Determinar cuál es la rentabilidad de la implementación del uso de techos verdes con geomembrana importada de Estados Unidos en el distrito de San

An in-situ anodes experiment was installed within the Hamble estuary, anodes were placed on nine metal piles to monitor corrosion rates of anodes within different regions of the estuary, over a yearly period.

4.8.1ANODE LOCATIONS

The piles were chosen to give an even spread of anodes in the river (Figure 4.6, Table 4.13). The piles chosen all contained metal fittings, so anodes had a good bond to the cathode (Bird et al., 1996). They were generally on the end of rows of boats to avoid the anode wires getting tangled in boat mooring gear, anchor chains or propellers. The anodes were placed on Crown Estate pile moorings controlled by the Hamble Harbour Board. The piles stretched from Hamble-Le-Rice up to Bursledon Bridge.

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Table 4.13: In-situ anode experiment pile numbers and location in river

Pile Location in river Type of pile

A3 Between Hamble Le-Rice, Hamble Point Marina metal

D9 Hamble-le-Rice village metal

HP20 Between Port Hamble and Mercury marina metal

G49 Upstream of Hamble marina and before Mercury bend metal

I42 Downstream mercury marina, before Mercury bend metal

TG On Mercury bend Tide gauge-metal

L25 Situated between Mercury marina and Swanwick marina metal

V8 On Bursledon bend, before the Jolly Sailor Pub metal

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4.8.2EXPERIMENT PREPARATION AND INSTALMENT

The anodes were weighed to two decimal places before the experiment and again after the experiment to determine the dissolution rates at each site in the river. The anodes were analysed on the XRF to determine their metal content (section 4.11).

Once the anodes were weighed and analysed on the XRF, anodes of similar weights were grouped in threes. The anodes were placed on the piles at different depths, to separate one another and to maximise the time anodes were in the water during the tidal cycle. Different colour cable ties (blue, green and red) were placed on each of three anodes so they could be told apart at the end of the experiment, allowing them to be weighed and analysed on the XRF. A rubber mooring doughnut was placed over the cables of the three anodes to act as a spacer and keep the anodes away from the piles as much as possible. The anodes were then connected to the piles via wire clips and wrapping the cables around the blocks welded to the side of the piles. Large cable ties were then placed at high and low water to keep the wire tight to the piles. This prevented them moving out with the tides and getting tangled in mooring gear. The boat owners moored next the piles were informed of the experiment by the Hamble Harbour Board.

The anodes were installed in February 2016 and kept in place for a year period until

February 2017, salinity profiling (section 4.8.3) and cleaning of the anodes occurred during this period.

4.8.3SALINITY PROFILING, MAINTENANCE OF ANODES AND REMOVAL Salinity profiling was carried out to determine the salinity variations in the estuary and used along with Environment Agency data to determine salinity regimes. This was carried out at each pile with anodes present at high and low tide on spring and neap tides in July and October 2016 (Table 4.14).

The anodes were gently cleaned during salinity profiling, with a toothbrush to remove algae, mud, zinc hydroxide Zn(OH)2 and calcium build up on the anodes, but not to abrade

the surface of the zinc anode. This occurred as the anodes were not moving through the water, like they do on a vessel. The anodes were also checked on other visits to the river to make sure they were not caught in moorings chains, etc.

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Table 4.14:Salinity profiling sampling dates, tidal state, times and heights Sampling date Tide type Tide times and (heights)

4th _{July 2016 Spring tide Warsash}

High 11.43 (4.5m) 14.02 (4.5m) Low 17.18 (1m) Bursledon High 11.53 (4.6m) 14.09 (4.5m) Low 17.26 (0.9m) 15th _{July 2016 Neap tide Warsash}

High 8.24 (3.8m) 10.26 (3.7m) Low 14.55 (2m) Bursledon High 8.29 (3.8m) 10.34 (3.7m) Low 13.57 (2.1m) 12th _{October 2016 Neap tide Warsash}

High 9.40 (4.2m) Low 14.22 (2m) Bursledon High 8.29 (3.8m) 10.34 (3.7m) Low 13.57 (2.1m) 21st _{October 2016 Spring Tide Warsash}

Low 8.43 (1.3m) High 15.57 (4.5m) 17.43 (4.5m) Bursledon Low 8.51 (1.3m) High 16.00 (4.5m) 17.44 (4.5m)

Anodes were removed from the estuary in February 2017 after one year of exposure to water in the estuary. Once back in the laboratory the three anodes were separated from one another, weeds and algae removed from anodes and wire rope. They were then left to dry for a couple of days and then weighed and analysed using the XRF like before deployment in the estuary.

An anode release rate was calculated for the Hamble estuary from this experiment using the method used from the survey (section 4.8.1). This was done by using the weight of each anode new and the weight lost over the year of deployment. The release rate was again calculated in kg/yr and converted to kg/yr/vessel based on a three anode average.

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