RESUMEN
We quantified pesticide contamination and its ecological impact up- and downstream of seven wastewater treatment plants (WWTPs) in rural and suburban areas of central Germany. During two sampling campaigns, time-weighted average pesticide concentrations (cTWA) were obtained using Chemcatcher® passive samplers; pesticide peak concentrations were quantified with event-driven samplers. At downstream sites, receiving waters were additionally grab sampled for five selected pharmaceuticals. Ecological effects on macroinvertebrate structure and ecosystem function were assessed using the biological indicator system SPEARpesticides (SPEcies At Risk) and leaf litter breakdown rates, respectively. WWTP effluents substantially increased insecticide and fungicide concentrations in receiving waters; in many cases, treated wastewater was the exclusive source for the neonicotinoid insecticides acetamiprid and imidacloprid in the investigated streams. During the ten weeks of the investigation, five out of the seven WWTPs increased in-stream pesticide toxicity by a factor of three. As a consequence, at downstream sites, SPEAR values and leaf litter degradation rates were reduced by 40% and 53%, respectively. The reduced leaf litter breakdown was related to changes in the macroinvertebrate communities described by SPEARpesticides and not to altered microbial activity. Neonicotinoids showed the highest ecological relevance for the composition of invertebrate communities, occasionally exceeding the Regulatory Acceptable Concentrations (RACs). In general, considerable ecological effects of insecticides were observed above and below regulatory thresholds. Fungicides, herbicides and pharmaceuticals contributed only marginally to acute toxicity. We conclude that pesticide retention of WWTPs needs to be improved.
Asunto(s)
Monitoreo del Ambiente , Invertebrados/efectos de los fármacos , Plaguicidas/análisis , Eliminación de Residuos Líquidos , Contaminantes Químicos del Agua/análisis , Animales , Ecosistema , Alemania , Neonicotinoides/análisis , Ríos , Aguas Residuales/análisisRESUMEN
Thiolysis of the model diazeniumdiolate prodrug, O2-(2,4-dinitrophenyl) 1-(N,N-diethylamino)diazen-1-ium-1,2-diolate (DNP-DEA/NO), by glutathione (GSH), cysteine (CYSH) and 1-heptanethiol (heptylmercaptan, HM) has been examined in anionic (DOPG), neutral (DPPC, DOPE) and cationic (DOTAP) vesicle media and in glycine buffered aqueous solutions. DOTAP vesicles accelerate the bimolecular reaction with glutathione, cysteine and 1-heptanethiol by factors of 81, 8.2 and 4630, respectively, while reaction is inhibited 5- to 10-fold in the presence of neutral and anionic vesicles. The intrinsic nucleophilicity of the thiols has been compared through the second-order rate constants, 22.9, 5.24 and 43.1M(-1)s(-1), for nucleophilic attack on 1 by GS(-), CYS(-) and M(-), respectively, obtained in buffered aqueous media. Analysis of the catalysis by DOTAP vesicles, using pseudophase ion-exchange formalism, suggests that the rate increase is due to reactant concentration in the bilayer and interfacial region coupled with enhanced dissociation of the thiol at the vesicle surface. Some contribution from enhanced nucleophilic reactivity at the vesicle interface may also contribute to the greater catalysis by HM. Inhibition of the thiolysis reaction by phospholipid liposomes is attributed to repulsion of the thiolate anions by the negatively charged acyl phosphate of the lipid head group. DOPG=1,2-dioleoyl-sn-glycero-3-[phospho-rac-(1-glycerol)], DPPC=1,2-dipalmitoyl-sn-glycero-3-phosphocholine, DOPE=1,2-dioleoyl-sn-glycero-3-phosphoethanolamine, DOTAP=1,2-dioleoyl-3-trimethylammonium-propane.
Asunto(s)
Compuestos Azo/química , Profármacos/química , Compuestos de Sulfhidrilo/química , Compuestos Azo/síntesis química , Tampones (Química) , Cisteína/química , Ácidos Grasos Monoinsaturados/química , Glutatión/metabolismo , Glutatión/farmacocinética , Concentración de Iones de Hidrógeno , Liposomas/química , Donantes de Óxido Nítrico/síntesis química , Donantes de Óxido Nítrico/química , Compuestos de Amonio Cuaternario/química , Espectrofotometría UltravioletaRESUMEN
In this laboratory study, we address the effect of Chironomus bioturbation (0, 2,000, 6,000, and 18,000 ind/m2) and sediment organic matter content (10, 20, and 40%) on the fate, distribution, and bioavailability of 14C-lindane under standardized conditions in toxicity tests with artificial sediment. The results show that both Chironomus burrowing activity and sediment organic matter strongly modify test conditions. Larval mortality and development were inversely related with Chironomus densities and lindane concentration. Sediment organic matter content affected larval development rates but not mortality. Partitioning of lindane between the sediment, overlying water, and interstitial water was affected negatively by Chironomus larval densities: however, sediment partitioning was positively affected by sediment organic matter content. Bioturbation by Chironomus resulted in a remobilization of particle-associated lindane to the interstitial and overlying water, implying an increase in the bioavailability of the test compound. Strong positive relationships were found between Chironomus densities and lindane concentrations in interstitial water. The presence of Chironomus also resulted in lower label recovery. Label recovery on sediment particles ranged from 49 to 61% of initially added label in microcosms without Chironomus, from 41 to 56% at low larval densities, and from 15 to 50% at high larval densities. These results show that large discrepancies may exist between nominal test concentrations (from test compound additions) and true exposure concentrations even under standardized test conditions, which can introduce a relatively large error term in risk assessments. Calculations show that volatilization may be a quantitatively important sink for test compounds.