«Dissertation zur Erlangung des Grades “Doktor der Naturwissenschaften” Im Promotionsfach Geowissenschaften Am Fachbereich Chemie, Pharmazie und ...»
Zusammenfassung (Tl) Böden aus der Nähe einer Zementfabrik nahe von Lengerich in Deutschland wurden auf ihre Thallium Belastung hin untersucht. Für zwei Probenahmegebiete (Standort 1 und 2) wurde die mobile und gesamte Thallium Belastung gemessen. Die mobile Fraktion des Ober- und Unterbodens an Standort 1 zeigte eine Thallium Konzentration im Bereich 20-130 und 0-100 µg/kg. Die Gesamtkonzentration am Standort 1 für Ober- und Unterboden war im Bereich von jeweils 0,4-2,4 und 0,3-1,3 mg/kg. Die Konzentration der mobilen Fraktion am Standort 2 war für ober und Unterboden jeweils 20-540 und 10-170 µg/kg. Die Gesamtkonzentration an Thallium am Standort 2 war für Ober- und Unterboden im Bereich von 0,8-3,2 und 0,4-1,4 mg/kg. Es wurde eine Semivarianzanalyse der Ammoniumnitratextrakte und damit der austauschbaren Thallium Gehalte des Oberbodens am Standort 1 durchgeführt. Diese Analyse zeigt eine moderate räumliche Abhängigkeit des austauschbaren Thalliums des Oberbodens. Die Ergebnisse zeigen für beide Probenahmegebiete einen unterschiedlichen Grad der Thallium Kontamination. Ein T-Test für gepaarte Stichproben zeigte für die mobile und gesamte Thallium Konzentration einen statistisch signifikanten Unterschied zwischen Ober und Unterboden für beide Probenahmegebiete. Der anthropogene Eintrag ist eine mögliche Quelle der überhöhten Thallium Konzentration des Oberbodens.
XVI Leader Abstract There is a long history of human using metals in developing an advanced technological society.
It has only been realized until the past century that metal’s chemical and radioactive properties can pose serious threat to mankind. In modern day geochemistry it is widely accepted that the specific physiochemical forms rather than the total concentration decides the ultimate trace metal behavior in an environment. The definition of speciation can be broadly classified as the identification and quantification of the different forms or phases for an element. Chemical extraction is a common speciation technique in which fractionating total metal content for analyzing the source of anthropogenic metal contamination and also to predict bioavailability of various metal forms. The philosophy of the partial and sequential extraction method is to assume that particular extractant is phase specific under chemical attack on a mixture of forms.
Speciation of metal is important in determining metal’s toxicity, mobility, bioavailability and hence their fate in environment and biological systems. Speciation analysis can be applied in understanding the impact on human health and ecological risks by quantifying the metal species at a sampling site and subsequently suitable remediation strategies can be implemented for the location. Speciation of arsenic and copper in agricultural lime and thallium in contaminated soils were investigated and revealed in the following sections.
(Arsenic) Heavy metals contamination to the terrestrial environment long exists due to the natural weathering of the parent rocks in which causing metal precipitation in the system. The widely observed increase trace element concentrations in agricultural soil due to various human activities such as liming would lead to potential harmful effects on mankind. Natural reduction in lime status for most soils would increase soil acidity and reduce soil fertility. Toxic metals and metalloids such as arsenic have the abilities to scavenge with Fe and Mn oxides present in low grade limestone and leach out from the soils under severe environmental condition. Adsorption of arsenic into the soil system depends greatly on the physicochemical behaviour in which arsenic enters the soil. Sequential extraction method was used to partition different arsenic species in associated with various metal-bearing phases. As, Fe and Mn contents in five extraction steps were determined by HG-AAS and XRF techniques. Solution matrix effect was observed throughout the HG-AAS analysis and minimized with addition of 1% cysteine as masking agent. All soil sub-samples demonstrated much higher As content than the above global average content of arsenic being found in limestone, pellet limestone for soil pH amendment and MAP/DAP phosphate fertilizers with majority of As showed strong binding with crystalline Fe phases. Direct X-ray spectroscopic analysis was deemed necessary because of possible repartitioning of As between dissolved Mn and residual Fe oxides in the first three extractions steps.
Abstract (Copper) The main host phases and solid speciation of Cu accumulated in agricultural lime samples were determined. Copper is an essential element for life but can be toxic to ecosystem when it is excessively accumulated. Agricultural liming is one of many ways of accumulating copper in soils and as copper is often accumulated by strongly complexing with soil organic matter.
Excessive accumulation of copper would cause Cu phytotoxicity and rhizotoxicity of plants and as a result Cu speciation would be essential on providing necessary information on handling with the Cu contaminated soils in long term future. A modified BCR sequential extraction scheme of Cu fractionation was developed and applied in order to partition metals in different Cu metalbearing phases. Cu, Fe, Mn and Ca contents in four extraction steps were determined by AAS and XRF techniques. All sub-samples demonstrated above usual 2-8 mg/kg Cu content in limestone for soil amendment and five out of six sub-samples revealed higher than typical phosphate fertilizers Cu level (1-13 mg/kg). The Cu concentrations of six sub-samples were found to be 12, 41, 69, 137, 140 and 174 mg/kg. Three out of the six-subsamples exceeded soil health tolerance level of 100 mg/kg for Cu. All the observed concentrations suggested excessive Cu in lime could be loaded on the uncontaminated soil and cause Cu toxicity to plants. The sequential extraction results showed that Cu was able to be mobilized acidic and reducing conditions. Cu identified in the first step could be associated with the carbonate matrix or the oxide dendrites alone, or the combination of both. It is important to distinguish Cu loaded between carbonate matrix phase and oxide dendrites phase as Cu from these two phases could be mobilized under different environmental condition (e.g. reducing). Direct X-ray spectroscopic speciation analysis was considered to be next stage in depth analysis for the Cu speciation.
Abstract (Thallium) The surveillance of soils with thallium exposure in the vicinity of a cement plant at Lengerich, Germany was undertaken. The results revealed mobile and total thallium concentration at top and sub-soils at two sampling location (location 1 and 2). Top and sub-soils at sampling location 1 showed exchangeable thallium concentration in a range of 20-130 and 0-100 µg/kg. The total thallium concentration at location 1 for top and sub-soils were in a range of 0.4-2.4 and 0.3-1.3 mg/kg respectively. Top and sub-soils at sampling location 2 showed exchangeable thallium concentration in a range of 20-540 and 10-170 µg/kg. The total thallium concentration at location 2 for top and sub-soils were in a range of 0.8-3.2 and 0.4-1.4 mg/kg respectively. Semivariance analysis of top-soils ammonium nitrate extracts targeting exchangeable thallium at sampling location 1 was applied and suggested exchangeable thallium in top-soils was moderately spatially dependent. The results suggested that soils at both sampling sites showed different degrees of thallium contamination. Paired t-test showed mobile and total thallium concentration between top and sub-soils were considered to be statistically significant difference at both sampling locations. The excessive thallium contents found in the surface soils at the two sampling locations were potentially from anthropogenic emission sources. Several possible pathways of causing soil pollution on the sampling locations were proposed. The top and subsoils thallium contents at two sampling sites contained different size of areas in where exceeding the safety limit of mobile thallium set by the German Federal Minster of Justice and total thallium established by North-Rhine Westphalia of Federal Republic of Germany.
(1.0) Introduction (1.1.1) Introduction of arsenic Arsenic (As) is a ubiquitous element existed in many sources in natural environment ranging from atmosphere, soils, rock to natural waters and organisms. Arsenic has long been drawing special attention from the scientific community due to its risks to human health and ecology. Most of environmental As problems existing in the world are the result of mobilization under natural conditions. The environmental toxicity effects are the consequences of arsenic mobilization under natural processes such as weathering reactions, biological activity and a range of anthropogenic activities.
Human activities also have had further contribution of As to natural environment through several of commercial activities such as mining, fossil fuels combustion, wood preservation (CrCu-As salts) and arsenical pesticides, herbicides (As2O3) application. Additional anthropogenic As sources can also be found in the following activities of mankind: High-temperature combustion (oil- and coal burning power plants, waste incineration, cement works); glassware production (discoloring agent); electronics industries (admixture in semiconductor production, arsenide as laser material to convert electrical energy into coherent light); ore production and processing (melting and roasting in non-ferrous smelters, melting in iron works); metal treatment (admixture in bronze production, lead and copper alloys); chemistry (dyes and colours, drying agent for cotton, oil and dissolvent recycling).
In modern days, public pay much attention to arsenic due to the observed harmful effects to people in worldwide. Problems are still pandemic in countries such as Bangladesh and India.
Arsenic is not considered an essential element of human metabolism, but is commonly absorbed or ingested and present in the body. Inorganic As compounds can be reabsorbed through human lungs and intestines. Prolong exposure of As can possibly induce skin, bladder, liver, kidneys, lungs and prostate gland cancer, as well as coronal heart diseases. The chronic As exposure is the hyperkeratosis on the palms of the hands and soles of the feet as well as excessive pigmentation of the skin at non-sun-exposed body parts. Malnutrition (Zn-depletion) and high amount of humic substances within As-contaminated water have a positive effect on Blackfoot disease.
There are several pathways for human of undertaking arsenic through for example air (inhalation of volatile arsine AsH3 in swampy areas), food and drinking water consumption.
Drinking water which poses the greatest threat to human health is derived from a variety of sources depending on local availability: surface water (rivers, lakes, reservoirs and ponds), groundwater (aquifers) and rain water. It is understood that approximately 30% of the As intake for human consumption goes via drinking water (Appelo and Postma, 1994). It is worth noticed that the World Health Organization (WHO) guideline value for As in drinking water was provisionally reduced in 1993 from 50 to 10 µg/l due to the increasing awareness of the carcinogenicity of As. The EC maximum admissible concentration (MAC) for As in drinking water has also been reduced to 10 µg/l. Both the WHO guideline value and current national standards are quite frequently exceeded in drinking water resources.
(1.1.2) Arsenic speciation and occurrences in natural environment Arsenic is a steel-gray, brittle, crystalline metalloid with three allotropic forms (e.g.
As2O3, As2O5 and As2O4) and a constituent of more than 245 minerals presented in Group 15 of the periodic table existing in various oxidation states (+5, arsenate), (+3, arsenite), (0, arsenic) and (-3, arsine) in the natural environment. Metalloids have properties of both metals and nonmetals with tendencies of forming amphoteric oxides and behaving as semiconductors. Arsenic however, tends to behave like a group V A elements than heavy metals. Elemental arsenic is considered to be non-poisonous. As3+ (exists as H3AsO3/H2 AsO3 - in pH range 4-9) exists stably in reducing conditions such as regularly flooded soils and As5+ (H2AsO4 - or HAsO42-) presents in a stable form in oxygen-rich environments and well-drained soils and are the main inorganic forms of As in most contaminated soils and sediments. As5+ is less soluble, mobile and toxic than As3+ due to its stronger association with soil solids. As5+ (AsO43-) compounds are usually dominating in aerobic soils whereas As3+ compounds mainly occur in slightly reduced soils.
Organic arsenic species (e.g. monomethylarsonate, dimethylarsenate and arsenobetaine), though toxic, are usually quantitatively insignificant towards the solid phase of forest soils because microorganisms easily degrade these compounds to As5+.
The total amount of As in the earth crust is estimated to be 4.01 x 10 16 kg (Matschullat, 2000). The crustal abundance of arsenic in natural source is around 1.5-2 mg/kg (National Research Council, 1977). The global average concentration of As in uncontaminated soils is around 5 mg/kg (Dragun and Chiasson, 1991). The following table (1) lists As concentration values obtained in different types of soils.
Table (1) Table shows some observed As concentrations in different soils
The above As concentrations found in soils are heavily depending on different factors which are local geological conditions, concentration in parent rock materials and a range of industrial activities (e.g. smelting).