[Irreversible sorption of phthalate acid esters to river sediments].

Irreversible sorption behavior of two phthalate acid esters (PAEs), Dimethyl phthalate (DMP) and Di-(2-ethyl-hexyl) phthalate (DEHP), on four natural sediment samples from the Yangtze River and the Yellow River has been studied by equilibrium sorption and multiple cycles of adsorption/desorption experiments. The equilibrium sorption experiment results showed that the organic carbon-normalized partition coefficients (lgKoc) of DMP and DEHP were higher than those reported in references. This means that the sorption of DMP and DEHP on natural sediments include other sorption mechanisms besides the linear partition on organic carbon. The multiple cycles of adsorption/desorption experiment results showed that the sorption of PAEs included linear reversible sorption and irreversible sorption. For the four sediment samples, the maximum of irreversible sorption capacities were 125.19-337.37 microg/g and 515.89-591.41 microg/g for DMP and DEHP, respectively, which were positive correlated to the surface areas, cation exchange capacity and black carbon content of the sediments. The OC-normalized partition constants for the reversible compartment (lgk(oc)(rev)) were 3.69-4.98 L/kg for DMP; they were higher than those (lgKoc) reported in references, suggesting other reversible sorption mechanisms exist besides the linear partition on organic carbon. The lgk(oc)(rev) were 4.12-5.31 L/kg for DEHP; they were close to those (lgKoc) reported in references, suggesting the linear partition on organic carbon is the main reversible sorption mechanism. Although the physiochemical properties of DMP and DEHP are different, the OC-normalized partition constant for the irreversible compartment on the four sediments is essentially constant with lgk(oc)(rev) = (6.46 +/- 0.38) L/kg. As irreversible sorption exists for PAEs, the maximum of irreversible sorption capacity should be considered when studying the sediment quality criteria.

[Distribution characteristics of phthalic acid esters in the Wuhan section of the Yangtze River].

Samples of water and sediment were collected at 30 sites in Wuhan section of the Yangtze River in high and low water period. Phthalic acid esters (PAEs) concentrations in each sample were determined by Gas Chromatography. The results were shown as follows: (1) PAEs concentrations in water phase of lakes and tributaries ranged from 0.114-1.259 microg/L in high water period and 0.25-132.12 microg/L in low water period, while slight increasing trends could be discovered in the main stream (0.034-0.456 microg/L and 35.73-91.22 microg/L in high and low water period, respectively). (2) PAEs concentrations in sediment phase of tributaries and lakes in low water period were from 6.3 to 478.9 microg/g. Di-n-butyl phthalate (DBP) and di-(2-ethylhexyl) phthalate (DEHP) both had strong trends from water to sediment phase, and the PAEs concentration ranges of the sediment phase in the main stream were 151.7-450.0 microg/g in high water period and 76.3-275.9 microg/g in low water period; DBP could transfer from sediment to water in high water period, while DEHP still had a potential for adsorption in low water period. (3) Among five studied PAEs compounds, DBP and DEHP were the main pollutants. According to the Surface Water Quality Criteria of China (GB 3838-2002), the limit values of DBP and DEHP for drinking water sources were 0.001 and 0.004 mg/L. All water samples in high water period were up to standard while the standard-exceeding sections accounted for 82.4% in low water period. (4) The PAEs pollution of the Wuhan section was similar to the Velino lake in Italy or the middle and lower stream of the Yellow River in China. However, PAEs concentrations in water phase of the Wuhan section in high water period were lower than most water bodies at home and abroad.

[Adsorption and partition of PAHS on particles of the Yellow River].

Experiments were carried out to study the sorption of PAHs Benzo(a)pyrene, chrysene and Benzo(g, h, i)perylene on particles of the Yellow River. The contributions of adsorption and partition to the sorption of PAHs were investigated. Several significant results were obtained from the study: (1) The total sorption capacity increases with the particle content while the sorption capacity of unit weight particle decreases; the isotherms of Benzo(a)pyrene depend on the particle content. (2) Isotherms of Benzo(a) pyrene can be fitted with the Dual Adsorption-Partition model under different particle content; the measured value of the adsorption and partition are in accord with the theoretical value of the Dual Adsorption-Partition model. (3) The adsorption is predominant in the sorption of Benzo(a)pyrene. When the particle contents are 3, 8 and 15 g/L and the liquid equilibrium concentrations are 2.84, 2.35 and 3.4 microg/L, respectively, the contributions of adsorption are 67.8%, 65.6% and 62.69%, respectively. In addition, the contributions of adsorption have a decreasing trend with the increase of the particle content. (4) The sorption capacity of Benzo (a) pyrene being alone are bigger than that with other PAHs chrysene and Benzo(g, h, i)perylene coexisting in the water system, this also proves that the adsorption is predominant in the sorption of PAHs.