were determined and a geochemical mixing model was employed (southern core). The watershed contour was calculated, and aerial photos and satellite images were examined.

Results and discussion

Construction activities in the watershed were chronologically associated with coarse sediment transport and deposition in the margins of the pond. The upper sandy layers were superimposed on layers rich in fine particles and OM, high concentrations of trace metals, and with Pb isotopic composition of more recent petrol. In the ²¹⁰Pb-dated southern core, deep metal-rich layers with petrol-related Pb isotopic ratios were inconsistent with metal emissions history. These findings point to mobility and migration of recent contamination metals through the coarse upper sediment layers and into deeper denser layers, confirmed also by a geochemical mixing model. Conversely, in the center of the pond, homogeneous fine particles were deposited with metal profiles consistent with regional emissions.

Conclusions

A small urban pond was found to provide an important case study for understanding heavy metal pollution records in highly populated regions. The margins of the pond depicted the surrounding urban development and the induced coarse sediment erosion, accompanied with post-depositional metal mobility. Due to the proximate developing residential areas, high metal concentrations accumulated in the margins, overshadowing regional atmospheric pollution levels recorded by sediment at the center of the pond.

     

Incorporation of trace elements on iron-rich concretions around plant roots of tagus estuary salt marsh (portugal)

Objective

The concentration gradients of solid Al, Fe, Mn, Zn, Cd, Pb, Cr and Ni in freshly formed concretions and in older concretions preserved in the sediment were evaluated in a millimetre resolution scale. These results provide a better understanding of the complex biogeochemical processes in the root-sediment system and elucidate the potentialities of marshes in the restoration of contaminated aquatic systems.

Methods

Tens (soll das vielleicht tonnes/tons heißen) of freshly formed concretions and preserved concretions were collected in the Rosário salt marsh. Each tubular structure and involving sediments were scraped in concentric layers of 2-mm thickness to form two sets of composite samples. The elemental composition of concretion and sediment samples were determined by atomic absorption spectrometry.

Results and Discussion

The sediment involving the concretions contained ～0.5 mmol g^-1 Fe, but concentrations increased towards the root up to 3.4 mmol g^-1 in 3-mm interval. Manganese, Zn, Cd and Pb exhibited similar radial distribution in both preserved and freshly formed concretions indicating that these metals remain in those structures with the age. Chromium and Ni showed a different pattern being lower in concretions with respect to involving sediments, and consequently, concretions do not act as a barrier for these elements. The estimated amount of Zn (59 tons), Pb (5 tons) and Cd (0.4 tons) retained in the concretions all over the Rosario salt marsh highlights the importance of these structures in sequestering metals.

Conclusions and Outlook

The sequestering may be particularly relevant in salt marshes located near urban and industrial zones, being areas working as a natural remediation system and contributing for the detoxification of aquatic environments and the well-being of coastal resources.

     

The forms and distribution of aluminum adsorbed onto maize and soybean roots

Purpose

The Al forms on maize and soybean roots were investigated to determine the main factors affecting the distribution of Al forms and its relationship with Al plant toxicity.

Materials and methods

Solution culture experiments were conducted to obtain the fresh roots of maize and soybean. KNO₃, citric acid, and HCl were used to extract the exchangeable, complexed, and precipitated forms of Al on the roots.

Results and discussion

The complexed Al was higher than the exchangeable and precipitated Al. Root CECs of soybean and maize were 77 and 55 cmol kg^?1, and functional groups on the soybean roots (262.4 cmol kg^?1) were greater than on maize roots (210.8 cmol kg^?1), which resulted in more exchangeable and complexed Al on soybean roots than on maize roots, and was one of the reasons for the increased Al toxicity to soybean. The total and exchangeable Al were the highest on the plant root tips and decreased gradually with increasing distance from the tips. Ca²⁺, Mg²⁺, and NH₄ ⁺ cations reduced the exchangeable Al on the roots. Oxalate and malate also reduced the adsorption and absorption of Al by roots, and the effect of oxalate was greater than malate.

Conclusions

Higher exchangeable and complexed Al on plant roots led to increased Al plant toxicity. Ca²⁺, Mg²⁺, and NH₄ ⁺ and oxalate and malate can effectively alleviate Al plant toxicity.

     

Remediation of heavy metal(loid)s contaminated sediments—in situ iron treatment and subsequent magnetic extraction

Purpose

Surface sediments contaminated with high levels of multiple heavy metal(loid) species are very common environmental problems. Especially, the labile and bioaccessible fractions of heavy metal(loid)s in the sediments are posing serious risks to the biota and the overlaying water quality. This study aimed at developing a potential method to manage the activity of the labile fractions of heavy metal(loid)s in surface sediments.

Materials and methods

This study assessed the feasibility of adding iron powder, a low-cost industrial by-product, to sediments containing high levels of Pb, As, and Cd to adsorb labile fractions of heavy metal(loid)s onto the sorbent surfaces and to retrieve the heavy metal(loid) laden powders by applying external magnetic field. In addition, the redistribution of Pb, Cd, and As in different sediment fractions, the dissolved fraction and the sorbent-adsorbed fraction, was also investigated and characterized.

Results and discussion

The results indicate that the bioactive labile fractions (exchangeable and carbonate-bound fractions) of heavy metal(loid)s are prone to concentrating onto iron powders and can be selectively removed from the sediments by magnetic retrieval. In addition, iron addition induces conversion of labile fractions of heavy metal(loid)s into more stabilized fractions.

Conclusions

Overall, the process can effectively minimize the activity of labile fractions of heavy metal(loid)s in surface sediments.

     

Impacts of sea-level rise on sediment microbial community structure and function in two New England salt marshes,USA

Purpose

There is growing evidence for a tight linkage between the structure and function of microbial communities and for the importance of this relationship in ecosystem responses to disturbances such as sea-level rise (SLR). While the role of plants in determining the capacity of salt marshes to keep pace with SLR through sediment accretion has received considerable attention, the role of microbes in offsetting these gains via decomposition is less understood.

Materials and methods

We conducted a controlled experiment to determine the structural and functional responses of microbes to SLR, using soil from the low intertidal zone of two New England salt marshes in Massachusetts and New Hampshire, USA. We used terminal restriction fragment length polymorphisms (t-RFLPs) generated from microbial 16S rDNA to evaluate community composition and diversity and focused on changes in respiration with SLR, measured as total respired carbon normalized by percent organic matter, as a surrogate for decomposition rate.

Results and discussion

We observed a 24% reduction in microbial respiration with a simulated rise in sea level of 40 cm. This functional change was accompanied by a structural shift in microbial community composition among samples from New Hampshire but not Massachusetts, assessed via principal coordinate analysis of t-RFLP data. We also found greater microbial diversity within our New Hampshire samples, suggesting that low diversity may constrain community compositional shifts.

Conclusions

Our results suggest that decreased microbial respiration could alleviate the negative effects of SLR on salt marsh surface elevation, at least in the short term, and that the diversity of the soil microbial community may positively influence functional responses such as respiration.

     

An efficient approach towards the bioremediation of copper,cobalt and nickel contaminated field samples

Purpose

The synthetic soil based bioremediation approach as reasonable and sustainable practice at the farming level where desired bioremediation could be established at lower cost.

Materials and methods

Metal-tolerant bacteria from different environmental field samples, (a) a municipal dump site, (b) an agricultural field and (c) sludge of electro-plating industries, were screened and characterized. Bioremediation of metal contaminants through isolated bacteria was compared under two different conditions, synthetic soil and basic minimal media containing copper, cobalt and nickel.

Results and discussion

The pollutants arising from industrial effluents are imparting a huge negative impact on agricultural land. Microbes are predominant in heavy metal-contaminated sites, which signifies as a potential opportunity for the researchers towards bioremediation. Three bacterial species showed high metal tolerance; 16S ribosomal DNA (rDNA) analysis revealed that the organisms were Proteus vulgaris strain, Stenotrophomonas sp. and Bacillus thuringiensis. Percentage removal of metals was also analysed under different concentrations and pH.

Conclusions

The current tested methods are helpful in streamlining the natural compliance of fragile elements and its uptake into the microbial system under in vitro and in situ conditions.

     

Soil pollution by mining activities in Andalusia (South Spain)—the role of Mineralogy and Geochemistry in three case studies

Purpose

Geochemical and mineralogical studies of soils potentially polluted by trace elements are basic to find the source of pollution, to understand the behavior of the contaminants in the environment, and to propose remediation and reclamation actions. This work reviews the role of the Mineralogy and Geochemistry to assess the hazard of soil contamination by trace elements in mining areas, focusing on three different case studies carried out in the Andalusian community (South Spain), with a Mediterranean temperate climate.

Materials and methods

Two significant mining districts were selected for this work: the Linares-La Carolina (Pb-Zn ores) and the Riotinto (Iberian Pyrite Belt, IPB) mining areas. Another case study was the Guadiamar basin, which soil was polluted by the spill produced in 1998 by the breakage of a mine tailing impoundment in Aznalcóllar mines (IPB). Soils, mine waste, and secondary precipitates were studied to approach the source of the pollution and the fate of the contaminants. Chemical composition (major and trace elements), soil parameters, and mineralogy of all materials selected were studied. In addition, the bioavailability of trace elements was determined by different methods.

Results and discussion

Pyrite and secondary phases are the main sources of pollution in the Riotinto area. Their stability is a key factor in the release of trace elements. The availability of trace elements in soils was lower in unpolluted leptosols than in contaminated orchards. In Linares-La Carolina, a severe pollution by Pb and a high availability (10–70% extracted with EDTA) were found. In Guadiamar basin, the residual pyrite sludge continues releasing trace elements to soil. Cd and Zn were mobile at pH <?6 and As at pH >?8, and Pb was quite immobile. Cd, Zn, and Pb can be coprecipitated by carbonates while As is mainly adsorbed by clays and iron oxyhydroxides.

Conclusions

The geochemical studies of soils polluted by mining activities allow to evaluate the availability of trace elements and their retention in soils. Therefore, geochemical and mineralogical studies are necessary for the assessment of soil pollution and remediation actions.

     

Effect of submerged macrophytes on metal and metalloid concentrations in sediments and water of the Yunnan Plateau lakes in China

Purpose

Submerged macrophytes have an ability to absorb metals and metalloids either from the sediments via the roots, from the water by the leaves, or from both sources. The objectives of this study were (1) to test the hypothesis that metal and metalloid concentrations in water and sediments from sampling sites with submerged macrophytes are significantly lower than those from sampling sites without submerged macrophytes, (2) to explore the accumulation potential for metals and metalloids of different submerged macrophyte species, and (3) to discuss the relationships among submerged macrophytes, water, and sediments in the Yunnan Plateau lakes.

Materials and methods

Twenty Yunnan Plateau lakes with different trophic levels were selected. Concentrations of 16 metals and metalloids (Al, As, Ba, Cd, Co, Cr, Cu, Fe, Li, Mn, Mo, Ni, Pb, Se, Sr, and Zn) in submerged macrophytes, water, and sediments were determined by using ICP-AES. Relationships among metal and metalloid concentrations in water, sediments, and submerged macrophytes were carried out by Pearson correlation analysis. The enrichment factor was calculated as the ratio between the concentration of metals and metalloids in a sediment sample and the soil background value.

Results and discussion

No significant differences were found in metal and metalloid concentrations in water and sediments between sampling sites with submerged macrophytes and sampling sites without submerged macrophytes. Moreover, lake water and sediments were mainly contaminated by As, Cr, and Pb. Potamogeton distinctus is a hyperaccumulator of Fe according to the threshold value for Fe hyperaccumulation. Many significantly positive correlations were found among metals and metalloids in submerged macrophytes due to co-accumulation. We found significant correlation between Cr in submerged macrophytes and Cr in water, and strong positive correlations between As, Cd, and Cu in submerged macrophytes and As, Cd, and Cu in corresponding sediments in the Yunnan Plateau lakes.

Conclusions

Submerged macrophytes have no significant effects on metal and metalloid concentrations in sediments and water in all the 20 Yunnan Plateau lakes in the study. However, further studies are necessary to understand the interactions of metals and metalloids in submerged macrophytes, water, and sediments.

     

Land contamination by toxic elements in abandoned mine areas in Italy

Purpose

The present paper concerns the distribution and mobility of heavy metals (Cu, Pb, Zn and Fe) in the soils of some abandoned mine sites in Italy and their transfer to wild flora.

Materials and methods

Soils and plants were sampled from mixed sulphide mine dumps in different parts of Italy, and the concentrations of heavy metals were determined.

Results and discussion

The phytoremediation ability of Salix species (Salix eleagnos, Salix purpurea and Salix caprea), Taraxacum officinale and P?lantago major for heavy metals and, in particular, zinc was estimated. The results showed that soils affected by mining activities presented total Zn, Cu, Pb and Fe concentrations above the internationally recommended permissible limits. A highly significant correlation occurred between metal concentrations in soils.

Conclusions

The obtained results confirmed the environmental effects of mine waste; exploring wild flora ability to absorb metals, besides metal exploitation, proved a useful tool for planning possible remediation projects.

     

Root-induced changes to soil water retention in permafrost regions of the Qinghai-Tibet Plateau,China

Purpose

Soil water retention plays a crucial role in regulating soil moisture dynamics, water circulation, plant growth, contaminant transport, and permafrost stability, and it is an issue of concern in water-limited ecosystems. However, our understanding of the relationship between plant roots and soil water retention is still relatively poor in the alpine grasslands of permafrost regions. To addresses this, our study evaluated the effect of plants on the soil water retention in permafrost regions of the Qinghai-Tibet Plateau.

Materials and methods

Three alpine grassland sites were identified and characterized as alpine wet meadow (AWM), alpine meadow (AM), and alpine steppe (AS). Root biomass, soil water retention, and soil physico-chemical properties were examined in the top 0–50 cm of active layer in the three experimental sites in the hinterland of the Qinghai-Tibet Plateau (QTP). Pedotransfer functions (PTFs) and Retention Curve program (RETC) were employed to illustrate how the plant roots affect soil water retention.

Results and discussion

Approximately 80, 65, and 60% of root biomass was distributed in the top 0–20 cm in the AWM, AM, and AS soil, respectively. Soil water retention was enhanced with the presence of plant roots; thereinto, the highest values of field capacity were found in AWM soil: on average, about 0.45 cm³ cm^?3. Field capacity of AWM soil was almost twice as high as that of AM soil, and triple higher than that of AS soil. Correlation and regression analysis showed that root-induced changes to soil water retention were caused by altering the soil organic matter and soil structure. In addition, we evaluated the Retention Curve (RETC) program’s performance and found that the program underestimated soil water retention if the effects of plant roots were not considered.

Conclusions

A lack of alpine plants is associated with a decline in soil physical conditions and soil water retention in permafrost regions, and the function of plant roots should be considered when predicting hydrological processes.

     

Metal tolerance in barley and wheat cultivars: physiological screening methods and application in phytoremediation

Purpose

The objective of the study was to evaluate the tolerance of barley (Hordeum vulgare) and wheat (Triticum aestivum) in soil contaminated with different concentrations of Cd and Cr, the effect of these metals on some physiological characteristics and the biomass produced in order to assess their potential application in phytoremediation of contaminated soils.

Materials and methods

A greenhouse experiment using two cultivars of barley, CB502 and Pedrezuela, and one of wheat, Albares, was conducted. The pots were watered with different concentrations of Cd or Cr during the period of plant growth. Cellular membrane damage, content and fluorescence of chlorophyll, and plant biomass were evaluated. After harvesting, the content of metals in the roots, shoots and grains was analysed as well as the available metal concentration in soil samples.

Results and discussion

The results show that the Cd treatments did not significantly affect the growth and physiology of the plants, but they were affected by the Cr treatments. At the highest concentration of Cr, the decrease in chlorophyll content compared to the control was 44, 77 and 83 % for the CB502 and Pedrezuela barleys and the Albares wheat respectively. A reduction in biomass was also observed (74, 81 and 85 % respectively). The amount of Cd and Cr accumulated in the root was higher than that accumulated in the aerial part for the three cultivars. The barleys accumulated the highest amount of metal in the roots. The transfer factor was lower in barley than in the wheat for both metals.

Conclusions

Cadmium treatments do not affect plant development. In the case of Cr, plant development and physiological traits were significantly affected. For the highest concentration of Cr, the CB502 barley had the highest tolerance index, 26 %, and the Albares wheat had the lowest one, 15 %. The two barleys were more effective in phytoremediation of soil contaminated with Cd or Cr than the wheat, presenting a higher tolerance to these metals in the assayed conditions.

     

Assessment of loose and adhered urban street sediments and trace metals: a study in the city of Poços de Caldas,Brazil

Purpose

This study aims to quantify and characterise sediments accumulated in the street gutters in an urban area of Poços de Caldas, Brazil. The main research questions are: What type of urban areas, e.g. those under construction, produce most sediments and what are the main characteristics of such sediments? What differences, e.g. granulometry, can be found in loose and adhered sediments? What trace metals can be found in the sediments?

Materials and methods

Fieldwork was carried out in a residential area of Poços de Caldas, Brazil. Ten samplings were conducted between May and August 2013 to collect sediments from road gutters. The collected sediments were then divided into ‘loose’ and ‘adhered’, depending on whether they were collected in a first, gentle, sweeping with soft bristled brush or in a subsequent sweeping with a stiff bristled brush. Granulometric curves were drawn for both types of sediments. Fine sediment analyses (≤63 μm) were performed on samples from the last five samplings. Two techniques were used to look for trace elements: energy dispersive X-ray fluorescence (EDXRF) and inductively coupled plasma-atomic emission spectrometry (ICP-AES).

Results and discussion

Larger amounts of sediments were collected after lower intensity rainfall events. Higher intensity events seemed to wash the sediments away. A correlation was found between areas under construction and sediment mass production. A characteristic range of granulometries (medium sand), found in our study is in accordance with studies by other authors. An important presence of heavy metals (Cr, Cd, Pb, Zn, Ni and Cu) was detected and characterised. As and Sn were also detected even though they are not often mentioned in the literature on urban soil pollutants.

Conclusions

Areas under construction were found to produce more sediments than other areas. The trace metals found in highest concentrations were Pb and As. The heavy metal concentration decreases after wet periods, showing that they are carried by runoff. It is expected that this study may serve as an input for establishing diffuse pollution control and mitigation strategies for the accumulation of pollutants in the urban environment.