One method used to measure water pollution by organic waste is to calculate the biological oxygen demand, BOD. This determines the rate at which oxygen is used by micro-organisms in the water.

To determine the BOD of water, a sample of water is taken from the sea or river and the concentration of oxygen is measured.

The sample is then placed in a tube with an airtight seal and kept at 20*C for five days. The concentration of oxygen is then measured again.

The fall in oxygen concentration is the BOD.

Suggest why the airtight seals are placed on the tubes.

Ms. w, a 21-year-old woman, came into a clinic after suffering a deep laceration on her foot while walking barefoot around her yard. the wound was cleaned, sutured, and bandaged, and she was released to return home after receiving tetanus antitoxoid. within 72 hours, the wound area was red and swollen, the suture line was dark in color, and it was accompanied by severe throbbing pain. ms. w had a high fever, her heart felt like it was racing, and she was finding it hard to concentraten even on simple tasks. she returned to the clinic and was immediately taken to the hospital. following lab tests, a diagnosis of acute necrotizing fasciitis was made. discussion questions 1. explain why ms. w. received a tetanus antitoxoid before leaving the hospital. (see chapters 3 and 4, infection and passive immunity.) 2. explain how acute necrotizing fasciitis developed in this case and the pathophysiology involved. (see acute necrotizing fasciitis.) 3. what is the potential outcome for ms. w if antibiotic drugs do not reduce the infection quickly?