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environmental chemistry h kaur pdf 27
Analysis articles provide an in-depth examination of energy and environmental technologies, strategies, policies, and overarching conceptual frameworks that will be of interest to the journal's wide and global readership. They should present new methods and data and fresh insights, and should be written for a scientifically literate audience. They must demonstrate scholarly rigor and tightness of presentation comparable to articles in mainstream science.
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The industrialization of the agricultural sector has increased the chemical burden on natural ecosystems. Pesticides are agrochemicals used in agricultural lands, public health programs, and urban green areas in order to protect plants and humans from various diseases. However, due to their known ability to cause a large number of negative health and environmental effects, their side effects can be an important environmental health risk factor. The urgent need for a more sustainable and ecological approach has produced many innovative ideas, among them agriculture reforms and food production implementing sustainable practice evolving to food sovereignty. It is more obvious than ever that the society needs the implementation of a new agricultural concept regarding food production, which is safer for man and the environment, and to this end, steps such as the declaration of Nyéléni have been taken.
The chemical fractionation identifies main binding sites and quantifies the strength of a metal binding to particulates. The strength of the metal binding determines mobility of particular elements and their further bioavailability. There are different methods of chemical fractionation. BCR method of sequential fractionation used in this study enabled us to determine four fractions of Cr bound to the sediments: I, exchangeable forms; II, forms of Cr associated with free Fe and Mn oxides; III, forms bound to organic matter; IV, residual phase of metals bound into lithogenic minerals (Baran and Tarnawski 2015). Fraction III is regarded very important for Cr distribution due to high affinity of Cr to organic matter (Baran and Tarnawski 2015; Shaheen and Rinklebe 2014). Due to different ground geochemistry, we found slight differences between particular locations; however, on average, more than 96% of Cr bound to the sediments appeared in fraction III (68.2%) and IV (28.7%) (Tab. 3). It suggests strong association of Cr with the bottom sediments and its highly limited bioavailability. The weakly bound fractions I and II constituted on average 1.4% and 1.6%, respectively. According to the Risk Assessment Code (Singh et al. 2005) we found low risk of chromium release from the bottom sediments.
Organic matter content, pH, redox potential, and the content of inorganic and organic pollutant are the main factors determining phytotoxicity of the sediment (Du Laing et al. 2009). It seems that high concentrations of Cr in the sediments did not threaten C. cophocarpa vegetation at the experimental sites. This was mainly due to the sorption of chromium by organic particles of the sediments, which also limited Cr availability to the plants. PEC values for Cr, exceeded at all experimental sites, negatively affected benthic organisms. Strong Cr-sediment binding rate combined with roots not participating in mineral uptake were the reasons of relatively poor Cr accumulation by Callitriche. Due to their simplified structure, the plant roots most likely do not have the capacity to efficiently change the redox potential. Moreover, alkaline pH of water and the sediments fosters Cr precipitation (Kyzioł-Komosińska et al. 2018). Based on the physicochemical properties of Cr in low redox potential and alkaline pH of water and sediment as well as strong association of Cr into the sediment, we can predict that Cr(III) was the dominant form at the polluted sites (Kotaś and Stasicka 2000). However, changes in the redox potential, e.g., during sediment deposition on the land, may alter chemical forms of metals bound in the solid phase form. This phenomenon is important when polluted sediments are subjected to oxidation, as it facilitates the element release into the aqueous phase according to the changes of Cr speciation from tri- to hexavalent. As a consequence, the metallic element becomes bioavailable to aquatic plants. Finally, we can speculate that environmental threat caused by chromium released from the sediments would be related to the following factors: (1) flood, due to translocation of the sediments to drinking water reservoirs; (2) pH changes, as acidic pH increases mobility of heavy metallic compounds/ions; and (3) sediment oxidation promoted by sediment deposition and/or land drainage.
The study demonstrated a successful acclimatization of Callitriche cophocarpa to strongly Cr-polluted environment. The plants grew without any signs of degeneration in their anatomical structures and maintained their physiological status at a similar level as the control plants. The species accumulated Cr in its shoots and roots, but due to poor Cr bioavailability in the sediments and the simplified root structure, bioconcentration factors were low. Extraordinary physiological tolerance to extremely high Cr concentrations in water, as shown in laboratory conditions, and in the bottom sediments, as described in this paper, makes this macrophyte a promising candidate for the reclamation of Cr-contaminated aquatic systems. Flood was the only environmental factor that affected the plant acclimatization. For use in the phytoremediation practice, we suggest to cultivate this species under controlled (pH, redox potential, water disturbances) conditions.
The first legislation providing federal authority for regulating pesticides was enacted in 1910.[17] During the 1940s, manufacturers produced large amounts of synthetic pesticides and their use became widespread.[18] Before the first World War, Germany was the world's leading chemical industry and exported most of the dyes and other chemicals that were used in the United States. War implemented tariffs that stimulated the growth of the chemical industry in the U.S., which made chemistry a prestigious occupation as this industry expanded and became profitable. Money and ideas flowed back from Europe after the U.S. entered WWI, changing the way Americans interacted with themselves and nature, and the industrialization of war hastened the industrialization of pest control.[19] Some sources consider the 1940s and 1950s to have been the start of the "pesticide era."[20] Although the U.S. Environmental Protection Agency was established in 1970 and amendments to the pesticide law in 1972,[17] pesticide use has increased 50-fold since 1950 and 2.3 million tonnes (2.5 million short tons) of industrial pesticides are now[when?] used each year.[15] Seventy-five percent of all pesticides in the world are used in developed countries, but use in developing countries is increasing.[21] A study of USA pesticide use trends through 1997 was published in 2003 by the National Science Foundation's Center for Integrated Pest Management.[16][22]
Available pesticides are not sufficient and new developments are needed. Continued research into the basic biology of pests may identify new vulnerabilities and produce new pesticides; it may also yield pesticides with better financial and environmental characteristics than those presently used.[24] Plant-derived pesticides, or "botanicals", have been developing quickly. These include the pyrethroids, rotenoids, nicotinoids, and a fourth group that includes strychnine and scilliroside.[9] In 2010, the development of a new class of fungicides called paldoxins was announced. These work by taking advantage of natural defense chemicals released by plants called phytoalexins, which fungi then detoxify using enzymes. The paldoxins inhibit the fungi's detoxification enzymes. They are believed to be safer and greener.[13]
Pesticides are used to control organisms that are considered to be harmful, or pernicious to their surroundings.[28] For example, they are used to kill mosquitoes that can transmit potentially deadly diseases like West Nile virus, yellow fever, and malaria. They can also kill bees, wasps or ants that can cause allergic reactions. Insecticides can protect animals from illnesses that can be caused by parasites such as fleas.[28] Pesticides can prevent sickness in humans that could be caused by moldy food or diseased produce. Herbicides can be used to clear roadside weeds, trees, and brush. They can also kill invasive weeds that may cause environmental damage. Herbicides are commonly applied in ponds and lakes to control algae and plants such as water grasses that can interfere with activities like swimming and fishing and cause the water to look or smell unpleasant.[29] Uncontrolled pests such as termites and mold can damage structures such as houses.[28] Pesticides are used in grocery stores and food storage facilities to manage rodents and insects that infest food such as grain. Each use of a pesticide carries some associated risk. Proper pesticide use decreases these associated risks to a level deemed acceptable by pesticide regulatory agencies such as the United States Environmental Protection Agency (EPA) and the Pest Management Regulatory Agency (PMRA) of Canada. 2ff7e9595c
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