Removal Effect of Coagulating Sedimentation Method on Polyethylene Microplastics in Water

Microplastic is a new kind of pollutant.It exists widely in the aquatic environment and seriously endangers the aquatic ecosystem.In this study,the coagulating sedimentation method was used to remove microplastics in water.Polyethylene(PE)was selected as the representative of microplastics,polyferric sulfate(PFS),polyaluminum chloride(PAC)and aluminum sulfate(AS)were used as coagulant,and polyacrylamide(PAM)was used as coagulant aid to study the effects of pH,coagulant concentration and sedimentation time on the removal of PE by single and composite coagulant.The results showed that when the dosage of PFS was 0.5 g/L and pH was 5.0,the removal rate could reach 82.14%,which was better than PAC and AS,indicating that PFS had better coagulation and sedimentation performance for PE;the composite coagulant of PFS+PAC+AS(1 g/L+0.2 g/L+0.2 g/L,pH was 5.0)had the highest removal rate of PE,reaching 96.06%;the removal rate of PE increased with the increase in sedimentation time,but considering that the longer sedimentation time has less contribution to the improvement of removal rate,it is recommended that 4 h is appropriate.

Symbol Error Rate Performance Analysis of Non-Orthogonal Multiple Access for Visible Light Communications

Non-orthogonal multiple access(NOMA) is considered as one of promising radio access techniques for visible light communications(VLC) in next-generation wireless communications systems.In order to provide theoretical support for designing VLC-NOMA,we derive its analytic expressions for the symbol error rate(SER).Specifically,NOMA is first incorporated with appropriate VLC to establish a VLC-NOMA framework.Afterwards,mathematical expressions of the SER for the VLC-NOMA are developed.Moreover,numerical results are provided carefully to demonstrate that the proposed VLC-NOMA scheme outperforms than state-of-the-art orthogonal frequency division multiple access(OFDMA) one in terms of SER performance.Finally,relationships between the SER performance and the number of users,power allocation coefficient and semi-angle are well investigated,which can give us a scientific guide to devise the VLC-NOMA system for achieving better SER performance.

Spatial variation in bigeye tuna Thunnus obesus size at sexual maturity in the eastern Pacific Ocean

Understanding the reproductive characteristics of a species is of crucial for accurate stock assessment and management plans to ensure sustainable fisheries.In this study,the size at 50%sexual maturity(L50)parameters in different bio-ecological provinces were estimated for bigeye tuna,Thunnus obesus,sampled from the Eastern Pacific Ocean tuna fisheries-dependent survey from 2013 to 2019.The overall sex ratio of the catch during the sampling differed significantly from 1:1.Bigeye tuna exhibit sexual dimorphism in the growth of males and females,with a clear shift in predominance from female to male with increasing sizes.In the North Pacific Sub-tropical Gyre(east)(NPST-east),North Pacific Tropical Gyre(NPTG),Pacific North Equatorial Countercurrent(PNEC),and Pacific Equatorial Divergence(PEQD),females(meals)reached sexual maturity round 102 cm(106 cm),106 cm(100 cm),125 cm(110 cm),and 113 cm(110 cm),respectively,the estimated L50 of bigeye tuna was 124.08 cm,121.97 cm,139.92 cm and 132.45 cm,respectively.The degree of populations mixing between equatorial(PNEC and PEQD)and high-latitude regions(NPST-east and NPTG)is extremely small,but it is reasonably high between the NPST-east and NPTG or PNEC and PEQD.These parameters were significantly different,suggesting the occurrence of a spatial difference in the size-at-maturity of bigeye tuna between these bio-ecological provinces.The findings of this study provide the key information for understanding the life history of bigeye tuna in the Eastern Pacific Ocean and will contribute to the conservation and sustainable yield of this species.