Reassessing the availability of crop residue as a bioenergy resource in India: A field-survey based study.

Second-generation bioenergy, a carbon neutral or negative renewable resource, is crucial to achieving India's net-zero emission targets. Crop residues are being targeted as a bioenergy resource as they are otherwise burned on-field, leading to significant pollutant emissions. But estimating their bioenergy potential is problematic because of broad assumptions about their surplus fractions. Here, we use comprehensive surveys and multivariate regression models to estimate the bioenergy potential of surplus crop residues in India. These are with high sub-national and crop disaggregation that can facilitate the development of efficient supply chain mechanisms for its widespread usage. The estimated potential for 2019 of 1313 PJ can increase the present bioenergy installed capacity by 82% but is likely insufficient alone to meet India's bioenergy targets. The shortage of crop residue for bioenergy, combined with the sustainability concerns raised by previous studies, imply a need to reassess the strategy for the use of this resource.

Synthesis, Characterization, Properties, and Novel Applications of Fluorescent Nanodiamonds.

In the last few years, fluorescent nanodiamonds (FNDs)  have been developed significantly as a new member in the nanocarbon family. The surface of FNDs is embedded with some crystallographic defects containing color centres which surmount the properties of other fluorochromes including up conversion and down conversion nanoparticles, quantum dots, nano tubes, fullerenes, organic dyes, silica etc. Some of the intriguing properties like inevitable photostability, inherent bio-compatibility, outstanding optical and robust mechanical properties, excellent magnetic field, and electric field sensing potentiality make FNDs appealing to some benevolent applications in numerous fields like bio-imaging, delivering drugs, fighting cancer, spin electronics, imaging of magnetic structure at nanoscale and as promising nanometric temperature sensor. The structure of FNDs has certain point defects on the surface among which negatively charged nitrogen vacancy centre (NV-) is the most investigated color centre. The production of NV- fluorescence nanodiamonds is the most challenging task as substitution of carbon atoms is required to create vacancies by causing irradiation from an electron beam which is followed by high temperature annealing. Thus, this review points out the relative advantages of FNDs containing negatively charged nitrogen vacancy centres produced from HPHT method or CVD method with those nanodiamonds produced through detonation process or pulsed laser ablation (PLA) method. The steps involved in the fabrication of FNDs are described along with the major challenges and struggles underwent during the process in this review. This review also summarizes the recent developments made in the functionalization and applications predominantly made in the field of biological science and it is understood that depending on the defect color centres they can exhibit different emitted wavelengths ranging from UV-visible to near infrared with broad or narrow bandwidths. This review also highlights some of the fluorescent NDs that emit stable and strong red or green photoluminescence from the defect centers of NV- which are implanted in the crystal lattice. This critical and extensive review will be useful for the further progress in this futuristic field of FNDs.

Variabilities of δ13C and carbonaceous components in ambient PM2.5 in Northeast India: Insights into sources and atmospheric processes.

A year-long sampling campaign of ambient PM2.5 (particulate matter with aerodynamic diameter ≤2.5 mm) at a regional station in the North-Eastern Region (NER) of India was performed to understand the sources and formation of carbonaceous aerosols. Mass concentration, carbon fractions (organic and elemental carbon), and stable carbon isotope ratio (δ13C) of PM2.5 were measured and studied along with cluster analysis and Potential Source Contribution Function (PSCF) modelling. PM2.5 mass concentration was observed to be highest during winter and post-monsoon seasons when the meteorological conditions were relatively stable compared to other seasons. Organic carbon (OC) concentration was more than two times higher in the post-monsoon and winter seasons than in the pre-monsoon and monsoon seasons. Air mass back trajectory cluster analysis showed the dominance of local and regional air masses during winter and post-monsoon periods. In contrast, long-range transported air masses influenced the background site in pre-monsoon and monsoon. Air mass data and PSCF analysis indicated that aerosols during winter and post-monsoon are dominated by freshly generated emissions from local sources along with the influence from regional transport of polluted aerosols. On the contrary, the long-range transported air masses containing aged aerosols were dominant during pre-monsoon. No significant variability was observed in the range of δ13C values (-28.2‰ to -26.4‰) during the sampled seasons. The δ13C of aerosols indicates major sources to be combustion of biomass/biofuels (C3 plant origin), biogenic aerosols, and secondary aerosols. The δ13C variability and cluster/PSCF modelling suggest that aged aerosols (along with enhanced photo-oxidation derived secondary aerosols) influenced the final δ13C during the pre-monsoon. On the other hand, lower δ13C in winter and post-monsoon is attributed to the freshly emitted aerosols from biomass/biofuels.

Air quality and PM10-associated poly-aromatic hydrocarbons around the railway traffic area: statistical and air mass trajectory approaches.

Diesel engine railway traffic causes atmosphere pollution due to the exhaust emission which may be harmful to the passengers as well as workers. In this study, the air quality and PM10 concentrations were evaluated around a railway station in Northeast India where trains are operated with diesel engines. The gaseous pollutant (e.g. SO2, NO2, and NH3) was collected and measured by using ultraviolet-visible spectroscopy. The advanced level characterizations of the PM10 samples were carried out by using ion chromatography, Fourier-transform infrared, X-ray diffraction, inductively coupled plasma optical emission spectrometry , X-ray photoelectron spectroscopy, field-emission scanning electron microscopy with energy-dispersive spectroscopy, and high-resolution transmission electron microscopy with energy-dispersive spectroscopy techniques to know their possible environmental contaminants. High-performance liquid chromatography technique was used to determine the concentration of polycyclic aromatic hydrocarbons to estimate the possible atmospheric pollution level caused by the rail traffic in the enclosure. The average PM10 concentration was found to be 262.11 µg m-3 (maximum 24 hour) which indicates poor air quality (AQI category) around the rail traffic. The statistical and air mass trajectory analysis was also done to know their mutual correlation and source apportionment. This study will modify traditional studies where only models are used to simulate the origins.

Chemical Forms of Mercury in Pyrite: Implications for Predicting Mercury Releases in Acid Mine Drainage Settings.

Pyrite (cubic FeS2) is the most abundant metal sulfide in nature and also the main host mineral of toxic mercury (Hg). Release of mercury in acid mine drainage resulting from the oxidative dissolution of pyrite in coal and ore and rock resulting from mining, processing, waste management, reclamation, and large construction activities is an ongoing environmental challenge. The fate of mercury depends on its chemical forms at the point source, which in turn depends on how it occurs in pyrite. Here, we show that pyrite in coal, sedimentary rocks, and hydrothermal ore deposits can host varying structural forms of Hg which can be identified with high energy-resolution XANES (HR-XANES) spectroscopy. Nominally divalent Hg is incorporated at the Fe site in pyrite from coal and at a marcasite-type Fe site in pyrite from sedimentary rocks. Distinction of the two Hg bonding environments offers a mean to detect microscopic marcasite inclusions (orthorhombic FeS2) in bulk pyrite. In epigenetic pyrite from Carlin-type Au deposit, up to 55 ± 6 at. % of the total Hg occurs as metacinnabar nanoparticles (ß-HgSNP), with the remainder being substitutional at the Fe site. Pyritic mercury from Idrija-type Hg deposit (α-HgS ore) is partly divalent and substitutional and partly reduced into elemental form (liquid). Divalent mercury ions, mercury sulfide nanoparticles, and elemental mercury released by the oxidation of pyrite in acid mine drainage settings would have different environmental pathways. Our results could find important applications for designing control strategies of mercury released to land and water in mine-impacted watersheds.

Polycyclic aromatic hydrocarbons (PAHs) around tea processing industries using high-sulfur coals.

In the present investigation, the concentrations of polycyclic aromatic hydrocarbons (PAHs) associated with PM2.5, PM10 and dust particles emitted from two tea processing industrial units were studied that uses high-sulfur coal as their energy source. A total of 16 PAHs (viz. naphthalene (Nap), acenaphthene (Ace), acenaphthylene (Acen), phenanthrene (Phe), fluorene (Flu), anthracene (Ant), fluoranthene (Fluo), pyrene (Pyr), benz[a]anthracene (BaA), chrysene (Chry), benzo[b]fluoranthene (BbF), benzo[k]fluoranthene (BkF), benzo[a]pyrene (BaP), dibenz[a,h]anthracene (DBahA), indeno[1,2,3-cd]pyrene (IP) and benzo[ghi]perylene (BghiP) were measured. The total PAH concentration was found to be 94.7 ng/m3 (∑4 PAHs) in the PM10 particle, 32.5 (∑12 PAHs) in PM2.5 and 1.08 ng/m3 (∑6 PAHs) in the dust sample from site A. In site B, the sum of the PAHs in the PM2.5, PM10 and dust samples are found to be 154.4 ng/m3 (∑7 PAHs), 165 ng/m3 (∑3 PAHs) and 1.27 ng/m3 (∑6 PAHs), respectively. Hybrid Single Particle Lagrangian Integrated Trajectory model study revealed the contribution of local or long-range transport of aerosol sources. Along with the coal combustion activities in the study sites, other sources such as biomass burning and vehicular emission may contribute to the PAHs in the aerosol samples.

Preliminary report on therapeutic potential of coal-derived carbon quantum dots against SARS-CoV-2 virus.

Due to the pandemic of COVID-19 and subsequent emerging of new mutant strains, there has been a worldwide hunt for therapeutic and protective agents for its inhibition. In this short communication, for the first time, we report the coal-derived carbon quantum dot (CQD) for the possible therapeutic application against SARS-CoV-2. The synthesized C1-CQD is observed to be safe towards the normal cell line at highest dose, while effectively inhibiting growth of SARS-CoV2 (>95%) with IC50 value of 5.469 µg/mL. Moreover, C1-CQD showed activity against SARS-CoV-2 infection which is comparable to known inhibitory antiviral drug i.e., Remdesivir. These novel findings indicate that coal-based CQDs have highly potent anti-viral activity and could be investigated further for developing cheap and safer alternative therapeutic strategies for inhibition of SARS-CoV-2.

Chemical and toxicological studies on black crust formed over historical monuments as a probable health hazard.

Studies to date have mostly investigated environmental factors responsible for deterioration of historical monuments. Black crusts formed on historical monuments are considered as factor for deterioration of structures or as an indicator of environmental status of the surrounding area. Black crust formed on historical monuments has never been investigated as a health hazard. Herein, for the first time, we performed in vitro and in vivo toxicology studies of black crust formed on three culturally-rich historical monuments (Rang Ghar, Kareng Ghar, and Talatal Ghar) of the Indian subcontinent to test their toxicological effect. Black crust suspension in ultrapure water was found not to be considerably toxic to the cells upon direct short-term exposure. However, the sub-acute nasal exposure of the black crust suspension in Swiss albino mice produced lung-specific pathologies and mortality. Additionally, structural formation of the black crust along with the speciation of potentially hazardous elements (PHEs), polyaromatic hydrocarbon (PAHs), and other metals were investigated. Overall, these results indicate the potential of black crust deposited on historical monuments as health hazard owing to the atmospheric pollution of the surroundings. However, it may be noted that black crust and its components have very low possibility of health implication unless they are disturbed without proper care.

Solid-State Phosphors from Coal-Derived Carbon Quantum Dots.

With unique optical and chemical properties, carbon quantum dots (CQDs) find tremendous applications in chemistry, biology, and materials science to medicine. To expand the applicability of coal-derived CQDs from the liquid to solid state, we herein report the sustainable synthesis of solid phosphors from coal-derived CQDs using poly(vinyl alcohol) (PVA) and silica (SiO2) as an organic and inorganic matrix. Two coal-derived CQDs were obtained using an eco-friendly ultrasonic-assisted wet oxidation method. The structural and chemical properties of the CQDs were extensively investigated and compared with commercial CQDs. The coal-derived CQDs exhibited blue fluorescence with 8.9 and 14.9% quantum yields. The CQDs were found to be self-co-doped with nitrogen and sulfur heteroatoms through surface and edge functional groups. Solid-state fluorescence of PVA/CQD composite films confirmed that the CQDs retained their excellent blue emission in a dry solid matrix. A facile one-pot sol-gel method was employed to fabricate SiO2/CQD phosphors with the unique fluorescence emission. Due to their special structural features, coal-derived CQDs favored the heterogeneous nucleation and rapid formation of SiO2/CQD phosphors. Further, coal-derived CQDs caused high-intensity white light emission with CIE coordinates of (0.312, 0.339) by endowing a suitable band gap structure in a SiO2/CQD solid phosphor for potential optical applications.

Biocompatible Nanodiamonds Derived from Coal Washery Rejects: Antioxidant, Antiviral, and Phytotoxic Applications.

Coal washery rejects (CWRs) are a major byproduct produced in coal washery industries. We have chemically derived biocompatible nanodiamonds (NDs) from CWRs toward a wide range of biological applications. The average particle sizes of the derived blue-emitting NDs are found to be in the range of 2-3.5 nm. High-resolution transmission electron microscopy of the derived NDs depicts the crystalline structure with a d-spacing of 0.218 nm, which is attributed to the 100 lattice plane of a cubic diamond. The Fourier infrared spectroscopy, zeta potential, and X-ray photoelectron spectroscopy (XPS) data revealed that the NDs are substantially functionalized with oxygen-containing functional groups. Interestingly, the CWR-derived NDs exhibit strong antiviral properties (high inhibition of 99.3% with an IC50 value of 7.664 µg/mL) and moderate antioxidant activity that widen the possibility of biomedical applications. In addition, toxicological effects of NDs on the wheatgrass seed germination and seedling growth showed minimal inhibition (<9%) at the highest tested concentration of 300.0 µg/mL. The study also provides intriguing prospects of CWRs for the creation of novel antiviral therapies.

Combustion conditions and feed coals regulating the Fe- and Ti-containing nanoparticles in various coal fly ash.

Quantitative characteristics and sizes of nanoparticles (NPs) in coal fly ash (CFA) produced in coal-fired power plants as a function of coal type and plant design will help reveal the NP emission likelihood and their environmental implications. However, little is known about how combustion conditions and types of coal regulate the NP abundance in CFAs. In this study, based on single particle (SP)-ICP-MS technology, particle number concentrations (PNCs) and sizes of Fe- and Ti-containing NPs in CFAs were determined for samples collected from power plants of different designs and burning different types of coal. The PNCs of Fe- and Ti-containing NPs in all CFAs measured were in the range of 1.3 × 107 - 3.4 × 108 and 6.8 × 106 - 2.2 × 108 particles/mg, with the average particle sizes of 111 nm and 87 nm, respectively. The highest Fe-NP PNCs likely relate to the highest contents of Fe and pyrite in the feed coal. In addition, high TOC in CFAs are associated with metal-containing NPs, resulting in elevated abundances of these NPs with relatively large sizes. Moreover, elevated PNCs of NPs were found in CFAs produced by coal-fired power plants burning low-rank coals and with small installed capacity (especially those under 100-MW units). Compared to cyclone filters, ESPs and FFs with higher removal efficiency typically retain more Fe-/Ti- containing NPs with smaller sizes. Based on a structural equation (SE) model, raw coal properties (coal rank and Fe/Ti content), boiler types, and efficiency of particulate emission control devices likely indirectly affect PNCs of Fe- and Ti-containing NPs by influencing TOC contents and their corresponding metal concentrations of CFAs. This study provides the first analytic and comprehensive information concerning the direct and indirect regulating factors on NPs in various CFAs.

An overview on atmospheric carbonaceous particulate matter into carbon nanomaterials: A new approach for air pollution mitigation.

Air pollutants consisting of atmospheric particulate matter (PM) poses a major threat to the environment and human health. However, due to their carbonaceous nature, these atmospheric PM can also be used as a precursor for fabrication of high-valued carbon nanomaterials (CNMs) leading to waste to wealth as well as mitigation of air pollution. Over the few years, various results have been reported on different types of physical and chemical methods for the synthesis of CNMs from atmospheric particulate matter with the help of top down and bottom up methods; however, there is a lack of review on these innovative processes and outcome in order to assess their feasibility and suitability for further investigation. This review critically assesses the synthesis, identification, and characterization of different types of CNMs derived from the atmospheric PM. The fascinating fluorescence properties along with the novel multifarious applications of such PM-derived CNMs are also extensively discussed in this review work. This unique review will certainly help to make a new avenue for air pollution mitigation through conversion of PMs in to value added nanomaterials (VNMs) and will boost the research activity in the field of environmental nanotechnology for a cleaner environment.

Geochemistry and mineralogy of coal mine overburden (waste): A study towards their environmental implications.

Open-cast mining of coal generates waste material, including rock and soil with different minerals, and traditionally dumped as waste over the valuable lands worldwide. Overburden (OB) is devoid of actual soil characteristics, low micro and macronutrient content, and a sufficient amount of rare earth elements, silicate, sulphate, and clay minerals. This study aimed to determine the geochemistry and mineralogy of OB samples collected from Makum coalfield, Margherita of Northeast (NE) India. The geochemical and mineralogical analyses of overburden (OB) were carried out by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), High resolution-inductively coupled plasma mass spectrometer (HR-ICP-MS), Field-emission scanning electron microscopy (FE-SEM) techniques. This study shows potentially hazardous elements (PHEs), including Pb, Co Cu, Cr, Ni, and Zn, and their association with minerals observed in OB samples. The major oxides (SiO2, Al2O3, Fe2O3, MgO, CaO, K2O, and Na2O) are present in all the overburden samples analyzed by the X-ray fluorescence (XRF) technique. Various minerals such as quartz, kaolinite, gypsum, melanterite, rozenite, hematite, and pyrite were identified. The overburden samples contain considerable amounts of rare earth elements and yttrium (REY; as received basis) with an average of 26.3 (ppm). The presence of abundant minerals and REY opens up a new avenue for the gainful and sustainable utilization of such waste materials.

Atmospheric particulate matter and potentially hazardous compounds around residential/road side soil in an urban area.

Exposure to ambient coarse and fine particulate matter (PM10 and PM2.5) causes premature death worldwide due to the nature of their particle size. It contains potentially hazardous elements (PHEs) and polycyclic aromatic hydrocarbons (PAHs). This study aims to quantify the particulate matter (PM) loads on the surface of soil in twenty-five different locations including residential and roadside areas of an urban area in Northeast India. This study shows that the 24h mean concentration of PM (121 ± 49 µg/m3 for PM2.5 and 153 ± 45 µg/m3 for PM10) exceeded more than three times the WHO's air quality standard limit for both PM2.5 (25 µg/m3) and PM10 (50 µg/m3) indicating poor air quality in the urban area during monsoon season. The health risk assessment of PAHs and PHEs including mutagenic or carcinogenic potency was observed to be higher as compared to other studies carried out on road traffic emissions in a similar type of urban area. This study also provides a brief database on the deposition of PM on the soil surfaces due to wet-deposition that would help to increase public awareness in such type of urban area for the control of PM pollution and further remediation.

An environmental evaluation of carbonaceous aerosols in PM10 at micro- and nano-scale levels reveals the formation of carbon nanodots.

Carbonaceous aerosols play significant roles in air quality and the climate; their oxidation at the nano-scale level may possibly increase the reactivity and toxicity of atmospheric particulates. In the present study, a laboratory experiment on the atmospheric carbonaceous aerosol was done by using H2O2 as an oxidizing agent. An extensive study made with advanced analytical tools revealed the formation of photoluminescent carbon nanoparticles (carbon nanodots) in the carbonaceous aerosol. The carbon nanoparticles are mostly at the sp2 hybridization state and contain various surface functional groups such as carboxyl and carbonyl groups. The properties of these carbon nanoparticles resemble the engineered carbon nanoparticles such as carbon dots (CDs). The carbon nanoparticles, mainly less than 10 nm, are composed of carbon nanocrystals containing a few other elements such as Ca and Fe. Fluorescence spectroscopy revealed the characteristic excitation-dependent emission spectra of blue fluorescent carbon nanoparticles. The results indicate the presence of characteristic carbon nanoparticles in the carbonaceous aerosol in PM10, opening a new road for predicting environmental processes occurring in the atmospheric environment.

Atmospheric particulate matters in an Indian urban area: Health implications from potentially hazardous elements, cytotoxicity, and genotoxicity studies.

The nature of the atmospheric particulate matters (PMs) varies depending on their sizes and their origin from different activities in the background environment. These PMs are associated with potentially hazardous elements (PHEs) such as organic compounds (e.g. Polyaromatic Hydrocarbons) that can be harmful to health. The main objective of this work is the identification and investigation of the toxicological aspects of PHEs in PMs during pre-monsoon and post-monsoon season in an urban area of Northeast region (NER) of India. In the course of the study, the 24 -hs average concentrations of PMs were detected to be more than two-times higher than the Indian standard limit (NAAQ, category) which indicates poor air quality in both the seasons around the sampling sites. This study demonstrates that the concentrations of PM-bound PAHs are mutagenic and that the Excess Cancer Risks exceed the USEPA standard limits. PMs cause cytotoxicity and can also induce genotoxicity to human health analyzed by cell culture and gel electrophoresis. This study helps to promote research to evaluate the PMs bound PHEs toxicity in diverse human cell lines and also their relationship with climatic factors as well as quantitative source apportionment for mitigation purposes.

Blue-emitting fluorescent carbon quantum dots from waste biomass sources and their application in fluoride ion detection in water.

Carbon quantum dots (CQDs) are among the most feasible allotropes of carbon-based nanomaterials with unique characteristics of photoluminescence, bio-compatibility, and high stability. Herein, a green and eco-friendly approach has been propagated for the fabrication of CQDs from different biomass waste materials including sugarcane bagasse (SCB), garlic peels (GP), and taro peels (TP) by using ultrasonic-assisted wet-chemical-oxidation method. This top-down approach involves oxidation of the carbonized biomass wastes by H2O2. Another purpose of our work is to make a comparative study on the three CQDs produced from the three different biomass wastes. The properties of the fabricated CQDs were evaluated by using High Resolution-Transmission Electron Microscopy (HR-TEM), Fourier Transform-Infrared (FT-IR) spectroscopy, X-ray Diffraction (XRD), and X-ray Photoelectron spectroscopy (XPS), respectively. The CQDs showed the characteristic photo-physical behaviours as evident from the UV-visible and fluorescence (FL) spectroscopic analyses. The CQDs are found to be highly water soluble possessing strong blue-fluorescence under UV light with excellent quantum yield around 4-27%. The comparative study on the different physico-chemical properties of the three wastes biomass-derived CQDs are also discussed in the paper. The FL properties of CQDs derived from taro peels waste shows the best fluorescence quantum yield among the three and keeping in view of this, an on-off-on fluorescence nanoprobe was designed by using taro peels-derived CQDs (i.e. T-CQDs) and Eu3+ ion. The FL emission of T-CQDs was observed to be significantly quenched by Eu3+ leading to the formation of a CQDs-Eu3+ nanoprobe. The CQDs-Eu3+ nanoprobe was promisingly used for sensing of fluoride ions in water.

Acid mine drainage in an Indian high-sulfur coal mining area: Cytotoxicity assay and remediation study.

Opencast mining causes significant environmental concern due to acid mine drainage (AMD) caused by the oxidation of pyrites and other sulfur-bearing minerals. The present study intends to determine the seasonal variability of AMD in the affected area of the Ledo opencast mining, the cytotoxicity of the AMD, and the AMD remediation process. The physicochemical properties of the collected samples were analyzed by using laboratory-based methods and sophisticated instrumental tools. The cytotoxicity study of AMD water was performed by using different cell lines such as normal rat muscle and human carcinoma cells. The study demonstrates that the mine water samples have high conductivity (1.30-2.49 ms cm-1) with high total dissolved solids (1068-1339 ppm) which can change the ionic composition of water. The concentration level of trace elements are also found to be higher than the permissible limit during monsoon season. A simple laboratory-based remediation process of AMD has been carried out in the current study by using size segregated pulverized limestone and the process reveals the decrease in elemental concentrations of AMD water. This study will be useful to develop a remediation technique to minimize the concentration levels of hazardous elements and ions in the AMD water.

Biochar aided aromatic grass [Cymbopogon martini (Roxb.) Wats.] vegetation: A sustainable method for stabilization of highly acidic mine waste.

Dumping of acidic mine waste poses severe threats to the ecosystem due to high acidity, nutrient deficiency and mobility of toxic metals. The present study has been undertaken on phytoremediation by amending the acidic soil/mine waste with biochar (BC) and plantation of palmarosa (Cymbopogon martini (Roxb.) Wats. A greenhouse experiment in different combinations of biochar and acidic mine waste was conducted to assess the phytoremediation efficiency of palmarosa by BC amendments. Results indicate that the palmarosa tolerates multiple stresses effectively with a 54 % metal tolerance index (MTI) and capable of reducing acid production from the acidic mine waste alone. BC incorporation in the mine waste and soil treatments significantly enhanced the palmarosa biomass (1.11-3.3 times) and oil content by liming the acid, immobilization of metals and improving the soil quality. BC addition in highly acidic mine waste amplified the phytoremediation efficiency and mitigates abiotic oxidative stress on plants (MTI 84 % to >100 %). BC aided palmarosa plantation shifted the soil from high-risk assessment code (RAC) to low RAC for vegetation. Biochar amendments along with palmarosa plantation offer a sustainable technology for phytostabilization of highly acidic mine waste along with the production of industrially important essential oil.

6,6'-Diamino-1,1',3,3'-tetra-methyl-5,5'-(4-chloro-benzyl-idene)bis-[pyrimidine-2,4(1H,3H)-dione].

The title compound, C(19)H(21)ClN(6)O(4), is a 1:2 adduct of p-chloro-benzaldehyde and uracil. It crystallizes with two mol-ecules in the asymmetric unit. The two uracil units in the same mol-ecule are connected by a pair of strong N-H⋯O hydrogen bonds. The packing is stabilized by N-H⋯O, C-H⋯O and C-H⋯N inter-actions.