Determination of OCPs and PCBs in environmental water samples by GC-DLLME optimized by Response Surface Methodology

A new sample preparation procedure to determine seven organochlorine pesticides and seven polychlorinated biphenyls in environmental water samples by using a combination of ultrasonic-assisted solvent extraction and dispersive liquid-liquid micro-extraction was established, and the extracted analytes were analyzed by gas chromatography coupled with electron capture detector. Some parameters influencing the extraction efficiency were studied and optimized utilizing response surface methodology. Under the optimum extraction conditions, the method showed wide linear ranges with r2 > 0.9989 and low limits of detection and quantification between 0.16 ~ 2.17 μg/L and 0.53 ~ 7.16 μg/L, respectively. Enrichment factors (EF) were high and ranged from 63 to 116. Relative standard deviations (RSDs) for the extraction of 25 μg/L of each selected OCPs and PCBs were less than 10.2 %. The proposed method was successfully used for targets contaminations determination in different water samples. α-HCH, β-HCH and p,p’-DDE were found in lake water closed to farmland with concentrations of 2.56 μg/L, 4.44 μg/L and 4.74 μg/L, respectively, and other OCPs and PCBs were not found in the corresponding water samples. The relative recoveries of OCPs and PCBs from tap water, river water and lake water at spiking levels of 10 μg/L were in the range of 81.9 ~ 109.7 %, within a relative standard deviation of 1.7 ~ 11.8 %. The results revealed that the proposed method was well suited for the determination of trace amounts of target contaminations in liquid samples

Effects of Environmental Factors on Nutrients Release at Sediment-Water Interface and Assessment of Trophic Status for a Typical Shallow Lake, Northwest China

Surface sediment and water samples were collected from Daihai Lake to study the biogeochemical characteristics of nitrogen and phosphorus, to estimate the loads of these nutrients, and to assess their effects on water quality. The contents and spatial distributions of total phosphorus (TP), total nitrogen (TN), and different nitrogen forms in sediments were analyzed. The results showed that concentrations of TN and TP in surface sediments ranged from 0.27 to 1.78 g/kg and from 558.31 to 891.29 mg/kg, respectively. Ratios of C : N ranged between 8.2 and 12.1, which indicated that nitrogen accumulated came mainly from terrestrial source. Ratios of N : P in all sampling sites were below 10, which indicated that N was the limiting nutrient for algal growth in this lake. Effects of environment factors on the release of nitrogen and phosphorus in lake sediments were also determined; high pH values could encourage the release of nitrogen and phosphorus. Modified Carlson’s trophic state index (TSIM) and comprehensive trophic state index (TSIC) were applied to ascertain the trophic classification of the studied lake, and the values of TSIM and TSIC ranged from 53.72 to 70.61 and from 47.73 to 53.67, respectively, which indicated that the Daihai Lake was in the stage of hypereutropher

Clay-sized Hf-Nd-Sr isotopic composition of Mongolian dust as a fingerprint for regional to hemispherical transport

Hf-Nd-Sr isotopic fingerprinting has been employed as a powerful method for distinguishing dust sources. However, the Hf and Sr isotopic compositions of dust are highly dependent on particle size to accurately identify dust provenance. Here we compare the Hf-Nd-Sr isotopic compositions of clay-sized fractions from dust sources (the Mongolian Plateau) to sinks (Beijing and Greenland). Our results document that clay-sized Hf-Nd-Sr isotopic compositions of Mongolian dust are controlled by two isotopic/geochemical provinces: Southern Mongolian Gobi (SMG) and Northern Mongolian Plateau (NMP). Our data indicate that the SMG is potentially an important dust source to the loess in Beijing and Hulun Buir and could be a contributing source of dust to Greenland, whereas the NMP contributes little dust to the Chinese loess and the Greenland. Furthermore, we demonstrate that the deserts of northwest China are one of the main dust contributors to Beijing and Greenland, but not to Hulun Buir.</p