Aerobic biodegradation of polyethylene glycols of different molecular weights in wastewater and seawater.

In order to distinguish between aerobic biodegradation of synthetic polymers in fresh and seawater, polyethylene glycols (PEGs) were systematically and comparatively investigated in inocula from municipal wastewater and seawater aquarium filters for the first time. The molecular weight (MW) of the PEGs, (HO(CH(2)CH(2)O)(n)H, n=3-1350) as representatives of water-soluble polymers, ranged from 250 to 57,800Da. The biodegradation was observed by removal of dissolved organic carbon and carbon dioxide production by applying standardized ISO and OECD test methods. Specific analyses using liquid chromatography mass spectrometry (LC-MS) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) were performed. All PEGs selected were completely biodegradable in freshwater media within 65d. PEGs with an MW up to 14,600Da have a similar degradation pathway which is characterized by gradual splitting of C(2)-units off the chain resulting in formation of short-chain PEGs. In artificial seawater media, full biodegradation of PEGs up to 7400Da required more time than in freshwater. PEGs with MW 10,300 and 14,600Da were only partially degraded whereas PEGs with MW 26,600 and 57,800Da were not degraded for a period of 135d. The biodegradation pathway of PEG 250 and PEG 970 in seawater is similar to that for freshwater. For PEGs having an MW from 2000 to 10,300Da, the degradation pathway in seawater differs from the pathway of the shorter PEGs.

Occurrence and fate of barbiturates in the aquatic environment.

Barbiturates have been widely used as sedative hypnotics in the mid-1960s and since then mainly as veterinary drugs. To monitor their presence and fate in the aquatic environment, a method based on gas chromatography-mass spectrometry (GC-MS) has been developed to quantify butalbital, secobarbital, hexobarbital, aprobarbital, phenobarbital, and pentobarbital, all with a limit of detection (LOD) down to 1 ng/L. From the various investigated waste and surface water samples, barbiturates were only, but regularly detected in the Mulde, a tributary of the river Elbe in Germany at relevant concentrations up to several microg/L. Investigations of groundwater being affected with wastewater infiltration several decades ago also revealed a barbiturate pattern, indicating a strong recalcitrance of these drugs. To confirm this hypothesis, studies were carried out on biotic and abiotic degradation. Both, the biodegradability under aerobic conditions and hydrolysis did not show any degradation, implementing, that the investigated barbiturates, once released into the aquatic environment, show high stability over a long period of time.

Phosphorus composition of sheep feces and changes in the field determined by 31P NMR spectroscopy and XRPD.

Information on the P species in sheep feces is lacking. Such information is required to understand P-cycling in grazed ecosystems. The P composition of feces from sheep grazing grass in Scotland was assessed on freeze-dried samples by 31P MAS (magic angle spinning) NMR (nuclear magnetic resonance) spectroscopy and XRPD (X-ray powder diffraction). The 31P MAS NMR spectrum showed resonances and sidebands consistent with dicalcium phosphate dihydrate (brushite) and ammonium magnesium phosphate hexahydrate (struvite). XRPD confirmed the result and allowed quantification of these minerals, which accounted for 63% of the P. To determine transformations in the field, sheep feces were collected and reapplied to sheep-free pasture in synthetic patches during late summer. The dry weight decreased with time and the feces disappeared between 84 and 112 days following heavy rainfall. The concentration of P in the feces recovered at intervals up to 84 days changed little with time but the contribution from brushite and struvite decreased and within 1 week <50% remained indicating conversion into other forms. Solution-phase 31P NMR spectra of NaOH/EDTA extracts of the feces were dominated by the inorganic orthophosphate with minor amounts of organic P that were attributed to phosphate esters and polyphosphates.