BBC_Earth_Singapore_2017

Do all fish and

shellfish contain

mercury?

Mr Trash Wheel

HOW IT WORKS

At the mouth of the Jones Falls River, where it feeds into Baltimore Harbour in the US, sits Mr Trash Wheel. Since 2014,

this semi-autonomous floating rubbish collector has scooped up more than 500 tonnes of detritus, including

9,000,000 cigarette butts, 492,000 coffee cups and 376,000 crisp packets. Mr Trash Wheel cost US$720,000 to build,

and has now been joined by Professor Trash Wheel, a ‘female’ version in a different part of the harbour.

Mercury levels in the oceans have tripled since the

Industrial Revolution, thanks to mining and the burning

of fossil fuels. All sea creatures absorb some of this

heavy metal directly, and once it’s in the body there’s

no way of getting rid of it. The amount of mercury in fish

varies between species. Long-lived predators like tuna

and swordfish tend to contain the most, because they

also absorb mercury from their prey and they’ve had a

long time to accumulate it. The lowest levels are found

in short-lived species lower down the food chain, such

as oysters and shrimp. HS

5.

Most of the rubbish isn’t

thrown in the river

directly – it’s land lit ter,

washed in by the rain.

A heavy storm can fill 12

skips!

1. The river current drives
   trash toward floating
   booms, which funnel
   rubbish to Mr Trash
   Wheel’s mouth. Long
   forks attached to a
   conveyor collect and
   compact the debris.

3.

A second conveyor

belt scoops up the

rubbish, drains away

the water and carries

the rest into a skip on

a separate floating

barge.

2.

The conveyors are

powered by a water

wheel fed by the river

current. When the

flow isn’t fast

enough, solar panels

can take over.

4.

As each skip fills, it’s

towed away and the

rubbish is incinerated

to generate electricity.