68
S. Mohapatra et al.
3.2 Various Types of Natural Attenuation Processes
3.2.1 Physical Parameters and Hydrogeological Conditions
Three major factors responsible for attenuating pharmaceuticals in a river are hydrogeological conditions, dissolved organic matter, and physical conditions prevailing
in an aquatic environment (Yang et al. 2017; Das et al. 2016; Kumar et al. 2019b,
c). The physical parameters include the flow rate of water in the river, penetration
depth of sunlight, depth of water column, ambient temperature, turbulence, mixing,
and rate of exfiltration and infiltration. Immediately, after discharge of wastewater
into the river bodies, pharmaceuticals undergo rapid dilution depending on the flow
conditions of the river. The aqueous concentrations were inversely proportional to
flow in the river. In an Indian river receiving sewage and industrial effluents, the
concentration of pharmaceuticals encountered in monsoon was substantially lower
due to the higher flow rates encountered in the monsoon season (Mutiyar et al. 2018).
DOM can enhance the mobility of hydrophobic pharmaceuticals, such as
diclofenac, bezafibrate, and gemfibrozil (Yang et al. 2017). Various researchers have
studied the correlation between the concentration of pharmaceuticals and various
physicochemical and water quality parameters, including pH, temperature, oxidation–reduction potential (ORP), chemical oxygen demand (COD), turbidity, and electrical conductivity (Yang et al. 2017). A negative correlation was obtained between
the total concentration of pharmaceuticals and temperature and ORP, while a positive correlation was observed with COD and turbidity (Yang et al. 2017). Both
temperature and redox potential were identified as important parameters affecting
the attenuation of pharmaceuticals (Massmann et al. 2006, 2008).
Regionally, the concentration of pharmaceuticals in a river is highly variable.
Medicine consumption patterns, hydrology, sewage water management practices,
and the extent of urbanization may all affect the concentration of pharmaceuticals
in a river. A significant difference in the spatial distribution of 33 pharmaceuticals
was seen other than for carbamazepine, which has been reported to be resistant to
biodegradation (Burns et al. 2018). A host of environmental processes, including instream degradation and dilution, may be prevalent in rivers flowing in geographically
distinct domains. These factors may vary to differing extents in neighboring rivers
leading to varying spatial concentration patterns of pharmaceuticals. For example,
Burns et al. (2018) studied the attenuation processes in two adjacent rivers. In one
river, the reduction in concentration moving downstream was symptomatic of instream removal processes, such as photolysis and microbial degradation, while a
fluctuating concentration of various pharmaceuticals was observed in the neighboring
river due to a complex dynamics between dilution and merging of other polluting
sources (i.e., tributaries and urban drainage) with the river.
Variation in flow rate is one of the major factors that cause temporal variation in
the concentration of pharmaceuticals. Low flow rate elevates the concentration and
vice versa. Additionally, higher usage of pharmaceuticals during winter or decreased
S. Mohapatra et al.
3.2 Various Types of Natural Attenuation Processes
3.2.1 Physical Parameters and Hydrogeological Conditions
Three major factors responsible for attenuating pharmaceuticals in a river are hydrogeological conditions, dissolved organic matter, and physical conditions prevailing
in an aquatic environment (Yang et al. 2017; Das et al. 2016; Kumar et al. 2019b,
c). The physical parameters include the flow rate of water in the river, penetration
depth of sunlight, depth of water column, ambient temperature, turbulence, mixing,
and rate of exfiltration and infiltration. Immediately, after discharge of wastewater
into the river bodies, pharmaceuticals undergo rapid dilution depending on the flow
conditions of the river. The aqueous concentrations were inversely proportional to
flow in the river. In an Indian river receiving sewage and industrial effluents, the
concentration of pharmaceuticals encountered in monsoon was substantially lower
due to the higher flow rates encountered in the monsoon season (Mutiyar et al. 2018).
DOM can enhance the mobility of hydrophobic pharmaceuticals, such as
diclofenac, bezafibrate, and gemfibrozil (Yang et al. 2017). Various researchers have
studied the correlation between the concentration of pharmaceuticals and various
physicochemical and water quality parameters, including pH, temperature, oxidation–reduction potential (ORP), chemical oxygen demand (COD), turbidity, and electrical conductivity (Yang et al. 2017). A negative correlation was obtained between
the total concentration of pharmaceuticals and temperature and ORP, while a positive correlation was observed with COD and turbidity (Yang et al. 2017). Both
temperature and redox potential were identified as important parameters affecting
the attenuation of pharmaceuticals (Massmann et al. 2006, 2008).
Regionally, the concentration of pharmaceuticals in a river is highly variable.
Medicine consumption patterns, hydrology, sewage water management practices,
and the extent of urbanization may all affect the concentration of pharmaceuticals
in a river. A significant difference in the spatial distribution of 33 pharmaceuticals
was seen other than for carbamazepine, which has been reported to be resistant to
biodegradation (Burns et al. 2018). A host of environmental processes, including instream degradation and dilution, may be prevalent in rivers flowing in geographically
distinct domains. These factors may vary to differing extents in neighboring rivers
leading to varying spatial concentration patterns of pharmaceuticals. For example,
Burns et al. (2018) studied the attenuation processes in two adjacent rivers. In one
river, the reduction in concentration moving downstream was symptomatic of instream removal processes, such as photolysis and microbial degradation, while a
fluctuating concentration of various pharmaceuticals was observed in the neighboring
river due to a complex dynamics between dilution and merging of other polluting
sources (i.e., tributaries and urban drainage) with the river.
Variation in flow rate is one of the major factors that cause temporal variation in
the concentration of pharmaceuticals. Low flow rate elevates the concentration and
vice versa. Additionally, higher usage of pharmaceuticals during winter or decreased