Subsea Dispersant Application records collected during the Deepwater Horizon (DWH) accident near the Mississippi Canyon block 252 wellhead from April 30 to July 22, 2010

The use of dispersants began shortly after the Deepwater Horizon (DWH) accident occurred in April of 2010, and ended shortly after the Mississippi Canyon lease block 252 (MC-252) well was capped in July 2010. The U.S. Coast Guard Federal On-Scene Coordinator (FOSC) and U.S. Environmental Protection Agency (EPA) authorized their use to disperse oil that could not be removed by other methods, with the goal of reducing the amount of oil in areas where persons were working onsite to cap and contain the well, and reducing the amount of oil that reached nearshore and shoreline habitats. Dispersants were applied underwater at the source of the leaking well, located nearly 50 miles offshore. EPA, BP, and others collected samples of water and air around the areas where dispersants were used, and along the Gulf shoreline, to determine whether any person or marine life was exposed to potentially significant levels of the dispersants or dispersed oil. This report contains information about subsurface dispersant use, and provides additional context for the posted dataset. During the Response to the DWH accident, dispersant was applied by subsurface injection into the oil plume emanating from the MC-252 well at different injection points that changed over time. Subsurface dispersant injection was one of the operational response strategies to reduce the amount of oil in the area where people were working to cap and contain the well, and to reduce the overall impact of released oil to the environment. Corexit EC9500A dispersant was injected at a known pumping rate and volume from the Subsea 7 vessel Skandi Neptune into the oil plume. Feasibility studies to evaluate the effectiveness and potential effects of subsea dispersant use were conducted between April 30 and May 15, 2010. Subsea injection continued on days and at times when it was approved for use, until the well was capped on July 15, 2010. A final subsurface release of dispersant occurred on July 22, 2010 when the discharge line was disengaged. The focus of this data posting is subsurface dispersant application records. These data have been compiled in a database that includes reporting period, average dispensing rate (gal/min), daily dispersant dispense volume, and cumulative total dispense. A map was produced to show the location of the subsurface dispersant injection. The parameters provided in this data posting for the subsurface dispersant application include: • Reporting period • Average subsurface dispersant dispensing rate during reporting period • Volume of subsurface dispersant dispensed during reporting period • Cumulative volume of subsurface dispersant dispensed.

2010年4月“深水地平线”（Deepwater Horizon, DWH）井喷事故发生后不久，分散剂便投入使用，并于2010年7月密西西比峡谷租赁区块252号（Mississippi Canyon lease block 252, MC-252）油井完成封井后不久停止使用。美国海岸警卫队现场联邦协调官（Federal On-Scene Coordinator, FOSC）与美国环境保护署（Environmental Protection Agency, EPA）授权使用分散剂，以处理无法通过其他方式清除的溢油，目标为减少现场参与封井及控井作业人员所在区域的溢油量，同时降低抵达近岸与滨岸生境的溢油量。

分散剂被注入至离岸近50英里的漏油油井源头水下区域。美国环境保护署、英国石油公司（BP）及其他相关机构在分散剂使用区域及墨西哥湾沿岸沿线采集水与空气样本，以确认是否存在人员或海洋生物暴露于潜在高浓度分散剂或分散型溢油的情况。

本报告涵盖水下分散剂使用的相关信息，并为已发布的数据集提供额外背景。在“深水地平线”事故应急处置期间，作业方通过水下注入方式，向MC-252油井产出的油羽流进行分散剂投放，不同注入点位随时间动态调整。水下分散剂注入是一项应急操作策略，旨在减少参与封井控井作业人员所在区域的溢油量，同时降低释放溢油对环境的整体影响。

Corexit EC9500A分散剂以已知泵送速率与体积，通过Subsea 7公司的“斯坎迪海王星号”（Skandi Neptune）船舶注入油羽流中。2010年4月30日至5月15日期间，研究人员开展了可行性研究，以评估水下分散剂使用的有效性及潜在影响。水下注入作业在获批使用的时段和日期持续进行，直至2010年7月15日油井完成封井。2010年7月22日，随着排放管线脱离，最后一次水下分散剂投放作业完成。

本次数据发布的核心为水下分散剂施用记录。相关数据已整理至数据库中，涵盖报告周期、平均施用速率（加仑/分钟）、当日分散剂施用总量及累计施用总量。同时还制作了一幅地图，用于展示水下分散剂注入点位的位置。本次数据发布中提供的水下分散剂施用参数包括：
• 报告周期
• 报告周期内水下分散剂平均施用速率
• 报告周期内水下分散剂施用总量
• 水下分散剂累计施用总量。