Soil Surface Geochemical Anomaly Around the Copper-Nickel Metallurgical Smelter

The soils were sampled from the center of airborne contamination caused by long time activity of a copper/nickel smelter complex in the Kola Peninsula, Russia. The soil specimens were taken from an area about 250 km², which included the town of Monchegorsk, with frequency of 1 sample (plot) per 3 km² and heavy metals nickel, copper, cobalt, chromium, lead, cadmium, strontium, iron, manganese and arsenic were measured. The soil surrounding the Smelter, including the inhabited territory of the town, was found to be contaminated by nickel and copper to levels 450- and 250 times higher in comparison to the background, respectively. These soils were found to be extremely toxic and represented a severe threat to human health. Elevated concentrations of iron and arsenic caused by smelter emissions were found too.     

Absorption of Heavy Metals in Wild Berries and Edible Mushrooms in an Area Affected by Smelter Emissions

The total concentrations of nickel, copper, chromium, strontium, arsenic, lead, cadmium and cobalt were measured in berries and mushrooms, as well as manganese and iron in mushrooms. The study area (about 3500 km²) is situated on the border of the northern taiga and tundra forests (68–69°N) and is affected by emissions from the extensive Ni-Cu smelter complex at Monchegorsk, Kola Peninsula, NW Russia. Part of the study area, extending along the railway line used for transporting apatite concentrate, contains elevated quantity of strontium. Berries of Vaccinium vitis-idaea (82 samples), Vaccinium myrtillus (28), Rubus chamaemorus (42) and Empetrum hermaphroditum (40) and mushrooms of Leccinum auantiacum (47 samples), Leccinum scabrum (32), Russula vesca (25), Lactarius torminosus (8), Lactarius trivialis (9), Suillus luteus (10) and Xerocomus subtomentosus (20 specimens) were collected from 98 locations during 1987–1992. The nickel and copper concentrations in the berries, and nickel in mushrooms, correlated satisfactorily with the corresponding metal concentrations in the soil. The berries and mushroons growing over an area of at least 3000 km² around the smelter complex are unsuitable for human consumption due to the elevated nickel concentrations caused by the smelter dust emissions. The berries and mushrooms gathered in the studied polluted forests were found to be contaminated by nickel by a factor of 15–30 times (berries) and 15–40 times (mushrooms) more than the background level. Increased levels of strontium were found close to the railway line. The concentrations of all the other metals in the studied area did not exceed sanitary standards.     

The origin and early genesis of clay bands in youthful sandy soils along lake Michigan,U.S.A.

A beach ridge and dune complex with good radiocarbon control sampling the last 3500 radiocarbon years B.P. provides new insights on the early genesis of clay bands in sandy soils. Soil profiles were sampled by age groups, described in the field, and then subjected to laboratory analyses for particle-size distribution, pH, organic carbon, carbonate minerals, and extractable iron and manganese. This study suggests that small increases in pH, brought about by small increases in carbonate content within the soil profile, are responsible for flocculating small amounts of illuviated clay. This process, along with a transition to a greater hydraulic conductivity with soil depth due to coarser textures in any given profile, partly explains the existence and possible reason for the initiation of illuvial zones and eventually for clay-band horizons. A pronounced increase in the thickness of incipient clay-band horizons in soils older than 2300 years appears due to finer textures in the parent materials than are present in younger soils. Because of slightly reduced porosity and lower permeability, carbonates and a high pH are retained in both illuvial and eluvial horizons of some of these older soils. In addition, only in those profiles older than 2300 years do clay and iron oxide concentrations coincide and is there some suggestion of greater amounts of extractable manganese in horizons of minimum iron and clay. A pronounced segregation of clay-iron bands is not apparent at the study area but should occur in future years as additional amounts of iron and clay are deposited.     

Response of spodic B horizons to acid precipitation in northernmost Fennoscandia

In northernmost Fennoscandia there is concern about the possible environmental effects of the sulphur emissions from Russian nickel smelters on the Kola Peninsula. The purpose of this study was to investigate to what extent the soils of this region may delay the response to pH changes through sulphate adsorption, and whether there are evidence for strong soil acidification effects. To this end 26 spodic B horizons were collected along a transect from northernmost Sweden to north-easternmost Norway, only 10 km from the Pechenganikel smelter. As the pH(H₂O) was > 4.8 in all soils, and as the exchangeable Ca/Al ratio was high, there were no evidence for strong soil acidification effects. Water-extractable SO₄ was clearly affected by the S deposition and thus SO₄ was at least partly mobile in the soils; it is therefore possible that soil solutions close to the smelter may have been acidified. In spite of this, sulphate adsorption was found to be more important than cation exchange reactions as a delaying process against soil acidification, at least in the top 10 cm of the B horizon. For the top 20 cm of the B horizon it was estimated that S04 adsorption can neutralize, on average, 700 mmol_c, m^?2 of acid before the pH is decreased to 4.4. Thus if the S deposition remains unchanged, decades are required to severely acidify most soils in the affected parts of Norway and Finland.     

Effects of Acid Deposition on Forest Soils in Northernmost Russia: Modelled and Field Data

In addition to strong natural stresses forest ecosystems in the Kola Subarctic, Russia, receive high loads of sulphur and heavy metals from the nickel smelter. To estimate soil response to acid deposition we compared the soil field data along a pollution gradient and simulated time effects. Multivariate technique was applied to investigate spatial distribution of soil field data. Time response of soils to acid deposition was evaluated with the SMART model. According to field observations there is no evidence for strong soil acidification effects close to the smelter. Concentrations of exchangeable Ca and base saturation increase, while acidity decrease in lower soil mineral horizons towards the pollution source. However, some features seem to reflect the early stages of the started acidification. Most soil profiles have low pH values. Despite increasing of exchangeable Ca and Mg towards the smelter in lower mineral horizons due to geological inheritance, they do not reveal the same trends in the upper ones. Concentration of exchangeable K in organic horizons decreases towards the smelter, thus confirming the starting acidification. As result, exchangeable base cations are depleted in the considerable part of shallow soil profiles. According to model simulation the present acid load does not effect considerably on forest soils in background areas, however, dramatic shift in soil chemistry near the smelter is expected within several decades. Due to low pool of exchangeable base cations and low weathering rate continued acid deposition can lead to increased soil acidification and nutrient imbalance.     

Magnesium,Potassium and Phosphorus in Available Forms in Luvisols in the Vicinity of Głogów Copper Smelter

Region near G?ogów is characterized as industrial—agricultural area, intensively used. Presented study was undertaken to estimate the impact of agricultural land use and the vicinity of G?ogów copper smelter on the contents of available forms of magnesium, phosphorus and potassium in selected profiles of Luvisols. The following analysis were performed: soil particle-size distribution, pH, organic carbon contents, CaCO₃ contents. The contents of available forms of phosphorus and potassium were determined by Egner- Riehm method and that of magnesium using Schachtschabel’s method. The results of the study showed that the contents of available P is medium (III class of abundance), very low in K (V class) and for available Mg very low (V class) to medium for surface horizons and very high (I class of abundance) in other soil horizons. The soils, in spite of the elevated copper content in humus horizons, according to IUNG, were classified as uncontaminated soils, therefore, can be used in plant production for all types of crops.     

Distribution of Zinc,Manganese, Copper,Cobalt, and Nickel in Andosols Profiles

The distribution of zinc, manganese, copper, cobalt, and nickel in Andosols was investigated. Sixty nine soil samples were collected from different horizons of an Andosols profile in Miyakonojo Basin in south Kyushu, Japan, The total contents of heavy metals were determined by digestion and four extraction solutions, 1 M NH₄Ac (ammonium acetate) pH 4.5, 0.1 M HCl, 0.01 M EDTA (ethylenediaminetetraacetic acid) pH 6.5, and 0.005 M DTPA (diethylenetri-aminepentaacetic acid) pH 7.3 were used to determine the contents of available Zn, Mn, Cu, Co, and Ni in Andosols in relation to the organic carbon content. The results of the extraction analysis showed that by the use of 0.1 M H Cl high value of extracted heavy metals in the upper layers of the humus horizons were obtained while EDTA extraction yielded a large amount of the above mentioned metals in the high humus horizons. The extractable heavy metals contents were high and these metals closely related to the organic carbon content mostly in the humus horizons in the profile. Where, biocycling process may play an important role in the concentration of heavy metals. Based on the study, it was found that the total content of Zn increased towards the C horizons or pumice layers in the soil profile. Such a trend was also found in the case of the Mn content. While the Cu content in the humus horizons was much higher in the upper part of each humus horizon. According to this study the distribution of heavy metals, Cu (organic matter complexes) in the Andosols profile was more stable than that of Zn (organic matter complexes) in soils. It was shown that Zn in the surface humus horizon was enriched but that some amount was leached under buried conditions. The same phenomenon was also observed in the distribution of Mn in the profile. The movement of Co and Ni in the soil profile was limited, as evidenced by the sharp reduction in the concentrations of these two metals in buried soils.

Hence, it is concluded that the distribution of Zn, Mn, Cu, Co, and Ni was considerably higher in the humus horizons of the Andosols profiles.     

Soil acidification along a topographic gradient on Roundtop Mountain,Quebec, Canada

We examined the effects that different acidic loadings have had on soil chemistry along a toposequence on Roundtop Mountain. Due to fog interception by the forest canopy, the amount of time in the clouds is a major factor determining the amount and chemistry of precipitation reaching the soil and hence, acid precipitation loading is directly related to elevation. Soils on a transect from 520 to 850 m show a pattern of chemistry that corresponds to the loading of acidic deposition. Soil solutions collected at two elevations show different levels of both SO₄ and Cl, two of the anions in fog water as well as differences in concentrations of H ion and Al. Surface horizons of soils located at 850 m have pH in water as low as 3.7; in mineral horizons base saturation is extremely low (<5%) and Al saturation exceeds 95% in many cases. In contrast, lower on the mountain slope (below 650 m), pH is slightly higher (about 4.1) and base saturation rises to over 50% for the same soil horizons. There is a clear relationship between soil acidification and position on the mountain.     

Humus forms and metal pollution in soil

Smelters in northern France are a serious source of soil pollution by heavy metals. We have studied a poplar plantation downwind of an active zinc smelter. Three humus profiles were sampled at increasing distance from the smelter, and the thickness of topsoil horizons was measured along a transect. We analysed the vertical distribution of humus components and plant debris to assess the impact of heavy metal pollution on the humus forms and on soil faunal activity. We compared horizons within a profile, humus profiles between them, and traced the recent history of the site. Near the smelter, poplar trees are stunted or dead and the humus form is a mor, with a well‐developed holorganic OM horizon. Here faunal activity is inhibited, so there is little faecal deposition and humification of plant litter. At the distant site poplar grows well and faunal activity is intense, so there are skeletonized leaves and many organo–mineral earthworm and millipede faecal pellets. The humus form is a mull, with a well‐developed hemorganic A horizon. The passage from mor to mull along the transect was abrupt, mor turning to mull at 250 m from the smelter, though there was a progressive decrease in heavy metal deposition. This indicates that there was a threshold (estimated to be 20 000 mg Zn kg^?1) in the resilience of the soil foodweb.     

Quantification of anthropogenic lead in Slovak forest and arable soils along a deposition gradient with stable lead isotope ratios

Isotope ratios of Pb may provide the opportunity to determine the contribution of Pb from a point source to Pb concentrations in soil. Our objective was to quantify the contribution of anthropogenic Pb to total Pb and chemical Pb fractions in contaminated soil profiles with the help of ²⁰⁶Pb/²⁰⁷Pb isotope ratios. We sampled 5 forest and 5 arable Cambisols along a transect from a Cu smelter and determined Pb concentrations and ²⁰⁶Pb/²⁰⁷Pb isotope ratios in total digests of all horizons and in 7 chemical fractions of the A horizons. In the organic layer under forest, Pb concentrations decreased from 2155 mg kg^—1 at 1.1 km distance from the smelter to 402 mg kg^—1 at 8 km distance; in the Ap horizons, it decreased from 126 to 72 mg kg^—1. In the total digests, ²⁰⁶Pb/²⁰⁷Pb isotope ratios could be explained by simple mixing of smelter‐ and background‐Pb as indicated by the correlation between the inverse of the Pb concentration and the ²⁰⁶Pb/²⁰⁷Pb ratio (r = 0.93). The mean proportion of smelter‐Pb in soil horizons decreased with depth from 87% (Oi) to 21% (C) under forest and from 64% (A) to 30% (B) in the arable soils. The smelter‐Pb proportions in the B horizons ranged from 6 to 66% and were independent of the distance from the smelter indicating variable leaching rates. The ²⁰⁶Pb/²⁰⁷Pb ratios in the chemical fractions could not be explained by a simple mixing model. Thus, the ²⁰⁶Pb/²⁰⁷Pb ratios may be used to determine the contribution of anthropogenic Pb in total digests but not in chemical Pb fractions.     

Biological recovery of two previously acidified,metal-contaminated lakes near Sudbury Ontario,Canada

Studies are reported on two small lakes at Sudbury, Ontario located close to a nickel-copper smelter which closed in 1972. At that stage, Baby Lake had a pH of 4.0–4.2 while the adjacent Alice Lake had a pH 5.9–6.3. Both lakes were almost entirely devoid of algae and had neither Zooplankton nor fish. Soon after the closure of the smelter, with its large airborne volume of sulphur dioxide and of copper and nickel containing particulates, the chemistry of the lakes began to change. By 1985, Baby Lake had changed from pH 4.0 to 6.8 and is now at pH 7.2. The pH of Alice Lake increased from a low of 5.9 in the early 1970s to 6.9–7.4 in the mid 1980s and is now at 7.3. Copper and nickel concentrations also decreased in both lakes during this period. The first biota found in the lakes in the post-smelter stage in the early 1980s were benthic red chironomids, planktonic rotifers, and a limited number of phytoplankton species, of which Rhizosolenia was the most common. By the 1990s, 13 phytoplankton species were present in each lake, with a substantial Zooplankton fauna (14 species) of rotifers, copepods, and cladocerans. There are now numerous insect larvae in the sediment and some small fish in both lakes. The biological recovery, which followed substantial reductions in acidity and in soluble nickel and copper concentrations in the waters, is a slower process than chemical recovery and is initially characterized by the dominance of a few species.     

Limited downward migration of pollutant metals (Cu,Zn, Ni,and Pb) in acidic virgin peat soils near a smelter

The distribution of pollutant heavy metals (Cu, Zn, Ni, Cd, and Pb) was determined in 11 acidic virgin peat profiles located along two transects moving away from a smelter plant in the Noranda region of Quebec. The levels of all five metals were found highest in the 0 to 15 cm layer at site near the smelter, and decreased progressively with the distance from the smelter, up to 42 km. Copper had the highest concentrations (5525 μg g^?1) followed by Pb and Zn. The maximum levels of total metals built up in the peat surface near the smelter were high, approximately reaching the threshold limits for phytotoxicity in peat soils. The amounts of heavy metals moving down and accumulating in the anaerobic zone of the peat profiles were limited. The distribution and enrichment ratios in the profiles showed that Cu, Zn, and Cd would have relatively higher mobility than Pb.     

Heavy Metal Concentrations,Partitioning, and Storage in Slovak Forest and Arable Soils Along a Deposition Gradient

Along a heavy metal deposition gradient, caused by a Cu smelter, heavy metal concentrations, partitioning, and storage in forest and arable soils were examined. We sampled organic and mineral soil horizons (0—50 cm) at ten pairs of forest and arable sites derived from the same parent material. A-horizons were extracted with a seven-step sequence; O- and subsoil horizons were digested with strong acids (HNO₃/HClO₄). We found high concentrations of Cd (up to 17.38 mg kg^—1 in the O horizons/up to 2.44 mg kg^—1 in the A horizons), Cu (8437/415), Pb (3343/126), and Zn (1482/637) which decreased exponentially with distance from the smelter and with soil depth. The metal concentrations in the organic layers indicate that the average transport distance decreases in the order Cd > Zn > Pb > Cu. With regard to metal partitioning, NH₄NO₃- + NH₄OAc-extractable forms in the A horizons were most affected by the deposition being more pronounced under forest. In the uppermost 50 cm of the four soils nearest to the smelter two to four times higher Cd, Cu, Pb, and Zn storages were found in forest than in arable soils. At greater distance, the higher deposition onto forest soils due to the scavenging effect of the canopy obviously was compensated by stronger leaching.     

Heavy Metal Contamination in Peach Trees Irrigated with Water from a Heavily Polluted Creek

This study was conducted to characterize the heavy metal contamination in the soils of peach orchards irrigated with water from Nilüfer creek, which is heavily polluted by industrial and municipal wastes. Twenty-one peach orchards with 3 different cultivars in 7 orchards each located along Nilüfer creek were monitored in the experiment. To determine levels of pollution, soils and aboveground parts of the trees were sampled and analyzed for iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), cobalt (Co), nickel (Ni), chromium (Cr), lead (Pb), and cadmium (Cd). Total amounts of Ni and Cr were found to be at the excessive levels in soils. Extractable Ni concentration decreased with increasing pH and CaCO₃ content in soils. Leaf metal contents were generally at tolerable levels, but Ni and Pb accumulated to toxic levels in different parts of the fruit (flesh and peel). Except for Fe and Ni, plant concentrations of the metals did not correlate with their total and DTPA-extractable concentrations in the soils. There was no significant difference among the cultivars in accumulation of heavy metals.     

Variabilität der Sulfatsorption in einem Gley-Podsol aus Sand unter Kiefernforst

Variability of sulfate sorption in a sandy Gleyic Podzol under a pine stand In acid forest soils sulfate can be stored by sorption processes. We studied the vertical heterogeneity and the horizontal variability of sulfate sorption in a sandy forest soil under a pine stand. Disturbed soil samples were taken from the horizons of a Gleyic Podzol (vertical heterogeneity). From a 120-m transect, 25 soil samples were taken from depth increment 35—50 cm and 65—80 cm at 5-m intervals by means of a hand auger (horizontal variability). In batch experiments, sulfate sorption isotherms were measured for all profile and transect samples. The Freundlich equation is suitable to describe the individual isotherms. The sulfate sorption isotherms show considerable differences in the horizons of the profile, systematic relations between the isotherm parameters and soil properties are not obvious. In order to quantify the spatial variability of the sulfate sorption isotherms, a scaling technique is used. The spatial distribution of scale factors for depth 35—50 cm along the transect reveals a periodicity of about 17 m length. The same recurrent pattern is also identified in the spatial distribution of the cumulative sulfate deposition by canopy throughfall along the transect, and in the spatial distribution of contents of iron and aluminium oxides soluble in oxalic acid at depth level 35—50 cm. This does, however, not refer to organic carbon content and pH at this depth. From these results it is concluded that in this soil at depth 35—50 cm oxide contents are related to the amount of sulfate deposition by throughfall. In spatial ranges with high sulfate and thus acid deposition, oxide contents of the soil are decreased by accelerated podzolization, and therefore, also the sulfate sorption of the soil is low in these ranges. The period length of this recurrent pattern of about 17 m is probably only an apparent period length that results from aliasing, because a very probably real periodicity of 3—4 m length, related to the canopy edge distribution of the pine trees along the transect, is sampled at an interval of 5 m. In the subsoil (65—80 cm depth) such relations could not be detected.     

Soil Aluminum Distribution in the Near-Stream Zone at the Bear Brook Watershed in Maine

Near-stream and upslope soil chemical properties were analyzed to infer linkages between soil and surface water chemistry atthe Bear Brook Watershed in Maine [BBWM]. Organic and mineral soil samples were collected along six 20 m transects perpendicular to the stream and one 200 m transect parallel tothe stream. O horizon soils immediately adjacent to the streamhad a significantly higher pH (4.20) and lower soil organic matter percentage (54%) than upslope O horizons (3.84 and 76%,respectively). Additionally, near-stream O horizon soils hadsignificantly higher concentrations of water-soluble Al (2.7 ×),exchangeable Al (2.3 ×), and organically-bound Al (3.9 ×) andsignificantly lower concentrations of exchangeable Ca (0.4 ×) than O horizons upslope. These results suggest that Al can accumulate in non-hydric near-stream zone soils at this site. Mobilization of labile Al from near-stream zone soils duringhydrologic events could play a key role in explaining controls on Al in stream water at BBWM.     

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

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

Effects of acid deposition on acidity and exchangeable cations in podzols of the Kola Peninsula

Response of soil and soil water of podzols in the Kola Peninsula to acid deposition was estimated under both field and laboratory conditions. A significant increasing trend of exchangeable acidity in organic (O) horizons and exchangeable Al in podzolic (E) horizons of podzols with distance from the nickel smelter was observed. The simulated rain at pH 4.5 did not alter chemical properties of soils and soil solutions. As much as 95–99% of the applied H⁺ ions were retained by soils and appeared in the percolates after a treatment period that depended on acid load and soil thickness. Ca and Mg in soil solutions were highly sensitive to acid loading. Simulated acid rain enhanced the leaching of exchangeable base cations out of root zone. Acid inputs resulted in decreased pH, amount of exchangeable base cations and base saturation, in elevated exchangeable acidity and it's Al fraction in soil solid phase. The most significant changes occurred in O and E horizons. Substantial amounts of both Ca and Mg can be lost from the root zone of podzols in the north-western Kola, subjected to acid deposition, thus leading to forest productivity damage.     

Variability and relationships between Pb,Cu, and Zn concentrations in soil solutions and forest floor leachates at heavily polluted sites

Seasonal variability of Cu, Pb, and Zn concentrations in litter leachates and soil solutions was examined in an afforested zone surrounding a copper smelter in SW Poland. Litter leachates (with zero‐tension lysimeters) and soil solutions (with MacroRhizon suction‐cup samplers, installed at a depth of 25–30 cm) were collected monthly at three sites differing in contamination levels in the years 2009 and 2010 (total Cu: 2380, 439, and 200 mg kg^–1, respectively). Concentrations of Cu in the litter leachate were correlated with dissolved organic C (DOC), whereas Zn and Pb were mainly related to leachate pH. Metal concentrations in the soil solution were weakly influenced by their total content in soils and the monthly fluctuations reached 300, 600, and 700% for Cu, Pb, and Zn, respectively. Metal concentrations in soil solutions (Cu 110–460 μg L^–1; Zn 20–1190 μg L^–1; Pb 0.5–36 μg L^–1) were correlated with their contents in the litter leachates. Chemical speciation, using Visual Minteq 3.0, proved organically‐complexed forms even though the correlations between metal concentrations and soil solution pH and DOC were statistically insignificant. The flux of organically‐complexed metals from contaminated forest floors is believed to be a direct and crucial factor affecting the actual heavy metal concentrations and their forms in the soil solutions of the upper mineral soil horizons.     

伊朗中部伊斯法罕地区土地利用对石灰性土壤磁性质和重金属的空间分布的影响

Anthropogenic activities have caused the accumulation of heavy metals in the soil environment. Pollution of the soils significantly reduces environmental quality and affects human health. In many recent studies, magnetic susceptibility measurements have been used for pollution monitoring. The objective of this research was to determine the spatial variability of magnetic properties and selected heavy metals and the effects of land use on their variability in the surface soils of the Isfahan region, Central Iran. A total of 158 composite surface (0-5 cm) samples of calcareous soils were collected from an area of about 700 km2, located along a cross-border transect from Isfahan City to a steel plant, covering urban, industrial, agricultural and uncultivated land uses. Concentrations of copper (Cu), zinc (Zn), lead (Pb), manganese (Mn), iron (Fe), nickel (Ni), chromium (Cr), and cobalt (Co) and magnetic parameters, magnetic susceptibility at low frequency (χlf), natural remanent magnetization (NRM), saturation isothermal remanent magnetization (SIRM), and isothermal remanent magnetization at the field of 100 mT (IRM100mT) and the backfield of 100 mT (IRM-100mT), were measured in all the soil samples. Results showed that magnetic susceptibility in the urban and industrial land topsoils (0--5 cm) samples was significantly higher than that in the agricultural and uncultivated land soils in the study area. Concentrations of Cu, Zn, Pb, Mn, and Fe were positively correlated with magnetic properties (χlf, IRM100mT, SIRM, IRM-100mT, and NRM), which could be attributed to their inputs from traffic emissions and industrial activities at the study sites. Ni and Cr concentrations showed significant negative correlations with magnetic properties. No significant correlation was found between Co concentration and magnetic parameters. The Tomlinson pollution load index (PLI) showed significant correlation with the magnetic properties (χlf, IRM100mT, SIRM, IRM-100mT, and NRM). The spatial distribution of the selected heavy metals and χlf in the study area suggested that activities at the urban and industrial land sites caused greater pollution as compared to that at the study sites of other land uses. The concentrations of Cu and Zn seemed to have been affected by anthropogenic sources, whereas Ni, Cr, and Co were mainly controlled by natural sources in the study area. Moreover, the concentrations of soil Pb and Fe in the study area could be affected by both lithologic and anthropogenic sources. The magnetic parameters appeared to be a proxy measure for the degree of heavy metal contamination and could be a potential method for the detection and mapping of contaminated soils.