高悬浮泥沙荷载和大型漂浮碎屑水生环境中 Microplastics 的取样、分类和表征
Summary
迄今为止, 大多数 microplastic 研究都发生在海洋系统中, 悬浮固体水平相对较低。重点现在转移到淡水系统, 这可能具有高泥沙负荷和漂浮的碎片。该协议涉及收集和分析含有高悬浮固体负荷的水生环境中的 microplastic 样品。
Abstract
在海洋中普遍存在的塑料碎片被公众、科学界和政府机构广泛认可。然而, 只有最近才在淡水系统, 如河流和湖泊中 microplastics, 被量化。Microplastic 抽样在表面通常包括部署漂移网在一个固定或移动的小船之后, 它限制取样对低水平悬浮的沉淀物和漂浮或被淹没的残骸的环境。以前的研究, 利用漂移网收集 microplastic 碎片通常使用网与≥300µm 网格大小, 允许塑料碎片 (颗粒和纤维) 低于这个大小, 通过网络和逃避量化。此处详述的协议使: 1) 在高悬浮荷载和漂浮或浸没碎片的环境中采集样本, 2) 对 microplastic 颗粒和纤维 < 300 µm 的捕获和定量. 用一种蠕动泵在低密度聚乙烯 (PE) 容器中储存, 然后在实验室进行过滤和分析。过滤是由一个定制的 microplastic 过滤装置, 其中包含了尼龙网状筛和混合纤维素酯膜过滤器可拆卸的联合关节。用显微镜对网筛和膜过滤器进行了定量和分离 microplastic 微粒和纤维的研究。然后用微衰减的全反射傅里叶变换红外光谱仪 (microplastic) 对这些材料进行了检测, 以确定聚合物的类型。采用蓝色 PE 微粒和绿色尼龙纤维对样品进行了峰值检测;测定颗粒物的回收率为 100%, 纤维含量为92%。该议定书将指导类似的研究 microplastics 在高浓度的河流泥沙。通过对蠕动泵和过滤装置的简单修改, 用户可以收集和分析各种样品体积和颗粒尺寸。
Introduction
最早在二十世纪三十年代1, 塑料首次在海洋中被观测到。最近对海洋塑料碎片的估计范围从海洋表面的塑料超过24.3万公吨 (mt) 到 4.8-1270万吨塑料, 每年从陆地来源进入大洋2,3。早期对海洋塑料碎片的研究侧重于 macroplastics (> 5 毫米直径), 因为它们很容易看到和量化。然而, 最近发现, macroplastics 代表 < 10% 的塑料碎片, 计数, 在海洋中, 表明绝大多数的塑料碎片是 microplastic (< 5 毫米直径)2。
Microplastics 分为两组: 初级和二级 Microplastics。主要 microplastics 由直径 < 5 毫米制造的塑料组成, 包括塑料球, 用于制造消费品的原料, 微球用作个人护理产品中的 exfoliants (例如,洗脸、身体磨砂、牙膏), 以及在工业中的磨料或润滑剂。次级 microplastics 是在环境中创建的, 因为较大的塑料碎片被光解、磨损和微生物分解4,5碎片。合成纤维也是次要的 microplastics 并且是越来越关心。一个单一的服装可以释放 > 1900 纤维每洗涤在国内洗衣机6。这些纤维, 以及个人护理产品的微珠, 在进入废水处理厂之前, 都被冲进下水道并进入排污系统。墨菲 (2016) 发现, 一个65万人口的污水处理厂将 microplastic 浓度减少了 98.4%, 从进水到出水, 但 6500万 microplastics 在废水和污泥中保持每天7。即使在处理过程中 microplastics 的比例很高, 千百万人, 可能是亿万, microplastics 通过废水处理厂每天和进入地表水在污水6,8 ,9,10,11。
由于其环境的释放, microplastics 在所有营养水平12,13,14,15的海洋生物的消化和呼吸组织中发现。它们在吸收后的影响是可变的, 有些研究没有观察到伤害, 而另一些则显示了许多影响, 如物理和化学组织损伤4,6,14,15。由于这些发现, 这一领域的兴趣在过去五年中有所增加。然而, 最近才开始对淡水系统, 如河流和湖泊中的塑料碎片 (特别是 microplastics) 进行量化研究, 或评估对居住在这些生境12、16的生物的影响, 17,18。河流是海洋中发现的塑料碎片的主要来源, 因为它们接收到含 microplastics 和 macroplastics 的废水和地表水径流。
此处详述的协议可用于收集不可行的漂移网的 microplastic 样本;具体来说, 在水生环境中, 悬浮沉积物高度集中, 像密西西比河这样的大型漂浮碎屑。密西西比河流域是世界上最大的、拥有 > 9000万人口的国家之一, 这可能使它成为海洋中最大的塑料碎片来源19,20。每年, 密西西比河平均排放735公里3的淡水到墨西哥湾, 以及高浓度的悬浮沉积物 (60 至 > 800 毫克/升) 和大碎片13,21。在密西西比河及其支流的两个深度 (即表面和0.6 深度) 收集水样, 使用蠕动泵在半透明的 1 L 低密度聚乙烯 (PE) 容器中。在实验室中, 用尼龙网筛和混合纤维素酯膜过滤器同时过滤样品, 用特制的63.5 毫米 (2.5 英寸) 聚氯乙烯 (PVC) 气缸与联合接头插入筛和过滤器22。在过滤装置中加入 PVC 联合, 可以根据需要尽可能多或少量的粒度类进行过滤。此外, 它还可用于在研究合成纤维时使用膜过滤器捕获 microplastic 碎片到亚微米尺寸。过滤后 , 样品燥 , 怀疑塑料被识别和分类从网筛和膜过滤器下的显微镜。然后用微衰减的全反射傅里叶变换红外光谱 (微型 ATR-FTIR) 研究了怀疑塑料, 以消除非合成材料或确定聚合物类型。考虑到 microplastic 颗粒和纤维的大小, 污染是司空见惯的。污染来源包括大气沉积物、衣物、田间和实验室设备以及去离子 (DI) 水资源。在整个《议定书》中包括多个步骤, 以减少来自不同来源的污染, 同时进行研究的所有阶段。
Protocol
Representative Results
Discussion
Microplastic 收集使用漂移网是传统的方法, 在海洋环境, 如泥沙和塑料浓度低, 因此需要大量的样本量。然而, 在高泥沙荷载和大型漂浮或淹没的河流中, 漂移网并不总是切实可行或安全的。此外, 在试图彻底捕获和量化 microplastic 材料 (尤其是纤维) 时, 使用漂移网是不可行的, 因为大多数用于塑料测量的网都有网格尺寸≥300µm。本文所描述的协议允许在含有高泥沙负荷的水体中进行取样, 同时允许捕获…
Offenlegungen
The authors have nothing to disclose.
Acknowledgements
该议定书建立的项目由国家海洋和大气管理局 (NOAA) 海洋碎片计划 (NA16NO29990029) 提供经费。我们感谢伊利诺伊州奥尔顿国家大河研究和教育中心 (NGRREC) 的迈尔斯. 科克伦, 以帮助选址和船上操作。现场和实验室的工作是在卡米尔. 巴克利, 迈克尔. Abegg, 和丽贝卡. 瓦格纳的帮助下完成的。
Materials
| 1L Cubitainer Containers, Low-Density Polyethylene | VWR | 89094-140 | Containers used to collect and store samples. |
| 2-1/2" Clear Schedule 40 Rigid PVC Pipe | United States Plastic Corporation | 34138 | The PVC pipe used to make the device comes as an 2.43 m pipe. The pipe was then cut to the desired lengths for each section seperated by union joints. Section lengths were decided by predicting smaller pore sizes would clogg the device quicker. Longer sections were placed above the smaller pore sizes to collect and hold water to prevent needing to disassemble the device to change a filter while a sample remained in the device. For one filtration device one 18 in, one 12 in, and two 6 in peices are needed. |
| 2-1/2" PVC SCH 40 Socket Union | Supply House | 457-025 | Union joints were glued to PVC pipe to house nylon sieves and mixed cellulose membranes. |
| Nylon 6 Woven Mesh Sheet, Opaque Off-White, 12" Width, 12" Length, 500 microns Mesh Size, 38% Open Area (Pack of 5) | Small Parts via Amazon | CMN-0500-C/5PK-05 | Mesh sheets were cut into circles to match the diameter of the outer diameter of the PVC pipe. The edges were glued to esure no fraying would occur. The glue 's diamter should not extend into the inner diameter of the PVC so that it will not be affected during filtration. |
| Nylon 6 Woven Mesh Sheet, Opaque White, 12" Width, 12" Length, 100 microns Mesh Size, 44% Open Area (Pack of 5) | Small Parts via Amazon | B0043D1TB4 | Mesh sheets were cut into circles to match the diameter of the outer diameter of the PVC pipe. The edges were glued to esure no fraying would occur. The glue 's diamter should not extend into the inner diameter of the PVC so that it will not be affected during filtration. |
| Nylon 6 Woven Mesh Sheet, Opaque White, 12" Width, 12" Length, 50 microns Mesh Size, 37% Open Area (Pack of 5) | Small Parts via Amazon | B0043D1SGA | Mesh sheets were cut into circles to match the diameter of the outer diameter of the PVC pipe. The edges were glued to esure no fraying would occur. The glue 's diamter should not extend into the inner diameter of the PVC so that it will not be affected during filtration. |
| Mixed Cellulose Ester Membrane, 0.45um, 142mm, 25/pk | VWR | 10034-914 | Mixed cellulose membrane filter with 0.45 um was used as the last filter. A large diameter was used to allow the filter to be folded into a cone to increase surface area of the filter to prevent clogging. |
| Metal Mesh Basket Tea Leaves Strainer Teapot Filter 76mm Dia 3pcs | Uxcell via Amazon | a15071600ux0260 | The mesh basket used to provide extra support for the membrane filter to prevent tearing when pressure was applied by a vacuum pump. |
| 1/2" PVC Barbed Insert Male Adapter | Supply House | 1436-005 | A vacuum adapter was added to allow vacuum filtration in the case of slow filtration due to high sediment concentration. |
| 1/2 in. O.D. x 3/8 in. I.D. x 10 ft. PVC Clear Vinyl Tube | Home Depot | 702229 | Tubing used to connect the vacuum pump to the filtration device. |
| YSI Professional Plus Multiparameter Instrument with Quatro Cable | YSI | 6050000 | Handheld meter used to measure additional water quality parameters parameters (e.g., turbidity, temperature, conductivity, pH, and dissolved oxygen (DO)). |
| 2100P Portable Turbidimeter | Hach | 4650000 | Handheld meter used to measure turbidity. |
| FEP-lined PE tubing | Geotech | 87050529 | Tubing used with perestaltic pump to collect water samples from desired depths. |
| Geopump Peristaltic Pump Series II | Geotech | 91350123 | Pump used to collected water samples. |
| MeiJi Techno EMZ-8TR Microscope | Microscope.com | EMZ8TR-PLS2 | Microscope used analyze mesh sieves and membrane filters to quanitfy suspect microsplastics. |
| Nicolet iS10 FTIR Spectrometer | Thermo Electron North America | 912A0607 | FTIR used to analyze suspect microplastics. |
| Nicolet iN5 FTIR microscope | Thermo Electron North America | 912A0895 | FTIR microscope used to analyze suspect microplastics. |
| Germanium (Ge) ATR | Thermo Electron North America | 869-174400 | Geranium ATR accessory used along with the Nicolet iN5 FTIR microscope to analyze suspect microplastic. |
| Aluminum EZ-Spot Micro Mounts (Pkg of 5) | Thermo Electron North America | 0042-545 | Microscope slides used along with the Nicolet iN5 FTIR microscope to analyze suspect microplastic. |
| Aluminum Coated Glass Sample Slides | Thermo Electron North America | 0042-544 | Microscope slides used along with the Nicolet iN5 FTIR microscope to analyze suspect microplastic. |
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