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Dynamics of absorption properties of CDOM and its composition in Likas estuary, North Borneo, Malaysia

Mohd-Shazali Saiyidah Munirah, Jafar Sidik Madihah, Brewin Robert J.W., Idris Md. Suffian, Noir P. Purba

Oceanologia

2022

No. 64 (4)

583--594

Chromophoric Dissolved Organic Matter (CDOM) is a vital water constituent in aquatic ecosystems that contributes to water colour, affects light penetration, and impacts primary production. This study aims to determine the spatial and monsoonal variability of CDOM absorption properties in the Likas estuary, characterise the source of CDOM, and investigate the correlations between CDOM absorption properties and salinity. Likas estuary is a small estuary located in Kota Kinabalu city on the west coast of Sabah, facing the South China Sea. A mangrove ecosystem surrounds it with manufactured structures such as residential areas and public facilities. Surface water samples were collected at 19 stations: upstream of rivers to the river mouth and coastal area during spring tides every month, from June 2018 to July 2019, for 14-months. The distribution of aCDOM(440) in the study area is predictable as a signature in a coastal area with a decreasing gradient from the upstream towards coastal water (0.29 ± 0.19 m−1 to 1.05 ± 0.39 m−1). There are increasing spatial patterns of spectral slopes S275-295 and SR. However, S350-400 and S300-600 declined spatial gradients from the upstream to coastal water. Thus, S300-600 indicates a linear relationship between aCDOM(440), which unconventional results in coastal water. We suspect this is due to a small coverage of the study site with a distance of 0.5 m intervals of each station. This could be why the S300-600 had constant values throughout the study area (with no statistical difference between stations). In addition, S300-600 was merely varied in the stations located at the river mouth and coastal water. Based on the spectral slope ratio (SR), most of the stations located in the Darau, Inanam, and Bangka-Bangka rivers had SR values less than 1. Hence, CDOM in these stations is a terrestrial-dominated source. Therefore, from our observations during the study period, monsoonal variation could alter the source of CDOM in the study area.

Poly(L-lactic acid)/deproteinized natural rubber blends with enhanced compatibility

Mahendra I Putu, Nghia Phan Trung, Phuong Nguyen Thi Hong, Hang Tring Thi, Alias Nur Fazreen, Ismail Hanafi

Polimery

2021

T. 66, nr 2

105--111

PLLA-g-LMWNR (LMWNR – low molecular weight natural rubber) was used as a compatibilizer (1–3 wt %) of poly(L-lactic acid)/deproteinized natural rubber (PLLA/DPNR) blend (95/5 w/w). The LMWNR was prepared using TiO2/ZnO (9 : 1 w/w) and H2O2 as co-catalyst. The obtained LMWNR was grafted with 0–12 wt % maleic anhydride (LMWNR-g-MA) and then with PLLA (PLLA-g-LMWNR). A significant improvement in the mechanical properties of the PLLA/DPNR blend was found in the blend that contained 3 wt % PLLA-g-LMWNR. Scanning electron microscopy showed a decrease in the pore diameter from 5.44 to 1.56 μm. The thermal analysis of PLLA/DPNR blends showed that the Tg value of PLLA phase shifted from 63.1 to 61.4°C. These results confirmed that PLLA-g-LMWNR can enhance the compatibility of the PLLA/DPNR blend.

PLLA-g-LMWNR (LMWNR – kauczuk naturalny o małym ciężarze cząsteczkowym) stosowano jako kompatybilizator (1–3% mas.) mieszaniny PLLA/DPNR [poli(L-kwas mlekowy)/zdeprotonowany kauczuk naturalny] (95/5 w/w). LMWNR otrzymano z DPNR przy użyciu TiO2/ZnO (9 : 1 w/w) i H2O2 jako kokatalizatora, a następnie szczepiono bezwodnikiem maleinowym w ilości 0–12% mas. (LMWNR-g-MA). PLLA-g-LMWNR uzyskano w wyniku szczepienia PLLA z LMWNR-g-MA. Stwierdzono poprawę właściwości mechanicznych mieszaniny PLLA/DPNR zawierającej 3% mas. PLLA-g-LMWNR. Metodą SEM wykazano zmniejszenie średnicy porów z 5,44 do 1,56 μm. Wartość temperatury zeszklenia Tg fazy PLLA mieszaniny PLLA/DPNR, wyznaczona metodą analizy termicznej, zmniejszyła się z 63,1 do 61,4°C. Uzyskane wyniki potwierdziły, że dodatek PLLA-g-LMWNR zwiększa kompatybilność mieszaniny PLLA/DPNR.