Rapid incorporation and short-term distribution of a nonylphenol isomer and the herbicide MCPA in soil-derived organo-clay complexes

Organo-clay complexes in soil are a major sink for xenobiotics and, thus, often enhance their persistence dramatically. However, the knowledge on environmental processes of non-extractable residue formation on a short time scale is very restricted. Therefore, this study examined the distribution of 4-(3,5-dimethylhept-3-yl)phenol (NP) and 4-chloro-2-methylphenoxyacetic acid (MCPA) in soil over a short time period of 48 h and in different soil sub-fractions. The overall proportion of organo-clay-associated bound residues was not only abundant but also in the same range for both substances (MCPA: 8%; NP: 11% of applied ¹⁴C-radioactivity). However, a more detailed view revealed two different distribution patterns: a higher proportion of clay-associated NP was accompanied by a lower content of bound residues, whereas a smaller fraction of clay-associated MCPA was characterized by a higher proportion of non-extractable residues. Further on, a selective accumulation of bound residues among clay-associated humic fractions was observed. NP residues were linked predominantly to humic acids, whereas MCPA residues tended to be incorporated more into fulvic acids. It was evident that the overall distribution was influenced primarily by the physico-chemical properties of the contaminants. This study demonstrates in detail a rapid initial incorporation accompanied by a specific distribution into soil sub-fractions for selected xenobiotics in soil and points to a complex interaction of clay-associated organic matter with low molecular weight compounds.     

Fate of the veterinary antibiotic 14C-difloxacin in soil including simultaneous amendment of pig manure with the focus on non-extractable residues

The fate of ¹⁴C-labeled difloxacin (¹⁴C-DIF) was studied in time course experiments after application on soil (Ap horizon of silt loam) and amendment of authentic DIF containing pig manure (146 mL kg^?1; 4.17 MBq kg^?1; 0.85 mg kg^?1) or water (124 mL kg^?1; 0.42 MBq kg^?1; 0.09 mg kg^?1) for 56 and 120 days of incubation, respectively.

Mineralization of ¹⁴C-DIF was below 0.2% in both experiments after 56 days or 120 days. In the course of the experiments, portions of extractable radioactivity (Accelerated Solvent Extraction (ASE); acetonitrile-water) decreased to 19–21% depending only little on manure amendment. Non-extractable residues of ¹⁴C-DIF increased to 70–74% after 56 days and 120 days, respectively, and therefore were the main route of ¹⁴C-DIF in soil. According to radioanalytical HPLC and LC-MS/MS, only the parent compound was found in all extracts over the whole time of the experiment. According to fractionation of the non-extractable residues (NER) into particle size fractions, ¹⁴C portions were associated to the water used for fractionation, the silt and clay fractions, whereas no radioactivity was detected in the sand fraction. The majority of ¹⁴C was found within the clay fractions.

Fractionation of humic components showed that radioactivity derived from ¹⁴C-DIF was associated with humic acids, fulvic acids, humins and minerals and very little with soluble, non-humic HCl fraction. The highest portions of radioactivity were found in the fulvic acid fraction. Results obtained by size exclusion chromatography (SEC) of the purified fulvic acids were similar for every sample analyzed. One large portion of ¹⁴C co-eluted with fulvic acids of a molecular weight below 910 g mol^?1. Both fractionation methods demonstrated that the parent compound DIF or initial metabolites were rapidly integrated into humic materials and, thus, were major components of NER.     

Estimating the biogenic enhancement factor of weathering using an inverse viability method

To determine the influence of the biosphere on weathering we use a dynamic model of the global carbon cycle. It takes into account the most important processes for the long-term evolution of the Earth. The model is solved under a slowly changing environment of increasing solar luminosity and volcanic activity and continental area. By comparing the model results for the global average temperature with data derived from δ¹⁸O values from cherts it is possible to quantify the biogenic enhancement factor of weathering. For this purpose a newly developed inverse viability method is applied, which allows for calculating the range of possible biogenic enhancement factors consistent with the data. We find that in the Precambrian the weathering was 5.4 times lower than in the Phanerozoic era. This supports the hypothesis that the Cambrian explosion was caused by a positive feedback between the spread of biosphere, increased silicate weathering, and a consequent cooling of the climate.     

Das neue Chemikalienprogramm von UNEP Chemicals

The UNEP International Register of Potentially Toxic Chemicals (IRPTC) was created by the UN Conference on the Human Environment of 1972. Its influence and co-operation in the 80ies with other international programmes of the WHO, FAO, OECD, and EC for the control of chemicals is presented here. The follow-up of the UN Conference on the Environment and Development (1992) created three new bodies that are to implement chapter 19 of Agenda 21 (Environmentally Sound Management of Chemicals): The UN Commission of Sustainable Development, the International Forum on Chemical Safety, and the Interorganisation Programme for the Sound Management of Chemicals. This UN Conference also brought about a new orientation ofIIRPTC. In 1996, IRPTC was renamed as UNEP Chemicals and has been functioning in three major fields since then: The international convention on Prior Informed Consent, the international convention on the control of Persistent Organic Pollutants and, finally, a continuation of is traditional field of information exchange on chemicals.     

Poplar plantation has the potential to alter the water balance in semiarid Inner Mongolia

Poplar plantation is the most dominant broadleaf forest type in northern China. Since the mid-1990s plantation was intensified to combat desertification along China's northwestern border, i.e., within Inner Mongolia (IM). This evoked much concern regarding the ecological and environmental effects on areas that naturally grow grass or shrub vegetation. To highlight potential consequences of large-scale poplar plantations on the water budget within semiarid IM, we compared the growing season water balance (evapotranspiration (ET) and precipitation (PPT)) of a 3-yr old poplar plantation (Kp₃) and a natural shrubland (Ks) in the Kubuqi Desert in western IM, and a 6-yr old poplar plantation (Bp₆) growing under sub-humid climate near Beijing. The results showed that, despite 33% lower PPT at Kp₃, ET was 2% higher at Kp₃ (228 mm) as compared with Ks (223 mm) in May–September 2006. The difference derived mainly from higher ET at the plantation during drier periods of the growing season, which also indicated that the poplars must have partly transpired groundwater. Estimated growing season ET at Bp₆ was about 550 mm and more than 100% higher than at Kp₃. It is estimated that increases in leaf area index and net radiation at Kp₃ provide future potential for the poplars in Kubuqi to exceed the present ET and ET of the natural shrubland by 100–200%. These increases in ET are only possible through the permanent use of groundwater either directly by the trees or through increased irrigation. This may significantly change the water balance in the area (e.g., high ET at the cost of a reduction in the water table), which renders large-scale plantations a questionable tool in sustainable arid-land management.     

Partitioning behavior of polychlorinated biphenyls

Partitioning of polychlorinated biphenyls (PCBs) among several idealized environmental compartments was investigated using equilibrium conditions. Simulations with single equilibrations suggested that PCB mixtures do not weather significantly. However, simulations with multiple equilibrations of a selected phase with renewed phases suggested that PCB mixtures have the potential to weather. These simulations were strongly influenced by temperature; both the compositions and total amount of the PCBs in each phase at equilibrium changed significantly with temperature. These simulations lend support to the hypothesis that lower and higher chlorinated PCBs behave differently in the environment.     

Synthesis of branched para-nonylphenol isomers: occurrence and quantification in two commercial mixtures

Eight tertiary nonanols were synthesized via Grignard reaction and coupled by Friedel–Crafts alkylation with phenol to the corresponding nonylphenols. Six branched para-nonylphenols (NP) were obtained: 4-(3′-methyl-3′-octyl)phenol (33NP), 4-(2′-methyl-2′-octyl)phenol (22NP), 4-(2′,5′-dimethyl-2′-heptyl)phenol (252NP), 4-(2′,5′,5′-trimethyl-2′-hexyl)phenol (2552NP), 4-(2′,4′-dimethyl-2′-heptyl)phenol (242NP) and 4-(4′-ethyl-2′-methyl-2′-hexyl)phenol (4E22NP). Their structures were confirmed by GC–MS and NMR spectroscopy. These six isomers as well as the earlier synthesized 4-(3′,5′-dimethyl-3′-heptyl)phenol (353NP), 4-(3′,6′-dimethyl-3′-heptyl)phenol (363NP) and 4-(2′,6′-dimethyl-2′-heptyl)phenol (262NP) were compared with commercial NP mixtures purchased from Acros and Fluka by GC–MS (equipped with a 100 m polysiloxane column). The analyses revealed that all obtained isomers are occurring in different quantities in both commercial NP mixtures.