Physico-chemical properties of Dhepa River in Dinajpur District of Bangladesh

Among different water quality parameters dissolved oxygen, transparency, pH, PO4-P and depth varied significantly among the sampling sites. The pH value in the present investigation remained a buffer condition (6.50- 7.90). Dissolved oxygen was ranges from 3.80 to 11.60 mg/l throughout the study periods. PO4-P concentration was observed highest (0.30 mg/l) in sampling site 2. On the basis of physical, chemical aspects sampling site 3 and sampling site 5 (situated in gosaipur and chandandoho) found in better condition in terms of limnological aspects. However, it could be concluded that Dhepa River will play important role in riverine fisheries and for further fisheries management.DOI: http://dx.doi.org/10.3329/jesnr.v6i1.22041 J. Environ. Sci. & Natural Resources, 6(1): 59-67 2013

STEROID FOCUSING BY MICELLE COLLAPSE IN MICELLAR ELECTROKINETIC CHROMATOGRAPHY

Preliminary studies on the separation of neutral steroids through analyte focusing by micelle collapse (AFMC) are presented to investigate its efficiency, sensitivity and limit of detection (LOD). The focusing mechanism of AFMC is based on the transport, release, and accumulation of molecules bound to micelle carriers that are made to collapse into a liquid phase zone. The sample solution of the neutral analytes (S) is prepared using sodium dodecyl sulphate (SDS) at a concentration above the critical micelle concentration (cmc) with higher conductivity than the running buffer. Normal mode–micellar electrokinetic chromatography (NM–MEKC) separation was initially performed on 100 mg/L of six neutral steroids in methanol using 20 mM SDS, 10% (v/v) methanol and sodium borate buffer (pH 9.0) with positive applied voltage of 25 kV and pressure injection of 50 mbar for 1 sec at 25°C. The same buffer condition has been applied to AFMC–MEKC, whereby the mixture of six neutral steroids was dissolved in 2 mM SDS and 250 mM sodium borate buffer which gave a conductivity ratio of 0.49. Results showed a good separation of prednisolone, prednisone, betamethasone, testosterone, 17–α–methyltestosterone, and 4–androstene–3,17–dione at 240 nm with sensitivity enhancement factors of 2.08, 1.17, 0.92, 16.9, 0.8, and 1.21 respectively. AFMC–MEKC allowed several folds improvement in sensitivity compared to NM–MEKC.

Runoff and Sediment from Row-crop, Row-crop with Grass Strips, Pasture, and Forest Watersheds

Comparisons of runoff and sediment loss from row-crop with and without riparian buffers, pasture and grass filter strips are limited. Effects of precipitation, landuse and buffer condition on runoff and sediment loss were examined from 1997 to 1999 in eight watersheds with varying proportions of row-crop, pasture, riparian buffers and grass filter strips. Runoff volume and sediment mass from row-crop watersheds were inversely related to the percentage of forest and pasture cover. Forest (n = 2), pasture (n = 3), row-crop (n = 2) and a row-crop watershed with grass filter strips (RC-GFS) had 3‑yr mean runoff of 939, 1,560, 3,434 and 1,175 m3 ha‑1 yr‑1, respectively. Runoff was greater from all landuses in a year when precipitation was 36% above normal (1998). The largest single runoff event from each watershed accounted for 11 to 25% of its total runoff. Forest, pasture, row-crop and RC-GFS watersheds lost 1,017, 1,241, 3,679 and 2,129 kg ha‑1 yr‑1 of sediment, respectively. In 1998, the RC-GFS watershed lost more sediment than row-crop watersheds and had less runoff and sediment loss in years with normal or below normal precipitation. Row-crop watersheds with 55% pasture reduced runoff and sediment loss by 55 and 66%, respectively, compared to row-crop watersheds. During 90% of the runoff events, more soil was lost from row-crop watersheds than pasture or forest watersheds. Results suggest that 3‑4 m grass filter strips, maintenance of 55% or more pasture/CRP land within row-crop watersheds and intact riparian buffers significantly reduce runoff and sediment losses from row-crop watersheds.