M. Safiur Rahman

Study on heavy metals levels and its risk assessment in some edible fishes from Bangshi River, Savar, Dhaka, Bangladesh.

Concentrations of eight heavy metals (Pb, Cd, Ni, Cr, Cu, Zn, Mn, and As) in the muscles of ten species of fish collected from Bangshi River at Savar in Bangladesh were measured in two different seasons. The concentrations of the studied heavy metals, except Pb in Corica soborna, were found to be below the safe limits suggested by various authorities and thus gave no indication of pollution. The present study also showed that, Zn was the most and Cd was the least accumulated metal in the studied fish muscles. ANOVA analysis clearly revealed that there was a significant variation (CI=95%) of the heavy metal concentrations in different fish species in the Bangshi River. Significant positive correlations between the heavy metal concentrations in fish muscles were also observed in both seasons. From the human health point of view, this study showed that there was no possible health risk to consumers due to intake of studied fishes under the current consumption rate.

Bench-scale evaluation of drinking water treatment parameters on iron particles and water quality.

Discoloration of water resulting from suspended iron particles is one of the main customer complaints received by water suppliers. However, understanding of the mechanisms of discoloration as well as role of materials involved in the process is limited. In this study, an array of bench scale experiments were conducted to evaluate the impact of the most common variables (pH, PO4, Cl2 and DOM) on the properties of iron particles and suspensions derived from the oxygenation of Fe(II) ions in NaHCO3 buffered synthetic water systems. The most important factors as well as their rank influencing iron suspension color and turbidity formation were identified for a range of water quality parameters. This was accomplished using a 2(4) full factorial design approach at a 95% confidence level. The statistical analysis revealed that phosphate was found to be the most significant factor to alter color (contribution: 37.9%) and turbidity (contribution: 45.5%) in an iron-water system. A comprehensive study revealed that phosphate and chlorine produced iron suspension with reduced color and turbidity, made ζ-potential more negative, reduced the average particle size, and increased iron suspension stability. In the presence of DOM, color was observed to increase but a reverse trend was observed to decrease the turbidity and to alter particle size distribution. HPSEC results suggest that higher molecular weight fractions of DOM tend to adsorb onto the surfaces of iron particles at early stages, resulting in alteration of the surface charge of iron particles. This in turn limits particles aggregation and makes iron colloids highly stable. In the presence of a phosphate based corrosion inhibitor, this study demonstrated that color and turbidity resulting from suspended iron were lower at a pH value of 6.5 (compared to pH of 8.5). The same trend was observed in presence of DOM. This study also suggested that iron colloid suspension color and turbidity in chlorinated drinking water systems could be lower than non-chlorinated systems.

Assessment of Anthropogenic Influence on Heavy Metals Contamination in the Aquatic Ecosystem Components: Water, Sediment, and Fish

Heavy metals (Pb, Cd, Ni, Cr, Cu, Zn, Mn, and As) concentration was investigated in the industrial effluents, water, sediment, and fish samples collected around the Dhaka Export Processing Zone, Savar, Bangladesh, to evaluate the level of contamination. The metals concentration in the industrial effluents of DEPZ and in the water samples of Dhalaibeel (lowland cum lake) and Bangshi River were significantly higher compared to the guideline values for industrial effluents and for drinking water (WHO and USEPA), respectively. The sedimentary metal concentrations were found to be lower than the respective probable effect concentrations (PECs) following the sediment quality guidelines. Furthermore, in comparison with the fish standards, the studied fish species were not found to be contaminated by heavy metals. Principal component analysis and cluster analysis demonstrated that the wastewater from the numerous industries and the domestic sewages around the DEPZ might have a possible impact on heavy metals contamination in the study area. The Pearson correlation analysis showed significant correlations (p < 0.01 and p < 0.05) between most of the metals in the samples of effluents, water, sediments, and fish muscles. The percentage enrichment factor (EF%) and geo-accumulation index () were followed to evaluate metal contamination in the sediment samples. Dhalaibeel sediment was maximally enriched for Cr (53.55%) and Bangshi River sediment for Zn (54.37%). The geo-accumulation index values for the sediment samples were less than zero, indicating that the sediment samples were free from contamination. This study could be used as a model study to assess the impact of anthropogenic activities on heavy metals contamination in aquatic ecosystems.

Spatial distribution and contamination assessment of six heavy metals in soils and their transfer into mature tobacco plants in Kushtia District, Bangladesh

Although the tobacco production and consumption rate in Bangladesh is very high and a substantial portion of premature deaths is caused by tobacco smoking, the status of heavy metals in tobacco plants has not yet determined. This study, therefore, investigated the concentrations of Cu, Ni, Cd, Pb, Cr, and Zn in tobacco plants and their surrounding agricultural soils in Kushtia District, Bangladesh. The geochemical maps showed a similar spatial distribution pattern of the analyzed metals and identified Shempur, Kharara, Taragunia, and Shantidanga as metal hot spots. Geoanalytical indexes were applied to assess the extent of soil contamination, and the results depicted that the soils of Shempur, Kharara, Taragunia, and Shantidanga were moderately contaminated where Cd contributed the most to contamination degree (Cd) in spite of its relative low content. However, other five areas in Kushtia District were suggested as uncontaminated according to both Cd and pollution load index (PLI). The hazard quotient (HQ) and hazard index (HI) showed no possible indication of human health risks via ingestion of agricultural soils. This study also determined that human activities such as excess application of commercial fertilizers, animal manures, and metal-based pesticides were the sources of Cu, Ni, Cd, and Cr enrichment in soils and that the metals into tobacco plants were transported from the soils. The present study conclusively suggested that regulation of improper use of agrochemicals and continuous monitoring of heavy metals in tobacco plants are needed to reduce the tobacco-related detrimental health problems in Bangladesh.

Bench-scale evaluation of ferrous iron oxidation kinetics in drinking water: Effect of corrosion control and dissolved organic matter

Corrosion control strategies are important for many utilities in maintaining water quality from the water treatment plant to the customers’ tap. In drinking water with low alkalinity, water quality can become significantly degraded in iron-based pipes if water utilities are not diligent in maintaining proper corrosion control. This article reports on experiments conducted in bicarbonate buffered (5 mg-C/L) synthetic water to determine the effects of corrosion control (pH and phosphate) and dissolved organic matter (DOM) on the rate constants of the Fe(II) oxidation process. A factorial design approach elucidated that pH (P = 0.007, contribution: 42.5%) and phosphate (P = 0.025, contribution: 22.7%) were the statistically significant factors in the Fe(II) oxidation process at a 95% confidence level. The comprehensive study revealed a significant dependency relationship between the Fe(II) oxidation rate constants (k) and phosphate-to- Fe(II) mole ratio. At pH 6.5, the optimum mole ratio was found to be 0.3 to reduce the k values. Conversely, the k values were observed to increase for the phosphate-to- Fe(II) mole ratio >1. The factorial design approach revealed that chlorine and DOM for the designated dosages did not cause a statistically significant (α=0.05, P>0.05) change in rate constants. However, an increment of the chlorine to ferrous iron mole ratio by a factor of ∼2.5 resulted in an increase k values by a factor of ∼10. This study conclusively demonstrated that the lowest Fe(II) oxidation rate constant was obtained under low pH conditions (pH ≤ 6.5), with chlorine doses less than 2.2 mg/L and with a phosphate-to-Fe(II) mole ratio≈0.3 in the iron water systems.

Assessing irrigation water quality in Faridpur district of Bangladesh using several indices and statistical approaches

Several water quality indices, i.e., salinity hazard (SH), sodium percentage (Na%), sodium adsorption ratio (SAR), permeability index (PI), magnesium hazard (MH), Kelly’s ratio (KR) and irrigation water quality (IWQ) indices are applied to assess the irrigation water quality using 60 groundwater samples collected from the study sites. This study reveals that groundwater samples are mainly Ca-Mg-HCO3 types. The IWQ of groundwater with various classifications are also followed to assess the water suitability for irrigation purposes. Based on IWQ index, it is observed that 68.33% of the water samples (41 locations) belong to high suitability water type, whereas 30% (18 locations) samples exhibit low suitability type for irrigation purposes in the study area. Results of the classification (EC, SH, Na%, SAR, PI, MH, and KR) indicate that groundwater in the study areas are mainly fit for irrigation uses. Besides the above findings, Na+ and Cl− concentrations reveal the positively skewed and are regarded to be extreme. Furthermore, results shows that groundwater mineralization process and rock-water interaction are mainly controlled with bivariate plots of major ions in the study areas. Subsequently, these results are validated using multiple regression models and correlation analysis. The spatial distribution of irrigation indices is carried out by geostatistical modeling. The results of semivariagram model show that most of the irrigation indices have weakly spatial dependence, suggesting agricultural and residential influences. However, it has been expected that this paper helps to give insights for a better management of the groundwater resources for the agricultural purposes in the study area.

Influence of Coadditives on Physical and Mechanical Properties of Jute Fabrics Improved by UV-Cured Coating with Urethane Acrylate

Twelve different formulations were developed with aliphatic backbone-based urethane acrylate oligomer (Ebecry-264) in combination with a number of monomers like N-vinyl pyrrolidone (NVP), tripropylene glycol diacrylate (TPGDA), plasticizer, diallyl phthalate (DP), and antibubling agent methyl ethyl ketone (MEK), along with a photoinitiator Irgacure 184. Some additives and coadditives, such as calcium carbonate, urea, copper, and acrylamide, were incorporated into these formulations to study their effects on the physical and mechanical properties of pendulum hardness, gel content, and tensile strength and elongation at break of the films produced under UV radiation with these formulated solutions. These formulations were applied on jute fabrics (Hessian cloth) and cured under UV radiation. The improvement of various physicomechanical properties, such as tensile strength, elongation at break, and water resistivity of the treated jute fabrics was determined. The best formulation was evaluated.

Evaluation of Water Quality for Sustainable Agriculture in Bangladesh

Sustainable groundwater quality has become a major concern for the agro-based country like Bangladesh. Integrated approaches of various irrigation water quality indices and geostatistical modeling were applied to evaluate the suitability and for spatial mapping of groundwater quality of Faridpur District in central Bangladesh. The irrigation water quality index (IWQI) revealed that majority of the samples were suitable for irrigation. Similar outcomes were recorded from other indices including Na%, sodium adsorption ratio (SAR), residual sodium bicarbonate (RSBC), total hardness (TH), Kelley’s ratio (KR), and magnesium adsorption ratio (MAR). Classifications based on Wilcox diagram and permeability index (PI) plot indicated a similar conclusion wherein almost all the samples were safe for agricultural uses without posing considerable effect on the soil fertility and overall crop yield. Principal component analysis (PCA) grouped the major cations and anions into three principal components including dissolution of calcite minerals, leaching of silicate sediments, and ion exchange process. Spatial mapping of IWQI identified that groundwater in the northern side of Faridpur region were more suitable for irrigational uses relative to central and southern side, possibly due to gradients of domestic discharges and agricultural activates from north to south side. These findings would provide useful information to water distributors, managers, and decision makers for taking adaptive measures in irrigation water quality management systems.