Chloride levels above the recommended federal criteria set to protect aquatic life were found in more than 40 percent of urban streams tested. The study was released today by the U.S. Geological Survey (USGS). Elevated chloride can inhibit plant growth, impair reproduction, and reduce the diversity of organisms in streams.
The effect of chloride on drinking-water wells was lower. Scientists found chloride levels greater than federal standards set for human consumption in fewer than 2 percent of drinking-water wells sampled in the USGS study.
Use of salt for deicing roads and parking lots in the winter is a major source of chloride. Other sources include wastewater treatment, septic systems, and farming operations.
“Safe transportation is a top priority of state and local officials when they use road salt. And clearly salt is an effective deicer that prevents accidents, saves lives, and reduces property losses,” said Matthew C. Larsen, USGS Associate Director for Water. “These findings are not surprising, but rather remind us of the unintended consequences that salt use for deicing may have on our waters. Transportation officials continue to implement innovative alternatives that reduce salt use without compromising safety.”
This comprehensive study examines chloride concentrations in the northern U.S. covering parts of 19 States, including 1,329 wells and 100 streams.
Land use matters
Chloride yields (the amount of chloride delivered per square mile of drainage area) were substantially higher in cities than in farmlands and forests. Urban streams carried 88 tons of chloride per square mile of drainage area. Forest streams carried about 6 tons of chloride per square mile.
Only 4 percent of the streams in agricultural areas had chloride levels that exceeded the recommended federal criteria set to protect aquatic life (compared to more than 40 percent of urban streams). Overall, 15 percent of all streams had chloride levels exceeding the criteria.Chloride concentrations in shallow groundwater (not used for drinking) were 16 times greater in urban areas than in forests, and 4 times greater in urban areas than in agricultural areas.
Highest levels in streams in the winter
In urban streams, the highest levels of chloride (as great as 4,000 parts per million, which is about 20 times higher than the recommended federal criteria) were measured during winter months when salt and other chemicals are used for deicing.
Increases over time
Increases in chloride levels in streams during the last two decades are consistent with overall increases in salt use in the U.S. for deicing.
Increasing chloride yields are linked to the expansion of road networks and parking lots that require deicing, increases in the number of septic systems, increases in wastewater discharge, and increases in saline groundwater from landfills.
Sources can vary locally
Chloride in ground and surface waters comes from many sources including the use and storage of salt for deicing roads, septic systems, wastewater treatment facilities, water softening, animal waste, fertilizers, discharge from landfills, natural sources of salt and brine in geologic deposits, and from natural and human sources in precipitation.
John Mullaney | EurekAlert!
Receding glaciers in Bolivia leave communities at risk
20.10.2016 | European Geosciences Union
UM researchers study vast carbon residue of ocean life
19.10.2016 | University of Miami Rosenstiel School of Marine & Atmospheric Science
Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.
"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...
In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.
A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...
By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.
"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...
COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.
In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...
'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.
Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...
14.10.2016 | Event News
14.10.2016 | Event News
12.10.2016 | Event News
21.10.2016 | Health and Medicine
21.10.2016 | Information Technology
21.10.2016 | Materials Sciences