Nitrate is a major contaminant and threat to groundwater quality in Texas and around the U.S., so knowing where this chemical tends to pool will be a help in controlling potential damage, according to a Texas AgriLife Research study.

Dr. Srinivasulu Ale, AgriLife Research geospatial hydrologist at Vernon, and his post-doctoral research associate, Dr. Sriroop Chaudhuri, completed a study of groundwater nitrate concentrations and recentlyhad their results published in the Journal of Environmental Quality.

The research paper was co-authored by Dr. Paul DeLaune, AgriLife Research environmental soil scientist, and Dr. Nithya Rajan, AgriLife Research agronomist, both at Vernon.

Results indicated that groundwater nitrate concentrations have significantly increased in several Rolling Plains counties since the 1960s. In 25 counties, morethan 30 percent of the groundwater quality observations exceeded the U.S. Environmental Protection Agency maximum contamination level for nitrate in the 2000s as compared to eight counties in the 1960s, they said.

“This suggests that more counties in the state are getting affected by high nitrate levels in the groundwater over time,” Ale said.

This groundwater, if used for irrigation with accounting for the high nitrate concentration and domestic purposes, could have serious environmental and health implications, he said. Ingestion of high nitrate groundwater can cause methemoglobinemia, commonly known as ‘blue baby syndrome,’ in infants less than six months of age.

Although earlier studies reported high levels of nitrate, exceeding the maximum contaminant level for drinking water, in different parts of Texas, a comprehensive statewide assessment of the groundwater nitrate contamination over a longer time period was lacking, Ale said.

 “We assessed 50 years (1960 to 2010) of groundwater nitrate data, as available from the Texas Water Development Board, and employed different statistical and geospatial techniques to study long-term trends in groundwater nitrate contamination across Texas,” Ale said. “We also identified the major factors affecting nitrate contamination.”

A distinct spatial clustering of high nitrate counties was observed in the Rolling Plains and parts of the Southern High Plains in recent times, Chaudhuri said.

“In the course of our study, we found that counties that have high nitrate contamination are generally associated with or surrounded by counties having similarly high nitrate levels in the groundwater,” he said. “The same was true with low-nitrate counties clumping together with other low-nitrate counties.”