Enhanced hyporheic exchange flow around woody debris does not increase nitrate reduction in a sandy streambed

Anthropogenic nitrogen pollution is a critical problem in freshwaters. Although riverbeds are known to attenuate nitrate, it is not known if large woody debris (LWD) can increase this ecosystem service through enhanced hyporheic exchange and streambed residence time. Over a year, we monitored the surface water and pore water chemistry at 200 points along a ~50m reach of a lowland sandy stream with three natural LWD structures. We directly injected 15N-nitrate at 108 locations within the top 1.5m of the streambed to quantify in situ denitrification, anammox and dissimilatory nitrate reduction to ammonia, which, on average, contributed 85%, 10% and 5% of total nitrate reduction, respectively. Total nitrate reducing activity ranged from 0-16µM h-1 and was highest in the top 30cm of the stream bed. Depth, ambient nitrate and water residence time explained 44% of the observed variation in nitrate reduction; fastest rates were associated with slow flow and shallow depths. In autumn, when the river was in spate, nitrate reduction (in situ and laboratory measures) was enhanced around the LWD compared with non-woody areas, but this was not seen in the spring and summer. Overall, there was no significant effect of LWD on nitrate reduction rates in surrounding streambed sediments, but higher pore water nitrate concentrations and shorter residence times, close to LWD, indicated enhanced delivery of surface water into the streambed under high flow. When hyporheic exchange is too strong, overall nitrate reduction is inhibited due to short flow-paths and associated high oxygen concentrations

Ethical procedures and patient consent differ in Europe

BACKGROUND: Research ethics approvals, procedures and requirements for institutional research ethics committees vary considerably by country and by type of organisation. OBJECTIVE: To evaluate the requirements and procedures of research ethics committees, details of patient information and informed consent based on a multicentre European trial. DESIGN: Survey of European hospitals participating in the prospective observational study on chronic postsurgical pain (euCPSP) using electronic questionnaires. SETTING: Twenty-four hospitals in 11 European countries. PARTICIPANTS: From the 24 hospitals, 23 local investigators responded; 23 answers were analysed. OUTCOME MEASURES: Comparison of research ethics procedures and committee requirements from the perspective of clinical researchers. Comparison of the institutions' procedures regarding patient information and consent. Description of further details such as costs and the duration of the approval process. RESULTS: The approval process lasted from less than 2 weeks up to more than 2 months with financial fees varying between 0 and 575 €. In 20 hospitals, a patient information sheet of variable length (half page up to two pages) was provided. Requirements for patients' informed consent differed. Written informed consent was mandatory at 12, oral at 10 and no form of consent at one hospital. Details such as enough time for consideration, possibility for withdrawal and risks/benefits of participation were provided in 25 to 30% of the institutions. CONCLUSION: There is a considerable variation in the administrative requirements for approval procedures by research ethics committees in Europe. This results in variation of the extent of information and consent procedures for the patients involved