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Disinfection by-products (DBPs) are formed in swimming pools by the reactions of bather inputs with the disinfectant. Although a wide range of molecules has been identified within DBPs, only few kinetic rates have been reported. This study investigates the kinetics of chlorine consumption, chloroform formation and dichloroacetonitrile formation caused by human releases. Since the flux and main components of human inputs have been determined and formalized through Body Fluid Analogs (BFAs), it is possible to model the DBPs formation kinetics by studying a limited number of precursor molecules. For each parameter the individual contributions of BFA components have been quantified and kinetic rates have been determined, based on reaction mechanisms proposed in the literature. With a molar consumption of 4 mol Cl2/mol, urea is confirmed as the major chlorine consumer in the BFA because of its high concentration in human releases. The higher reactivity of ammonia is however highlighted. Citric acid is responsible for most of the chloroform produced during BFA chlorination. Chloroform formation is relatively slow with a limiting rate constant determined at 5.50×10-3 L/mol/sec. L-histidine is the only precursor for dichloroacetonitrile in the BFA. This DBP is rapidly formed and its degradation by hydrolysis and by reaction with hypochlorite shortens its lifetime in the basin. Reaction rates of dichloroacetonitrile formation by L-histidine chlorination have been established based on the latest chlorination mechanisms proposed.

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Rationale Chlorine reacts in swimming pools with several compounds released by bathers to form disinfection by‐products (DBPs). Epidemiological studies have shown adverse effects on health associated with the exposure to DBPs present in indoor swimming pool atmosphere. DBPs analyses require the use of multiple techniques depending on the targeted molecules. The measurement process itself is challenging due to the low stability of several compounds and the lack of specificity of certain methods. The Membrane Introduction Mass Spectrometry (MIMS) technique provides a solution to these problems by specific and sensitive in situ measurement of DBPs. This study investigates the effect of analytical conditions on quantification of DBPs and assesses the relevance of using MIMS for reliable analysis under typical swimming pool operating conditions. Methods MIMS is based on the simultaneous permeation of the selected compounds from the air or water samples through a polydimethylsiloxane (PDMS) membrane. DBPs are identified and quantified with a quadrupole analyzer after electron ionization. Limits of quantification (LOQs) of five DBPs are determined to assess the sensitivity of the system. Moreover, signal changes are monitored while varying physicochemical parameters such as temperature, pH and ionic strength. Results The mass spectra obtained for individual molecules show that the simultaneous measurement of trihalomethanes (THMs) and chloramines requires the monitoring of several ions and mathematical corrections of the signal. The pH and ionic strength of the solution do not significantly influence the determination of THMs. On the contrary, the temperature and hydraulics at the membrane interface must be controlled for accurate determination of DBPs. Conclusions Results confirm that MIMS is a promising technology for the simultaneous quantification of volatile DBPs in both water and air of swimming pools. However, operating conditions such as membrane temperature should be treated with great care in order to avoid interferences.

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