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1.
Arsenic contamination occurs in groundwater of Bangladesh mainly from the alluvial and deltaic sediments. Arsenic contamination of groundwater in Bangladesh was first detected more than a decade ago and the ’shallow tubewells’ were reported as the main source of arsenic contaminated water. From the nutritional and metabolic points of view, arsenic is likely to adversely affect human health and nutrition. Up to now, several studies have been carried out on this context; however, inadequate knowledge on arsenic sources, mobilization and transport still remains as a constraint due to lack of data, information and technological advances. Thus, a review study has been undertaken on the sources of arsenic, its causes, mobilization, transport, effects on human health, arsenic test procedures and removal methods, in the context of groundwater contamination in Bangladesh, and finally sustainable remedial measures of arsenic have been proposed. This study suggests that laboratory facilities for testing of arsenic and effects of enhanced groundwater pumping, phosphate fertilizer etc., need to be updated, expanded and studied. This review work is significant to further knowledge improvement, as the topic is general and worldwide. It can be concluded that the integration of the proposed remedial measures with the national geographic information system interface database relating to arsenic for analysis, production of hazard maps, and dissemination on television show for the planners, engineers, managers, field supervisors and affected people, can reach at the sustainable solution for mitigating arsenic and associated problems successfully in Bangladesh.  相似文献   
2.
This study evaluates the synoptic features and environmental conditions of Brahmanbaria tornado event that caused 36 fatalities, 388 injuries and huge damages of properties on 22 March, 2013. Various factors for initiation of that terrific event are investigated through analysis JRA-55 reanalysis (50 km horizontal resolution) data and Multi-functional Transport Satellite images by Japan Meteorological Agency. In addition, radar images, radiosonde data and three hourly synoptic data of Bangladesh Meteorological Department are used to verify the reanalysis data. The genesis of the tornadic storm is identifiable in the most unstable part of the study region. The satellite observations are found to useful to identify the location of convection occurrence region. The half hourly satellite images identify that the convection initiation started at the convergence area and the systems intensify and organize by the continuous moisture supply from the Bay of Bengal. Lower-level convergence coupled with strong wind shear and humidity gradient lift moist air aloft to trigger deep convection and the severe storm occurred. Energy Helicity Index seems a good predictor parameter for this specific case study.  相似文献   
3.
The study aims to reveal Australian households?? perceptions of climate change and their preferences for mitigation action. A web-based survey was conducted in November 2008 in which over 600 households from the state of New South Wales were asked for their willingness to bear extra household expenditure to support the ??Carbon Pollution Reduction Scheme??, an emissions trading scheme proposed by the Australian government. The results of the study can be summarized in four key findings. First, respondents?? willingness to pay for climate change mitigation is significantly influenced by their beliefs of future temperature rise. Support for the policy increased at a decreasing rate as the perceived temperature change rose. Second, perceptions of policy failure have a significant negative impact on respondents?? support for the proposed mitigation measure. The higher the perceived likelihood that the measure would not deliver any outcome, the lower was the likelihood that respondents would support the policy. Third, respondent preferences for the proposed policy are influenced by the possibility of reaching a global agreement on emissions reduction. Sample respondents stated significantly higher values for the policy when the biggest polluting countries implement a similar scheme. Finally, respondents?? willingness to take action against climate change, both at the national and household level, is found to be influenced by their level of mass-media exposure. Particularly, those respondents who watched ??An Inconvenient Truth?? were significantly more likely to act for climate change mitigation than others.  相似文献   
4.
Southern Bangladesh’s irrigation and drinking water is threatened by saline intrusion. This study aimed to establish an irrigation water quality index (IWQI) using a geostatistical model and multivariate indices in Gopalganj district, south-central Bangladesh. Groundwater samples were taken randomly (different depths) in two seasons (wet-monsoon and dry-monsoon). Hydrochemical analysis revealed groundwater in this area was neutral to slightly alkaline and dominating cations were Na+, Mg2+, and Ca2+ along with major anions Cl? and HCO3 ?. Principal component analysis and Gibbs plot helped explain possible geochemical processes in the aquifer. The irrigation water evaluation indices showed: electrical conductivity (EC) >750 µS/cm, moderate to extreme saline; sodium adsorption ratio (SAR), excellent to doubtful; total hardness (TH), moderate to very hard; residual sodium bicarbonate, safe to marginal; Kelly’s ratio >1; soluble sodium percentage (SSP), fair to poor; magnesium adsorption ratio, harmful for soil; and IWQI, moderate to suitable. In addition, the best fitted semivariogram for IWQI, EC, SAR, SSP, and TH confirmed that most parameters had strong spatial dependence and others had moderate to weak spatial dependence. This variation might be due to the different origin/sources of major contributing ions along with the influence of variable river flow and small anthropogenic contributions. Furthermore, the spatial distribution maps for IWQI, EC, SSP, and TH during both seasons confirmed the influence of salinity from the sea; low-flow in the major river system was the driving factor of overall groundwater quality in the study area. These findings may contribute to management of irrigation and/or drinking water in regions with similar groundwater problems.  相似文献   
5.
To investigate the seasonal heterogeneity of the periphytic ciliate communities, a 1-year baseline survey was conducted in the Karnaphuli River estuary, northern Bay of Bengal, Bangladesh. A total of 54 ciliate species were recorded, including seven common and 14 dominant species. Maximum species number was in autumn whereas maximum abundance was in winter; the minimum for both occurred in summer. Multivariate analyses, i.e., canonical analysis of principal coordinates (CAP) and principal co-ordinates analysis (PCoA), revealed a clear seasonal heterogeneity of community structure and environmental variables. Multivariate correlation analysis (RELATE) demonstrated that the community structure of the periphytic ciliate communities was significantly correlated with environmental variables, and best matching analysis (BIOENV) indicated that heterogeneity of community patterns was mainly driven by water temperature, pH, dissolved oxygen, total dissolved solids and nutrients. Species richness and diversity peaked in autumn whereas species evenness peaked in summer. These results suggest that environmental conditions shape periphytic ciliate community structure, which is a potentially useful bio-indicator of estuarine water quality.  相似文献   
6.
To identify the causes of salinization and arsenic contamination of surface water on an embanked island (i.e., polder) in the tidal delta plain of SW Bangladesh we collected and analyzed water samples in the dry (May) and wet (October) seasons in 2012–2013. Samples were collected from rice paddies (wet season), saltwater ponds used for brine shrimp aquaculture (dry season), freshwater ponds and tidal channels (both wet and dry season), and rainwater collectors. Continuous measurements of salinity from March 2012 to February 2013 show that tidal channel water increases from ~0.15 ppt in the wet season up to ~20 ppt in the dry season. On the polder, surface water exceeds the World Health Organization drinking water guideline of 10 μg As/L in 78% of shrimp ponds and 27% of rice paddies, raising concerns that produced shrimp and rice could have unsafe levels of As. Drinking water sources also often have unsafe As levels, with 83% of tubewell and 43% of freshwater pond samples having >10 μg As/L. Water compositions and field observations are consistent with shrimp pond water being sourced from tidal channels during the dry season, rather than the locally saline groundwater from tubewells. Irrigation water for rice paddies is also obtained from the tidal channels, but during the wet season when surface waters are fresh. Salts become concentrated in irrigation water through evaporation, with average salinity increasing from 0.43 ppt in the tidal channel source to 0.91 ppt in the rice paddies. Our observations suggest that the practice of seasonally alternating rice and shrimp farming in a field has a negligible effect on rice paddy water salinity. Also, shrimp ponds do not significantly affect the salinity of adjacent surface water bodies or subjacent groundwater because impermeable shallow surface deposits of silt and clay mostly isolate surface water bodies from each other and from the shallow groundwater aquifer. Bivariate plots of conservative element concentrations show that all surface water types lie on mixing lines between dry season tidal channel water and rainwater, i.e., all are related by varying degrees of salinization. High As concentrations in dry season tidal channel water and shrimp ponds likely result from groundwater exfiltration and upstream irrigation in the dry season. Arsenic is transferred from tidal channels to rice paddies through irrigation. Including groundwater samples from the same area (Ayers et al. in Geochem Trans 17:1–22, 2016), principal components analysis and correlation analysis reveal that salinization explains most variation in surface water compositions, whereas progressive reduction of buried surface water by dissolved organic carbon is responsible for the nonconservative behavior of S, Fe, and As and changes in Eh and alkalinity of groundwater.  相似文献   
7.

Background

High salinity and arsenic (As) concentrations in groundwater are widespread problems in the tidal deltaplain of southwest Bangladesh. To identify the sources of dissolved salts and As, groundwater samples from the regional shallow Holocene aquifer were collected from tubewells during the dry (May) and wet (October) seasons in 2012–2013. Thirteen drill cores were logged and 27 radiocarbon ages measured on wood fragments to characterize subsurface stratigraphy.

Results

Drill cuttings, exposures in pits and regional studies reveal a >5 m thick surface mud cap overlying a ~30 m thick upper unit of interbedded mud and fine sand layers, and a coarser lower unit up to 60 m thick dominated by clean sands, all with significant horizontal variation in bed continuity and thickness. This thick lower unit accreted at rates of ~2 cm/year through the early Holocene, with local subsidence or compaction rates of 1–3 mm/year. Most tubewells are screened at depths of 15–52 m in sediments deposited 8000–9000 YBP. Compositions of groundwater samples from tubewells show high spatial variability, suggesting limited mixing and low and spatially variable recharge rates and flow velocities. Groundwaters are Na–Cl type and predominantly sulfate-reducing, with specific conductivity (SpC) from 3 to 29 mS/cm, high dissolved organic carbon (DOC) 11–57 mg/L and As 2–258 ug/L, and low sulfur (S) 2–33 mg/L.

Conclusions

Groundwater compositions can be explained by burial of tidal channel water and subsequent reaction with dissolved organic matter, resulting in anoxia, hydrous ferric oxide (HFO) reduction, As mobilization, and sulfate (SO4) reduction and removal in the shallow aquifer. Introduction of labile organic carbon in the wet season as rice paddy fertilizer may also cause HFO reduction and As mobilization. Variable modern recharge occurred in areas where the clay cap pinches out or is breached by tidal channels, which would explain previously measured 14C groundwater ages being less than depositional ages. Of samples collected from the shallow aquifer, Bangladesh Government guidelines are exceeded in 46 % for As and 100 % for salinity.
  相似文献   
8.
Public scepticism surrounding climate change is an obstacle for implementing climate change mitigation measures in many countries. However, very little is known about: (1) the nature and sources of climate change scepticism; and (2) its influence on preferences for climate change mitigation policies. In this paper, we investigate these two issues using evidence and analysis from an Australian public survey and choice experiment. The study has three key findings. First, the intensity of scepticism varies depending on its type; we observed little scepticism over the cause, trend and impact of climate change and widespread scepticism over the effectiveness of mitigation measures and global co-operation. Second, cause and mitigation scepticism play significant roles in determining public support for climate change abatement. Respondents who believed in human-induced climate change were significantly more supportive of mitigation. Likewise, respondents who believed that mitigation would be successful in slowing down climate change were significantly more likely to be supportive. Third, the general public tend to give the benefit of the doubt to supporting mitigation. Those who expressed higher uncertainty about climate outcomes were more supportive of mitigation than others with similar expectations but lower uncertainty.  相似文献   
9.
The cyclone frequency distribution over the Bay of Bengal during 1990–2009 was distinctly bimodal, with a primary post-monsoon peak and a secondary pre-monsoon peak, despite the very high convective available potential energy (CAPE) during the pre-monsoon. The location of the monsoon trough over the bay is a primary factor in tropical cyclogenesis. Because the trough was in the northernmost bay during the pre-monsoon season, cyclogenesis was inactive in the southern bay, where a strong southwesterly wind shear was found. In this season, moreover, a hot, dry air mass extending vertically from 950 to 600 hPa was advected from northwestern India toward the bay. Moist, warm southwesterly winds penetrating below the deep, dry air mass caused a prominent dryline to form aloft on the northwestern side of the bay. The synoptic-scale hot, dry air forcing to the bay suppressed the active convection necessary for cyclogenesis. The strength of the stable environmental layer, represented by convective inhibition (CIN), was extremely large, and acted as a cap over the northern and northwestern bay. Conversely, during the post-monsoon, there were no horizontal temperature or moisture gradients, and CAPE and CIN were fairly modest. The entire bay was covered by a very deep, moist layer from the surface to 700 hPa transported from the east. The monsoon trough position and the environmental CIN in combination can explain the lower frequency of cyclogenesis during the pre-monsoon compared with the post-monsoon season.  相似文献   
10.
Abstract

Environmental flows have scarcely been considered in river water management in Bangladesh. This study attempts to assess the environmental flow requirements in the Halda River, Bangladesh. Thus, the objectives are to estimate the Halda River flow with different return periods/probabilities, which was done using the log-Pearson Type III distribution (LPIII), and to mitigate the environmental problems in the Halda River using the building block method. The LPIII distribution was used to estimate the expected extreme and satisfactory flows for fish habitat at Panchpukuria station and the expected extreme water levels at Panchpukuria, Narayanhat, Telpari and Enayethat stations. It was found that floods are likely to occur at least once in 2.1, 1.02, 1.75 and 1.25 years at Panchpukuria, Narayanhat, Telpari and Enayethat stations, respectively. The results of flow and water quality analyses suggest that environmental flow requirements cannot be achieved in this river throughout the year. The environmental flow requirements and conservation of fish resources can be achieved by implementing the suggestions provided in conjunction with a comprehensive awareness programme, investigations and trade-off analyses being among the suggestions.

Editor Z.W. Kundzewicz; Associate editor B. Sivakumar

Citation Akter, A. and Ali, Md. H., 2012. Environmental flow requirements assessment in the Halda River, Bangladesh. Hydrological Sciences Journal, 57 (2), 326–343.  相似文献   
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