Department of Chemistry

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1,1,1-Trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) and its derivatives in marketed Clarius werneri caught from Uganda’s major urban wetlands
(Journal of Toxicology and Environmental Health Sciences, 2014-07-29) Nnamuyomba, Proscovia; Jolocam Mbabazi; Muhammad Ntale
The presence of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) and derivatives in the Clarius werneri of Uganda’s major urban wetland ecosystems was investigated. Solid dispersion extraction method for extraction, florisil column method for clean-up, gas chromatograph equipped with an electron capture detector (GC-ECD) for analysis and gas chromatograph equipped with mass spectrophotometer (GC-MS) for confirmation of results were used in this study. The major DDT contaminants detected in the samples were p,p’-DDD, p,p’-DDE and p,p’-DDT which were found in 25, 22 and 21% of the samples, respectively. o,p’-DDD was detected in 19% and o,p’-DDT in 13% of the samples. For o,p’-DDE there were no measurable values since the levels were below limit of quantitation (LOQ). The concentrations of DDT derivatives ranged between ND-0.478 µg/kg for p,p’-DDE, ND-0.387 µg/kg for o,p’-DDD, ND-0.476 µg/kg for p,p’-DDD, ND-0.345 µg/kg o,p’-DDT and ND-0.556 µg/kg for p,p’- DDT. The concentration of total DDT in C. werneri was in the range of 1.111 to 1.328 µg/kg dry wt. Generally, all the samples had DDT derivative levels below the maximum residue limit recommended by Food and Agriculture Organisation/World Health Organization (FAO/WHO) Codex Alimentarius Commission.
Analysis of the Application of the Discovery Learning Model to Students' Creative Thinking Ability in Reaction Rate Material
(Indonesian Journal of Education Research (IJoER), 2023-08-28) Niski Nadila1, 2,; Louis-Charl Cloete Coetzee; Beatrice Arwenyo
Purpose of the study: The purpose of this study was to describe and determine the relationship between the implementation of the discovery learning model in the matter of the rate of reaction with the students' creative thinking abilities. Methodology: This research is a type of correlational descriptive research. The sampling technique used in this study is Simple Random Sampling. The instrument used in this research is the observation sheet. Data analysis techniques using normality and homogeneity tests. Main Findings: The results of this research are that the application of the Discovery Learning model to reaction rate material can be carried out very well. This is because the teacher corrects errors in applying the model at the next meeting and there is a relationship between the application of the Discovery Learning model and students' creative thinking abilities in the reaction rate material in class XI in the medium category. Novelty/Originality of this study: Provide information about the implementation of discovery learning learning models and their correlation with students' creative thinking abilities.
Application of biochar for the removal of actinides and lanthanides from aqueous solutions.
(Elsevier Inc., 2022) Bursztyn, Amalia L. Fuentesa; Arwenyo, Beatrice; Nanney, Andie L.M.; Ramirez, Arissa; Jamison, Hailey; Venson, Beverly; Mohan, Dinesh; Mlsna, Todd E.; Navarathna, Chanaka
Actinides and lanthanides are elements with unfilled f orbitals and are collectively labeled as the inner transition elements (ITEs). The actinide series includes 15 radioactive metallic ele ments with atomic numbers 89–103 (Cooper, 2000). The actinide elements are classified as light (Ac, Th, Pa, U, Np, Pu, Am) or heavy (Cm, Bk, Cf, Es, Fm, Md, No, Lr) based on their atomic numbers. The actinides fill their 5f sublevels progressively and exhibit char acteristics of both the d-block and the f-block elements. Elements of the actinide series can have oxidation states from +2 to plus +7. In addition to being radioactive, all actinides are paramagnetic and pyrophoric. Except for actinium with one oxidation state of +3, the other actinides are known to show variable oxidation states and more than one crystalline phase. To date, only the first four elements in the actinide series have been found to occur naturally.
Comparison of Acid- and Base-Modified Biochar Derived from Douglas Fir for Removal of Copper (II) from Wastewater
(SEPERATIONS:MDPI, 2024-03-01) Beatrice Arwenyo ,; Prashan M. Rodrig; Olalekan A. Olabode; Hashani P. Abeysingh; Jessie N. Tisdal; Rose C. Azuba; Todd E. Mlsna
Copper is a non-biodegradable heavy metal, and high levels in water bodies cause serious environmental and health issues. Douglas fir biochar has a higher number of carboxylic, phenolic, and lactonic groups, which provide suitable active sites for copper removal. Douglas fir biochar (BC) was modified using 20% solutions of KOH (KOH/BC), H2SO4, (H2SO4/BC), and Na2CO3 (Na2CO3/BC). All materials were characterized using SEM, SEM-EDS, FTIR, TGA, XRD, BET, and elemental analysis. These modifications were done to compare the activations of those sites by measuring copper removal efficiencies. KOH/BC, H2SO4/BC, and Na2CO3/BC materials gave surface areas of 389.3, 326.7, and 367.9 m2 g−1, respectively, compared with pristine biochar with a surface area of 578.9 m2 g−1. The maximum Langmuir adsorption capacities for Na2CO3/BC, KOH/BC, BC, and H2SO4/BC were 24.79, 18.31, 17.38, and 9.17 mg g−1, respectively. All three modifications gave faster kinetics at 2 mg/L initial copper concentrations (pH 5) compared with pristine BC. The copper removal efficiency was demonstrated in four different spiked real water matrices. The copper removals of all four water matrices were above 90% at 2 mg/L initial concentration with a 2 g/L biochar dosage. The competitive effects of Pb2+, Zn2+, Cd2+, and Mg2+ were studied at equimolar concentrations of Cu2+ and competitive ions for all four materials.
Contribution of modified P-enriched biochar on pH buffering capacity of acidic soil
(Elsevier Journal of Environmental Management, 2022-11-06) Arwenyo, Beatrice; Varco, Jac J.; Dygert, Andrew; Brown, Sydney; Pittman, Charles U.; Mlsna, Todd
Biochar can directly hold cations in soil because of the negative charge that exists on its surfaces. Besides, improving soil cation exchange capacity, the negative charges on biochar surfaces can buffer acid soil by pro tonation and deprotonation mechanisms. Moreover, biochar ameliorates soil acidity due to the presence of ox ides, carbonates, and hydroxides of its basic cations (Ca, Na, K, and Mg). Both biochar surface functional group and basic cation concentrations can be altered by modification with chemical agents which can affect its soil pH buffering capacity. However, the impact of modified biochar application on soil pH buffering capacity is still scanty. This study investigated the pH buffering capacity of acidic soil amended with three P-enriched modified Douglas fir biochars and compared this buffering capacity to amendment with untreated Douglas fir biochar. These three P-enriched biochars, were prepared by treating Douglas fir biochar (DFB), respectively, with: 1) anhydrous calcium chloride (CaCl2) and potassium phosphate monobasic (KH2PO4), 2) calcium carbonate (CaCO3) and diammonium phosphate {(NH4)2HPO4} and 3) an aqueous solution of magnesium sulfate (MgSO4), potassium hydroxide (KOH) and potassium phosphate monobasic (KH2PO4). The three P-enriched biochars were designated as CCPP, CAPP and MSPP, respectively. The soil pH buffering abilities were largely dependent on the added biochar’s alkalinity and ash contents. The residual soil CEC was highly correlated (r ≥ 0.9), with the soil buffering capacity. Both alkalinity and pH buffering capacity improved following the order CCAP > CCPP > MSPP > DFB, while residual soil CEC followed the order CAPP > MSPP > CCPP > DFB. The pH buffering ca pacity of the soil after amendments with 10% CAPP, CCPP MSPP and BFB rose by 84.8, 58.3, 3.0 and 2.5%, respectively. Whereas MSPP had higher concentrations of K+ and Mg2+, greater concentrations of Ca2+ were present in CCAP and CCPP than MSPP. So, Ca2+ concentrations in biochar exerts a greater influence on alkalinity and buffering capacity than Mg2+ and K+ because of 1) its smaller effective hydration radius and larger charge density. 2) calcium hydroxide has a greater water solubility than magnesium hydroxide providing more available base. Since pH buffering capacity depends on cation exchange sites, soil additives containing Ca2+ are prone to create greater impacts than Mg2+ and K+ additives.
Dichloro-diphenyl-trichloroethane (DDT) residue levels in marketed Silver Fish (Rastreneobola argentea) caught from major water bodies in Uganda
(Academic Journal, 2014-06-25) Nnamuyomba, Proscovia; Mbabazi, Jolocam; Ntale Muhammad
Silver fish (Rastreneobola argentea) samples from Lake Victoria and Lake Kyoga were analyzed for dichloro-diphenyl-trichloroethane (DDT) and metabolites using a Gas Chromatograph equipped with an Electron Capture Detector. Confirmation of results was by Gas Chromatography equipped with Mass Spectrophotometer (GC-MS). DDT and metabolites were detected in 90% of the total samples (63 out of 70). pp’ DDT was the most frequently detected residues in the samples whereas op’ DDE was detected in none of the samples. The mean ΣDDT concentrations in fish from Lake Victoria varied from 0.147 to 0.396 µg/kg while that in Lake Kyoga varied from 0.207 to 0.506 µg/kg dry wt of fish sample. The concentration of total DDT in the fish samples ranged from 0.147 to 0.506 µg/kg dry wt. This was far below the recommended FAO limit of 5000 µg/kg for fish (edible portion), implying that the fish are safe for human consumption.
Dichlorodiphenyltrichloroethane (DDT) and its metabolites in house dust, soil and selected food crops from indoor residual sprayed areas of Apac and Oyam Districts, Uganda
(African Journal of Pure and Applied Chemistry, 2022-06-12) Mukasa paul; Wasswa John; Namuyomba Proscovia; Ntambi Emmanuel
Dichlorodiphenyltrichloroethane (DDT) levels and its metabolites are reported in 75 soil and 75 vegetable samples from the vicinity of homesteads sprayed with DDT during indoor residual spraying (IRS) pilot exercise, carried out in 2008 in Apac and Oyam districts, Uganda as a measure to control malaria. The samples were randomly and conveniently collected in 2020 from selected villages of the districts, extracted using solid dispersion and multi-residue methods for soil and vegetable samples, respectively and analyzed using GC-ECD and GC-MS. DDT residues were detected in all samples collected. The ΣDDT (µg kg-1) in all indoor house dust, outdoor soil samples from villages of Apac and Oyam districts and control areas were 69.9±20.9 and 8.9±4.7, 113.4±22.6 and 15.4±4.3, and 1.13±0.27 and 1.8±0.9, respectively. ΣDDT were significantly higher (p < 0.05) in the study areas than the control areas. In vegetables, ∑DDT (µg kg-1) ranged between 1.7±0.3 and 8.3±4.0 and 2.3±0.4 and 11.4±7.5 in the study and control areas, respectively. Abelmoschus esculentus and Gynandropsis gynandra had the highest levels. The results suggest that IRS had an effect on DDT levels in the environment. However, ∑DDT in vegetables were significantly below (P < 0.05) the EU EMRL, thus, the results raise no concern regarding the potential health effects of DDT to the residents. Nevertheless, due to bioaccumulation effects of DDT, to control malaria, measures like Ecohealth rather than IRS of DDT should be embraced.
Effects of environmental temperature on the growth performance of a tropical Oreochromis esculentus (Graham, 1928). Implications for the species conservation
(Willey., 2022-09-14) Nagayi, Kalule Yawe jane; Kisakye Joseph; Tenywa Mwanja Matthew ,; Nattabi. Juliet; Opio Alfonse
Climate variability and change are currently recognised global challenges. However, the impacts of rising temperatures may be greatest on tropical freshwater fish, which already exist in warm environments and may be living close to their critical thermal maximum. However, there is limited species- specific information on tropical species’ adaptive capacity to increased temperature. This study examined various growth attributes in juvenile populations (farmed, L. Kacheera and L. Nabisojjo) of a critically endangered tropical Oreochromis esculentus to determine its adaptive potential. Fish were acclimated at 25, 28, 31 and 34°C for 28 days. Overall, survival rates were high. Growth coefficient b was not significantly different from three (b = 3) in all treatments, implying isometric growth. The specific growth rates (SGRs), body condition K, and hepato- somatic indices (his) declined as the acclimation temperatures increased. Although SGR showed significant variations only among populations, the highest in L. Nabisojjo, K and HSI showed significant variations among treatments. Overall, the growth attributes declined at higher acclimation temperatures, but remained within acceptable ranges, implying that the species may attain normal growth at elevated temperatures experienced in outdoor aquaculture systems, despite its warm environmental background. Hence, we recommend selective breeding for temperature resilience and species introduction into aquaculture using broodstock from L. Nabisojjo.
Effects of thermal acclimation and ecological background on the physiological responses of juvenile Oreochromis esculentus (Graham, 1928). Implications for the species adaptive capacity to global warming
(Aquaculture Research, 2021-10-12) Nagayi, Jane Kalule Yawe; KisakyeJohn , Joseph; Tenywa Mwanja, Matthew; Nattabi; Opio Alfonse
Climate change is a recognized global concern in the 21st century. Water temperature elevation is likely to affect fish physiological and ethological function, causing great economic losses for fisheries resources and aquaculture production. Fish are particularly vulnerable to climate change as they are unable to control their body temperatures with changes in environmental temperature. This study assessed the effects of thermal acclimation in three juvenile populations of Oreochromis esculentus on the critical thermal maximum CTmax, cortisol, biochemical and haematological responses to acute temperature increase (0.3°Cmin−1). Fish from Senya farm, Lake Kacheera and Lake Nabisojjo were acclimated at 25°C, 28°C, 31°C and 34°C for 21 days at Kajjansi aquaculture research and development centre KARDC. The CTmax and blood cell counts increased, while plasma cortisol, glucose and proteins decreased at higher acclimation temperatures. Two-way ANOVA showed significant differences among treatments in CTmax, cortisol, proteins and erythrocytes indices, but not in glucose and leucocytes. However, significant variations among populations were only showed in CTmax. Overall, these results suggest that O. esculentus can respond to higher climate change induced temperatures, when allowed time for acclimation. Since temperature adaptation not only depends on the parameters assessed in this study, we recommend further investigations into metabolic rate and digestive enzymatic activity.
The impact of septic systems density and nearness to spring water points, on water quality
(African Journal of Environmental Science and Technology, 2017-01-18) Arwenyo, B.; Wasswa, J.; Nyeko, M.; Kasozi, G. N.
Worldwide, 1.1 billion people do not have access to clean water and as a result, 2 million children die annually due to preventable waterborne diseases. In Uganda, 440 Children die every week of waterborne diseases. High prevalence of this death is reported in the peri urban areas. It is still unclear however the causes of water pollution in the peri-urban areas. The improper use of onsite sanitation facilities such as latrines and septic systems may lead to groundwater contamination. It is true that drain field of septic system located too close to water point, and or over population of the septic systems in a small area can lead to pollution of groundwater. Our study investigated the impact of septic systems density and nearness to water points on spring water quality. Samples from 15 spring wells were analysed for pH, nitrate and faecal coliform contamination. Locations and distances of spring from septic systems were determined using global positioning system (GPS) device and ArcGIS software, respectively. Water samples from all the spring wells had pH value less than 6.5, 66.7% had faecal coliform and 53% had nitrate above 2 mg L-1. While sample from one of the springs had nitrate concentration above the United States Environmental Protection Agency (US EPA) standard of 10 mg L- 1. It was also noted that coliform counts and nitrate concentrations increases with increase in number of septic systems surrounding the spring well. In addition, increase in distance between spring wells and septic systems indicated decrease in both coliform counts and nitrate concentration. It is therefore concluded that improper use of septic systems is one of the causes of groundwater pollution in the peri urban areas. The study recommends treatments of water from groundwater sources, regular monitoring of groundwater sources and proper design and siting of septic systems using more robust methodologies.
Inorganic nutrients and heavy metals in some wild edible plants consumed by rural communities in Northern Uganda:
(Elsevier Ltd., 2023-08-04) Alfred Nyeroa; Innocent Achayea; Godwin Upoki Anywarc; Geoffrey Maxwell Malingab
For centuries, wild edible plant species have sustained local communities across Africa by supplementing households’ diets in seasons of food shortage. Wild edible plants contain inorganic nutrients, which are essential for the proper functioning of organisms. However, their nutritional contents have not been well researched and are generally poorly understood. This study aimed to quantify the levels of inorganic micro-and macronutrients as well as heavy metals (Mg, Ca, K, Fe, Zn, Cd, Hg and Pb) in selected wild edible plants traditionally consumed among the Acholi communities in northern Uganda, and associated health risks of consuming them. The leaves and young stems of 12 wild edible plants, viz: Acalypha rhomboidea, Asystacia gangetica, Crassocephalum sacrobasis, Crotalaria ochroleuca, Heterotis rotundifolia, Hibiscus cannabinus, Hibiscus sp., Hibiscus surattensis, Ipomoea eriocarpa, Maerua angolensis, Senna obtusifolia and Vigna membranacea were air-dried and crushed to powder. The powders were then macerated using aqua regia solution and analyzed in triplicates using the Atomic Absorption Spectrophotometry (AAS). The target hazard quotient (THQ) of Pb was calculated for non-carcinogenic health risks. Mg, Ca, K, Fe, Zn and Pb were detectable in all the wild edible plants sampled. All inorganic nutrients (mg/ 100gdw), were below the Recommended Daily Allowance (RDA); Mg (9.4 ± 0.19 to 10.4 ± 0.15), Ca (119 ± 5.82 to 1265 ± 14.9), Fe (3.29 ± 0.02 to 11.2 ± 0.09), Zn (0.52 ± 0.02 to 2.36 ± 0.03). Hg and Cd were below detectable limits in all the samples tested. The content of Pb (0.69 ± 0.11 to1.22 ± 0.07) was higher than the CODEX and EU limits of 0.1 ppm (0.001 mg/g) but was below the recommended threshold of 1. The health risk assessment revealed no potential hazards both in children and adults. However, there is a need to study the bioavailability of Pb when the vegetables are consumed due to factors such as indigestion and antinutritional compounds
Kinetics and Thermodynamic Studies: Adsorption of Pb, Cr and Ni Ions from Spent Lubrication Oil (SLO) Using Acid Modified Clay
(American Journal of Analytical Chemistry, 2021-12) Sughnen Atsar, Felix; Kukwa, Donald; Ahule Wuana, Raymond; Arwenyo, Beatrice
Adsorption of Pb, Cr, and Ni ions from spent lubrication oil (SLO) by sulphuric acid modified clay (SAMC) was investigated considering the effect of contact time and temperature of the adsorption system. The removal percentage of the heavy metals was found to be temperature and contact time-dependent. Adsorption of the heavy metals increases with an increase in temperature and contact time with 95.0% - 100% adsorption recorded at the temperature of 331 K with the equilibration time of 12 hours. The thermodynamic and kinetics investigation of the adsorption process showed that the adsorption of these metals by the modified adsorbent is a spontaneous and endothermic physical adsorption process that followed the pseudo-second-order kinetic model.
Lead immobilization in simulated polluted soil by Douglas fir biochar-supported phosphate
(Elsevier Chemosphere, 2021-12-16) Varco, Jac J.; Dygert, Andrew; Atsar, Felix S.; Solomon, Sabrina; Venkatesh, Rooban; Thirumalai, K.G.; Pittman Jr., Charles U.; Mlsna, Todd
This study compared the lead (Pb2+) immobilization efficacy of biochar-supported phosphate to conventional in situ heavy metal immobilization methods (with lime, neat biochar and phosphate). The biochar-supported phosphate was obtained by treating Douglas fir biochar (BC) with anhydrous calcium chloride and potassium dihydrogen phosphate. The amount of Pb2+ immobilized was determined by comparing the concentration of ammonium nitrate extractable Pb2+ lead from lead-spiked soil (without amendment) to that of a 30 d incubation with (a) lead-spiked soil plus 5% (wt./wt.) biochar supported-phosphate, (b) lead-spiked soil plus 5% (wt./wt.) untreated Douglas fir biochar, (c) lead-spiked soil plus 5% (w/w) lime and (d) lead-spiked soil plus 5% (wt./wt.) potassium dihydrogen phosphate. The control (lead-spiked soil without amendment) produced the largest quantity (96.08 ± 9.22 mg L− 1 ) of NH4NO3-extractable Pb2+, while lead-spiked soil treated with 5% (wt./wt.) biochar-supported phosphate resulted in the lowest quantity of NH4NO3 extractable Pb2+ (0.3 ± 0.2 mg L− 1 ). The mechanism for immobilization of Pb2+ by BP occurs at pH < 7 through dissolution of hydroxyapatite embedded in BP during modification, followed by precipitation of insoluble Pb10(PO4)6(OH)2. The residual lead fraction in the lead-spiked soil increased by 20.9% following amendment with BP. These results indicate that biocharsupported phosphate is a candidate to reduce lead mobility (bioavailability) in polluted soil. This amendment may lower Pb2+ uptake into plants while minimizing the potential for water contamination due to Pb2+mobility.
Liver and renal biochemical profiles of people with sickle cell disease in Africa: a systematic review and meta-analysis of case-control studies
(MBC., 2023-08) Awor Silvia; Bongomin Flexi; Kaggwa Mark Mohan; Pebalo Francis; Epila Jackie; Malinga Geoffrey Maxwell; Oryema Christine; Nnamuyomba Proscovia; Abola Benard; Ongwech Acaye; Musoke David
Background Sickle cell disease (SCD) is a genetic blood disorder characterized by a painful vaso-occlusive crisis due to the sickling of red blood cells in capillaries. Complications often lead to liver and renal dysfunctions, contributing to morbidity and mortality, particularly for children under 5. This systematic review and meta-analysis aimed to evaluate the liver and renal functions of people with SCD (HbSS) compared to those without it (HbAA) in Africa. Methods The protocol was registered with PROSPERO (CRD42022346771). We searched PubMed, Embase, Web of Science, and Google Scholar using the keywords “liver function”, “renal function”, “sickle cell disease”, and “Africa” on 6th May 2023 for peer-reviewed articles with abstracts in English. We included case-control studies comparing SCD (HbSS) with controls without hemoglobinopathies (HbAA). We used the random-effect model to calculate the pooled average values for the blood tests of people with SCD in RStudio version 4.2.2. Results Overall, 17 articles were analyzed from five African countries involving 1312 people with SCD and 1558 controls. The pooled mean difference of liver enzymes aspartate transaminase (AST) was 8.62 (95% CI − 2.99–20.23, I2 = 97.0%, p < 0.01), alanine transaminase (ALT) 7.82 (95% CI − 0.16–15.80, I2 = 99%, p < 0.01) and alkaline phosphatase (ALP) − 2.54 (95% CI − 64.72 – 59.64, I2 = 99%, p < 0.01) compared to controls. The pooled mean difference for the renal biochemical profiles creatinine − 3.15 (95% CI − 15.02; 8.72, I2=99%, p < 0.01) with a funnel plot asymmetry of t = 1.09, df = 9, p = 0.3048 and sample estimates bias of 6.0409. The pooled mean difference for serum urea was − 0.57 (95% CI − 3.49; 2.36, I2 = 99%, p < 0.01), and the estimated glomerular filtration (eGFR) rate was 19.79 (95% CI 10.89–28.68 mL/min/1.73 m2, I2 = 87%, p < 0.01) compared to controls. Conclusion People with SCD have slightly elevated liver enzymes and estimated glomerular filtration rates compared to controls in Africa. With all the heterogeneity (I2) > 50%, there was substantial variation in the reported articles’ results.
Microplastics and Nano-Plastics: From Initiation to Termination
(Journal of Geoscience and Environment Protection, 2023-01-31) Awolesi, Oluwafemi; Oni, Peter; Arwenyo, Beatrice
Following the advent of the Industrial Revolution, plastic pollution has been a serious environmental issue while micro- and nano-plastics have been a cy nosure of researchers’ attention in the twenty-first century. This is due to the improved knowledge of its ecotoxicological effects and the global pushfor ward towards sustainability. There is a growing concern that the increasing presence of microplastics and nanoplastics (MNPs) in aquatic habitats poses a threat to marine life, and it is predicted that nanoplastics will be just as ubi quitous as macro- and micro-plastics, but far more destructive to living or ganisms due to their ability to infiltrate cells. Recent research has shown that marine and freshwater biota become entangled with plastic litter, which dis rupts the ecosystem. Aquatic creatures are known to absorb and deposit these new pollutants in their digestive systems, as has been documented in several studies. More recent research has also examined their co-occurrence and tox icity with other emerging contaminants, including their prevalence and ef fects in food, air, and soil. Using articles extracted from a six-year period from Scopus, ACS Publications and Google Scholar, this review explores the origins, fates, occurrence in the food chain, exposure routes, cellular interac tions of microplastics and nano-plastics, in addition to the ecotoxicological impacts, analytical methods, and the potential remedies for combating pollu tion and toxicity. Ultimately, this review is a comprehensive, updated adden dum to available reviews on micro- and nano-plastics.
Microplastics and Per- and Polyfluoroalkyl Substances (PFAS) Analysis in Sea Turtles and Bottlenose Dolphins along Mississippi’s Coast
(MDPI, Basel, Switzerland., 2023-01-18) Navarathna Chanaka M.; Pray Hannah; M Prashan. Rodrigo; Arwenyo Beatrice; McNeely Cassidy; Reynolds Henry; Hampton Natalie; Lape Katherine; Katie Roman; Heath Maddie; Stokes Sean; R Sameera. Gunatilake; Ariunbold Gombojav; Perez Felio; V. K. G Rooban . Thirumalai; Hassan EI Barbary; Elsayed Islam; Mohan Dinesh; Brown Ashli ,; Moore Debra; Reichley Stephen; Lawrence Mark; MlsnaTodd E.
Global plastic production and usage has increased annually for decades and microplastic pollutants ( 5 mm) are a growing concern. Microplastics in surface waters can adsorb and desorb harmful chemicals such as per- and polyfluoroalkyl substances (PFAS). Microplastics can accumulate across all tropic levels in the marine food web. The purpose of this research was to analyze the stomach and intestinal contents of stranded (Mississippi coast) bottlenose dolphins and sea turtles for the presence of microplastics and commonly found PFAS, PFOS, PFOA, and GenX. Gut contents were digested (10% KOH in 50% MeOH) and then analyzed for microplastics using pyrolysis gas chromatography-mass spectrometry (Pyro-GC-MS), Nile red microscopy, X-ray photo electron spectroscopy (XPS), and Raman spectroscopy. Digested sample filtrate was pre-concentrated using solid-phase extraction (SPE) before PFAS liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. The PFOS extraction and analysis had 98.6% recovery when validated with certified pike-perch fish reference material. The Nile red testing on most samples revealed the presence of microplastics (Table S1). The Pyro-GC-MS results from two samples confirmed the presence of the plasticizer acetamide. The Raman spectroscopy analysis indicated characteristic plastic peaks corresponding to polystyrene in one sample. PFOS (95.5 to 1,934.5 g/kg) was detected in three dolphin stomach samples. This project is part of a long-term study with the goal of a better understanding of microplastics and PFAS environmental contamination and their impact on bottlenose dolphins and sea turtles.
Organic Explosive Residues from Demining Sites in Amuru District, Northern Uganda
(Scientific Research Publishing, 2025) Ocaya, Jimmy; Arwenyo,Beatrice; Ongwech , Acaye; Nnamuyomba , Proscovia; Opio , Alfonse; Angwech ,Harriet; Kisitu , Jaffar
The study investigated the occurrence of explosive compounds at four demining sites in Amuru District, Northern Uganda. The concentrations of explosive compounds octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), 2,4,6-Trinitrophenyl-n-methylnitramine (tetryl), 2,4,6-trinitrotoluene (TNT), 2,6-dinitrotoluene (2,6-DNT),cyclotrimethylenetrinitramine (RDX), nitroglycerin (NG) and Pentaerythritol tetranitrate (PETN) in soil samples collected from the demining sites were determined by liquid chromatography-tandem mass spectrometry with atmospheric pressure chemical ionization (LC-MSMS-APCI). The LC-MSMS-APCI method was optimized and validated. The validation parameters included were accuracy, precision, recovery, linearity, selectivity, limits of detection, and limits of quantification. The limit of detection and quantification of the target analytes ranged from 4.5 - 32.1 ng·mL−1 and 17 - 102.9 ng·mL−1, respectively. Recovery of the target analytes from the soil samples ranged from 76% - 96%. The intra- and inter-day accuracy and precision values of below 15% indicated that the target analytes could be determined with reasonable accuracy and precision using the optimized method. The target analyte concentrations in soil samples ranged from 24.6 to 551.8 μg·g−1 with RDX and TNT being dominant. All the soil samples analyzed had explosive residue concentrations higher than the set chemical contamination values set by the US EPA PRGs Region 9 for Soil Screening Levels.
PFAS:
(Journal of Agricultural Chemistry and Environment,, 2023-08-31) Awolesi Oluwafemi; Oni Peter; Oshinowo Abiodun; Olubusoye Boluwatife; Owusu Faustina; Sunday Simeon Pama; Osobamiro Temitope; Ongwech Acaye; Awolesi Omotoyosi; Arwenyo Beatrice
The C-F bond is one of the strongest in organic chemistry. It is responsible for the great stability of perfluoroalkyl and polyfluoroalkyl substances, commonly referred to as “PFAS”, a group of man-made chemicals that include perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA). Thermal stability, surface activity, dielectric characteristics, chemical resistance, and inertness are just a few of the technical advantages that this group has over hydrocarbons, and since the 1950s, these chemicals have been largely utilized in a variety of domestic and industrial endeavors. The hydrophilic and lipophilic nature of this class of chemicals accounts for its uniqueness. Up until today, the chemistry and ecotoxicology of these chemicals continue to emerge. Issues concerning the destructive power of ignorance expedited by an ineffective regulatory institution continue to show that manufacturing chemicals are insufficient without giving serious thought to issues of openness and humanity’s awareness of its own safety. When discussing the nature of humanity and how it can be defined or redefined, it is important to allude to the significance of integrating business with ethics in its various forms. This paper highlights the importance of holding polluters accountable for PFAS contamination cleanup costs while emphasizing the need for chemical manufacturers to test and disclose the health and environmental effects of PFAS compounds. In addition, the sources, types, properties, applications, distribution, toxicological implications, regulations, and analytical methods associated with PFAS (per- and polyfluoroalkyl substances) are explored. The effectiveness of the remedial methods described in this paper needs to be progressively tested while exploring other sustainable approaches.
PFAS: Ecological Implications, Remedial Actions and Ethical Considerations
(Journal of Agricultural Chemistry and Environment, 2023-08-31) Awolesi, Oluwafemi; Oni, Peter; Oshinowo, Abiodun; Olubusoye, Boluwatife S.; Owusu, Faustina; Pama, Simeon Sunday; Osobamiro, Temitope; Ongwech, Acaye; Awolesi, Omotoyosi; Arwenyo, Beatrice
The C-F bond is one of the strongest in organic chemistry. It is responsible for the great stability of perfluoroalkyl and polyfluoroalkyl substances, commonly referred to as “PFAS”, a group of man-made chemicals that include perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA). Thermal stability, surface activity, dielectric characteristics, chemical resistance, and inertness are just a few of the technical advantages that this group has over hydrocarbons, and since the 1950s, these chemicals have been largely utilized in a variety of domestic and industrial endeavors. The hydrophilic and lipophilic nature of this class of chemicals accounts for its uniqueness. Up until today, the chemistry and ecotoxicology of these chemicals continue to emerge. Issues concerning the destructive power of ignorance expedited by an ineffective regulatory institution continue to show that manufacturing chemicals are insufficient without giving serious thought to issues of openness and humanity’s awareness of its own safety. When discussing the nature of humanity and how it can be defined or redefined, it is important to allude to the significance of integrating business with ethics in its various forms. This paper highlights the importance of holding polluters accountable for PFAS contamination cleanup costs while emphasizing the need for chemical manufacturers to test and disclose the health and environmental effects of PFAS compounds. In addition, the sources, types, properties, applications, distribution, toxicological implications, regulations, and analytical methods associated with PFAS (per- and polyfluoroalkyl substances) are explored. The effectiveness of the remedial methods described in this paper needs to be progressively tested while exploring other sustainable approaches.
Phosphorus availability from magnesium-modified P-enriched Douglas fir biochar as a controlled release fertilizer
(Soil Use and Management, 2021-08-04) Arwenyo, Beatrice ; Varco, Jac J.; Dygert, Andrew ; Mlsna, Todd
Phosphorus (P) is one of the essential elements required for plant growth and de velopment. However, worldwide, many agricultural soils can be deficient in P. The use of fertilizers and manures as a source of P can be costly, limited in sup ply in some regions of the world and ecologically unfavourable. Nutrient-enriched biochar has been suggested as a relatively cost-effective and eco-friendly P source. This study investigated P availability from Douglas fir biochar modified with mag nesium chloride and potassium hydroxide solutions only (B), and modified P enriched Douglas fir biochar B50, B100 and B150 corresponding to B treated with 50, 100 and 150 mg P L−1 solutions of potassium phosphate monobasic. Triple super phosphate fertilizer (FC) and a control treatment without phosphate added (C) used as a reference treatment. Treatments were added to soil in varied amounts to obtain the same P rate of 30 kg P ha−1. Aboveground biomass dry weight yield (R2 = .7) and plant height (R2 = .86) improved with P contents. After harvest, re sidual soil P for the FC treatment was significantly greater than all other treatments (p-value = 1.7848 E-6, R2 = .8). Plant height and aboveground dry weight biomass were greater with B150 compared to B50 at the same total P loading, suggesting that the greater P concentration of the biochar (B150) resulted in less tightly bound P and was therefore more available for plant uptake. This study showed promise of utilizing P-enriched Douglas fir biochar as a slow-release P fertilizer.

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