5:15 PM - 6:45 PM
[AHW22-P22] The plastic distribution patterns and fertilizer capsule occurrence along the Niigata and Yamagata prefecture seashores, Japan
Keywords:Microcapsule, Polymer-coated fertilizer, Microplastic, Macroplastic
Plastic debris pollution has become one of the emerging concerns for the marine environment. The transported plastic material from the terrestrial area is the main source of this pollution in marine systems. The types of plastic debris originated from terrestrial sources vary depending on the common activities and specific needs in a certain region or country. Modern agriculture is a common activity that releases plastic debris into the environment from plastic mulch, greenhouse film and crop protection cover. Application of polymer-coated fertilizer in paddy-fields in Japan also releases plastic debris to the field, resulting in distribution of the plastic capsules in the downstream. We have surveyed on seashores along the Japan Sea coast in Yamagata and Niigata prefectures, Japan in July 2023. In total, plastic samples were collected from 63 points in 7 areas. The plastic debris was visually collected within fixed areas along the coastline, and the results were expressed as plastic items per area.
Based on size categories, the distribution density of microplastics (MPs: > 0.5 cm) was higher than that of meso (0.5 - 2 cm) and macroplastics (> 2 cm) in all surveyed points. The average microplastic concentration was 187.2 ± 69.5 item m-2. A surveyed shore closest to the river mouth collected smaller density of MPs distribution as compared to the place where is located far from a river mouth. In comparison to the MPs, meso (41.9 ± 12.7) and macroplastics (24.5 ± 13.1) showed lower concentrations at every survey site. This distinct result of the size composition of plastic debris is probably related to the plastic degradation process during their transport. The size reduction of plastic debris due to its degradation produces MPs at the coastal areas.
Fertilizer capsules (60.52%) were the major type of plastic in the composition of plastic debris. Other types of plastic litter were distributed in the average composition as foams (19.98%), fragments (12.81%), films (4.28%), and fibers (2.42%). In addition, the distribution density of capsules ranged between 79.3 and 285.5 item m-2. The difference of the distribution density can be attributed to the areas occupied by paddy fields in the background watersheds. In conclusion, plastic debris distribution in the coastal areas of the Japan seaside is mainly caused by agricultural activities, especially the widespread use of polymer-coated fertilizer capsules in the paddy fields.
Based on size categories, the distribution density of microplastics (MPs: > 0.5 cm) was higher than that of meso (0.5 - 2 cm) and macroplastics (> 2 cm) in all surveyed points. The average microplastic concentration was 187.2 ± 69.5 item m-2. A surveyed shore closest to the river mouth collected smaller density of MPs distribution as compared to the place where is located far from a river mouth. In comparison to the MPs, meso (41.9 ± 12.7) and macroplastics (24.5 ± 13.1) showed lower concentrations at every survey site. This distinct result of the size composition of plastic debris is probably related to the plastic degradation process during their transport. The size reduction of plastic debris due to its degradation produces MPs at the coastal areas.
Fertilizer capsules (60.52%) were the major type of plastic in the composition of plastic debris. Other types of plastic litter were distributed in the average composition as foams (19.98%), fragments (12.81%), films (4.28%), and fibers (2.42%). In addition, the distribution density of capsules ranged between 79.3 and 285.5 item m-2. The difference of the distribution density can be attributed to the areas occupied by paddy fields in the background watersheds. In conclusion, plastic debris distribution in the coastal areas of the Japan seaside is mainly caused by agricultural activities, especially the widespread use of polymer-coated fertilizer capsules in the paddy fields.