Total Trace Metal Content Research Articles

The environmental risk assessment of urban soils pollution with trace elements in the Arkhangelsk industrial agglomeration

In this paper, an ecological and economic approach is proposed to assess the environmental risks of soil pollution in the Arkhangelsk industrial agglomeration, where the most important indicator of risk is the amount of probable damage. Based on the total content of trace metals in the surface soil layer, the degree of the ecological risk, the probability of further pollution, and the magnitude of the probable damage have been determined. It was found that Arkhangelsk, Severodvinsk and Novodvinsk soils are characterized by a weak degree of ecological risk for most sample plots with the probability of further contamination from 20 to 40%.

Distribution and Characterization of Heavy Metal and Pollution Indices in Landfill Soil for Its Rehabilitation by Phytoremediation

Population growth associated with urban development in African cities is a key environmental concern in development programs. Indeed, urban areas are strongly impacted by the production of municipal waste, the management of which remains problematic and is only stored in open dumps. This is the case in the city of Bonoua, a small town located 59 km east of Abidjan in the South Comoé region of Côte d’Ivoire. The management of municipal waste in this town is crucial because all the mineral water sources are concentrated in this town. The objective of this study is to characterize and map the distribution of trace metal elements in the largest urban landfill in the city in order to propose an efficient strategy for rehabilitation into an urban park. Soil samples were collected from the entire site (landfill and surrounding soil) and from a control site. The total content of trace metals (Pb, Cd, Cr, and Zn) in the soil was analyzed by X-ray fluorescence spectrometry (XRF). Soil pollution was evaluated through enrichment factors, geoaccumulation indices and pollution indices. The results show that the calculated geoaccumulation indices and their distribution maps indicate a pollution of the site in these elements. The values of the PI higher than the unit reveal a pollution of the site in several elements. The levels of Pb, Cd, Cr and Zn are higher than the levels in the upper continental crust and in the control soil. The spatial distribution shows a significant accumulation of Pb, Cr and Zn on the landfill while Cd is concentrated in the surrounding soils. The calculated enrichment factors suggest an anthropogenic origin of the heavy metal at the study site. These results indicate polymetallic pollution by metals that can persist in the environment and affect human health.

Climatic control of major and trace elements in paddy soils from wet and dry regions of Sri Lanka

Rice cultivation is a widespread agricultural practice in the dry and wet climatic zones of Sri Lanka. Due to the excessive application of agrochemicals, paddy soils are considered to be polluted, particularly with toxic trace elements. To assess the major and trace element levels in rice paddy soils, 97 samples were collected from the main two climatic regions of Sri Lanka. Total and exchangeable contents of 12 major and trace elements, i.e., Na, K, Ca Mg, Fe, Mn, Cr, Ni, Zn, Pb, Cu, and As were analyzed. Geo-accumulation index and Potential Bioavailability Factor (PBF) was employed to assess the levels of contaminations and results were statistically compared. Paddy soils from both climatic zones contained over 5.0 mg/kg of available–P, which is almost equal to the optimum levels required for rice plants. The total content of trace metals varied in the order Fe>Mn>Zn>Cu>Ni>As in both dry and wet zones, while major elements increased in the order Mg>K>Na. Geo Accumulation indices (Igeo) showed that almost all soils were uncontaminated to moderately contaminated with trace elements.

Trace metal availability in soil horizons amended with various urban waste composts during 17 years – Monitoring and modelling

Recycling organic residues in agrosystems presents several benefits but faces the question of contaminants, among them a few trace metals which eventually accumulate in soils following regular applications of organic waste products (OWP) and represent an ecological risk. The increase of total trace metal contents in amended topsoils can be predicted by a mass balance approach, but the evolution of their available fractions is a more intricate issue. We aimed at modelling this evolution by using the dataset of a long-term field experiment of OWP applications (manure and three urban waste composts). Two operationally-defined fractions of 6 trace metals have been quantified in the OWP and amended topsoils between 2002 and 2015: the soluble and potentially available metals, extracted in 0.01 M CaCl2 and 0.05 M EDTA solutions, respectively.The potentially available metals have progressively increased in amended topsoils, at rates depending on elements and types of OWP. For Zn, these increases corresponded in average to inputs of potentially available Zn from OWP. But the soil stocks of potentially available Cu increased faster than from the inputs of EDTA-extractable Cu, showing linear regression slopes between 1.4 and 2.5, depending on OWP type. The influence of OWP has been provisionally interpreted in the light of their efficiency to increase soil organic matter and their inputs of reactive oxides.Soluble copper has increased with repeated amendments. But soluble cadmium, nickel and zinc have generally decreased, as they are influenced by changing soil variables such as pH and organic matter. Statistic models were used to unravel the relationships between soluble and EDTA-extractable metals and other soil variables. For Cu, the most satisfactory models just relate soluble and potentially available Cu. Developing such models could contribute to predict the long-term effects of a precise scenario of agricultural OWP recycling upon available trace metals in soils.

Speciation analysis and bioaccessibility evaluation of trace elements in goji berries (Lycium Barbarum, L.)

Goji berries (Lycium Barbarum, L.) are known for their nutritional potential as a great source of trace metals (e.g., copper, zinc and manganese) which are present in the form of highly bioaccessible compounds. In order to assess the bioaccessibility of trace elements and to identify compounds responsible for better bioaccessibility of copper and zinc, an in vitro simulation of gastrointestinal digestion was used in this study.The total content of trace metals was evaluated using sample digestion followed by inductively coupled plasma mass spectrometry. Bioaccessibility of trace elements was estimated by size exclusion chromatography coupled to inductively coupled plasma mass spectrometry. These analytical methods were used to analyse samples of goji berries to determine the highest amount of elements. For total trace metal content in goji berries, Zn had the highest level of the three studied (10.6μgg−1), while the total content of manganese and copper was 9.9μgg−1 and 6.1μgg−1, respectively.Additionally, the analysed metals were found to be highly bioaccessible to the human body (about 56% for Mn, 72% for Cu and 64% for Zn in the gastric extract and approximately 35% for Mn, 23% for Cu and 31% for Zn in the case of gastrointestinal extract). To obtain information about metal complexes present in goji berries, extraction treatment using different solutions (ionic liquid, HEPES, SDS, Tris-HCl, ammonium acetate, water) was performed. Enzymatic treatment using pectinase and hemicellulase was also checked. Extracts of berries were analysed by SEC-ICP-MS and μHPLC–ESI–MS/MS techniques. The ionic liquid and pectinase extraction helped efficiently extract copper (seven compounds) and zinc (four compounds) complexes. Compounds identified in goji berries are most likely to be responsible for better bioaccessibility of those elements to the human organism.

Assessment of Geochemical Environment from Study of River Sediments in the Middle Stretch of River Ganga at Ghazipur, Buxar and Ballia area

In order to investigate geochemical environment of the river Ganga, the freshly deposited sediment samples were collected from Ghazipur, Buxar and Ballia urban centers in the pre-monsoon period (May, 2010). The river receives industrial as well as domestic wastes from various drains of above mentioned cities. River Ganga has been one of the major recipients of the industrial effluents in India. The present study assesses the current status of the distribution and concentration of seven heavy metals (Cr, Co, Ni, Cu, Zn, Cd and Pb) in the river sediment at the three urban centers. The total trace metal content in sediment samples were analyzed by atomic absorption spectrophotometer and obtained values were compared with different standard values. The heavy metal concentrations were recorded in the following ranges (mg/kg) Cr (113–230), Co (11–29), Ni (32–75), Cu (39–73), Zn (72–140), Cd (0.45–0.95) and Pb (15–27). Results show that the mean concentration of Cr, Cd, Zn, Cu and Co in sediment at all urban centers exceeded the average worldwide shale concentration. However the mean concentration of Ni and Co was lower than it. Metal enrichment factor (EFc) for all sampling stations was recorded between 0 and 3. The maximum EFc was 1.82 for Cr, 1.18 for Co, 0.87 for Ni, 1.33 for Cu, 1.15 for Zn, 2.43 for Cd and 1.05 for Pb. The exceptionally high EFc value was recorded for Cd at all sampling stations. High EFc value indicates that large amount of pollutants are added through anthropogenic sources. The percentage of anthropogenic and lithogenic values of heavy metal concentration indicates that Cd receives highest value of anthropogenic addition into stream and it is followed by Cr, Cu, Zn and Co. Geoaccumulation indices showed that sediment was uncontaminated to moderately contaminated and may adversely affect the fresh water ecology of the river. Toxicity reference value indicates that the river bed sediment is toxic to benthos organisms for most of the undertaken metals. The data generated may provide useful information to Governmental agencies to control the heavy metal pollution of the river Ganga sediment at these urban centers which may even be worst with the increasing population load in the basin.

Heavy metals contamination in water and sediments of an urban river in a developing country

Water and sediment samples were collected from 20 location of the Buriganga river of Bangladesh during Summer and Winter 2009 to determine the spatial distribution, seasonal and temporal variation of different heavy metal contents. Sequential extraction procedure was employed in sediment samples for the geochemical partitioning of the metals. Total trace metal content in water and sediment samples were analyzed and compared with different standard and reference values. Concentration of total chromium, lead, cadmium, zinc, copper, nickel, cobalt and arsenic in water samples were greatly exceeded the toxicity reference values in both season. Concentration of chromium, lead, copper and nickel in sediment samples were mostly higher than that of severe effect level values, at which the sediment is considered heavily polluted. On average 72 % chromium, 92 % lead, 88 % zinc, 73 % copper, 63 % nickel and 68 % of total cobalt were associated with the first three labile sequential extraction phases, which portion is readily bioavailable and might be associated with frequent negative biological effects. Enrichment factor values demonstrated that the lead, cadmium, zinc, chromium and copper in most of the sediment samples were enriched sever to very severely. The pollution load index value for the total area was as high as 21.1 in Summer and 24.6 in Winter season; while values above one indicates progressive deterioration of the sites and estuarine quality. The extent of heavy metals pollution in the Buriganga river system implies that the condition is much frightening and may severely affect the aquatic ecology of the river.

Assessment of extractability of Cu, Cr, Ni, Pb and Zn in some chilean biosolid-amended soils by using BCR sequential extraction procedure

The effect of biosolid application on the distribution and extractability of Cr, Cu, Ni, Pb, and Zn was assessed in Mollisol soils from an important agricultural zone in central Chile. These were amended with biosolids at the amounts of 15 and 30 Mg ha-1 and incubated for 60 days under controlled conditions of moisture and temperature. Four domestic biosolids were obtained from the monofill at one of the Santiago wastewater treatment plants. Biosolid and soil sequential extraction was performed according to the procedure recommended by BCR, which considers four extractions to obtain an acid-soluble fraction (exchangeable, carbonates), a reducible fraction (iron/manganese oxides), an oxidizable fraction (organic matter and sulfides) and the residual one. Trace metals were determined by flame atomic absorption spectrometry and inductively coupled plasma mass spectrometry. Among the metals determined in biosolids, Zn had the highest concentration. Total trace metal contents found, except for Ni in some biosolids, was below the limits allowed by the Chilean regulation for biosolids. In general, without considering the residual fraction, the metals were found predominantly as reducible and oxidizable fractions. A multifactorial design was applied to assess the effects of biosolid application amounts, biosolid type and incubation time. Biosolid incorporation at the amount of 30 Mg ha-1 produced an increase in Zn and Ni availability in all soils and Cu in most of them, while Cr, and Pb showed no significant variations. In general, the factors incubation and type of biosolid did not show remarkable effects compared with initial conditions.

Investigation of trace element mobility in river sediments using ICP-OES

In this study, the column method was used to determine the leachable trace metals present in selected river sediments. In addition the sediments were investigated using a shaker method and these two methods were compared for reliability. For both these methods extract solutions associated with a sequential extraction method were used. However, the sediments were only subjected to one extractant solution and not to the whole sequential procedure. The river sediments were also subjected to a digestion procedure to determine the total trace metal content. Simulated pollution experiments were performed where the sediments were also spiked to give known concentrations of trace metals. These results were very useful, especially in cases where certain trace metals were not currently present in river sediments. From the results achieved in this study the general trace metal status of the sediments can be established. From the results achieved it was established that in the case of the less impacted rivers (Crocodile and Olifants Rivers) only slight changes in the river conditions are needed to mobilise the trace metals present. From the results of the Blesbokspruit it was seen that urgent attention is needed to prevent further damage to the system. Water SA Vol. 31 (2) 2005: pp.183-192

Geochemistry and partitioning of trace metals in paddy soils affected by metal mine tailings in Korea

Soil solution samples were extracted from paddy soil near mine tailing dumps in an abandoned mine in Korea. Trace metals in the soil solution and soil solid (As, Cd, Cr, Cu, Ni, Pb and Zn) were analysed, along with the mineralogical composition of the soil, using XRD. Sequential extraction was also undertaken for speciation of different fractions bound to the soil solid. Kaolinite was the main clay minerals and the CEC value was relatively low, recording between 11.0 and 27.5 meq/100 g. Comparison of the paddy soil with the control soil samples collected from an uncontaminated area revealed that nearly all the paddy soil samples were enriched for trace metal contents. Cadmium, Pb and Zn concentrations exceeded the intervention values of the Dutch standards, which requires remediation action. Arsenic, Ni and Cr were below the values, indicating little or no contamination for these metals. The trace metal contents in the paddy varied with distance from the mine tailing site. In addition to the changes with distance, higher proportions of relatively easily releasable fractions, such as exchangeable forms, were found to be proportional to the total trace metal contents in the soil sample. Although most paddy soil samples were enriched with respect to some trace elements, concentrations of Cd, Cu, Ni and Pb in the solution were very low, recording maximum levels of up to only several milligrams per liter. Geochemical equilibrium modelling using PHREEQC indicates the presence of solubility controlling solid phases for Cd and Pb, whereas Zn and Cu seem to be controlled by adsorption/desorption processes. We presumed that either iron sulphides or oxides removed dissolved trace elements. Under reducing conditions, iron may be dissolved as Fe 2+ in the soil solution and then the reduced iron possibly would form iron sulphide precipitates with sulphur from the mine tailings. On the contrary, in an oxidizing condition, iron exists as the oxidised form, Fe 3+, and again forms iron oxides, which is a good adsorbent for trace elements in soil environments. A Cycle of dry and flooded conditions is characteristic for paddy fields. Therefore, either iron sulphide or iron oxide is believed to provide a good adsorbing site for trace metals and so explains the subsequent low concentrations in the soil solution. Despite the low trace metal concentrations in the soil solution, higher portions of the trace metals still exist as relatively easily available form in the soil solid. It should be stressed that controlling of the redox condition and pH would be important in managing the transport of trace metals in the paddy soil that was affected by the mine tailings.

Speciation distribution of Cd, Pb, Cu, and Zn in contaminated Phaeozem in north-east China using single and sequential extraction procedures

Knowledge of the total content of trace metals is not enough to fully assess the environmental impact of polluted soils. For this reason, the determination of metal speciation in soil is important to evaluate its mobilisation capacity and behaviour in the environment. The sequential extraction procedure was used to separate 4 heavy metals (Cd, Pb, Cu, Zn) from contaminated Phaeozem in north-east China into 5 operationally defined geochemical species: exchangeable, bound to carbonates, bound to Fe–Mn oxides, bound to organic matter, and residues. Neutral salts, dilute acids, and chelating reagents were used as single extractants for the functionally defined speciation. In the sequential extraction, the residual fraction was the most abundant pool for Pb, Cu, and Zn. A major portion (40–84%) of Pb, Cu, and Zn was associated with the residue. The speciation distribution of Pb, Cu, and Zn in the surface samples was similar to that in the subsurface, with residues > bound to organic matter > bound to Fe–Mn oxides > bound to carbonates > exchangeable. A significant amount (32–47%) of Cd persisted in the potential availability of the exchangeable fraction. The main part of Cd fractionation in the surface soil samples comprised exchangeable, carbonate, and Fe–Mn oxide fractions, whereas in the subsurface it comprised the residual and exchangeable phases. EDTA can be regarded as an extractant for assessing the plant-available species of Cd, Cu, and Zn; NH4Cl released electrostatically weakly bound metals and was used to estimate the mobile species. Assuming that metal mobility and bioavailability are related to their solubility and the contents in typical plants in the contaminated Phaeozem, Cd would be the main potential risk to animal health and groundwater safety in the area.

Use of major‐ and trace‐element correlations to assess metal migration in sandy Luvisols irrigated with wastewater

SummarySoils irrigated with raw wastewater for many years accumulate trace metals, especially in the surface horizon. We do not know, however, to what extent the metals migrate down the profile and whether they accumulate in deeper horizons. We assessed the migration of trace metals in the suburbs of Paris where market gardens had been irrigated with wastewater for more than 100 years. Within a soil series, we compared metals in the polluted soils with those of a reference soil of the same kind. We sampled by horizons three representative Luvisol profiles in the irrigated area and a fourth profile selected as a reference just outside the irrigated area. Large quantities of Zn, Pb, Cd and Cu appeared to have accumulated in the topsoil, at the base of which concentrations diminished markedly. There appeared to be appreciable migration into the subsoil only at the most intensely irrigated site. By relating the total trace metal contents to the total iron contents we could detect anomalous values and identify migration into the subsurface horizons more sensitively. This approach was tested first with the endogenous metal Cr, then with metal pollutants. We showed that Zn, Pb, Cd and Cu migrated downwards in all three irrigated soils.

Levels and speciation of heavy metals in soils of industrial Southern Nigeria.

A knowledge of the total content of trace metals is not enough to fully assess the environmental impact of polluted soils. For this reason, the determination of metal species in solution is important to evaluate their behaviour in the environment and their mobilization capacity. Sequential extraction procedure was used to speciate five heavy metals (Cd, Pb, Cu, Ni and Zn) from four contaminated soils of Southern Nigeria into six operationally defined geochemical species: water soluble, enchangeable, carbonates, Fe-Mn oxide, organic and residual. Metal recoveries were within +/- 10% of the independently determined total Cd, Pb, Cu, Ni and Zn concentrations. The highest amount of Cd (avg. 30%) in the nonresidual fractions was found in the exchangeable fraction, while Cu and Zn were significantly associated with the organic fraction. The carbonate fraction contained on average 14, 18.6, 12.6, 13 and 11% and the residual fraction contained on average 47, 18, 33, 50 and 25% of Cd, Pb, Cu, Ni and Zn respectively. Assuming that mobility and bioavailability of these metals are related to the solubility of the geochemical form of the metals, and that they decrease in the order of extraction sequence, the apparent mobility and potential bioavailability for these five metals in the soil were: Pb > Zn > Cu > Ni > Cd. The mobility indexes of copper and nickel correlated positively and significantly with the total content of metals, while mobility indexes of cadmium and zinc correlated negatively and significantly with the total content of metals.

Spatial trends in the chemical composition of sediments on the continental shelf and slope off the Mediterranean coast of Israel

In order to determine whether observed trends in total trace metal content were natural or due to anthropogenic inputs, major and trace elements were measured on three size fractions (fine sand (250–63 μm), silt and clay (<63 μm) and clay (<2 μm)) of sediment collected off the Mediterranean coast of Israel. Partitioning of trace metals into carbonate/exchangeable, iron oxide and residual phases for each grain size was also determined. The dominant source of particles was Nile derived material. There was a decrease in Fe/Al, Ti/Al and non-carbonate Mg/Al in the fine sand fraction, interpreted as a decrease in heavy minerals towards the north and an increase in K/Al due to increased feldspars and micas. There was a simultaneous increase in CaCO 3 both towards the north and onshore in all grain size fractions due to a northward increase in local biogenic fragments and river detritus. This is consistent with circulation and sediment transport models for the southeast Levantine basin. The background trend in trace metals corresponds to changes in mineralogy. While the fine sand fraction appeared free of contamination, in the finer fractions there is a significant enrichment of Zn, and Cd towards the north, which is not accounted for by changes in mineralogy. The sediments were also enriched in Cu, Zn and Cd near Tel Aviv and Hadera. The peaks near Tel Aviv may correspond to waste discharged through the Yarqon and an old sewage pipe, whilst near Hadera, the Alexander and Hadera Rivers and the terminal for a coal-fired power station may be the source of contamination. There was also clear evidence for contamination by Pb in the finest sediments. However, there was no enrichment in Pb around the point sources of the other trace metals, therefore it was concluded that the majority of Pb contamination was from the atmosphere. All trace metal contamination may be subject to ‘smearing’ by sediment transport, particularly in the clay fraction.

Intracellular determination of elements in mammalian cultured cells by total reflection X-ray fluorescence spectrometry

TXRF (total reflection X-ray fluorescence spectrometry), a rapid and reliable multi-element method, was applied to quantify intracellular concentrations of trace and non-trace elements in different mammalian cell lines. The coordinated variations in their intracellular contents were determined when the extracellular concentration of one of them was modified. The results indicate that TXRF permits the detection of total trace metal contents using a minimum amount of cells [(1-2)×10 6 ), while (4-6)×10 6 cells were sufficient to determine their cytosol/pellet distribution. In the six cell lines analyzed, the order of relative abundance for trace and non-trace elements was Cu<Fe<Zn and Ca<S, respectively. One of the cell lines was exposed to increased amounts of extracellular copper (0.44 to 100 µmol l –1 ), and then transferred to a culture medium containing a minimum concentration of the metal (0.44 µmol l –1 ). Under this condition, it was possible to measure both the rise (28-fold) in the intracellular copper content and its recovery to a base concentration. In addition, intracellular levels of other elements were measured, indicating that Fe and Ca showed the highest increase (1.7- and 2.2-fold respectively). On the other hand, the Zn/Fe ratio was hardly affected, suggesting that this ratio can be used as an internal marker of metabolic integrity in cells exposed to different extracellular copper concentrations. These results indicated that TXRF is an adequate method to measure simultaneously the intracellular concentration of different elements and permits the evaluation of their variations in response to modified concentrations in the extracellular medium of one element.

Trace metals in sediment cores from the Campeche shelf, Gulf of Mexico

Trace metals in sediment cores from the Gulf of Mexico, in the Campeche shelf area were studied to investigate possible variations in their vertical and/or horizontal sedimentary distributions. Possible links to petroleum sources were investigated as this area contains very productive oil explotation and transportation activities. Sediments were collected undisturbed using a vegematic type box corer. The upper 10 cm. were collected and cut in sections of 2 cm each. Incomplete, open vessel sediment digestion and atomic absorption was used for trace element determination. Particular interest was placed on vanadium and nickel concentrations as they have been associated to oil. Several metals were measured and representative distributions are presented. Horizontal distributions appear to conform to predominant current circulation patterns reported and closeness to sources of sedimentary materials. Vertical distributions are discussed. The vertical distributions were strikingly constant. Correlation among metals are also presented. Fe was used as a normalizing agent and the carbonate content was acting as a diluter of total trace metal content.

Study of lability of heavy metals in wines with different degrees of aging through differential pulse anodic stripping voltammetry

DPASV is a precise, highly sensitive, low-cost analytical technique which allows for the determination of total content of trace metals and at the same time provides information on the stability of metal-ligand unions. In this study, the content of Zn, Cd, Pb, and Cu in three wines with different aging periods subjected to three different treatments (digestion, acidification to pH 1, and dilution) was studied to determine total metal concentration and distinguish the labile fraction from that displaceable by acids. Previously, the influence of deposition time and sample volume on potential and intensity of each metal was studied

Trace metals in sediments from the “Ria de Huelva”

The Ría de Huelva is an estuarine zone into which flow the Odiel and Tinto rivers, polluted by trace metals. Total contents of Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Pb, Cd and Hg were determined in the < 630 and < 63 μm fractions of bed sediments. Total trace metal contents in the coarsest fraction are lower than in the finest, although both are highly correlated for most of the metals, allowing an easy grain size effect correction. Total concentrations of Cu, Zn, As, Pb and Hg are very high, having enrichment factor indexes ranging from 35–171. Important proportions of these are in easily soluble and reducible physico‐chemical forms, which are readily available for living organisms.

NUTRIENT REQUIREMENTS OF THE DINOFLAGELLATE PERIDINIUM GATUNENSE1

ABSTRACTOptimum nutrient conditions for growth and photosynthesis of Peridinium gatunense (Nygaard) (Peridinium cinctum fa. westii) were investigated using axenic clones in batch cultures. Selenium (Se) had previously been found to be an indispensable growth factor for P. gatunense. Optimal, suboptimal, and supraoptimal concentrations of HCO3−, N, Ca, Cl, Mg, P, K, S, Si, EDTA‐Na, Fe, Mo, Zn, Mn, Co, Se, B, Br, I, and various trace element mixtures were determined by measuring biomass development, growth rates, 14C uptake, and/or oxygen production at various concentration gradients of these elements. The general characteristics of the best formulation, medium‐L 16, relative to other media, are its high content of NaHCO3 (1 meq · L−1) and Mo (0.2 μM) but low concentrations of NO3‐N (150 μM), PO4‐P (10 μM), and Fe (0.4 μM), in addition to its content of Se. The total content of trace metals, except for Se, may be reduced to one‐fourth of that in medium‐L 16 without altering the major growth‐promoting properties of the medium. Medium‐L 16 deviated considerably from Lake Kinneret (Israel) water, being much lower in macroelements except for N and P. The pH (8.1–8.4) was in the same range, but the values of conductivity (140 μS · cm−1), alkalinity (1 meq · L−1) and NaCl (200 μM) were &gt; 8, 2, and 30 times higher, respectively, in the lake water. Selenium deficiency may limit the growth of P. gatunense in this lake.

The Effect of Deicing Salts on Trace Metal Mobility in Roadside Soils

AbstractCalcium magnesium acetate (CMA) (Ca0.3Mg0.7(C2H3O2)2) is being used as an alternative to NaCl for deicing highways. CMA is an effective deicer, handles well, biodegrades, is less toxic to aquatic life, and is less corrosive than Cl salts. There is some concern, however, that CMA may increase the mobility of certain trace metals from roadside soils. Roadside soils were collected from around the USA from high‐traffic and high‐salt use areas. These soils were characterized for total trace metal content as well as important chemical and physical parameters. Studies were carried out to determine (i) the effect of CMA decomposition on Pb and Cd concentrations in an aqueous system (no soil), (ii) changes in major and minor element chemistry in soils incubated with NaCl and CMA solutions, and (iii) the mobility of trace metals from soil columns leached with solutions of deicing chemicals and/or H2O. Microbial decomposition of the acetate resulted in increased pH, CaCO3 precipitation, and immobilization of Cd either through coprecipitation with CaCO3 or CdCO3 precipitation. There was no difference in trace metal solubility in soils treated with H2O or 10 mmolc L−1 CMA or NaCl (average runoff concentration). Trace metal concentrations were initially high in soils treated with 100 mmolc L−1 solutions of deicing salts but concentrations decreased with time due to adsorption or precipitation reactions. The leachability of Pb from soil columns was strongly correlated with organic matter solubilization. Soils leached with NaCl followed by distilled water had reduced permeabilities as compared to CMA‐leached soils. It appears the effect of CMA on trace metal mobility in roadside soils should generally be beneficial.