Large Amounts Of Heavy Metals Research Articles

Impact of artificial water and sediment discharge regulation in the Huanghe (Yellow River) on the transport of particulate heavy metals to the sea

Variations in the concentrations of major particulate heavy metals (PHMs) (Mn, Pb, Zn, V, Cr, and Ni) and fluxes into the sea during the water–sediment regulation scheme (WSRS) in the Huanghe (Yellow River) were examined based on observational and measured data during June and July of 2009. Two stages of variations in the concentrations of PHMs were observed in the WSRS with lower values in the early stage and higher values in the late stage. The early stage corresponded to a high water discharge with coarser sediment that was largely scored from the riverbed, and the late stage corresponded to a low water discharge with much finer sediment that was released from the Xiaolangdi reservoir. The significant increase in PHM concentrations by 2–4 fold from the early to the late stage largely resulted from a decrease in the suspended-sediment grain size and an increase in the quantity of anthropogenic pollutants caused by changes in the sediment sources from riverbed in the lower reaches to the Xiaolangdi reservoir during the WSRS. The concentrations of PHMs, particularly in the late stage of the WSRS, were approximately two times as high as those during the pre-WSRS period as the anthropogenic pollutants have been increasing in recent years. More than 57% of the annual quantity of PHMs was transported to the sea during the WSRS, and over 34% of that from the Xiaolangdi reservoir was delivered to the sea during the late stage of the WSRS over a period of approximately 4–5days. This large quantity of heavy metals, with a high proportion of labile components because of the increasing contribution of anthropogenic pollutants, emptied into the sea over a short period and may thus drastically alter the eco-environment in the river mouth and its adjacent seas.

Health risks from the exposure of children to As, Se, Pb and other heavy metals near the largest coking plant in China

Coking influences environmental quality and poses high risks to human health as large amounts of heavy metals and metalloids are emitted into the environment from coal during the coking process. Health risks depend heavily on multi-pathway and element-specific exposures, which have, unfortunately, been rarely studied. In this study, children's health risks and exposure levels to As, Se, and heavy metals (Pb, Cd, Cr, Ni, Co, Zn, Cu, Mn, V and Sb) in the water, soil, dust, air and locally produced food were studied based on field sampling and questionnaire-based surveys around the largest coking area in China. Human blood samples were collected and analyzed to indicate the exposure levels. The non-carcinogenic risks to children mainly resulted from Cr, Mn, Pb, As and Sb, the levels of which were 3 to 10 times higher than the acceptable levels (1.0×10−6). The carcinogenic risks to children were 30 to 200 times higher than the safe level (1.0×10−6–1.0×10−4), which could be attributed to Cr, As and Ni pollution. The estimated risks mainly came from the pathway involving the ingestion of locally produced food, accounting for more than 85% in total for most elements. For As, the food ingestion and air inhalation exposure pathways both contributed approximately 50%, respectively. The high risks in this study highlight the attention paid to the health of children who live in the vicinity of coking activities and the importance of site-specific multi-pathway health risk assessments and food safety to protect potentially exposed children.

Mycorrhizal fungi modify element distribution in gametophytes and sporophytes of a fern Pellaeaviridis from metaliferous soils

In the present study, the element distribution within mycothallic and nonmycothallic gametophytes and the early stages of sporophyte development of Pellaea viridis (Pteridaceae) were investigated. Gametophytes of this fern were collected from soil samples originating in the ultramafic area of the Agnes Mine near Barberton, South Africa. The gametophytes were grown on both the original soil and on a plant growth substratum obtained from the local botanical garden. Gametophytes and young sporophytes grown on substratum inoculated with Glomus tenue or non-inoculated were freeze-dried, and the distribution of elements was studied using micro-PIXE. The GeoPIXE II software package was used for quantitative elemental mapping complemented by data extracted from arbitrarily selected micro-areas. The obtained results suggest that although the fern itself avoids the uptake of large amounts of heavy metals, increased levels of Ni, Cr, Fe, Co and Ti were found in the part of the gametophyte that hosted the fungal endophyte. This finding suggests that the fungus might be active in the immobilisation of certain potentially toxic metals that are taken up from the soil by the plant, although other mechanisms cannot be excluded. For the first time, precise, quantitative measurements of the concentration of individual elements in the fern gametophytes and young sporophytes were obtained, along with their distribution within the plant parts.

Bioaccumulation of Heavy Metals by Submerged Macrophytes: Looking for Hyperaccumulators in Eutrophic Lakes

To directly select submerged macrophytes with high accumulation capability from the field, 24 eutrophic lakes along the middle and lower reaches of the Yangtze River were investigated in the study. These eutrophic lakes have large amounts of heavy metals in both water and sediments because of human activities. The results showed that Najas marina is a hyperaccumulator of As and Cd, Ceratophyllum demersum is a hyperaccumulator of Co, Cr, and Fe, and Vallisneria natans is a hyperaccumulator of Pb. Strong positive correlations were found between concentrations of heavy metals in tissues of submerged macrophytes, probably because of coaccumulation of heavy metals. However, for most heavy metals, no significant correlations were found between submerged macrophytes and their surrounding environments. In conclusion, N. marina, C. demersum, and V. natans are good candidate species for removing heavy metals from eutrophic lakes.

Application of Nanomaterials for the Removal of Pollutants from Effluent Streams

Rapid industrialization with the increase in the population leads to the water crisis. The number of industries using heavy metals such as copper, chromium, nickel, zinc, etc. in their process is also leaving behind the effluent containing a large amount of heavy metals which discharged directly to the water bodies. There are constraints set by the regulatory bodies of government on the industries to maintain an upper level discharge limit for each of the metal ion. There are various methods available for the removal of metal ions which are selected according to the requirement. Adsorption is one of the optimal solutions for the removal of metal ions from industrial effluent streams. It is helpful in reducing the operational cost and size of equipment along with the increase recovery of metal ions. Adsorption is a surface phenomenon so the foremost property required for a perfect adsorbent is the higher surface area. Nanoparticles are now being preferred to be used as an adsorbent due to their large surface area which is a very important characteristic for a desired adsorbent. Development of nanoparticles has been the subject of enormous interest since the past decade. They have incredible adsorption properties due to the presence of high-energy adsorption sites and they also have excellent binding energies or interaction potentials for physisorption than traditional adsorbents. This study summarized the use of nanomaterial for the removal of metal ions from wastewater streams. It also highlights the various types of nanomaterials, their fabrication method and characteristics. The mechanism of metal adsorption onto various nanomaterials is also described in this study.

English

  Heavy metals constitute a serious health risk because they accumulate in soils, water and organisms. One of the methods of removing these pollutants from water and soil is the use of plants. There are many plants (hyperaccumulators) which have the ability to accumulate large amounts of heavy metals. One of them is the aquatic fern Azolla filiculoides, which can bind some substances. A dried A. filiculoides biomass was used to remove heavy metal from aqueous solution using batch experiments. The aim of this study was to verify the ability of A. filiculoides to fix Ni and Cu from polluted waters. The maximum uptake capacities of the collected A. filiculoides from the Asbchin Wetland west of Mazandaran in the northern part of Iran at the optimal conditions for Ni and Cu ions were approximately 0.77 and 0.54 mmol/g (dry Azolla), respectively. Fourier transform infrared (FT-IR) spectroscopy was used to examine functional groups that may take part in the dried A. filiculoides biomass. Results showed that the amino, carboxyl and hydroxyl groups may be responsible for the biosorption of metal ions on the biomass. Desorption experiments indicated that ethylenediaminetetraacetic acid (EDTA), HNO3 and HCl were efficient desorbents for recovery from Ni (II) and Cu (II).   Key words: Azolla filiculoides, wastewater, batch biosorption, heavy metals

CADMIUM AND MANGANESE ACCUMULATION IN PHYTOLACCA AMERICANA L. AND THE ROLES OF NON-PROTEIN THIOLS AND ORGANIC ACIDS

Phytolacca americana L. can accumulate large amounts of heavy metals in its aerial tissues, especially cadmium (Cd) and manganese (Mn). It has great potential for use in phytoextraction of metals from multi-metal-contaminated soils. This study was conducted to further investigate the Cd- and Mn-tolerance strategies of this plant. Concentrations of non-protein thiols (NPTs) and phytochelatins (PCs) in leaves and roots increased significantly as the concentration of Cd in solution increased. The molar ratios of PCs:soluble Cd ranged from 1.8 to 3.6 in roots and 8.1 to 31.6 in leaves, suggesting that the cellular response involving PC synthesis was sufficient to complex Cd ions in the cytosol, especially that of leaves. In contrast, excess Mn treatments did not result in a significant increase in NPT or PC concentrations in leaves or roots. Oxalic acid concentrations in leaves of plants exposed to 2 or 20 mM Mn reached 69.4 to 89.3 mg (0.771 to 0.992 mmol) g–1 dry weight, respectively, which was approximately 3.7- to 8.6-fold higher than the Mn level in the 0.6 M HCl extract. Thus, oxalic acid may play an important role in the detoxification of Mn.

Study on the Characteristics of Heavy Metal Accumulation in Seven Dominant Plants in Shilu Iron Mines Area of Hainan

Based on the field investigation and sampling, seven dominant wild plants and relative soil samples in Hainan Shilu iron mines area were collected. To analyze and study the contents of heavy metals Pb, Cd, Cu, Fe, Mn and Zn in these samples and the characteristics of enriching heavy metals of these dominant plants. Results of this study showed that the contents of the same heavy metal in the soils around roots system of seven dominant plants had a large range of variation, to a certain extent, it reflected the difference of the enriched characteristics of different plants to the same heavy metal. All seven dominant plants had endurance and enriched characteristics to Fe. Bothriochloa root hoarded up abundant Fe, Cu, Zn and its stored characteristics to Mn, Pb, Cd also stood out from the seven dominant plants, so it could be used as good plant which absorbed a large amount of heavy metals but mainly held in the roots, this result had a good consistance with the finding that the enriched and transferred characteristics of Bothriochloa to heavy metals in soil. In the soil of low cadmium pollution, Calopo and Bothriochloa had higher concentration factors of cadmium, this indicated they had a good potential in high cadmium pollution soil. White tephrosia and Cyperus alternifolius had the higher metastasis ability to Mn, Zn, Cd, which had the potential of phytoremediation.

Efficiency of different particle sizes of dried Salvinia natans in the removing of Cu(II) and oil pollutions from water

Aquatic plants can be useful in removing various contaminants from contaminated waters, since they can sorb large amounts of heavy metals and oil spill. To investigate the effects of different particle sizes of biosorbent on the metal biosorption and oil spill capacities, dried biomass of Salvinia natans selected as aquatic plant which found a lot in astrakhan city. From the results we concluded that, the metal biosorption capacity increased with decreasing of particle size, while in the case oil spill, capacities of removing of spill increase with increasing particle sizes.

Removal of heavy metals in stormwater by hydrous ferric oxide

Stormwater runoff from urban and industrial areas contains several types of heavy metals that have negative ecological impacts on receiving waters, and therefore methods need to be developed to remove these pollutants. Combined removal of a mixture of heavy metal cations (Cu2+, Zn2+, Cd2+, and Ni2+) and an oxy anion (selenate, SeO4−) from an artificially prepared stormwater was investigated by sorption of these heavy metals on hydrous ferric oxide (HFO) in a column experiment under intermittent runoff (wetting and drying) condition, as occurs between rainfall events in the field. The heavy metal removal behaviour varied between ions as well as with time. In each continuous column run (8 h) the amount of ions removed progressively decreased with time and reached a constant level at approximately 4–6 h. However, stopping the runoff for 40 h and starting the next runoff after this period removed a large quantity of heavy metals in the first few hours of this run. The intermittent runoff for seven runs showed that HFO has a high capacity to remove copper and zinc, which were present in higher concentrations in the stormwater than cadmium, nickel and selenium.

The Heavy Metal Equilibrium in the Soil

.” Friedrich NietzcheThe presence of heavy metals in soils is an environmental hazard key and one of the most difficult contamination control problems to solve. There are two main causes: firstly, the chemical character of heavy metals (they are not subjected to biodegradation processes), favours accumulate in the environment and, secondly, the complexity of the geochemical soil matrix. Simplification of this matrix increase chances of recognition of basic soil processes [1]. Soil is a major reservoir for xenobiotic compounds as it possesses an ability to bind various chemicals [2]. The soil as an important ecological factor due to several characteristics: close correlation with the climate and region and its structure, configuration and nature; its own quality on which relies formation and protection of surface and underground matter resources; influence on humans nutrition and its role in social and economic development of mankind. The heavy metals have an important influence on plants, animals and humans development. The chemical compositions of these heavy metals don’t exceed 0.01% in the analyzed systems and their physiologic role is essential for normal biological life cycle of organisms [3]. They are absolutely necessary for living organisms but their biological role is still difficult to establish. If taken alone they don’t show deficiency symptom, only in combination with other mineral elements and don’t seem to have a direct function in plants nutrition. Soil has the ability to immobilise introduced chemicals like heavy metal ions [4,5]. From the geological and chemical point of view the heavy metals can express lots of proprieties. The solid phase of soils and environmental factors play an important role in heavy metals solubility, dynamics and balance in the soil.Between solid, liquid and gaseous phases exists a dynamic equilibrium in the soil.When the concentration of the elements in the soil solution exceeds the normal level, the mineral elements start to precipitate in order to maintain the normal balance. When their concentration is low they start to dissolve from the solid phase [6]. The period of time in which every element re-establish his own balance in the soil, depends on the soil nature, structure, texture, chemical composition pH, humus content etc. [7]. The heavy metal equilibrium in the soil can last from several hours to few days or years. The manganese and iron hydroxides represent the basic phase, where the heavy metals found in small quantities are adsorbed, co–precipitated and integrated in the soil.The organic matter in the soil can retain a large amount of heavy metals or can release some of them due to microbiological activities [8,9]. From these reasons we can discuss about a dynamic balance. The elements with metal characteristics, in their inferior oxidation states (one, two, three and in some cases even four states) can form combination with most of bases. For these the most abundant and important, due to their effects on plant development carbon, nitrogen and sulphurous compound and also carboxylic acids salts [10,11]. Metals can be found in the soil as native elements, characterized by a fine crystal structure with metal bond like Van der Walls hetero–polar bonds.The humus, humic acids and the natural chelate agents possess the capacity to make more complex heavy metals. A substantial part of the humic acids is represented by functionally carboxylic acids groups which give them the ability to incorporate positive charged ions (Zn

Hydrothermal sulfidation of zinc-containing neutralization sludge for zinc recovery and stabilization

The conventional lime-neutralization process generates a huge volume of neutralization sludge (NS). The disposal of NS is difficult because it contains large amounts of heavy metals, moisture and complex components. The present study describes the application of hydrothermal sulfidation (HS) toward the conversion of certain heavy metals (mainly zinc) in NS to metal sulfide (MeS) for subsequent metal recovery through flotation. The effects of temperature, time, sulfur concentration and liquid-to-solid ratios were investigated under laboratory conditions. The extent of zinc sulfidation was up to 85% under optimal conditions. Flotation tests indicated that the ZnS produced could be separated from the NS, increasing the recovered Zn concentration from 19.9% to 38.8%. The toxicity characteristic leaching procedure (TCLP) revealed that stabilization and detoxification of heavy metals occurred during sulfidation. The formation of metal sulfide by HS enhanced the stabilization effect. Moreover, flotation technology provided a means to enhance metal recovery from the NS.

First record of anisakid juveniles (Nematoda) in the European seabass Dicentrarchus labrax (family: Moronidae), and their role as bio-indicators of heavy metal pollution

This study assessed the anisakid nematode distribution pattern in the fish collected from coasts of Mediterranean Sea, Egypt, during the period September 2010-April 2011. Two hundred thirty out of 300 (76.7%) Dicentrarchus labrax (European seabass) marine fishes belonging to family Moronidae were dissected and found to be infected with larva three nematodes. The larvae had been studied by light and scanning electron microscopy. The present work represents the first record of the presence of the parasite in this fish in the Mediterranean Sea. The concentrations of some heavy metals (Pb, Zn, Fe, Cd, Cu, Mn, Ni) in parasites as well as in tissues of fish were measured. The presented results showed that the nematode parasites are able to accumulate heavy metals in their tissues and in some cases that they are able to accumulate large amounts of heavy metals in a higher amount than host tissues. This demonstrated their sustainability as bioindicators of environmental pollution by removing heavy metals and help in the survival of fish.

Assessing soil heavy metal pollution in the water-level-fluctuation zone of the Three Gorges Reservoir, China

The water-level-fluctuation zone (WLFZ) between the elevations of 145–175 m in China's Three Gorges Reservoir has experienced a novel hydrological regime with half a year (May–September) exposed in summer and another half (October–April) submerged in winter. In September 2008 (before submergence) and June 2009 (after submergence), soil samples were collected in 12 sites in the WLFZ and heavy metals (Hg, As, Cr, Cd, Pb, Cu, Zn, Fe, and Mn) were determined. Enrichment factor (EF), factor analysis (FA), and factor analysis-multiple linear regression (FA-MLR) were employed for heavy metal pollution assessment, source identification, and source apportionment, respectively. Results demonstrate spatial variability in heavy metals before and after submergence and elements of As, Cd, Pb, Cu, and Zn are higher in the upper and low reaches. FA and FA-MLR reveal that As and Cd are the primary pollutants before submergence, and over 45% of As originates from domestic sewage and 59% of Cd from industrial wastes. After submergence, the major contaminants are Hg, Cd, and Pb, and traffic exhaust contributes approximately 81% to Hg and industrial effluent accounts about 36% and 73% for Cd and Pb, respectively. Our results suggest that increased shipping and industrial wastes have deposited large amounts of heavy metals which have been accumulated in the WLFZ during submergence period.

INVESTIGATION INTO HEAVY METAL CONCENTRATION BY THE GRAVEL ROADSIDES / SUNKIŲJŲ METALŲ KONCENTRACIJŲ ŽVYRKELIŲ PAKELIŲ DIRVOŽEMIUOSE VERTINIMAS / ОЦЕНКА КОНЦЕНТР АЦИЙ ТЯЖЕЛЫХ МЕТАЛЛОВ В ПОЧВЕ ОБОЧИН ГРАВИЙНЫХ ДОРОГ

Vehicles release large amounts of heavy metals to the environment. There have been done a lot of investigations analysing the distribution of heavy metals in soils near intensive regional roads. However, there is lack of investigations into the impact of small-intensity gravel roads on roadside soil contamination with heavy metals. The object of this investigation is four gravel roads of local significance connecting small villages. The intensity of these roads is very low. The gravel roads are chosen according to application of dust-minimizing materials, for example, CaCl2 and oil emulsion. According to our results, none of the soil samples had an excess of heavy metal concentration limit. Besides, heavy metal concentrations were decreasing with a distance from the road increasing. We can make an assumption that road dust-minimizing materials do not have a significant impact on heavy metal distribution in roadside soils. The major factors of heavy metal pollution distribution in roadside soils are traffic intensity, roadside trenches, and topographic conditions. Santrauka Eksploatuojant autotransportą, į aplinką patenka daug sunkiųjų metalų. Atlikta nemažai tyrimų sunkiųjų metalų paplitimuidirvožemyje šalia intensyvių magistralinių kelių nustatyti, tačiau mažo intensyvumo keliai šiuo požiūriu tiriami mažai.Tirti pasirinkta 4 žvyrkeliai – vietinės reikšmvs keliai, jungiantys nedideles gyvenvietes. Eismo intensyvumas šiuose keliuose mažas. Žvyrkeliai pasirinkti pagal taikomas priemones dulkėtumui mažinti, t. y. du nagrinvjami žvyrkeliai apdorotiCaCl2, kiti du – naftos emulsija. Nė viename mėginyje sunkiųjų metalų koncentracijos neviršijo DLK, o tolstant nuo važiuojamosios kelio dalies sunkiųjų metalų koncentracijos buvo mažesnės. Galima daryti prielaidą, kad kelio apdorojimo medžiagos dulkėtumui mažinti žymios įtakos sunkiųjų metalų pasiskirstymui pakelių dirvožemyje nedaro, lemia transporto srauto intensyvumas, kelio grioviai pakelėse bei reljefo sąlygos. Резюме При эксплуатации автомобилей в окружающую среду попадает много тяжелых металлов. Проведено немалоисследований, посвященных анализу распространения тяжелых металлов в почве обочин интенсивно эксплуатируемых магистральных дорог, однако исследований, касающихся аналогичных проблем дорог малой интенсивности, в настоящее время имеется немного. В настоящей работе в качестве объекта исследований выбраны четыредороги местного значения с гравийным покрытием, соединяющие небольшие поселения. Интенсивность дорог небольшая. Гравийные дороги выбраны с учетом их обработки для уменьшения пыльности – две дороги обработаны с применением CaCl2, а две другие – с применением нефтяной эмульсии. Ни в одной пробе не былозафиксировано концентраций тяжелых металлов, превышающих допустимые нормами. С удалением от проезжей части концентрации тяжелых металлов уменьшались. На основании исследований можно сделать вывод о том,что материалы, применявшиеся для уменьшения пыльности дорог, большого влияния на распространениетяжелых металлов в почве обочин дорог не оказывают. На распространение тяжелых металлов в почве обочин оказывает влияние интенсивность транспортного потока, кюветы на обочинах и условия рельефа.

Flora of toxic depots in selected industrial zones

Floristic composition in three industrial areas with soils contaminated by heavy metals (As, Cd, Cu, Hg, Pb, Zn) and organic pollutants (polychlorinated biphenyls) was studied. The content of Pb was only significantly correlated with the floristic composition and explained 13.8% of its variability considering spatial dependency of the sites. No correlation was found for PCBs. Altogether, 237 plant vascular species were found at three study sites (117, 133 and 105, respectively). The three study areas differed in their species composition represented by their own characteristic species. The gradient in the content of natives/non-natives, species number, prevailing life forms and indicator values for plant species investigated was revealed. Based on our results, for phytoremediation purposes we can select productive plant species with high biomass and ability to accumulate large amounts of heavy metals or organic compounds and surviving on soils with low mineral content.

Effect of cadmium-contaminated soils on dry matter yield and mineral composition of raya (Brassica juncea) and spinach (Spinacia oleracea)

Raya (Brassica juncea) and spinach (Spinacia oleracea), grown as leafy vegetables, are known to accumulate large amounts of heavy metals in their shoots and roots because of their high biomass and root proliferation. In a pot experiment, a sandy loam soil was polluted with cadmium (Cd) at rates of 0, 5, 10, 20, 40 and 80 mg kg−1 soil to assess the accumulation pattern and its effect on the dry matter yield and mineral composition of these vegetables. There was a decrease in dry matter yield due to the phytotoxic effect of Cd. The rate of Cd application at which a significant decline in root and shoot dry matter yield occurred varied depending on the vegetable. It was 20 mg Cd kg−1 soil in the shoots for both crops. However, the roots of raya were found to be more tolerant of Cd toxicity than those of spinach, as is evident from the fact that a significant decline in dry matter yield occurred at 20 and 10 mg Cd kg−1 soil, respectively. Since no visual toxic symptoms were observed on the leaves of raya in any of the treatments, it is clear that the metal may accumulate in this vegetable without visual evidence of its presence. However, at application levels beyond 40 mg kg−1 soil, toxicity symptoms, in the form of interveinal chlorosis of the leaf lamina followed by necrosis and leaf rolling, were clearly evident in the case of spinach. The reduction in root and shoot growth corresponded with the amounts of extractable Cd in the soils. The total content of Cd in the crops increased gradually as the rate of applied Cd rose and the roots accumulated much higher amounts than the shoots. The relationship of Cd with Zn and Fe was synergistic in both roots and shoots at the lower rates, but antagonistic at higher Cd application rates for both the crops, while in the case of Mn and Cu, the relationship was negative and antagonistic.

OS ISÓPODOS TERRESTRES SÃO BOAS FERRAMENTAS PARA MONITORAR E RESTAURAR ÁREAS IMPACTADAS POR METAIS PESADOS NO BRASIL?

Restoration Ecology aims at the restoration of degraded environments and seeks an integrated management of its resources. It has been considered as a long-term solution, not only to reconstitute the original landscape, but also to give back functionality to these enviromnments. Using tools as phytoremediation, Restoration Ecology aims to decrease or eliminate the negative effects of contaminants in polluted areas. To be effective, restoration projects need both short-term and long-term biomonitoring, and for that matter the knowledge on bioindicator organisms is required. Terrestrial isopods are macroinvertebrate detritivores that can bioaccumulate large quantities of heavy metals. They have been long used as models in the terrestrial ecotoxicology and therefore have a great potential to be employed as biomonitors during the phytoremediation of polluted lands. In Brazil, knowledge on the species' biology, ecology and distribution is still very incipient, nonetheless it is possible to identify two species with potential to be used as biomonitors. Atlantoscia floridana (Philosciidae) and Balloniscus sellowii (Balloniscidae) are Neotropical species with large geographical distribution in Brazil and show an enhanced capacity to colonize degraded lands. In the future, with a better knowledge on these species' physiology, the combination of phytoremediation and terrestrial isopods as biomonitors may enhance the ecological restoration of lands contaminated by heavy metals.

Heavy metals stabilization in medical waste incinerator fly ash using alkaline assisted supercritical water technology

This study investigated the process of aluminosilicate formation in medical waste incinerator fly ash containing large amounts of heavy metals and treated with alkaline compounds at 375 degrees C and examined how this process affected the mobility and availability of the metals. As a consequence of the treatments, the amount of dissolved heavy metals, and thus their mobility, was greatly reduced, and the metal leaching concentration was below the legislative regulations for metal leachability. Moreover, this process did not produce a high concentration of heavy metals in the effluent. The addition of alkaline compounds such as sodium hydroxide and sodium carbonate can prevent certain heavy metal ions dissolving in water. In comparison with the alkaline-free condition, the extracted concentrations of As, Mn, Pb, Sr and Zn were decreased by about 51.08, 97.22, 58.33, 96.77 and 86.89% by the addition of sodium hydroxide and 66.18, 86.11, 58.33, 83.87 and 81.91% by the addition of sodium carbonate. A mechanism for how the formation of aluminosilicate occurred in supercritical water and affected the mobility and availability of the heavy metals is discussed. The reported results could be useful as basic knowledge for planning new technologies for the hydrothermal stabilization of heavy metals in fly ash.

Greenhouse gases emission from soil contaminated with automobile industry residue in Brazil

Solid waste of the automobile industry containing large amounts of heavy metals might affect the emission of greenhouse gases (GHG) when applied to the soil. Accumulation of inorganic chemical elements in the environment generally occurs due to human activity (industry, agriculture, mining and waste landfills). Residues from human activities may release heavy metals to the soil solution, causing toxicity to plants and other soil organisms. Heavy metals may also be adsorbed to clay minerals and/or complexed by the soil organic matter, becoming a potential source of pollutants. Not much is known about the behavior of solid wastes in tropical soil as regarded as source of greenhouse gases (GHG). The emission of GHG (CO2, CH4 and N2O) was evaluated in incubated soil samples collected in an area contaminated with a solid residue from an automobile industry. Samples were randomly collected at 0 to 0.2 m (a mix of soil and residue), 0.2 to 0.4 m (only residue) and 0.4 to 0.6 m (only soil). A contiguous uncontaminated area, cultivated with sugarcane, was also sampled following the same protocol. Canonical Discriminant Analysis and Principal Component Analysis were applied to the data to evaluate the GHG emission rates. Emission rates of GHG were greater in the samples from the contaminated than the sugarcane area, particularly high during the first days of incubation. CO2 emissions were greater in samples collected at the upper layer for both areas, while CH4 and N2O emissions were similar in all samples. The emission rates of CH4 were the most efficient variables to differentiate contaminated and uncontaminated areas.