Water and air quality
For the first time, modern humans lifted the weight of nurturing nature by doing nothing but only keeping themselves off the street and locked inside home to get rid of COVID-19 infection. Many cities had been experiencing heavy pollution during pre-COVID-19 timings and water bodies near industries and cities were found to be the main hub for pollution. It simply indicates that the industrial and anthropogenic pollutants were not treated before draining into water bodies. Instances of loose environmental audit and environmental clearances to industries also have been reported to contribute unprecedented damage to ecosystems 33,34. As a result, pollution accumulates in rivers and riverine systems26. Keeping in mind the intensity of pollution, sampling was done in the study site to indicate effects of industrial effluents in the study site (Fig. 1a).
The observed higher water pollution in the study site (Fig. 1b, c, d) could be a sensible factor, perhaps for which the river lacked the fish A. panchax when it was searched for experiments during 2018-201925. Although some of the studied parameters, especially the levels of heavy metals, were under control during the pre-COVID lockdown times, it probably was enough to disallow the above fish to grow in the study site. The pollution could also be the reason why large scale die-off events have been noticed along the rivers and riverine systems in India including Bay of Bengal and Mahanadi River during pre-COVID-19 timings26. Two months of full and stringent lockdown in the study area was resulted in the clear water and associated ecological improvements in industrial canals discharging water into the river (Fig. 1b-k). Clear base of the canal (Fig. 1e), schooling of fish (Fig. f and g), shrinking of the canals discharging polluted water with growth wild plants (indicating increase in biodiversity, Fig. 1h, i and j), and clear water (Fig. 1k) in the mouth of the discharging canals are few of the outcomes of the lockdown. Probably, our study is the first report with planned experimental analyses of environmental parameters at pre and post-COVID-19 time points indicating the appearance of a species in a niche under COVID-19 lockdowns (video 1).
We found that the dissolved oxygen level was increased during lockdowns by 15, 40 and 26% in US, DS and MB, respectively, than pre-lockdown times (Fig. 2a). Similarly, water temperature was also reduced by 4 (in US), 9 (in DS) and 8% in MB regions (Fig. 2b). pH of US and DS area was increased by 12 and 7%, respectively (p < 0.003, Fig. 2c). Water conductivity was drastically reduced by 47 (in both US and DS) and 44% in MB area (Fig. 2d). It could be due to loss of total dissolved solutes by 18 (in US), 15 (in AS) and 11% (in MB) regions during lockdown than pre-lockdown time (Fig. 2e). The changes are drastic and could be exemplary enough to accept that lockdowns had paramount effects on increasing the water of Mahanadi River and as observed in other rivers of India such as Yamuna River of New Delhi27. This is possibly due to zero effluent discharge into the river as cleanness of its water was observed (Fig. 1b-j). Perhaps this is the reason why the fish A. panchax count during lockdowns was noticed being an average of 12, 8 and 16 numbers per 100 × 2 m2 area (Fig. 2f) after the lockdowns are implemented. Similar results without experimental analyses of the environmental quality were reported. For example, the suspended particulate matter in surface water was reduced by 15.9% in the Vembanad lake, the longest one in India22.
We found that air quality of the study area was also improved drastically (Fig. 2g). Data indicates that overall air quality parameters such as levels of NO2, SO2, NH3, PM2.5 and CO were drastically reduced (p ≤ 0.001). The levels of NO2, SO2, NH3, PM2.5, PM10 and CO were reduced (p < 0.001) by 58.75, 80.33, 72.22, 76.28, 77.33 and 80.15%, respectively in post 2 months lockdowns than pre-COVID-19 study time whereas, O3 level was increased (p < 0.01) in the air (Fig. 2g). Similar results have been noticed in many cities across the world 1,5,7. More particularly, reduction in 60% PM10, 39% PM2.5, 52.68% NO2, 30.35% CO and improvement ≥ 31% air quality index in New Delhi, India, in March 2020 than April 2020 under COVID-19 induced lockdowns 3. In China, overall environmental pollution level was found to be reduced by 30% in 2020 than 2019 due to 90% reduction in human mobility 4. Air temperature was also found to be low (r = 0.392; p < .01) during the above timings at Jakarta, Indonesia that had induced positive effects on climate21. In some places in India, the temperature was also found to be reduced from 3 to 5 °C and noise pollution from 85dBA to < 65dBA23. The most advanced countries such as the USA, Italy and Germany were also found to experience the historical reduction in NO2 level by 25.5% under the lockdowns 14. It is noteworthy to mention that PM2.5 and NO2 emissions have an intricate relation with COVID-19 in humans19.
As a result Few of such examples are elephant strolling through roads, deer on street of Japan, whales in Indonesia sea water, peacocks in human habitats at Delhi India, spotting coyotes (that normally timid of traffic) on the Golden Gate Bridge in San Francisco, USA, grazing deer few miles from the White House near Washington homes, wild boars in Barcelona and Bergamo, Italy, wild puma in Santiago, the capital of Chile, peacocks have strutted through Bangor and goats through Llandudno and sheep in Wales, and the most convincingly, crabs and fish in Venice canal of Italy are noticed after lockdowns 17,28. However, the invasion of species due to the reduction of environmental pollution or due to reduction of human dominancy is still not clear.
Heavy metal distribution
We have noticed that heavy metal (except Fe) concentration was reduced by ≥ 50% in the water at all the stations (Table 1). Particularly, Cu content was reduced by 58, 59 and 65% at US, DS and MB areas, respectively. Similarly, Ni content was reduced by 91, 92 and 59% (US, DS and MB, respectively) in the studied area. The level of Cd was undetectable in lockdown time and similar data was found for Pd in US and DS area, but it was reduced to 93% in the MB area. Notably, Zn content in the water was also reduced by 98% (in US), 90% (in DS) and 86% (in MB) in the studied area (Table 1) in lockdown period than pre-lockdowns timings. The physico-chemical characteristics and concentrations of various heavy metals in the water samples collected from the three study sites were shown in Table 1. Data on effects of lockdowns on heavy metal content in water bodies are scanty. Although, the change in heavy metal contents in water bodies as a function of lockdowns are scanty, similar results of the reduction of Cr, Fe, Cu, Zn, Cd, Pb, As, and Se were noticed in coastal industrial city of Tuticorin, South India 29.
Table 1
Heavy metal distribution before and after COVID-19 lockdowns in Mahanadi industrial river basin at Cuttack, India.
Metal
|
Time
|
Up-stream
|
Down stream
|
Mid-basin
|
WHO*
|
ICMR**
|
BSI#
|
Fe
|
BL
|
0.13 ± 0.001c
|
0.15 ± 0.002c
|
0.56 ± 0.005a
|
1
|
1
|
1
|
|
AL
|
0.073 ± 0.00e
|
0.083 ± 0.000d
|
0.30 ± 0.002b
|
1
|
1
|
1
|
Cu
|
BL
|
0.76 ± 0.02b
|
0.78 ± 0.061b
|
0.89 ± 0.043a
|
2
|
1.5
|
1.5
|
|
AL
|
0.32 ± 0.01c
|
0.31 ± 0.01c
|
0.31 ± 0.01c
|
2
|
1.5
|
1.5
|
Ni
|
BL
|
0.011 ± 0.000 b
|
0.013 ± 0.002a
|
0.015 ± 0.001a
|
0.02
|
BDL
|
BDL
|
|
AL
|
0.001 ± 0.000d
|
0.001 ± 0.002d
|
0.008 ± 0.001c
|
0.02
|
BDL
|
BDL
|
Cd
|
BL
|
0.0007 ± 0.000b
|
0.0009 ± 0.000a
|
0.0010 ± 0.000a
|
0.003
|
0.001
|
0.01
|
|
AL
|
BDL
|
BDL
|
BDL
|
0.003
|
0.001
|
0.01
|
Pb
|
BL
|
0.004 ± 0.000c
|
0.009 ± 0.000a
|
0.009 ± 0.001a
|
0.01
|
0.1
|
0.05
|
|
AL
|
BDL
|
BDL
|
0.0006 ± 0.000b
|
0.01
|
0.1
|
0.05
|
Zn
|
BL
|
0.07 ± 0.001b
|
0.07 ± 0.002b
|
0.14 ± 0.020a
|
5
|
15
|
15
|
|
AL
|
0.001 ± 0.000d
|
0.001 ± 0.000d
|
0.02 ± 0.000c
|
5
|
15
|
15
|
Data are represented for three consecutive day readings in up, down and mid-stream of the Mahanadi industrial belt at Cuttack. Before lockdown (BL, pre-COVID-19 time) and after lockdown (AL, during COVID-19 timing) sampling time difference was about 60 days. MANOVA was employed to know the significant difference among the mean values within a set (as on 23.05.2020) and before COVID-19 period. Mean values are considered as significantly different (assigned with different superscript) from each other at p ≤ 0.04 level. *-limit of heavy metals set by the World Health Organisation, **-limit of heavy metals set by the Indian Council of Medical Research, New Delhi, India, #limit of heavy metals set by the British Standards Institution. |
Overall results and appearance of A. panchax in the study site.
DFA analyses have confirmed that all parameters taken together or in groups such as the studied environmental parameters or heavy metals have yielded all studied groups into six (before and after lockdown at three sites, Fig. 3). Therefore, all parameters were subjected to change as a function of COVID-19 induced lockdowns. Almost all parameters had a very high standardized coefficient for canonical variables via root 1 to root 4 (Table 2, supplementary Table S1 and S2). Therefore, since an overall improvement of the environmental parameters was noticed, the sub-verity fish A. panchax (grow up to 2 cm) appeared in the river (Fig. 1g, 2f, Fig. 4, video 1). It is because; this fish prefers clear water in areas with dense growth of rooted or floating macrophytes 30.
Table 2
Standardized coefficient for canonical variables of environmental parameters and heavy metals as a function of COVID-19 timings and site of water stream in relation to the industrial belt in Mahanadi River.
Parameters
|
Root 1
|
Root 2
|
Root 3
|
Root 4
|
Root 5
|
DO
|
-0.2
|
0.442
|
0.889
|
-1.2205
|
1.89164
|
Temp
|
-0.4
|
0.318
|
-1.385
|
-0.3416
|
1.16639
|
pH
|
-4.0
|
0.717
|
-0.995
|
-0.2967
|
-0.63521
|
Conductivity
|
-0.9
|
2.049
|
0.915
|
-0.5242
|
-0.80021
|
TDS
|
-1.3
|
0.260
|
0.375
|
-0.2428
|
-0.51262
|
Fe
|
7.0
|
-0.592
|
-0.713
|
-0.6565
|
-0.46642
|
Cu
|
1.1
|
-0.851
|
-1.731
|
0.3770
|
2.78746
|
Ni
|
5.5
|
-0.288
|
0.309
|
0.6369
|
-2.22165
|
Cd
|
-3.7
|
0.479
|
0.071
|
0.4343
|
0.39227
|
Pb
|
1.4
|
-0.119
|
-0.893
|
-0.4383
|
0.68407
|
Zn
|
-0.8
|
-0.156
|
0.984
|
0.1687
|
-2.00592
|
EV
|
150933.3
|
8475.336
|
3034.573
|
172.6590
|
81.64398
|
CP
|
0.9
|
0.980
|
0.998
|
0.9995
|
1.00000
|
Environmental parameters and heavy metals as a function of COVID-19 timings (pre and during COVID-19 timings) and site (up, mid and downstream of Mahanadi River industrial belts near Jagatpur, Cuttack are included in the DFA analyses. The bold data indicate their significant contribution in segregating the groups distinctly as a function of the variable. DO-dissolved oxygen, Temp-temperature, TDS-total dissolved solid, EV-Eigen value, CP-cumulative proportion. |
The fish A. panchax can survive till the last few mL of water left in ditches for which it is employed to identify palaeo drainage basins for climatic and geological oscillations, biodiversity and evolutionary distribution of biota 31,32. This fish is susceptible to water pollution, as they were not available in the above basin on Mahanadi during pre-COVID-19 timings25. It clearly indicates that the Mahanadi River at the studied basins remains polluted although some of the toxic heavy metals are found to be under standard level24 (Table 1). The growth period of this fish to reach adulthood is around 2 months 31,32. Hence, healthy fish could be migrated to this area from the non-polluted sites and/or the fish could reproduce and fingerlings would have been grown to reach adulthood.
Environmentalists have been advocating that the self-regenerated nature will be degenerated quickly in post-COVID-19 timings because of the massive re-opening of the industries and vehicular exhaustion5. The industries will try to cover up the loss they did bear during the COVID-outbreak in post-COVID-19 time periods 36, 37, 38, 39. Mahanadi River system is the 3rd largest in the peninsula of India and serves as the source of domestic water supply to many cities including Sambalpur (0.2 million population), Cuttack (0.5 million population) and Paradeep (a major port of the country and 0.15 million population) besides many officially undocumented number of rural and minor urban settlements. However, its basin near Choudwar-Jagatpur industrial belt harbours mainly steel, ferro alloys, charge chrome, textile, polythene, plastic and paper and pharmaceutical industries. Use of water from the river and flush their effluents containing many pollutants in turn are the main source of pollution in Mahanadi River24. Therefore, stringent environmental audits need to be employed to maintain the revived nature in post-lockdown periods 1, 33, 34. In India, the environmental clearance from the governing body i.e. the Central Pollution Control Board states that the applications received and approval given for industrial activities are highly stringent and none of the industries violates them (Supplementary Fig. S1). If it is true in India, and in other countries, then the environment would not be polluted, remains as the unsolved question for a long time.
Stringent environmental audit to implement pollution clearance and “strict environmental safety and precautions” must be the need of the post-COVID-19 society to enjoy natural, sparkling water bodies, unpolluted water to drink and clear air to breathe. In India, the environmental clearance from the regulatory body i.e. the Central Pollution Control Board states that the applications received and approval given for industrial activities are highly stringent and none of the industries violates them. Then the pollution is from only vehicular operation must be debatable. But reduction in prevailing pollution from pre-lockdown to post lockdown strongly suggests that local, institutional, national and international bodies must join hands to implement strict audit system for industries. Probably in few counties such as India, implementation of such stringent rules has been started after the mishap occurred with a massive leak of styrene gas at an LG Polymer plant in Visakhapatnam early on Thursday (7th May 2020) which had killed 11 people and affected around 1,100 people along with many environmental crises. The Central Pollution Control Board of India, has directed all industries and state pollution control boards for a “good operable conditions” that include monitoring the deployment of pollution control equipments and effluent treatment plants, including safety equipment and machineries, and connectivity of sewers should be kept in before resuming operations at post-lockdown time. The board also issued a set of instructions to all pollution control boards and centres to ensure all units undertake a “proper safety and hazard audit” before they start operations after the lockdowns that is going to be ended on 31st May 202040. Similar steps by all nations need to be taken on urgent basis. Interference of international bodies in such environmental intervention programme must be highly solicited. Therefore, the world must put forth steps for the long terms maintenance of the self-regenerated environment in post COVID-19 timings before nature bounce back to experience the pre-COVID-19 time pollution1.