In recent years, careless accidents of field workers in situations where hard labor is often placed, such as construction sites, and excessive physical burden associated with work has been regarded as problems. At these civil engineering and construction sites, it is regarded that many accidents and injuries are caused by fatigue. As a method for evaluating fatigue, measurement of heart rate and blood pressure with a smartwatch is generally used, but the measurement of these methods differs greatly depending on individual differences. It is difficult to measure fatigue appropriately. Therefore, in this study, we applied the detection of three-dimensional center of gravity (D3DCG) to bodies under walking conditions. D3DCG calculates the position of the center of gravity of the bodies (C.O.G.) from the frequency of heaving and rolling in walking motions. We conducted experiments of long-distance walking by subjects who differ the distinction of age and sex. The subjects walked in hours on smooth surface and rough surface measuring the motions. Results of calculations by D3DCG showed that there were three different C.O.G.s found in the bodies by which fatigue of walking may be measured. When the fatigue accumulated, each amplitude of the three C.O.G.s changed accordingly to balance the bodies against the fatigue. Degree of the change was quicker on the rough surface than on the smooth surface.

　近年，地球環境問題の1つとしてマイクロプラスチック（以降，MP）への関心が高まっている．このような中，海浜に存在するMPの実態を把握することは，その動態を把握するための重要な項目の1つであるが，同一海浜内のMP分布変動を詳細に検討した調査はまだ少ない．本研究では神奈川県藤沢海岸片瀬西浜地区にて，径0.5～5.0mmの大きさのMPを対象とした空間分布調査を2019年春先と同年秋において実施し，MPの分布変化とその要因について検討を行った．その結果，対象海岸では平均93個/m²のMPが採取され，また，同一海浜内においても海側，中央，陸側によって分布に差があり，MPの移動は風速場により影響を受けやすいことが示唆された．加えて，径0.85～5.0mmのMPを対象とした簡易回収実験を行ったところ，砂に混在した状態から90%以上のMPを回収できることがわかった．