ISO 22190:2020 pdf free

ISO 22190:2020 pdf free.Soil quality – Use of extracts for the assessment of bioavailability of trace elements in soils
The subdivision in terms of dissolved/actual and potential bioavailability is important, because it broadens the role of the pore water. Bioavailable is not only the amount in the pore water, but may include the amount that desorbs during the time an organism is in contact with the soil. Regarding the organisms a “bio-influenced” zone could be defined[3]. This zone comprises the pore water and depending on the organism, parts of the soil matrix. Consequently, the available amount may have different values. Thus, there could be numerous bioavailabilities depending on the type of target organisms and time scale and, in turn, there could be numerous specific definitions (operational definition).
For regulatory purposes simple and cheap methods are required and a simple extraction that simulates the pore water quality is desirable. A neutral aqueous solution (i.e., limiting changes of the soil pH during extraction as much as possible) can be used for this purpose. The concentration of trace element measured in a neutral extract is assumed to reflect the concentration in the pore water [as well as ionic strength, temperature, pH, DOC (Dissolved Organic Carbon)]. These properties may show a variation during the year and can be influenced by external factors (e.g., rain, drought, addition of manure).
Extraction of a soil sample with demineralised water may have impact on the soil. For the purpose of estimating the actual availability of trace elements, it is desirable to reduce the influence of external factors and to obtain data that are more independent of the time of sampling. Extraction procedures have been developed using aqueous solutions containing a fixed concentration of a specific salt (neutral extract) in order to simulate the soil pore water.
Consequently, soil extracts could not be correlated with trace element uptake by soil organisms in numerous studies. Situations in which the measuring results of soil extracts are not a proper predictor of trace element bioavailability are described for accumulation in plants (see References [19], [22] and [23]) and accumulation in soil organisms (see References [24], [25] and [26]). In these cases, the use of biological methods for a more direct assessment of trace element bioavailability is required.ISO 22190 pdf free download.