Do the chemicals in our rivers tell us who we are?

Leonardo da Vinci provided us with profound hydrologic insight, albeit unintentionally, when he stated, “In rivers, the water that you touch is the last of what has passed and the first of that which comes; so present with time.” Rivers continuously drain water from our landscapes and carry it to the oceans. After it rains, the water moves both over the land surface and underneath the ground towards the river.  When you look at a river you’re seeing the same water that once blanketed the land for a brief moment. As the water makes its way into the river, we often see it take small items along for the ride, like soils, stones, woodchips, newspapers, and empty soda cans. However, there is something else being carried that we don’t see; chemicals. Unlike heavy items like trash, the chemicals cannot settle out of the water downstream because they go through a transformation and instantly become a part of the water. Hydrologists call these chemicals the dissolved load of a river. As we apply nutrient fertilizers to our crops to grow food for our families, the chemicals (nitrate, phosphate) become a part of the dissolved load.  As we build our houses and roads, the chemicals (salts, carbonates) follow the pipes into our rivers. As we improve our quality of life and innovate new technologies, the chemicals of raw materials (sulfur, lead, arsenic, PCBs, PFOAs) enter the dissolved load.  As we drink more coffee, cure disease, and fight our wars, the chemicals involved (caffeine, hormones, amphetamines, antibacterials, radioactive uranium and tritium) show up in our rivers. 

Water discharge from a pipe (iStockphoto/Viktor Balabanov from ScienceDaily, 2008)

Although these chemicals in our rivers might be fascinating to anthropologists, they are catastrophic for our environment and our health. Nitrates and phosphates cause huge algal blooms in stagnant water (like beaches) that suck up all of the oxygen and kill fish, crabs, and other marine life. Salts, carbonates, and metals can create toxicity for the delicate plant life that relies on the water. These chemicals also attract invasive plants that are tougher, and that can outcompete the native species and eventually lead to a loss of biodiversity.  Organic chemicals like antibacterials, hormones, and plastics are carcinogenic for the animals that rely on the water and can cause reproductive issues, physical and mental abnormalities, and death. If these chemicals continue to show up in our rivers, we can ultimately lose the ecosystem services that we are dependent on for our quality of life, like seafood, clean drinking water, sewage disposal, and recreational spaces. If aliens ever landed on Earth and wanted to know more about us, I’d tell them to look in our water.

People have significantly altered the landscape, and the fingerprints of human activities show up in the water (Kaushal & Belt, 2012)