SUMMARY1. The regulation and management of chemical contaminants rarely use community-and ecosystemlevel endpoints, partly due to a lack of suitable methods. To overcome this limitation, we propose contaminant exposure substrata (CES), an adaptation of the widely used nutrient-diffusing substratum method, to assess responses of biofilm communities to chemical contaminants in situ. 2. We describe methods for using CES to assess effects on biofilm biomass, community structure, process rates, biofilm-consumer interactions and biofilm chemistry. We also provide equations to calculate the flux of soluble chemicals from CES and describe an approach to compare contaminant dose in CES assays to the contaminant dose encountered by biofilms in polluted surface waters. 3. Data from four case studies demonstrate that CES can detect impairment of biofilm structure and function. 4. The adaptability, simplicity and cost-effectiveness of CES make them valuable tools to assess community-and ecosystem-level responses to contaminants, suggesting potential for routine use and incorporation of data generated from such assays into contaminant regulation and management.
Environmental context Pharmaceuticals and personal care products are routinely found in waters discharged from treatment plants and in surrounding aquatic ecosystems. Despite the widespread occurrence of these biologically active agents, there is limited understanding of their potential effects on key ecosystem processes such as primary production, ecosystem respiration and algal growth. This paper examines the effects of five common pharmaceuticals on the rates of these fundamental processes. Abstract Pharmaceutical diffusing substrates were used to study in situ responses of aquatic biofilms in an urbanised lentic ecosystem to five pharmaceutical and personal care products (PPCPs; caffeine, cimetidine, ciprofloxacin, diphenhydramine and metformin). The pharmaceutical diffusing substrates consisted of porous biofilm substrates placed atop a mass of agar amended with 2.5mM of the PPCP compound of interest. Over 21 days, biofilms growing on the substrata were exposed to slow diffusion of the PPCP through the agar and porous substrate. Algal biomass was suppressed by exposure to diphenhydramine (–81%) and ciprofloxacin (–50%). Gross primary production was completely suppressed by diphenhydramine exposure but stimulated by caffeine (+39%) and cimetidine (+46%). For heterotroph biofilms, community respiration was suppressed by exposure to diphenhydramine (–24%). To characterise PPCP exposure, rates of diffusion from the pharmaceutical diffusing substrates were measured at 10, 20 and 30°C. Diffusion was Fickian for all compounds and all temperatures. Diffusion coefficients, D, were in the range 1.5×10–10 to 1.1×10–9m2s–1. From diffusion data, average release rates over 21 days were typically 30–50ngmin–1cm–2 at 20°C. The results show that PPCPs can dramatically affect rates of key ecological processes, and the relationship between release rate and ambient concentration of PPCPs is discussed.
Patent literature is an important source of chemical information that is often neglected by chemical educators. This paper describes an effort to teach chemistry students how to use patent databases to search for information on applied chemical technology related to the manufacture of industrial and specialty chemicals. Students in a second-year-level organic chemistry class were shown how to search patent literature as part of a group research paper assignment that involved determining the feasibility of starting an industrial chemical operation to manufacture a given industrial chemical. Students who were assigned high value or specialty chemicals were most likely to cite patent literature in their final papers. Students who were assigned plastics or bulk commodity chemicals were less likely to cite patents. It is suggested that students made choices about the usefulness of patent literature and that patents were most useful when current patents existed and provided the patent owner a competitive advantage. For plastics or commodity chemicals, manufacturing technologies tend to be mature and are well described by more accessible information sources. Suggestions are made for effective introduction of patent literature instruction into upper-level chemistry courses.
Final effluent from a pulp and paper kraft mill was exposed to power ultrasound at 357kHz with the aim of reducing color, turbidity, and chemical oxygen demand (COD). Absorbance measurements showed a bleaching of the effluent at wavelengths above 250nm, indicating loss of aromatic chromophores. Effluent turbidity also decreased. Surprisingly, there was no observable decrease in COD, within experimental error. This is attributed to the presence of bicarbonate and sulfate ions in the final effluent, which react with hydroxyl radicals and effectively block the oxidation of organics in the effluent. This was demonstrated by sonicating solutions of potassium hydrogen phthalate (KHP) containing chloride, bicarbonate, or sulfate ions, which are the major inorganic ions in the final effluent studied. A solution containing only 2.3mM KHP showed a 19% reduction in COD after 6h of sonication. An identical solution with 200ppm chloride also showed a 19% COD reduction. However, solutions with 700ppm sulfate and 400ppm bicarbonate showed COD reductions of 11% and 3%, respectively.
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