A study of groundwater irrigation water quality in south-central Bangladesh: a geo-statistical model approach using GIS and multivariate statistics

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 Gopalgan 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^+, Mg^(2+), and Ca^(2+) along with major anions Cl-and HCO^(3-). Principa component analysis and Gibbs plot helped explain possible geochemical processes in the aquifer. The irrigation wate evaluation indices showed: electrical conductivity(EC)[750 l S/cm, moderate to extreme saline; sodium adsorption ratio(SAR), excellent to doubtful; total hard ness(TH), moderate to very hard; residual sodium bicar bonate, safe to marginal; Kelly's ratio [1; soluble sodiumpercentage(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.

Measurement of DNA damage by terminal deoxynucleotidyl transferase reaction

An improved terminal deoxynucleotidyl transferase- mediated dUTP-biotin nick end labeling method for the quantification of DNA damage in tissues and cultured cells was developed. Many reports have revealed that histochemistry of DNA damage can be visualized using immunohistochemistry for the terminal deoxynucleotidyl transferase reaction in tissue sections. However, few reports have described quantification of DNA damage in tissues or cells. In this study, to estimate the degree of DNA damage, the confirmed method for histochemistry using biotinylated dUTP and deoxynucleotidyl transferase was applied to label the cleaved DNA ends caused by DNA damage in tissues or cells. After end-labeling, avidin-conjugated peroxidase was reacted. A significant correlation was observed between numbers of cleaved DNA ends and peroxidase activity after the reaction. The obtained signals for presented method showed higher than those for ordinary method, and correlate with degree of DNA damage caused by serum deprivation and chemical dose. In addition, DNA damage caused by apoptosis in cells treated with 6-hydroxydopamine or Cu and in the tissues of rats administered a diet containing no Zn could be evaluated quantitatively using the present method.