Environmental context. Pollution of the aquatic environment by oxytetracycline can lead to microbial resistance thereby compromising the efficacy of current medication regimes. Adsorption by colloidal and sediment particles reduces the rate at which oxytetracycline degrades, whereas the longer the antimicrobial remains in the aquatic environment, the greater the danger of microbial resistance. There is need therefore for a fuller understanding of the kinetics of degradation of oxytetracycline in aquatic ecosystems before measures for mitigating pollution by the antimicrobial can be designed.Abstract. The persistence of oxytetracycline in an aquatic microcosm and distilled water control experiments, was studied over a period of 90 days. An immediate 35 % loss as a result of adsorption by the sediment was observed in the microcosm experiment soon after charging. Subsequently triphasic linear rates of oxytetracycline degradation were observed for both the water phase (3.1 Â 10 À2 , 5.8 Â 10 À3 and 1 Â 10 À3 mg g À1 day À1 ) and sediment phase (4.8 Â 10 À2 , 6.5 Â 10 À3 and 2 Â 10 À4 mg g À1 day À1 ). Degradation is attributed to photolysis and microbial degradation of the free oxytetracycline in solution, and microbial degradation of the colloidal and sediment particle adsorbed speciation forms. The distilled water control exhibited biphasic zero order kinetics attributed to hydrolysis (2 Â 10 À6 mg g À1 day À1 ) and microbial degradation (2.7 Â 10 À3 mg g À1 day À1 ) under dark conditions, and monophasic zero order kinetics attributed to photolysis (6.9 Â 10 À3 mg g À1 day À1 ) under sunlight exposure. A kinetic model that takes into account hydrolysis, photolysis, microbial degradation and adsorption of the antibiotic by colloidal and sediment particles, is presented to account for the monophasic, biphasic and triphasic zero order kinetics observed in the control and microcosm experiments. Possible remediation strategies for mitigating aquatic environments polluted by the antimicrobial are discussed.

Fibrous chelating cation exchangers were derived from chloromethylstyrene-grafted polyethylenecoated polypropylene filamentary fiber and its nonwoven cloth. Ligand contents and acid capacities of the resulting chelating filamentary fiber (FIDA-f) and cloth (FIDA-c) were ca. 2 mmol/g and ca. 4 mequiv/g, respectively. A distribution study by using FIDA-c clarified that the selectivity sequence of divalent metal ions is Mg(Capacities of FIDA-c in mmol/g at around pH 5 were as follows: for divalent ions, Ca(II) ) 0.91, Mg(II) ) 0.98, Cd(II) ) 1.5, Ni(II) ) 1.5, Pb(II) ) 1.6, and Cu(II) ) 1.8; for trivalent ions, La(III) ) 0.75, Gd(III) ) 0.92, and Lu(III) ) 1.0. A column-mode study using a FIDA-f packed column revealed that breakthrough capacities for Cu(II) (ca. 1 mmol/g) were not dependent on flow rates up to 200-300 h -1 in space velocity but slightly decreased with a further increase in the flow rate. Conditioning-adsorption-elution operations of the FIDA-f column were repeated many times (n ) 21) under various conditions; averages of the column capacity for Cu(II) and the amount of eluted Cu(II) were 1.9 ( 0.1 and 1.9 ( 0.2 mmol/g, respectively.

The surface composition and surface properties of water hyacinth (Eichhornia crassipes) root biomass were studied before and after extraction with dilute nitric acid and toluene/ethanol (2/1, v/v) followed by ethanol, using Fourier Transform Infra-red (FT-IR) spectroscopy, thermogravimetric analysis, x-ray diffraction, scanning electron microscopy. FT-IR absorption bands were obtained at 3421, 2855, 1457 and 1035 cm-1 (O-H stretch, C-H vibration, C-H asymmetric deformation, and CO stretch, respectively) and 1508, 1541 and 1559 cm-1 (all aromatic skeletal vibrations characteristic of lignin), as well as a C=O carboxylate stretch vibrational band at 1654 cm-1. Scanning electron microscopy confirmed the root biomass to be amorphous and not to have a strongly structured surface. The dilute mineral acid and organic solvent treatment increased crystallinity. Thermogravimetric analysis Studies show that the treated biomass are more thermally stable than the untreated biomass. Data are presented showing that dilute mineral acid and organic solvent treatment resulted in a decrease in the amount of lignin in the biomass. The implications of the decrease in the percentage of lignin on the adsorption of volatile polar organic solvents and non-polar n-alkane hydrocarbons is discussed.

Formation of disinfectant by-products was investigated in the Harare water supply system from February to April 2015. Sampling sites were selected from the lake, Morton Jaffray Water Treatment Works and critical points in the distribution system. The spatial variations of trihalomethanes and selected water quality parameters were investigated for 15 sampling points in 5 sampling campaigns to assess suitability for drinking. All trihalomethane species were measured, namely chloroform, bromodichloromethane, dibromochloromethane and bromoform. Only chloroform and bromodichloromethane were detected. The study confirmed that there is trihalomethanes formation in the Harare water distribution system and that it is affected by the residence time and presence of organic matter in the system. However, the levels of trihalomethanes are generally within the levels suggested by the World Health Organization. Only bromodichloromethane presents a risk for long-term exposure as it had levels that exceeded the limit for long-term exposure suggested by the United States Environmental Protection Agency. Bromodichloromethane, turbidity and free residual chlorine levels were not suitable for drinking in some of the zones. Boosting of chlorine residuals is necessary especially in areas with free chlorine less than 0.2 mg/L. Injection of ammonia, periodic cleaning of storage reservoirs, and flushing of lines will reduce trihalomethanes formation.

Most waste sites in Zimbabwe are not sanitary landfills but open dumps that indiscriminately receive waste from municipalities, industries, commercial establishments, and social services establishments. People, including children, who eke out a living through scavenging the dumps expose themselves to environmental pollutants at the dumps via inadvertent ingestion and inhalation of contaminated dust, and dermal absorption. The public is potentially being exposed to a slew of the pollutants via air, water, and food, all contaminated by uncontrolled leachates and aerially deposited dust and particulates from the sites. One of the unfortunate consequences of globalization is the sharing of contaminated food and the associated disease burdens; hence, regional contamination can have global impacts. We analyzed the levels of lead at two waste sites in Zimbabwe to assess the daily exposure levels of Pb to children and adults who scavenge the sites as well as determine levels of the heavy metal that are potentially contaminating air, water, soils, and food in the country. Levels of Pb ranged from 23,000 to 14,600,000 µg/kg at one of the sites and from 30,000 to 1,800,000 µg/kg at the other. Inadvertent daily exposure amounts that were calculated by assuming an inadvertent daily ingestion of 20-500 mg of soil/dust were mostly higher than the provisional tolerable daily intake established by the World Health Organization for infants, children, and adults. The XRF measurements were validated using certified reference samples, 2710a (Montana soil) and 2781 (domestic sludge), from the National Institute of Standards and Technology.