Bight 18 Debris Harmonized

Trash impairment of watersheds has been recognized as a worldwide environmental problem. Trash monitoring in streams and rivers is needed to understand the potential effect on freshwater habitats and examine the role of streams as a conduit for transport to marine environments. Southern California, with a population of over 22 million, is home to nearly 7,400 km of wadeable streams in watersheds spanning a variety of land uses, making it an ideal region to study the extent and magnitude of trash and trash types (plastic, metal, glass, etc.) found in southern Californias coastal watersheds and identify relationships between land use and trash. We found that 77% of southern Californias coastal stream kilometers contained trash, with an estimated stock of 7 million pieces of trash. Of the types enumerated, plastic trash was the most ubiquitous, present in 69% of stream kilometers, and the most abundant, with an estimated stock of over 4.3 million pieces of plastic. The most common items were single-use plastic containers, wrappers, and plastic bags. Urban land use was associated with the greatest extent and magnitude of trash, with levels nearly double those found in open land uses. Trash was strongly associated with indicators of human activity and development in watersheds. Road density and proximity to roads and parking lots were strongly correlated with increased trash in watersheds. This survey also suggested that management actions were having a positive effect on trash abundance. Since the previous trash survey in southern California streams in 2011-2013, a statewide ban on plastic bags was implemented and this survey found a significant decrease in bag abundance within streams in the present survey compared to the previous survey. In addition, trash in the Santa Monica Bay watershed, which implemented a trash total maximum daily load (TMDL) in 2012, saw a significant reduction in trash abundance since the last survey. Planning Documents Field Manual Sediment Quality QA Plan Assessment Reports Trash and Marine Debris Report流域垃圾污染已成为全球公认的环境问题。为了解垃圾对淡水生境的潜在影响，并厘清溪流作为污染物向海洋环境输运通道的作用，对溪流与河流中的垃圾开展监测十分必要。南加州人口超2200万，其流域内分布着近7400公里可涉水溪流，涵盖多种土地利用类型，因此是研究南加州沿海流域垃圾的分布范围、污染程度、垃圾类型（塑料、金属、玻璃等），并厘清土地利用与垃圾之间关联关系的理想区域。本研究发现，南加州沿海溪流中有77%的河段存在垃圾，预估总垃圾存量达700万件。在已统计的垃圾类型中，塑料垃圾分布最广泛，覆盖69%的溪流河段，同时也是存量最多的垃圾类型，预估塑料垃圾总量超过430万件。最常见的垃圾品类为一次性塑料容器、包装纸及塑料袋。城市土地利用类型与垃圾的分布范围及污染程度呈最强相关性，其垃圾水平几乎是开阔土地利用类型的两倍。流域内垃圾量与人类活动及开发程度的各项指标显著相关。道路密度、距道路与停车场的距离与流域内垃圾量的增加呈显著相关性。本次调查还显示，垃圾管理措施已对垃圾存量产生积极影响。自2011-2013年南加州溪流垃圾首次调查以来，全州已实施塑料袋禁令，本次调查发现，与此前的调查结果相比，溪流内塑料袋的存量已显著减少。此外，2012年实施了垃圾最大日负荷总量（total maximum daily load, TMDL）管控的圣塔莫尼卡湾流域，其垃圾存量较上次调查也出现了显著下降。规划文件、野外手册、沉积物质量保证计划、评估报告、垃圾与海洋废弃物报告