Nature-based solutions to enhance urban flood resiliency: case study of a Thailand Smart District.

A Research through Designing approach was used to explore nature-based solutions (NbS) for flood management at the fluvial (regional) and pluvial (local) scales as part of a Smart District visioning study in a peri-urban area north of Bangkok, Thailand. The NbS visions were informed by community surveys (total n = 770) as well as in-depth, semi-structured interviews with community leaders and key stakeholders representing private sector business. Both fluvial and pluvial flooding commonly occur in the study area and the cost of damage incurred by individuals generally exceeds aid remuneration. The surveys revealed that flood insurance was not widely used as a form of resiliency to flood conditions. Furthermore, survey participants generally considered common space and green space unsatisfactory and inadequate to meet community needs. In light of these survey responses, example NbS visions were developed to address community concerns and promote well-being, while concurrently providing resiliency and improved ecosystem services through connectivity of blue and greenscapes. This case study provides a novel linkage between the concepts of NbS, Research through Designing, and Smart City/District, in exploring sustainable and resilient approaches to flood management in the context of tropical, Global South development and also provides a first step towards developing an NbS typology.

The Role of Micronutrients and Toxic Metals in the Management of Epidemics in Cambodia.

The illegal trade of wildlife in SE Asia has been identified as the likely cause of the COVID-19 pandemic. We reviewed 198 papers on the current COVID pandemic in Cambodia, diseases such as avian influenza and Nipah virus, most likely to develop into a new pandemic in Cambodia, and common features of disease that require mitigation. Artisanal goldmining uses pure mercury in the areas where wildlife is smuggled to China. Moreover, 30-40% of Cambodians are zinc deficient. High levels of arsenic in irrigation water (>1000 µg/L) are associated with very low levels of zinc in rice (5 µg/g) and rice is the primary staple food for the region. Brown rice from nine of 15 paddy fields in the arsenic zone of Cambodia had double the new guidelines of 100 µg/kg inorganic arsenic for children's food in the EU and USA. The combination of deficiencies of essential micronutrients like zinc and pervasive presence of arsenic and mercury has the potential to compromise the immunity of many Cambodians. Innovative solutions are suggested to improve micronutrient nutrition. Toxins that suppress the immune system must be better managed to reduce the virulence of pathogens. Cambodia was not likely the source of the COVID-19 but does have problems that could result in a new pandemic.

Interactions of Dimethylarsinic Acid, Total Arsenic and Zinc Affecting Rice Crop Management and Human Health in Cambodia.

BACKGROUND: In parts of Cambodia and in many other parts of the world, irrigation of rice with groundwater results in arsenic (As) accumulation in soil and rice, leading to health concerns associated with rice consumption. At times, some As is present as relatively nontoxic, non-regulated, dimethylarsinic acid (DMA). Low levels of zinc (Zn) have been found in rice from Bangladesh, Cambodia, and China where As levels in rice are high. Furthermore, there have been claims that Zn deficiency is responsible for stunting the growth of children in Cambodia and elsewhere, however in rural Asia, rice is the major source of Zn. Current data are inadequate for both Zn and DMA in Cambodian rice. OBJECTIVES: The present study aimed to provide a preliminary evaluation of the relationship between the content of Zn and DMA in rice grain in Preak Russey, an area with elevated levels of As in groundwater and to improve the management of Zn deficiency in rice. METHODS: Rice agriculture was evaluated along the Mekong River in Cambodia. Analyses for metals, total As, and As species in rice and water were conducted by inductively coupled plasma mass spectrometry. Analysis of total Zn and As in soils and total Zn in rice were analyzed using X-ray fluorescence (XRF) spectrometry. RESULTS: Rice in Preak Russey had Zn concentrations less than a third the level recommended by the United Nations World Food Programme. There was a significant (p < 0.05) negative correlation between the Zn content of rice and DMA in rice with the lowest Zn and highest DMA levels occurring near irrigation wells, the source of As. CONCLUSIONS: The highest levels of DMA in rice were associated with Zn deficiency in rice. COMPETING INTERESTS: The authors declare no competing financial interests.

Environmental and Health Implications of the Correlation Between Arsenic and Zinc Levels in Rice from an Arsenic-Rich Zone in Cambodia.

BACKGROUND: In parts of Cambodia, irrigation of rice with groundwater results in arsenic accumulation in soils and rice, leading to health concerns associated with rice consumption. In Bangladesh and China, low zinc levels in rice have been found in regions where arsenic levels in rice are high. Furthermore, there have been claims that zinc deficiency is responsible for stunting of children in Cambodia. There are limited data on zinc in Cambodian rice, but in rural Asia, rice is the major source of zinc. OBJECTIVES: To provide a preliminary evaluation of the zinc content in rice grain in Preak Russey, an area with elevated levels of arsenic. The importance of zinc in rice for infants was also assessed. METHODS: Rice cultivation was evaluated in sixty farms along the Mekong River in Cambodia. Analyses for metals, total arsenic, and arsenic species in the water and rice were conducted at the University of Ottawa, Canada by inductively coupled plasma - mass spectrometry. Analysis of total zinc and arsenic in soils were analyzed in Phnom Penh using X-ray fluorescence spectrometry (XRF). Total zinc in rice was also measured by XRF analysis. RESULTS: Rice in the Preak Russey area contained zinc with ½ to » of the 1987 Codex standard for rice in Infant Formula. Moreover, our average zinc concentration in rice samples was less than a third that recommended for zinc fortification in rice by the United Nations World Food Programme. There was a significant (α=0.05) negative correlation between the arsenic and zinc content of rice with the lowest zinc levels occurring near the irrigation wells, the source of arsenic. There was a significantly higher content of zinc in rice from farms that fertilized with cow manure. CONCLUSIONS: Handheld XRF spectrometers are useful tools for detection of zinc levels in rice. The potential for zinc deficiency in farmers in areas of Cambodia with arsenic toxicity is high. COMPETING INTERESTS: The authors declare no competing financial interests.

Modelling the washoff of pollutants in various forms from an urban catchment.

The exponential washoff model was originally developed based on observations of particulate pollutants, however, its applicability when applied to different forms of pollutants is not well understood. Data from a previous study of 6 stormwater pollutants from 126 events at 12 sites in Singapore was used for event based model parameter calibration using a Monte Carlo technique. The accuracy of the calibrated exponential washoff model was clearly best for particulate pollutant total suspended solids (TSS), and worst for dissolved pollutants Ortho-Phosphate (PO4), nitrate (NO3) and ammonium-nitrogen (NH4). Model accuracy for mixed forms of pollutants total Phosphorus (TP) and total Nitrogen (TN) were in between these two extremes. Relationships between model parameters with rainfall and flow characteristics were also investigated. Statistically significant relationships could only be found for TSS, where the total rainfall depth was identified as being the most significant variable to explain model parameter behaviour. Antecedent dry period (ADP) was shown to have little or no importance across all land uses and pollutant forms. The results showed that the model parameter behaviour could be explained only for particulate pollutants and small (≤10 ha) sub-catchments, and that replicating washoff of mixed or dissolved forms of pollutants as a fraction of solids is likely to lead to misleading results.

Groundwater Irrigation and Arsenic Speciation in Rice in Cambodia.

BACKGROUND: Arsenic bioaccumulation in rice is a global concern affecting food security and public health. OBJECTIVE: The present study examined arsenic species in rice in Cambodia to characterize health risks with rice consumption and to clarify uncertainties with Codex guidelines. METHODS: The present study collected 61 well water samples, 105 rice samples, 70 soil samples, and conducted interviews with 44 families in Preak Russey near the Bassac River and Kandal Province along the Mekong River in Cambodia. Analyses of metals, total arsenic and arsenic species were conducted in laboratories in Canada, Cambodia and Singapore. RESULTS: Unlike in Bangladesh, rice with the highest total arsenic concentrations in Cambodia contains mostly organic arsenic, dimethylarsinic acid (DMA), which is unregulated and much less toxic than inorganic arsenic. The present study found that storing surface runoff in ditches prior to irrigation can significantly reduce the arsenic concentration in rice. It is possible to remove > 95% of arsenic from groundwater prior to irrigation with natural reactions. CONCLUSIONS: The provision of high quality drinking water in 2015 to Preak Russey removed about 95% of the dietary inorganic arsenic exposure. The extremes in arsenic toxicity that are still obvious in these farmers should become less common. Rice from the site with the highest documented levels of arsenic in soils and water in Cambodia passes current Codex guidelines for arsenic. INFORMED CONSENT: Obtained. COMPETING INTERESTS: The authors declare no competing financial interests.

Effects of Arsenic, Iron and Fertilizers in Soil on Rice in Cambodia.

BACKGROUND: In parts of Cambodia, irrigation with groundwater results in arsenic accumulation in soils and rice, leading to health concerns associated with rice consumption. A high concentration of iron in groundwater can precipitate arsenic and reduce its bioavailability, however high concentrations of arsenic and iron can also reduce rice production. Furthermore, concerns have been raised about chemical contamination from inorganic fertilizers used to grow rice. The relationship between soil geochemistry and arsenic concentrations in rice is not yet fully understood. OBJECTIVES: The primary objective of this project was to investigate the relationship between arsenic concentrations in irrigation water, soil and rice collected from different sites in Cambodia. A secondary objective was to explore arsenic and phosphorus levels in fertilizer samples obtained from the study area in Cambodia. METHODS: The present study collected 61 well water samples, 105 rice samples, 70 soil samples, 11 inorganic fertilizer samples and conducted interviews with 44 families along the Mekong River in Cambodia. Analyses for metals, total arsenic, and arsenic species in the water and rice were conducted in Canada by inductively coupled plasma mass spectrometry. Analyses for metals, total arsenic and phosphorus in soils and inorganic fertilizers were conducted in Cambodia and Singapore by X-ray fluorescence. RESULTS: The concentration of arsenic in rice paddy soils was highly variable and as much as 20 times higher near the irrigation wells than in more distal areas of the paddy. Two farmers in Preak Russey had integrated soil samples with arsenic levels above the concentration associated with toxicity to rice in Taiwan (40 mg/kg) and above the Dutch concentration requiring intervention or remediation (55 mg/kg). The highest total arsenic measured in soil was 95 mg/kg. In Preak Russey, the loading of arsenic from irrigation water was 3710 times greater than the loading of arsenic from inorganic fertilizers. Half of the commercial inorganic fertilizers had less than 50% of the labelled content of phosphorus. CONCLUSIONS: Emphasis should be placed on improving the management of irrigation water, not on inactivation of arsenic in soil. The high levels of iron in groundwater mitigate arsenic toxicity, but the accumulation of iron could later result in lower rice productivity. Irrigation of rice with groundwater is not likely sustainable. To improve rice productivity, the content of phosphorus in local inorganic fertilizers must be improved to world standards. X-ray fluorescence analysis can quickly identify poor quality fertilizers. INFORMED CONSENT: Obtained. COMPETING INTERESTS: The authors declare no competing financial interests.

Spatial Distribution of Forensically Significant Blow Flies in Subfamily Luciliinae (Diptera: Calliphoridae), Chiang Mai Province, Northern Thailand: Observations and Modeling Using GIS.

Blow flies of the subfamily Luciliinae (Diptera: Calliphoridae) are one of the main forensically important subfamilies globally. In addition to being used to estimate the minimum post-mortem interval (PMImin), assuming colonization occurred after death, blow fly specimens found infesting a human corpse are used to determine if the corpse was relocated or if the individual ingested narcotics prior to death. The presence of these blow flies in a given area is strongly influenced by abiotic and biotic factors, such as temperature, elevation, and habitat. Having this information, along with geographical distributions and the characteristics of preferred habitats, is necessary to better understand the biology of this group. This study aimed to characterize the spatial distribution of Luciliinae throughout 18 sampling sites within six ecozones (disturbed mixed deciduous forest, mixed deciduous forest, mixed orchard, paddy field, lowland village, and city/town) in central Chiang Mai Province, northern Thailand over one year (May 2009⁻May 2010). The purpose of the study was to elucidate the relationship of blow fly species composition with environmental abiotic factors (e.g., temperature, relative humidity, light intensity), and to predict the distribution of the common species within this subfamily using GIS. Adult collections were performed biweekly, baited with one-day-old beef offal. A total of 2331 Luciliinae flies trapped, comprising eight species, of which the four predominant species were Hemipyrellia ligurriens (Wiedemann) (n = 1428; 61.3%), Lucilia porphyrina (Walker) (n = 381; 16.3%), Hemipyrellia pulchra (Wiedemann) (n = 293; 12.6%), and Lucilia papuensis Macquart (n = 129; 5.5%). Population density across species varied seasonally, peaking in August 2009 coinciding with the rainy season. Predicting population composition was based on a model developed with ArcGIS 9.2, which utilized environmental variables (temperature, relative humidity, and light intensity) in conjunction with abundance data. Models indicated H. ligurriens had the most widespread geographic distribution, while H. pulchra was predicted to occur largely in mixed orchards and lowland villages. Lucilia porphyrina and L. papuensis were less widespread, restricted mainly to mixed deciduous forest. This model, along with knowledge of forensic information, may be useful under certain investigations where the corpse may have been relocated.

Predicting Geographic Distribution of Forensically Significant Blow Flies of Subfamily Chrysomyinae (Diptera: Calliphoridae) in Northern Thailand.

Blow flies (Diptera: Calliphoridae) are carrion-breeding flies that are commonly used as evidence in forensic investigation. An adequate knowledge of ecological and geographical data of blow fly has a direct application in forensic science, as far as estimating time of colonization or corpse relocation. The aim of this study was to evaluate the occurrence of four species of Chrysomyinae (Chrysomya pinguis, Chrysomya chani, Chrysomya villeneuvi, and Ceylonomyia nigripes) across six land use types in central Chiang Mai, northern Thailand. Eighteen study sites were selected for sampling across three districts of Chiang Mai province (Mueang Chiang Mai, Mae Rim, and Hang Dong). Adult flies were collected every two weeks using a funnel trap baited with 1-day tainted beef offal. The predicted geographic distributions of forensically important blow fly species were modeled using the computer program ArcGIS, based on selected climatic variables (temperature, relative humidity, and light intensity) recorded at study sites. During the study period, 1298 adult flies were collected, with peak fly occurrence during summer (April⁻May). Seasonal fluctuation patterns varied depending on fly species. Climatic factors displayed diverse impact on associated fly populations. Identified species were restricted mainly to mixed deciduous forests (MDF) especially in the mountainous area. None of these flies were trapped in an urban area.

Metal Contamination in Low-Cost Jewelry and Toys in Cambodia.

BACKGROUND: The existence of lead-contaminated consumer products is a global issue. Toys and low-cost jewelry may contain toxic metals and Cambodia is known to have consumer products with toxic metals. OBJECTIVES: It is important to inform Cambodians about sources of toxic metals so that they can reduce their exposure risk, particularly for children. METHODS: Student volunteers purchased, or brought from home, low-cost jewelry and toys to either the University of Health Science or a Don Bosco Institute in Phnom Penh, Cambodia, where they were analyzed using X-ray fluorescence (XRF). The initial analysis was performed in 2011. A subset of the 2011 samples was re-analyzed in 2015 using new preparation techniques and a new x-ray fluorescence (XRF) unit. DISCUSSION: The analysis of low-cost jewelry in Phnom Penh in 2015 indicated that lead in jewelry clasps is a more serious health concern than was first perceived in 2011. Mercury, nickel, cadmium and copper were also found in toys, and occasionally these toys had been produced by well-known companies. Sources of jewelry production of samples in the present study are unknown. Lead in clasps in low-cost jewelry appeared to be the greatest risk to children in our sampling. CONCLUSION: One-third of toys and low-cost jewelry exceeded the United States and European Union guidelines for heavy metals. XRF analysis allows for rapid screening of lead and other toxic metals and could be used to reduce the sales of low-cost jewelry and toys containing toxic metals.

Leaded Paint in Cambodia-Pilot-scale Assessment.

BACKGROUND: Lead is a heavy metal that is well known to pose a threat to human health. Although the sale and use of lead paint has been banned in much of the developed world, lead is still commonly used in enamel paints in the developing world, including Cambodia. As Cambodia's economy grows, this may increase the purchase and use of lead-based paints, thus potentially exposing more of the population to the toxic effects of lead. OBJECTIVE: This study was performed to evaluate the concentration of lead in enamel paints in Cambodia using a method that is quick, effective, and cost-efficient. METHODS: A handheld X-ray fluorescence analyzer was used to evaluate 21 samples of enamel paint, including 8 replicates that were randomly purchased from three shops in Phnom Penh, Cambodia to evaluate the level of metals. All of the paint samples in the current study were manufactured in Thailand. DISCUSSION: Ninety percent of the enamel paints sampled in Cambodia exceeded the voluntary standard of 100 µg/g lead of the producing country, Thailand. The mean and median levels for lead were 11,833 µg/g, and 4,961 µg/g, respectively. CONCLUSION: Based on our pilot-scale assessment, high levels of lead appear to be common in enamel paints in Cambodia, and a fuller assessment of the situation is warranted. Import and production of such toxic products should be avoided and appropriate labeling and public warnings should be provided.

Mercury Contamination of Skin-whitening Creams in Phnom Penh, Cambodia.

BACKGROUND: In Cambodia, there is widespread use of skin-whitening creams containing levels of mercury that exceed Association of Southeast Asian Nations (ASEAN) guidelines by up to 35,000 times. Mercury in skin-whitening creams threatens to compromise the health of Cambodians. OBJECTIVES: It is important to provide essential information on sources of mercury so that Cambodians can avoid exposure to elevated levels of mercury and to support informed management of consumer goods. METHODS: Students were directed to buy selected skin-whitening creams that were then sampled with replication in 2011 and 2015 and processed with X-ray fluorescence (XRF) at the University of Health Science (UHS), Phnom Penh, Cambodia. DISCUSSION: The analysis of skin-whitening creams in Phnom Penh in 2015 was compared to analyses in 2008 and 2011 and showed that several creams produced in Asia no longer contain mercury. However, skin creams produced in Phnom Penh continue to use mercury and counterfeit products also are contaminated with mercury. Vendors occasionally identified Vietnam as a source of counterfeit products, but often the source was unknown. Mercury continues to be the metal of greatest concern in skin creams. Creams with more than 1,000 µg/g of mercury are a common cause of dermatitis (27% of cases). A new XRF analyzer was also able to detect more lead and arsenic than that used in analyses performed in 2011, and these two metals also exceeded ASEAN guidelines. Arsenic contamination also reflected the presence of bismuth in creams. CONCLUSION: Some producers of skin-whitening creams in Thailand, China and Taiwan appear to be aware of the risks of mercury contamination and have modified their products. However, other producers of skin-whitening creams continue to use mercury. XRF analysis allows for rapid screening of mercury in cosmetics and should be used to gather additional information on mercury content in cosmetics in support of public health efforts to stem the import, export and sales of skin creams containing mercury.

Impact of abiotic factor changes in blowfly, Achoetandrus rufifacies (Diptera: Calliphoridae), in northern Thailand.

Understanding how medically important flies respond to abiotic factor changes is necessary for predicting their population dynamics. In this study, we investigated the geographical distribution of the medically important blowfly, Achoetandrus rufifacies (Macquart) (Diptera: Calliphoridae), and ascertained the response to climatic and physio-environmental factors in Chiang Mai, northern Thailand. Adult fly surveys were carried out every 2 weeks from May 2009 to May 2010 at 18 systematically randomized study sites in three districts of Chiang Mai province (Mueang Chiang Mai, Mae Rim, and Hang Dong), using reconstructable funnel traps with 1-day tainted beef offal as bait. During the study period, 8,861 adult A. rufifacies were captured, with peak densities being observed at the end of winter (i.e., late February) and throughout most of the summer (May to March). Population density had a weak but significant (α = 0.05) positive correlation with temperature (r = 0.329) and light intensity (r = 0.231), and a weak but significant (α = 0.05) negative correlation with relative humidity (r = -0.236). From the six ecological land use types (disturbed mixed deciduous forest, mixed deciduous forest, mixed orchard, lowland village, city town, and paddy field), greater fly densities were observed generally in the disturbed mixed deciduous forest and lowland village, but not in the paddy fields. In conclusion, A. rufifacies are abundant from the end of winter and throughout most of the summer in northern Thailand, with population density being weakly positively correlated with temperature and light intensity, but weakly negatively correlated with relative humidity. The greatest densities of this fly species were collected in disturbed mixed deciduous forest and lowland village land uses. The prediction of annual and season specific distributions of A. rufifacies were provided in each season and all-year patterns using a co-kriging approach (ArcGIS9.2).

Patterns of ecosystem metabolism in the Tonle Sap Lake, Cambodia with links to capture fisheries.

The Tonle Sap Lake in Cambodia is a dynamic flood-pulsed ecosystem that annually increases its surface area from roughly 2,500 km(2) to over 12,500 km(2) driven by seasonal flooding from the Mekong River. This flooding is thought to structure many of the critical ecological processes, including aquatic primary and secondary productivity. The lake also has a large fishery that supports the livelihoods of nearly 2 million people. We used a state-space oxygen mass balance model and continuous dissolved oxygen measurements from four locations to provide the first estimates of gross primary productivity (GPP) and ecosystem respiration (ER) for the Tonle Sap. GPP averaged 4.1±2.3 g O2 m(-3) d(-1) with minimal differences among sites. There was a negative correlation between monthly GPP and lake level (r = 0.45) and positive correlation with turbidity (r = 0.65). ER averaged 24.9±20.0 g O2 m(-3) d(-1) but had greater than six-fold variation among sites and minimal seasonal change. Repeated hypoxia was observed at most sampling sites along with persistent net heterotrophy (GPP

Do climatic and physical factors affect populations of the blow fly Chrysomya megacephala and house fly Musca domestica?

The blow fly, Chrysomya megacephala (Fabricius), and house fly, Musca domestica L., are medically and forensically important flies. The population dynamic of these flies is essential for both control and forensical aspects. The aim of this study was to investigate the climatic and physical factors affecting the population trend of both species in Chiang Mai province, northern Thailand, using the Geographic Information System (GIS). Based on systematic random sampling, 18 study sites were selected in three districts (Mueang Chiang Mai, Mae Rim, and Hang Dong). Six land use types were involved in the study sites, i.e., disturbed mixed deciduous, mixed deciduous forest, mixed orchard, lowland village, city, and paddy field. Adult flies were sampled every 2 weeks using an in-house prototype reconstructable funnel trap. Two types of bait were used--one with fresh beef viscera for luring M. domestica and the other with 1-day tainted beef viscera for luring C. megacephala. Collections were conducted from May 2009 to May 2010, and analysis of climatic factors (temperature, relative humidity, and light intensity) was carried out. Correlation bivariate analysis was performed initially to determine the relationship between climatic factors and the number of flies. Consequently, an ordinary co-kriging approach, in ArcGIS 9.2, was performed to predict the spatial distribution of flies with land use and climatic factors as co-variables. A total of 63,158 flies were captured, with C. megacephala being the most common species collected (68.37%), while only 1.3% were M. domestica, thus proving that C. megacephala was the most abundant species in several land use types. A significantly higher number of females than males was found in both species. Fly populations can be collected throughout most of the year with a peak in late summer, which shows a positive relation to temperature but negative correlation with relative humidity. C. megacephala was predicted to be abundant in every land use type, from lowland to forested areas, while the density of house fly was association with altitude and land use types.

Field investigation of Bithynia funiculata, intermediate host of Opisthorchis viverrini in northern Thailand.

A survey of freshwater snail, Bithynia funiculata, was conducted in four locations, Doi Saket, Mueang, Saraphi and Mae Rim Districts of Chiang Mai Province, northern Thailand, between June and October, during the rainy season of 2004. A total of 2,240 snails was collected and classified into 7 families and 15 genera; of which 352 B. funiculata were obtained. B. funiculata was found most abundant in July and September. The infection rate of trematode cercariae in B. funiculata was 9.6% (19/352), while that of pleurolophocercous was 0.3% (1/352). Virgulate cercaria was the most common type, followed by lophocercous, monostome and pleurolophocercous. B. funiculata prefers habitats with clear water, which was less than 30 cm depth, temperatures between 24.48 and 31.78 degrees C, dissolved oxygen 2.03-7.66 mg/l, saturated dissolved oxygen 26.70-95.00%, conductivity 0.000-0.2642 mS/cm, turbidity 16.00-288.00 NTU and pH 6.58-7.56. Geographic Information System (GIS) analysis using loose soil mixed with clay revealed that the breeding grounds of this snail species was in the paddy fields and village environs of the Ping, Kuang and Fang river basins.