Evaluating arsenic contamination in northwestern Bangladesh: A GIS-Based assessment of groundwater vulnerability and human health impacts

One of the biggest environmental worries in the world today is the risk of arsenic (As) contamination in groundwater. The Atomic Absorption Spectrometer (AAS) was used in this work to assess the As content in groundwater samples from 38 shallow (27 m) tubewells in northwest Bangladesh to determine the existing situation, potential source(s), and likely health risk of As and other important water quality parameters. The range of arsenic concentrations (μgL-1) was troublesome and greater than the WHO recommended level for drinking water, ranging from 0.50 to 164 (mean ± SD: 20.22 ± 36.46). In groundwater, the concentrations of Fe, and Mn vary from 0.04 to 52.75 mgL-1 (mean ± SD: 4.23 ± 9.68), and 0.23 to 3.27 mgL-1 (mean ± SD: 1.10 ± 0.67). The obtained groundwater samples have pH values ranging from 5.9 to 7.1, which indicates a somewhat acidic to neutral character. Major cations have an average abundance that is as follows: Ca2+ > Mg2+ > Na+ > K+, while major anions have an average abundance that is as follows: HCO3- > Cl- > SO42- > NO3-; Ca2+ and HCO3- are the main cation and anion, respectively. The groundwater in the Rajarampur village was deemed unfit for drinking or irrigation based on analyses of water quality performed using the entropy water quality index. The Ca-HCO3 type of water, in which Ca2+ and HCO3- are the main positive ions and negative ions, is suggested by the Piper tri-linear diagram. It was discovered that silicate weathering regulates the hydro-geochemical activities in groundwater using a bi-variate examination of several hydro-chemical variables. Four major clusters were observed for the water sample. According to reductive dissolution processes and principal component analysis, the arsenic in groundwater is geogenic in origin. Arsenic is discharged from sediment to groundwater by reductive dissolution of FeOOH and MnOOH, as shown by the modest connection between As, Fe, and Mn. The United Nations Environmental Protection Agency's (USEPA) suggested value for probable cancer risk assessment was 10-6, however the probable cancer risk assessment found a higher value, indicating that the population in the study region was at high risk for cancer. Remedial measures for arsenic mitigation include removing arsenic from groundwater after it is extracted, searching for alternative aquifers, and implementing various water-supply technologies such as dugwells, deep tubewells, pond-sand filters, and rainwater harvesting systems.

Origin, spatial distribution, sediment contamination, ecological and health risk evaluation of trace metals in sediments of ship breaking area of Bangladesh

Eleven trace metals (Cd, Cr, Fe, Mn, Cu, Ni, Co, Zn, As, Pb, and Ag) in sediments of Bangladesh's ship breaking area were measured by an atomic absorption spectrometer to determine origin, contamination extent, spatial distributions, and associated ecological and human health hazards. This study found considerable quantities of Pb, Cd, Mn, Zn, and Cu when compared with standards and high levels of Pb, Cd, Zn, Cu, As, and Ag contamination according to pollution evaluation indices. Different indices indicate most of the sampling sites were highly polluted. However, spatial distribution maps indicate that trace metals were predominantly deposited in the northern and southern region. The ecological risk index revealed that Cd has the highest while Pb and As had moderate risk. Based on the health index values, Zn for both adults and children were higher than the safe limit while Mn, Pb, Cr, As, Fe, Cu, Ni, and Co for children were close to the threshold. The mean total carcinogenic risk values of Cr, As, and Ni for children and Ni for adults exceeded the permissible threshold. The cancer risk possibilities were further assessed using Monte Carlo simulation. Most trace metals have anthropogenic origins, which were attributed to ship breaking activities.

Spatial distribution, water quality, human health risk assessment, and origin of heavy metals in groundwater and seawater around the ship-breaking area of Bangladesh

The concentrations of eleven heavy metals (Pb, Cd, Cr, Fe, Mn, Zn, Cu, Ni, Co, As, and Ag) were assessed in both groundwater and seawater collected from the ship-breaking industrial area of Bangladesh using an atomic absorption spectrometer. The investigation aimed to estimate the water quality and pollution level employing several indices, and its associated health risks for the first time in that area. This study found that Cd, Cr, Fe, Pb, Mn, and Ni were higher in both groundwater and seawater compared with WHO standards. Based on the WQI (water quality index) and EWQI (entropy water quality index) classifications, the quality of most of the groundwater is extremely poor or unsuitable for drinking purposes. Furthermore, the HPI (heavy metal pollution index), HEI (heavy metal evaluation index), and CD (degree of contamination) values of most groundwater and all seawater samples exhibit a higher degree of pollution. In addition, the results of NI (Nemerow pollution index) come to an end that both groundwater and seawater in the study area are mostly polluted by Fe, Mn, Pb, Cr, and Cd. Although the HI (hazard quotient index) values of almost all studied heavy metals in both cases of adults and children are within the safe limit, the HI value of Cr for an adult is near the threshold limit and the maximum HI value of Cr for children exceeds this limit. The carcinogenic risk reveals that Cr, Pb, As, and Cd produce detrimental effects on local people through the direct ingestion of groundwater. The pollution source is identified using principal component analysis and a Pearson correlation matrix as being primarily anthropogenic and attributed to intensive ship-breaking activities or other industries in the area.

Mechanism of arsenic enrichment and mobilization in groundwater from southeastern Bangladesh: Water quality and preliminary health risks assessment

To understand the mechanistic pathway of arsenic (As) enrichment and mobilization in groundwater (southeastern Bangladesh) and to evaluate the water quality as well as associated health risks, a suite of systematically collected groundwater samples (depth: 17-61 m) were analyzed. Arsenic concentrations (μg L^-1) in the groundwater samples were ranged from 6 to 581 with a mean value of 199 which is significantly higher than the recommended values. The assessment of water quality using entropy water quality index and irrigation water quality indices revealed that the groundwater in the studied region was not recommended for drinking and irrigation, respectively with few exceptions. Dominant water types in the studied area were Ca-Mg-HCO_3, Na-HCO₃, and Na-Cl types. Various forms of water-rock interactions, leaching of evaporates, and the confined nature of the aquifer mostly control the hydro-chemical parameters. Fe/Mn bound As are likely to be released in the aquifer through the dissolution of carbonate minerals of Fe/Mn while the higher degree of water-rock interaction and probable oxidation of organic materials helped to elevate As concentration. The probable longer residence time of groundwater guided by topographic slope and the neighboring clayey aquitard govern the As mobilization in the aquifer. Probabilistic health risk assessment revealed that groundwaters from the studied area can cause both non-carcinogenic and carcinogenic health risks.

Trace metals pollution in seawater and groundwater in the ship breaking area of Sitakund Upazilla, Chittagong, Bangladesh

This study reveals potential accumulation of trace metals in the sea and groundwater due to ship breaking activities which take place along the Bay of Bengal in Sitakund Upazilla, Chittagong, Bangladesh. When compared with WHO and Bangladesh domestic standards for water quality, it is revealed that seawater was strongly polluted by Fe and Hg, moderately by Mn and Al, and slightly by Pb and Cd. Groundwater was strongly polluted by Fe, Pb and Hg, moderately by Mn and Al, and slightly by As. Trace element concentrations of all seawater samples exceeded the average concentration of elements in the Earth's seawater. The application of Principal Components Analysis identified two sources of pollution-marine and ship breaking. The mechanism of groundwater pollution inferred that if seawater is polluted, nearby groundwater is also polluted with trace metals due to the influence of seawater intrusion.

Comparison of three fluid regimens for preloading in elective caesarean section under spinal anaesthesia

The most common problem associated with subarachnoid block (SAB) for caesarean section remains the rapid onset of profound hypotension. This study was designed to compare the incidence of hypotension after preloading with Ringer's Lactate, Hydroxyethylstarch and combination prior to SAB in caesarean section. Ninety non-labouring ASA grade 1 and 2, aged 20-35 years, weight and height was 45-60kg and 153-165cm respectively divided randomly into three groups. Group-RL received Ringer's Lactate 20ml/kg as preloading fluid. Group-H received Hydroxyethylstarch-6% 8ml/kg and Group-RLH received preloading fluid with combination of Ringer's Lactate 10ml/kg and Hydroxyethylstarch-6% 4ml/kg. Blood pressure (Systolic, Diastolic & Mean arterial pressure) was measured every 5 minute for 20 minute and every 10 minutes thereafter. Hypotension was less in Group-RLH (6.7%) whereas in Group-H and Group-RL hypotension was 20% and 47.7% respectively. Systolic blood pressure decreased significantly in all three groups. But the decreasing was less in Group-RLH than other two groups. Less IV fluid was required in Group-RLH (403ml) and Group-H (577ml) in comparison to Group-RL (1032ml) to prevent and treat peroperative hypotension. No ephedrine was needed in Group-RLH. Variation in Pulse rate was not significant in Group-RLH (p=0.061). But in other two groups it was highly significant (Group RL p≤0.001 and Group H p=0.004). There was no significant difference in neonatal outcome between three groups. Preloading with low volume colloid (4ml/kg) plus crystalloid (10ml/kg) is superior to crystalloid or colloid alone.