Chemical Fractionation Of Heavy Metals Research Articles

Chemical fractionation of heavy metals and zinc isotope source identification in sediments of the Huangpu River, Shanghai, China

BackgroundThe Huangpu River serves as a vital water source for around 24 million individuals residing in the metropolitan area of Shanghai. Despite this, elevated levels of heavy metals persist in the sediments of the river, with their chemical fractionation and sources remaining inadequately understood.ResultsTo improve the management of heavy metal contamination, sequential extractions and zinc (Zn) isotopic compositions were utilized to evaluate pollution levels in the Huangpu River. The findings reveal that the majority of heavy metals in the river sediments are present in residual fractions, constituting an average of 67.5% for Cd, 57.6% for Cu, 60.6% for Ni, 56.2% for Pb, and 74.4% for Cr, with the exception of Zn (33.8%). Furthermore, a substantial portion of Zn, exceeding 66%, was found in acid-exchangeable, reducible, and oxidizable fractions, indicating a high potential for Zn release into aquatic ecosystems.ConclusionFurther analysis of Zn isotopes pinpointed traffic emissions, including exhaust fumes and tire wear particles (account for ~ 34.0%), along with anthropogenic emissions and fertilizer (~ 31.7%), as the major culprits behind this contamination. These findings highlight the critical need for stricter regulations to control heavy metal contamination from traffic and domestic sources within the Huangpu River basin.

Insight into heavy metal chemical fractions in ash collected from municipal and industrial waste incinerators in northern Vietnam.

This investigation involved the collection of fly ash and bottom ash specimens from seven waste incinerators situated in the northern provinces of Vietnam, aimed at assessing the composition and distribution patterns of five chemical fractions of heavy metals (Pb, Cr, As, Cd Cu, and Zn) present in incinerator waste ash. The outcomes reveal that fly ash exhibited a relatively elevated concentration of industrial waste metals (25-66%) such as As, Cd, and Pb primarily in exchangeable (F1) and carbonate fractions (F2), which are mobile forms susceptible to environmental dissolution and consequential bioaccumulation posing health risks to humans. The predominant states of the metals Cr, Cu, and Zn were identified as residual, Fe-Mn oxide, and carbonate, respectively, with their relative proportions showing minimal variation. Conversely, heavy metals were predominantly present in residual residue and Fe-Mn bound form (F3) in bottom ash derived from both residential and commercial waste incineration operations. The non-carcinogenic hazard indices (HI) associated with the examined metals, ranked for both adults and children, were as follows: Pb > Cr > As > Cd > Cu > Zn. Notably, the HI values for Pb, Cr, and As exceeded the permissible threshold (HI > 1) for children. However, the risk of As, Cd, and Pb-related cancer via exposure pathways remained within acceptable limits for both age groups. Conversely, the probability of carcinogenic effects attributable to Cr surpassed the permissible threshold (>10-4), indicating significant health concerns associated with heavy metals in waste incinerators for humans, particularly children.

The impacts of aging pH and time of acid mine drainage solutions on Fe mineralogy and chemical fractions of heavy metals in the sediments

Fe (oxyhydr)oxides are the main components that accumulate heavy metals (HMs) in the acid mine drainage (AMD) sediments, but how the aging pH and time of AMD solution affects the Fe mineralogy and HMs speciation remains ambiguous. Herein, we determined the impacts of aging pH and time on the Fe mineralogy and chemical fractions of HMs in the sediments from Dabaoshan mining area using mineral characterizations, chemical extraction, and AMD solution incubation. For the natural AMD sediments, jarosite and goethite are the major Fe (oxyhydr)oxides in sample S1 with solution pH 2.68, while schwertmannite is dominant in sample S2 with solution pH 6.78, co-existing minor ferrihydrite. With increasing the AMD solution pH, the total contents of HMs (expect for As) and the reducible fraction of HMs (expect for Pb) in the sediments both increase. The HMs of Mn, Zn, Ni, and Cd are mainly associated with Fe (oxyhydr)oxides, while Pb possibly exists as Pb-bearing minerals (e.g., PbSO4) in the sediments. The oxidizable fraction of all HMs is negligible in both sediments. When the AMD solution of S1 was aged at different pHs, schwertmannite is dominant initially at all pHs, with a higher crystallinity being at a lower pH. With increasing aging time, the pre-formed schwertmannite transforms to goethite and jarosite at pH≤3, while it keeps stable at pH 5 and 7 due to the accumulation of more HMs. These new insights are essential to assess the mobility and availability of HMs in the AMD-affected areas.

Comprehensive insight into heavy metal(loid)s in road dust from industrial and urban areas in northern Vietnam: concentrations, fractionation characteristics, and risk assessment

ABSTRACT Road dust samples were collected from 6 cities and provinces in northern Vietnam to evaluate contamination levels and distribution characteristics of 5 toxic elements, including Cu, Zn, Pb, Cd, and As. Total concentrations of 5 elements in road dust samples ranged from 18.4 to 470 (median 96.4) mg/kg, in declining order of Zn > Cu > Pb > As > Cd. Pollution levels in urban road dust from Hanoi (median 266; range 205–366 mg/kg) were generally higher than those measured in samples taken from other industrial areas (median 91.1; range 18.4–470 mg/kg). Our results showed that the emission of some heavy metals from urban areas with high population density and heavy traffic was comparable to or even higher than in manufacturing areas of electronic components, construction materials, and mining. The chemical fractions of heavy metals in road dust were also evaluated. More than 60% of heavy metals are present in the potential mobile phases, indicating that the anthropogenic metals are still in a relatively weakly bound form. These metals can be mobile and bioaccumulative, affecting ecosystems and humans. The geological accumulation indexes indicate moderate contamination of heavy metals in many locations of this study. Cd poses an ecological threat in several urban and industrial sites. There were no serious human health risks associated with heavy metals in road dust. However, relatively high levels of Cu and Pb in road dust imply a health risk for children living in some urban and industrial areas. Further monitoring and risk assessment studies on toxic elements in road dust should be conducted, especially in developing countries’ highly urbanised and industrialised areas.

An Experimental Investigation of the Environmental Risk of a Metallurgical Waste Deposit

The aim of this study is to investigate the environmental risk of long-term metallurgical waste disposal. The investigated site was used for the open storage of lead and zinc waste materials originating from a lead smelter and refinery. Even after remediation was performed, the soil in the close vicinity of the metallurgical waste deposit was heavily loaded with heavy metals and arsenic. The pollutants were bound in various compounds in the form of sulfides, oxides, and chlorides, as well as complex minerals, impacting the pH values of the investigated soil, such that they varied between 2.8 for sample 6 and 7.34 for sample 8. In order to assess the environmental risk, some eight soil samples were analyzed by determining the total metal concentration by acid digestion and chemical fractionation of heavy metals using the BCR sequential extraction method. Inductively coupled plasma optical emission spectrometry (ICP-OES) was used to determine six elements (As, Cd, Cu, Pb, Zn, and Ni). Total concentrations of the elements in the tested soil samples were in the range of 3870.4–52,306.18 mg/kg for As, 2.19–49.84 mg/kg for Cd, 268.03–986.66 mg/kg for Cu, 7.34–114.67 mg/kg for Ni, 1223.13–30,339.74 mg/kg for Pb, and 58.21–8212.99 mg/kg for Zn. The ratio between the mean concentrations of the tested metals was determined in this order: As > Pb > Zn > Cu > Ni > Cd. The BCR results showed that Pb (50.7%), Zn (49.2%), and Cd (34.7%) had the highest concentrations in mobile fractions in the soil compared to the other metals. The contamination factor was very high for Pb (0.09–33.54), As (0.004–195.8), and Zn (0.14–16.06). According to the calculated index of potential environmental risk, it was confirmed that the mobility of Pb and As have a great impact on the environment.

Occurrence and Ecological Risk Assessment of Heavy Metals from Wuliangsuhai Lake, Yellow River Basin, China

As one of the eight largest freshwater lakes in China, Wuliangsuhai Lake is an extremely rare large lake with biodiversity and environmental protection functions in one of the world’s arid or semi-arid areas and it plays a pivotal role in protecting the ecological security of the Yellow River Basin. Heavy metals in sediment interstitial water, surface sediments, and sediment cores of Wuliangsuhai Lake were investigated and analyzed, and the pollution degree evaluated based on multiple assessment methods. The bioavailability of heavy metals of the surface sediments was evaluated by calculating the ratio of chemical fractions of heavy metals. The toxicity assessment of sediment interstitial water indicated that Ni, Zn, As, and Cd would not be toxic to aquatic ecosystems, however, Hg and Cr in some regions may cause acute toxicity to the benthos. The ecological assessment results of the surface sediments indicated that some areas of the lake are heavily polluted and the main polluting elements are Cd and Hg. Cd has the highest bioavailability because of its high exchangeable fraction ratio. In addition, exogenous pollution accumulated within 20 cm of the sediment cores, and then, with the increasing of the depth, the pollution degree and ecological risk decreased.

Combination of UNMIX, PMF model and Pb-Zn-Cu isotopic compositions for quantitative source apportionment of heavy metals in suburban agricultural soils

Quantitative identification of heavy metals (HM) sources in soils is key to prevention and control of heavy metal pollution. In this study, UNMIX, PMF (Positive matrix factorization) model and Pb-Zn-Cu isotopic compositions were combined to quantitatively identify heavy metal sources in a suburban agricultural area of Kaifeng, China. Using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) and ICP-MS, we measured Pb, Zn and Cu stable isotopic compositions, HM concentrations and HM chemical fractions in studied soils, as well as potential sources around the highly polluted site, including total suspended particle, compound fertilizer, irrigated river water and sediments. The results showed that total contents and chemical fractions of heavy metals, as well as Pb-Zn-Cu isotopic compositions presented great variation in different sites, which implied that heavy metal accumulation was obviously affected by local anthropogenic pollution source. UNMIX and PMF presented good agreement on source apportionment that industrial and agricultural activities (61.74% and 60.75% for UNMIX and PMF, respectively) were the major contributors to heavy metal accumulation in the study area. Especially, sewage irrigation and atmosphere deposition accounted for a large proportion (28.14% and 41.03% for UNMIX and PMF, respectively). Moreover, isotopic compositions of Pb, Zn and Cu in highly polluted soils and environment media gave further confirmation that sewage irrigation and atmosphere deposition were primary anthropogenic source. Therefore, combination of UNMIX, PMF model and Pb-Zn-Cu isotopic compositions showed good coordination in quantitative and specific source identification of heavy metals in agricultural soils.

Vertical Distribution and Chemical Fractionation of Heavy Metals in Dated Sediment Cores from the Saronikos Gulf, Greece

The Saronikos Gulf is under a lot of anthropogenic pressure, such as the urban expansion of the metropolitan area of Athens, the port of Piraeus and marinas, industrial activities, and tourism. Heavy metal pollution has been a major environmental problem in the area for many decades. Sedimentary cores have proven to be an invaluable indicator of heavy metal pollution, as they can reveal not only the current metal inputs but also the evolution of pollution over time, and with the appropriate geochemical analyses, they can provide information on the potential toxicity of metals. In this study, the temporal evolution and the chemical speciation of eleven elements were examined in sediment cores from Elefsis Bay and the Inner Saronikos Gulf, with an emphasis on the emerging environmental hazards (V and Ag). The results showed extensive pollution of the sediments by Ni, Cr, Cu, Zn, As, Mo, Cd, and Pb from the 1910s and 1960s in Eastern and Western Elefsis Bay, respectively. A significant decrease of the sediment enrichment in V, Ni, Cr, Cu, Zn, As, Cd, Pb, and Ag since 2000 was observed in the part of the Inner Saronikos Gulf that is mainly influenced by the WWTP of Athens. However, a toxicity assessment using the metal contents of the surface sediments showed that most of the trace elements studied still pose a moderate to high risk of toxicity to benthic ecosystems. The present study highlighted the urgent need for focused research and the management of trace element inputs, particularly Ag in the Inner Saronikos Gulf, where severe sediment modification was evident.

Correlation between chemical fractionation of heavy metals and their toxicity in the contaminated soils

Correlation between chemical fractionation of heavy metals and their toxicity in the contaminated soils

Distribution and partitioning of heavy metals in water and sediments of a typical estuary (Modaomen, South China): The effect of water density stratification associated with salinity

Many estuaries have undergone severe saltwater intrusion in addition to simultaneously experiencing serious heavy metal pollution. To explore the effect of water density stratification associated with saltwater intrusion on the behaviour of heavy metals (Cr, Co, Ni, Cu, Zn, As, Pb, and Cd) in water and sediments, a field survey was conducted in a typical estuary (Modaomen). The content, distribution, and mobility of heavy metals were investigated, as well as the influence of environmental factors on their future. The results showed that Modaomen estuary was characterised by a notable variation in salinity along the estuary, presenting total freshwater upstream, high salinity stratification water in the mouth, and saltwater offshore. Dissolved metals presented a prominent gradient vertically, with 1.2–2.1 times higher in bottom water than in surface water and the highest contents in the highly–stratified bottom water. Elevated salinity and restricted mixing induced by water stratification were likely the causes of this outcome. The distribution of heavy metals in sediments was greatly governed by grain size, Fe/Mn (hydr)oxides, total organic carbon, salinity, and dissolved oxygen. Comprehensive evaluation, combined with total contents and chemical fractions of heavy metals, indicated that internal release from sediments contributed a considerable part to the higher levels of heavy metals in bottom water, particularly for Zn and Pb, which was fully consistent with their status in water body, and elevated salinity and lack of oxygen were likely the primary driving factors. During the phase-partition processes between bottom water and sediments, partitioning coefficients were markedly lower in the highly stratified zone, implying that saltwater intrusion facilitated the mobility and repartitioning processes of metals. Because of increased levels and toxicity of heavy metals in water and extended residence time during saltwater intrusion, the potential damage to the estuarine ecosystem should receive more attention.

Assessment of heavy metals pollution in sediment of Citarum River, Indonesia

Heavy metals have been reported to accumulate in sediment of Citarum River. The measurement of total heavy metals may not be able to provide information about the exact dimension of pollution, thus the determination of different fractions assumed great importance. This study was performed to determine chemical fractions of heavy metals (Cu, Ni, Cr, Pb and Cd) in sediment collected at 8 locations from Citarum River. The sequential extraction procedure was used to extract heavy metals in water-soluble, acid-soluble, MnO occluded, organically bound, FeO occluded and residual fraction in sediment. Bioavailability and potential ecological risk level of heavy metals were evaluated based on bioavailability factor (BF) and risk assessment code (RAC) method. The results showed that Cu, Ni, Cr were mostly in residual form, indicate those from geological sources. Cu had low bioavailability and no risk in all sediment samples of Citarum River. Ni and Cr each was found to have risk at 2 locations. Pb and Cd were found dominantly in non-residual fraction, suggest those from anthropogenic sources. BF and RAC analysis of Pb and Cd suggest that there is a potential risk to the aquatic environment.

CHEMICAL FRACTIONS OF HEAVY METALS IN SEDIMENTS OF LAKES ON SAMOYLOV ISLAND, THE LENA DELTA

The article focuses on studying the total content and chemical fractions of heavy metals (Fe, Mn, Co, Cr, Cu, Ni, Pb, V, Zn) in sediments of two lakes on Samoylov Island in the Lena delta. The lakes differ in genesis and hydrological conditions. Geochemical data for the study area were summarized. We used the sequential extraction procedure to research the roles of different sediment components in the accumulation of microelements. ICP AES was the method for all the chemical analyses. The results reveal a quite homogeneous vertical distribution of heavy metals in cores from the two lakes over the entire period of their existence (ca. 3 Ka according to radiocarbon dating). The average concentrations of the heavy metals were comparable to their content in sediments from other lakes, as well in the island soils. Analysis of the chemical fractions of the heavy metals showed that the elements were mainly stored in stable forms (bound to the crystal lattice of minerals). However, humic matter plays a significant role in binding the cations of all the metals to stable complex compounds. Cu, Pb and Zn had the most organophilic properties in the two lakes. It was noted that a significant proportion of Ni, Cr, Zn and Cu was bonded with Fe and Mn oxides. Cr, Cu, Zn and Mn were found in potentially bioavailable forms. The most mobile elements were Mn and Zn. There is a high risk of secondary water pollution with these metals.

Contrasting effects of biochar and hydrothermally treated coal gangue on leachability, bioavailability, speciation and accumulation of heavy metals by rapeseed in copper mine tailings.

The purpose of this research was to examine the influence of hydrothermally treated coal gangue (HTCG) with and without biochar (BC) on the leaching, bioavailability, and redistribution of chemical fractions of heavy metals (HMs) in copper mine tailing (Cu-MT). An increase in pH, water holding capacity (WHC) and soil organic carbon (SOC) were observed due to the addition of BC in combination with raw coal gangue (RCG) and HTCG. A high Cu and other HMs concentration in pore water (PW) and amended Cu-MT were reduced by the combination of BC with RCG and/or HTCG, whereas individual application of RCG slightly increased the Cu, Cd, and Zn leaching and bioavailability, compared to the unamended Cu-MT. Sequential extractions results showed a reduction in the exchangeable fraction of Cu, Cd, Pb, and Zn and elevation in the residual fraction following the addition of BC-2% and BC-HTCG. However, individual application of RCG slightly increased the Cu, Cd, and Zn exchangeable fractions assessed by chemical extraction method. Rapeseed was grown for the following 45 days during which physiological parameters, metal uptake transfer rate (TR), bioconcentration factor (BCF), and translocation factor (TF) were measured after harvesting. In the case of plant biomass, no significant difference between applied amendments was observed for the fresh biomass (FBM) and dry biomass (DBM) of shoots and roots of rapeseed. However, BC-2% and BC-HTCG presented the lowest HMs uptake, TR, BCF (BCFroot and BCFshoot), and TF for Cu, Cd, Cr, Ni, Pb, and Zn in rapeseed among the other amendments compared to the unamended Cu-MT. Overall, these findings are indicative that using biochar in combination with RCG and/or HTCG led to a larger reduction in HMs leaching and bioavailability, due to their higher sorption capacity and could be a suitable remediation strategy for heavy metals in a Cu-MT.

Chemical fractionation, bioavailability, and health risks of heavy metals in fine particulate matter at a site in the Indo-Gangetic Plain, India.

In the present study, the distribution and chemical fractionation of heavy metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) in PM2.5 collected at Sikandarpur in Agra from September 2015 to February 2016 were carried out to evaluate their mobility potential, environmental, and human health risk through inhalation. Sequential extraction procedure was applied to partition the heavy metals into four fractions (soluble and exchangeable fraction (F1); carbonates, oxides, and reducible fraction (F2); bound to organic matter, oxidizable, and sulphidic fraction (F3); and residual fraction (F4)) in PM2.5 samples. The metals in each fraction were analyzed by inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Daily PM2.5 concentration ranged between 13 and 238μgm-3 during the study period. For more than 92% of the days, the mass concentrations were greater than the National Ambient Air Quality Standard (NAAQS) set at 60μgm-3. The total mass concentration of the eight metals was 3.3μgm-3 that accounted for 2.5% of the PM2.5 mass concentration and followed the order Fe > Zn > Cu > Mn > Pb > Ni > Cd > Cr in dominance. The carcinogenic metals (Cd, Cr, Ni, and Pb) comprised 10% of the total metal determined. Almost all the metals had the highest proportion in the residual fraction (F4) except Ni, which had the highest proportion in the reducible fraction (F2). Chemical fractionation and contamination factor (CF) showed that Pb and Ni are readily mobilized and more bioavailable. Risk assessment code (RAC) showed that Cd, Cu, Mn, Ni, Pb, and Zn had medium environmental risk, while Cr and Fe had low risk. When the bioavailable (F1 + F2) concentrations were applied to calculate non-carcinogenic and carcinogenic risk, the results showed that the value of hazard index (HI) for toxic metals was 1.7 for both children and adults through inhalation. The integrated carcinogenic risk was 1.8 × 10-6 for children and 7.3 × 10-6 for adults, with both values being higher than the precautionary criterion (1 × 10-6). Enrichment factor (EF) calculations showed that Cd, Pb, Zn, and Ni were enriched being contributed by anthropogenic activities carried out in the industrial sectors of the city.

Changes in chemical fractions and ecological risk prediction of heavy metals in estuarine sediments of Chunfeng Lake estuary, China

The changes of available forms of heavy metals would affect their corresponding ecological risks in sediments. The distribution of chemical fractions of heavy metals in sediment profiles from Chunfeng Lake estuary was investigated and then a prediction model for potential ecological risk index (PMRI) was proposed to forecast the changes of ecological risks caused by the aging process of metals in sediments. The results show that the estuarine sediments were polluted by As and Cd. The proportions of available metals were generally decreased with depth, while those of the residual forms showed an opposite trend. The aging rates of Cd and As were found to be 0.21 and 0.12%/year, respectively. The PMRI model showed that the total ecological risk of metals in sediments decreased from moderate to low risk level (<150) after 25 years, while cadmium would need 47 years in contrast to the 15 years for As.

Chemical fractionation of heavy metals in fine particulate matter and their health risk assessment through inhalation exposure pathway.

Samples of PM2.5 were collected from an urban area close to a national highway in Agra, India and sequentially extracted into four different fractions: water soluble (F1), reducible (F2), oxidizable (F3) and residual fraction (F4) for chemical fractionation of arsenic (As), cadmium (Cd), cobalt (Co), chromium (Cr), nickel (Ni) and lead (Pb). The metals were analyzed by inductively coupled plasma optical emission spectroscopy in each fraction. The average mass concentration of PM2.5 was 93 ± 24μgm-3.The total concentrations of Cr, Pb, Ni, Co, As and Cd in fine particle were 192 ± 54, 128 ± 25, 108 ± 34, 36 ± 6, 35 ± 5 and 8 ± 2ngm-3, respectively. Results indicated that Cd and Co had the most bioavailability indexes. Risk Assessment Code and contamination factors were calculated to assess the environmental risk. The present study evaluated the potential Pb hazard to young children using the Integrated Exposure Uptake Biokinetic Model. From the model, the probability density of PbB (blood lead level) revealed that at the prevailing atmospheric concentration, 0.302 children are expected to have PbB concentrations exceeding 10μg dL-1 and an estimated IQ (intelligence quotient) loss of 1.8 points. The predicted blood Pb levels belong to Group 3 (PbB < 5μg dL-1). Based on the bioavailable fractions, carcinogenic and non-carcinogenic risks via inhalation exposure were assessed for infants, toddlers, children, males and females. The hazard index for potential toxic metals was 2.50, which was higher than the safe limit (1). However, the combined carcinogenic risk for infants, toddlers, children, males and females was marginally higher than the precautionary criterion (10-6).

Fractionation of heavy metals in yellow latosol cultivated with vegetables

Sequential extraction or chemical fractionation of heavy metals allows inferences to be made about their origin, occurrence, bioavailability, toxic potential and environmental contamination. Thus, the present study aimed to assess the distribution of Cu, Mn, Ni, Pb and Zn among the different soil fractions and landscape compartments of a yellow latosol cultivated with vegetables. Soil samples were collected from five areas cultivated with tomato (Lycopersicon esculentum, Mill.), lettuce (Lactuca sativa), chili pepper (Capsicum annuum L.) and chard (Beta vulgaris L.) in different slope positions (upper, middle, lower), and four reference areas (native forest), at a depth of 0.00 - 0.20 m. Heavy metal levels were also assessed in water used to irrigate the crops and for human consumption by collecting 200 ml of water samples from reservoirs. The soil samples were sequentially fractionated to quantify the concentrations of adsorbed Cu, Mn, Ni, Pb and Zn in the exchangeable (EF), organic matter (OF), amorphous and crystalline iron oxide fractions (AFeOx and CFeOx). Landscape position only interfered significantly in heavy metal adsorption in the soil for Cu and Ni associated with CFeOx and Zn bound to the EF in the farming areas. The highest Cu, Ni, Pb and Zn levels were found in the fractions with less stable chemical bonds (bound to organic matter), in addition to a strong affinity between Cu, Zn and Mn and the oxide fractions (AFeOx + CFeOx). The low affinity of Pb and Ni for the AFeOx and CFeOx fractions indicates greater contamination potential for the water reservoirs. In the short term, organic matter is the main source of remediation for heavy metal contamination in soil, making it important to adopt conservation practices aimed at reducing OM losses.

Comparative study on effects of four energy plants growth on chemical fractions of heavy metals and activity of soil enzymes in copper mine tailings

ABSTRACTFour gramineous energy plants, Miscanthus sacchariflorus, M. floridulus, Phragmites australis, and Arundo donax were grown on copper tailings in the field for four years. Their phytoremediation potential was examined in terms of their effects on the fractions of heavy metals and soil enzyme activities. Results showed that plantation of these four gramineous plants has improved the proportion of organic material (OM)-binding fraction of heavy metals in copper tailings as a whole, and reduced the proportion of exchangeable and residual fractions. In particular, M. sacchariflorus growth improved significantly the proportion of the OM-binding fractions of Cu (1.73 times), Cd (1.71 times), Zn (1.18 times), and Pb (3.14 times) (P < 0.05) and reduced markedly the residual fractions of Cu (64.45%), Cd (82.38%), Zn (61.43%), and Pb (73.41%) (P < 0.05). Except for A. donax, the growth of other three energy plants improved the activity of phosphatase, urease and dehydrogenase in copper tailings to some extent. In particular, the activity of soil phosphatase and urease in planted tailings differed significantly from that of control (P < 0.05). The effect of M. sacchariflorus growth on soil enzyme was the highest, followed by P. australis, M. floridulus, and A. donax. The content of each heavy metal fraction in soil was correlated with soil enzyme activities, especially the content of OM-binding fraction, which correlated significantly with the activities of phosphatase, urease and dehydrogenase in soil. According to the effects of four gramineous plants growth on activity of soil enzymes and fractions of heavy metals, M. sacchariflorus had the optimal effects for phytoremediation. Therefore, M. sacchariflorus was a candidate plant with great potential for the revegetation of heavy metal tailings.

The effect of selected acidic or alkaline chemical agents amendment on leachability of selected heavy metals from sewage sludge

The aim of the study was to evaluate the effect of acidic (Fenton's reagent, peracetic acid) or alkaline (CaO) chemical agents amendment on chemical forms of Pb, Ni, and Cd in sewage sludge. The dose of Fenton's reagent was as follows: Fe2+=1g·L−1, Fe2+/H2O2=1:100; stabilisation lasted for 2h. The dose of CaO was equal to 1g CaO·gd.m.−1. The dose of CH3COOOH was 2.5g·L−1. Total concentration of all metals in the digested sewage sludge was higher than in the soil and it did not meet Polish law requirements. Acidic chemical stabilisation of sludge did not significantly decrease total metal content in the sludge. Amendment of CaO decreased the content of Pb, Cd, and Ni in the sludge. Chemical fractions of heavy metals were identified in the sludge (exchangeable, carbonate bound, iron oxides bound, organic and residual). The results indicate that stabilisation of the sludge with Fenton's reagent and peracetic acid increased the exchangeable fraction of Pb, Cd, and Ni compared to the digested sludge, but it did not increase shares of mobile forms of metals considered as a total of I-st and II-nd fraction. Amendment of CaO increased percent share of examined metals in residual fraction. Not-mobile fractions of examined metals overweight the mobile ones in all sludge samples regardless of the treatment method.

Chemical Fractionation of Heavy Metals in the Soil of Auto-Mechanic Workshops in Akure, Ondo State, Nigeria

Chemical Fractionation of Heavy Metals in the Soil of Auto-Mechanic Workshops in Akure, Ondo State, Nigeria