JoSS: Joy of Sharing Science No: 3

Joy of Sharing Science
the contamination of freshwater with pesticides since they tend to reach water through
watering systems of plants and soils and their runoffs. From the chemical analysis of
those water samples, it is evident that more than 150 chemicals from each major class
are utilized for agricultural purposes. It may take centuries for water to purify itself
from toxic chemicals with high cost and complex chemical systems if there is any way
to solve this issue. Thus, the United States Geological Survey has found out that the
concentration is exceeding the legal guidelines about pesticides.
The Hazardous Effects of Pesticides on the Environment
Transformation products are chemical substances that emerged from contaminants
by a combination of biotic and abiotic processes such as advanced oxidation,
photolysis, hydrolysis and can be found in wastewater pretreatment plants. Some
frameworks such as water solubility and persistence define TPs. Additionally, such
parameters by being correlated with soil-sorption constant (Koc), the octanol/water
partition coefficient (Kow), and half-life in soil (DT50) also define the toxicity and
are being used to classify pesticides. These are two main classifications of
pesticides:
1. The main characteristics of this type of pesticides are hydrophobicity, persistence,
and most importantly bioaccumulation since these chemical compounds are able to
establish strong bonds with soil. Even though most of the hydrophobic pesticides
are banned worldwide due to its bioaccumulation, in urban areas, organochlorine
DDT, endosulfan, endrin, heptachlor, lindane, and their TPs are currently used for
agricultural purposes.
2. Another type of TPs is polar pesticides that are commonly regarded as herbicides
while they can be used as carbamates, fungicides, and other organophosphorus
insecticides TPs. They stand a higher risk of contamination to soil and thus the
groundwater provided to the population due to the fact that it could spread on soil
through runoffs. The most recent study focuses on different biotic and abiotic
pathways that could be followed such as hydrolysis, methylation, and ring cleavage
that would result in the productions of these toxicants. The efficacy of
contamination depends on several parameters, and most importantly on the
chemical classification these chemicals belong to. After long surveys and analysis of
samples collected from different regions, the correlation between the absorption of
pesticides and TPs into the soil and the organic matter content of the soil is found as
follows: The increase in the organic matter content in soil results in the enhanced
absorption of these toxicants. The absorption constant of soil is directly
proportional to soil’s capacity to hold positively charged ions since most of the
pesticides are also positively charged, and it enhances the quality of the transaction
of these ions and the bonds created during this process. For the removal of these
chemicals, strong mineral acids are required and the scientists consider it almost