Pollution is one of the biggest threats to biodiversity and the environment in the world. It can come in a number of forms, ranging from simple fertilizer and agricultural runoff, to plastic and other trash pollution, through to radioactive and other toxic waste. Unfortunately, the worst affected areas are usually waterbodies such as lakes or rivers. Since local communities often rely on these for water, food, and/or recreation, the pollution can then have flow on effects. Here are five of the world’s most polluted lakes:
Lake Karachay (sometimes spelled Karachai or Karachaj), is a small lake in central Russia. It is often referred to as the most polluted site on earth. Containing just one square mile of water, the lake formed a dumping ground for nuclear waste by the Soviet Union for around 12 years between 1934 and 1957. Apparently, high level radioactive waste makes up almost the entire lake-bed to a depth of around 3.4 meters. Some areas surrounding the lake have radiation measurements of around 6 Sv/hour, which is enough to give a lethal dose to a human in as little as 30 minutes[sc:1].
Onondaga lake, located in central New York state, is proof that pollution isn’t strictly limited to poorer or third world countries. Pollution of the lake has been a problem since at least the end of the 19th century, with ice harvesting banned as early as 1901. Swimming was also banned in 1940, followed by a fishing ban in 1970 due to mercury contamination. A number of factors have contributed to the extreme pollution of the lake. Raw sewerage was dumped directly into the lake for years, leading to high nutrient concentrations and algal blooms. Chemical pollution in the form of heavy metals and toxic waste by the Allied Chemical Corporation continued up until 1986. An estimated 165000 pounds of mercury were dumped in the lake during the company’s operations[sc:2].
Lake Tai is located on the Yangtze Delta near Shanghai in China. It is the third-largest freshwater lake in China, and has been plagued by pollution in recent times due to the rapid growth of surrounding regions. While details surrounding the pollution in the lake are sparse, there are thousands of factories on its shores, which quite possibly all discharge industrial waste into its waters. Major algal and cyanobacterial blooms have been experienced in the past. Despite the governments so called efforts to reduce the pollution levels, the problem doesn’t seem to be improving[sc:3].
Serra Pelada Lake
The Serra Pelada Lake is not actually a true lake at all. Rather, it is an abandoned gold mine which has filled with water. Regardless, it is still one of the most polluted water bodies in the world, mainly due to the mercury used in the gold extraction process. It is located in central Brazil, and villagers downstream of the lake reportedly suffer from elevated mercury levels from eating contaminated fish[sc:4].
One of the African Great Lakes, Lake Victoria was named after Queen Victoria when it was first documented in 1858. It is the world’s second largest freshwater lake, and Africa’s largest. It forms the border between three countries: Kenya, Tanzania, and Uganda. This has made pollution prevention difficult, due to the fact that all three countries need to work together in order to effectively reduce pollution. The lake has long been polluted by raw sewerage, fertilizers, and chemicals, as well as being a popular dumping ground for domestic and industrial waste. These pollutants reduce the quality of the water, which is relied on by millions of people living on the shores of the lake[sc:5].