Soil-based on-site wastewater treatment systems (OWSs) are suspected to contribute to eutrophication of surface waters, due to the discharge of phosphorus (P). However, along the flow path between the facilities and surface waters, different processes contribute to delay the transport of phosphorus through the ground. This may reduce the unwanted impact on receiving water bodies. However, the strength and significance of this so-called soil retention remains unclear. In Sweden, there are nearly one million OWSs. To protect surface waters, a high P removal rate (up to 90%) is often required by the local municipalities. However, since these requirements may have costly consequences to property owners, it is debated as to whether they are too strict. In this debate, it is often claimed that the retention of P occurring in natural environments may be underestimated by authorities. Accordingly, there is a need for a scrutiny of the available evidence related to soil retention of phosphorus from OWSs. This is the objective of the planned systematic map. Focus will be on boreal and temperate climate zones. Searches will be made for peer-reviewed articles and grey literature using bibliographic databases, search engines, specialist websites and stakeholder contacts. The references will be screened for relevance according to a predefined set of eligibility criteria. At stage one, after testing and clarifying the eligibility criteria, the references will be single-screened based on title and abstract. At stage two, potentially relevant references will be screened in full-text independently by two reviewers. We will compile a detailed database of the relevant studies. Moreover, a narrative report will be produced, describing the research landscape in general terms. This will be carried out with a conceptual model, describing the processes involved in P retention in natural environments, as a foundation. It will be discussed where the respective studies/study types fit into the conceptual model, and also evaluated how each study/study type can be related to the overarching question of eutrophication. Moreover, we will describe identified knowledge gaps that warrant further primary research effort, as well as identified knowledge clusters that could be suitable for systematic reviews.

中文翻译：

---

有哪些证据与北方和温带气候区现场废水处理系统中磷的土壤截留有关？系统的地图协议

怀疑土壤中的现场废水处理系统（OWSs）由于磷（P）的排放而导致地表水富营养化。然而，沿着设施和地表水之间的流动路径，不同的过程会延迟磷通过地面的运输。这可以减少对接收水体的有害影响。然而，这种所谓的土壤保持性的强度和重要性仍不清楚。在瑞典，有将近一百万的OWS。为了保护地表水，当地市政部门通常要求高P去除率（高达90％）。但是，由于这些要求可能会对财产所有者造成高昂的后果，因此就它们是否过于严格进行了辩论。在这场辩论中 人们常常声称，当局可能低估了自然环境中磷的保留。因此，需要检查与OWS中磷的土壤保留有关的可用证据。这是计划的系统地图的目标。重点将放在北方和温带气候区。将使用书目数据库，搜索引擎，专业网站和利益相关者联系人搜索经过同行评审的文章和灰色文献。将根据一组预定义的资格标准来筛选参考文献的相关性。在第一阶段，在测试并明确了资格标准之后，将根据标题和摘要对参考文献进行单筛选。在第二阶段，将由两名审阅者对全文中的潜在相关参考文献进行筛选。我们将汇编有关研究的详细数据库。此外，还将制作一个叙述性报告，以一般性术语描述研究前景。这将以概念模型为基础来进行，该模型描述自然环境中P保留所涉及的过程。将讨论各个研究/研究类型适合概念模型的位置，并评估每种研究/研究类型如何与富营养化这一总体问题相关。此外，我们将描述需要进一步开展基础研究工作的已识别知识差距，以及可能适用于系统评价的已识别知识集群。这将以概念模型为基础来进行，该模型描述自然环境中P保留所涉及的过程。将讨论各个研究/研究类型适合概念模型的位置，并评估每种研究/研究类型如何与富营养化这一总体问题相关。此外，我们将描述需要进一步开展基础研究工作的已识别知识差距，以及可能适用于系统评价的已识别知识集群。这将以概念模型为基础来进行，该模型描述自然环境中P保留所涉及的过程。将讨论各个研究/研究类型适合概念模型的位置，并评估每种研究/研究类型如何与富营养化这一总体问题相关。此外，我们将描述需要进一步开展基础研究工作的已识别知识差距，以及可能适用于系统评价的已识别知识集群。