Recovery and characterization of α-zein from corn fermentation coproducts

Zeins were isolated from corn ethanol coproduct distiller's dried grains (DDG) and fractionated into α- and β γ-rich fractions. The effects of the ethanol production process, such as fermentation type, protease addition, and DDG drying temperature on zein recovery, were evaluated. Yield, purity, and molecular properties of recovered zein fractions were determined and compared with zein isolated from corn gluten meal (CGM). Around 29-34% of the total zein was recovered from DDG, whereas 83% of total zein was recovered from CGM. Process variations of cooked and raw starch hydrolysis and fermentation did not affect the recovery, purity, and molecular profile of the isolated zeins; however, zein isolated from DDG of raw starch fermentation showed superior solubility and film forming characteristics to those from conventional 2-stage cooked fermentation DDG. Protease addition during fermentation also did not affect the zein yield or molecular profile. The high drying temperature of DDG decreased the purity of isolated zein. SDS-PAGE indicated that all the isolated α-zein fractions contained α-zein of high purity (92%) and trace amounts of β and γ-zeins cross-contamination. Circular dichroism (CD) spectra confirmed notable changes in the secondary structure of α-zeins of DDG produced from cooked and raw starch fermentation; however, all the α-zeins isolated from DDG and CGM showed a remarkably high order of α-helix structure. Compared to the α-zein of CGM, the α-zein of DDG showed lower recovery and purity but retained its solubility, structure, and film forming characteristics, indicating the potential of producing functional zein from a low-value coproduct for uses as industrial biobased product.     

Fractionation of tropical soilborne heavy metals—Comparison of two sequential extraction procedures

We compared Cr, Cu, Ni and Zn fractionation patterns in four typical soils naturally containing high levels of these elements on the tropical volcanic island of Réunion. Two sequential chemical extraction procedures were used: the modified four-stage BCR procedure (subsequently called mBCR) and the modified six-stage Geological Survey of Canada procedure (subsequently called mGSC). The results obtained by these two procedures highlighted some similarities. With both approaches, exchangeable fractions were the smallest fractions with respect to the four heavy metal (HM) distributions (< 5% of the total HM quantity), and residual fractions had the highest Cr, Cu, Ni and Zn contents (39.1–97.9%) in the four soils. In contrast, we noted differences in HM fractions bound to organic matter. These differences could be explained by the different reagents and extraction sequences implemented in the two procedures. However, the most marked difference in the results obtained by the two procedures concerned the HM fraction bound to oxyhydroxides, despite the fact that the same reagent was used (hydroxylammonium chloride). Our results revealed that the mBCR procedure underestimated the proportion of HM bound to this fraction. The mGSC procedure therefore seems more suitable for analysing tropical soils which typically contain high levels of Fe and Mn oxyhydroxides.     

Investigating speciation and toxicity of heavy metals in anoxic marine sediments—a case study from a mariculture bay in Southern China

Purpose

The pollution of marine sediments by heavy metals is still a major concern, especially in zones affected by industry or mariculture. Toxicity of sediment heavy metal contents may be assessed using sequential extraction (SE) procedures, minding inherent constraints of such approaches. In this study, we investigated heavy metal speciation and toxicity in anoxic marine sediments in Zhelin Bay, a mariculture bay in Southern China, using an SE and acid volatile sulfur-simultaneously extracted metals (AVS-SEM) approach.

Materials and methods

Speciation of Cd, Cu, Ni, Pb, and Zn were studied by a modified SE of five fractions, adapted to separate organic and sulfidic metal fractions in anoxic sediments: F1 weak acid soluble (readily available), F2 reducible fraction, F3 organic matter-bound fraction, F4 sulfide-bound fraction, and F5 residually bound fraction. Toxicity predictions based on the sum of non-residual (NR) metal fractions from sequential extraction were compared to predictions based on AVS-SEM.

Results and discussion

Results showed that Cd, Ni, and Pb predominantly occurred in the weak acid soluble fraction (F1), residual fraction (F5), and sulfide-bound fraction (F4), respectively; Cu and Zn were mainly obtained in F4 and F5. Based on the distribution of indicator elements for metal fractions, the SEM from AVS extraction included different yields of non-residual and residual fractions besides the sulfidic fraction. Estimates for potential heavy metal toxicity based on NR metals of the SE procedure were thus based on a better-defined speciation compared to the simplistic approach of the AVS-SEM method.

Conclusions

Based on the contents of NR metals and normalizing them by organic matter content, toxic effects are not expected for any of the sampling sites, irrespective of the presence or absence of mariculture. Using Pearson correlation analysis to identify predominant fractions influencing toxicity, we conclude that toxicity of heavy metals in anoxic sediments can be well predicted by their non-residual heavy metal contents.

     

Effects of autumn foliar application of 15n‐urea on nitrogen storage and reuse in apple 1

Effects of autumn foliar application of N‐urea on N storage and reuse in young apple seedling (Malus Pumila Mill.) were studied. Foliar application of urea^‐15 N (3.5%) during autumn enhanced the retranslocation of leaf N to other plant parts and increased stored N. Foliar N sprays increased the proteolytic activities of the leaves; therefore, such activities appear to be a major mechanism of retranslocation of leaf N. Foliar applied N enabled the plant to produce more growth during the following seasons. A considerable portion of the plant total N during second and third years was attributable to the foliarly applied N during the first year.     

Bioleaching of heavy metals from sewage sludge by Acidithiobacillus thiooxidans—a comparative study

Purpose

To understand the bioleaching of metals from sludge by Acidithiobacillus thiooxidans, the aims of this study were to evaluate the experimental conditions affecting the efficiency of removal of the metals, including solids concentration, initial pH, sulfur concentration and inoculum level were examined, and following the bioleaching mechanism was proposed.

Materials and methods

A. thiooxidans were isolated from collected sludge samples containing bacteria from Fuzhou Jingshan sewage treatment plant, and identification of bacteria by sequencing the 16?s rDNA gene sequences. Conditions affecting the bioleaching and application were conducted by batch experiments. The analysis of Cr, Cu, Pb, and Zn was carried out using an atomic absorption spectrophotometer, and the pH and oxidation?Creduction potential (ORP) were measured using a pH meter and an ORP meter.

Results and discussion

The results show that a high metal leaching efficiency was achieved at low solid concentrations due to decreases in buffering capacity. In addition, the best conditions of the bioleaching included 2?% (w/v) solid concentration, 5.0 gL^?1 sulfur concentration, and 10?% (v/v) inoculum concentration, where the removal efficiencies of Cr, Cu, Pb, and Zn in sewage sludge was 43.6?%, 96.2?%, 41.6?%, and 96.5?%, respectively.

Conclusions

We found that the bioleaching of Zn was governed by direct and indirect mechanisms, while the bioleaching of Cu, Pb, and Cr was mainly dominated by the bioleaching indirect mechanism. After processing with the proposed techniques, the heavy metals in the sewage sludge did meet the requirement of the national standards.     

Fixation and Recovery of Added Phosphorus and Potassium in Different Soil Types of Pulse‐Growing Regions of India

Abstract

Fixation and recovery of added phosphorus (P) and potassium (K) were studied in different soil types of pulse‐growing regions. Amounts of P and K fixed increased in all the soils irrespective of type and texture. With the increase in levels of added P and K, maximum P fixation was observed at lower levels of added P (50 mg kg^?1). Alfisols showed maximum P‐fixation capacity (92.7%), followed by Vertisols (86.5%) and Inceptisols (76.6%) at 50 mg kg^?1 added P. However, K fixation increased with increasing levels of added K up to 200 mg kg^?1, and thereafter fixation either decreased or was maintained at similar levels. Vertisols showed higher K fixation than Inceptisols and Alfisols. Fertilizer P requirement per unit increase in available P in soil was highest in Bangalore (3.23) and lowest in Delhi (2.38). Fertilizer K requirement per unit increase in available K in soil was highest in Raipur and Gulbarga (1.75) and lowest in Ranchi (1.28).     

Dissolution and Fractionation of Calcium—Bound and Iron—and Aluminum—Bound Humus in Soils

This paper deals with the development of a sequential extraction method to separate the Ca-bound and Fe-and Al-bound humus from soils.First,comparative analyses were carried out on dissolution of synthetic organo-mineral complexes by different extractants,i.e.0.1M Na4P2O7,0.1M NaOH 0.1M Na4P2O7 mixture,0.1M NaOH,0.5M (NaPO3)6 and 0.5M neutral Na2SO4.Among the five extractants,0.1M NaOH 0.1M Na4P2O7 mixture was the most efficient in extracting humus from various complexes.0.5M Na2SO4 had a better specificity to Ca than 0.5M (NaPO3)6,by only extracting Ca-bound humus without destorying Fe-and Al-bound organo-mineral complexes.Then sequential extractions first with 0.5M Na2SO4 and then with 0.1M NaOH 0.1M Na4P2O7 mixture were applied to a series of soil samples with different degrees of base saturation.The cations were dominated by Ca in the 0.5M Na2SO4 extract and by Al in the 0.1M NaOH 0.1M Na4P2O7 mixture.The sequential extraction method can efficiently separate or isolate Ca-bound and Fe-and Al-bound humus from each other.     

Composition and Structural Features of Calcium—Bound and Iron—and Aluminium—Bound Humus in Soils

Calcium-bound and iron-and aluminium-bound humus extracted from different soils collected from north to south of China were characterized by chemical and spectroscopic methods.Meaningful differences in the composition and structure between them were revealed by ^13 C NMR,visible spectroscopy and elemental analysis.Results showed that the contents of carbon,hydrogen and nitrogen were higher in iron-and aluminium-bound humus than in calcium-bound humus while oxygen content in calcium-bound humus was shown to be higher .The calcium-bound humus had higher C/N and O/C ratios than iron-and aluminiumbound humus.The calcium-bound humic acid(HA1) showed higher E4/E6 ratios than iron-and aluminumboud,humic acid(HA2)while iron-and aluminum-bound fulvic acid(FA2) showed higher E4/E6 ratios than calcium-bound fulvic acid(FA1).An inverse relationship between E4/E6 ratios and aromaticity as determined by 13C NMR spectra was observerd for HA and FA from black soil.The 13C NMR spectroscopy revealed that HA2 was more aromatic than HA1.On the other ,FA1 exhibited a higher aromaticity than FA2.     

Potentially bioavailable metals in sediment from a tropical polymictic environment—Rio Grande Reservoir,Brazil

Background, aim and scope  Although many recent studies have focused on sediment potential toxicity, few of them were performed in tropical shallow aquatic environments. Those places can suffer short-time variations, especially due to water column circulations generated by changes in temperature and wind. Rio Grande reservoir is such an example; aside from that, it suffers various anthropogenic impacts, despite its multiple uses. Materials and methods  This work presents the first screening step for understanding sediment quality from Rio Grande reservoir by comparing metal content using three different sediment quality guidelines. We also aimed at verifying any possible spatial heterogeneity. Results and discussion  We found spatial heterogeneity varying according to the specific metal. Results showed a tendency for metals to remain as insoluble as metal sulfide (potentially not bioavailable), since sulfide was in excess and sediment physical–chemical characteristics contribute to sulfide maintenance (low redox potential, neutral pH, low dissolved oxygen, and high organic matter content). On the other hand, metal concentrations were much higher than suggested by Canadian guidelines and regional background values, especially Cu, which raises the risk of metal remobilization in cases of water circulation. Further study steps include the temporal evaluation of AVS/SEM, a battery of bioassays and the characterization of organic compounds.     

Retranslocation,Plant, and Soil Recovery of Nitrogen‐15 Applied to Bareroot Black Walnut Seedlings

Although retranslocation or nitrogen (N) derived from plants (NDFP) may account for more than 50% of the annual N demand in new growth of conifer seedlings, the proportional contribution of NDFP vs. current uptake or N derived from fertilizer (NDFF) in new growth of hardwood seedlings is relatively unknown. The current uptake was labeled with ammonium sulfate [(¹⁵NH₄)₂SO₄] at the rate of 1.56 g N plant^?1 and reared for 90 days in sand culture under greenhouse conditions, and NDFP vs. NDFF was quantified in new growth of half‐sib bareroot black walnut (Juglans nigra L.) seedlings. Nitrogen derived from plants accounted for 68 to 83% of the total N demand in new shoot growth of black walnut seedlings vs. NDFF (17 to 32%). Recovered applied fertilizer was 43% in soil and 9% in plants. The greater proportion of NDFP in new growth demonstrates the importance of retranslocation in meeting early N demand of transplanted black walnut seedlings.     

From soil to rice – a typical study of transfer and bioaccumulation of heavy metals in China

For the purpose of studying the contamination, bioaccumulation and transfer of heavy metals and understanding the effects of soil properties on these, the work was carried out on a regional scale. A total of 30 sets of soil and pairing rice tissues samples (root, straw and grain) were collected in Xiangzhou of Guangxi, China; soil properties and Cd, Cu, Pb and Zn of different rice tissues were analyzed. The mobility and bioaccumulation of Cd, Cu, Pb and Zn were assessed by transfer coefficients and bioaccumulation factors of them. The results indicated that the excess proportions of Cd and Pb were 50%, 3.33% and 30%, 6.67% in soil and rice grain, respectively, according to Chinese maximum permitted concentrations of heavy metals. Cd and Zn showed stronger bioaccumulation and mobility capability; the bioaccumulation and transfer of Cu were slightly lower than Cd and Zn; Pb had the weakest mobility. The bioaccumulation and mobility of heavy metals from soil to rice were restrained by soil pH, CaO, SOC, Fe oxides and Mn.     

Arsenic and metals mobility in soils impacted by tailings at Zimapán,México

Purpose

Mining wastes may cause important environmental impacts in soil, water, and air due to their high metals and arsenic contents. The aim of this work was the assessment of the mobility of arsenic and several heavy metals in soils located near different types of tailing heaps in the town of Zimapán, México.

Materials and methods

One hundred twenty soil samples were collected nearby to three tailing heaps, one oxidized presenting a red color (RT), and two with gray wastes (OSM and NSM) but with different age, during the dry and rainy seasons at the surface and to 40 cm depth, as well as to different distances from the deposits. Arsenic, Cd, Cu, Fe, Mn, Pb, V, and Zn total concentrations were determined; in addition, geochemical phase distribution of As, Cu, Mn, and Zn in selected samples was determined by sequential extraction. Concentrations were measured by graphite furnace atomic absorption spectrometry and inductively coupled plasma. To interpret the results, statistical analyses were performed.

Results and discussion

All samples presented high As concentrations reaching more than 50,000 mg kg^?1 close to OSM tailings, although the highest concentrations in the available fractions were measured in NSM impacted soils. Arsenic and metals concentrations exceeded the screening limits recommended for industrial sites. In samples influenced by OSM tailings, most of the elements analyzed were in the residual fraction, whereas in NSM and RT they were mostly in the organic and sulfide fractions and in the Fe and Mn oxides fractions, respectively. Larger concentrations of As and metals than those allowed by the screening values in Canada and the Netherlands were measured in the residential area representing a health threat for the inhabitants and the environment.

Conclusions

Acid mine drainage, water, and wind erosion of tailings have polluted nearby soils. Higher concentrations of As and metals were measured during the rainy season in gray tailings impacted soils and during the dry season in red tailings, showing both deposit types’ different mobility. Elements fractionation in soils depends mainly on tailings characteristics. Low metals and As proportions were found in the fraction with the highest mobility. Metals and arsenic are more stable in soils impacted by gray tailings, mainly in the organic and sulfides and residual fractions, while in RT, most are linked to Fe and Mn oxyhydroxides. Polluted soils in residential areas constitute a health hazard. Remedial actions must be taken to stop the population exposure.

     

Response of Cotton to Irrigation Methods and Nitrogen Fertilization: Yield Components,Water‐Use Efficiency,Nitrogen Uptake,and Recovery

Efficient crop use of nitrogen (N) fertilizer is critical from economic and environmental viewpoints, especially under irrigated conditions. Cotton yield parameters, fiber quality, water‐ and N‐use efficiency responses to N, and irrigation methods in northern Syria were evaluated. Field trials were conducted for two growing seasons on a Chromoxerertic Rhodoxeralf. Treatments consisted of drip fertigation, furrow irrigation, and five different rates of N fertilizer (50, 100, 150, 200, and 250 kg N /ha). Cotton was irrigated when soil moisture in the specified active root depth was 80% of the field capacity as indicated by the neutron probe.

Seed cotton yield was higher than the national average (3,928 kg/ha) by at least 12% as compared to all treatments. Lint properties were not negatively affected by the irrigation method or N rates. Water savings under drip fertigation ranged between 25 and 50% of irrigation water relative to furrow irrigation. Crop water‐use efficiencies of the drip‐fertigated treatments were in most cases 100% higher than those of the corresponding furrow‐irrigated treatments. The highest water demand was during the fruit‐setting growth stage. It was also concluded that under drip fertigation, 100–150 N kg/ha was adequate and comparable with the highest N rates tested under furrow irrigation regarding lint yield, N uptake, and recovery. Based on cotton seed yield and weight of stems, the overall amount of N removed from the field for the drip‐fertigated treatments ranged between 101 and 118kg and 116 and 188 N/ha for 2001 and 2002, respectively. The N removal ranged between 94 and 113 and 111 and 144 kg N/ha for the furrow‐irrigated treatments for 2001 and 2002, respectively.     

Contamination by PAHs,PCBs, PCPs and heavy metals in the mecoácfin lake estuarine water and sediments after oil spilling

Intention, Goal, Scope, Background  Environmental pollution caused by oil spills is a major ecological problem. Oil contamination in the environment is primarily evaluated by measuring the chemical concentrations of hydrocarbons. The results of chemical analyses are important for estimating water and sediment quality in the risk assessment to the flora and fauna of oil-contaminated sites. In the world there are lake ecosystems under permanent chemical stress due to urbanization and the oil industry. Studies, however, have been generally limited to petroleum compounds and have not considered other pollutants of the site like PCBs, polychlorinated pesticides and heavy metals. Objective  Water and sediment from stations in the Mecoacán Lake in the Mexican State of Tabasco were analyzed for polycy-clic aromatic compounds (PAHs), aliphatic hydrocarbons (AHs), polychlorinated biphenyls (PCBs), polychlorinated pesticides (PCPs) and heavy metals. The objective of this study was to examine the contaminant levels of the samples collected in February 1993 and 1996 after oil spills at the Mecoacán petroleum region. The goals of this study were to reveal the effect of the spills on the distribution of the hydrocarbons and assess the toxi-cological significance of the levels found. In addition, our aim was to examine the distribution of the PAHs in sediments from Mecoacán originated from both pyrolytic and petrogenic sources. Methods  Samples were collected from 19 stations and prepared according to the CARIPOL (Caribbean Pollution) methodology of the United Nations Environmental Programme (1992) of the Great Caribbean Region for hydrocarbons in marine and coastal water, and sediments. The gas-chromatographic and atomic absorption analysis of the samples was performed after sampling. Results and Discussion  Concentrations of PAHs in water ranged from 0.2 to 0.8 μg/l in 1993 and from 0.3 to 2.8 μg/l in 1996. The concentration of the 16 EPA-PAHs varied from 0.1 to 36 mg/kg dry weight in the lake sediment samples collected in 1996, while those of AHs, PCBs and PCPs ranged from 0.1 to 67 mg/kg, 0.1 to 59 μg/kg and 6 to 370 μg/kg, respectively. The most abundant contaminants in water were benz[a]anthracene and pyrene, in 1993 and 1996, respectively; while in sediments collected in 1996: Pyrene, C₂₄, 2-chlorobiphenyl and endrin predominated. Heavy metals (Cu, Pb and Zn) were found at low concentrations. Benzo[a]pyrene was detected in some sediment samples in varying amounts (0.2 to 0.3 mg/kg). Conclusions  The maximum total PAH concentration in sediments was found at sites near the oil fields and the AH concentration near the urban zone. The mayor pollutants in sediments were PAHs and AHs, and taking into regard the detected PAHs near the oil fields, the source was the oil spilling. The mean total PAH value in Mecoacan sediments of 6.4 mg/kg did not exceed the median range effects value (ERM) for total PAHs of 44.8 mg/kg. The measured organochlorine compounds and heavy metals were present in amounts much inferior to the ERM values. This study confirms that contaminants concentration in sediments did not exceed the environmental quality guideline for the 50% probability and no adverse effect can be expected. Recommendation and Outlook  Analysis revealed no indication of a contribution of PAHs, PCBs, PCPs and heavy metals to acute sediment toxicity. The results of this study demonstrate the importance of continuous monitoring of ecosystems exposed to pollution to make pre-spill data available in order to evaluate the real consequence of the spilling and its effect on flora and fauna.     

Recovery of nitrate‐N in dry soil and plant samples by the standard,unmodified Kjeldahl procedure

Abstract

In the literature, various modifications of the standard Kjeldahl procedure for the determination of total nitrogen are used to include nitrate‐N in soil and plant samples. This study suggests that these modifications, which are usually time consuming and tedious, are not necessary in the case of dry soil samples. However, if total‐N (including nitrate‐N) is to be measured in dry plant samples then the use of one of the modifications is essential.     

Preface—Biochar and agricultural sustainability

Journal of Soils and Sediments -     

Heavy metals in the soil–plant system of the Don River estuarine region and the Taganrog Bay coast

Purpose

The aim of this work was to study the level and degree of mobility of heavy metals in the soil–plant system and to perform bioindication observations in the Don River estuarine region and the Russian sector of the Taganrog Bay coast.

Materials and methods

The objects of the study included samples of zonal soils (chernozem) and intrazonal soils (alluvial meadow and alluvial-stratified soils, Solonchak, sandy primitive soil) from monitoring stations of the Don river estuarine region and the Taganrog Bay coast, as well as their higher plants: Phragmites australis Cav., Typha angustifolia L., Carex riparia Curtis, Cichorium intybus L., Bolboschoenus maritimus L. Palla, and Rumex confertus Willd. The total concentrations of Mn, Ni, Cd, Cu, Zn, Pb, and Cr in the soils were determined by X-ray fluorescent scanning spectrometer. The concentration of heavy metal mobile forms exchangeable, complex compounds, and acid-soluble metal were extracted using the following reagents: 1 N NH₄Ac, pH 4.8; 1 % EDTA in NH₄Ac, pH 4.8; 1 N HCl, respectively. Heavy metals in plants were prepared for analysis by dry combustion at 450 °C. The heavy metal concentration in extracts from plants and soils was determined by AAS.

Results and discussion

The total contents of heavy metals in the soil may be described with a successively decreasing series: Mn?>?Cr?>?Zn?>?Ni?>?Cu?>?Pb?>?As?>?Cd. The total concentrations of As, Cd, and Zn in the soil exceed the maximum permissible concentrations levels. Contamination of alluvial soils in the estuarine zone with mobile Сu, Zn, Pb, and Cd has been revealed, which is confirmed by the high bioavailability of Cu and Zn and, to a lesser degree, Cd and Pb accumulating in the tissues of macrophytic plants. Data on the translocation of elements to plant organs have showed their predominant accumulation in the roots. Bioindication by the morphofunctional parameters of macrophytic plants (with a Typha L. species as an example) can be used for revealing the existence of impact zones with elevated contents of metals in aquatic ecosystems.

Conclusions

The results revealed that increased content of Zn, Pb, Cu, Ni, and As in soil have anthropogenic sources. The high content of Cr in the soils is related to the lithogenic factor and, hence, has a natural source.

     

Assessment of loose and adhered urban street sediments and trace metals: a study in the city of Poços de Caldas,Brazil

Purpose

This study aims to quantify and characterise sediments accumulated in the street gutters in an urban area of Poços de Caldas, Brazil. The main research questions are: What type of urban areas, e.g. those under construction, produce most sediments and what are the main characteristics of such sediments? What differences, e.g. granulometry, can be found in loose and adhered sediments? What trace metals can be found in the sediments?

Materials and methods

Fieldwork was carried out in a residential area of Poços de Caldas, Brazil. Ten samplings were conducted between May and August 2013 to collect sediments from road gutters. The collected sediments were then divided into ‘loose’ and ‘adhered’, depending on whether they were collected in a first, gentle, sweeping with soft bristled brush or in a subsequent sweeping with a stiff bristled brush. Granulometric curves were drawn for both types of sediments. Fine sediment analyses (≤63 μm) were performed on samples from the last five samplings. Two techniques were used to look for trace elements: energy dispersive X-ray fluorescence (EDXRF) and inductively coupled plasma-atomic emission spectrometry (ICP-AES).

Results and discussion

Larger amounts of sediments were collected after lower intensity rainfall events. Higher intensity events seemed to wash the sediments away. A correlation was found between areas under construction and sediment mass production. A characteristic range of granulometries (medium sand), found in our study is in accordance with studies by other authors. An important presence of heavy metals (Cr, Cd, Pb, Zn, Ni and Cu) was detected and characterised. As and Sn were also detected even though they are not often mentioned in the literature on urban soil pollutants.

Conclusions

Areas under construction were found to produce more sediments than other areas. The trace metals found in highest concentrations were Pb and As. The heavy metal concentration decreases after wet periods, showing that they are carried by runoff. It is expected that this study may serve as an input for establishing diffuse pollution control and mitigation strategies for the accumulation of pollutants in the urban environment.

     

Are cadmium, lead and mercury concentrations in mosses across Europe primarily determined by atmospheric deposition of these metals?

Purpose

This study aimed at investigating correlations between heavy metal concentrations in mosses and modelled deposition values as well as other site-specific and regional characteristics to determine which factors primarily affect cadmium, lead and mercury concentrations in mosses. The resulting relationships could potentially be used to enhance the spatial resolution of heavy metal deposition maps across Europe.

Materials and methods

Modelled heavy metal deposition data and data on the concentration of heavy metals in naturally growing mosses were integrated into a geographic information system and analysed by means of bivariate rank correlation analysis and multivariate decision trees. Modelled deposition data were validated annually with deposition measurements at up to 63 EMEP measurement stations within the European Monitoring and Evaluation Programme (EMEP), and mosses were collected at up to 7,000 sites at 5-year intervals between 1990 and 2005.

Results and discussion

Moderate to high correlations were found between cadmium and lead concentrations in mosses and modelled atmospheric deposition of these metals: Spearman rank correlation coefficients were between 0.62 and 0.67, and 0.67 and 0.73 for cadmium and lead, respectively (p?<?0.001). Multivariate decision tree analyses showed that cadmium and lead concentrations in mosses were primarily determined by the atmospheric deposition of these metals, followed by emissions of the metals. Low to very low correlations were observed between mercury concentrations in mosses and modelled atmospheric deposition of mercury. According to the multivariate analyses, spatial variations of the mercury concentration in mosses was primarily associated with the sampled moss species and not with the modelled deposition, but regional differences in the atmospheric chemistry of mercury and corresponding interactions with the moss may also be involved.

Conclusions

At least for cadmium and lead, concentrations in mosses are a valuable tool in determining and mapping the spatial variation in atmospheric deposition across Europe at a high spatial resolution. For mercury, more studies are needed to elucidate interactions of different chemical species with the moss.