Preface.- Contributors.- List of Abbreviations.- Section 1: Basic Principles: Introduction.-Sources of Heavy Metals and Metalloids in Soils.- Chemistry of Heavy Metals and Metalloids in Soils.- Methods for the Determination of Heavy Metals and Metalloids in Soils.- Effects of Heavy Metals and Metalloids on Soil Organisms.- Soil-Plant Relationships of Heavy Metals and Metalloids.- Heavy Metals and Metalloids as Micronutrients for Plants and Animals.-Critical Loads of Heavy Metals for Soils.- Section 2: Key Heavy Metals And Metalloids: Arsenic.- Cadmium.- Chromium and Nickel.- Cobalt and Manganese.- Copper.-Lead.- Mercury.- Selenium.- Zinc.- Section 3: Other Heavy Metals And Metalloids Of Potential Environmental Significance: Antimony.- Barium.- Gold.- Molybdenum.- Silver.- Thallium.- Tin.- Tungsten.- Uranium.- Vanadium.- Glossary of Specialized Terms.- Index.

Heavy metals in soils : trace metals and metalloids in soils and their bioavailability

Atmospheric mercury—An overview

Because it is very toxic and accumulates in organisms, particularly in fish, mercury is an important pollutant and one of the most studied. Nonetheless we still have an incomplete understanding of the factors that control the bioconcentration of mercury. Elemental mercury is efficiently transported as a gas around the globe, and even remote areas show evidence of mercury pollution originating from industrial sources such as power plants. Besides elemental mercury, the major forms of mercury in water are ionic mercury (which is bound to chloride, sulfide, or organic acids) and organic mercury, particularly methylmercury. Methylmercury rather than inorganic mercury is bioconcentrated because it is better retained by organisms at various levels in the food chain. The key factor determining the concentration of mercury in the biota is the methylmercury concentration in water, which is controlled by the relative efficiency of the methylation and demethylation processes. Anoxic waters and sediments are an important source of methylmercury, apparently as the result of the methylating activity of sulfatereducing bacteria. In surface waters, methylmercury may originate from anoxic

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The chemical cycle and bioaccumulation of mercury

Remediation of heavy metal(loid)s contaminated soils - To mobilize or to immobilize?

Mercury is one of the most hazardous contaminants that may be present in the aquatic environment, but its ecological and toxicological effects are strongly dependent on the chemical species present. Species distribution and transformation processes in natural aquatic systems are controlled by various physical, chemical, and biological factors. Depending on the prevailing environmental conditions, inorganic mercury species may be converted to many times more toxic methylated forms such as methylmercury, a potent neurotoxin that is readily accumulated by aquatic biota. Despite a considerable amount of literature on the subject, the behavior of mercury and many of the transformation and distribution mechanisms operating in the natural aquatic environment are still poorly understood. This review examines the current state of knowledge on the physicochemical behavior of mercury in the aquatic environment, and in particular the environmental factors influencing its transformation into highly toxic methylated forms.

Mercury in the Aquatic Environment: A Review of Factors Affecting Methylation

During the last decade a new pattern of Hg pollution has been discerned, mostly in Scandinavia and North America. Fish from low productive lakes, even in remote areas, have been found to have a high Hg content. This pollution problem cannot be connected to single Hg discharges but is due to more widespread air pollution and long-range transport of pollutants. A large number of waters are affected and the problem is of a regional character. The national limits for Hg in fish are exceeded in a large number of lakes. In Sweden alone, it has been estimated that the total number of lakes exceeding the blacklisting limit of 1 mg Hg kg-1 in 1-kg pike is about 10 000.

Mercury in the Swedish environment — Recent research on causes, consequences and corrective methods

As a result of air pollution, the content of Hg in fish has significantly increased in a large part of Scandinavia and North America. In this paper, the occurence and fluxes of Hg in Swedish forest soils and waters are reviewed and synthesized. The main objective is to describe and evaluate the present transport of anthropogenic Hg from atmospheric deposition, through the terrestrial compartment and running waters to lake basins and also to comprehend the main factors influencing these fluxes. The transportation and distribution. of Hg in forest soils and waters is closely related to the flow of organic matter. The content of Hg in humic matter is higher in southern and central areas compared to the north of the country. Compared to background concentrations, the Hg content has increased in the southern and central part by about a factor of 4–7, while the overall increase in the north is by about a factor of 2 to 3. The increased content of Hg in forest soils may have an effect on organisms and biological processes in the soil. Regarding budget calculations for whole catchment areas and for the mor layer of the soil, a reduction of about 80% from present atmospheric wet deposition must be obtained to reach “critical load” with respect to conditions in Scandinavia.

Mercury in swedish forest soils and waters — Assessment of critical load

Plant material and soil samples from seven long-term field experiments with different liming rates and fertilizer levels were analysed for Mn, Zn, Cu, Ni, Pb, Cd, Cr and As. Liming consistently decreased the plant levels of Mn, Zn and Ni, whereas Pb, Cr and As did not seem to be influenced. Cu was only slightly influenced and the influence on Cd levels varied inconsistently in grain/seeds. In straw/ley the expected decrease in Cd level with increasing base saturation and pH was found. Liming consistently decreased easily soluble fractions of Zn, Ni and Pb in soils. Only Cd was influenced by the level of fertilizer, with an obvious tendency towards increasing Cd levels in plants and soils at increasing rates of fertilizer application.

Levels of Cd and Some other Trace Elements in Soils and Crops as Influenced by Lime and Fertilizer Level

Grain samples from four varieties of winter wheat, grown within the same limited area, one of them during the entire period 1918–1980, were analysed for Cd and some other elements for comparison. Two types of variation were found for Cd, namely annual fluctuations and systematic increase with time. The annual fluctuations in Cd content were about twice as high as for the other elements investigated, as expressed by the standard deviation as a percentage of the averages. They were most likely caused by climatic fluctuations during the growing season and by the variation in soil factors like pH and soil type when the growing was alternated between adjacent fields. There was a significant positive correlation between the Cd and Zn contents, despite different time trends. The Cd content was independent of the yield level. The time trend, meaning more than a doubling of the Cd content in grain during the period 1918–1980, may be partly due to increased solubility and availability to plants of the soil...

Arne Andersson

Papers

Mercury in the Swedish environment — Recent research on causes, consequences and corrective methods

Mercury in swedish forest soils and waters — Assessment of critical load

Levels of Cd and Some other Trace Elements in Soils and Crops as Influenced by Lime and Fertilizer Level

Trends and Annual Variations in Cd Concentrations in Grain of Winter Wheat

Regional accumulation pattern of heavy metals in lake sediments and forest soils in Sweden