Dynamics of nitrate-nitrogen removal in experimental stormwater biofilters under intermittent wetting and drying

High concentrations of nitrate-nitrogen degrade the quality of aquatic environments. The primary mechanism by which nitrate-nitrogen is removed (denitrification) requires anoxic conditions and electron donors. While removal of total and ammonium-nitrogen is often high in stormwater biofilters, poor removal or even the release of nitrate-nitrogen in the outflow has often been observed. Five Perspex biofilter columns (94 mm internal diameter) were fabricated with a filter layer that contained 8% organic material. Columns were operated at 875  mm/h 875  mm/h and fed with simulated stormwater with different antecedent dry days (ADDs) and concentrations of nitrate-nitrogen. Samples were collected from the outflow at different time intervals between 2 and 150 min and were tested for nitrate-nitrogen. The removal of nitrate-nitrogen varied during an event from a high removal percentage (60–90%) in the initial outflow that gradually decreased in the first 30 min and settled at 0–15% removal thereafter. This remained consistent during all simulated events independent of the number of ADDs or inflow concentrations. ADDs and previous event feed concentrations affected the outflow nitrate-nitrogen concentration in the first 30 min of the current event. Therefore, from this study it is concluded that denitrification within stormwater biofilters occurs mainly during drying periods rather than wetting periods.

Tax compliance and psychic costs: Behavioral experimental evidence using a physiological marker

Although paying taxes is a key element of a well-functioning society, there is still limited understanding as to why people actually pay their taxes. Models emphasizing that taxpayers make strategic, financially motivated compliance decisions seemingly assume an overly restrictive view of human nature. Law abidance may be more accurately explained by social norms, a concept that has gained growing importance as research attempts to understand the tax compliance puzzle. This study analyzes the influence of psychic stress generated by the possibility of breaking social norms in the tax compliance context. We measure psychic stress using heart rate variability (HRV), which captures the psychobiological or neural equivalents of psychic stress that may arise from the contemplation of real or imagined actions, producing immediate physiologic discomfort. The results of our laboratory experiments provide empirical evidence of a positive correlation between psychic stress and tax compliance, thus underscoring the importance of moral sentiments for tax compliance. We also identify three distinct types of individuals who differ in their levels of psychic stress, tax morale, and tax compliance.

How social preferences shape incentives in (experimental) markets for credence goods

Credence goods markets suffer from inefficiencies caused by superior information of sellers about the surplus-maximising quality. While standard theory predicts that equal mark-up prices solve the credence goods problem if customers can verify the quality received, experimental evidence indicates the opposite. We identify a lack of robustness with respect to heterogeneity in social preferences as a possible cause of this and conduct new experiments that allow for parsimonious identification of sellers’ social preference types. Our results confirm the assumed heterogeneity in social preferences and provide strong support for our explanation of the failure of verifiability to increase efficiency.