2022 World Water Day is dedicated to groundwater and its preservation from over-usage and pollution due to agricultural activities.
Water is one of the essential inorganic components for life whose movement defines the so-called nutrient cycle.
In addition, water as some other elements (e.g. Carbon) cyclically passes from environment to organisms carrying out the biogeochemical cycle.
Only 3% of available water on Earth consists of fresh water, the remaining 97% consists of salt water.
Fresh water used in irrigation and other human activities is found both in rivers and lakes and as a “submerged resource” in groundwater, so its pollution and depletion adversely affect human health.
WATER BIOGEOCHEMICAL CYCLE AND GROUNDWATER
Water biogeochemical cycle starts from evaporation of liquid water constituting the hydrosphere. Through condensation processes, atmospheric water vapor obtained, along with substances allowing the constitution of the condensation nuclei, ensures the reintegration of water in the form of precipitation, reaching the biosphere.
Last stages of the cycle include infiltration and percolation: part of the precipitation water is absorbed by the soil, filling lakes and rivers or feeding the groundwater, considered the largest reserves of freshwater on Earth.
In order to reach the deepest soil layers and form groundwater, it’s necessary that the soil has an impermeable layer (clay layer, rocks) and therefore doesn’t allow the passage of water but tends to preserve it: its ability to retain H2O depends on the texture.
Groundwater is easily subject to pollution by soil agents, for example nitrate leaching, where large quantities of free nitrate present in the outermost layers of the soil are removed from the percolation water towards the innermost layers until reaching the aquifer (e.g. due to heavy rainfall).
Biogeochemical cycle of water
POLLUTANTS OF WATER
There are 6 pollutants of water:
- Pathogen agents such as coliforms that must be completely absent from drinking water;
- Biodegradable waste;
- Inorganic water-soluble chemicals, can make the water not drinkable, lower the productivity of agricultural crops and damage industrial plants;
- Inorganic nutrients such as nitrates, phosphates and sulphates which may cause eutrophication (natural event that originates in abundant areas of nutrients, especially in shallow water and with little exchanges, and that causes overdevelopment of primary producers resulting in change of the environment)
- Sediments and particulate matter;
- Soluble radioactive isotopes
Agriculture is one of the main causes of groundwater contamination, caused by pesticides and fertilizers that provide large amounts of nitrates on soil, generating an overabundance of the necessary inorganic nutrients.
To fight the conversion of nutrients into pollutants, DEMETRA project aims to deal with the delicate “nitrate issue” that afflicts the NVZs scattered throughout Puglia, through an approach based on monitoring technologies and the application of agronomic best practices.
Monitoring agricultural activities and nutrients can lead to identifying sources of contamination and planning proper intakes. In addition, knowing the nitrogen content of the soil and the impact of the activities is essential to implement the right agronomic techniques to reduce the risk of contamination.
Only thorough a more conscious and sustainable agriculture it will be possible to ensure that natural sources of water continue to exist.