Methodological considerations for nitrogen policies in the Netherlands including a new role for research

The Netherlands has attempted to follow EU guidelines in developing national policies to reduce pollution of groundwater by nitrates originating from (over) fertilized agricultural land. The EU has not been satisfied with these policies and this is resulting in legal conflicts. National policies have focused on nitrogen budgeting and on fertilization rates, over-simplifying the crucial role of soils during the leaching of nitrates to groundwater. As an alternative, a dynamic approach using simulation modeling is introduced as is illustrated for a study area in the Netherlands. A number of considerations for future policy directions are suggested, including requirements for research: (i) promotion of research aimed at improving and maintaining nutrient use efficiency at farm level; (ii) promotion of joint learning experiences between farmers and researchers, where farmers’ organizations could act as “research consortia”; (iii) emphasis on site and time specific management (precision agriculture) in policy development, and provision of site-specific advice via modern information and communication technologies; (iv) clearer guidelines for groundwater monitoring procedures, including additional monitoring at greater depths and consideration of groundwater quality from an appropriate regional perspective; (v) groundwater monitoring should take place at locations selected according to specific hydro-geological characteristics, rather than being executed at random and (vi) clear goals that are defined within existing and future policies at EU and international level, should allow for regional differentiation in indicators; these being the outcome of negotiations between farmers or their representatives, policy makers and researchers.     

兼氧条件下厨余垃圾发酵液作碳源的反硝化性能

在兼氧条件下,利用厨余垃圾厌氧发酵液调节反硝化系统的碳氮比（COD/TN,C/N）,并考察了其脱氮性能.结果表明,不同C/N条件下,反应系统均未出现有机物的积累,但高C/N条件下的亚硝酸盐最大积累浓度和积累速率高于低C/N;随着进水C/N的增大,反应整体脱氮率和反硝化速率不断增大,当C/N为13时,反硝化速率达到了最大值,为9.79mg/（gVSS·h）,其脱氮率超过95%;相同C/N条件下,反硝化速率和最大亚硝酸盐积累浓度均与进水硝酸盐浓度成正比.此外,实验结果表明,兼氧条件下的反硝化过程虽不易出现COD残留,但去除单位氮所需的有机物更多,且整体反硝化速率以及亚硝酸盐还原速率均低于厌氧条件.