Effects of liming on uptake of lead and cadmium by Raphanus sativa

Although liming soil to reduce the heavy metal uptake by plants has been recommended generally, there is some disagreement with the practice based on the results of recent studies. Radishes, Raphanus sativa L. var. Paekyong, were grown in greenhouse pots which were filled with soils treated with 1.52 mg kg^–1 Cd and 25.37 mg kg^–1 Pb, respectively and amended with lime at five rates of 0, 0.25, 0.5, 1.0, and 2.0% by dry soil weight. Plants were harvested three times at 25, 50, and 75 days after sowing and the roots and shoots separated. After the plant samples were digested with HNO₃-HClO₄, Cd was analyzed by flame AAS and Pb by graphite furnace AAS. A large amount of Cd was translocated into the radishes, which accumulated dramatically with time. Compared to Cd, Pb uptake was very low and accumulated slowly. Cd contents were very much higher in the shoots than the roots, but Pb was not significantly different. Liming or increased soil pH decreased Cd uptake markedly with increased lime level; Pb influence was negligible. Yields were decreased with excessive liming, but not by the levels of Cd or Pb added.     

An Assessment of Heavy Metal Contamination in Vegetables Grown in Wastewater-Irrigated Areas of Titagarh,West Bengal,India

The effects of municipal wastewater irrigation on the accumulation of heavy metals (Pb, Zn, Cd, Cr, Cu and Ni) in soil and vegetables were investigated by monitoring wastewater-irrigated agricultural field of Titagarh, 24-Parganas (North), West Bengal, India. The mean concentrations of Pb, Ni, Cu in the irrigation water and the mean Cd content in soil were much above the recommended level. The concentrations of Pb, Zn, Cd, Cr and Ni in all the examined vegetables were beyond the safe limits. The study reveals that heavy metal-contaminated vegetables grown in wastewater-irrigated areas may pose public health hazards.     

Effects of Different Soil Amendments on Mixed Heavy Metals Contamination in Vetiver Grass

Three different types of low cost soil amendments, namely, EDTA, elemental S and N-fertilizer, were investigated with Vetiver grass, Vetiveria zizanioides (Linn.) Nash growing under highly mixed Cd–Pb contamination conditions. A significant increase (p?<?0.05) in Cd and Pb accumulation were recorded in the shoots of all EDTA and N-fertilizer assisted treatments. The accumulation of Cd in 25 mmol EDTA/kg soil and 300 mmol N/kg soil showed relatively higher translocation factor (1.72 and 2.15) and percentage metal efficacy (63.25?% and 68.22?%), respectively, compared to other treatments. However, it was observed that the increased application of elemental S may inhibit the availability of Pb translocation from soil-to-root and root-to-shoot. The study suggests that viable application of 25 mmol EDTA/kg, 300 mmol N/kg and 20 mmol S/kg soil have the potential to be used for soil amendment with Vetiver grass growing under contaminated mixed Cd–Pb soil conditions.     

Arbuscular Mycorrhizal Fungi Favor the Initial Growth of <Emphasis Type="Italic">Acacia mangium,Sorghum bicolor</Emphasis>, and <Emphasis Type="Italic">Urochloa brizantha</Emphasis> in Soil Contaminated with Zn,Cu, Pb,and Cd

This study evaluated the effect of inoculation with a mixture of spores of arbuscular mycorrhizal fungi (AMF) (Glomus macrocarpum, Paraglomus occultum, and Glomus sp.) on the initial establishment of Acacia mangium, Sorghum bicolor, and Urochloa brizantha in soil contaminated with heavy metals. The experiment was conducted in a greenhouse, in plastic pots containing 1.8 kg of soil, which presented 7200, 1140, 480, and 72 mg of Zn, Cu, Pb, and Cd, respectively. The chlorophyll content (SPAD index) of inoculated plants of A. mangium and U. brizantha was higher than those of non-inoculated plants (p?<?0.05). No differences were detected for the concentration of heavy metals in plant shoots, whether the plant was inoculated or not. However, inoculated plants had greater root length (S. bicolor and U. brizantha) (p?<?0.05) and greater plant height (A. mangium) (p?<?0.05). The present results demonstrate that the beneficial effects of AMF on plant growth and the alleviation of contaminants are imperative factors for the rehabilitation of soils contaminated with heavy metals.     

The Effect of Heavy Metal Concentration and Soil pH on the Abundance of Selected Microbial Groups Within ArcelorMittal Poland Steelworks in Cracow

The present study aimed to identify the effect of heavy metal concentration and soil pH on the abundance of the selected soil microorganisms within ArcelorMittal Poland steelworks, Cracow. The analysis included 20 soil samples, where the concentration of Fe, Zn, Cd, Pb, Ni, Cu, Mn, Cr and soil pH were evaluated together with the number of mesophilic bacteria, fungi, Actinomycetes and Azotobacter spp. In the majority of samples soil pH was alkaline. The limits of heavy metals exceeded in eight samples and in one sample, the concentration of Zn exceeded 31-fold. Chromium was the element which most significantly limited the number of bacteria and Actinomycetes.     

Biotests and biosensors in ecotoxicological risk assessment of field soils polluted with zinc, lead, and cadmium

The combined chemical and ecotoxicological hazard evaluation study was conducted on 60 smelter-influenced soils containing 1 to 13, 50 to 653, and 100 to 1,198 mg/kg of Cd, Pb, and Zn, respectively. For these soils (liquid-to-soil ratio = 10), water extractability of Zn, Cd, and Pb was less than 0.19% (median values). Acetic acid (0.11 M) extracted 23, 9.7, and 0.7% of Cd, Zn, and Pb, respectively. Although heavy metal concentrations in the studied soils were high, the toxic effects of water extracts were observed only in few samples and in few biotests (algae Selenastrum capricornutum and metal detector assay). For most of the aquatic test organisms (e.g., crustaceans, photobacteria), the bioavailable concentrations of metals in soil-water extracts were either subtoxic, or the adverse effects were compensated by soil nutrients, etc. However, analysis of the soils with recombinant Cd sensor Bacillus subtilis (pTOO24) showed that about 65% of these apparently subtoxic samples contained bioavailable Cd when analyzed in the suspension assay (detection limit 1.5 mg Cd/kg soil), indicating the desorption of Cd induced by direct contact of bacteria with soil particles. The median bioavailable fraction of Cd (1%) was 23-fold lower than the fraction extracted by acetic acid. The Pb-Cd sensor Staphylococcus aureus (pT0024) detected bioavailable Pb only in the suspensions of five of the most lead-polluted soils (>417 mg Pb/kg): the median bioavailability of Pb was 0.42%. Consequently, the hazard assessment relying on total metal levels in soils should be revised by critical comparison with data obtained from bioassays. Development and use of biosensors (excellent tools for mechanistic studies and signaling hazard already at subtoxic level) should be encouraged.     

Background Concentrations of Heavy Metals in Benthos from Transboundary Rivers of the Transbaikalia Region, Russia

The concentrations (mg/kg dry weight) of Cu, Zn, As, Cd, Hg, and Pb were measured in benthic macroalgae and invertebrates collected in the upper transboundary tributaries of the Onon River, Transbaikalia, Russia. The background concentration ranges in Cladophora fracta, Ulothrix zonata and Zygnemataceae were: 6.4–9.1 for Cu, 27.2–73.1 for Zn, 0.4–0.9 for Cd, 6.7–35.3 for As, 0.01–0.02 for Hg, and 1.9–4.3 for Pb. In Brachycentrus americanus and Lymnaea media the concentration ranges were: 9.0–25.5 for Cu, 21.4–96.0 for Zn, 0.1–0.3 for Cd, 1.7–5.6 for As, 0.004–0.02 for Hg, and 0.4–2.2 for Pb. The concentrations of Cu, Zn, Pb, and Hg were consistent with data for uncontaminated areas. Under contamination conditions the concentrations in C. fracta were: 938 for Zn, 513 for Pb, and 9.5 for Cd; in Lymnaea media were: 46.8 for Cu, 176 for Zn, 52.3 for Pb, and 3.0 for Cd. All the organisms showed a common response to contamination, and consequently can be used as biomonitors of contamination by heavy metals.     

Ecotoxicity of Cr, Cd, and Pb on Two Mediterranean Soils

Three potentially toxic elements [chromium (Cr), lead (Pb), and cadmium (Cd)] were tested to assess their effects on two soils of different properties and origin. The soils were a granitic soil (Haplic Arenosol), which meets the requirements of OECD ecotoxicity testing, and a calcareous soil (Calcaric Regosol) with properties often found in the Mediterranean areas. The metal concentrations used ranged from 0.001 to 5,000 mg kg^?1 soil. The effects on soil microbial activity and community composition (respirometry and polymerase chain reaction–denaturing gradient gel electrophoresis analysis), as well as the effects on plant germination and elongation (Lactuca sativa), were assessed. The toxicity of the soil water extracts was also evaluated by the growth inhibition of algal populations (Pseudokirschneriella subcapitata). Cr showed the highest level of toxicity to soil organisms in the assays performed because this element remains in soil as anionic form and is less retained by the soil solid matrix than Cd and Pb. The lowest observed–adverse effect level for Cr ranged from approximately 0.1 mg kg^?1 [substrate induced respiration (SIR) test for the granitic soil] to 10 mg kg^?1 (basal respiration and SIR tests for the calcareous soil). For Pb (SIR) and Cd (SIR and alga tests), these levels were approximately 100 mg kg^?1. Germination and algal tests showed higher sensitivity in Regosol soil than in Arenosol soil for Cr due to differences in the bioavailability between the soils. In the cases or areas where alkaline soils are abundant, these should also be considered in laboratory ecotoxicity testing to avoid underestimation of ecotoxicological risks.     

Cadmium and Lead Accumulation in Three Endogeic Earthworm Species

The objective of this study was to assess the capability of earthworms from the same ecological group as heavy metal bioindicators. Three earthworm species from the endogeic group were studied: Aporrectodea caliginosa (Savigny, 1826), Perelia kaznakovi (Michaelsen, 1910) and Octolasion lacteum (Örley, 1885). Their accumulation of the heavy metals lead (Pb) and cadmium (Cd) were studied from three stations in Tehran province, Iran. O. lacteum was used to compare metal accumulations in two sites located next to a highway. A. caliginosa and P. kaznakovi were used at a third site located near the edge of a sewage system to compare metal accumulations between the two endogeic species in this area. At both locations, the concentrations of Cd and Pb in earthworms were higher than in the surrounding soil. The results of the study revealed that P. kaznakovi and A. caliginosa were better bioindicators for Pb, but O. lacteum was a better bioindicator for Cd. These earthworms can therefore be used as Cd and Pb bioindicators in environmental assessment.     

Effect of Cd or Pb Addition to Cu-Contaminated Soil on Tissue Cu Accumulation in the Earthworm,Dendrobaena veneta

Generally, soil heavy metal contamination consists of a mixture of heavy metals. Soil chemical properties and interaction with other pollutants in soil affect the external heavy metal bioavailability. Moreover, interaction with other pollutants accumulated in organisms may change the toxicity of each pollutant. Therefore, the hypotheses was tested that addition of Cd or Pb to Cu-contaminated soil would lead to an increase in tissue Cu accumulation in the earthworm,Dendrobaena veneta,caused by (i) induction of metallothionein by Cd, or (ii) an increase in Cu concentration in soil solution due to the exchange of adsorbed Cu for Pb. Tissue heavy metal concentrations were determined after exposure in contaminated soils for 3 or 21 days. Considerable amounts of Cu, Cd, and Pb were accumulated, indicating that these heavy metals were available for uptake byD. veneta.Both Cd and Pb, however, did not significantly affect tissue Cu accumulation.     

Comparative Effects of Biochar,Slag and Ferrous–Mn Ore on Lead and Cadmium Immobilization in Soil

A variety of remediation approaches have been applied to the heavy metals-contaminated soils, however, the immobilization of metals in co-contaminated soils still not cleared. Therefore, an incubation study was conducted to evaluate the instantaneous effects of different concentrations of biochar (BC), slag (SL) and Fe–Mn ore (FMO) on immobilization of Pb and Cd through the Toxicity Characteristic Leaching Procedure (TCLP) by following the the European Community Bureau of Reference (BCR), CaCl₂ and NH₄NO₃. The sequential extraction of BCR showed decrease in acid soluble fractions, while the residual proportions of Pb and Cd were enhanced with increasing concentrations of SL and BC. Addition of BC significantly lowered the extractable fractions of both metals by TCLP, NH₄NO₃ and CaCl₂ as compared to SL and FMO. Among all amendments, BC incorporation into co-contaminated soil offered promising results for Pb and Cd immobilization. Overall, all amendments showed positive and long-term impact on the reclamation of co-contaminated soil with heavy metals and could deserve advance monitoring studies on a field scale.     

Toxicity and bioaccumulation of lead and cadmium in marine protozoan communities

The behavior of lead and cadmium in a protozoan community was studied in order to obtain new data regarding the toxicity and bioaccumulation of these heavy metals. For this purpose, microcosms with different concentrations of the pollutants (without metals, 500 microg Cd and Pb x L(-1) 1,000 microg Cd and Pb x L(-1)) were used. Protozoans bioaccumulated 7.03-207.00 microg Pb x g(-1) dry weight (dw) and 0.05-332.75 microg Cd x g(-1) dw, representing an accumulation capacity of up to 161.45 microg Pb x g(-1) dw and 310.75 microg Cd x g(-1) dw more than that of the bacteria. The addition of both metals caused a significant reduction in the density of protozoans. These data were compared with those obtained previously in treatments that used these metals separately.     

Human health risk assessment of lead,cadmium, and mercury co-exposure from agricultural soils in the Tuzla Canton (Bosnia and Herzegovina)

The aim of this study was to assess the risk of human exposure to lead (Pb), cadmium (Cd), and mercury (Hg) through agricultural soil by considering both uncertainty and variability in key exposure parameters. For this reason we collected soil samples from 29 locations in the Tuzla Canton (Bosnia and Herzegovina) and measured their metal levels with inductively coupled plasma atomic emission or absorption spectrometry (ICP-AES and ICP-AAS, respectively). The levels of Pb ranged from 13.33 to 1692.33 mg/kg, of Cd from 0.05 to 3.67 mg/kg, and of Hg from 0.02 to 2.73 mg/kg. To estimate cancer and non-cancer risks we used deterministic and semi-probabilistic methods. Lead was found to involve higher health risk than the other two heavy metals. Its hazard index (HI) decreased between population groups (children>women>men) and exposure routes (ingestion>skin contact>inhalation). Our Monte Carlo simulations indicated that Pb HIs for both adult populations had a 0.6 % probability to exceed the threshold value of 1, while in children this probability was 14.2 %. Cd and Hg showed no probability to exceed the threshold in any scenario. Our simulation results raise concern about possible adverse health effects of heavy metals from soil, especially in children. It is very important to continue monitoring environmental pollution and assess human health risk, not only with respect to soil, but also with other important environmental compartments, such as air and water.KEY WORDS: cancer risk, deterministic methodology, heavy metals, Monte Carlo simulations, non-cancer risk, probabilistic methodology     

Bacteria and cadmium interactions in natural and laboratory model aquatic systems

Cadmium-resistant bacterial populations were examined in sediments of the Ottawa River, near Lima, Ohio, at a site that had elevated levels of Cd, Cr, Cu, Ni, Zn, and Fe. The percentage of the bacterial population that was resistant to cadmium was higher at the metal-contaminated site than at a less contaminated site downstream.Bacillus was the most abundant genus of the total river sediment population recovered andPseudomonas was the most abundant Cd-resistant genus recovered. Types and distribution of bacterial populations in 40 liter laboratory model aquatic systems were examined over a ten-week period during the continuous addition of 10 mg Cd⁺² per day. The Cd level in the water column rose rapidly through the first two weeks and reached a maximum of 3 g Cd/ ml. Sediment Cd levels rose most rapidly after 5 weeks and reached a concentration of 270 g Cd/g after 10 weeks. The bacteria in the water column responded to the Cd treatment with increased Cd resistance more quickly and to a greater degree than the bacteria in the sediment. The types of Cd-resistant bacteria isolated in the model systems were similar to Cd-resistant bacteria isolated from sediments of the Ottawa River.     

Evaluation of different phosphate amendments on availability of metals in contaminated soil

A pot trial was conducted to assess the efficiency of P-induced metal immobilization in soils. Natural hydroxyapatite (HA), phosphate rock (PR), triple-superphosphate (TSP), and diammonium phosphate (DAP) were evaluated for their ability to reduce cadmium (Cd), lead (Pb), and zinc (Zn) bioavailability in an artificially metal-contaminated soil with three addition levels: T0 (without metals added), T1 (Cd/Pb/Zn:0.6/100/66 mgkg(-1)), and T2 (Cd/Pb/Zn: 1.5/300/200 mgkg(-1)). Phosphate compounds were applied at 2500 mg P(2)O(5) kg(-1) soil for each metal level with five treatments: CK (control), TSP, DAP, PR, and HA, respectively. The immobilization and bioavailability of Cd, Pb, and Zn were determined by plant (Brassica campestris L.) uptake, scanning electron microscope (SEM), and sequential extraction. The results showed that HA was superior to all other materials for reducing Pb, Zn, and Cd uptake in shoot with reductions of 34.6-53.3% for Pb, 31.2-47.3% for Zn, and 39.1-42.4% for Cd, respectively, as compared with the control treatment. The mechanisms of Pb immobilization in the soil and the decreased Pb translocation from the plant root to shoot induced by added phosphate were identified with scanning electron microscope (SEM) equipped with energy dispersive X-ray elemental spectrometry (EDS). Sequential extraction results indicated that the phosphate amendments converted significant amounts of the soil Pb, Zn, and Cd from exchangeable (EX), organic bound (OC), carbonate bound (CB), amorphous Fe and Al oxides-bound (OX) (non-residual (RES) fractions) to RES fraction. In general, the effect of different phosphates on plant uptake of Pb, Zn, and Cd followed the order: HA>PR>DAP>TSP. The results suggested that HA and PR amendments could significantly reduce the bioavailability and increase the geochemical stability of soil Pb, Zn, and Cd in contaminated soils.     

Availability of Heavy Metals (Cd, Pb, and Cr) in Agriculture from Commercial Fertilizers

The purpose of this study was to investigate the availability of the heavy metals cadmium (Cd), lead (Pb), and chromium (Cr) to soil and maize plants fertilized with different sources and doses of zinc (Zn) in a Rhodic Eutrudox soil. For that purpose, concentrations of Cd, Pb, and Cr were evaluated in leaf tissue and grains of maize plants and in 0–20 and 20–40 cm soil layers after fertilization with four doses of Zn from eight different sources of fertilizer. There was no accumulation of Cd, Pb, and Cr in maize grain and Cd and Cr in leaf tissue of the plants; nevertheless, there was accumulation of Pb in leaf tissue, showing its availability throughout different sources of Zn and consequent uptake by plants. Regarding the soil, it was observed that fertilizer from the different sources made Cd, Pb, and Cr available at increasing amounts proportional to increased Zn doses. Under experimental conditions, fertilization with Zn increased concentrations of heavy metals Cd, Pb and Cr in soil, further highlighting the importance of conducting more studies related to the application of mineral fertilizers for micronutrient supply and the availability of heavy metals.     

公路旁土壤中重金属污染分布及潜在生态危害的研究

[目的]研究公路旁土壤中重金属污染的分布及潜在生态危害。[方法]以319国道龙岩市新罗区路段为研究区,对耕作土采样,用原子吸收光谱法和分光光度法分析土壤中重金属Cd、Pb、Cu、Zn和Cr含量,并与对照区比较,同时采用Lars Hakanson指数法评价重金属的潜在生态危害。[结果]研究区表层土壤cd[(1.48±0.60)mg/kg]、Pb[(160.17±55.99)mg/kg]、cu[(38.44±12.16)mg/kg]、Zn[(80.35±6.60)mg/kg]、Cr[(79.50±23.58)mg/kg]含量显著高于对照区(P<0.001),Cd和Pb为重度污染(100％),Cu和Cr为轻微污染(分别占监测点位的55.8％和35.3％);土壤对重金属元素的吸收及污染程度:Pb>Cd>Cu>Cr>zn。潜在生态危害综合指数为253.0,主要污染为Cd,达到很强的生态危害,其次是Pb、Cu、Cr和Zn,均为轻微生态危害;潜在生态危害地带自公路起向其两侧扩散范围约为150 m。[结论]公路旁土壤中重金属以Cd、Pb污染为主,属于中等生态危害,污染物主要来源于机动车辆燃料和轮胎中所含微量重金属成分。     

Nutritional Quality and Safety Related to Trace Element Content in Fish from Tyrrhenian Sea

This study analyzed for the detection of the following trace elements: As, Cd, Cu, Hg, Pb, Se, Zn, in muscle of four widely traded and consumed marine fish species (Mullus surmuletus L., Merluccius merluccius L., Micromesistius poutassou (Risso, 1827), Scomber scombrus L.) selected for their wide trade and consumption. Mean concentrations found in fish muscle, irrespective of species, ranged from 3.61 to 105.49 (As); 0.01–0.08 (Cd); 0.74–4.71 (Cu); 0.09–1.10 (Hg); 0.02–0.58 (Pb); 0.30–2.88 (Se); 11.56–73.37 (Zn) mg/kg wet weight. As, Hg, Cu and Se concentrations showed a significant difference (p < 0.01) among the analyzed species in winter and in summer. Cd exhibited a significant difference (p < 0.01) only in summer. The maximum levels set for Hg, Cd and Pb by European Regulation No 1881/2006 were exceeded by 5 (8.9 %), 1 (1.8 %) and 4 (7.1 %) samples, respectively. In particular the species exceeding the legal limits were red mullet for Cd and Pb, Atlantic mackerel and blue whiting for Hg and Pb.     

Effects of Soil Amendments on the Extractability and Speciation of Cadmium,Lead, and Copper in a Contaminated Soil

The effects of chemical amendments including zeolite, compost and mesoporous molecular sieves (MCM-41) on the extractability and speciation of heavy metals (Cd, Pb and Cu) in a contaminated soil were investigated. Results showed that the application of soil amendments decreased Cd, Pb and Cu uptake by the shoots of pakchoi, up to 44.2–53.2%, 30.2–42.7% and 16.9–22.1%, respectively, compared with the control. Among the three amendments, zeolite and MCM-41 were more efficient in reducing Cd and Cu uptake, while compost was more efficient in reducing Pb uptake by the plants. The growth of pakchoi was improved in amended soils due to the action of chemical amendments.     

Metabolic Responses to Lead of Metallicolous and Nonmetallicolous Populations of Armeria maritima

Metabolic responses to Pb(NO₃)₂ (Pb) ions of excised leaves of metallicolous (MPs) and nonmetallicolous populations (NMPs) of Armeria maritima, cultivated on normal soil, were examined. Detached leaves were exposure to Pb for 24 h, and metabolic parameters were investigated. Pb decreased the photosynthesis (Pn) rate and photosystem II (PSII) activity, whereas the photochemical efficiency of PSII remained unchanged. In both populations, Pb ions caused increase in O₂ uptake of dark-treated leaves; however, respiration after Pn was not affected. Pb increased superoxide dismutase activity in MP leaves and malondialdehyde content in NMP leaves. Other metabolites after Pb treatment were increased (proline or H₂O₂) or decreased (malate). Ascorbate peroxidase activity and adenosine triphosphate content decreased more in MP than in NMP leaves. Our results indicate that A. maritima is well adapted to heavy metal-contaminated soils, and we discuss potential causes of the stimulation of respiration by Pb ions and possible reasons for the tolerance to oxidative stress of plants growing in a metal-rich habitat.