Monsoon Minimum Research Articles

Multi-year observations of particulate matter and gases over Mumbai: Spatio-temporal variation, oxidation ratios, and secondary aerosols

System of Air quality and weather Forecasting And Research (SAFAR-Mumbai) network hourly observations of air pollutants spanning half a decade are subjected to a Generalized Additive Model (GAM) to investigate the non-linear relationship of PM2.5 to other precursor gases and meteorological parameters. The Effective Degrees of Freedom (EDF), a statistic of GAM quantifying the non-linear relationship, reveals that PM2.5 is highly non-linearly dependent on NH3, SO2, and CO as inferred from the response curves exhibiting at least one inflexion point and threshold responses. PM2.5 is linearly related to NO2 (EDF = 1), while it is non-linearly related to other gases and meteorological parameters (EDF > 2). The frequency distribution of PM2.5 shows a sharp peak at 25 μg m−3 in monsoon and broad peaks in pre-monsoon (peak at 50 μg m−3), post-monsoon (peak at 60 μg m−3) and winter (peak at 100 μg m−3) indicating relatively large variability in winter and post-monsoon. Chemical analysis of PM2.5 shows a high contribution of four major ions in the order of SO42− > Cl− > Na+ > NH4+, mainly associated with anthropogenic and marine sources. The average sulphate oxidation ratio (SOR), nitrogen oxidation ratio (NOR), and neutralization ratio (NR) are up to 0.3, 0.04, and 0.27, respectively, indicating that SO2 is contributing majorly to secondary aerosol production. Monthly concertation of PM2.5, Ozone (O3), CO, NO2, SO2, and NH3 shows U-shaped variability with maximum in winter and minimum in monsoon.

Observations of Inertia Gravity Waves in the Western Pacific and Their Characteristic in the 2015/2016 Quasi‐Biennial Oscillation Disruption

AbstractThe statistical characteristics of inertia‐gravity waves (IGWs) in the troposphere (2–14 km) and lower stratosphere (18–28 km) are analyzed using daily radiosonde observations over six stations in the Western Pacific from 2013 to 2018. Stokes parameter method is used to extract the characteristic parameters of gravity waves (GWs), which are divided into upward and downward propagating waves, and compared with the results of hodograph analysis. In the stratosphere, due to the filtering effect of the background wind field, the IGWs generated in the troposphere mainly propagate eastward with lower frequency range. The tropospheric IGWs have obvious seasonal variation in spectral amplitude and energy, with the maximum in winter and the minimum in monsoon from 2013 to 2018. The stratospheric IGWs are enhanced during phase transition of the quasi‐biennial oscillation, when the enhanced easterly wind appears in the lowest stratosphere, accompanied by enhanced wave energy in the troposphere. During the quasi‐biennial oscillation disruption in late 2015 and early 2016, the tropospheric wave source excites more intense IGWs propagating upward. After reaching the stratosphere, IGWs with slower phase speed are absorbed by the mean flow, dissipating momentum to the lower stratosphere and generating additional enhanced westward forcing, which may have contributed to the development of the easterly wind within the westerly quasi‐biannual oscillation phase.

Monitoring and assessment of Dracaena-based constructed vertical flow wetlands treating textile dye wastewater.

The monitoring and assessment of multiple constructed vertical flow wetlands (CVFWs) treating textile dye wastewater (metanil yellow as dye) are studied covering three seasons. Three CVFWs (CVFW-1, dye—5 mg/l; CVFW-2, dye—50 mg/l; and CVFW-3, dye—100 mg/l) and a control (dye—5 mg/l) were used. The CVFWs with Dracaena (an ornamental plant) efficiently removed contaminants like dye, COD, NH4+-N, and PO43−-P from the wastewater under varying inlet dye concentrations, indicating its dependence on meteorological conditions. Substantial dye removal was observed to be maximum in summer (control, 44.3%; CVFW-1, 75.1%; CVFW-2, 76.1%; CVFW-3, 46%), but lesser in winter (control, 45%; CVFW-1, 73.1%; CVFW-2, 76.8%; CVFW-3, 42.6%) and minimum in monsoon (control, 40.8%; CVFW-1, 63.5%; CVFW-2, 51.6%; CVFW-3, 37.1%), respectively. Efficiency was less in CVFW-3 as it observed plant stress due to higher inlet dye concentration. COD removal was higher in winter, followed by summer and monsoon. A first-order kinetic model was used to investigate the efficiency of the CVFW system w.r.t. contaminant removal. Various functional groups were characterized using Fourier transform infrared spectroscopy (FTIR) from the inlet and outlet water samples of different CVFWs. The Dracaena accumulated various elements and oxides during the treatment with no stress on its health. No effects on plant health highlight the suitability of Dracaena for textile wastewater treatment. The results were validated using statistical tools like the Mann–Whitney U test and principal component analysis (PCA).Supplementary InformationThe online version contains supplementary material available at 10.1007/s10661-022-10415-y.

Evaluation of water quality and dam for sustaining the fish population dynamics

Bhagirathi is a Himalayan River, which flows in Uttrakashi district in Uttarakhand state. It is one of the most important streams of the Ganga River. This river is famous for dam construction and fisheries development. The fishes of commercial importance in cold water are Mahaseer, Snow Trout. The fish production depends on the physical, chemical as well as biological qualities of water. In the present paper, water quality evaluation and dam in the sustaining fish population dynamics have been reviewed to make aware the fish culturist and environmentalist about the water quality factors which influence health of a pond and to increase the fish yields to meet the growing demands of present time scenario of the our country. The construction of dams causes many problems. Water quality and discharge of water from the dam wall systems also indirectly affect the fish populations. In this study, we also review some of the important impacts associated with dams and their recommended mitigation measures. There is a negative impact on fish population dynamics, especially for downstream habits due to dams. Water quality is measured like temperature, turbidity, carbon dioxide, pH, alkalinity, hardness, BOD, TDS, Turbidity. The maximum oxygen content of water was recorded in January 13.02 ± 0.166 mg l−1 and minimum 9.4 ± 0.05 mg l−1 in July in site I phase I (before the reservoir dam wall). While in site II and phase I (After the dam), the maximum DO was observed in the month of January of 12.1 mg l−1 and minimum in July of 8.93 mg l−1. This is because water level is minimized in site II almost dried in winter. The CO2 of the Maneri Bhali phase I -Site I (before dam) was recorded maximum in April 3.10 ± 0.012 mg l−1. In Maneri Bhali phase I -Site II (After dam), the CO2 was recorded maximum 3.01 ± 0.003 mg l−1 in the month July. The river of Garhwal Himalaya harbors a rich aquatic diversity, the most common endemic fish species that inhabit this fresh water is the Schizothorax species. The maximum no. of fish were observed in winter and minimum in monsoon. At present, the production of these fishes from the streams is very poor and is not well managed from recreational and conservation point of view. If such is developed properly, it can have revenue potential for our state government. Sports, fisheries, tourism should be promoted.

A year-long study on PM2.5 and its carbonaceous components over eastern Himalaya in India: Contributions of local and transported fossil fuel and biomass burning during premonsoon

A year-long (March 2019–February 2020) study on the characterization of fine mode carbonaceous aerosols has been conducted over a high altitude urban atmosphere, Darjeeling (27.01°N, 88.15°E, 2200 m asl) in eastern Himalaya. The fine mode aerosol (PM2.5; 41.7 ± 23.7 μgm−3), total carbonaceous aerosols (TCA; 19.8 ± 7.7 μgm−3), organic carbon (OC; 8.0 ± 3.9 μgm−3) and elemental carbon (EC; 2.0 ± 0.9 μgm−3) exhibited similar seasonal variability with the highest abundance during winter followed by premonsoon, postmonsoon and minimum in monsoon. The OC:EC varied over a range of 2.8–19.4 whereas the secondary organic carbon ranged between 1.9 and 17.1 μgm−3 respectively. Higher PM2.5 associated with higher winds and elevated mixing layer depth suggest a strong influence of regional and long-range transport. In addition to the usual morning and evening rush-hour peaks, the impact of low land plain regions driven by up-slope valley winds was observed for the carbonaceous components. A novel approach has been taken to find out the individual contributions from the local and transported fossil fuel, biomass burning, and biogenic sources to OC and EC during premonsoon. We observed that the local fossil fuel (43%) contributions dominated over the biomass burning (39%) for EC whereas the contributions of local biomass burning and the local fossil fuel were same (46%) for OC. EC exhibited a higher contribution (18%) from the regional/long-range transport compared to OC (8%). IGP and Nepal were found to be the maximum contributing long distant source regions for the carbonaceous aerosol loading over eastern Himalaya. Such individual source apportionment of carbonaceous aerosols over eastern Himalaya makes the study unique and first-ever of its kind and immensely helpful for building robust mitigation action plans.

Seasonal food preferences and group activity pattern of Blackbuck Antilope cervicapra (L., 1758) (Mammalia: Cetartiodactyla: Bovidae) in a semi-arid region of western Haryana, India

To evaluate food preferences and group activity patterns, a fragmented population of Blackbuck Antilope cervicapra was selected for observation in a semi-arid ecosystem of western Haryana. A field survey was conducted fortnightly, from dawn to dusk, between September 2019 and August 2020, covering every season. Scan sampling and quadrat methods were used to record data on group size and vegetation. Group sizes ranged from 3 to 72 individuals. Based on visual observation, blackbuck seasonally consumed 26 species belonging to 25 families with varied preferences, out of a total of 53 plant species documented from the study site. Some plant species with high medicinal and therapeutic values were preferred, including Artemisia scoparia, Cucumis callous, Ziziphus jujuba, and Ziziphus nummularia. Unlike most herbivores, Blackbuck also consumed the toxic and medicinally rich Calotropis procera. We suggest that zoos which house blackbuck include these preferred wild plant species in their diet. Observations on group activity were analyzed on hourly, monthly and seasonal bases, and converted into time percentages. Group foraging activity was at a maximum in the monsoon (62%) and minimum in winter (50%), followed by resting: maximum in winter (21%) and minimum (12%) in monsoon, largely influenced by food availability. Foraging/walking ratio was at a maximum (5.2) in monsoon and minimum (3.1) in winter, and was correlated with the number of group sightings (maximum in winter and minimum in monsoon) in nearby farmland, when the animals faced food scarcity in their natural habitat and fed on crops.

Seasonal variation of mountain-valley wind circulation and surface layer parameters over the mountainous terrain of the northeastern region of India

Mountainous topography and solar elevation angle have a significant influence on the wind circulation and energy exchange over a complex region. Here, the seasonal variation of mountain-valley wind circulation (MVWC) and surface layer parameters have been presented over a hilly station of northeastern India. For the study, quick-response sonic anemometer data have been utilized. The solar elevation angle varies from 85° to 43° in different seasons and controls the MVWC over the terrain. MVWC was dominated in winter (WN), pre-monsoon (PM), and post-monsoon (PMN) seasons, while the synoptic wind predominates the wind direction over the terrain in monsoon (MN). In WN and PM, nighttime heat transmission from the atmosphere to the ground was −10 to −20 W m−2, while the minimum in MN and PMN was −3 to −7 W m−2. The net seasonal daily mean sensible heat flux (H) values from the surface to the atmosphere were 42 W m−2, 58 W m−2, 35 W m−2, and 34 W m−2 in WN, PM, MN, and PMN. In MN, the average daytime temperature was 8 °C, 0.5 °C, and 3 °C higher and at night was 9.5 °C, 2 °C, and 4.5 °C higher than the WN, PM, and PMN. In WN, PM, and PMN, the momentum flux had a higher value of about 2 to 3 h after the maximum value in H was attained at the 6-m and 10-m levels. The daytime turbulence kinetic energy was higher by 99%, 56%, 72%, and 93% than the nighttime during WN, PM, MN, and PMN.

Exploring spatial and temporal trends of diurnal temperature range in the region of the Subarnarekha river basin India

This study analyzed the spatial and temporal trends of diurnal temperature range (DTR) for 35-years (1983–2017) in the region of the Subarnarekha river basin of Jharkhand, India. The daily data of maximum temperature (Tmax) and minimum temperature (Tmin) were habituated to compute the DTR, whereas rainfall data is used to measure its relationship with DTR, on a monthly annual and seasonal basis. Mann–Kendall test and Sen’s slope method has been used to detect the increasing or decreasing trends in climatic data with their statistical significance. The annual mean DTR of the basin is 11.97 °C With a maximum in pre-monsoon (16.36 °C) and minimum in monsoon (6.94 °C). A significant negative trend (− 0.31 °C/decade) was observed in annual DTR over the basin. On a seasonal basis, all four seasons show a negative trend in DTR with the largest significant decreasing trend in the pre-monsoon season (− 0.49 °C/decade). On an annual and seasonal basis, a significant negative correlation between DTR and rainfall is found, indicating that rainfall has a significant impact on the variation of DTR in this basin. A concomitant increase in rainfall might be one of the possible causes of the decreases in DTR in the basin.

Diatom flora of Hasina pond, Morang, Nepal

Epiphytic diatoms of Hasina pond were studied during winter, summer, and monson seasons in 2014-2015. Samples were collected by squeezing submerged roots and leaves of hydrophytes and frustules were cleaned using nitric acid. A total 59 diatoms under 27 genera and 19 families were reported among which 33 diatoms were new to the country. Epithemia adnata, Rhopalodia gibba, Gomphonema truncatum, Nitzschia palea, Ulnaria acus, U. ulna and Pinnularia amabilis were dominant in the pond. Diatom species were found maximum in summer (40%) and minimum in monsoon (28%) seasons.

Observations of trace gases, photolysis rate coefficients and model simulations over semi-arid region, India

Continuous ground-based measurements of CO, SO2 and NO2 were carried out in a semi-arid rural area, Anantapur [14.62 0N, 77.65 0E], Southern India, for the period January 2012–December 2012. The maximum CO concentration was observed in winter (310 ± 17 ppbv) followed by summer (180 ± 21 ppbv) and post monsoon (174 ± 20 ppbv), while the minimum in monsoon (72 ± 9 ppbv). Seasonal mean NO2/NOx ratios for monsoon, post monsoon, winter and summer were about 0.88, 0.91, 0.76 and 0.80 respectively, indicating a higher conversion of NO to NO2 over the measurement site. Monthly mean low SO2 mixing ratio was found (0.46 ± 0.02 ppbv) in monsoon and high (2.42 ± 0.21 ppbv) in winter. Keeping the emissions aside, the levels of CO, SO2 and NO2 were influenced by meteorology, urban effects and trans-boundary transport in the lower troposphere. Atmospheric boundary layer (ABL) had the good correlation coefficient (R = 0.76) with solar radiation during daytime, while it was mainly correlated with wind speed during night time (R = 0.42). Diurnal trend of atmospheric visibility was found to be maximum during noon times at around (14:00–16:00 h) about 76 k.m. and minimum during morning periods (06:00–08:00 h) about 45 k.m. A strong positive correlation was observed between BC and CO (R = 0.71) with an average slope, suggesting common or proximate sources likely to be traffic emissions contribution for the production of BC and CO. The SO2/NOx and CO/NOx study were strongly suggested that mobile sources were larger contributors over the site and the evidence of transport of emissions from other surrounding regions. Tropospheric Ultraviolet Visible (TUV) radiative transfer model was used to calculate the Photolysis rate coefficients (J(O3), J(NO2)). Chemical box model (NCAR-MM) was used to simulate diurnal variation of CO and the results were reported.

Satellite-sensed tropospheric NO2 patterns and anomalies over Indus, Ganges, Brahmaputra, and Meghna river basins

ABSTRACTThis study presents trends, seasonality, hot spots, and anomalies of tropospheric NO2 pollution over four basins of Indus, Ganges, Brahmaputra, and Meghna rivers in South Asia using observations from Ozone Monitoring Instrument (OMI) on-board Aura satellite during 2004–2015. For the first time this area, a highly populated and industrialized region with significant emissions of air pollutants, has been discussed collectively. OMI data reveal significantly elevated NO2 column over the region averaged at (1.9 ± 0.1) × 1015 molecules cm–2 (average ± standard deviation of observations) with an increase of 21.12% (slope (0.036 ± 0.004) × 1015 molecules cm–2, y-intercept (1.705 ± 0.024) × 1015 molecules cm–2, R2 = 0.92) during the study period. According to MACCity anthropogenic emissions inventory transportation, energy, residential, and industrial sectors are the major contributors of high NOx emissions. NO2 pollution hot spots are identified and their tendencies have been discussed. The hot spots of megacities Lahore (Pakistan) and Dhaka (Bangladesh) are found to be strengthening and expanding over the time. Eastern Ganges Basin shows the highest NO2 concentration at (2.63 ± 0.22) × 1015 molecules cm–2 and growth rate of 3.22% per year mainly linked to power generation, fossil fuel extraction, mining activities, and biomass burning. NO2 over Indus–Ganges–Brahmaputra–Meghna Basin exhibits seasonal maximum in winter and minimum in monsoon. The highest seasonality is found over Meghna Basin due to large variations in meteorological conditions and large-scale crop-residue burning. Some anomalies in NO2 levels have been detected linked to intense crop-residue burning events. During these anomalies, exceptionally high levels of daily NO2 reaching up to 76.23 × 1015 molecules cm–2 have been observed over some places in Indus and Meghna Basins.

Prevalence of Malassezia Pachydermatis in Dogs

In the present study the prevalence of Malassezia pachydermatis among the clinical cases of dogs was 28%. However, Malassezia sps was also associated in dogs with demodicosis (6.6%), pyoderma (4.4%) and dermatophytosis (2.2%). The breed wise prevalence of canine malasseziosis was highest in Labrador retriever (32 %) and least in Great dane, Dachshund and Pug (2 %). Similarly, a prevalence rate of 42% was recorded in dogs which were above 8 yrs and a least prevalence of 24% among the dogs aged between 1-4 yrs and whereas, the infection was more prevalent in males (58 %) when compared to females (42 %). Further, the seasonal prevalence was recorded to be highest in summer (52 %) and minimum in monsoon (20 %).

Diurnal variation of ducts observed over a tropical station, Gadanki, using high‐resolution GPS radiosonde observations

AbstractA comprehensive study on diurnal variation of ducting using high vertical and temporal resolution radiosonde measurements over the Indian tropical region, Gadanki (13.5°N, 79.2°E), was presented. The diurnal variation of ducts was examined statistically based on both the refractivity and modified refractivity using 3‐hourly radiosonde soundings obtained during October 2010 to March 2014 as a part of tropical tropopause dynamics (TTD) campaigns conducted under Climate and Weather of Sun Earth System (CAWSES) India Phase II program. Strong diurnal variation in the altitude of occurrence of the duct has been found and is at maximum altitude (~2.5 km) during 11–17 LT. Interestingly, it is found that the occurrence of duct altitude closely follows the boundary layer altitude. Diurnal variation of duct altitude is maximum during postmonsoon followed by winter, monsoon, and minimum in premonsoon. However, duct strength is maximum during winter followed by premonsoon, postmonsoon, and minimum in monsoon. Duct thickness is found to be varying between 0.4 km and 1 km diurnally with the highest thickness during the winter season. Strong diurnal and seasonal variation in the percentage occurrence of the ducts was found with the highest percentage of ducts observed during winter (77%) followed by postmonsoon (51%), premonsoon (44%), and monsoon (10%). All the characteristics of ducts during all the seasons are maximum at 14 LT due to the high solar irradiance over Gadanki from 11 to 17 LT. The minimum frequency being trapped has been investigated and found that wave trapping occurs for the radars with frequencies 56–438 MHz over this station.

Occurrence of heavy metals in fish: a study for impact assessment in industry prone aquatic environment around Kolkata in India

A study was conducted during November 2005-October 2006 for determining the heavy metal contamination in surface water and sediments and giving prime thrust to determine the heavy metal concentrations fish samples collected from various points of the river Ganga at different time interval. Fish samples (viz., Channa marulius and Aorichthys seengala) were analyzed for heavy metals using standard laboratory procedures by AAS method. In impact points the annual average values for Cu, Cr, Cd, Pb and Zn were 0.15, 0.04, 0.03, 0.02 and 0.29 ppm, respectively. The concentrations of heavy metals in the riverine water collected from middle point had the order Zn > Cu > Cr > Cd > Pb. The data indicated that copper was maximally accumulated in the riverine sediments whereas least annual average concentration was obtained for lead. The trend of accumulation suggested deposition was maximum for zinc and minimum for cadmium in the muscles of both fish species. Only zinc has shown some significant seasonal variation in relation to metal deposition in fish muscles (minimum in monsoon and maximum in summer). The heavy metal contamination to fish may be due to indiscriminate discharge of polluted and untreated sewage sludge to the river. The heavy metal contents in fish at some places are alarming.