Biota matrix

The sampling sites are distributed along the entire basin but focusing the areas potentially polluted because of the emission of contaminant substances. Starting from 1992, the sampling sites have been extended, the list of compounds and the studied matrixes included in the network have been enlarged. Nowadays, the RCSP consists of the analysis of different compounds in water, sediments and biota from... 

SPE employing either GCB [6,25,73-75,80,81], C8 [77], C18 [82-87] or a combination of Cis- - SAX [88-91] cartridges is the most used method to determine SPC in environmental samples accompanied by detection with HPLC-FL [6,25,90], LC-MS [73-75,82,83,86], GC-MS with derivatisation [77,80,92] or capillary electrophoresis [81]. For biota samples, matrix SPE [85] or Soxhlet [91] followed by clean-up with SPE have been used to determine SPC. SPE employing GCB cartridges and further analysis by LC-MS has been used for the determination of SPDCs [73,74],... 

Ylinen et al. [53] developed an ion-pair extraction procedure employing tetrabutylamonium (TBA) counter ions for determination of PFOA in plasma and urine in combination with gas chromatography (GC) and flame ionisation detection (FID). Later on, Hansen et al. [35] improved the sensitivity of the ion-pair extraction approach using methyl tertiary butyl ether (MTBE) and by the inclusion of a filtration step to remove solids from the extract making it amenable to liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) determination. Ion-pair extraction procedure has been the basis of several procedures for biota [49,54-58] and food samples [50,59,60]. However, this method has shown to have some limitations, such as (1) co-extraction of lipids and other matrix constituents and the absence of a clean-up step to overcome the effects of matrix compounds and (2) the wide variety of recoveries observed, typically ranging. 

Dussault, . ., Balakrishnan, V.K., Solomon, K.R. and Sibley, P.K. (2009) Matrix effects on mass spectrometric determinations of four pharmaceuticals and personal care products in water, sediments and biota. Can J Chem, 87, 662-672. 

It is not always necessary or required to digest the entire sample in order to free the metals for analysis. In some cases it is not even desirable. In studies of contaminated soils, for instance, the analyte of interest may be present as a soluble salt from a pollution source, as well as also being present in the structure of the mineral crystals. The soluble form is of concern, as it is available to biota and may eventually contaminate groundwater. That in the insoluble particles is not of interest. In such cases, where the analyte is much more soluble than the matrix or where the metals included in the matrix are not of interest, an extraction process rather than complete solubilization is preferred. This is treated further in Section 5.10. 

Three general levels of complexity are recognized in matrix and media extrapolation. The simplest approach assumes that all toxicants are completely available to be taken up by the biota. In this case, no extrapolation is required. The second level of complexity requires the calculation of bioavailable fractions of toxicants, whereas at the highest level of complexity the influence of physiological responses to toxicant uptake is considered. 

With respect to exposures, there are many possible toxicants. More than 100000 chemicals exist (Commission of the European Communities, 1990), the number of possible mixtures is almost infinite, and the exposure of biota to chemicals is influenced by matrix characteristics. With respect to sensitivity and responses of biota, there is great natural variability among species and ecosystem types and in the array of conditions in which they occur. It is evident that an array of extrapolation types is needed for risk assessment. 

What properties of the matrix could act as (additional) stressors to the exposed biota For example, acid soil both influences the speciation of metals (increasing bioavailability) and may cause stress in terrestrial species such as earthworms. 

Soils are multicomponent, multiphase, open systems that sustain a myriad of interconnected chemical reactions, including those involving the soil biota. The multiphase nature of soil derives from its being a porous material whose void spaces contain air and aqueous solution. The solid matrix (which itself is multiphase), soil air, and soil solution—each is a mixture of reactive chemical compounds—hence the multicomponent nature of soil. Transformations among these compounds can be driven by flows of matter and energy to and from the vicinal atmosphere, biosphere, and hydrosphere. These external flows, as well as the chemical composition of soil, vary in both space and time over a broad range of scales. 

Contaminants in the soil compartment are associated with the soil, water, air, and biota phases present. Transport of the contaminant, therefore, can occur within the water and air phases by advection, diffusion, or dispersion, as previously described. In addition to these processes, chemicals dissolved in soil water are transported by wicking and percolation in the unsaturated zone.26 Chemicals can be transported in soil air by a process known as barometric pumping that is caused by sporadic changes in atmospheric pressure and soil-water displacement. Relevant physical properties of the soil matrix that are useful in modeling transport of a chemical include its hydraulic conductivity and tortuosity. The dif-fusivities of the chemicals in air and water are also used for this purpose. 

Bulk matrix removal aims to remove material such as lipids which can disturb final analysis. This can be performed by acid treatment of the extract or by liquid-solid chromatography. Alumina fractions of chlorophenol extracts have been purified with concentrated sulfuric acid [37,38] and it has been used to remove lipid and organic coextractives in sediment, biota, and human extracts [33,43,57,58,113,114,120,122-125]. The sulfuric acid treatment of PCDEs has been reported not to affect their recoveries [58]. 

Buser and Muller found B8-1413 (P-26), B9-1679 (P-50), and six further chlo-robornanes (TCI, TC2, TC5-TC8) in penguin tissue [120], TC8, tentatively identified as B8-806/B8-809 (P-42), was present in low amounts [120], Some of the other components may be B8-1412, B8-1414 (P-40), B8-1945 (P-41), B8-2229 (P-44), which have been identified in the same matrix [100]. Usually, in biota from the top level of the food chain B8-1413 (P-26) and B9-1679 (P-50) were most abundant. In addition, the number of toxaphene peaks decreased with increasing trophic level. The results obtained so far can be summarized as follows. Most of the toxaphene components are degradable, and only a few persistent congeners are accumulated in higher organisms. 

In topsoils, the development of redox zones is directly related to the soil volumetric water content (cm of water per cm ), as this determines the composition and activity of soil biota (Eenchel et al., 1998). Water potential is affected by both solute and matrix characteristics, which subsequently affect the ecophysio-logy of microorganisms. The soil biota which... 

GAU-Radioanalytical has participated in several intercomparison exercises for H-3 and C-14 activities in aqueous and biota samples. These results are in good agreement with the reference values (Table 4). Currently there are no commercially available natural matrix reference materials for total H-3 and therefore the analysis of spiked samples with known certified activities of H-3 is the best possible way of showing that the method is working. 

In addition to complexing metals in the aqueous phase, humic materials can also remove metals and radionuclides contained within the mineral matrix (18). The factors that control this behavior are not well understood however, it has direct implications on waste storage and containment strategies. The binding of organic and inorganic contaminants to humic substances is known to alter their bioavailability (41). Organic contaminants that are associated with humic substances are essentially unavailable for uptake by biota. In most cases studied, toxic metals associated with humic materials also have reduced uptake. With the new focus on bioremediation of polluted are as, the effect of the association of pollutants with humic materials on their phytotoxic properties must be considered, particularly for bound metals and radionuclides. 

In all but extreme climates, the upper portion of the soil profile is extensively occupied by plant roots, which remove both water and mineral nutrients. Plants and other biota (such as insects and small mammals) create extensive networks of voids often referred to as macropores, which result in a heterogeneous, biporous (i.e., there are two porosity values, for micro- and macropores), and structurally very complex material. Macropores (and pipes, which are larger, continuous macropores) can play a significant role in water transport, although the exact role of flow through macropores versus flow through the rest of the soil matrix is not completely understood. For an overview of the types and mechanisms of formation of macropores, the reader is referred to Beven and Germann (1982). 

The unit that underpins chemical measurements is the unit of amount of substance, the mole. However, in practice, as there is no mole standard, the kg is used, i.e. chemical measurements are actually traceable to the mass unit, the kg. In other words, water-related chemical measurements are based on the determination of amount of substance per mass of matrix. For solid matrices (sediment, suspended matters, biota), these are units corresponding to ultratrace (ng/kg) and trace (ftg/kg) concentrations for many organic micropollutants and trace elements, and mg/kg for major elements. For water, results should also in principle be reported in mass/kg of water but the practice is usually that they are reported as mass/volume, e.g. ng/1, pg/l or mg/1, which is already diverging from basic metrological principles. 

The role and use of reference materials are in principle well known, in particular for Certified Reference Materials (CRMs) used as calibration materials or matrix materials representing - as far as possible - real matrices used for the verification of the measurement process, or (not certified) laboratory reference materials (LRMs also known as quality control (QC) materials) used, for example, in interlaboratory studies or in the maintenance of internal quality control (control charts). Examples of reference materials relevant to WFD monitoring (water, sediment and biota) are described in the literature (Quevauviller, 1994 Quevauviller and Maier, 1999). 

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