Changes In Heavy Metal Concentrations Research Articles

Changes of heavy metal concentrations in farmland soils affected by non-ferrous metal smelting in China: A meta-analysis

Long-term human smelting activities have resulted in substantial heavy metals (HMs) pollution of farmland soils around smelting sites, and the safety of farmland products is critical for human health. The current study focuses on HMs in farmland soils surrounding a single smelter, therefore the impact of smelting on a national scale needs to be investigated further. This study was based on 116 papers and 1143 sets of relevant data for meta-analysis, and a hierarchical mixed-effects model was used to quantify the changes of HMs concentrations in farmland soils affected by non-ferrous metal smelting on a national scale, as well as their relationships with relevant explanatory variables in China. Results showed that: (i) non-ferrous metal smelting substantially increased farmland soils HMs concentrations (323%), with each HM concentration increasing in the following order: Cd (2753%) > Pb (562%) > Hg (455%) > Zn (228%) > Cu (158%) > As (107%) > Ni (52%); (ii) the highest increase of HMs in vegetable fields (361%), but not significant in comparison to other farmland categories, and the increase of Pb, Zn, Cu and As concentrations were significantly different in different types of smelting areas; (iii) the increase of Hg was significantly higher in the northern region than in the southern region, and the opposite increase of Cu; (iv) the soil depth from 0 to 40 cm was significantly affected by smelting, and the increase of multiple HMs were significantly positively correlated with soil pH and negatively correlated with distance; (v) the other explanatory variables (farmland category and soil organic matter) were not significantly related to the effect of smelting. The results can provide some reference for protecting and restoring farmland soils around smelting areas.

Pollution Characterization, Source Identification, and Health Risks of Atmospheric Particle-Bound Heavy Metals in PM2.5 in Zhengzhou City: Based on High-resolution Data

In order to study the pollution characteristics and sources of heavy metals in urban atmospheric PM2.5, 21 elements in atmospheric PM2.5 in Zhengzhou City were detected using an online metal analyzer during July and October 2017 and January and April 2018, and the changes in heavy metal concentrations were analyzed. Heavy metals were traced by enrichment factors, principal component analysis, and potential source function. The US EPA risk assessment model was used to assess their health risks. The results showed that:the concentrations of K, Zn, Mn, Pb, Cu, As, Cr, and Se increased with the increase in pollution level. The results of enrichment factors and principal component analysis showed that the main sources of heavy metals were crust, mixed combustion, industry, and motor vehicles. The characteristic radar charts showed that the pollution dominated by crustal sources mainly occurred in spring and winter, whereas the pollution dominated by mixed combustion sources mainly occurred in winter. Pb, As, and Ni were greatly affected by the transport of a fen nutrient-laden plain, Beijing-Tianjin-Hebei, and southern Henan, whereas Cd was greatly affected by the northwest region of the sampling site. As presented a significant carcinogenic risk in both adults and children, whereas Pb and Sb presented a significant non-carcinogenic risk in children.

A survey on heavy metal concentrations in residential neighborhoods: The influence of secondary water supply systems

Water quality deterioration often occurs in secondary water supply systems (SWSSs), and increased heavy metal concentrations can be a serious problem. In this survey, twelve residential neighborhoods were selected to investigate the influence of SWSSs on the seasonal changes in heavy metal concentrations from input water to tank and tap water. The concentrations of nine evaluated heavy metals in all groups of water samples were found to be far below the specified standard levels in China. The concentrations of Fe, Mn, and Zn increased significantly from the input water samples to the tank and tap water samples in spring and summer (p < 0.05), especially for the water samples that had been stagnant for a long time. Negative correlations were found between most of the heavy metals and residual chlorine (Fe, Cu, Zn, and As, r = -0.186 to -0.519, p < 0.05). In particular, a high negative correlation was observed between Fe and residual chlorine (r = -0.489 to -0.519, p < 0.01) in spring and summer. Fe and Mn displayed positive correlations with turbidity (r = 0.672 and 0.328, respectively; p < 0.05). In addition, Cr and As were found to be positively associated with some nutrients (NO3−, TN, and SO42−; r = 0.420-0.786, p < 0.01). The material of the storage tanks had little influence on the difference in heavy metal concentrations. Overall, this survey illustrated that SWSSs may pose a chronic threat to water quality and could provide useful information for practitioners.

Changes in heavy metal concentrations in the sediments of the Gulf of Finland over two decades

Changes in heavy metal concentrations in the sediments of the Gulf of Finland over two decades

Downstream Changes in Heavy Metal Concentrations and Pollution Indices of Bed Sediments in Khamsan Representative Watershed

Downstream Changes in Heavy Metal Concentrations and Pollution Indices of Bed Sediments in Khamsan Representative Watershed

The potential of using Cedrus atlantica as a biomonitor in the concentrations of Cr and Mn.

Air pollution is becoming increasingly dangerous which is quite a significant issue of today's world, especially air pollution from heavy metal, whose emission increases with industrial and traffic activities. This is of great importance in terms of environmental pollution and human health. Heavy metals do not deteriorate and disappear easily on earth. They are liable to bioaccumulate within cells in organisms. Most of them demonstrate harmful effects in addition as a result of advanced accumulation, and thus they emerge as toxic and carcinogenic. Therefore, it is of great importance to observe the changes in heavy metal concentrations in the air. One of the most effective techniques for monitoring the change of heavy metal concentrations in the atmosphere is the use of annual rings of trees as biomonitors. In this study, in the annual rings of the Cedrus atlantica Manettitree cut at the Kastamonu province at the end of 2019, the variation of the concentrations of some of the heavy metals most associated with traffic density was tried to be determined. Within the scope of the study, Cr and Mn concentration in the outer bark and the inner bark was compared with the direction and wood for the variation of heavy metal concentrations. Also, variance analysis and Duncan test were applied and evaluated. As a result of the study, while the highest values in many heavy metals are generally obtained in the outer bark, the transfer of metals in the wood is limited, and some heavy metal concentrations change significantly depending on the direction, especially in the wood. This change is related to the traffic density, so Cedrus atlantica Manettiannual rings are very suitable as biomonitors for air pollution control.

The usability of Cupressus arizonica annual rings in monitoring the changes in heavy metal concentration in air.

Air pollution, which has been increasing in recent years, has reached significant dimensions and has become one of the most important agenda topics of present day. Among air pollution components, heavy metals are of particular importance, since they are not easily decomposed, they tend to bioaccumulate, and some of them have toxic or carcinogenic effects even at low concentrations. Therefore, it is an extremely important subject to monitor the changes in heavy metal concentrations found in air. The most preferred method in determining the changes in heavy metal concentrations in the atmosphere is the use of biomonitors. From past to present, trees have been good biomonitors in determining the increase in heavy metal concentrations in the atmosphere. Particularly, with the help of the annual growth rings of trees, vital information can be obtained on the changes in heavy metal concentrations in air. In this study, after the annual rings were determined on the log taken from the main body of the cypress (Cupressus arizonica) tree cut from the Kisla park located in Kastamonu province, the concentrations of Bi, Cd, and Ni in the outer bark, inner bark, and wood were compared in the inward-facing and road-facing parts of these sections. Also, the changes in heavy metal concentrations in the annual rings were evaluated on a yearly basis. As a result of the study, it was found that the element concentrations in the outer bark of the road-facing part were generally at a higher level, and that the changes in the elements on a yearly basis generally followed a fluctuating course, but there had been a general increase in the Cd and Ni concentrations in recent years.

The investigation of bioremediation potential of Bacillus subtilis and B. thuringiensis isolates under controlled conditions in freshwater.

Bioremediation is widely used to remove water pollution as environmentally friendly smart solutions. In this study, Bacillus isolates were investigated in terms of the effectiveness of single and multiple cultures in eliminating aquatic pollution related to aquaculture activities. In the established experimental setups, the environments where Bacillus isolates were inoculated with single and multiple cultures at 1 × 107CFU/mL were evaluated comparatively with control groups without these isolates, and total aerobic mesophilic bacterial counts were performed in the petri dish by inoculation method. At the end of the 6 days of the experiment, in the environment in which single and multiple cultures of Bacillus isolates were presented with 17-20 ± 0.05°C temperature and 5.1-8.1 pH 2-4.6mg/l dissolved oxygen values (O2), 2% increase in total phosphorus (TP) value was observed. On the other hand, 4% removal of Ammonia-nitrogen (NH3-N), 80% removal of Nitrite-nitrogen (NO2-N), and 100% removal of Nitrate-nitrogen (NO3-N) were observed. In the changes in heavy metal concentrations, the removal of Ni, Cr, Se, Al, Cd, Mn, Fe, and B was observed from highest to lowest as 57%, 50%, 50%, 43%, 40%, 23%, 5%, and 2%, respectively. It also has been seen that B. thuringiensis isolate was observed to be more effective than B. subtilis in metal removal.

Changes of heavy metal concentrations in Shitalakhya river water of Bangladesh with seasons

Heavy metal concentrations in water and fish of the Shitalakhya river was measured to find out the suitability of its water for drinking and irrigation purposes. The concentrations of Pb, Cu, Cr, Zn, Cd and Hg in water were 0.0065; 0.0240; 0.0069; 0.8170; 0.0044; and 0.0057 mg/L, respectively in pre-monsoon, 0.0029; 0.0151; 0.0019; 0.4270; 0.0015; and 0.0020 mg/L, respectively in monsoon, and 0.0040; 0.0212; 0.0039; 0.6520; 0.0029; and 0.0031 mg/L, respectively in post-monsoon season. The heavy metal concentrations were found higher in pre-monsoon followed by post-monsoon and monsoon. The results also depicted that over the three seasons heavy metal pollution index and heavy metal evaluation index for all metals were lower than the critical pollution index value and low heavy metal contamination, respectively, and the degree of contamination in pre-monsoon season stated medium level pollution, followed by post-monsoon and monsoon season. The concentrations of Pb, Cu, and Cr in fish were found less than the lower detection limit, while the Zn were found 25.42; 18.30; and 29.34 mg/kg during the pre-monsoon, monsoon and post-monsoon, respectively. The study concluded that the Shitalakhya river water was not safe for the aquatic environment, especially for aquatic biota.

Effects of Atmospheric Precipitation on Heavy Metal Accumulation and Deactivation Amendment in Wheat Around a Lead Smelter

The effects of atmospheric precipitation on heavy metal accumulation and deactivation amendment in wheat surrounding a lead smelter were studied. The total precipitation amounts of Cd, Pb, and As in an in situ test were noticeably more than their amounts in an off-site test over the entire growing period of wheat. In the same soil-wheat system, the heavy metal concentrations of wheat leaves in the off-site test were significantly lower than those in the in situ test near the lead smelter. Specifically, Cd, Pb, and As were 53.1%, 89.2%, and 85.7% less, without the amendment of the heavy metal deactivator (HMD). Meanwhile, the deactivation effect improved in the off-site test, resulting in the respective Cd, Pb, and As decreases of 6.0%, 46.3%, and 22.1% more, compared with it in the in situ test. The changes in heavy metal concentrations of wheat grains were consistent with those of wheat leaves. The concentrations of Cd and Pb in the off-site test were 10.7% and 91.0% lower than the in situ values, without the amendment of the HMD, and deactivation effect also had enhanced, with Cd and Pb decreasing by 1.3% and 9.6% more. The heavy metal concentrations of wheat leaves in the indoor pot test were significantly lower than those in the in situ test, with Cd, Pb, and As 74.4%–87.3%, 95.6%–97.0%, and 86.2%–87.4% less, respectively. After repeated leaf-washing treatment, the effect of HMD amendment was further enhanced, with Cd, Pb, and As decreasing by 30.8%, 33.6%, and 34.7%, respectively. All tests conducted indicate atmospheric precipitation is the controlling pollution source. Deactivation amendment can reduce the heavy metal concentrations of wheat leaves and grains, even in the presence of precipitation contamination, although the presence of precipitation reduces the effect of HMD amendment. Repeated leaf-washing can enhance the effect of HMD amendment and decrease the accumulation of heavy metals from atmospheric precipitation in wheat.

Spatio-temporal variability and pollution sources identification of the surface sediments of Shatt Al-Arab River, Southern Iraq

Water draining from heavily industrialized basins introduces significant amounts of pollutants to the rivers water and sediments. Heavy industrial activities in the Shatt Al-Arab basin result in increased pollutant loads to the river’s surface sediments. Therefore, it becomes crucial to investigate the influence of anthropogenic activities on both spatial and temporal scales. This study unfolded the extent, sources, and distributions of heavy metals pollution in the sediments of the Shatt Al-Arab River. Extensive samplings were performed during the dry and the wet seasons at 25 stations along the river course for the analysis of 11 heavy metals. The analysis revealed high pollution levels in the river sediments compared to both their historical values and international standards. Statistical analysis techniques such as Principal Component Analysis (PCA) and Factor Analysis (FA) were applied. Statistical analysis showed that all the elements were well represented by four varifactors that explained a cumulative total variance of 74%. PCA/FA indicated that most investigated metals were of anthropogenic origins (i.e., industrial, residential, and agricultural sources). Pollution indices that were applied, such as Contamination Factor (CF) and Nemerow Pollution index (PN), indicated that sediments were: (i) considerably contaminated with Fe and Mo (ii) moderately contaminated with Cr, Zn, Ni, Cu, Pb and Mn and (iii) not contaminated with Co and V. The PN values indicated serious pollution in the river sediments in all sites, even though the pollution was not evenly distributed, i.e., the upstream reaches of the river were more polluted compared to the downstream parts. In contrast to many studies that have reported changes in heavy metals concentrations due to seasonal variations, our data showed no significant relationship between metals concentrations and seasonality. This study addresses several of the major limitations of the current knowledge on this river’s pollution sources and analysis, such as the limited number of analyzed pollutants and restricted samplings in the current literature. The findings necessitate the implementation of effective management strategies to control pollution in the river basin.

Analyzing of usability of tree-rings as biomonitors for monitoring heavy metal accumulation in the atmosphere in urban area: a case study of cedar tree (Cedrus sp.).

It is important to monitor the heavy metal pollution in order to identify risk zones and to determine the change in the heavy metal concentration of the atmosphere within the process. For this, it is necessary to carry out measurements for many years; however, this is not possible. Especially from past to present, one of the most effective methods to determine the changes of heavy metal concentrations in the atmosphere is to use the annual tree rings as biomonitors. Perennial plants growing in our country create annual rings, and it is possible to gain information regarding the changes of heavy metal concentrations in that region by determining the heavy metal concentrations in these rings. In this study, it was aimed to determine the annual changes of Pb, Co, and Fe elements' concentrations in these sections by determining the annual rings on the logs taken from the main stem of the cedar tree (Cedrus sp.), which was cut by the end of 2016, in December, 2016, in Kastamonu province. Within the scope of the study, the element concentrations were also determined in the inner and outer bark. As a result of the study, it was found that the heavy metal values in the organelles taken from the road-facing part, especially the heavy metal concentrations in the outer bark were higher than the metal concentrations in the inward-facing part, and that the concentrations changed significantly on organelle and year basis.

Heavy metal accumulation and mobility in a soil profile depend on the organic waste type applied

While organic waste amendments can initially improve soil physicochemical properties, including nutritional benefits to plants and increased microorganism activity, long-term application of excessive amounts of organic wastes can cause accumulation of heavy metals (HMs). Thus, the current study examined the accumulation of HMs in agricultural soil profiles following organic waste application. Three common organic sludge, including municipal sewage sludge (MSS), industrial sewage sludge (ISS), and leather sludge (LS), were applied annually to an agricultural soil under field conditions over 7 years (1994–2000) at a rate of 25 and 50 t ha−1 year−1. Subsequently, when organic sludge amendments were ceased, the experimental plots were cultivated without any treatments for another 12 years (2001–2012) and the changes in HM concentrations along the soil depth profile were monitored together with soil pH, dissolved organic carbon (DOC), and dehydrogenase activity (DHA). Significant increases in Cu, Pb, and Zn concentrations were observed down to a depth of 80 cm in soils treated with ISS and LS, where sludge application also increased the levels of Cd, Cr, Pb, and Zn and their movement down the soil profile. However, with the exception of Cu, no significant changes in HM concentrations were observed following treatment with MSS. At a depth of 80 cm, soils which had received 25 and 50 t ha−1 LS showed, respectively, 4 and 14 times higher Cr levels than the control soil. Organic sludge induced changes in soil pH and soil DOC concentration which were the key factors influencing HM movement and accumulation following organic sludge treatment.

The effect of heavy metal pollution on foraminifera in the Western Marmara Sea (Turkey)

The aim of this study was to investigate the effects of heavy metals on foraminiferal assemblages in Holocene sediments in the western Marmara Sea. Accordingly, four drilling samples, one in Bandırma (Balıkesir/Turkey), two in Erdek Bay (Erdek-Bandırma/Turkey) and one in Tekirdağ (Turkey). Samples of cores taken from 43 different locations in the western Marmara Sea also have been examined. Changes in heavy metal concentrations were determined (spatially) in the vertical direction by means of drilling samples in the vertical direction for geochronology and in the horizontal direction by the areal distribution of the core samples, and foraminiferal assemblages were identified. In order to summarize the results of geochemical analyses, an average value defined as Pollution Index (PI) was used for the first time in this study. In this method, the pollution index value is obtained by dividing the sum of average value ratios of heavy metal measurement values by the number of measurements. The obtained index value was correlated separately with the numbers of foraminifer individuals and species. It was observed that the number of individuals and species decreased where the heavy metal measured values (MV) were higher than the pollution index and increased where the heavy metal values were lower than the pollution index. It was also observed that foraminifera were completely absent in some locations where PI was less than MV. Morphological changes were observed in Elphidium crispum, Massilina secans, and Ammonia compacta foraminifer species in the core samples taken in areas where industrial wastes are discharged into the southern parts of the Marmara Sea. No foraminifer species were observed at some locations where the heavy metal density was high (between Misakça-Denizkent, and Erdek-Balikesir). The pollution index (PI) value measured in this area was higher than the critical value, indicating that heavy metal concentrations affect the habitats of foraminifera.

Modelling cadmium contamination in paddy soils under long-term remediation measures: Model development and stochastic simulations

A pollutant accumulation model (PAM) based on the mass balance theory was developed to simulate long-term changes of heavy metal concentrations in soil. When combined with Monte Carlo simulation, the model can predict the probability distributions of heavy metals in a soil–water–plant system with fluctuating environmental parameters and inputs from multiple pathways. The model was used for evaluating different remediation measures to deal with Cd contamination of paddy soils in Youxian county (Hunan province), China, under five scenarios, namely the default scenario (A), not returning paddy straw to the soil (B), reducing the deposition of Cd (C), liming (D), and integrating several remediation measures (E). The model predicted that the Cd contents of soil can lowered significantly by (B) and those of the plants by (D). However, in the long run, (D) will increase soil Cd. The concentrations of Cd in both soils and rice grains can be effectively reduced by (E), although it will take decades of effort. The history of Cd pollution and the major causes of Cd accumulation in soil were studied by means of sensitivity analysis and retrospective simulation.

Using Heavy Metal Content and Lipid Peroxidation Indicators in the Tissues of the Mussel Crenomytilus grayanus for Pollution Assessment After Marine Environmental Remediation.

We examined the effects of environmental remediation on the heavy metal concentration and lipid peroxidation activity in the digestive gland and gills of the marine mussel Crenomytilus grayanus. Changes in heavy metal concentrations and lipid peroxidation biomarkers in the tissues of mussels collected at a contaminated site were compared with those obtained from a reference site. Prior to remediation the concentration of Pb, Cu, Cd, Fe and Zn and the levels of malondialdehyde, conjugated dienes and lipofuscin in mussels collected from the contaminated site were significantly increased compared with those obtained from the reference site. Three years after remediation, these parameters did not significantly exceed the reference site parameters, except Pb, whose concentration, though markedly decreased, yet was much higher than in tissues of mussels from the reference site.

Effects of a small-scale, abandoned gold mine on the geochemistry of fine stream-bed and floodplain sediments in the Horsefly River watershed, British Columbia, Canada

Mining is known to be a major source of metal contamination for fluvial systems worldwide. Monitoring and understanding the effects on downstream water and sediment quality is essential for its management and to mitigate against detrimental environmental impacts. This study aimed to examine the effects of the small-scale, abandoned, hydraulic Black Creek gold mine on the geochemical content of fine (&lt;63 μm) stream bed and floodplain sediment in the Horsefly watershed (British Columbia, Canada), which is a part of the Quesnel River basin. Concentrations of As, Cd, Se and Zn were determined byaqua regiadigestion and the modified BCR (European Community Bureau of Reference) sequential extraction procedure followed by inductively coupled plasma-optical emission spectroscopy or inductively coupled plasma-mass spectrometry. Age-depth models for the floodplain cores were constructed using excess Pb-210 and Cs-137 activity concentration profiles. The results show that the mine caused local As contamination of the Horsefly River floodplain sediment during the first years of operation, but at present the contamination is mainly contained in the Black Creek. Present-day and recent concentrations of Cd, Se and Zn in the Horsefly River are elevated and this is probably derived from other upstream mining activities. The spatial and temporal changes in heavymetal concentrations suggest a slight, but not particularly widespread, mining effect on the finesediment geochemistry in the Horsefly River system.

Bioleaching of heavy metals from contaminated alkaline sediment by auto- and heterotrophic bacteria in stirred tank reactor

Bioleaching Xiangjiang River alkaline sediment contaminated by multiple heavy metals was investigated. Multiple metals in alkaline sediment possess significant toxicity to aquatic organisms or humans and will greatly inhibit bioleaching. The bioleaching method using autotrophic bacteria mixed with heterotrophic bacteria can solve this problem successfully. The experiment results showed that bioleaching efficiencies of Zn, Mn, Cu, and Cd were 95.2 %, 94.2 %, 90.1 %, and 84.4 %, respectively. Moreover, the changes of heavy metal concentrations in different fractions in contaminated sediment before and after bioleaching were analyzed by selective sequential extraction, and it was discovered that the main fractions of Zn, Mn, Cu and Cd after bioleaching are Fe-Mn oxide, organic associated form and a residual form. Its biotoxicity decreased greatly. The bioleaching heavy metals from sediment using autotrophic bacteria combined with heterotrophic bacteria can effectively improve the bioleaching efficiency and reduce toxicity.

Effect of different soil layers on porewater to remediate acidic surface environment at a close mine site

This paper describes the chemistry of porewater when constructing different soil layers on acidic weathered rock of a closed mine to remediate the surface environment. Three cases were set on a flat surface of the site, all under different layer systems. Case 1 was only composed of weathered rocks. A top neutralization layer was constructed on the weathered rocks in case 2, whereas both an upper low-permeable and middle neutralization layers were constructed on the weathered rocks in case 3. The low-permeable layer of 30 cm thick consists of clay, and the neutralization layer of 30 cm thick consists of the mixture of the weathered rock and calcium carbonate as a neutralizer. Porewater sampling systems and soil sensors to measure temperature, water content, and electrical conductivity were set at different depths. In case 1, steadily high concentrations of heavy metals were observed regardless of the depth, and the pH ranged from 2 to 4. In cases 2 and 3, a dramatic decrease in concentrations of heavy metals was observed, even below the neutralization layer. For both cases, pH values were circumneutral. There were no significant seasonable changes in heavy metals concentrations and pH of porewater by considering the temperature and precipitation. In addition, the water content of the layers in case 3 fluctuated more mildly than that in cases 1 and 2, indicating that the low-permeable layer reduced the rate of infiltration. Therefore, a significant reduction in the load of heavy metals released from the site can be achieved by both implementing neutralization and low-permeable layers.

CHEMICAL ELEMENTS AND HEAVY METALS IN EUROPEAN LARCH TREE RINGS FROM REMOTE AND POLLUTED SITES IN THE EUROPEAN ALPS

LEONELLI G., BATTIPAGLIA G., CHERUBINI P., MORRA DI CELLA U. & PELFINI M., Chemical elements and heavy metals in European larch tree rings from remote and polluted sites in the European Alps. (IT ISSN 0391-9838, 2011). Air pollution dispersal in the European Alps has been studied both for glacial and forest environments. In this study, chemical elements and heavy metals in the tree rings were analyzed for seven sites of European larch (Larix decidua Mill.) in the Italian European Alps. At three sites in the proximities of the Mont Blanc Tunnel (MBT) entrance the analyses were performed at the yearly scale on the periods 1950-1970 (comprising the MBT opening in 1965) and 1985-2008 (comprising the 3-yr MBT clo- sure after the 1999 car accident) with the aim to check if trees recorded at the yearly scale variations in chemical elements and changes in heavy metals concentrations over time. At the regional scale, the analyses on heavy metals were conducted without annual resolution for most sites on the common periods 1950-1970 / 1985-1998 with the aim to detect possi- ble ongoing trends and differences between some Alpine sites. Chemical elements concentrations at Entreves (EN) sites varied significantly be- tween heartwood and sapwood with generally higher concentrations in sapwood. At EN sites no clear patterns were found for heavy metals be- fore and after the MBT opening and during its 3-yr closure. We found that the high site (ENH) was generally less polluted than the (ENC) and the far (ENF) sites. At site ENC we found higher values of Cr, Ni and Cu, whereas at site ENF we found higher values for all the other elements analyzed. The analysis of heavy metals at the regional scale revealed generally no significant temporal changes in concentrations except for Cr and Cu, showing higher values in the recent period. On comparing the heavy metals concentration between the seven sites, the Palud site showed almost always the highest concentrations, except for Ni and Cu that were higher in two remote sites close to glacial environ- ments in the Gressoney and Valtellina valleys. Dendrochemical analysis revealed that the temporal information in the tree rings is covered by too many signals and no environmental changes are recorded at the yearly scale by European larch. However tree rings may provide useful informa- tion on ongoing long-term trends and on the spatial definition of pollu- tant dispersal in the Alpine environment.