Dataset: Floating plastic transport and accumulation in Amsterdam 2022-2023

This dataset contains data from monthly plastic monitoring efforts at twenty locations in Amsterdam between November 2022 and October 2023. The ArcGIS Survey123 application (ESRI, Redlands, California) with a customized form was used to efficiently log the observed floating plastic items in digital forms. Items at all locations were categorized using the River-OSPAR protocol, originally developed by the North Sea Foundation [1]. Two types of monitoring took place. <br>First, accumulated items were monitored at eleven locations, counting and categorizing all floating items within the most polluted 100 square meters of surface area. This area can be variable depending on the conditions during the measurement day. Additionally, the surface area does not follow any geometry rules, i.e. it can have any shape or form. We determined the monitored area by drawing polygons in Google Earth and redefined this area to capture the most polluted surface when deviating from the original surface area (Example: Figure 1a and b). <br>Second, the transport of items was monitored at nine locations, using the visual counting method to estimate plastic transport [2]. The observer counts and categorizes all floating items for a predetermined time interval and observation width on top of a bridge. Each bridge was divided into 1 to 3 segments, depending on the length of the bridge. Segments can be unequal in width by covering the distance between bridge pillars (Example: Figure 1c). Consequently, each segment covers a part of the waterway within the field of view of the observer, enabling the identification of all floating items within a given segment. Here, every segment was measured four times for five minutes every monitoring round. <br>The dataset contains one main file, 'dataset.xlsx' with six sheets:<br>1) Locations + metadata | Description of the monitored locations with identifiers, street names, type of monitoring and lat/lon coordinates<br>2) Transport (flux) data | All entries of monitored items for transport locations.<br>3) Accumulation (density) data | All entries of monitored items for accumulation locations.<br>4) Totals and top ten items | Total counts per item category, an overview of the categories and share of top ten items both summed for all locations and per location. 5) Transport calculations into IJ | Stepwise calculations from raw data to mass transport estimates in [kg/yr] into the IJ river. A short description of all calculation steps is included in this sheet. <br>6) Mass calculations for accumulation and transport, for each item category with all locations combined.<br>For sheet 2 and 3, all timestamps are in UTC. To convert to local time, the purple timestamps are UTC+1 (CET), and the green timestamps UTC+2 (CEST).<br>The dataset contains one figure, providing an example of monitoring. Figure caption: a) Top view of `accumulation' monitoring area at location NW2, (b) side-view with the same monitoring area, (c) top view of `transport' monitoring at location O1B. This bridge is divided into three segments (S1, S2, S3) which can be monitored by one or multiple observers simultaneously.<br>

本数据集涵盖2022年11月至2023年10月期间，阿姆斯特丹20个监测点位的月度塑料污染监测数据。研究采用定制化表单的ArcGIS Survey123 应用程序（ESRI，加利福尼亚州雷德兰兹市），以数字化表单高效记录观测到的漂浮塑料废弃物。所有点位的监测对象均按照由北海基金会（North Sea Foundation）制定的River-OSPAR 协议进行分类[1]。本次监测包含两类监测方案：

第一类为11个点位的累积漂浮塑料量监测：统计监测时段内污染最严重的100平方米水面范围内的所有漂浮塑料废弃物，计数并完成分类。该监测区域面积并非固定值，会随监测当日的环境条件变化；同时该区域不遵循特定几何规则，形状与边界均可灵活调整。研究人员通过谷歌地球（Google Earth）绘制多边形划定初始监测区域，若实际监测中发现区域未覆盖污染最严重的水面，则会对其进行重新划定（示例：图1a与图1b）。

第二类为9个点位的塑料迁移量监测：采用目视计数法估算塑料迁移通量[2]。观测者在桥梁上的预设观测宽度范围内，于固定时长的时间间隔内计数并分类所有漂浮塑料废弃物。根据桥梁长度，每座桥梁被划分为1至3个分段，分段宽度以桥墩间距为基准，可不均等划分（示例：图1c）。每个分段对应观测者视野范围内的一段航道，可识别该分段内的所有漂浮塑料废弃物。本次监测中，每个分段在每一轮监测中均开展4次时长为5分钟的观测。

本数据集包含一个主文件'dataset.xlsx'，内含6个工作表：
1) 点位与元数据：记录监测点位的标识符、街道名称、监测类型及经纬度坐标
2) 迁移（通量）数据：迁移监测点位的全部塑料监测条目
3) 累积（密度）数据：累积监测点位的全部塑料监测条目
4) 总量与前十高频品类：按品类统计的总计数，以及全点位及单点位下的品类占比与前十高频品类概览
5) 流入IJ河的迁移量计算：从原始数据到以kg/yr为单位的流入IJ河质量通量估算值的分步计算流程，本工作表附全部计算步骤的简要说明
6) 累积与迁移的质量计算：合并所有点位后，按品类划分的累积与迁移质量计算结果

工作表2与工作表3中的所有时间戳均采用UTC（协调世界时）格式。如需转换为当地时间，紫色时间戳对应UTC+1（中欧标准时间CET），绿色时间戳对应UTC+2（中欧夏令时CEST）。

本数据集附带一张示意图，展示监测示例。图注如下：(a) NW2点位「累积」监测区域俯视图；(b) 同一监测区域的侧视图；(c) O1B点位「迁移」监测俯视图，该桥梁被划分为S1、S2、S3三个分段，可由一名或多名观测者同时开展监测。