Grip op beekslib : hoe meer aandacht voor slib de KRW-doelen dichterbij kan brengen

In veel beken worden ecologische KRW- en Natura2000-doelen voor waterplanten en vegetatie niet gehaald. De meeste doelsoorten prefereren matig voedselrijke omstandigheden, soms in combinatie met zacht, bicarbonaatarm water. Hoewel de fosfaatconcentratie in het oppervlaktewater van beken wel omlaag gebracht is, heeft dit op plekken met slibophoping niet geleid tot voldoende verbetering. Woekerende waterplanten kunnen gebruik maken van nutriënten en koolstof uit het slib, waarmee ze door hun snelle groei een betere concurrentiepositie hebbenten opzichte van veel doelsoorten. Dit vraagt om een aanpak waarin de rol van slib erkend wordt en sedimentatie van voedselrijk slib in beken wordt verminderd

Research on key technologies of multi-dimensional resource cooperative allocation for a super base station system

To meet the ever increasing demand for high wireless transmission data rates, more and more base stations (BSs) need to be deployed in current cell-centric cellular networks to increase the system capacity. This brings big challenges to mobile operators such as increased power consumption and low BS resource utilization. To solve these problems, a new centralized cellular network architecture, the super BS, is proposed by the Institute of Computing Technology, Chinese Academy of Sciences. In this architecture, large scale centralized BS resource pools are constructed, where multi-dimensional radio resource as well as the computing resource can be dynamically shared and managed across the whole network. Thus one of the key issues is how to efficiently allocate radio resource and computing resource in the super BS system. This thesis focuses on cooperative multi-dimensional resource allocation in the super BS system. A global centralized radio resource allocation algorithm based on adaptive soft frequency reuse (ASFR) is proposed, so that the system throughput is maximized. As the system traffic load fluctuates dramatically in both time and spatial domains, to avoid the high system computing overhead caused by frequent global resource allocation adjustment, a traffic aware radio resource allocation algorithm (TA-SFR) with regional optimization is then proposed. Simulation results show that both the ASFR and TA-SFR achieve a higher system throughput than traditional fixed allocation schemes. To improve system computing resource utilization, dynamic computing resource allocation algorithms are further proposed, based on an improved first fit decreasing method (IFFD), and the heuristic and simulated annealing method (HSA). Simulation results show that compared to the fixed allocation in traditional cellular networks, the IFFD and HSA effectively decrease system power consumption by 40%-65% with high traffic load and 70%-100% with low traffic load

Effects of Groundwater Nitrate and Sulphate Enrichment on Groundwater-Fed Mires: A Case Study

Mires and peatlands in general are heavily influenced by anthropogenic stressors like acidification, eutrophication, desiccation and fragmentation. Groundwater-fed mires are, in contrast to rainwater-fed mires, often well protected against desiccation due to constant groundwater discharge. Groundwater-fed mires can however be influenced by groundwater pollution such as groundwater nitrate enrichment, a threat which has received minor attention in literature. The present case study demonstrates how groundwater nitrate enrichment can affect the biogeochemical functioning and vegetation composition of groundwater-fed mires through direct nitrogen enrichment and indirect nitrate-induced sulphate mobilisation from geological deposits. Biogeochemical and ecohydrological analyses suggest that the Dutch groundwater-fed mire studied is influenced by different water sources (rainwater; groundwater of local and regional origin) with differing chemical compositions. The weakly buffered and nitrate-enriched groundwater leads, where it reaches the uppermost peat, to nitrogen enrichment, enhanced isotopic nitrogen signatures and altered the vegetation composition at the expense of characteristic species. Nitrate-induced sulphate mobilisation in the aquifer led to enhanced sulphate reduction, sulphide toxicity and elemental sulphur deposition in the mire. Despite sulphate reduction and nitrate enrichment, internal eutrophication did not play an important role, due to relatively low phosphorus concentrations and/or low iron-bound phosphorus of the peat soil. Future management of groundwater-fed mires in nitrate-polluted aquifers should include the reduction of nitrate leaching to the aquifer at the recharge areas by management and ecohydrological restoration measures on both a local and landscape scale