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The Invisible Polluter: Do you know what non-point source pollution is?
Nonpoint Source Pollution (NPS) refers to widespread pollution of water or air that cannot be traced to a single specific source. This pollution often results from the cumulative effect of small amounts of pollutants accumulating over a large area. In contrast, point source pollution is caused by a single source. Non-point source pollution often results from conditions such as land runoff, precipitation, aerosol deposition, drainage, seepage or hydrological changes (such as rainfall and snowmelt), making it difficult to trace its origin.
Non-point source water pollution affects water bodies, such as polluted runoff from agricultural areas into rivers, or debris carried by winds to the ocean.
Nonpoint source pollution is difficult to control because it originates from many different daily activities of people, such as lawn fertilization, pesticide use, road construction or building construction. Controlling this type of pollution requires improved management of urban and suburban areas, agricultural operations, forestry operations and dock management.
Main types of non-point source water pollution
Sediment
Sediments (loose soil) include silt (fine particles) and suspended solids (larger particles). Sediments may enter surface waters through surface runoff from eroding river banks and improper vegetation cover in urban and rural lands. Sediments cloud the water and reduce the amount of light reaching deeper waters, which can inhibit the growth of underwater plants and therefore affect species such as fish and shellfish that rely on them.
Nutrient
Nutrient materials are primarily inorganic materials derived from runoff, landfills, livestock operations, and farmland. The two main nutrients of concern are phosphorus and nitrogen. Excessive phosphorus and nitrogen can lead to eutrophication of water bodies, promote the growth of microalgae, cause algae blooms, and affect water quality.
Excess phosphorus and nitrogen can lead to eutrophication of water bodies and can trigger toxic algae blooms that threaten drinking water sources.
Toxic pollutants and chemicals
Toxic chemicals include organic and inorganic compounds, such as heavy metals and degradation-resistant toxic substances, and may originate from human sewage, industrial emissions, and agricultural chemicals.
Pathogen
Pathogens are bacteria and viruses that can cause disease in water and are commonly found in public drinking water supplies, such as Cryptosporidium and Salmonella.
Sources of non-point source pollution
Urban and suburban areas
Cities and suburbs have become the main source of non-point source pollution due to their large paved areas. Rainwater flows over these impermeable surfaces, carrying contaminants into the soil and affecting nearby water bodies.
Agricultural operations
Nutrient substances such as chemical fertilizers and animal manure as well as agricultural product residues applied in farmland will enter water bodies through runoff, causing water quality to deteriorate.
Climate Subsidence
Pollutants discharged from industries settle to the ground via aerosols, forming non-point source pollution.
Highway runoff
Highway runoff is also a component of non-point source pollution due to the impact of traffic and pavement maintenance materials.
Methods to control non-point source pollution
Control methods in urban and suburban areas
The application of technologies such as lawn buffer strips, detention ponds and porous paving can effectively reduce pollution in stormwater runoff.
Agricultural control methods
Farmers can use soil conservation techniques such as planting shelter belts and wheat to reduce runoff and improve fertilizer management.
Forestry control methods
Properly planned logging roads and tree planting will help reduce soil erosion and control runoff.
Non-point source pollution is caused by many reasons. Although many control methods are known, there are still many challenges in implementation. People should think about, what can we do in our daily lives to reduce the impact of these invisible polluters?
