Beach litter - Total abundance (No. Items) of litter aggregated over a given period per beach - Official monitoring 2001/2022 v2023

This visualization product displays the total abundance of marine macro-litter (> 2.5cm) per beach, per 100m & to 1 survey aggregated over the period 2001 to 2020 from Marine Strategy Framework Directive (MSFD) monitoring surveys. EMODnet Chemistry included the collection of marine litter in its 3rd phase. Since the beginning of 2018, data of beach litter have been gathered and processed in the EMODnet Chemistry Marine Litter Database (MLDB). The harmonization of all the data has been the most challenging task considering the heterogeneity of the data sources, sampling protocols and reference lists used on a European scale. Preliminary processing were necessary to harmonize all the data: - Exclusion of OSPAR 1000 protocol: in order to follow the approach of OSPAR that it is not including these data anymore in the monitoring; - Selection of MSFD surveys only (exclusion of other monitoring, cleaning and research operations); - Exclusion of beaches without coordinates; - Some categories & some litter types like organic litter, small fragments (paraffin and wax; items > 2.5cm) and pollutants have been removed. The list of selected items is attached to this metadata (total abundance list). This list was created using EU Marine Beach Litter Baselines and EU Threshold Value for Macro Litter on Coastlines from JRC (these two documents are attached to this metadata); - Normalization of survey lengths to 100m & 1 survey / year: in some cases, the survey length was not exactly 100m, so in order to be able to compare the abundance of litter from different beaches a normalization is applied using this formula: Number of items (normalized by 100 m) = Number of litter per items x (100 / survey length) Then, this normalized number of items is summed to obtain the total normalized number of litter for each survey. Finally, a median is calculated over the entire period among all these total numbers of litter per 100m calculated for each survey. Sometimes the survey length was null or equal to 0. Assuming that the MSFD protocol has been applied, the length has been set at 100m in these cases. The size of each circle on this map increases with the calculated median number of marine litter per beach, per 100m & to 1 survey. The median litter abundance values displayed in the legend correspond to the 50 and 99 percentiles and the maximum value. More information is available in the attached documents. Warning: - the absence of data on the map doesn't necessarily mean that they don't exist, but that no information has been entered in the Marine Litter Database for this area. - This map was created to give an idea of the distribution of beach litter between 2001 and 2021 in a synthetic manner. NOT ALL BEACHES MAY HAVE DATA FOR THE ENTIRE PERIOD, SO IT IS NOT POSSIBLE TO MAKE A COMPARISON BETWEEN BEACHES.

本可视化产品展示了2001年至2020年间，汇总自海洋战略框架指令（Marine Strategy Framework Directive, MSFD）监测调查的每片海滩、每100米及单次调查的海洋大型垃圾（＞2.5cm）总丰度。欧洲海洋观测与数据网络化学分部（EMODnet Chemistry）在其第三阶段纳入了海洋垃圾的收集工作。自2018年初起，海滩垃圾数据已在EMODnet Chemistry海洋垃圾数据库（Marine Litter Database, MLDB）中完成收集与处理。
鉴于欧洲范围内数据源、采样方案及参考清单的异质性，对所有数据进行统一协调是本次工作最具挑战性的任务。为实现数据标准化，需开展以下预处理工作：
- 排除OSPAR 1000采样方案数据：遵循东北大西洋海洋环境保护委员会（OSPAR）不再将此类数据纳入监测的相关要求；
- 仅保留MSFD监测调查数据，排除其他监测、清理及研究作业相关数据；
- 剔除无坐标信息的海滩数据；
- 移除部分类别及垃圾类型，包括有机垃圾、小型碎片（石蜡与蜡质物品；＞2.5cm）及污染物。本次选取的垃圾项清单已附于本元数据（总丰度清单）中，该清单基于欧盟委员会联合研究中心（JRC）发布的《欧盟海滩海洋垃圾基线》与《海岸线大型垃圾欧盟阈值标准》制定（两份文件均附于本元数据）；
- 将调查长度标准化为100米，且单次调查仅统计1次：部分调查的实际采样长度并非恰好100米，为实现不同海滩垃圾丰度的横向可比，需通过以下公式完成标准化：
标准化为100米的垃圾件数 = 单位采样长度的垃圾件数 ×（100 / 实际调查长度）
随后对标准化后的垃圾件数进行求和，得到单次调查的总标准化垃圾数量。最终，针对该时段内所有单次调查得到的每100米垃圾总数量，计算其中位数。若调查长度为空或为0，鉴于已遵循MSFD采样规范，默认将其长度设为100米。
本地图上的每个圆形尺寸，随每片海滩、每100米及单次调查的海洋垃圾中位数计算值增大而增大。图例中展示的垃圾丰度中位数对应50分位数、99分位数及最大值。更多详细信息可参阅附件文档。
【警告】
1. 地图上无数据并不代表该区域不存在海洋垃圾，仅表示该区域尚未有数据录入海洋垃圾数据库；
2. 本地图旨在以综合形式展示2001年至2021年间海滩垃圾的分布情况。并非所有海滩均拥有完整监测时段的数据，因此无法在不同海滩间进行横向对比。