Water Pollution

Any physical, biological, or chemical change in water quality that adverselyaffects living organisms or makes water unsuitable for desired uses.

The most serious water pollutants in terms of human health worldwide

The main source of these pathogens is

The WHO estimates that ______________ of all sickness and disease in less-developed countries can be attributed to waterborne infectious agents and inadequate sanitation

The amount of oxygen dissolved in water is a good indicator of water quality and of the kinds of life it will support.

Water with an oxygen content of ________ will support game and other desirable forms of aquatic life.

Water with less than _____ oxygen will support mainly worms, bacteria, fungi, and other detritus feeders and decomposers.

Oxygen is removed from water by ____________ and chemical processes that consume oxygen

is the amount of dissolved oxygen that must be present in water in order for microorganisms to decompose the organic matter in the water, thus a useful test for the presence of organic waste in water

uses a strong oxidizing agent (dichromate ion in 50% sulfuric acid) to completely breakdown all organic matter in a water sample.

the oxygen decline downstream.

• Further downstream, the water may become so oxygen-depleted that only the most resistant microorganisms and invertebrates can survive.

rivers and lakes that have clear water and low biological productivity.

waters that are rich in organisms and organic materials. Eutrophication is an increase in nutrient levels and biological productivity.

Some toxic inorganic chemicals are released from rocks by ____________, are carried by runoff into lakes or rivers, or percolate into groundwater aquifers.

Some soils contain naturally high concentrations of soluble salts, including toxic selenium and arsenic.

Salts, such as _________-, that are non-toxic at low concentrations also can be mobilized by irrigation and concentrated by evaporation, reaching levels that are toxic for many plants and animals.

Globally, 20% of the world’s irrigated farmland is estimated to be affected by __________

Acids are released as by-products of industrial processes, such as leather tanning, metal smelting and plating, petroleum distillation ,and organic chemical synthesis

is an especially important source of acid water pollution.

due to acid precipitation has been reported in about 200lakes in the Adirondack Mountains of New York State and in several thousand lakes in eastern Quebec, Canada.

Include drugs, pesticides, and other industrial substances

from shipwrecks and well blowouts, such as the 2010explosionofthe Deepwater Horizon in the Gulf of Mexico, can be disastrous for ecosystems and local economies.

Erosion and runoff from croplands contribute about 25 billion metric tons of soil, sediment, and suspended solids to world surface waters each year