Uusia kemian analyiikan työkaluja veden laadun seurantaan – Kentältä laboratorioon

Väitekirja elektrooniline versioon ei sisalda publikatsioone.Käesolevas töös pakutakse välja metodoloogiline „tööriistakomplekt“ veekvaliteedi monitoorimiseks. Loodud on tarkvara mõõtemääramatuse hindamiseks nn Nordtest’i metodoloogia (Nordtest TR 537) abil, samuti abivahend reaalajas toimuvate sensor-mõõtmiste mõõtemääramatuse hindamiseks. „Tööriistakastis“ on ka näited konkreetsetes analüüsiolukordades tulemuste usaldusväärsuse tõstmise kohta kasutades kvaliteedikontrolli protseduure: lahustunud hapniku sisalduse määramiseks on välja pakutud vee küllastamisel põhinev referentsmaterjal, elavhõbeda määramiseks on välja pakutud 196Hg isotoobil põhinev sisestandard ning kasutavate klaasnõude pinna silüleerimine. Pädevuskatsed on väga olulised mõõtetulemuste kvaliteedi tagamisel. Töös on uuritud nende korraldamise parimaid mooduseid. Üks tuleviku jaoks olulisi lähenemisi monitoorimisel on nn „crowdsourcing”, mis põhineb kodanike kaasamisel keskkonnamonitooringusse. Seda trendi edendab käesoleva töö raames välja arendatud innovatiivne hägususe mõõtesüsteem. Välja pakutud „tööriistad“ on konkreetsed ja mitmed neist on lihtsasti kasutatavad, võimaldades nii uudseid andmekogumise mooduseid kui ka keskkonnamonitooringus kasutatavate analüüsitulemuste kvaliteedi tõusu.This work introduces a set of new tools for enhancing quality of analytical results in water monitoring. These include tutorial computer software aimed for chemical laboratories for estimation of measurement uncertainty mainly based on the approach described in Nordtest TR 537. Also a novel tool for a real-time uncertainty estimation procedure of a field sensor on-line measurement is presented. The toolbox includes also individual examples of improving the reliability of analytical results by enhanced quality control procedures. These include an application of “in-house” reference material for DO measurement. For mercury, enriched stable 196Hg isotope is applied for monitoring the stability of total mercury in water samples. A glass surface silylation procedure is applied for minimising mercury losses and contamination. Also proper organisation of proficiency tests for field sensor measurements of selected inorganic parameters is investigated. One of the tools for future water quality monitoring is based on crowdsourcing, where citizens’ observations are applied. This trend is promoted by validating an innovative measuring system for water turbidity field measurements. The presented tools are concrete and many of them are fairly easy to apply at same time enabling new ways to produce monitoring data and raising the level of quality of environmental monitoring

Automatic real-time uncertainty estimation for online measurements : a case study on water turbidity

Continuous sensor measurements are becoming an important tool in environmental monitoring. However, the reliability of field measurements is still too often unknown, evaluated only through comparisons with laboratory methods or based on sometimes unrealistic information from the measuring device manufacturers. A water turbidity measurement system with automatic reference sample measurement and measurement uncertainty estimation was constructed and operated in laboratory conditions to test an approach that utilizes validation and quality control data for automatic measurement uncertainty estimation. Using validation and quality control data for measurement uncertainty estimation is a common practice in laboratories and, if applied to field measurements, could be a way to enhance the usability of field sensor measurements. The measurement system investigated performed replicate measurements of turbidity in river water and measured synthetic turbidity reference solutions at given intervals during the testing period. Measurement uncertainties were calculated for the results using AutoMUkit software and uncertainties were attached to appropriate results. The measurement results correlated well (R2 = 0.99) with laboratory results and the calculated measurement uncertainties were 0.8–2.1 formazin nephelometric units (FNU) (k = 2) for 1.2–5 FNU range and 11–27% (k = 2) for 5–40 FNU range. The measurement uncertainty estimation settings (such as measurement range selected and a number of replicates) provided by the user have a significant effect on the calculated measurement uncertainties. More research is needed especially on finding suitable measurement uncertainty estimation intervals for different field conditions. The approach presented is also applicable for other online measurements besides turbidity within limits set by available measurement devices and stable reference solutions. Potentially interesting areas of application could be the measurement of conductivity, pH, chemical oxygen demand (COD)/total organic carbon (TOC), or metals