Based on a typical residential area, this paper studies the characteristics of pollutant concentration changes in two rainfall runoffs and the first flush effect of rainfall. In rainfall runoff, the concentrations of seven pollutants (CODMn, TN, DTN, NH3-N, TP, DTP, and PO43−) increased during the initial rainfall period and decreased in the later period. Rainfall causes the erosion of pollutants on the underlying surface so that water pollution begins when rainfall runoff occurs, and the pollution level drops over time. The seven pollutants all experience this first flush effect, of which, rainfall has the strongest scouring effect on NH3-N produced by domestic sewage. The significant excess of pollutants in rainfall runoff should be considered by management departments. In addition, the existence of the first flush effect makes it possible in theory to partially intercept rainfall runoff to control water pollution, thereby reducing the cost of pollution control.
The transdermal delivery of 2 fluorescent probes with similar molecular weight but different lipophilicity, into and through the skin from 2 commercially available transdermal bases, pluronic lecithin organogel, and Lipoderm® has been evaluated. First, in vitro penetration of fluorescein sodium and fluorescein (free acid) through porcine skin was evaluated. Retention and depth distribution profiles in skin were obtained by tape stripping and then followed by optical sectioning using multiphoton microscopy. The results showed that Lipoderm® led to an enhanced penetration of the hydrophilic compound, fluorescein sodium. For the lipophilic compound fluorescein (free acid), Lipoderm® performed similar to pluronic lecithin organogel base, where minimal drug was detected in either receptor phase. The skin retention and depth distribution results also showed that the hydrophilic fluorescein sodium had high skin retention with Lipoderm®, whereas fluorescein (free acid) had very low penetration and retention with increasing skin depth. Moreover, optical sectioning by multiphoton microscopy revealed an uneven distribution of probes across the skin in the x-y plane for both transdermal bases. This work showed that a hydrophilic compound has significantly increased skin penetration and retention when formulated with Lipoderm®, and the skin retention of the probe was the main determinant of its skin flux. 相似文献