No abstract

Manufacturing and resource industries are the key drivers for economic growth with a huge environmental cost (e.g. discharge of industrial effluents and post-mining substrates). Pollutants from waste streams, either organic or inorganic (e.g. heavy metals), are prone to interact with their physical environment that not only affects the ecosystem health but also the livelihood of local communities. Unlike organic pollutants, heavy metals or trace metals (e.g. chromium, mercury) are non-biodegradable, bioaccumulate through food-web interactions and are likely to have a long-term impact on ecosystem health. Microorganisms provide varied ecosystem services including climate regulation, purification of groundwater, rehabilitation of contaminated sites by detoxifying pollutants. Recent studies have highlighted the potential of methanotrophs, a group of bacteria that can use methane as a sole carbon and energy source, to transform toxic metal (loids) such as chromium, mercury and selenium. In this review, we synthesise recent advances in the role of essential metals (e.g. copper) for methanotroph activity, uptake mechanisms alongside their potential to transform toxic heavy metal (loids). Case studies are presented on chromium, selenium and mercury pollution from the tanneries, coal burning and artisanal gold mining, respectively, which are particular problems in the developing economy that we propose may be suitable for remediation by methanotrophs.

Chromium from tannery waste dump site causes significant environmental pollution affecting surrounding flora and fauna. The primary aims of this study were to survey vegetation, investigate the degree of soil pollution occurring near tannery waste dump site and make a systematic evaluation of soil contamination based on the chromium levels found in plants and earthworms from the impacted areas. This paper presents the pollution load of toxic heavy metals, and especially chromium, in 10 soil samples and 12 species of plants. Soil samples were analysed for heavy metals by using ICP-MS/ICP-OES method. Results indicated that Cr in soils exceeded soil quality guideline limits (SQGL). The total chromium present in the above ground parts of plants ranged from 1.7 mg kg in Casuarina sp. to 1007 mg kg in Sonchus asper. The Cr bioaccumulation in Eisenia fetida from tannery waste soil ranged from 5 to 194 mg kg. The high enrichment factor of Cr in S. asper and bioaccumulation factor in earthworms indicate that there is a steady increase of toxic chromium risk in this area, which could be correlated with the past dumping activity. Emphasis needs to be put on control measures of pollution and remediation techniques in such areas to achieve an ecologically sustainable industrialisation.

Keeping the sources of pollution such as chromium (Cr) under a safe limit is a daunting challenge due to the negative impact of heavy metal bioaccumulation in vegetation and the concomitant human health exposure. We took a closer look at Sonchus asper by cultivating in the green house. It resulted in 80% germination when cultivated over nine different soils collected from the tannery dump site. The biochemical analytical techniques such as mass spectrometry indicated significant bioaccumulation of Cr in the plant tissue. As per the ICP-MS analysis, this annual herb resulted in the accumulation of 601 mg kg of total Cr with 212 mg kg in its shoot from soil samples containing up to 41 mg kg of hexavalent Cr. The energy dispersive X-ray (EDX) spectroscopy of S. asper revealed a higher level of S element indicating a sulfate-Cr binding relation. Elevated content of Cr in soil (73,721 ± 65 mg kg) caused biochemical changes in the shoot of S. asper as indicated by the disappearance of Fourier transform infrared spectroscopy (FTIR) bands at 935 and 872 cm and further revealing aliphatic -CH appearing as anti-symmetry ν(CH) and symmetric vibration ν(CH) at the band of 2920 and 2850 cm, respectively.

A pot culture study was conducted at Horticultural Research Station, Ooty to assess the effect of ground level ozone on physiology in garlic plant and to find out the suitable remedial measures against ground level ozone. The potted soil was found to be acidic in nature with very low salt concentration, very high in organic carbon, medium in nitrogen, phosphorus and high in potassium. Elevated ozone levels (150ppb and 200ppb) had significantly reduced the garlic plant chlorophyll content, stomatal conductance, photosynthetic rate, pungency and total soluble solids. The highest chlorophyll content (33.97µmolm-2) was observed under ambient ozone level (T1) and the lowest chlorophyll content (12.68µmolm-2) was observed in elevated ozone exposure at 200 ppb (T3), the highest stomatal conductance (0.45mmol m-2s-1) was recorded in Ambient Ozone level + foliar spray 3% Panchagavya (T4), and the lowest stomatal conductance (0.11mmol m-2s-1) was observed in elevated ozone exposure at 200 ppb (T3). Since, the elevated ozone had significant reduction in photosynthetic rate in garlic, the lowest was observed (0.82µmol CO2 s-1m-2) in T3- Elevated ozone exposure at 200 ppb and the highest photosynthetic rate (3.02µmol CO2 s-1m-2) was observed in treatment T4- Ambient Ozone level + foliar spray 3% Panchagavya after a week. When coming to quality of garlic bulbs, the highest pungency content was found in Ambient Ozone level + foliar spray 0.1% Ascorbic acid and the lowest was observed in Elevated ozone exposure at 200 ppb (T3) furthermore, in observing the garlic quality where total soluble solids (TSS) showed that the treatment Ambient Ozone level + foliar spray 3% Panchagavya (40.00°Brix) as highest and the treatment Elevated ozone exposure at 200 ppb (T3) recorded the lowest. Thus the tropospheric ozone has detrimental impact on physiological responses, which will reduce crop growth and yield. The ozone protectants helped in scavenging the O3 from apoplast of the crops and among the ozone protectants, neem oil acted as a good ozone scavenger followed by ascorbic acid and panchagavya to improve the physiological response of garlic plant under elevated tropospheric ozone levels.