DISCUSSION
Zone – I (GR-12 – GR-13) -Urban:- The present zone is located
between Nadwa and Hanuman Setu. The variation of opaque phytoclast and
degraded brown organic matter with fungal spores and filamentous algae
suggests that the degradation is moderate to high in this zone with low
oxygenation state in the sediment. The various palynofacies association
has been captured and is depicted in Plate-1. The grain distribution
shows very fine sand to silty sediment deposits in this zone of Gomati
River indicating very low energy conditions with a unimodal depositional
system in the flow regime. The statistical inference from the grain size
shows that the grain are unimodal with poor sorting, negatively skewed
(-0.253 and -0.418) in coarse to very coarse owing to very fine sand
category, while the kurtosis suggest leptokurtic and mesokurtic
statistics (Folk and Ward 1957; Blott and Pye 2001). The zone is
identified with poor winnowing and variable fluvial energy conditions
(Folk and Ward, 1957; Friedman 1967; Kanahaiya et al., 2016; Padhi et
al., 2017, Kholia et al., 2021). The present zone is influenced by high
levels of anthropogenic activity and can be held responsible for the
degradation of particulate organic matter (Xenopoulos et al., 2021).
Recently it has been globally recognized that human activities can
modify the organic matter either in dissolved or particulate form. These
can be adhered to the natural system due to land-use change, climate
change, nutrient pollution, browning, wildfires, etc (Xenopoulos et al.,
2021). The high opaque phytoclast percent vary effectively with slight
enhancement of coarser grain fraction and is reflected in PCA biplot
(Figure 6). As the river energy condition in the mature stage is low in
the Gomati River, the winnowing of sediments by channel action in the
flow regime with changeable energy conditions may affect the
palynofacies is least anticipated. Alternatively, due to low water
levels after the southwest (SW) monsoon allows high fertile sediments
for agriculture practice in these parts of flood plains. The continous
use of the agriculture practice since long is also one of the reasons
for deterioration of palynofacies. The ratio of degraded charcoal (Dc)
to burnt charcoal (Bc) ranges between 1.05-0.71 suggesting burning
activity along the river channel as an evidence of human activity
(Xenopoulos et al., 2021). The occurrence of opaque phytoclast (degraded
or burnt) is a result of either prolonged transportation or natural/
anthropogenic fires (Mendonça Filho et al., 2011a). High encroachment of
human population along the rivers is evidenced world wide and this is
also a typical situation in and around the Lucknow city. Furthermore,
the ratio of the cuticle (C) to tracheid (T) is 0.41-0.31 representing
low vegetation in the surrounding and the present status of tracheids
and cuticles may be transported by the channel as the river is
perennial. Palynofacies and grain size analyses suggest that the
moderate to high degradation due to anthropogenic reasons along the
river banks in the urban reaches and organic matter deterioration due to
development projects and encroachment on the flood plain of the Gomati
River cannot be ignored. The changes in the organic matter association
is also a factor of the dissolved organic matter that is subjected to
the anthropogenic responses along the river channel and affects the
flood plains to a great extent (Xenopoulos et al., 2021).
Zone – II (GR-8 – GR-11) - Urban Fringe:- This zone lies
between Gaughat to Gaughat3. The variation of terrestrial organic matter
is primarily controlled by degraded brown OM and opaque phtoclast and
variable percentages of amorphous OM and Mycelium fungal hyphae.
The details of the palynofacies association for the shown in Plate-2.
The opaque phytoclast comprise trees/ woody material being transported
onto the flood plains of the Gomati River during precipitation time.
Also, the portion of opaque phytoclast shows angular to sub-angular
edges suggesting low distance transport of phytoclast from nearby
source. It is also noteworthy that the AOM and fungal remains show an
appreciable variation reflecting slowly flowing/ near stagnant
conditions and high degradation of organic matter as a consequence of
post-deposition in the flood plains. The Dc/Bc ratio varies between 3-5
indicating higher degraded opaque phytoclast in the river bank as a
result of post burial activity of palynofacies matter. The C/T ratio
varies 0.9-2 showing high leafy remains i.e. cuticular remains and also
suggest proximal region of source area. The high degradation of
palynofacies may also be addressed to human practices such as
agriculture along the flood banks. This zone also experiences seasonal
vegetation of creeping plants and hence records of high cuticles may be
a plausible explanation. The rise in land acquisition along the river is
also be a probable reason for deteriorating palynofacies in this
transitional part of urban suburbs. The charcoal particles have also
been recorded in coarse-grained, high energy, organic-poor sediments
such as distributary channel sands and point bars in the flood plains
(Denison and Fowler, 1980; Parry et al., 1981; Tyson, 1995; Mendonça
Filho et al., 2011a). The grain size distribution shows both silt and
sand content in vaiable proportions indicating a bimodal system and
suggests varying energy conditions. The negative skewness suggest fine
grained deposition alongwith poor sorting, and mesokurtic and
platykurtic nature of sediments in the flood plain. The incision in the
channel flow has also been recognised in the Gomati channel by Thakur et
al., (2009). The plausible explanation of palynofacies and grain size
relatio in context to brown degraded OM and opaque phytoclast is also
ascertained using the PCA analysis in PC1 and PC2 (Figure 6).
Zone – III (GR-4 – GR-7) - Urban Fringe to Sub-urban:- The
localities Raitha to Ghaila marks this zone. In this zone, terrestrial
organic matter is marked by a high percentage of degraded brown OM,
filamentous algae, and opaque phytoclast with a small percentage of AOM
that suggests low energy of the river. In order to define the fate of
the palynofacies the images are captured and shown in Plate-3. Here,
different palynomorphs like thecamoebians, fungal spores, and
cyanobacterial remains are also recorded which indicates that this zone
is low polluted and disturbed that prevented oxidation of palynofacies
matter and allowed preservation in finely deposited silt and sand
fraction. Based on the grain size distribution low to moderate energy
conditions is interpreted. Here it can also be observed that the channel
is nearly straight with minimal meandering. The negative skewness
suggests fine grained sediment with platykurtic that implies mixing of
sediment from two sources with poor sorting in this zone that can be
attributed to channel sediments and local weathering. The zone exhibits
a deposition where the natural resources are less affected by the
anthropogenic activities. The Dc/Bc ratio varies between 3.05 to 6.5
suggesting high opaque phytoclast(degraded) due to the long
transportation of plant material (Mendonça Filho et al., 2011a). The C/T
ratio varies from 0.59 to 1.22 showing high tracheid record indicating
the prevalence of woody material. The present finding agrees with the
silt and very fine sand grain texture with degraded brown OM,
pollen/spore, Thecamoebians, cyanobacteria, and filamentous algae
explaining the highest variability in PC1 and PC2 (Figure 6). The
present association of the phytoclasts is also influenced by
hydrodynamic equivalence effects. Being relatively large and dense
organic particles, woody debris mainly comprised of degraded brown is
often concentrated in sediments rich in coarse silt and/or very fine
sand (Tyson, 1993).
Zone – IV (GR-1 – GR-3) - Sub-urban:- This zone comprises the
area between Atariya to Chandrika Devi. The characteristic palynofacies
component comprises high proportions of the degraded brown OM followed
by filamentous algae and variable proportions of opaque phytoclasts,
fungal remains, and other organic matter. The major palynofacies
association are shown in Plate -4 to explain the sub-urban region. The
variable degree of degraded brown OM, filamentous algae and AOM points
to both prolong and local transportation suggesting palynofacies
deposition from autochthonous or allochthonous sources. This can be
explained by the angular to sub-angular and sub-rounded opaque
phytoclast. It is also noted that the high content of filamentous algae
and fungal/ algal remains (Glomus sp. and Alternaria sp.)
points towards clear and standing water with a low velocity of the
channel and local erosion (Quamar, 2015; Sridhar et al., 2020). The
variation in the AOM shows a certain degree of organic matter
degradation by natural processes during transport by mechanical
breakdown and further by post-deposition burial (Tyson, 1995). The grain
size show negative and positive skewness suggesting fine and coarse
grained sediments that are poorly sorted with platykurtic reflecting the
mixing of sediment source. The palynofacies findings also go in
hand-to-hand with the grain size distribution and it can be effectively
postulated that the variability in palynofacies and grain size
representing a bimodal system of deposition or a mixed environmental
setting. The Dc/Bc ratio is of higher value i.e. 6.7-5.6 advocate major
degraded charcoal deposit, at the same time, C/T ratio ranges between
0.31-1.36 showing equable recurrence of cuticle and tracheids propose
high vegetation within the proximity. The association ofdegraded brown
OM, filamentous algae, and AOM with fine to medium silt and fine sand is
in aggreable reference in PC1 and PC2 (figure 6).
To depict the distribution and destiny of palynofacies in urban and
sub-urban reaches, the various zones outlined above have also been
displayed in ArcGIS to decode the spatial heterogeneity in the Gomati
River flood plain in Lucknow district (Figure 7). The spatial variation
shows that, in comparison to the sub-urban reaches, variability is
developing more quickly throughout the urban regime. It might be argued
that the increasing rate of urbanisation in the periphery areas is
accelerating the degradation of sedimentary organic matter through
development and concretization.