Field retrieval 1

The first retrieval at Pont Gendarme went well, though there were some unexpected issues with the cage positioning. In attendance for the retrieval training were Adama, Marie, Anna, Sokhna, Cheikh and Makhfousse. Abdoulaye Djiop again joined us and helped significantly during retrieval.

We left for Saint Louis Monday, the 1^st in the afternoon and arrived that evening. We left the hotel at about 7 am (first light) and headed to the field site.

At the first site, the main drainage pumping station, we found the cages exposed to air (about 15 cm above the water line). The water level had been lowered to facilitate fishing, which was ongoing when we arrived (the fishermen declined to allow photos). Exposure to air prevents water sampling and, in fact, allows for air sampling; neither condition is suitable for this project.

The PSD cages as we found them at the first site.

Also, a cage had clearly been tampered with, the shell removed and the retention nuts missing. The shell had been dented, but the PSDs were still intact. We collected this cage for analysis.

The cage that had been tampered with lost it's shell on retrieval.


A rusted spring and accompanying discoloration on the PSD.


The dented shell.

The cages were repositioned lower in the water column.

The retention springs on the cages are not stainless steel and had rusted. These should be replaced with stainless springs.

Staff washed the two PSD in local water and packaged them in a clip-sealed Teflon bag according to the SOP. (Note: this project necessitates a deviation from the OSU SOP. The OSU SOP requires the local water rinse, then subsequent rinses in HCL, 18 Mohm/cm water, acetone, and finally isopropanol. For the UN-GEF project, the PSDs are washed in local water and then sealed in a Teflon bag. The rinses are performed at the laboratory. This modification is a logistical requirement and has been vetted by OSU/ Locustox work from the summer of 2006.) A trip blank accompanied our retrieval and a field blank remained exposed for the entire operation at this site.

At the second site, the main irrigation canal, the cages were again exposed, this time about 20cm above the water line. Staff retrieved, cleaned and stored the PSD without incident and according to the SOP. After retrieval, the cages were repositioned so they rested horizontally in the water column.

The cages as we found them at the second site.

Removing the PSDs for the local water wash (L to R: Anna, Marie, Sokhna).

Cheikh and Mr. Djiop helping to reposition the cages horizontally in the water column.

We discussed the possibility of manufacturing new shell retention nuts with an eye hook on them. This would allow easy horizontal deployment, prevent the nut from inadvertently unscrewing, and may help prevent tampering.

The PSDs at this site had about the same amount of fouling as those at the first site.

The third site is the main irrigation pumping station with the cages deployed in the Goron-Lampsor tributary. The cage and PSDs here were extremely clean; no signs of rusting or fouling. Additionally, the cages remained completely submerged. Staff retrieved, cleaned and stored the PSDs without incident in accordance with the SOP.

We again witnessed local household water collection and fishing in the area.

Retrieval of the cages and water quality data collection at site 3

(L to R: Anna, Adama, Mr. Djiop).

At the fourth site, the main drainage canal, the cages remained well positioned. Again, staff retrieved, cleaned and stored the PSDs without incident in accordance with the SOP.

Cage retrieval at site 4 (L to R: Marie, Sokhna, Mr. Djiop, Anna, Makhfousse).

After the final collection we returned to Dakar and deposited the samples at the laboratory that afternoon.

The staff have become comfortable with handling the PSDs and benchsheets. While I was initially disappointed that the first two sites’ cages were partially exposed, Makhfousse pointed out that the incident helps training. It also underscores the fact that these data should be limited to training purposes only.

The PSD extraction, GC analysis and data evaluation steps remain and we will accomplish as much as we can in the remainder of the week.