Potential bioremediation of mercury-contaminated substrate using filamentous fungi isolated from forest soil

The use of filamentous fungi in bioremediation of heavy metal contamination has been developed recently. This research aims to observe the capability of filamentous fungi isolated from forest soil for bioremediation of mercury contamination in a substrate. Six fungal strains were selected based on their capability to grow in 25 mg/L Hg2+-contaminated potato dextrose agar plates. Fungal strain KRP1 showed the highest ratio of growth diameter, 0.831, thus was chosen for further observation.Identification based on colony and cell morphology carried out by 18S rRNA analysis gave a 98%match to Aspergillus flavus strain KRP1. The fungal characteristics in mercury(Ⅱ) contamination such as range of optimum pH, optimum temperature and tolerance level were 5.5–7 and 25–35℃ and 100 mg/L respectively. The concentration of mercury in the media affected fungal growth during lag phases. The capability of the fungal strain to remove the mercury(Ⅱ) contaminant was evaluated in 100 mL sterile 10 mg/L Hg2+-contaminated potato dextrose broth media in 250 mL Erlenmeyer flasks inoculated with 108spore/mL fungal spore suspension and incubation at 30℃ for 7 days. The mercury(Ⅱ) utilization was observed for flasks shaken in a 130 r/min orbital shaker(shaken) and nonshaken flasks(static) treatments. Flasks containing contaminated media with no fungal spores were also provided as control. All treatments were done in triplicate. The strain was able to remove 97.50%and 98.73% mercury from shaken and static systems respectively. A. flavus strain KRP1 seems to have potential use in bioremediation of aqueous substrates containing mercury(Ⅱ) through a biosorption mechanism.     

Intensification level of rice farming in Myanmar: implication for its sustainable development

This study aims to estimate the intensification of rice farming in Myanmar particularly due to chemical fertilizer application, using farm-level data obtained from field surveys conducted in the 2000s. Relatively high-input rice farming was found in dry season crop in the delta zone and the double crop in well-irrigated lowlands of the central dry zone. The chemical fertilizer used there was about 88–159 kg NPK (nitrogen, N; phosphate, P₂O₅; and potash, K₂O) ha⁻¹ (76–110 kg nitrogen (N) ha⁻¹), and the average paddy yield ranged from 2.8 to 3.5 ton ha⁻¹. On the other hand, nutrient input in survey sites of rain-fed lowland was between 11 and 53 kg NPK ha⁻¹ (5 and 36 kg N ha⁻¹), and the yield ranged from 1.1 to 2.3 ton ha⁻¹. The national average of paddy yield and nutrient input of fertilizer was roughly estimated to be around 2.4 ton ha⁻¹ and 60 kg NPK ha⁻¹, respectively. A gap was observed between these calculated values and the official statistics. A comparison of fertilizer use efficiency for rice production in Myanmar with that in China and Vietnam has shown that the efficiency in Myanmar has not declined to an inappropriate level even in its intensive ones. Rice production in Myanmar has room for increasing the yield by capital intensification. Nevertheless, considering its sustainability as well as productivity, further intensification in rice farming technology in irrigated lowlands of Myanmar may neither be the best nor the only way.     

Transmission of ice-nucleating active bacteria from a prey reduces cold hardiness of a predator (Araneae: Theridiidae)

The influence of ice-nucleating active (INA) bacteria on cold hardiness of the house spider, Achaearanea tepidariorum, was determined by measuring the supercooling point (SCP) of hatchlings given either INA-bacteria-fed or bacteria-free prey (Drosophila melanogaster). Spiders that had eaten INA-bacteria-fed flies showed higher SCPs than those fed on bacteria-free flies. Through feeding, INA bacteria in the prey reduce the cold hardiness of spiders. This fact should be taken into account before using INA agents as a means of pest management.     

An Index to Determine Vulnerability of Communities in a Coastal Zone: A Case Study of Baler, Aurora, Philippines

A coastal community vulnerability index (CCVI) was constructed to evaluate the vulnerability of coastal communities (Buhangin, Pingit, Reserva, Sabang, and Zabali) in the municipality of Baler, Aurora, Philippines. This index was composed of weighted averages of seven vulnerability factors namely geographical, economic and livelihood, food security, environmental, policy and institutional, demographic, and capital good. Factor values were computed based on scores that described range of conditions that influence communities’ susceptibility to hazard effects. Among the factors evaluated, economic and livelihood, policy and institutional and food security contributed to CCVI across communities. Only small variations on CCVI values (i.e., 0.47–0.53) were observed as factor values cancelled out one another during combination process. Overall, Sabang received the highest CCVI, which was contributed mainly by geographical and demographic factors. This technique to determine factors that influenced communities’ vulnerability can provide information for local governments in enhancing policies on risk mitigation and adaptation.     

Extraction and cleanup methods of dioxins in house dust from two cities in Japan using accelerated solvent extraction and a disposable multi-layer silica-gel cartridge

A simple and rapid method for the extraction and cleanup of dioxins from house dust was developed using an accelerated solvent extraction (ASE) method and a multi-layer silica-gel cartridge. It was found that the WHO-TEQ levels of dioxins extracted from the house dust obtained by both a conventional soxhlet extraction and the ASE were almost equal, when the data obtained by both methods were compared. As for the cleanup method, a multi-layer silica-gel cartridge yielded higher dioxin recoveries than the alkaline digestion method. The average values of the dioxins in house dust from Kumagaya city and Sendai city in Japan (Sendai city is bigger than Kumagaya city with respect to the population and industry), were 15.6 pg TEQ/g (8.6-26.0 pg TEQ/g, n=5, Kumagaya city) and 16.0 pg TEQ/g (5.9-30.5 pg TEQ/g, n=5, Sendai city), respectively.     

Levels of PCDDs, PCDFs and Co-PCBs in human milk in Saitama, Japan, and epidemiological research

From 1998 to 2000, the dioxin levels were measured in the milk of 299 mothers who lived in Saitama prefecture, Japan. Factors that influenced the dioxin levels were investigated based on a questionnaire given to the milk donors at that time. It was found that the dioxin levels in the milk of the mothers who smoked were lower than those of non-smokers, and the dioxin levels were generally low in the mothers who were heavy smokers. The average dioxin levels in the milk of mothers who had been breast-fed were higher than those given formula, and there was a significant difference in the dioxin congeners. It was also found that the dioxin levels in milk of the women who regularly consumed fish and shellfish were generally higher. There was a strong correlation between summation operator TEQ and PCB126. The data suggested that PCB126 could be a useful indicator for the simplified analysis of dioxin in human milk.