Removing unwanted macro, micro and nanoplastics from fresh produce production

2019年全球塑料产量为3.59亿吨。在欧洲生产的6200万吨中，只有920万吨被收集用于回收，其余的被丢弃在陆地或海洋环境中，对这些生态系统造成损害。最近的研究表明，宏观塑料，例如塑料袋，随着时间的推移会分解成微米或纳米塑料颗粒。这些微观塑料已经在海洋环境中进行了调查，发现海洋野生动物，如扇贝和贻贝摄取这些塑料，它们分布在整个生物体中。然而，到目前为止，还没有在陆地环境中开展工作，以确定纳米塑料是否可以被植物根部吸收并可能进入人类食物链。由于植物的根系是用来从土壤中吸收养分和小分子的，因此这种情况很可能发生。该项目将使用扫描电子显微镜表征农作物种植环境中宏观，微观和纳米塑料的丰度和分布。该项目将在水培实验装置中使用14C放射性标记的球形纳米聚合物，该实验装置将研究植物是否可以吸收这些颗粒，并使用液体闪烁计数和磷光成像来找出它们随后在植物中的分布位置。我们选择将叶菜沙拉行业作为调查塑料污染的环境，因为企业严重依赖它来保持他们种植的作物的质量。欧洲大部分蔬菜和水果都产自西班牙南部一个名为阿尔梅里亚（Almeria）的地区，该地区每年收获270万吨农产品，面积达3万公顷，几乎所有的土地都覆盖着塑料。阿尔梅里亚的标准做法是用塑料隧道或塑料覆盖物覆盖作物，然后在作物收获时将其犁入土壤。覆盖物用于保持土壤温度足够温暖以供植物生长，防止水分蒸发损失，抑制杂草生长而不是使用除草剂，并减少土壤侵蚀。纳米塑料（<1000 nm）预计将通过重复种植含有废塑料覆盖材料的土地产生。绿叶沙拉在整个供应链中也使用塑料，以保持作物的新鲜度，防止微生物污染，并延长保质期。阿尔梅里亚生产的传统和有机种植的沙拉在英国消费的主要比例之间的九月和三月。一次性塑料在整个供应链中用于板条箱衬垫、包装托盘和产品包装。在板条箱衬垫和托盘包装的情况下，废物管理流得到了很好的控制，使大多数英国新鲜农产品企业能够声称零废物填埋。然而，用于袋装婴儿和切割沙拉叶的包装没有良好的废物管理流，公司开始探索替代品，包括可生物降解和可堆肥的包装。虽然这些概念是好的，但研究表明，这些材料的降解往往很差。需要更多的工作来开发真正可生物降解的生物基包装材料。该项目将评估生物基包装的潜力，以保持绿叶沙拉的质量和保质期，该项目将评估与塑料使用相关的不同生产和供应链实践的可持续性，并确保碳氢化合物聚合物的替代材料在以下方面有真实的改进：持续发展

Global plastics production in 2019 was 359 million tonnes. Of the 62 million tonnes produced in Europe, only 9.2 million tonnes was collected for recycling, leaving the remainder to be disposed of on land or in marine environments, to the detriment of those ecosystems. Recent work has demonstrated that macro plastics, e.g. plastic bags, break down over time into micro- or nano-plastic particles. These microscopic plastics have been investigated in the marine environment and it has been found that marine wildlife, such as scallops and mussels ingest these, and they become distributed throughout the body of the organism. However, to date, no work has been done on terrestrial environments to find out whether nano-plastics can be taken up by plant roots and potentially enter the human food chain. Since plant roots are designed to absorb nutrients and small molecules from the soil it seems likely that this could occur. This project will characterize the abundance and distribution of macro, micro and nano plastics in a crop cultivation environment using Scanning Electron Microscopy. The project will use 14C radiolabelled spherical nanopolymers in a hydroponic experimental set up that will investigate whether plants can take up these particles and find out where in the plant they are subsequently distributed, using liquid scintillation counting and phosphorimaging. We have chosen to focus on the leafy salad industry as the environment in which to investigate plastic contamination, since businesses depend heavily on it to preserve the quality of the crops they grow. Much of the European supply of vegetables and fruit is produced in a region of southern Spain called Almeria, where 2,700,000 metric tons per year of produce is harvested over a region covering 30,000 hectares, nearly all of which is covered in plastic. Standard practice in Almeria is to cover the crops in plastic tunnels or plastic mulch which is then ploughed into the soil when the crop is harvested. The mulch is used to keep the soil temperature warm enough for plant growth, to prevent evaporative water loss, to suppress weed growth instead of using herbicide, and to reduce soil erosion. Nanoplastics (<1000nm) are expected to be generated by repeated cultivation of land containing waste plastic mulching material. Leafy salads also use plastics throughout the supply chain, in order to maintain freshness of the crop, to prevent microbial contamination, and to extend shelflife. Almeria produces the major proportion of conventionally and organically grown salads consumed in the UK between September and March. Disposable plastics are used throughout the supply chain for crate liners, wrapping pallets and product packaging. In the case of crate liners and pallet wrappers, waste management streams are well controlled, enabling most UK fresh produce businesses to claim zero waste to landfill. However, packaging used for bagged baby and cut salad leaves does not have a good waste management stream and companies are starting to explore alternatives including biodegradable and compostable packaging. Although these concepts are good, research has indicated that degradation of these materials is often poor. More work is required to develop bio-based packaging materials that are truly biodegradable. The project will evaluate the potential for bio-based packaging to preserve leafy salad quality and shelf life, alongside assessing the ability of these types of packaging to degrade in different environments that reflect possible disposal routes.The project will evaluate the sustainability of different production and supply chain practices in relation to plastic use and ensure that alternative materials to hydrocarbon polymers represent a real improvement in sustainability.