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A review of the impacts of dams on the hydromorphology of tropical rivers

Chong XY, Vericat D, Batalla RJ, Teo FY, Lee KSP, Gibbins CN

Sci Total Environ, 2021 Nov 10;794:148686.
PMID: 34218154 DOI: 10.1016/j.scitotenv.2021.148686

A major programme of dam building is underway in many of the world's tropical countries. This raises the question of whether existing research is sufficient to fully understand the impacts of dams on tropical river systems. This paper provides a systematic review of what is known about the impacts of dams on river flows, sediment dynamics and geomorphic processes in tropical rivers. The review was conducted using the SCOPUS® and Web of Science® databases, with papers analysed to look for temporal and geographic patterns in published work, assess the approaches used to help understand dam impacts, and assess the nature and magnitude of impacts on the flow regimes and geomorphology ('hydromorphology') of tropical rivers. As part of the review, a meta-analysis was used to compare key impacts across different climate regions. Although research on tropical rivers remains scarce, existing work is sufficient to allow us to draw some very broad, general conclusions about the nature of hydromorphic change: tropical dams have resulted in reductions in flow variability, lower flood peaks, reductions in sediment supply and loads, and complex geomorphic adjustments that include both channel incision and aggradation at different times and downstream distances. At this general level, impacts are consistent with those observed in other climate regions. However, studies are too few and variable in their focus to determine whether some of the more specific aspects of change observed in tropical rivers (e.g. time to reach a new, adjusted state, and downstream recovery distance) differ consistently from those in other regions. The review helps stress the need for research that incorporates before-after comparisons of flow and geomorphic conditions, and for the wider application of tools available now for assessing hydromorphic change. Very few studies have considered hydromorphic processes when designing flow operational policies for tropical dams.
Incidence of vaginal erosion with different synthetic materials for suburethral sling in the treatment of Stress Urinary Incontinence: A systematic review

Sivalingam N, Teng YH, Chong XY, Low CH, Manocha SK, Intan Sabreena MS

Med J Malaysia, 2018 06;73(3):147-153.
PMID: 29962498 MyJurnal

INTRODUCTION: The aim of this systematic review is to compare the vaginal erosion rates in different synthetic materials used in suburethral slings in Tension Free Vaginal Tape (TVT-O /TOT) procedures in management of female stress urinary incontinence.
METHODS: PRISMA 2009 framework was adopted for study design. Scholarly literature search was done using MEDLINE, EMBASE, the Cochrane Library and Clinical Trials.gov using selected keywords. Five articles fulfilled the inclusion and exclusion criteria. Our main outcome of interest is to review the ideal properties of the suburethral sling, procedure of insertion and post-surgical complication following the sling insertion primarily vaginal erosion. Results were compared using one way-ANOVA test and independent T- test.
RESULTS: Total of 1725 subjects were available for analysis in the five studies. Monofilament polypropylene constituted 92.5% of the total sample size from one study alone. Polyester (n= 16/51) causes higher incidence rate of vaginal erosion compared to monofilament polypropylene (31.4 vs., 4.7; p = 0.01). There was no difference in the vaginal erosion rate between monofilament polypropylene and multifilament polypropylene (4.7 vs, 14.1; p=0.055) as well as between multifilament polypropylene and polyester (14.1 vs, 31.4; p=0.068). Although there was a marginally lower rate of vaginal erosion in TVT-O over TVT, the difference was not significant. (5.6 vs., 6.4, p=0.468). Common presentations of vaginal erosion were vaginal discharge, perineal pain and dyspareunia.
CONCLUSION: Given the limited sample size, polyester sling material appears to cause higher rates of vaginal erosion. No difference in erosion rate was seen between TVT and TVT-O.
Fulltext Bacteroides fragilis Causing Liver Abscess and Pyelonephritis

Teo PS, Chong XY, Chang CY, Deen AN, Zaid M

J Glob Infect Dis, 2024;16(1):39-40.
PMID: 38680751 DOI: 10.4103/jgid.jgid_184_23
Fulltext CH4 and N2 O emissions from smallholder agricultural systems on tropical peatlands in Southeast Asia

Jovani-Sancho AJ, O'Reilly P, Anshari G, Chong XY, Crout N, Evans CD, et al.

Glob Chang Biol, 2023 Aug;29(15):4279-4297.
PMID: 37100767 DOI: 10.1111/gcb.16747

There are limited data for greenhouse gas (GHG) emissions from smallholder agricultural systems in tropical peatlands, with data for non-CO2 emissions from human-influenced tropical peatlands particularly scarce. The aim of this study was to quantify soil CH4 and N2 O fluxes from smallholder agricultural systems on tropical peatlands in Southeast Asia and assess their environmental controls. The study was carried out in four regions in Malaysia and Indonesia. CH4 and N2 O fluxes and environmental parameters were measured in cropland, oil palm plantation, tree plantation and forest. Annual CH4 emissions (in kg CH4 ha-1 year-1 ) were: 70.7 ± 29.5, 2.1 ± 1.2, 2.1 ± 0.6 and 6.2 ± 1.9 at the forest, tree plantation, oil palm and cropland land-use classes, respectively. Annual N2 O emissions (in kg N2 O ha-1 year-1 ) were: 6.5 ± 2.8, 3.2 ± 1.2, 21.9 ± 11.4 and 33.6 ± 7.3 in the same order as above, respectively. Annual CH4 emissions were strongly determined by water table depth (WTD) and increased exponentially when annual WTD was above -25 cm. In contrast, annual N2 O emissions were strongly correlated with mean total dissolved nitrogen (TDN) in soil water, following a sigmoidal relationship, up to an apparent threshold of 10 mg N L-1 beyond which TDN seemingly ceased to be limiting for N2 O production. The new emissions data for CH4 and N2 O presented here should help to develop more robust country level 'emission factors' for the quantification of national GHG inventory reporting. The impact of TDN on N2 O emissions suggests that soil nutrient status strongly impacts emissions, and therefore, policies which reduce N-fertilisation inputs might contribute to emissions mitigation from agricultural peat landscapes. However, the most important policy intervention for reducing emissions is one that reduces the conversion of peat swamp forest to agriculture on peatlands in the first place.