Abstract
A study was conducted at the Department of Agricultural Chemistry, Bangladesh
Agricultural University, Mymensingh to assess irrigation water quality and metal
accumulation in soils and crops irrigated with water samples of four rivers namely Turag,
Balu, Khiru and Bangshi around industrial areas at farmers' field during dry season. Thirty
water samples from each river were collected in consecutive two years to measure pH, EС,
TDS, major ionic constituents (Ca, Mg, K, Na, CO3 & HCO3) and metal ions (Fe, Mn, Cu,
Zn, Pb, Cr, Cd & Ni) in order to categorize their suitability for irrigation usage. pH values
of four river water samples were slightly acidic to alkaline. The river water samples were
under low to medium salinity [C1 (EC<250 μS cm-¹) and C2 (EC=250-750 µS cm-1)] and low
alkalinity (S1, SAR<10) hazards expressing as C1S1 and C2S1 classes. TDS values of river
waters were rated as fresh water (TDS<1,000 mg L-1) in quality. The levels of Mn and Cr
ions in four river water samples under study exceeded the permissible limits of
WHO/FAO standard and considered as chemical contaminants for irrigation usage. The
order of metals magnitude for the selected river waters was: Fe> Mn> Cr> Pb> Zn> Cu>
Ni for the Turag river, Fe> Mn> Pb> Cr> Zn> Cu> Ni for the Balu river, Fe> Pb> Mn> Zn>
Cr> Cu> Ni for the Khiru river and Fe> Mn> Cr> Pb> Cu> Zn>Ni for the Bangshi river.
Again, thirty soil samples from each river water irrigated sites were collected to determine
pH, EC, OC and total metal ions (Ca, Mg, Na, K, Pb, Cr, Cd, Cu, Zn, Fe and Mn) in
successive two years. The relationships between soil characteristics and mobility of metals
were studied. The results showed the strong influence of pH and EC on retention and
mobility of metals. The levels of metal ion in soil irrigated with the contaminated river
water was found in the order of Fe> Mn> Zn> Cu> Cr> Pb> Ni for the Turag; Fe> Mn>
Zn> Cr> Cu> Pb> Ni for the Balu; Fe> Mn> Zn> Cr> Pb> Cu> Ni for the Khiru and Fe>
Mn> Zn> Cr> Pb> Cu> Ni for the Bangshi. Geoaccumulation index (Igeo) values of four
river sites indicated uncontaminated to moderately polluted soil in terms of metals while
pollution load index (PLI) indicated soil environment of those river sites with progressive
deterioration. The calculated enrichment factor (EFC) values of four river water sites
exhibited the enrichment of Cr and Pb in soils. The sequence of soil pollution level of the
studied four river areas were Bangshi>Turag>Balu>Khiru. Multivariate analysis revealed
that the correlation of chemical parameters of water and soil samples was loading by the
contaminated river water irrigation. The bioaccumulation of Pb, Ni and Cr ions in leafy
vegetables viz., water spinach, red amaranth, indian spinach and stem amaranth was
observed in three rivers sites and bioaccumulation of Pb and Cr ions in rice grain and
straw was also found in four river areas for long-term irrigated sites. The cumulative THQ
(CTHQ) value of rice grain ranged from 2.439 to 3.144 for male and from 3.415 to 4.402 for
female while CTHQ values of vegetables were 2.435 to 2.742 for male and from 3.409 to
3.839 for female, respectively revealing the potential health risks. Individual THQ value of
metals in vegetables and rice grain also showed the abundance of Mn, Pb and Cr ions in
vegetables and rice grain. The present study clearly indicated the contamination of water,
soil and plant systems caused by metals under consideration in the irrigated sites of four
rivers toward food safety and health risks to the local population.