Laboratory study highlights the key influences of stormwater sediment thickness and bioturbation by tubificid worms on dynamics of nutrients and pollutants in stormwater retention systems.

In urban area, the accumulation of polluted stormwater sediments (SWS) in retention ponds may be a source of dissolved pollutants and nutrients for the aquatic ecosystems. Our objective was to quantify the influence of the thickness of SWS layer and the occurrence of tubificid worms on organic matter processing (O(2) uptake and fluxes of NH(4)(+), NO(3)(-), PO(4)(3-), and dissolved organic carbon between sediment and water), releases of 17 PAHs and 4 heavy metals, and microbial characteristics. Results showed that oxidation of SWS organic matter (O(2) and NO(3)(-) uptakes) and releases of nutrients were significantly increased by the quantity of accumulated SWS and the worm bioturbation. Releases of acenaphtene and naphthalene from sediments were significantly increased by the thickness of the SWS layer. In contrast, tubificid worms did not promote the mobilization of pollutants. In conclusion, biological activities and stormwater sediment characteristics need to be assessed to quantify the fate of pollutants and nutrients in stormwater retention ponds.

[The parathyroid risk in thyroid surgery. Argument against the early postoperative prescription of vitamin D. Experience with 729 thyroidectomies in 1988]. / Le risque parathyroïdien en chirurgie thyroïdienne. Plaidoyer contre la prescription post-opératoire précoce de vitamine D. Expérience de 729 thyroïdectomies en 1988.

729 consecutive patients underwent thyroidectomy in 1988 in the same institution, including 477 (68%) bilateral resections and 242 (33%) total thyroidectomies. An effort was made to see and save all 4 parathyroids and their blood supply. Early post-operative hypoparathyroidism was defined at day 5, by serum calcium less than 8 mg/dl. and serum phosphate less than 4 mg/dl or by serum calcium only if greater than 7.5 mg/dl. Patients afflicted with early hypoparathyroidism were given calcium tablets without any vit D for 1 year at most. Follow-up, checking serum Ca, P and i PIH was done on a 3 months basis during 1 year. Permanent hypoparathyroidism was defined by persistence of the above-mentioned criteria after 1 year, and eventually vit D was started. 27 patients (5.6% our of 477 bilateral thyroid resections) experienced early post-op hypoparathyroidism. Inciting factors were previous thyroid surgery (4), radioiodine treatment (2), modified neck dissection (2), sternal split with mediastinal node clearance (1), visualization of 1 parathyroid gland only (3 redo cases) and autotransplantation of more than 1 parathyroid (1 case). 1 patient was lost for follow-up. 25 others recovered a normal parathyroid function. 1 is permanently hypoparathyroid (1 redo case with other risk factors). Painstaking parathyroid dissection allows a 0% rate of permanent hypoparathyroidism after primary surgery, if vit D is not given in the early post-operative period. We suggest that avoidance of early vit D prescription in cases of early post-operative hypoparathyroidism, leading to mild sustained hypocalcemia, stimulates the spared parathyroid glands (including a possible 5th) and therefore allows full recovery of the parathyroid function.