Safdar Bashir

Phosphate-assisted phytoremediation of arsenic by Brassica napus and Brassica juncea: Morphological and physiological response

ABSTRACT In this study, we examined the potential role of phosphate (P; 0, 50, 100 mg kg−1) on growth, gas exchange attributes, and photosynthetic pigments of Brassica napus and Brassica juncea under arsenic (As) stress (0, 25, 50, 75 mg kg−1) in a pot experiment. Results revealed that phosphate supplementation (P100) to As-stressed plants significantly increased shoot As concentration, dry biomass yield, and As uptake, in addition to the improved morphological and gas exchange attributes and photosynthetic pigments over P0. However, phosphate-assisted increase in As uptake was substantially (up to two times) greater for B. napus, notably due to higher shoot As concentration and dry biomass yield, compared to B. juncea at the P100 level. While phosphate addition in soil (P100) led to enhanced shoot As concentration in B. juncea, it reduced shoot dry biomass, primarily after 50 and 75 mg kg−1 As treatments. The translocation factor and bioconcentration factor values of B. napus were higher than B. juncea for all As levels in the presence of phosphate. This study demonstrates that phosphate supplementation has a potential to improve As phytoextraction efficiency, predominantly for B. napus, by minimizing As-induced damage to plant growth, as well as by improving the physiological and photosynthetic attributes.

Phytoremediation of Arsenic-Contaminated Soils Using Arsenic Hyperaccumulating Ferns

Arsenic contamination of soils is a global environmental, agricultural, and health issue given to the toxic and carcinogenic nature of As. Several anthropogenic activities, such as mining and smelting, coal combustion, wood preservation, leather tanning operations, and use of As-based pesticides in agriculture, have led to elevated concentrations of As in soil. Therefore, remediation and restoration of As-contaminated soils is imperative for providing safe food and healthy soils. In contrast to conventional (physicochemical) remediation methods, phytoremediation of As-contaminated soils using As-hyperaccumulating fern species has emerged as an eco-friendly, cost-effective, and efficient technology. Since the discovery of As-hyperaccumulator, Pteris vittata L., several other As-hyperaccumulating fern species have been identified in Pteris and Pityrogramma genera which demonstrated the ability to remove As from soil. This review will briefly discuss about the As dynamics and availability in soil; elucidate the mechanisms involved in As tolerance and (hyper)accumulation by ferns/plants for improving the phytoremediation efficiency; evaluate the capacity of As-hyperaccumulating fern species (e.g., P. vittata, Pityrogramma calomelanos) for phytoremediation of As-contaminated soils under pot and field conditions; and discuss how phosphate amendments, microbes, and agronomic practices can increase phytoremediation efficiency of the ferns.

Removal and recovery of metals by biosorbents and biochars derived from biowastes

The production of biosorbents and biochars from various biowastes (such as the agricultural and food industries and algal and fungal biomass) has received considerable attention because of their potential use in the removal and recovery of elements, such as precious metals and heavy metals from water and wastewater. Recovery of these metals from their aqueous solutions has emerged as an exciting area of research as a result of increasing or fluctuating prices of metals (eg, precious metals), limited availability of their deposits, and the ever-increasing demand and time- and energy-consuming processes needed to mine metal deposits. This review will summarize the various sources of metals, the available biowastes of the agricultural and food industries, and preparation methods for biosorbents and biochars from biowastes. We will focus on metal and heavy metal removal and recovery from waste and wastewater, methods for metal recovery, pretreatment and modification of biosorbents and biochars for enhanced metal sequestration, and strategies to provide stability to biosorbents and biochars to maximize resource recovery.

Cadmium toxicity and soil biological index under potato (Solanum tuberosum L.) cultivation

Increasing cadmium (Cd) pollution in soil is of great concern. A pot experiment was conducted with the aim of assessing the effect of Cd on soil biological indices under potato cultivation. Cadmium was added to 10 kg soil in each pot (6 seeds pot–1) as Cd(NO3)2 at 0, 15, 30, 45 and 60 mg kg–1 with three replications. All soil and plant parameters decreased with all Cd treatments; however, high levels of Cd had a significant (P < 0.05) suppressive effect. The highest Cd level significantly (P < 0.05) decreased microbial biomass carbon (2.16-fold), nitrogen (11.37-fold) and phosphorus (10.3-fold), as well as enzyme activities of dehydrogenase (4.36-fold), phosphatase (9.23-fold), and urease (9.61-fold). The highest Cd level also decreased pH (1.46-fold), potato shoot (3.55-fold) and root (7.43-fold) length, root (10.9-fold) and shoot (6.04-fold) fresh weight, root (7.51-fold) and shoot (13.7-fold) dry weight, chlorophyll content (27.0-fold), carotenoid content (4.08-fold), and plant macronutrient and micronutrient uptake in potato root and shoots. Conversely, the highest level of Cd significantly (P < 0.05) increased the biomass C : N (5.27-fold) and C : P (4.77-fold) ratios, soil extractable Cd (5.38-fold), and Cd uptake in potato root (5.05-fold) and shoot (4.82-fold) at the end of the experiment (day 60). Cadmium contamination substantially affected soil biological indices and growth of potato, and the Cd threshold was strongly associated with the extent of Cd concentration and duration to accumulate. Soil microbial biomass, enzymatic activities, pH and potato physiological parameters could be used as a sensitive indicators to reflect environmental stresses in soil ecosystems.

Arsenic removal by natural and chemically modified water melon rind in aqueous solutions and groundwater

Contamination of groundwater with toxic arsenic (As) has become an emerging health and environmental problem around the world, which has seen significant attention amongst the scientists for development of new sorbents to remediate As-contaminated water. Here, we explored the arsenate (As(V)) and arsenite (As(III)) sorption to natural water melon rind (WMR), xanthated WMR and citric acid-modified WMR in aqueous solutions, and determined potential of the most potent sorbent for As removal in groundwater. Xanthated WMR (X-WMR) showed relatively higher As(V) and As(III) removal than the citric acid modified WMR (CA-WMR) and natural WMR. The maximum As(III) (99%) and As(V) (98%) removal was obtained at pH 8.2 and 4.6, respectively, by X-WMR at 4 mg L-1 initial As(V) and As(III) concentrations and sorbent dose of 1 g L-1. Langmuir isotherm model best fitted (R2 of up to 0.96) the data both for As(III) and As(V) sorption to X-WMR. Sorption kinetics of As(V) and As(III) was well described (R2 of up to 0.99) by the pseudo second-order model on surface of the X-WMR. Thermodynamic investigations revealed that As(V) and As(III) sorption was endothermic and spontaneous. The FTIR spectroscopy depicted the presence of different surface function groups (OH, COOH, S-bearing (C=S, S=O and S-S)) which were involved in As(V) and As(III) sequestration on the sorbents examined here. Significantly, X-WMR showed (up to 49%) greater As(III) and As(V) sorption than that of natural WMR. Our results demonstrated that X-WMR efficiently removed 94%-100% (n = 16) of As from As-contaminated drinking well water which possessed detectable concentrations of some anions (e.g., SO4, CO3, HCO3). This study highlights that the X-WMR has potential to remove As, notably As(III), from solutions and drinking water, and might be utilized as a reactive medium for the treatment of As-contaminated water.

Current Approaches for the Assessment of In Situ Remediation of Xenobiotics

Industrial development during the last century has resulted in the spread of chemicals which were initially friends to human beings and revolutionized the human development. But due to their widespread use and application, they became foe for human beings. There are million tons of xenobiotics present in the world which are causing direct effects on human health. Application of chemicals to get rid of these xenobiotics will make them worst and is also not an economical approach. In situ remediation or natural attenuation is the only sustainable option to remediate widespread contaminated sites. It is also important to assess if these remediation/natural attenuation processes can replace conventional xenobiotic removal methods and are able to remove substantial amount of xenobiotics efficiently. Development of efficient techniques, which help us not only to estimate in situ remediation of xenobiotics but also their complete characterization, is therefore the need of the time. There has been a lot of work done in the development of tools to assess and characterize in situ remediation of xenobiotics. Different approaches are currently being applied to monitor natural attenuation or in situ remediation which include concentration monitoring, geohydrochemical investigation, molecular and microbiological characterization, application of tracer technology, analysis of metabolites, compound-specific stable isotope analysis, enantiomer fraction analysis and in situ microcosm to assess in situ remediation of xenobiotics. In this chapter, a brief introduction and evaluation of techniques to assess in situ remediation and their applicable boundaries have been discussed. In the end, application of integrated approaches to monitor in situ remediation of xenobiotics is stated.

Injustices of foreign investment in coal

After remaining flat from 2014 to 2016, global greenhouse gas emissions in 2017 increased to a record high ([ 1 ][1]). One contributing factor is foreign investments in coal. Many countries are working to reduce their carbon footprints within their borders, but adding to emissions by investing in

Better management of groundwater needed in Pakistan

Conservation triage, the prioritization of conservation efforts by explicit economic accounting, may not be used to determine listing decisions under the US Endangered Species Act of 1973. This could change with the proposed US H.R.717 Listing Reform Act that has been submitted to Congress (see also go.nature.com/2e6s8fo and go.nature.com/2bftgd4). The bill proposes to “preclude the listing of a species as threatened due to the likelihood of significant, cumulative economic effects that would result from such listing or from the likely resulting designation of critical habitat of the species”. Economic effects include those relating to public and private lands, property values, the provision of public services, employment and revenues available for governments. This triage process would effectively legitimize species extinctions by ruling out conservation programmes that conflict with economic interests. Conservation triage puts a mathematical gloss on extinctions, presenting them as neutral outputs of optimization algorithms and branding itself as effective science that is based on data and not dogma. It is crucial to oppose the ‘new conservation’ paradigm: it is performing a conceptual triage on conservation itself. Guillaume Chapron Swedish University of Agricultural Sciences, Uppsala, Sweden. Yaffa Epstein Uppsala University, Sweden. José Vicente López-Bao Oviedo University, Spain. guillaume.chapron@slu.se Add societal impact to the syllabus