Simulation and parameter determination of the net sorption of phenanthrene by sediment particles.

The distribution of polycyclic aromatic hydrocarbons (PAHs) in the ocean is affected by the sorption-desorption process of sediment particles. This process is determined by the concentration of PAHs in seawater, water temperature, and organic matter content of sediment particles. Quantitative relationships between the net sorption rates (=the difference of sorption and desorption rates) and these factors have not been established yet and used in PAH transport models. In this study, phenanthrene was chosen as the representative of PAHs. Three groups of experimental data were collected to address the dependence of the net sorption processes on the initial concentration, water temperature, and organic carbon content representing organic matter content. One-site and two-compartment mass-transfer models were tested to represent the experimental data using various parameters. The results showed that the two-compartment mass-transfer model performed better than the one-site mass-transfer model. The parameters of the two-compartment mass-transfer model include the sorption rate coefficients kafand kas (L g-1 min-1), and the desorption rate coefficients kdf and kds (min-1). The parameters at different temperatures and organic carbon contents were obtained by numerical simulations. Linear relationships were obtained between the parameters and water temperature, as well as organic carbon content. kaf, kas and kdf decreased linearly, while kds increased linearly with temperature. kaf, kas and kdf increased linearly, while kds decreased linearly with organic carbon content. The r2 values between the simulation results based on the relationships and the experimental results reached 0.96-0.99, which supports the application of the model to simulate sorption-desorption processes at different water temperatures and organic carbon contents in a realistic ocean.

Seasonal variations of nutrient concentrations and their ratios in the central Bohai Sea.

The Bohai Sea is a typical semi-enclosed sea in the northwest Pacific, which is subject to serious eutrophication due to human activities. Similar to hydrographic variables such as water temperature and salinity, the nutrient concentrations and ratios in the Bohai Sea also exhibit seasonal variations. However, the effects of external inputs, biological processes, and benthic processes on these seasonal variations have not been quantified to date. To address this issue, a physical-biological coupled model was developed to capture the seasonal nutrient cycling in the central Bohai Sea. The simulation results revealed apparent seasonal variations in the concentrations of dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP), and dissolved silicate (DSi). The N/P ratio (as the molar ratio of DIN/DIP) also exhibited an apparent seasonal variation, with the maximum and minimum values in surface water occurring in summer (>100) and winter (<30), respectively. The Si/N ratio (as the molar ratio of DSi/DIN) was slightly higher in summer than in other seasons. The budget for three types of nutrient indicated that the biological processes determined the seasonal variations in nutrient concentrations and the N/P ratio. The external inputs of nutrients via river input, atmospheric deposition, and sediment release were probably important in summer when they could alleviate the reduced nutrient concentrations due to biological processes. To maintain a reasonable nitrogen budget, it was necessary to include benthic nitrogen loss, which removed a large amount of inorganic nitrogen in summer and autumn. In addition, the variation of N/P ratio of phytoplankton uptake can reduce the ratio of DIN to DIP in surface water by ~20 in summer as compared to the calculation with a fixed N/P ratio (16:1) in phytoplankton uptake.

[Application of modified adjustable skin stretching and secure wound-closure system in repairing of skin and soft tissue defect].

Objective: To investigate the application of modified adjustable skin stretching and secure wound-closure system in repairing of skin and soft tissue defect. Methods: Between March 2016 and April 2017, 21 cases of skin and soft tissue defects were repaired with the modified adjustable skin stretching and secure wound-closure system (the size of regulating pressure and the times of adjustment were determined according to the color, temperature, capillary response, and swelling degree of the skin edge). There were 11 males and 10 females, with an average age of 49.2 years (range, 21-67 years). Among them, 1 case was the residual wound after amputation of leg; 18 cases were the wounds after traumatic injury operation, including 4 cases in the lower leg, 3 cases in the knee joint, 7 cases in the upper limb, and 4 cases in the foot; and 2 cases were diabetic feet. The skin defect area ranged from 4.0 cm×2.5 cm to 21.0 cm×10.0 cm. Results: Skin defect wounds closed directly in one stage in 4 cases; 12 cases were closed after continuously stretching for 5-14 days (mean, 10 days); 5 cases were reduced to less than one-half area, and the wound healed after the second skin grafting or flap repairing. All the 21 patients were followed up 3-12 months (mean, 5.2 months). The wound was linear healing with small scar, and no invasive margin, poor blood flow, necrosis, and poor sensory function happened. Conclusion: The modified adjustable skin stretching and secure wound-closure system can reduce the skin and soft tissue defects or close the wound directly, and even replace the skin graft and skin flap repairing. It was a good method for the treatment of skin and soft tissue defect.