Greenhouse gas emissions from hydroelectric reservoirs: mechanistic understanding of influencing factors and future prospect.

Rising need for various renewable and non-renewable energy resources became vital for developing countries to meet their rapid economic growth under an exponentially growing population scenario. The primary goal of COP-26 for climate change mitigation is to reduce greenhouse gas (GHG) emissions from different sectors. Because of their significant contribution to global warming, GHG emissions from hydroelectric reservoirs have been a contentious topic of discussion since the pre-industrial age. However, the exact methodology for quantification of GHG and important parameters affecting emission rate is difficult due to limited equipment facilities, techniques for GHG measurement, uncertainties in GHG emissions rate, insufficient GHG database, and significant spatio-temporal variability of emission in the global reservoirs. This paper discusses the current scenario of GHG emissions from renewable energy, with a focus on hydroelectric reservoirs, methodological know-how, the interrelationship between parameters impacting GHG emissions, and mitigation techniques. Aside from that, significant methods and approaches for predicting GHG emissions from hydroelectric reservoirs, accounting for GHG emissions, life cycle assessment, uncertainty sources, and knowledge gaps, have been thoroughly discussed.

Nickel in terrestrial biota: Comprehensive review on contamination, toxicity, tolerance and its remediation approaches.

Nickel (Ni) has been a subject of interest for environmental, physiological, biological scientists due to its dual effect (toxicity and essentiality) in terrestrial biota. In general, the safer limit of Ni is 1.5 µg g-1 in plants and 75-150 µg g-1 in soil. Litreature review indicates that Ni concentrations have been estimated up to 26 g kg-1 in terrestrial, and 0.2 mg L-1 in aquatic resources. In case of vegetables and fruits, mean Ni content has been reported in the range of 0.08-0.26 and 0.03-0.16 mg kg-1. Considering, Ni toxicity and its potential health hazards, there is an urgent need to find out the suitable remedial approaches. Plant vascular (>80%) and cortical (<20%) tissues are the major sequestration site (cation exchange) of absorbed Ni. Deciphering molecular mechanisms in transgenic plants have immense potential for enhancing Ni phytoremediation and microbial remediation efficiency. Further, it has been suggested that integrated bioremediation approaches have a potential futuristic path for Ni decontamination in natural resources. This systematic review provides insight on Ni effects on terrestrial biota including human and further explores its transportation, bioaccumulation through food chain contamination, human health hazards, and possible Ni remediation approaches.

Lead Toxicity: Health Hazards, Influence on Food Chain, and Sustainable Remediation Approaches.

Lead (Pb) toxicity has been a subject of interest for environmental scientists due to its toxic effect on plants, animals, and humans. An increase in several Pb related industrial activities and use of Pb containing products such as agrochemicals, oil and paint, mining, etc. can lead to Pb contamination in the environment and thereby, can enter the food chain. Being one of the most toxic heavy metals, Pb ingestion via the food chain has proven to be a potential health hazard for plants and humans. The current review aims to summarize the research updates on Pb toxicity and its effects on plants, soil, and human health. Relevant literature from the past 20 years encompassing comprehensive details on Pb toxicity has been considered with key issues such as i) Pb bioavailability in soil, ii) Pb biomagnification, and iii) Pb- remediation, which has been addressed in detail through physical, chemical, and biological lenses. In the review, among different Pb-remediation approaches, we have highlighted certain advanced approaches such as microbial assisted phytoremediation which could possibly minimize the Pb load from the resources in a sustainable manner and would be a viable option to ensure a safe food production system.

High temperature stress during flowering and grain filling offsets beneficial impact of elevated CO2 on assimilate partitioning and sink-strength in rice.

Elevated [CO2] (e[CO2]) environments have been predicted to improve rice yields under future climate. However, a concomitant rise in temperature could negate e[CO2] impact on plants, presenting a serious challenge for crop improvement. High temperature (HT) stress tolerant NL-44 and high yielding basmati Pusa 1121 rice cultivars, were exposed to e[CO2] (from panicle initiation to maturity) and a combination of e[CO2] + HT (from heading to maturity) using field based open top chambers. Elevated [CO2] significantly increased photosynthesis, seed-set, panicle weight and grain weight across both cultivars, more prominently with Pusa 1121. Conversely, e[CO2] + HT during flowering and early grain filling significantly reduced seed-set and 1000 grain weight, respectively. Averaged across both the cultivars, grain yield was reduced by 18 to 29%. Despite highly positive response with e[CO2], Pusa 1121 exposure to e[CO2] + HT led to significant reduction in seed-set and sink starch metabolism enzymatic activity. Interestingly, NL-44 maintained higher seed-set and resilience with starch metabolism enzymes under e[CO2] + HT exposure. Developing rice cultivars with higher [CO2] responsiveness incorporated with increased tolerance to high temperatures during flowering and grain filling using donors such as NL-44, will minimize the negative impact of heat stress and increase global food productivity, benefiting from [CO2] rich environments.