Comparison of biological collectors of airborne heavy metals near ferrochrome and steel works

The value of several biological monitors of the distribution of airborne Cr and Ni dust was studied in the vicinity of ferrochrome and stainless steel works. The following indigenous biomonitors were compared: the forest mosses Pleurozium schreberi and Hylocomium splendens, the epiphytic lichen Hypogymnia physodes, bark of Scots pine (Pinus silvestris), needle litter, earthworms (Dendrobaena octaedra) and moths (mainly Xylena vetusta). Results were compared and related to the heavy metal deposition estimated by the vertical snow sampling method. The representative sampling size at different pollution levels was investigated. In Cr it varied from 1 to 300 mg m^?2 a^?1. Of the biomonitors studied, the mosses showed most effective accumulation of heavy metals, their results having a clear relationship to the deposition and good replicability. The lichen gave almost as good results as the mosses. Both mosses and lichens collected heavy metals more effectively at low to moderate pollution loads than near the pollution source. The accumulation of heavy metals in bark was lower than in the mosses or lichen. The heavy metal content of earthworms indicated the degree of pollution well, but the replicability of the method was poor. The accumulation of heavy metals in moths was low.     

Effect of heavy metals on microorganisms in soils near a secondary lead smelter

Soil samples were collected to a depth of 0 to 10 cm from several sites near a secondary Pb smelter during the summer of 1976 in order to determine heavy metal concentrations of soil and enumerate soil microorganisms and earthworms. Chemical analyses indicated that abnormally high concentrations of Pb, As, Cd, and Cu decreased with increasing distance from the source and population counts of bacteria, actinomyces, fungi, nematodes and earthworms increased with increasing distance from the smelter. The negative correlation coefficients between bacteria, actinomyces, fungi, and nematodes and the level of Pb, As, Cd, and Cu in the soil were statistically significant. The microflora of the contaminated soil was altered and the marked quantitative reduction or elimination of organisms were attributable to heavy metal pollution emission from the secondary Pb smelter.     

Mobility of heavy metals in polluted soils near zinc smelters

The distribution and the availability of Cd, Zn, Cu, and Pb along the entire profile of two highly polluted soils located near Zn smelters have been related to the chemical and mineralogical composition of the soil. Lead and Cu deposits always remain in the surface layers and their availability measured by neutral ammonium acetate extraction was very weak. The behavior of Cd and Zn appears different in sandy acidic podzolic soils and in neutral loamy soils. These metals are associated with the organic matter migration in podzolic soils, while they remain in the upper layers in loamy soils provided that the pH is higher than 6. When the pH drops below 6, the mobility of Cd increases while that of Zn increases only below pH 5. The availability of heavy metals is lower in neutral loamy soils than in sandy acidic soils due to precipitation of carbonates and phosphates. With increasing depth, Cd and Zn are more available if the soil is acid; but, if the soil is neutral and loamy the availability is kept low by adsorption on clays and free oxides. The results of the complex trace metals interactions with the soil components show a higher accumulation capacity for loamy soils than for sandy soils notwithstanding the fact that their CEC is similar.     

Phosphatic fertilizers as a source of heavy metals in protected cultivation

Abstract

In order to quantify the uptake by lettuce plants (Lactuca sativa L.) of heavy metals contained in the phosphate fertilizers and to evaluate their residual bioavailability in the growth substrate a greenhouse experiment was carried out. The superphosphate added to the soil contained varying amounts of heavy metals, particularly Cd, Cr and Zn which accumulated in the soil and increased the amounts available for plant uptake. The accumulation of metals observed in the plant tissues did not have physiological effects on lettuce and did not affect negatively the growth of the plants. The heavy metal speciation in soil indicated that metals extractable by EDTA increased by increasing the phosphorus added. These amounts of metals, adsorbed or complexed in the soil after harvest, represent in protected environments a potentially bioavailable species for the following cultivations.     

Distribution of airborne heavy metals as measured in the lichens Ramalina stenospora and Parmotrema praesorediosum in Baton Rouge,Louisiana

The lichens Ramalina stenospora and Parmotrema praesorediosum were collected from 30 stations in the greater metropolitan area of Baton Rouge, Louisiana and analyzed for Al, Cu, Fe, Zn, and Pb content. A univariate analysis of the data showed a significant difference between metal concentrations and sampling stations. When the stations were separated into two groups representing those in the industrial and urban zones, a discriminant analysis was over 90% successful in correctly assigning stations based solely on metal concentrations. No significant differences in metal concentration with species could be observed. Average metal concentrations for the two lichen species were used to construct contours and three-dimensional plots of metal distribution across the study area which clearly demonstrate the effects of the industrial zone on airborne metal levels.     

The effects of acid rainfall and heavy metal particulates on a boreal Forest ecosystem near the sudbury smelting region of Canada

Sulphur dioxide and particulate pollution have been occurring over a wide area in the Sudbury region, Ontario, as a result of massive smelting operations. In excess of 3Z million short tons of SO₂ were released into the atmosphere in the area in 1972, and this pollutant is now discharged through a 1250-foot smokestack. The particulate contribution is an additional complicating and phytotoxic factor. For example, in 1971, 192 tons of nickel, 145 tons of copper, 1130 tons of iron and 4.5 tons of cobalt per 28 days from two of the smelters were released as airborne pollutants (Hutchinson and Whitby, 1974). The natural vegetation of the area is a mixed deciduous boreal forest, with white pine (Pinus strobus), jack pine (Pinus banksiana), red maple (Acer rubrum), red oak (Quercus rubra), etc. as dominant trees. This forest, which previously surrounded the mining town of Sudbury, has been devastated over the past 50 yr, especially by the SO₂ emissions and the increased acidity of rainfall and soils. An area in excess of 100 mi² is now almost devoid of vegetation and damage to the forest vegetation is visible over an area of approximately 1800 mil. The increased stack heights to dilute local pollution problems have spread the problem more widely. The pH of rainfall sampled up to 12 mi east of the smallest smelter in 1970 was less than 4.3 and that within 2 mi of the stacks was frequently of less than pH 3.0. Soil erosion has occurred on a large scale as a consequence of loss of vegetation. Metal accumulation in the soils has also been a complicating and probably highly persistent phenomenon. Concentrations of nickel in excess of 3000 ppm and copper of 2000 ppm in surface soils occur widely. The increased acidity of these soils has increased metal mobility and solubility, presenting phytotoxic problems. The effects on the soil chemistry, especially of organic composition have been profound. They involve an increased metal binding capacity of these soils, and very high levels of sulphur in the purified Tulvic acid′ fraction itself. Indeed, the evidence is suggestive of the incorporation of sulphonic groups into the changed extracts. Such profound and damaging changes may be merely a consequence of the extreme conditions experienced at Sudbury or they may be a harbinger of things to come in many potentially podsolic soils in areas of increasing acidity of rainfall.     

Pond sediments as historical record of heavy metals fallout

Well preserved pond sediments were dated as a function of depth by the Pb-210 geochronological method for the past 100 yr. The results have been checked with Cs-137 analysis for the last 30 yr. Mineralogical composition is very constant along the sediment core indicating mechanical erosion of local outcrops as bulk sediment origin. The contents of Al, Cu, Pb, Zn, Cd, and As have been determined and enrichment factors normalized to A1 value were calculated. Copper is mainly of natural origin, and As is influenced by local agricultural use. The anthropogenic source of Pb, Zn, and Cd is clearly provided by atmospheric fallout which is supported by comparison with atmospheric fluxes for wet and dry deposition.     

Use of sequential extraction to evaluate the heavy metals in mining wastes

Lead-zinc mine tailings from the ‘old lead-belt’ in Missouri were chemically characterized using total chemical analysis and sequential extraction. These tailings have been considered as an inert and safe material for years. However, the levels of heavy metals in these tailings were found elevated with Pb values as high as 5000 ppm. The sequential extraction results indicated that the Pb was primarily found in the residual fraction and probably is in the PbS form. Some Pb was found in the oxide fraction. Cu, Zn, and Cd were found in several different fractions, but primarily in the residual fraction. Some Cu was found in the organic fraction. The Zn showed a wide variation between samples with high levels in the carbonate, oxide and residual fractions. Very little Pb, Cd, Cu, and Zn was leached by water. The heavy metals in these tailings do appear to be in the more inert forms and should not be readily available to the environment unless there is an interaction of the tailings with acids, microorganisms or chelating materials. The breathing and ingestion of this material may provide such an environment for such interactions and these materials should still be considered dangerous and managed properly.     

Deposition of airborne mercury near point sources

The deposition of Hg emitted into the atmosphere by a power plant and an incinerator has been calculated. Separate results are presented for wet and dry scavenging processes acting on both the adsorbed and vapor phases. Some localized deposition occurs, leading to a slow increase in the Hg levels of soil and surface runoff, but most of the emission remains airborne for relatively long distances, typically tens of kilometers.     

Use of regulatory documents for assessing the contamination of soils with heavy metals

The chronological review and analysis of the existing regulatory documents relevant to the assessment of soil contamination with heavy metals have been presented. Attention has been given to the incorrect use of the term “total heavy metal content” and the method of its determination in a 5 M nitric acid solution recommended by some regulatory documents. The maximum permissible concentrations (MPCs) and tentatively permissible concentrations (TPCTPCs) for the total heavy metal contents are based on the above method; therefore, the conventional methods of determining the true total contents of heavy metals overestimate the degree of contamination. To avoid confusion, it has been proposed to call the content of a heavy metal in a 5 M nitric acid solution the “pseudototal” content and to compare the experimental results with the MPC or TPCTPC values only if the methods recommended by the regulatory documents were used.     

Solubility and uptake of heavy metals from a Swedish soil

Samples of the surface layer (Ap) and of grass, collected from: (1) grass ley fertilized in the normal way; (2) permanent pasture fertilized in the normal way; and (3) permanent pasture treated with large amounts of sewage sludge five years earlier, were analysed for Mn, Zn, Cu, Cr, Co, Ni, Pb, and Cd.The soil samples were extracted with: (1) distilled water saturated with CO₂; (2) 1 M neutral ammonium acetate; (3) ammonium acetate + acetic acid, pH 4.75; and (4) 2 M nitric acid on a waterbath. The efficiency of these extractants differed greatly and, in relative values, was: 1 for H₂O + CO₂, 3.4 for NH₄OAc, 20.7 for NH₄OAc + HOAc, and 343 for 2 M HNO_3- The dissolving effects of the extractants differed markedly with the kind of element.Grass from the field treated with sewage sludge showed much higher contents of Mn and Zn and somewhat higher contents of Cu and Pb than grass from the untreated field. The levels of Cr, Co, Ni, and Cd were practically uninfluenced by the treatment. Grass from a field close to a highway accumulated large amounts of air-borne Pb and Cd during the summer.It is concluded that the total contents of heavy metals in soils have only limited importance for the uptake by plants. Weak extractants therefore give better information about the plant-available amounts in soils.     

Mobility of heavy metals in pine forest soils as influenced by experimental acidification

The mobility of Pb, Zn, Cd and Cu was examined at two adjacent experimental plots at åmli, southern Norway, B-1 and B-2. Both experiments were established on the same glacifluvial deposits, with forest consisting of uniform stands of Pinus sylvestris L. The forest in B-1 was planted between 1968 and 1970, while B-2 consisted of naturally regenerated trees. The experiments included plots supplied with artificial rain of varying acidity over a period of seven and eight years for B-1 and B-2, respectively, in addition to control plots. In experiment B-1, experimental acidification was carried out both in unlimed plots and in plots applied with three different levels of lime. The two experiments showed distinct differences with respect to effects of the acidification on mobilization of heavy metals from the O horizon. In experiment B-1, the amount of Zn and Cd decreased with decreasing pH in artificial rain, while Pb and Cu were not appreciably affected. The reduction in Zn and Cd concentrations ceased after termination of the acidification experiment. Liming reduced the leachability of Zn, but still appreciable amounts of Zn were obviously leached from the O horizon during the experiment. In experiment B-2 a high retention even of Zn and Cd was observed in the O horizon, probably due to microbial uptake and accumulation.     

Remediation of a soil contaminated with heavy metals by immobilizing compounds

The labile fraction of heavy metals (HM) in soils is the most important for toxicity for plants and microorganisms. Thus, it is crucial to reduce this fraction in contaminated soils to decrease the negative effect of HM. In a greenhouse experiment, the effects of several additives on the labile fractions of Zn, Cd, Cu, Ni, and Pb were investigated in a soil contaminated during long‐term sewage‐sludge application. The accumulation of HM was studied in the aboveground biomass of wheat (Triticum aestivum L.). The additives used were the clay minerals Na‐bentonite, Ca‐bentonite, and zeolite; the Fe oxides hematite and goethite; the phosphate fertilizers superphosphate and Novaphos. Wheat was planted three times during 5 months, allowed to grow for 7 w, and harvested. Dry matter and HM content of shoots were determined after each harvest. Soil samples were taken after the first and third harvest, and the NH₄NO₃‐extractable HM contents were determined. After the addition of 2% Na‐bentonite as well as 2% Ca‐bentonite, a strong reduction of the labile HM soil fraction and shoot HM concentration was observed. At the end of the experiment, the labile fraction was reduced due to the addition of Na‐bentonite and Ca‐bentonite by 24% and 31% for Zn, by 37% and 36% for Cd, by 41% and 43% for Cu, by 54% and 61% for Ni, and by 48% and 41% for Pb, respectively. Furthermore, the shoot HM concentrations with the exception of Zn were reduced below the phytotoxicity range. Accordingly, the shoot dry‐matter production was significantly increased. The addition of phosphate fertilizers (notably Novaphos) strongly reduced the bioavailability of Pb for wheat plants. By addition of 0.05% Novaphos, the labile fraction and the shoot concentration of Pb were lowered by 39% and 64%, respectively. However, the addition of Fe oxides and zeolite resulted only in a small reduction in HM bioavailability to wheat plants. Among the studied additives, Na‐bentonite and Ca‐bentonite have the most promising potential to reduce the bioavailability for the studied HM.     

Adsorption behavior of heavy metals on biomaterials

We have investigated adsorption of Cd(II) and Pb(II) at pH 2-6.7 onto the biomaterials chitosan, coffee, green tea, tea, yuzu, aloe, and Japanese coarse tea, and onto the inorganic adsorbents, activated carbon and zeolite. High adsorptive capabilities were observed for all of the biomaterials at pH 4 and 6.7. In the adsorption of Cd(II), blend coffee, tea, green tea, and coarse tea have comparable loading capacities to activated carbon and zeolite. Although activated carbon, zeolite, and chitosan are utilized in a variety of fields such as wastewater treatment, chemical and metallurgical engineering, and analytical chemistry, these adsorbents are costly. On the other hand, processing of the test biomaterials was inexpensive, and all the biomaterials except for chitosan were able to adsorb large amounts of Pb(II) and Cd(II) ions after a convenient pretreatment of washing with water followed by drying. The high adsorption capability of the biomaterials prepared from plant materials is promising in the development of a novel, low-cost adsorbent. From these results, it is concluded that heavy metal removal using biomaterials would be an effective method for the economic treatment of wastewater. The proposed adsorption method was applied to the determination of amounts of Cd(II) and Pb(II) in water samples.     

Behavior of heavy metals in forest microcosms

Transport and distribution of heavy metals were determined in soil and vegetation (Acer Rubrum) of intact forest microcosms. Litter from a contaminated forest and baghouse dust from a primary Pb smelter were applied to three of the microcosms, while three uncontaminated microcosms served as controls. Total dosages for Ph, Cd, Zn, and Cu on the treated microcosms were 11.0, 0.128, 0,748, and 0.161 mg cm^?2, respectively. All metals were mobilized in soil and were enriched in at least one tissue component of Acer rubrum. Enrichment of Pb, Cd, and Zn occurred in all Acer tissues; Cu enrichment was found only in leaves. Uptake of metals by Acer rubrum was similar to a contaminated forest in southeastern Missouri and decreased in order: Zn, Cu, Cd, and Pb. Results of this experiment indicate that intact microcosms may be useful in assessing uptake and mobility of toxic chemicals which may be applied to forest ecosystems.     

Spatial and temporal variation of heavy metals in sediment cores from the calcasieu river/lake complex

Sediment cores were obtained from several locations in the Calcasieu River/Lake Complex (Lousiana), including Calcasieu Lake, Calcasieu River, two bayou tributaries, and Lake Charles, during the period from November 1983 to November 1985. The cores were analyzed for Cu, Zn, Cr, and Pb. The approximate sedimentation rate and a core chronology were determined by the use of ¹³⁷Cs and ²¹⁰Pb. The increase in metal concentrations after 1933, particularly along Bayou d'Inde where most industries are located, points to anthropogenic input of these metals to the system. The fact that metal concentrations tend to merge to a common value prior to 1940 throughout the system suggests that geological factors do not contribute to the observed variations in metal concentrations of heavy metals found in this area. The background concentrations of heavy metals found in this study for the Calcasieu River/Lake Complex were: Cu (10 mg kg^?1), Cr (25 mg kg^?1), Pb (8 mg kg^?1), and Zn (40 mg kg^?1), The main emphasis of the study focused along Bayou d'Inde due to the enhanced levels of heavy metals found.     

Conditioning of sediment polluted with heavy metals using plants as a preliminary stage of the bioremediation process: a large-scale study

Purpose

A bioremediation process for sediments contaminated with heavy metals has been developed based on two core stages: (1) conditioning of dredged sludge using plants; and (2) solid-bed bioleaching of heavy metals from the resulting soil-like material using microbially produced sulfuric acid. In laboratory and pilot-scale tests, reed canary grass (Phalaris arundinacea) was found to be best suited for the conditioning process. To demonstrate the feasibility of conditioning in practice, a study on a larger scale was performed.

Materials and methods

The sediment originated from a detritus basin of the Weisse Elster River in Leipzig (Saxony, Germany) and was polluted with heavy metals, especially with zinc and cadmium. The dredged sludge was a muddy-pasty, anoxic, and had a high organic matter content. The experimental basin (base area of 50?×?23 m) was filled with 1,400 m³ of sludge to a height of 1.2 m. Conditioning was carried out in five segments that were planted with pre-cultivated Phalaris plants at two plant densities, sowed with Phalaris seeds using two different seeding devices, and grown over by vegetation. Plant development and changing sediment characteristics were analyzed during two vegetation periods by harvesting plant biomass every 4 weeks and sampling sediment material at two different depths every 2 weeks over a total duration of 475 days.

Results and discussion

At the end of the second vegetation period, the pre-cultivated Phalaris plants had reached a height of 2 m, compared to 1.8 m for the sowed Phalaris seeds. Regarding root penetration and the degree of sediment conditioning, the less expensive sowing techniques yielded similar results to planting pre-cultivated plants. The content of heavy metals in the Phalaris plants was below the permissible limits for Germany. The vegetation evapotranspirated large amounts of water from the sediment and transported oxygen into the anoxic sludge. The water content was reduced from 68 to 37 %. The muddy-pasty sludge turned into a soil-like oxic material with a high permeability to water. The oxidation of sediment-borne compounds lowered the pH from 7.3 to 6.0. Due to the high total precipitation in Saxony in the summer of 2010, a maximum of 65 % of the sediment was conditioned.

Conclusions

The feasibility of the first core stage of the bioremediation process for sediments was demonstrated in practice by conditioning 1,400 m³ of dredged sludge using reed canary grass. To establish the proposed sediment treatment in practice, the applicability of the central core stage–solid-bed bioleaching of conditioned soil-like sediment–will also be tested at a larger scale.