Linking heavy metal bioavailability (Cd, Cu, Zn and Pb) in Scots pine needles to soil properties in reclaimed mine areas

Multistage stabilization of Cd, Pb, Zn, Cu and As in contaminated soil by phosphorus-coated nZVI layered composite materials: characteristics, process and mechanism

This study developed a shell-like slow-release material, PF@ST/Fe-0.5, by encapsulating nanoscale zero-valent iron composites (NZC) with phosphate fertilizer (PF) and a starch binder (ST). The material dissolved in soil in stages, first releasing P and Ca to increase the soil pH from 4.95 to 7.14. This was followed by the formation of phosphates and hydroxides precipitates with Pb, Cu, Zn, and Cd in soil, reducing their bioavailable forms by 81.73 %, 79.58 %, 91.05 %, and 86.47 %, respectively. The process also involved the competitive adsorption between PO43-/HPO42- and arsenate/arsenite led to the release of specifically adsorbed arsenic, increasing the probability of reaction with the material. Afterwards, the exposure of the NZC core reacted with arsenate/arsenite to form ferric arsenates, thus reducing the content of bioavailable arsenic in the soil by 73.57 %. Excess PO43- and alkali metal cations were captured and mineralized by the iron (hydro) oxides and reactive silicates in NZC, enhancing the remediation effect. Furthermore, the wet-dry alternation test had demonstrated the adaptability of PF@ST/Fe-0.5 to the rainy dry-wet soil environment in Yunnan, which enabled the bioavailable content of As, Pb, Cu, Zn, and Cd decreased by 71.2 %, 94.8 %, 84.1 %, 79.8 %, and 83.9 %, respectively. The layered structure minimized internal reactive substance consumption and protected the internal nZVI from oxidation. The phased release of phosphate and Fe0 stabilized Pb, Cu, Zn, and Cd, enhancing As stabilization and providing a new perspective for the synchronous stabilization of soil contaminated.

The environment as the first victim: The impacts of the war on the preservation areas in Ukraine

The war in Ukraine has had a devastating impact on the environment. Military actions have caused the release of hazardous substances into the environment, such as pollutants and toxic chemicals, that have contaminated the water, soil, and air, posing a threat to both human health and the environment. This has resulted in widespread destruction and contamination of natural habitats and resources and has disrupted wildlife populations and ecosystems. The impacts of military activity on the soils of protected areas are particularly critical, as they are the basis of biotic and landscape diversity and require special management and scientifically based monitoring measures even in peaceful conditions. In this context, this communication paper aims to provide an overview of the impacts of the war on the soils in four Ukrainian protected areas, namely Chornobyl Radiation and Ecological Biosphere Reserve; Desniansko-Starohutskyi National Nature Park; Holosiivskyi National Nature Park, and Hetmanskyi National Nature Park. To address these aspects, this paper combined GIS analysis and secondary data including soil samples obtained during field expeditions, to provide evidence of how ground battles, occupation, terrestrial land mines, and explosions can severely impact the soils. Practical and theoretical implications of the military actions are also discussed.

Receptor model-based source-specific health risks of toxic metal(loid)s in coal basin-induced agricultural soil in northwest Bangladesh

Toxic metal(loid)s (TMLs) in agricultural soils cause detrimental effects on ecosystem and human health. Therefore, source-specific health risk apportionment is very crucial for the prevention and control of TMLs in agricultural soils. In this study, 149 surface soil samples were taken from a coal mining region in northwest Bangladesh and analyzed for 12 TMLs (Pb, Cd, Ni, Cr, Mn, Fe, Co, Zn, Cu, As, Se, and Hg). Positive matrix factorization (PMF) and absolute principal component score-multiple linear regression (APCS-MLR) receptor models were employed to quantify the pollution sources of soil TMLs. Both models identified five possible sources of pollution: agrochemical practice, industrial emissions, coal-power-plant, geogenic source, and atmospheric deposition, while the contribution rates of each source were calculated as 28.2%, 17.2%, 19.3%, 19% and 16.3% in APCS-MLR, 22.2%, 13.4%, 24.3%, 15.1% and 25.1% in PMF, respectively. Agrochemical practice was the major source of non-carcinogenic risk (NCR) (adults: 32.37%, children: 31.54%), while atmospheric deposition was the highest source of carcinogenic risk (CR) (adults: 48.83%, children: 50.11%). NCR and CR values for adults were slightly higher than for children. However, the trends in NCR and CR between children and adults were similar. As a result, among the sources of pollution, agrochemical practices and atmospheric deposition have been identified as the primary sources of soil TMLs, so prevention and control strategies should be applied primarily for these pollution sources in order to protect human health.

Synchronous stabilization of Pb, Zn, Cd, and As in lead smelting slag by industrial solid waste

In order to prevent heavy metal (HM) pollution from lead smelting slag (LSS) to the surrounding environment, this work investigated the feasibility, influencing factors, and mechanisms of using industrial solid waste such as fly ash (FA), oil sludge pyrolysis residue (PR), and steel slag (SS) as remediation amendments. The results demonstrated that the stabilization process was influenced by the material dosage, water content, and LSS particle size. Compared to single materials, the combination amendment PR2FA1 (with a mass ratio of PR to FA as 2:1) exhibited the best stabilization effect, simultaneously reducing the leaching concentrations of As, Zn, Cd, and Pb in LSS to 0.032, 0.034, 0.002, and 0.014 mg/L, respectively. The pH value of the leachate remained between 8 and 9, which met the requirements of surface water quality class IV (GB3838-2002). Through morphological analysis, microscopic characterization, and simulated solution adsorption experiments, it was determined that the stabilization process of HMs was controlled by various mechanisms, including electrostatic attraction, physical adsorption, ion exchange, and chemical precipitation. PR2FA1 had more active components, and its fine-porous structure provided more active sites, resulting in good stabilization performance for As, Zn, Cd, and Pb. Furthermore, cost analysis showed that PR2FA1, as an environmentally friendly material, could generate profits of 157.2 ¥/ton. In conclusion, the prepared PR2FA1 not only addressed the HMs pollution from lead smelting slag to the surrounding environment but also achieved the safe and resourceful disposal of hazardous waste-oil sludge. Its excellent performance in stabilizing HMs and cost-effectiveness suggested promising commercial applications.

Variability in Water Capacity of Small-Leaved Linden Associated with Both the Presence of Honeydew and Various Sources of Pollution

The process of water retention on the surface of the assimilation apparatus of plants is inextricably linked with the water capacity of tree crowns and depends mainly on the condition of the leaf itself. The main objective of the present study was to investigate how the honeydew coverage and the location of trees related to the content of polycyclic aromatic hydrocarbons affected the differences in the capability of small-leaved linden leaves to capture water. Honeydew coverage was determined with the use of AutoCAD, whereas the content of polycyclic aromatic hydrocarbons was determined using gas chromatography. The value of S (water capacity) was much lower before the appearance of honeydew on the leaf than at the peak moment of honeydew collection. This is due to the hydrophobic properties of the substance. It was also found that the content of polycyclic aromatic hydrocarbons (PAH) in leaves varied depending on the distance of trees from pollution sources, and it was found that the amount of PAHs increased with the growth of honeydew on leaves and in locations exposed to pollution. The highest S and the total amount of PAHs occurred with the combination of the largest amount of pyrogenic impurities with the highest amount of honeydew. Combing pollutants from the air by plants is a very important function, but it may also change the physical properties of leaves, such as wettability.

Impact of potentially toxic elements on pines in a former ore processing mine: Exploitation of hyperspectral response from needle and canopy scales

Anthropic potentially toxic element (PTE) releases can lead to persistent pollution in soil. Monitoring PTEs by their detection and quantification on large scale is of great interest. The vegetation exposed to PTEs can exhibit a reduction of physiological activities, structural damage … Such vegetation trait changes impact the spectral signature in the reflective domain 0.4-2.5 μm. The objective of this study is to characterize the impact of PTEs on the spectral signature of two pine species (Aleppo and Stone pines) in the reflective domain and ensure their assessment. The study focuses on nine PTEs: As, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Zn. The spectra are measured by an in-field spectrometer and an aerial hyperspectral instrument on a former ore processing site. They are completed by measurements related to vegetation traits at needle and tree scales (photosynthetic pigments, dry matter, morphometry …) to define the most sensitive vegetation parameter to each PTE in soil. A result of this study is that chlorophylls and carotenoids are the most correlated to PTE contents. Context-specific spectral indices are specified and used to assess metal contents in soil by regression. These new vegetation indices are compared at needle and canopy scales to literature indices. Most of the PTE contents are predicted at both scales with Pearson correlation scores between 0.6 and 0.9, depending on species and scale.

Migration, accumulation, and risk assessment of potentially toxic elements in soil-plant (shrub and herbage) systems at typical polymetallic mines in Northwest China

In grassland systems of the semi-arid mining area, the migration, accumulation, and bioavailability of potentially toxic elements (PTEs) are important ecological and health risk issues. Thirty-eight pairs of topsoil (0-20 cm) and plant samples were collected around Baiyin City and in Dongdagou stream valley to investigate the migration of PTEs in soils, transfer of PTEs in soil-plant (shrub and herbage) systems, and assess the risk in soils and plants. The total concentrations of PTE (Hg, As, Cu, Zn, Cd, and Pb) were analyzed following digestion in mixture acid solution, and bioavailable PTE was extracted with a strong chelating agent (DTPA-TEA-CaCl₂). The transfer factor (TF) and bioaccumulation factor (BCF) were calculated to examine the migration of PTEs in soil-plant. Hazard quotient (HQ) and total hazard index (THI) were calculated to assess the risk and migration of PTEs in soils. The results showed that PTEs in soils and plants of study area exceeded the soil background value and Hygienic Standard for Feeds. Correlation among the total Hg, As, Cu, Zn, Cd, and Pb in soils of Dongdagou stream valley was significant at p < 0.01. A good correlation was exhibited between PTEs in root/aboveground parts of plants and DTPA-soil extractable. Difference of TF and BCF was existed between Dongdagou stream valley and around Baiyin City. Hg, Cu, Zn, Cd, and Pb were mainly accumulated in soils near the mining area. The calculated THI exceeded 1, and As and Pb were the major risk factors. The ability to absorb and transfer Hg, As, Cu, and Pb of plants was lower in more serious polluted area. As had a stronger migration capacity in study area. PTEs in soils had an adverse health effect for residents, and PTEs in plants may cause toxicity to cattle and sheep.

Cellulosic pine needles-based biorefinery for a circular bioeconomy

Pine needles (PNs) are one of the largest bio-polymer produced worldwide. Its waste, i.e., fallen PNs, is mostly responsible for forest fires and is a major challenge. In present article, we have reviewed differenteffortsmadeto tackle this situation. PNs have been used in various fields such asin composite, water purification industries,electronic devices, etc. Gasification is one of the appealing processes for turning PNs into bio-energy; pyrolysis technique has been employed to create various carbon-based water purification materials; saccharification combined with fermentation produced good yields of bio-ethanol; Pd or Ni/PNs biocatalyst showed good catalytic properties in variousreactionsand pyrolysis with or without catalyst is an alluring technique to prepare bio-fuel. Nano cellulose extracted from PNs showed appealing thermal and mechanical strength. The air quality of nearbyenvironment was examinedby studying the magnetic properties of PNs. Packing materials made of PNs showed exceptional ethylene scavenging abilities.

Study of Chemical Pollutants and Ecological Reconstruction Methods in the Tismana I Quarry, Rovinari Basin, Romania

The phytoremediation of polluted land in Romania is based on research on biodiversity, environmental protection, and the sustainable use of natural or man-made resources, carried out by universities and research institutes for over 30 years, synchronized with those at the European and global level. The aim of this paper is to establish the categories of pollutants with potential environmental, economic, and social impacts associated with mining in order to choose the optimal method of ecological reconstruction. In this regard, the Tismana quarry was mapped, the surface of the analysis plot was set at 50 m × 50 m, and the sampling depth was 0–20 cm; from each plot, two samples were collected. Out of a total of 121 analysis plots, ten susceptible plots were identified, from which 20 samples were collected and analyzed. The samples were analyzed by the UV-VIS spectrophotometer method—MLUV1720 and UV spectrometry—with a SHIMADZU UV 160U spectrophotometer; they indicated in only three analysis plots a pollution with phenols, Ni, Zn, Ni and HAP, the concentrations of which exceeded only the normal values, which does not affect the eaves threshold and intervention for the type of land use. Being point pollution, the phytoremediation of these soils can be achieved in a short time. The paper aims to present the situation of chemical pollutants in the Tismana quarry area, and to offer different ecological rehabilitation solutions depending on their presence.

Assembly of root-associated bacterial community in cadmium contaminated soil following five-year consecutive application of soil amendments: Evidences for improved soil health

Soil amendments have been extensively used to remediate heavy metal contaminated soils by immobilizing or altering edaphic properties to reduce the bioavailability of heavy metals. However, the potential influences of long-term soil amendments applications on microbial communities and polluted soil health are still in its infancy despite that have been applied for decades. We used amplicon sequencing and q-PCR array to characterize the root-associated microbial community compositions and rhizosphere functional genes in a five-year field experiment with consecutive application of four amendments (lime, biochar, pig manure, and a commercial Mg-Ca-Si conditioner). Compared with the control, soil amendments reduced the available Cd (CaCl₂ extractable Cd) in soils and strongly affected bacterial community compositions in four root-associated niches. Five rare keystone bacterial species were found belonging to the family Gallionellaceae (1), Haliangiaceae (1), Anaerolineaceae (2), and Xanthobacteraceae (1), which significantly correlated with soil pH and the functional genes nifH and phoD. Random forest analysis showed that rhizosphere soil pH and microbial functions, and root-associated keystone bacterial community compositions mainly influenced the Cd concentrations in rice grains. Altogether, our field data revealed five-year consecutive application of soil amendments regulated root-associated microbial community assembly and enhanced microbial functions, thereby improved rhizosphere health of Cd-contaminated soils.

Key Cr species controlling Cr stability in contaminated soils before and chemical stabilization at a remediation engineering site

Linking chromium (Cr) speciation with its stability in soils is vital because insoluble Cr(VI) and chemically adsorbed Cr(VI) could hinder the remediation efficiency and release Cr(VI) for a prolonged period of time. In this study, we investigated key Cr species to probe the mechanisms controlling the release of insoluble Cr(VI) at Cr-contaminated sites using synchrotron-based X-ray absorption near-edge structure (XANES) for the first time. Chromite, stichtite and Cr-silicate were predominant forms of Cr(III). Insoluble Cr(VI) was hosted by layered double hydroxides (LDHs) such as brownmilerite and hydrotalcite. Anion competition tests documented a substitution of absorbed Cr(VI) by SO₄^2- and NO₃^-. Acid extraction released 6.7-25.7% more Cr(VI) than anion extraction, possibly attributing to the erosion of LDH and CaCrO₄ in calcite rather than Cr-bearing minerals. Brown and red soils released maximally 62% and 44% of total Cr(VI) by 10 mol/(kg soil) and 2 mol/(kg soil) of H⁺, respectively. SO₄^2-, H₂O and H⁺ contributed to more release of total Cr(VI) in brown soils (22%, 33% and 7%) than red soils (25%, 17% and 2%). More crystalline Cr structures were found after chemical stabilization, indicating a higher Cr stability in chemically stabilized soils. Cr and Mn exhibited an overlapped distribution pattern in both contaminated and chemically stabilized soils, hinting at the re-oxidation of Cr(III). Insoluble Cr(VI) could be released by acidic rainfalls and soil organic matters, posing potential threats to Cr long-term stability in field-scale remediation.

Potentially Toxic Elements’ Contamination of Soils Affected by Mining Activities in the Portuguese Sector of the Iberian Pyrite Belt and Optional Remediation Actions: A Review

Both sectors of the Iberian Pyrite Belt, Portuguese and Spanish, have been exploited since ancient times, but more intensively during and after the second half of the 19th century. Large volumes of polymetallic sulfide ore were extracted in open pits or in underground works, processed without environmental concerns, and the generated waste rocks and tailings were simply deposited in the area. Many of these mining sites were abandoned for years under the action of erosive agents, leading to the spread of trace elements and the contamination of soils, waters and sediments. Some of these mine sites have been submitted to rehabilitation actions, mostly using constructive techniques to dig and contain the contaminated tailings and other waste materials, but the remaining soil still needs to be treated with the best available techniques to recover its ecosystem functions. Besides the degraded physical structure and poor nutritional status of these soils, they have common characteristics, as a consequence of the pyrite oxidation and acid drainage produced, such as a high concentration of trace elements and low pH, which must be considered in the remediation plans. This manuscript aims to review the results from studies which have already covered these topics in the Iberian Pyrite Belt, especially in its Portuguese sector, considering: (i) soils’ physicochemical characteristics; (ii) potentially toxic trace elements’ concentration; and (iii) sustainable remediation technologies to cope with this type of soil contamination. Phytostabilization, after the amelioration of the soil’s properties with organic and inorganic amendments, was investigated at the lab and field scale by several authors, and their results were also considered.

Comparison of non-destructive techniques and conventionally used spectrometric techniques for determination of elements in plant samples (coniferous leaves)

Conventionally used spectrometric techniques of inductively coupled plasma optical emission spectrometry (ICP-OES) and inductively coupled plasma optical emission spectrometry (ICP-MS) usually involve time-consuming sample preparation procedure of a sample dissolution which requires the usage of aggressive and toxic chemicals. The need for suitable and sustainable analytical methods for direct multi-elemental analysis of plant samples has been increased in recent years. Spectrometric techniques for direct sample analysis, instrumental neutron activation analysis (INAA) and X-ray fluorescence (XRF) have been applied in environmental studies and various fields of screening tests. Nevertheless, these techniques are not commonly used for plant sample analysis and their performances need to be evaluated. This research aimed to assess how reliable non-destructive techniques are in the determination of elements in plants compared to conventionally used spectrometric techniques. A total of 49 plant samples of four conifer species (Pinus nigra, Abies alba, Taxus baccata and Larix decidua) were measured using two conventionally applied (ICP-MS, ICP-OES) and two non-destructive techniques (wavelength dispersive XRF (WD-XRF), INAA). The comparison was performed by investigation of relative ratios of concentrations and by correlation analysis. Moreover, precision of the techniques was examined and compared. The quality control included analysis of NIST pine needles certified reference material (1575a) using all examined techniques. Our results suggest that additional analytical and quality control steps are necessary for reaching the highest accuracy of multi-elemental analysis.

Crop straw-derived biochar alleviated cadmium and copper phytotoxicity by reducing bioavailability and accumulation in a field experiment of rice-rape-corn rotation system

Biochar has the potential to control the bioavailability and transformation of heavy metals in soil, thereby ensuring the safe crop production. A three seasons field experiment was conducted to investigate the effect of crop straw-derived biochar on the bioavailability and crop accumulation of Cd and Cu in contaminated soil. Wheat straw biochar (WSB), corn stalk biochar (CSB), and rice husk biochar (RHB) were applied at the rate of 0, 1.125, and 2.25 × 10⁴ kg ha^-1, respectively. The results showed that all types of biochar significantly increased soil pH, organic carbon and cation exchangeable capacity (CEC), compared to the control. The reduction in DTPA extractable Cd and Cu contents was much greater under high dosage biochar application, with a prominence at RHB treatment throughout the three cropping seasons, compared to the control. Moreover, the biological accumulation of Cd and Cu in the grains of rapeseed and corn significantly decreased after biochar application. Linear regression also confirmed the effective role of biochar in controlling the translocation and accumulation of Cd and Cu due to their inactive bioavailability. In addition, the sequential extraction indicated that exchangeable fraction (EXF) of Cu and Cd had decreased, while residual fraction (RSF) had increased under all biochar amendments. Contrarily, the oxidizable fraction (OXF) of Cd decreased while OXF of Cu increased under biochar treatments. Biochar application, especially RHB, could be an effective measure to enhance Cd and Cu adsorption and immobilization in polluted soils and thereby reducing its uptake and translocation to crops.

Heavy metal accumulation of urban Scots pine (Pinus sylvestris L.) plantation

In soil and plant tissues, the concentrations and reserves of manganese (Mn), zinc (Zn), nickel (Ni), copper (Cu), and lead (Pb) were calculated to measure the heavy metal quantities of the Scots pine afforestation. In the soil and plant tissues, heavy metal concentrations varied. The highest concentration of heavy metal was found in Mn and the lowest concentration in Pb in the soil. Heavy metal stocks followed the order of Mn > Zn > Ni > Cu > Pb in soil, and the order of Zn > Cu > Mn > Ni > Pb in the plant. In the Scots pine parts, Pb and Zn concentrations and BCFs follow Needle > Branch > Bark > Root > Trunk order, while Cu concentrations follow Root > Needle > Branch > Bark > Trunk order, Mn concentrations follow Needle > Branch > Bark > Trunk > Root order and Ni concentrations follow Needle > Branch > Root > Bark > Trunk order. In particular, Scots pine needles are considered to be ideal to be used as biomonitoring plants, especially in monitoring increases in heavy metal concentrations in urban areas. Besides, in order to be more effective in the retaining of heavy metals, it is proposed that mixtures of hyperaccumulator plants be added which are appropriate for climatic conditions.

The role of plants and soil properties in the enzyme activities of substrates on hard coal mine spoil heaps

Knowledge about biotic (plant species diversity, biomass) and/or abiotic (physicochemical substrate parameters) factors that determine enzyme activity and functional diversity of the substrate on hard coal spoil heaps is limited. Spontaneously developed vegetation patches dominated by herbaceous species commonly occurring on these spoil heaps: grasses (Poa compressa, Calamagrostis epigejos) and forbs (Daucus carota, Tussilago farfara), were examined. The activity of dehydrogenase and alkaline phosphatase was twice as high in plots dominated by grass species compared with those dominated by forbs. Significant positive correlations were found between the activity of dehydrogenase and alkaline phosphatase with pH, available P, soil moisture, and water holding capacity and negative correlations between the activity of urease and soil organic carbon. Strong positive correlations were found between values for Shannon–Wiener diversity index, evenness, species richness and soil functional diversity in plots dominated by grasses. We found that the soil physicochemical parameters had a greater impact on enzyme activity of the substrate than plant biomass and species diversity. However, grasses, through their extensive root system, more effectively increased enzyme activity and health of the substrate than other herbaceous species, and as they stabilize the substrate and form dense plant cover, they can be recommended for reclamation purposes.

Risk Assessment of Potential Food Chain Threats from Edible Wild Mushrooms Collected in Forest Ecosystems with Heavy Metal Pollution in Upper Silesia, Poland

In this study, the contents of selected heavy metals (Zn, Cu, Cd, Pb, Cr, and Ni) and macroelements (C, N, K, P, S, Mg, Na, and Ca) were measured in wild mushrooms growing in a heavily polluted forest ecosystem in the northeastern part of the Upper Silesian Industrial Region. The research was conducted on 10 species of mushrooms belonging to three families: Boletaceae, Russulaceae, and Suillaceae. Using a spatial autoregressive model, the study showed a strong relationship between heavy metal concentrations (especially Zn, Pb, and Cd) and the distance from a source of industrial pollution (a zinc smelter, Huta Miasteczko Śląskie). The concentrations of potentially toxic metals (Pb and Cd) in mushrooms significantly exceeded food-acceptable standards. The bioconcentration factor (BCF), calculated as the ratio between the concentration in mushroom tissues and in forest soils overall, reached the highest values for cadmium (Cd). The highest accumulation capacity for Cd was noted for Imleria badia (BCF = 9.18), which was also the most abundant mushroom species in the study plots. In general, the established threshold values for Pb and Cd concentrations in consumer mushrooms and food products were exceeded up to almost 30-fold in the studied area. We conclude that the potential risk to human health of the toxic elements that enter the food chain through the harvesting and consumption of wild mushrooms from this region is significant.

Facing the threat: common yellowjacket wasps as indicators of heavy metal pollution

We investigated the common wasp, Vespula vulgaris as a bioindicator and biomonitor of metals in the industrial area. Using traps, we collected 257 yellowjackets along a pollution gradient in the Harjavalta Cu-Ni smelter in Southwest Finland. Our method detected metal elements such as arsenic (As), cobalt (Co), copper (Cu), iron (Fe), nickel (Ni), lead (Pb), zinc (Zn), and mercury (Hg) in wasps. The data analyses revealed V. vulgaris can be a proper indicator for As, Cd, Co, Cu, Ni, and Pb, rather than for Fe and Zn contamination. Body burdens of As, Cd, Co, Cu, Ni, and Pb decreased with an increase in distance from smelter. Enrichment factor (EF) followed the pattern Pb ˃ Cd ˃ As ˃ Co ˃ Cu ˃ Ni. The highest bioaccumulation (BAF) values were revealed for Cd (5.9) and the lowest for Pb (0.1). Specially designed software (WaspFacer) allowed revealing body burdens of As, Cd, Co, Cu, Ni, and Pb to be associated with rather smaller than more asymmetric facial colour markings in yellowjackets. These results add to the body of literature on how heavy metal contaminants can have tangible phenotypic effects on insects and open future opportunities for using wasps as indicators of metal pollution.

Rice intercropping with alligator flag (Thalia dealbata): A novel model to produce safe cereal grains while remediating cadmium contaminated paddy soil

Phytoremediation has been employed as a cost-effective technique to remove the cadmium (Cd) from soil and water in several ecosystems. However, little is known about whether intercropping the remediating plants with rice (Oryza sativa) crop could reduce Cd accumulation in rice grains. We conducted greenhouse pot and concrete pond trials to explore the effects of intercropping alligator flag (Thalia dealbata, Marantaceae) on soil Cd remediation, paddy soil and microbial properties, and rice production. Our results suggest that intercropping with alligator flag significantly decreased Cd absorption, transportation, and accumulation from the soil to the rice grains (under 0.2 mg kg^-1 at a soil Cd content below 2.50 mg kg^-1). This decrease was due to the lowered Cd availability and higher soil pH in the rice-alligator flag intercropping system. Although planting alligator flag resulted in the reduction of soil NH₄-N and NO₃-N, Cd content in the rhizosphere was the main factor restricting microbial biomass, species, and community composition. Alligator flag could tolerate higher Cd contamination, and accumulate and stabilize more Cd in its tissues than rice. Our study suggests that alligator flag intercropped with rice has potential as a phytostabilization plant to produce rice safely for human consumption in moderately Cd-contaminated soils.

Interactive effects of multiple heavy metal(loid)s on their bioavailability in cocontaminated paddy soils in a large region

Heavy metal(loid) pollution in large regions is often highly complex due to the coexistence and interactions of metal(loid)s and complex soil environments. However, the interaction effects of heavy metal(loid)s on their bioavailability in large regions remain obscure. Here, we identified the interaction effects of Pb, Cd and As on their bioavailability in cocontaminated paddy soils of Shaoguan City, China. The results showed that pH (12.40%) was the most important impact factor among the key soil properties of the pH, CEC, and SOM for the bioconcentration factor (BCF) of Cd. As the soil Pb content decreased and the soil Cd content increased, the interaction of soil Pb and Cd increased the BCF of Pb. As the soil Pb content increased and the soil Cd content decreased, the interaction of soil Pb and Cd increased the BCF of Cd. The synergistic interaction of Pb and Cd in soil promoted the accumulation of both Pb and Cd in rice under certain soil conditions. Specifically, when the average pH and CEC were below 6.19 ± 0.82 and above 7.23 ± 2.55 cmol (+)/kg, respectively, the average BCF of Cd varied from 0.70 ± 0.80 to 1.47 ± 0.62 due to the interactive effect of soil Cd and Pb on the BCF of Cd. When the average pH was above 6.19 ± 0.82 and the average SOM was below and above 27.12 ± 20.34 mg/kg, respectively, the corresponding average BCF of Cd varied from 0.70 ± 0.63 to 0.10 ± 0.26. As the average soil Cd and As contents increased, the interactive effect of soil As and Cd on the average BCF of As decreased. The negative interaction of As and Cd in soil mitigated As accumulation in rice at certain soil Cd and As contents. Our results suggest that to achieve the large-scale control of heavy metal(loid) pollution, the interactions among multiple metal(loid)s and soil properties should be considered.

Geoassessment of heavy metals in rural and urban floodplain soils: health implications for consumers of Celosia argentea and Corchorus olitorius vegetables in Sagamu, Nigeria

Vegetable gardening in floodplains in western Nigeria has assumed economic significance but with attendant pressure on urban field in the dry season. This study assessed soil properties and bioconcentration of cadmium (Cd), iron (Fe) and lead (Pb), in edible parts of Celosia argentea and Corchorus olitorius grown in floodplains. Soil and vegetable samples were collected at 20 m intervals from rural (Atoyo and Ewuga) and urban (GRA Rd. and Lafarge) floodplain gardens in Sagamu. Six samples were collected per location making a total of 24 samples each of soil and vegetable. Samples were analyzed for soil properties and heavy metal concentration in the vegetables. Transfer factor (TF), contamination factor (CF), daily intake of metals (DIM), health risk index (HRI) and geoaccumulation index (I_geo) were also determined. Soil properties varied significantly, with the highest soil concentration of Cd (0.91 mg kg^-1) and Fe (208.20 mg kg^-1) recorded at Lafarge. The highest soil Pb (223.77 mg kg^-1) was at Atoyo. Bioaccumulation of Fe was significantly (p ≤ 0.05) higher in C. argentea than C. olitorius. Heavy metal bioaccumulation beyond allowable limits was recorded for Cd (0.46 mg kg^-1) and Pb (49.30 mg kg^-1) by C. argentea and C. olitorius, respectively. Soil contamination was dominated by Cd at Lafarge and by Pb at Atoyo. The DIM and HRI indices indicated no risk of Cd, Fe and Pb consumption in the vegetables. Geoaccumulation index revealed that Lafarge and Atoyo soils were extremely contaminated with Cd and Pb, respectively. Leafy vegetables grown in urban and rural floodplain soils adjacent to waste dumpsite are accumulators of Cd and Pb with food poisoning as the consequence.

Sources, bioaccumulation, health risks and remediation of potentially toxic metal(loid)s (As, Cd, Cr, Pb and Hg): an epitomised review

The release of potentially toxic metal(loid)s (PTMs) such as As, Cd, Cr, Pb and Hg has become a serious threat to the environment. The anthropogenic contribution of these PTMs, especially Hg, is increasing continuously, and coal combustion in thermal power plants (TPPs) is considered to be the highest contributor of PTMs. Once entered into the environment, PTMs get deposited on the soil, which is the most important sink of these PTMs. This review centred on the sources of PTMs from coal and flyash and their enrichment in soil, chemical behaviour in soil and plant, bioaccumulation in trees and vegetables, health risk and remediation. Several remediation techniques (physical and chemical) have been used to minimise the PTMs level in soil and water, but the phytoremediation technique is the most commonly used technique for the effective removal of PTMs from contaminated soil and water. Several plant species like Brassica juncea, Pteris vittata and Helianthus annuus are proved to be the most potential candidate for the PTMs removal. Among all the PTMs, the occurrence of Hg in coal is a global concern due to the significant release of Hg into the atmosphere from coal-fired thermal power plants. Therefore, the Hg removal from pre-combustion (coal washing and demercuration techniques) coal is very essential to reduce the possibility of Hg release to the atmosphere.

Comparable effects of manure and its biochar on reducing soil Cr bioavailability and narrowing the rhizosphere extent of enzyme activities

Chromium (Cr) contamination is especially hazardous to soil biota. Application of manure and biochar has been frequently proposed to remediate Cr-contaminated soil. However, the understanding of mechanisms behind manure and biochar impacts on soil enzyme activities requires advanced visualization technologies. For the first time, we compared manure and its biochar influence on the spatial distribution of β-glucosidase, N-acetyl-glucosaminidase and phosphomonoesterase activities in Cr-contaminated soil using direct zymography. Maize was planted for 45 days in (a) soil mixed with manure, (b) soil mixed with manure-derived biochar and (c) soil without any addition. Soil pH decreased over 45 days, inducing an increase in acid soluble Cr. The concomitant decrease in β-glucosidase and N-acetyl-glucosaminidase activities explained the narrowing rhizosphere extent of enzyme activities by 13-44%, indicating that increased Cr bioavailability decreases microbial activities. A larger maize performance index and the greatest plant shoot/root ratio after biochar application suggested enhanced maize growth (p < 0.05). In contrast, manure induced the narrowest extent of β-glucosidase and phosphomonoesterase activities due to the addition of labile organic compounds and nutrients following its application. Our study emphasizes the importance of pH on Cr bioavailability and enzyme activities and demonstrates that biochar application is more ideally suited for remediating Cr-contaminated soil.

Responses of soil mite communities (Acari: Oribatida, Mesostigmata) to elemental composition of mosses and pine needles and long-term air pollution in Scots pine (Pinus sylvestris L.) stands

Air pollution is an important threat to biodiversity via deposition of high amounts of heavy metals or nutrients (macroelements). In forest ecosystems contamination can be found in plant tissues and the soil environment including soil mesofauna. However, there is little information on how it influences soil mesofauna. Hence, the aim of the study was to evaluate the reaction of soil mites (Acari: Oribatida, Mesostigmata) to long-term air pollution in mature pine (Pinus sylvestris L.) forests in southwestern Poland. The study was conducted in late autumn between October 2008 and 2010 in eight 5000 m² plots, each within a Scots pine stand. Concentrations of macroelements (C, N, S, Ca, Mg) and heavy metals (Cu, Cr, Cd, Ni, Pb, Zn) were measured in 40 samples of pine needles and 36 bryophyte samples. In total, 360 soil samples were collected for the soil mesofauna analysis. Results of the study include correlations between the sample plot, the year and the soil mite abundance. Among the macroelements analyzed, calcium affected the abundance of mite species the most. Soil mite communities from different forests were dominated by the same species, despite the fact that we found in total 150 mite species, among which there were 106 species of oribatid mites and 44 species of mesostigmatid mites. It seems that, among the elements analyzed, calcium plays the most important, positive role for mite communities. Magnesium had a positive effect on abundance of both mite groups, while nitrogen had a negative effect on diversity of oribatid and mesostigmatid mite communities. Our study indicated that oribatid and mesostigmatid mite communities are stable in areas of long-term contamination, as we did not observe distinct changes in structure and diversity of soil mite assemblages along the pollution gradient.

Significant Impacts of Both Total Amount and Availability of Heavy Metals on the Functions and Assembly of Soil Microbial Communities in Different Land Use Patterns

Land use change alters the accumulation of heavy metals (HMs) in soils and might have significant influence on the assembly and functions of soil microbial community. Although numerous studies have discussed the impacts of either total amounts or availability of metals on soil microbes in land change, there is still limited understanding on which one is more critical. In the present study, soils from three land use types (forest, mining field, and operating factory) located in Shaoguan city (Guangdong Province, China) were collected to investigate the impacts of soil HMs on soil enzyme activities and bacterial community structures. Mining activities remarkably increased the concentrations of HMs in soils, and land use patterns changed soil properties and nutrition level. Soil pH, total and available HMs (Cu, Pb, Zn, and Cd) and organic matters (SOM) were identified as the key influential factors shaping soil ecological functions (soil enzyme activities) and community assembly (bacterial community composition), explained by HMs accumulation and soil acidification caused by human activities. In addition, total amount and availability of some metals (Zn, Pb, Cu, and Cd) showed similar and significant effects on soil bacterial communities. Our findings provide new clues for reassessing the environmental risks of HMs in soils with different land use.

Using cadmium bioavailability to simultaneously predict its accumulation in crop grains and the bioaccessibility in soils

Single extraction procedures (SEPs) have been extensively conducted to determine Cd bioavailability (Cd-Bav) in soils. However, whether SEPs can simultaneously predict Cd accumulation in crop grains and bioaccessibility (Cd-Bac) in soils remains unclear. To assess their suitability, the Cd-Bav in 20 contaminated soils (containing 0.27-56.59 mg/kg Cd) determined by four SEPs (including DTPA, EDTA, HOAc and HCl) was compared with Cd concentrations in crop grains (wheat and rice) and Cd-Bac in soils (based on SBET and PBET assays). The results indicated that both Cd-Bav (0-103.2%) and Cd-Bac (0-110.4%) in soils varied greatly with the methods used. The Cd-Bav obtained from chelators (DTPA and EDTA) was generally greater in low-Cd soils but lower in high-Cd soils as compared to those obtained from acid solutions (HOAc and HCl). Regression analysis revealed that bioavailable Cd concentrations in soils were linearly correlated with Cd concentrations in wheat grains (R² = 0.88-0.91); however, no significant correlation was found for rice grains. The Cd-Bac in soils was significantly correlated with Cd-Bav obtained from HOAc (R² = 0.55-0.59) or HCl (R² = 0.60-0.68), but not with those obtained from chelators (DTPA and EDTA). Our data suggest that SEPs, particularly the HCl method, have great potential to simultaneously predict Cd accumulation in wheat grains and Cd-Bac in contaminated soils.

The use of vegetation, bees, and snails as important tools for the biomonitoring of atmospheric pollution-a review

The continuous discharge of diverse chemical products in the environment is nowadays of great concern to the whole world as some of them persist in the environment leading to serious diseases. Several sampling techniques have been used for the characterization of this chemical pollution, although biomonitoring using natural samplers has recently become the technique of choice in this field due to its efficiency, specificity, and low cost. In fact, several living organisms known as biomonitors could accumulate the well-known persistent environmental pollutants allowing their monitoring in the environment. In this work, a review on environmental biomonitoring is presented. The main sampling techniques used for monitoring environmental pollutants are first reported, followed by an overview on well-known natural species used as passive samplers and known as biomonitors. These species include conifer needles, lichen, mosses, bees and their byproducts, and snails, and were widely used in recent research as reliable monitors for environmental pollution.

Phytoremediation: Metal decontamination of soils after the sequential forestation of former opencast coal land

Phytoremediation through forestry may be an effective means for reducing the metal loading in lands reclaimed after surface-coal-mining in the UK. Planted with mixed woodland, the soil loading of 5 key metals (Zn, Cd, Mn, Pb and Cu) decreased, significantly and progressively, compared to soils left as grassland through a 14 year forestation chronosequence on land reclaimed from the former Varteg opencast coalmine, South Wales. Fourteen years after initial tree planting, soil metal loadings decreased by 52% for Cd (4.3 mg∙kg^-1 per year), 48% for Cu (2.1 mg∙kg^-1 per year), 47% for Zn (7.3 mg∙kg^-1 per year), 44% for Pb. (7.1 mg∙kg^-1 per year) and 35% for Mn (45 mg.kg-1 per year). Analysis of metal loadings in the leaves of Alnus glutinosa (L. Gaertn) (Common Alder) and Betula pendula (Roth) (Silver Birch) found both to be involved in metal uptake with birch taking up more Cd, Cu, Zn and Mn and Alder more Pb. Concentrations of Zn, Mn and Cd (Birch only) increased significantly in leaves from, but not in soils, under older plantings. Since different tree species take up metals at different rates, mixed plantings may be more effective in forest phytoremediation.

Effects of Urban-rural Atmospheric Environment on Heavy Metal Accumulation and Resistance Characteristics of Pinus tabulaeformis in Northern China

The washed and unwashed current (C) and previous year (C + 1) needles, branches and top soils of Pinus tabulaeformis trees were sampled at five sites Haitai industrial district (HT), Puji River (PJ), Fukang road (FK), Residential area (RA) and Baxian Mountain (BX) in Tianjin along an urban-rural gradient and analyzed for heavy metals (Cu, Mn, Zn, Pb and Cd) concentrations via ICP. C + 1 needles generally had higher Mn, Pb, Cd than C needles while the opposite was for Cu and Zn. Total Cu, Zn, Pb, Cd in soils peaked at HT and decreased at RA and BX. Heavy metals were generally higher in the unwashed needles than the washed needles at all sites. Meanwhile MDA, soluble sugar and free proline concentration in needles were increased with the increasing of heavy metal contents along the urban-rural gradient, further correlated with the heavy metal contents.

Restoration of Vegetation in Relation to Soil Properties of Spoil Heap Heavily Contaminated with Heavy Metals

The main objectives of our study were to evaluate soil contamination on a zinc-lead spoil heap in the Upper Silesian Industrial Region in southern Poland using pollution indices, and to investigate the relation between soil properties and the natural succession of vegetation. Organic carbon and nitrogen, pH, soil texture, base cations, and heavy metal content were analyzed in soil samples at depths of 0-15 cm below the organic horizon over a regular grid of 14 sampling plots. The contents of Zn, Pb, and Cd exceeded by several times the acceptable thresholds. Measurements of soil enzyme activity were used to evaluate the progress of vegetation development in relation to soil chemical properties. The results indicate that heavy metals had a significant impact on soil enzyme activity and the development of vegetation cover. High contents of Pb and Cd reduced enzyme activity, while this activity increased with increasing amounts of soil organic matter. Further, the accumulative capacities of heavy metals in needles of Scots pine (Pinus sylvestris L.) and aboveground biomass of bladder campion (Silene vulgaris (Moench) Garcke) were examined. A high accumulation of Zn, Pb, and Cd in the aboveground tissues of S. vulgaris indicated an unusual tolerance of this species to heavy metals and the possibility of using this species in phytoremediation of post-industrial sites.

Spatial distribution, mobility and bioavailability of arsenic, lead, copper and zinc in low polluted forest ecosystem in North-western Mexico

A geochemical-environmental mapping was carried for a low polluted forest in North-western Mexico (Santiago Papasquiaro mining area), as part of the North American forests accounting for environmental behavior of arsenic (As), lead (Pb), zinc (Zn) and copper (Cu) in soil and tree components (stem wood and aciculums). Spectroscopic and microscopic techniques along with standard protocols were used to determine the mineralogical phases containing these elements, and their corresponding spatial distributions in soil and forests and mobility. In soil, total As, Pb, Zn and Cu ranged from 4.9 to 98.3, 19.6 to 768.6, 19.6 to 407.1, and 1.6 to 63.8 mg kg^-1, respectively. Ultrafine particles (<5-10 μm) of arsenopyrite and sphalerite (and complex Zn-Fe phase) were the main As and Zn-bearing phases determined by SEM-EDS, respectively. Complex Pb-Cu-Fe and Cu-O oxide-like phases were the only ones containing Pb and Cu, respectively. Mobility was low for Pb, Zn and Cu, whereas a significant mobility was assessed for As. Concentrations vs. depth profiles suggested progressive accumulations of As, Pb, Zn and Cu in top soil. Total As, Pb, Zn and Cu in pine stem wood varied from 11.5 to 184.5, 98.9 to 7359.8, 3242.7 to 22197.3, 689.2 to 7179.6 μg kg^-1, respectively. The respective concentrations in the pine needles ranged from 50 to 624.2, 100 to 16353.1, 120 to 46440.9 and 720 to 7200 μg kg^-1, indicating an active bioaccumulation of As, Pb, Zn and Cu. A prospective environmental behavior was discussed for As, Pb, Zn and Cu in the low-polluted forest.

Chronological Variation of Metals in Reclaimed Coal Mine Soil and Tissues of Eucalyptus Hybrid Tree After 25 Years of Reclamation, Jharia Coal Field (India)

Fast-growing metal-accumulating woody trees are potential candidates for phytoremediation of coal mine overburden (OB) dumps. The present study assessed chronological variation in metals (Pb, Zn, Mn, Cu, and Co) concentration in reclaimed mine soil (RMS) and tissues (leaf, stem bark, stem wood, root bark and root wood) of Eucalyptus hybrid tree between 3 and 25-year old OB dumps (RMS3 and RMS25) from Jharia coal field (India). Total metal concentrations of Pb, Zn, and Cu in RMS25 were 1.55, 3.46, and 1.44 times lower (p < 0.05), respectively, than RMS3. Higher concentrations of total (110%-565%) and available form (DTPA-extractable) of metals (109%-480%) were observed in RMS25 than in control soil. Pb selectively accumulated in stem bark, Zn and Mn in leaves, and Cu and Co in root wood. Metal concentrations were higher (1.04-4.15 times at p < 0.05) in tree tissues growing on RMS25 than in RMS3. This study concluded that Eucalyptus hybrid could be utilized for reclamation of coal mine OB dumps.

Chemical speciation and risk assessment of cadmium in soils around a typical coal mining area of China

The distribution characteristics of Cadmium (Cd) fractions in soils around a coal mining area of Huaibei coalfield were investigated, with the aim to assess its ecological risk. The total Cd concentrations in soils ranged from 0.05 to 0.87 mg/kg. The high percentage of phyto-available Cd (58%) when redox or base-acid equilibria changed. Soil pH was found to be a crucial factor affecting soil Cd fraction, and carbonate-bound Cd can be significantly affected by both organic matter and pH of soils. The static ecological evaluation models, including potential ecological risk index (PERI), geo-accumulation index (I_geo) and risk assessment code (RAC), revealed a moderate soil Cd contamination and prensented high Cd exposure risk in studied soils. However, the dynamic evaluation of Cd risk, determined using a delayed geochemical hazard (DGH), suggested that our studied soils can be classified as median-risk with a mean probability of 24.79% for Cd DGH. These results provide a better assessment for the risk development of Cd contamination in coal mining areas.

Remediation techniques for heavy metal-contaminated soils: Principles and applicability

Globally there are over 20millionha of land contaminated by the heavy metal(loid)s As, Cd, Cr, Hg, Pb, Co, Cu, Ni, Zn, and Se, with the present soil concentrations higher than the geo-baseline or regulatory levels. In-situ and ex-situ remediation techniques have been developed to rectify the heavy metal-contaminated sites, including surface capping, encapsulation, landfilling, soil flushing, soil washing, electrokinetic extraction, stabilization, solidification, vitrification, phytoremediation, and bioremediation. These remediation techniques employ containment, extraction/removal, and immobilization mechanisms to reduce the contamination effects through physical, chemical, biological, electrical, and thermal remedy processes. These techniques demonstrate specific advantages, disadvantages, and applicability. In general, in-situ soil remediation is more cost-effective than ex-situ treatment, and contaminant removal/extraction is more favorable than immobilization and containment. Among the available soil remediation techniques, electrokinetic extraction, chemical stabilization, and phytoremediation are at the development stage, while the others have been practiced at full, field scales. Comprehensive assessment indicates that chemical stabilization serves as a temporary soil remediation technique, phytoremediation needs improvement in efficiency, surface capping and landfilling are applicable to small, serious-contamination sites, while solidification and vitrification are the last remediation option. The cost and duration of soil remediation are technique-dependent and site-specific, up to $500ton^-1 soil (or $1500m^-3 soil or $100m^-2 land) and 15years. Treatability studies are crucial to selecting feasible techniques for a soil remediation project, with considerations of the type and degree of contamination, remediation goals, site characteristics, cost effectiveness, implementation time, and public acceptability.

Influence of F1 hybridization on the metal uptake behaviour of pine trees (Pinus nigra x Pinus thunbergiana; Pinus thunbergiana x Pinus nigra)

Pine needles have been considered to be useful bio-indicators for air pollution. This phenomenon can be used for environmental studies for monitoring purposes. Additionally, this fact offers the possibility to study uptake and accumulation behaviour not only in different species, but also in hybrids obtained from common pine trees to inheritage processes. Therefore, needles of Pinus nigra Arnold and Pinus thunbergiana Franco as well as of their F1 hybrids were investigated for essential and non-essential metals, such as Al, B, Ba, Ca, Cd, Co, Cu, Cr, Fe, K, Mg, Mn, Mo, Na, Ni, Pb, Sr, and Zn. The samples underwent acidic microwave-assisted digestion prior to analysis inductively coupled plasma atomic emission spectrometry (ICP-AES). Furthermore flavonoids were quantitatively determined to prove hybrid character. Regarding all determined analytes, increase and decrease of uptake in the needles of the hybrids were evaluated in comparison to the needles of the parent pine species to see which parent is the dominant one. In the hybrids higher amounts of Al, Cd, Mo, Ni, Mg, Mn, and Zn were found. Different behaviour was registered for flavonoids than for metals, due to different metabolic pathways.

Remediation Potential of Forest Forming Tree Species Within Northern Steppe Reclamation Stands

The aim of the research was to study the features of accumulation of heavy metals by assimilation apparatus of coniferous and deciduous arboreous plants. The research identified excess of factual concentrations for Arsenic in mining rock in relation to values stated in IPC (indicative permissible concentrations). It is stated that the metals can be divided into three groups according to their absolute content in unit of foliage biomass. The element of excessive concentration is Mn, medium concentration is characteristic for Pb and Zn and low concentration is observed for Sb, Cr, As, Cu, Ni and Sn. Calculation of coefficient of biological accumulation of the metals under research has shown its high values for Crimean pine. The data presented for Black locust indicate low values of coefficient of biological accumulation, which is best noticeable for Chromium, Antimony and Tin. It is determined that a small amount of Sb and Sn are a subject to uptake by Black locust leaves, whilst for Crimean pine needles, Sb and As are characterised by the lowest inflow. The average content of lead is 209.11 kg·ha−1 for Crimean pine in all age groups of trees, whilst for Black locust, this index is only 15.52 kg·ha−1, which is 13.5 times less. Zinc accumulation is better performed by Black locust leaves, and it gradually decreases with increasing age. No definite trend of redistribution and subsequent accumulation of copper depending on tree species and age was found.

Evaluation of the impact of reducing national emissions of SO2 and metals in Poland on background pollution using a bioindication method

Changes in environmental pollution by S, Cd, Cu, Pb and Zn in 2006–2014 were evaluated using a bioindication method. This method was based on measurements of pollutants in Scots pine (Pinus sylvestris L.) needles. The measurements were performed in the Chojnowskie Forests, a region recognized as a background area for central Poland. The changes in the contents of sulfur (S) and metals in needles were not comparable with the changes in the global emissions of the pollutants in Poland. On average, the pollution level in the study area decreased by 9.9% for S, 61.4% for Pb, 22.5% for Cd, 11.7% for Zn and 10.4% for Cu. During the same period, global emissions in Poland decreased by 38.1% for S, 8.0% for Pb, 63.2% for Cd, 11.7% for Zn and 14.0% for Cu. Therefore, the differences in the changes in emissions and the needle contents of each element should be examined separately which was not a goal of this study. However, the discrepancy between these results did not prevent the use of bioindication methods. Evaluation of pollutant contents in plants reflected their incorporation in biological processes rather than air or soil pollution levels.

Long term growth of crop plants on experimental plots created among slag heaps

Suppression of plant growth is a common problem in post-mining reclaimed areas, as coarse texture of soils may increase nitrate leaching. Assessing feasibility of using solid waste (precipitated solid matter) produced by water and sewage treatment processes in field conditions is very important in mine soil reclamation. Our work investigated the possibility of plant growth in a degraded site covered with sewage-derived sludge material. A test area (21m × 18m) was established on a mine soil heap. Experimental plant species included Camelina sativa, Helianthus annuus, Festuca rubra, Miscanthus giganteus, Amaranthus cruentus, Brassica napus, Melilotus albus, Beta vulgaris, and Zea mays. ANOVA showed sufficient water content and acceptable physical properties of the soil in each year and layer in a multi-year period, indicating that these species were suitable for phytoremediation purposes. Results of trace elements assays indicated low degree of contamination caused by Carbocrash waste material and low potential ecological risk for all plant species. Detrended correspondence analysis revealed that total porosity and capillary porosity were the most important variables for the biosolids among all water content related properties. Overall, crop plants were found useful on heavily degraded land and the soil benefited from their presence. An addition of Carbocrash substrate to mine soil improved the initial stage of soil reclamation and accelerated plant growth. The use of this substrate in phytoremediation helped to balance the content of nutrients, promoted plant growth, and increased plant tolerance to salinity. Sewage sludge-amended biosolids may be applied directly to agricultural soil, not only in experimental conditions.

Vegetation development and nutrients supply of trees in habitats with high sulfur concentration in reclaimed former sulfur mines Jeziórko (Southern Poland)

The paper presents an assessment of vegetation (composition and cover-abundance), nutrient supply, and especially sulfur accumulation in the trees foliage (birch and pine) used in reforestation and wood small-reed (Calamagrostis epigejos (L.) Roth) appearing in succession on reclaimed areas of the former Jeziórko sulfur mine (southern Poland, Tarnobrzeg region). In researched area, three categories of vegetation cover were determined: category D-degraded and unsuccessfully reforested plots, and two categories with successful reforestation: P-pine and B-birch stands. On each category, four study plots (4-6 areas each, depends on site category) were established. Soil and vegetation samplings (current year and 2-year-old pine needles, birch leaves, and wood small-reed foliage) were collected on the subplots established in regular grid square (10 × 10 m) in each category. Basic soil properties and nutrient content in soils and vegetation were analyzed. Trees grew well in areas where neutralization and reclamation treatments were carried out properly and showed a good supply of nutrients (exception of phosphorus and nitrogen), while on category D, only herbaceous vegetation with low cover-abundance and dominated by wood small-reed were noted. Linear correlations between the soil and trees nutrients content occurred, while the correlations between the soil and wood small-reed did not occur. Wood small-reed did not display increased sulfur uptake which may indicate a strategy of blocking pollutant uptake from the soil and may be recommended as a species resistant to sulfurous soils.

Causal inference between bioavailability of heavy metals and environmental factors in a large-scale region

The causation between bioavailability of heavy metals and environmental factors are generally obtained from field experiments at local scales at present, and lack sufficient evidence from large scales. However, inferring causation between bioavailability of heavy metals and environmental factors across large-scale regions is challenging. Because the conventional correlation-based approaches used for causation assessments across large-scale regions, at the expense of actual causation, can result in spurious insights. In this study, a general approach framework, Intervention calculus when the directed acyclic graph (DAG) is absent (IDA) combined with the backdoor criterion (BC), was introduced to identify causation between the bioavailability of heavy metals and the potential environmental factors across large-scale regions. We take the Pearl River Delta (PRD) in China as a case study. The causal structures and effects were identified based on the concentrations of heavy metals (Zn, As, Cu, Hg, Pb, Cr, Ni and Cd) in soil (0-20 cm depth) and vegetable (lettuce) and 40 environmental factors (soil properties, extractable heavy metals and weathering indices) in 94 samples across the PRD. Results show that the bioavailability of heavy metals (Cd, Zn, Cr, Ni and As) was causally influenced by soil properties and soil weathering factors, whereas no causal factor impacted the bioavailability of Cu, Hg and Pb. No latent factor was found between the bioavailability of heavy metals and environmental factors. The causation between the bioavailability of heavy metals and environmental factors at field experiments is consistent with that on a large scale. The IDA combined with the BC provides a powerful tool to identify causation between the bioavailability of heavy metals and environmental factors across large-scale regions. Causal inference in a large system with the dynamic changes has great implications for system-based risk management.

Accumulative response of Scots pine (Pinus sylvestris L.) and silver birch (Betula pendula Roth) to heavy metals enhanced by Pb-Zn ore mining and processing plants: Explicitly spatial considerations of ordinary kriging based on a GIS approach

Plants have an accumulative response to heavy metals present in soils or deposited from airborne sources of emissions. Therefore, their tissues are very often used in studies of heavy metal contamination originating from different sources as a bioindicator of environmental pollution. This research was undertaken to examine accumulation capacities of Pb, Zn, Cd, Cu and Cr in washed and unwashed needles of Scots pine (Pinus sylvestris L.) and leaves of silver birch (Betula pendula Roth) growing in a contaminated area. We collected needles of Scots pine and leaves of silver birch in an area around a sedimentation pond and metallurgic plant processing Pb and Zn ores near Olkusz, Poland. Concentrations of heavy metals, which have been linked with exposure to emissions, were determined from foliar samples collected at 33 sites. These sites were established at various distances (0.5-3.6 km) from the pond and metallurgic plant so as to identify the predominant accumulative response of plants. Spatial gradients for Pb and Zn were calculated using an ordinary kriging interpolation algorithm. A spatial pattern was identified by a GIS method to visualize maps over the Pb-Zn ore mining area. The accumulation of Zn (R² = 0.74, p < 0.05) and Pb (R² = 0.85, p < 0.01) in plant tissues correlated with soil concentrations. This tendency was not found in the case of Cu, Cd and Cr.

Assessment of Heavy Metals Contamination in Reclaimed Mine Soil and their Accumulation and Distribution in Eucalyptus Hybrid

The metal contamination in reclaimed mine soil (RMS) of Jharia coal field, Dhanbad (India) using various contamination indices and their accumulation in tissues of Eucalyptus hybrid were assessed. In RMS, metal concentrations were found higher (202%-533%) than control soil (CS) with major contribution of Co and Mn followed by Zn, Cu and Pb. Principal component analysis (PCA) of metals present in RMS was carried out to assess their origin in RMS. The contamination factor (CF) values in RMS indicated moderate to very high level of pollution (ranged between 2.02 and 5.33). Higher accumulation of Pb in barks (three times), Zn in leaves (4.5 times), Mn in leaves (19 times), and Cu in roots (1.4 times) was found in trees growing on RMS than CS. The study concluded that different tree tissues accumulate varied concentration of heavy metals in RMS and thus for biomonitoring of metals, specific tissues has to be selected.

Trace element contamination differentiates the natural population of Scots pine: evidence from DNA microsatellites and needle morphology

The Scots pine is often used in the biomonitoring of forests. Studies on the chemical composition plus variability of its needles morphological structure allow for an assessment of the state of environmental pollution. However, in their natural populations, the response of individual trees to stress differs. This study reports on the influence of long-term soil contamination with trace elements on the morphology of the needles, its possible relation to the differentiation of the genetic pool, and their implications for biomonitoring. In the natural and self-renewable pine stand growing near the point polluter (zinc smelter, Upper Silesia, Poland), two categories of trees are observed with respect to their health status: pollution-tolerant (T) and pollution-sensitive (S). A detailed analysis of the trace element content of the needles reveals that the concentration of Cd, Zn, Pb, and Cu in the needles is significantly higher in S as compared to T individuals. The metal accumulation pattern decidedly follows the sequence Pb > Cd > Cu > Zn. An analysis of the fluctuating asymmetry (FA) of the needles reveals that sensitive trees showed an FA index ten times higher in comparison to tolerant ones. Moreover, the high differences between these S and T tree groups are also observed in the basic genetic diversity parameters investigated by an analysis of DNA simple sequence repeats (SSR). The concentration of trace elements in pine needles, distinct in sensitive and tolerant trees and in connection with their morphological and genetic characteristics, may reflect an adaptation process. The level of Mg and Fe content in the needles could be a physiological-toxicological index for evaluating trace element "lethality" expressed as Mg and Fe mineral-survival strategies. The example of differences described in this Scots pine population should be taken into consideration in ecotoxicological research to better interpret the obtained results.

Effects of copper deficiency and copper toxicity on organogenesis and some physiological and biochemical responses of Scots pine (Pinus sylvestris L.) seedlings grown in hydroculture

The morphological, physiological, and biochemical parameters of 6-week-old seedlings of Scots pine (Pinus sylvestris L.) were studied under deficiency (1.2 nM) and chronic exposure to copper (0.32, 1, 2.5, 5, and 10 μM CuSO4) in hydroculture. The deposit of copper in the seed allowed the seedlings to develop under copper deficiency without visible disruption of growth. The high sensitivity of Scots pine to the toxic effects of copper was shown, which manifested as a significant inhibition of growth and development. The loss of dominance of the main root and a strong inhibition of lateral root development pointed to a lack of adaptive reorganization of the root system architecture under copper excess. A preferential accumulation of copper in the root and a minor translocation in aerial organs confirmed that Scots pine belongs to a group of plants that exclude copper. Selective impairment in the absorption of manganese was discovered, under both deficiency and excess of copper in the nutrient solution, which was independent of the degree of development of the root system. Following 10 μM CuSO4 exposure, the absorption of manganese and iron from the nutrient solution was completely suppressed, and the development of seedlings was secured by the stock of these micronutrients in the seed. The absence of signs of oxidative stress in the seedling organs was shown under deficiency and excess of copper, as evidenced by the steady content of malondialdehyde and 4-hydroxyalkenals. Against this background, no changes in total superoxide dismutase activity in the organs of seedlings were revealed, and the increased content of low-molecular-weight antioxidants was observed in the roots under 1 μM and in the needles under 5 μM CuSO4 exposures.

Cadmium availability in rice paddy fields from a mining area: The effects of soil properties highlighting iron fractions and pH value

Cadmium (Cd) availability can be significantly affected by soil properties. The effect of pH value on Cd availability has been confirmed. Paddy soils in South China generally contain high contents of iron (Fe). Thus, it is hypothesized that Fe fractions, in addition to pH value, may play an important role in the Cd bioavailability in paddy soil and this requires further investigation. In this study, 73 paired soil and rice plant samples were collected from paddy fields those were contaminated by acid mine drainage containing Cd. The contents of Fe in the amorphous and DCB-extractable Fe oxides were significantly and negatively correlated with the Cd content in rice grain or straw (excluding DCB-extractable Fe vs Cd in straw). In addition, the concentration of HCl-extractable Fe(II) derived from Fe(III) reduction was positively correlated with the Cd content in rice grain or straw. These results suggest that soil Fe redox could affect the availability of Cd in rice plant. Contribution assessment of soil properties to Cd accumulation in rice grain based on random forest (RF) and stochastic gradient boosting (SGB) showed that pH value should be the most important factor and the content of Fe in the amorphous Fe oxides should be the second most important factor in affecting Cd content in rice grain. Overall, compared with the studies from temperate regions, such as Europe and northern China, Fe oxide exhibited its unique role in the bioavailability of Cd in the reddish paddy soil from our study area. The exploration of practical remediation strategies for Cd from the perspective of Fe oxide may be promising.

Phytoextraction of metals by Erigeron canadensis L. from fly ash landfill of power plant "Kolubara"

The objectives of this study were to determine the concentrations of Pb, Cd, As, Cr, Cu, Co, Ni, Zn, Ba, Fe, Al and Ag in Erigeron canadensis L. growing on fly ash landfill of power plant "Kolubara", Serbia. The content of each element was determined in every part of plant separately (root, stalk and inflorescence) and correlated with the content of elements in each phase of sequential extraction of fly ash. In order to ambiguously select the factors that are able to decidedly characterize the particular part of plant, principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) were performed. The bioconcentration factors and translocation factors for each metal were calculated in order to determine the feasibility of the use of plant E. canadensis L. for phytoremediation purpose. There were strong positive correlations between metals in every part of plant samples, and metals from pseudo total form of sequential extraction indicate that the bioavailability of elements in fly ash is similarly correlated with total form. Retained Al, Fe, Cr and Co in the root indicate its suitability for phytostabilization. This plant takes up Cd and Zn from the soil (bioconcentration factors (BCFs) greater than 1), transporting them through the stalk into the inflorescence (translocation factors (TFs) higher than 1). Regarding its dominance in vegetation cover and abundance, E. canadensis L. can be considered adequate for phytoextraction of Cd and Zn from coal ash landfills at Kolubara.

Recrystallization and stability of Zn and Pb minerals on their migration to groundwater in soils affected by Acid Mine Drainage under CO2 rich atmospheric waters

The extent of vertical contamination is intimately related to the soil solution and surface chemistry of the soil matrix with reference to the metal and waste matrix in question. The present research demonstrated the impact that the dissolved CO2 of the meteoric waters, which acidify the environment with pH values below 4, has in the increase of the metal mobility. Although under the given conditions the Zn remains mainly dissolved, the initial PbS and ZnS have evolved into newly formed secondary carbonates and sulphates (i.e., hydrozincite, gunningite, hydrocerussite) that can be found in the efflorescences. The chemical simulation done on the weathering of the original sulphide ores for the formation of these secondary minerals has proved the transient storage mainly of Pb. Nonetheless, many of the minerals formed inside the galleries will be easily dissolved in the next rains and release in an ionic form to the groundwater. The analytical procedure exposed has been proved to be useful not only for the characterization of AMD but also for the prediction of the mobility of metals.