What are heavy metals? Long-standing controversy over the scientific use of the term ‘heavy metals’ – proposal of a comprehensive definition

The term ‘heavy metals’ is commonly used in the environmental literature to refer to metals and metalloids associated with environmental pollution, toxicity and adverse effects on biota. The term has been diversely defined, mostly in terms of density, relative atomic mass and atomic number. This diversity of definitions has raised questions about the nomenclature of these elements. The inclusion of the metalloid As and the nonmetal Se with heavy metals is also an important issue. Some people have called the term as meaningless, imprecise and poorly defined and have suggested abandoning the use of the term. The term itself may not be problematic but the careless and inconsistent use of terminology has led to a confusion about the meaning of the term. The use of the term may be continued but it should be defined in a more comprehensive and scientific way. Here, a more comprehensive definition of the term ‘heavy metals’ is suggested as ‘naturally occurring metals having atomic number (Z) greater than 20 and an elemental density greater than 5 g cm^?3.’ A screening of the Periodic Table according to this definition yields 51 elements to be called ‘heavy metals.’ As and Se are excluded from heavy metals.     

Does digitalization matter in green preferences in nexus of output volatility and environmental quality?

Environmental Science and Pollution Research - The fact is that output volatility and carbon dioxide (CO2) emissions move together over the period. This empirical study examines the dynamic effect...     

Are bioplastics an ecofriendly alternative to fossil fuel plastics?

Environmental Chemistry Letters - More than 390 million tons of fossil fuel plastics have been produced in 2022, and plastic pollution has become a major health issue for humans and ecosytems....     

Environmental chemistry in the twenty-first century

Human society actually faces many environmental challenges such as environmental pollution, climate changes and loss of biodiversity. These issues induce major risks for ecosystems and are a serious threat for further life on Earth. Anthropogenic pressure may continue to exacerbate the present-day problems. Prevention and mitigation of environmental issues demands sound science and dedicated political support. For that, environmental chemistry is a central and multidisciplinary science that will provide new concepts and applied methods to solve actual environmental issues. Here, we outline the scope of environmental chemistry. The Anthropocene era and major chemical disasters are discussed. We present also the challenges of atmospheric chemistry, analytical chemistry, statistics and chemometrics, and education in environmental chemistry.     

Recent progress in bioethanol production from lignocellulosic materials: A review

Natural energy sources like petrol and diesel are going to be diminished in the coming future which will lead to increase in the prices and demands of fossil fuels. Therefore, it is important to find a sustainable alternate of fossil fuels. Bioethanol is one of the alternatives, which is produced from different feedstocks including sugar-based, starch-based and lignocellulose-based materials through fermentation. Since sugar-based (sugar cane and sugar beet) and starch-based (corn) materials are sources of staple food, therefore, research on lignocellulosic materials for bioethanol production is a subject of recent studies. Ethanol production from lignocellulosic materials involves different steps, such as pretreatment, hydrolysis, followed by fermentation process and finally ethanol purification. In this review, we have summarized the recent progresses in bioethanol production and processing from lignocellulosic materials.     

Prevalent fecal contamination in drinking water resources and potential health risks in Swat, Pakistan

Fecal bacteria contaminate water resources and result in associated waterborne diseases.This study assessed drinking water quality and evaluated their potential health risks in Swat, Pakistan. Ground and surface drinking water were randomly collected from upstream to downstream in the River Swat watershed and analyzed for fecal contamination using fecal indicator bacteria(Escherichia coli) and physiochemical parameters(potential of hydrogen, turbidity, temperature, electrical conductivity, total dissolved solid, color, odor and taste). The physiochemical parameters were within their safe limits except in a few locations, whereas, the fecal contaminations in drinking water resources exceeded the drinking water quality standards of Pakistan Environmental Protection Agency(Pak-EPA),2008 and World Health Organization(WHO), 2011. Multivariate and univariate analyses revealed that downstream urbanization trend, minimum distance between water sources and pit latrines/sewerage systems, raw sewage deep well injection and amplified urban,pastures and agricultural runoffs having human and animal excreta were the possible sources of contamination. The questionnaire survey revealed that majority of the local people using 10–20 years old drinking water supply schemes at the rate of 73% well supply,13% hand pump supply, 11% spring supply and 3% river/streams supply, which spreads high prevalence of water borne diseases including hepatitis, intestinal infections and diarrhea, dysentery, cholera, typhoid fever, jaundice and skin diseases in children followed by older and younger adults.     

Polylactic acid synthesis,biodegradability, conversion to microplastics and toxicity: a review

Global pollution by plastics derived from petroleum has fostered the development of carbon–neutral, biodegradable bioplastics synthesized from renewable resources such as modern biomass, yet knowledge on the impact of bioplastics on ecosystems is limited. Here we review the polylactic acid plastic with focus on synthesis, biodegradability tuning, environmental conversion to microplastics, and impact on microbes, algae, phytoplankton, zooplankton, annelids, mollusk and fish. Polylactic acid is a low weight semi-crystalline bioplastic used in agriculture, medicine, packaging and textile. Polylactic acid is one of the most widely used biopolymers, accounting for 33% of all bioplastics produced in 2021. Although biodegradable in vivo, polylactic acid is not completely degradable under natural environmental conditions, notably under aquatic conditions. Polylactic acid disintegrates into microplastics faster than petroleum-based plastics and may pose severe threats to the exposed biota.