The extraction efficiency of a dispersive liquid-liquid microextraction (DLLME) method coupled with gas chromatography-microelectron capture detection (GC-μECD) for the simultaneous determination of 20 organochlorine pesticides (OCPs) in water samples was evaluated. The optimum conditions of DLLME for OCP measurement in water sample were determined with 10 μL of carbon tetrachloride (CCl4) and 1.5 mL of acetone as the extraction and dispersive solvents, respectively, all measurements were conducted under room temperature without the addition of salt. OCPs were extracted with good recoveries (60.35 -107.89%) by the proposed method, except for heptachlor and aldrin due to the specific physico-chemical properties of these chemicals. Quantitative analysis showed that the relative standard deviations (RSDs) were below 9% and rather wider linear ranges (LRs) of 0.1 -50 μg/L were obtained. The limits of detection (LODs) were in the range of 0.21 -11.65 ng/L and no significant matrix effects were observed. Obtained results demonstrated that DLLME coupled with GC-μECD was rapid, convenient and efficient for OCP analysis in water samples.

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As the core of arid Central Asia, Uzbekistan is experiencing prominent water scarcity with increasingly warming climate and accelerated human impact. To determine the hydrochemical characteristics and sources of toxic elements, as well as to assess water quality and health risks in Uzbekistan, 55 surface water samples were collected from the Amu Darya Basin of Uzbekistan (ADBU) and monitored for 20 parameters. A hierarchical cluster analysis showed that river water samples from the middle reach and Amu Darya Delta (ADD) were dominantly HCO3-Ca and SO4-Ca·Mg type, respectively. While the water samples collected near the former shoreline of the ADD and sewage outlets were dominantly Cl-Ca·Mg and Cl-Na types, which were consistent with the distribution of sites with high concentrations of toxic elements, seriously affected by human activities. Furthermore, principal component analysis indicated that the toxic elements of Pb and Cd in surface waters of the ADBU had industrial origins; local agricultural activities were considered to have contributed much of the NO3, Zn, Ni, Hg and Mn through pesticides and fertilizers; and Cu, Cr, As, and Co were controlled by mixed anthropogenic and natural sources. The results of water quality and health risk assessment also suggested that unsuitable drinking waters were displayed near the former shoreline of the ADD region and sewage outlets, and human health risks also occurred these areas.