In the context of climate change and urbanization, sustainable urban drainage systems (SUDS) are widely adopted measures to manage stormwater in the city on-site. However, their performance in practice often differs from modelled and laboratory-scale predictions due to the variability in properties of real sediments (in terms of size, shape, density and coagulation) compared to the silicate standard Millisil®W4. Clogging is a common source of failure.  The SediSubstrator L is a decentralized stormwater treatment device installed as a pre-treatment step to mitigate clogging in a storage and infiltration system on the Rooseveltlaan in Amsterdam. It consists of a sedimentation pipe with a flow-separating grate, the SediPipe, and a filter-adsorbent, the SediSorp+. It is purported to remove 80 % of TSS by DiBT (the technical authority in the German construction sector) test principles that use Millisil®W4 to simulate real sediments. The full-scale unit was monitored in the city throughout May-September 2022 to assess its performance.  The stormwater runoff discharged from the catchment had high concentrations of lead (54 μg/L) and zinc (790 μg/L), likely due to contact with gutters and old roofing material, amplified by the relative contribution of these roofs to the total catchment discharge (accounting for 50 % of the area contributing to runoff). The sediment (TSS) concentration was low, equivalent to 20 mg/L on average. The sediments were also light and fine—with an organic fraction of 66 % and with 78 % of diameter smaller than 63 μm. In the SediSubstrator L, the TSS removal efficiency was 34 % on average. This corresponds to an estimated caught load of 2.7 kg for this period. The removal efficiency was shown to increase with an increasing stormwater TSS concentration, with longer antecedent dry periods and with lower TSS organic fractions. Turbidity dynamics in the system suggest that while a net sequestration of solids occurs in the SediPipe, there is a resuspension of fine solids. This was observed in a camera inspection to occur from solids which settle on or near the grate. In an extreme rainfall event on September 28th 2022, water collected on the section of the street connected to the SediSubstrator, the cause of which is still subject to speculation. The observed SediSorp+ filter resistance across the summer was not indicative of gradual clogging, but an inspection showed signs of decayed organic matter throughout the full length of the filter bedas well as traces of cement in two of the four cartridges. It is possible that these two effects together with turbulent inflows prompted the acute clogging behavior. There is interest in using the SediSubstrator beyond the city of Amsterdam to reduce phosphorus loadings in the road runoff discharged to sensitive nature areas. On the Rooseveltlaan, the average total phosphorus removal efficiency was 18 % (50 % for dissolved, readily bioavailable ortho-phosphate). Interactions with settled sediments generated ortho-phosphate in the SediPipe, and fine particulate and colloidal organic phosphorus was shown remobilized in both the SediPipe and SediSorp+. The removal of ortho-phosphate in theSediSorp+ in natural rainfall was good (on average 50 %) and was shown to be consistent at different contact times (approximately 10-30 minutes).  The installed unit should be monitored over a longer time period of two years for statistical significance and to capture seasonal variation in loads. Nevertheless, the removal efficiency observed on site is consistent with the results of a sedimentation model developed according to Ferguson & Church (2004), using a stormwater sediment particle density as measured at another location in the city. Design adaptations are recommended to improve the SediSubstrator L to the conditions observed in Amsterdam: namely, better site selection, a longer SediPipe section (24 m) and a second filter stage to better capture the fine suspended solids.

Litter decomposition in soils is a microbial process linked to soil respiration, affected by soil composition as well as environmental factors such as temperature and moisture. For alpine areas in particular, these stand to vary significantly with climate change. To characterize the impacts of these projected changes on the carbon fluxes and carbon cycling in the environment, this study uses turf transplants along an altitudinal gradient in Western Norway. Warming is simulated for alpine and subalpine soils. Because the soils differ in composition, this enables the quantification of the influence of soil composition on soil litter decomposition and respiration. Decomposition is quantified using the standard Tea Bag Index (TBI) where the mass loss of buried rooibos and green tea bags over an extended period is used to model the labile and recalcitrant fraction of litter in the soil. Respiration CO2 fluxes are quantified from concentration measurements in an infrared gas analyzer (IRGA, LI-84A, LICOR) across a prescribed period and bare soil area. Results from this study show that simultaneous optimal soil moisture and temperature conditions maximize soil respiration and litter decomposition rates. These optimal ranges are 15-35% for soil moisture and the maximum measured 22 oC for temperature. However, the impacts of the conditions individually are more complex: soil moisture is positively correlated with soil respiration, while the correlation with temperature is inconclusive. Decomposition rates and stabilization factors for the Liahovden, the alpine site, consistently exceed those for Joasete, the sub-alpine site, which contains less soil organic matter (SOM) and carbon. With warming, Joasete exhibits opposing behavior to that of Liahovden: reduced decomposition rates and litter stabilization. These findings suggest that the availability of nutrients due to soil moisture and the soil composition itself are the most important factors determining the carbon emissions and cycling in the soil. Nevertheless, under coupled optimal conditions (warmer climate with soil moisture at approximately 35%), there is a clear maximum in flux. The complexity of the interrelations of soil moisture and temperature for different soil types supports further research on the topic, with more replicates and soil moisture content variation plot by plot.