Differences In Trace Element Concentrations Research Articles

Anguilliform fish reveal large scale contamination by mine trace elements in the coral reefs of New Caledonia

Due to intensive mining activity, increasing urbanization and industrialization, vast amounts of contaminants are discharged into the lagoon of New Caledonia, one of the largest continuous coral reef systems and a major biodiversity hotspot. The levels of 11 trace element concentrations were examined in the muscles of predator fish in the south-western lagoon (moray eels and congers). These species are sedentary, widespread, abundant, and they are easily collected using a sea snake sampling technique. We found the highest mean and maximal concentrations of different trace elements ever found in coral fish, notably regarding trace elements typical from mining activity (e.g., mean values for Cr and Ni, respectively: 5.53±6.99μgg−1 [max, 35.7μgg−1] and 2.84±3.38μgg−1 [max, 18.0μgg−1]). Results show that important trace element contamination extends throughout the lagoon to the barrier reef, following a concentration gradient from the oldest nickel factory (Nouméa).

First data on composition of the volcanic rocks of the IVS 50th anniversary Fissure Tolbachik eruption (Kamchatka)

First data on major, minor and trace element (XRF. 1CP-MS) concentrations in the volcanic rocks of the IVS 50th anniversary Fissure Tolbachik eruption are reported for the period from 27.11.2012 to 25.01.2013; scheme of lava flows distribution by March 2013 is made. The volcanic rocks of the new eruption are substantially different from the other studied volcanic rocks of Tolbachinsky Dol by their higher alkalis and incompatible elements content. The rocks of the first three days of eruption (Menyailov Vent) have higher silica and alkalis content than all previously reported volcanic rocks of Tolbachinsky Dol. Volcanic rocks of the Naboko Vent, at silica content similar to high-Al basalts of Tolbachinsky Dol, have different concentrations of trace elements and some major elements (K2O, CaO, TiO2, P2O5). REE and other incompatible element concentrations in the rocks of the Menyailov Vent are higher than in the rocks of the Naboko Vent at the same element ratios. The differences of the volcanic rocks of the two vents of the new eruption may be caused by the fact that the erupted lavas came from the different levels of the same magma chamber.

Changes in trace element contents in ashes of oil shale fueled PF and CFB boilers during operation

Two oil shale combustion technologies, pulverized firing (PF) and circulated fluidized bed (CFB) were compared with respect to partitioning of selected elements (Ba, Cd, Co, Cr, Cu, Hg, Mn, Mo, Ni, Pb, Rb, Sb, Sn, Sr, Th, Tl, U, V, and Zn) in the ashes along the flue gas ducts. The ash samples were characterized by high-resolution ICP-MS. The average contents of toxic heavy metals in fly ash samples from the CFB boiler are lower compared to the PF boiler. Main differences in trace element contents between combustion technologies were as follows: Cd content in the fly ash samples of PF boiler was up to 0.9mg/kg while in CFB boiler it remained below 0.1mg/kg in all analyzed ash samples; Hg was observed in the ashes of electrostatic precipitator (ESP) of CFB boiler while in the PF boiler it was close to or below detection limit. In the PF boiler content of Sn was detected only in the ashes of ESPs, while in CFB boiler it was evenly distributed between bottom and fly ash samples. Highest content among heavy metals in ash samples was observed for Pb in the last field of ESP of the PF boiler (142mg/kg).

Sampling strategy and analysis of trace element concentrations by inductively coupled plasma mass spectrometry on medieval human bones – the concept of chemical life history

Medieval human bones have the potential to reveal diet, mobility and treatment of diseases in the past. During the last two decades trace element chemistry has been used extensively in archaeometric investigations revealing such data. Many studies have reported the trace element inventory in only one sample from each skeleton - usually from the femur or a tooth. It cannot a priori be assumed that all bones or teeth in a skeleton will have the same trace element concentrations. Six different bone and teeth samples from each individual were carefully decontaminated by mechanical means. Following dissolution of ca. 20 mg sample in nitric acid and hydrogen peroxide the assays were performed using inductively coupled plasma mass spectrometry (ICPMS) with quadropole detection. We describe the precise sampling technique as well as the analytical methods and parameters used for the ICPMS analysis. The places of sampling in the human skeleton did exhibit varying trace element concentrations. Although the samples are contaminated by Fe, Mn and Al from the surrounding soil where the bones have been residing for more than 500 years, other trace elements are intact within the bones. It is shown that the elemental ratios Sr/Ca and Ba/Ca can be used as indicators of provenance. The differences in trace element concentrations can be interpreted as indications of varying diet and provenance as a function of time in the life of the individual - a concept which can be termed chemical life history. A few examples of the results of such analyses are shown, which contains information about provenance and diagenesis.

Disturbances of trace element metabolism in ESRD patients receiving hemodialysis and hemodiafiltration

IntroductionAccumulation of trace elements occurs in conditions of decreased kidney function. In some conditions, increased trace elements can have toxic features. On the other hand, studies are showing that concentration of some trace elements could be decreased in ERSD patients as well. The most important factor affecting trace element concentration in ERSD patients is the degree of renal failure and the usage of replacement therapy.Materials and methodsWe analyzed the trace elements’ (boron, aluminum, vanadium, chromium, manganese, cobalt, nickel, copper, zinc, arsenic, selenium, rubidium, strontium, cadmium, cesium, barium and lead) concentration in the whole blood of 41 ESRD patients who were treated with hemodialysis and hemodiafiltration and also of 61 healthy blood donors. In addition, comparison of trace element blood levels of patients receiving hemodialysis and hemofiltration was carried out. Whole blood trace element concentration was determined using inductive coupled plasma mass-spectrometry (ICPMS).ResultsLevels of boron, aluminum, vanadium, chromium, manganese, zinc, strontium, cadmium, barium and lead were significantly increased in ESRD patients. Significantly decreased levels were observed for nickel, arsenic, selenium and rubidium. Blood levels of cobalt, copper, cadmium and lead in hemodialysis patients were significantly higher compared to patients receiving hemodiafiltration.ConclusionsESRD is accompanied with serious and multidirectional changes of trace element blood levels. The highest degree of blood level increases were observed for nonessential and toxic trace elements. Disorders of essential trace elements were manifested in a minor degree. Besides this, there were observed differences of trace element concentrations between ESRD patients receiving hemodialysis and hemo-diafiltration.

A provenance study of coffee by photon activation analysis

Photon activation analysis (PAA) is a multi-elemental radioanalytical technique in trace elements analysis with high accuracy and precision. Researchers at the Idaho accelerator center performed PAA analysis on coffee samples from several locations around the world as an initial step in assessing the relationship between trace elements in illicit drugs and the soils in which they were grown. The preliminary results show coffees from different locations have different concentrations of trace elements. In the three cases where we have soil samples, the matrices of elements in the coffee samples are closely related to the matrices of the elements of the local soil samples. The majority of trace elemental content is similar to that of the local soil sample in which the coffee is planted. It may be that coffee assimilates numerous elements from the soil where it is grown in similar ratios as is found in the soil. Thus, it is conceivable that the elemental content could serve as “fingerprint” to trace the origins of the coffee. To verify our analytical results we applied X-ray fluorescence (XRF) methods as well. Our PAA results are consistent with XRF experimental data. The future of tracing the origin of illicit drugs with the PAA technique is promising.

Discrimination between different water bodies from a multilayered aquifer (Kaluvelly watershed, India): Trace element signature

In the multilayered aquifer of Kaluvelly (India), comprising various sedimentary layers overlying a charnockitic basement, concentrations of trace elements were measured in aquifer formations and in groundwaters to identify geochemical tracers for water bodies. The two main sandstones (Cuddalore and Vanur) originate from the charnockites and the Cuddalore sandstone has experienced lateritization. In the studied area, two charnockite end-members were identified: a dioritic and a granitic one. Mineralogical composition and whole-rock Ti concentrations confirmed the charnockite which displayed the granitic composition as the parent rock of the two sandstones. Titanium distribution indicates that the Cuddalore sandstone originates from a more intense weathering of the parent material than the Vanur sandstone. Despite extensive differences in trace element contents recorded in aquifer formations, only a few trace elements were suitable to distinguish the water bodies. Among soluble elements, Li (in the Vanur aquifer) and Ba (in the charnockite and carbonaceous aquifers) can be used as tracers. As the input of these elements in solution is mainly regulated by the available stock, for a given mineralogical origin there is a direct link between the aquifer formation composition and water signature. With the exception of As, concentrations of redox-sensitive elements were not preserved during pumping because of oxidation, preventing their use as tracers. Low-mobility elements such as La, Ce, Th, Zr, Nb, Hf, or Ta were too insoluble to be detected in waters and/or to record the aquifer formation signature. Their input in solution was not regulated by the available stock but by the dissolution rate of rock-forming minerals. Only Ti can be used to distinguish between two out of the three aquifers (charnockite and Vanur). The specific behavior of Ti recorded in these waters may be linked to rutile inclusions within plagioclases and to the influence of climate on Ti solubility.

Equation Reliability of Soil Ingestion Estimates in Mass‐Balance Soil Ingestion Studies

Exposure to chemicals from ingestion of contaminated soil may be an important pathway with potential health consequences for children. A key parameter used in assessing this exposure is the quantity of soil ingested, with estimates based on four short longitudinal mass-balance soil ingestion studies among children. The estimates use trace elements in the soil with low bioavailability that are minimally present in food. Soil ingestion corresponds to the excess trace element amounts excreted, after subtracting trace element amounts ingested from food and medications, expressed as an equivalent quantity of soil. The short duration of mass-balance studies, different concentrations of trace elements in food and soil, and potential for trace elements to be ingested from other nonsoil, nonfood sources contribute to variability and bias in the estimates. We develop a stochastic model for a soil ingestion estimator based on a trace element that accounts for critical features of the mass-balance equation. Using results from four mass-balance soil ingestion studies, we estimate the accuracy of soil ingestion estimators for different trace elements, and identify subjects where the difference between Al and Si estimates is larger (>3 RMSE) than expected. Such large differences occur in fewer than 12% of subjects in each of the four studies. We recommend the use of such criteria to flag and exclude subjects from soil ingestion analyses.

Trace elements in Anadara spp. (Mollusca: Bivalva) collected along the coast of Vietnam, with emphasis on regional differences and human health risk assessment

This study measured concentrations of 21 trace elements in whole soft tissue of the blood cockle Anadara spp., which is a common food for local people, collected along the coast of Vietnam. Results showed that concentrations of As, Sr, Mo, Sn, and Pb in cockles collected from Khanh Hoa Province in the Central Coastal Zone (CCZ) had higher values than those from the other regions, while cockles collected from the Mekong River Delta (MRD) showed the highest concentrations of Hg. Regional differences in trace element concentrations of the cockle may be due to differences in human activities, i.e., shipyards in the CCZ and agriculture in the MRD. Trace element concentrations measured in the soft tissues of blood cockles investigated here were within safe levels for human consumption following criteria by the European Commission (EC) and the United States Food and Drug Agency, but several specimens had Cd levels exceeding the EC guidelines of 1 μg/g wet weight. The estimated target hazard quotients for trace elements via consuming bivalves were <1, indicating that the cumulative noncarcinogenic risk was completely insignificant. However, the estimated target cancer risk values by assumed inorganic As concentrations seem to implicate consumption of these cockles as posing potential human health concerns.

Toxic Element Analyses of Summer and Winter Storm-Water Sediment by Neutron Activation Analyses

AbstractTo maintain the effectiveness of a storm-water detention/retention pond, the sediments accumulating at the bottom the pond must be periodically removed and treated for ultimate disposal. The required pond clean-outs may be executed during the winter months to minimize the impact on the pond’s operation and the recreational use of surrounding areas. However, the difference in trace element concentrations of storm-water sediments between the winter and summer months has not been fully investigated because most earlier studies focused on the summer season and sediment samples were seldom collected during the winter months. In this study, sediment samples were deliberately collected during both the winter and summer seasons at the same location. Neutron activation analysis (NAA) and prompt gamma ray techniques were used to determine the trace element concentration in the sediment samples, while a laser diffraction particle size analyzer and an optical microscope were used to analyze the sizes and shap...

Distribution of trace metals in a ling ( Genypterus blacodes) fish fillet

The distribution of trace metals in a ling ( Genypterus blacodes) fish fillet was determined from ICP-MS measurements of digests prepared using nitric acid and hydrogen peroxide, followed by microwave digestion. Most trace elements were inhomogeneously distributed in the muscle tissue of the ling with a non-linear increase in concentration towards the tail end of the fillet. This distribution pattern may be connected to the size variation of the individual muscle cells or the change in the ratio of connective tissue to muscle tissue, suggesting that the observed inhomogeneity of muscle elemental distribution may be inherent to all fish species. The concentration of an element in a sample of fish muscle tissue thus depends on the physical location within the fish from which the sample was dissected. Significant differences in trace element concentrations were also detected between the red and white muscle fibres of ling, as well as between the belly flap and the rest of the musculature.

Geographic variation in natal and early larval trace-elemental signatures in the statoliths of the market squid Doryteuthis (formerly Loligo) opalescens

We found distinct geographic differences in trace element concentrations in both the core and early larval areas of the statoliths of paralarval market squid Doryteuthis (= Loligo) opalescens at sites throughout the Southern California Bight, USA. Laser ablation inductively cou- pled plasma mass spectrometry (LA-ICPMS) of individual statoliths indicated detectable levels of Mg, Mn, Sr, and Ba, with marginal levels of Cr and Pb. While these paralarvae showed considerable within-sample differences in elemental concentrations, there was significant between-site discrimi- nation of natal (core) and early larval signatures for collection sites up to 100 km apart. In 2002 and 2003, levels of Ba and Sr in the statolith cores were significantly different among sites, suggesting dif- ferences in the natal environment or local maternal effects. Site specific differences in elemental sig- natures were also apparent for Mg and Mn in samples taken from outside the core in the early post- hatching period. These same portions of the statolith can be analyzed from adult squid collected on spawning grounds. We showed that concentrations of trace elements in the statolith cores of adults closely resembled the core signatures of squid paralarvae, which opens the possibility of identifying the source populations for stocks of this commercially important species.

Major- and trace-element characterization, expanded distribution, and a new chronology for the latest Pleistocene Glacier Peak tephras in western North America

The Glacier Peak tephra beds are among the most widespread and arguably some of the most important late Pleistocene chronostratigraphic markers in western North America. These beds represent a series of closely-spaced Plinian and sub-Plinian eruptions from Glacier Peak, Washington. The two most widespread beds, Glacier Peak ‘G’ and ‘B’, are reliably distinguished by their glass major and trace element abundances. These beds are also more broadly distributed than previously considered, covering at least 550,000 and 260,000 km 2, respectively. A third bed, the Irvine bed, known only from southern Alberta, is similar in its major-element composition to the Glacier Peak G bed, but it shows considerable differences in trace element concentrations. The Irvine bed is likely considerably older than the G and B tephras and probably records an additional Plinian eruption, perhaps also from Glacier Peak but from a different magma than G through B. A review of the published radiocarbon ages, new ages in this study, and consideration in a Bayesian framework suggest that the widespread G and B beds are several hundred years older than widely assumed. Our revised age is about 11,600 14C yr BP or a calibrated age (at 2 sigma) of 13,710–13,410 cal yr BP.

Trace elements in home-produced eggs in Belgium: Levels and spatiotemporal distribution

The purpose of this study was to evaluate the levels of arsenic, cadmium, lead, copper and zinc in home-produced eggs, soils and kitchen waste samples of private chicken owners in Belgium, and to determine spatiotemporal differences in trace element contents in eggs. Eggs were sampled in all provinces of Belgium in autumn 2006 and spring 2007. A total number of 59 private chicken owners participated in the study. Trace elements were determined by inductively coupled plasma-mass spectrometry except for mercury, which was determined by atomic absorption of mercury vapour. The mean fresh weight concentrations in eggs in autumn and spring respectively were < 8.0 and < 8.0 µg/kg for arsenic, 0.5 and < 0.5 µg/kg for cadmium, 116 and 74 µg/kg for lead, 0.43 and 0.52 mg/kg for copper, 20.3 and 19.2 mg/kg for zinc, and 3.15 and 4.44 µg/kg for mercury. Analysis of variance determined significant differences in some trace element concentrations in eggs among seasons and regions in Belgium. Average concentrations of arsenic, cadmium and mercury corresponded well with values measured in other countries, while copper and zinc concentrations were within the same order of magnitude as in other countries. Average lead concentrations were high compared to concentrations in eggs from other countries and correlated well with lead concentrations in soil, indicating that the soil is an important source. Other sources of trace elements in eggs might be home-grown vegetables and forage (grass and herbs), and indirectly, air pollution.

Trace Element Distribution in Topsoils in Catalonia: Background and Reference Values and Relationship with Regional Geology

Spatial distributions of fifteen trace elements (As, Be, Cd, Co, Cr, Cu, Mo, Ni, Pb, Sb, Sn, Tl, U, V, and Zn) potentially harmful for the human health and the ecosystem have been studied in the soils of Catalonia. Geographic Information Systems were used together with the cartographic information available in sampling design. Descriptive statistics, box-plots, and cumulative distribution figures were used to assess the differences in trace element concentrations among soil uses. A clear enrichment in Pb and Sn (mean 24.3 and 3.31 mg · kg−1 d.w., respectively) in urban soils was observed when compared to other soil uses. Values obtained for country soils where similar to those observed in previous studies carried out in Europe. Trace element enrichment or impoverishment observed in the soils is consistent with the concentration in representative rock types of the underlying geology analysed in other areas. This fact indicates that geology is an important factor influencing trace element distribution in country topsoils of the region studied. Background and reference values, computed as upper confidence limits for a central tendency value and 95th percentile, respectively, were also provided to assist in the assessment of soil pollution in the region.

Bioaccumulation and distribution of trace elements in tissues of giant river prawn Macrobrachium rosenbergii (Decapoda: Palaemonidae) from South Vietnam

Accumulation profiles of 22 trace elements in abdominal muscle, abdominal exoskeleton and the hepatopancreas of the giant river prawn Macrobrachium rosenbergii were analyzed. The giant river prawn is an indigenous freshwater species from South Vietnam, and is cultured commercially and fished in the wild. Samples were collected from Ho Chi Minh City and the surrounding area (SKEZ, South Key Economic Zone), and from the Mekong River Delta between 2003 and 2005. Highest accumulations of essential (Cu, Se and Mo) and toxic (As, Ag, Cd and Hg) elements were observed in hepatopancreatic tissue, except for Mn, Sr, Sn, Ba and V in the exoskeleton and Rb and Cs in muscle tissue. Spatial differences showed concentrations of Cs and Pb in muscle and Sr in exoskeletons from the SKEZ were higher than those from the Mekong River Delta. The opposite trend was observed for Cr, Se and Sb in muscle, Mo, Sb and TI in exoskeleton, and Se, Hg, Mo, Cd, Sb, TI and Bi in the hepatopancreas. These differences in trace element concentrations in prawns likely reflect differences in industrialization and human activities between the two regions of South Vietnam.

Trace elements in edible tissues of three shrimp species (Penaeus semisulcatus, Parapenaeus longirostris and Paleomon serratus)

AbstractAccumulation levels of trace elements in edible tissues of three shrimp species (Penaeus semisulcatus, Parapenaeus longirostris and Paleomon serratus) from the Gulf of Antalya, Turkey were investigated. Copper (Cu), cadmium (Cd), zinc (Zn), iron (Fe) and manganese (Mn) concentrations were determined by atomic absorption spectrophotometry. The lowest Cu (1.33 mg kg−1) and Cd (0.23 mg kg−1) and highest Mn (1.52 mg kg−1) concentrations were found in P. longirostris, the lowest Zn (6.25 mg kg−1), Fe (1.84 mg kg−1) and Mn (0.25 mg kg−1) concentrations in P. serratus and the highest Cu (6.19 mg kg−1), Cd (2.36 mg kg−1), Zn (30.84 mg kg−1) and Fe (33.89 mg kg−1) concentrations in P. semisulcatus. The Cd levels detected in P. semisulcatus and P. serratus were above legislative limits. Our results show that there were significant differences in trace element concentrations among the three shrimp species. The highest levels of the five trace elements investigated, with the exception of Mn, were found in edible tissue of P. semisulcatus. Copyright © 2007 Society of Chemical Industry

Magmatic evolution at Batur volcanic field, Bali, Indonesia: petrological evidence for polybaric fractional crystallization and implications for caldera-forming eruptions

Batur volcanic field (BVF), in Bali, Indonesia underwent a complex evolution that comprised three periods of building and two major caldera-forming eruptions. The magmas erupted show a broad range of compositions from basaltic to rhyolitic (50–71 wt.% SiO 2) and variable phenocryst assemblages. Based on their mineralogy and geochemistry, these magmas may be assigned to four distinct suites: (1) plagioclase+olivine suite that comprises basalts only, (2) plagioclase+orthopyroxene+clinopyroxene+amphibole suite that includes andesites, (3) plagioclase+clinopyroxene+orthopyroxene suite that consists of basalts to andesites and (4) plagioclase+olivine+clinopyroxene suite with basaltic andesite to dacite magmas. Modelling indicates that the compositional variations within the various suites were produced by fractional crystallization of observed phenocryst assemblages. It also suggests that the four suites were produced by fractionation from basaltic parental magmas with similar major element compositions. Incompatible trace element ratios, however, indicate that there were significant differences in trace element contents between the parental melts, likely to reflect variable degrees of depletion of a MORB-like mantle wedge and variable degrees of metasomatism by a slab-derived component enriched in large ion lithophile elements (LILE) and light rare earth elements (LREE). Additional variations in H 2O (1–3 wt.%) within the parental melts are necessary to account for the range of phenocryst assemblages that produced the four suites. Initial variations in H 2O content combined with variable pressure of crystallization (possibly <1–7 kbar) under conditions varying from water-undersaturated to water-saturated may have produced the observed range of phenocryst assemblages and ultimately controlled the different fractionation trends. The repeated occurrence of magmas from different suites during a single period of activity suggests that the magmatic system at Batur comprised several independent conduits and reservoirs dispersed at different levels in the crust and near the mantle/crust interface. During the first building period, the plagioclase+olivine+clinopyroxene suite became progressively predominant to totally obscure the other suites during and after the caldera-forming eruptions. This is thought to reflect progressive development of a shallow magmatic system, conditions that ultimately resulted in the two catastrophic caldera-forming eruptions.

Relative Effect of Temperature and pH on Diel Cycling of Dissolved Trace Elements in Prickly Pear Creek, Montana

Diel (24 hr) cycles in dissolved metal and As concentrations have been documented in many northern Rocky Mountain streams in the U.S.A. The cause(s) of the cycles are unknown, although temperature- and pH-dependent sorption reactions have been cited as likely causes. A light/dark experiment was conducted to isolate temperature and pH as variables affecting diel metal cycles in Prickly Pear Creek, Montana. Light and dark chambers containing sediment and a strand of macrophyte were placed in the stream to simulate instream temperature oscillations. Photosynthesis-induced pH changes were allowed to proceed in the light chambers while photosynthesis was prevented in the dark chambers. Water samples were collected periodically for 22 hr in late July 2001 from all chambers and the stream. In the stream, dissolved Zn concentrations increased by 300% from late afternoon to early morning, while dissolved As concentrations exhibited the opposite pattern, increasing 33% between early morning and late afternoon. Zn and As concentrations in the light chambers showed similar, though less pronounced, diel variations. Conversely, Zn and As concentrations in the dark chambers had no obvious diel variation, indicating that light, or light-induced reactions, caused the variation. Temperature oscillations were nearly identical between light and dark chambers, strongly suggesting that temperature was not controlling the diel variations. As expected, pH was negatively correlated (P < 0.01) with dissolved Zn concentrations and positively correlated with dissolved As concentrations in both the light and dark chambers. From these experiments, photosynthesis-induced pH changes were determined to be the major cause of the diel dissolved Zn and As cycles in Prickly Pear Creek. Further research is necessary in other streams to verify that this finding is consistent among streams having large differences in trace-element concentrations and mineralogy of channel substrate.

Comparative study of trace element contents in human full-term placenta and fetal membranes by total reflection X-ray fluorescence

The total reflection X-ray fluorescence (TXRF) method was applied to study the influence of environmental pollution on the contents of trace elements in human full-term placenta and fetal membranes. The samples were collected from the donors living in two regions characterised by different levels of environmental pollution. In this comparative study, based on relatively large (∼100) populations, the concentrations of approximately 20 trace elements (P–Pb) were determined in the samples. In particular, the paper discusses the role of ‘truncation’ of measured concentration distribution by the detection limit of the TXRF method in context of comparative studies. First, the importance of the developed method of reconstruction of original concentration distribution, to derive the correct concentrations of trace elements, is described and demonstrated and, second, the statistical tests, which can be used to compare the truncated, or reconstructed, concentration distributions are discussed. Finally, the statistically significant differences of trace element concentrations found in both populations are presented and summarised.