Baljit Singh

Bio: Baljit Singh is an academic researcher from Himachal Pradesh University. The author has contributed to research in topics: Self-healing hydrogels & Drug delivery. The author has an hindex of 33, co-authored 112 publications receiving 3957 citations.

Polysaccharides as safer release systems for agrochemicals

Abstract: Agrochemicals are used to improve the production of crops. Conventional formulations of agrochemicals can contaminate the environment, in particular in the case of intensive cropping. Hence, there is a need for controlled-release formulations of agrochemicals such as polysaccharides to reduce pollution and health hazards. Natural polysaccharides are hydrophilic, biodegradable polymers. This article reviews the use of polysaccharides in the form of micro- and nanoparticles, beads and hydrogels. The main points are: (1) slow release formulations minimize environmental impact by reducing agrochemical leaching, volatilization and degradation. For example, 50 % of the encapsulated insecticide chlorpyrifos is released in 5 days, whereas free chlorpyrifos is released in 1 day. (2) Slow release formulations increase the water-holding capacity of soil. (3) Slow release formulations better control weeds in the long run. (4) Polymer-clay formulations store ionic plant nutrients. (5) Polymer hydrogel formulations reduce compaction, erosion, and water run-off. They increase soil permeability and aeration, infiltration rates, and microbial activity, and, in turn, plant performance. In conclusion, polysaccharide formulations can be used for safer use of agrochemicals.

Wastewater Treatment Works (WwTW) as a Source of Microplastics in the Aquatic Environment

Abstract: Municipal effluent discharged from wastewater treatment works (WwTW) is suspected to be a significant contributor of microplastics (MP) to the environment as many personal care products contain plastic microbeads. A secondary WwTW (population equivalent 650 000) was sampled for microplastics at different stages of the treatment process to ascertain at what stage in the treatment process the MP are being removed. The influent contained on average 15.70 (±5.23) MP·L–1. This was reduced to 0.25 (±0.04) MP·L–1 in the final effluent, a decrease of 98.41%. Despite this large reduction we calculate that this WwTW is releasing 65 million microplastics into the receiving water every day. A significant proportion of the microplastic accumulated in and was removed during the grease removal stage (19.67 (±4.51) MP/2.5 g), it was only in the grease that the much publicised microbeads were found. This study shows that despite the efficient removal rates of MP achieved by this modern treatment plant when dealing with su...

Pathways for degradation of plastic polymers floating in the marine environment

Abstract: Each year vast amounts of plastic are produced worldwide. When released to the environment, plastics accumulate, and plastic debris in the world's oceans is of particular environmental concern. More than 60% of all floating debris in the oceans is plastic and amounts are increasing each year. Plastic polymers in the marine environment are exposed to sunlight, oxidants and physical stress, and over time they weather and degrade. The degradation processes and products must be understood to detect and evaluate potential environmental hazards. Some attention has been drawn to additives and persistent organic pollutants that sorb to the plastic surface, but so far the chemicals generated by degradation of the plastic polymers themselves have not been well studied from an environmental perspective. In this paper we review available information about the degradation pathways and chemicals that are formed by degradation of the six plastic types that are most widely used in Europe. We extrapolate that information to likely pathways and possible degradation products under environmental conditions found on the oceans' surface. The potential degradation pathways and products depend on the polymer type. UV-radiation and oxygen are the most important factors that initiate degradation of polymers with a carbon-carbon backbone, leading to chain scission. Smaller polymer fragments formed by chain scission are more susceptible to biodegradation and therefore abiotic degradation is expected to precede biodegradation. When heteroatoms are present in the main chain of a polymer, degradation proceeds by photo-oxidation, hydrolysis, and biodegradation. Degradation of plastic polymers can lead to low molecular weight polymer fragments, like monomers and oligomers, and formation of new end groups, especially carboxylic acids.