A GC×GC-ToFMS Investigation of the Unresolved Complex Mixture and Associated Biomarkers in Biodegraded Petroleum

Heavy biodegraded crude oils have larger numbers of coeluting compounds than nonbiodegraded oils, and they are typically not resolved with conventional gas chromatography（GC）. This unresolved complex mixture（UCM） has been investigated using comprehensive two-dimensional gas chromatography–time-of-flight mass spectrometry（GC×GC-To FMS） within a set of biodegraded petroleums derived from distinct sedimentary basins, including northwestern Sichuan（Neoproterozoic, marine）, Tarim（Early Paleozoic, marine）, Bohai Bay（Eocene, saline/brackish） and Pearl River Mouth（Eocene, freshwater）. In general, the hydrocarbons that constitute the UCM in petroleum saturate fractions can be classified into three catalogues based on the distributions of resolved compounds on two dimensional chromatograms. Group 1 is composed mainly of normal and branched alkanes, isoprenoid alkanes and monocyclic alkanes; Group 2 comprises primarily terpanes ranging from two to five rings, and Group 3 is dominated by monoaromatic hydrocarbons such as tetralins and monoaromatic steranes. In addition, the UCM is source dependent and varies between oil populations. i.e., the UCM of petroleum derived from Precambrian and Early Paleozoic marine, Eocene saline/brackish and freshwater source rocks is specifically rich in higher homologues of A-norsteranes, series of 1,1,3-trimethyl-2-alkylcyclohexanes（carotenoid-derived alkanes）, and tetralin and indane compounds, respectively.

Comprehensive monitoring of chlorinated aromatic and heteroaromatic pollutants at sites contaminated by chlorine production processes to inform policy making

The production of chlorine by the chlor-alkali process using graphite electrodes was one of the largest sources of polychlorinated dibenzo-p-dioxins and dibenzofurans(PCDD/PCDFs)in history with estimates in the kg TEQ range for individual factories.In addition,the chlorine production predecessor processes in the former Leblanc soda factories generated large amounts of PCDD/PCDFs,also in kg TEQ range for individual sites.In both processes coal tar,used as pitch binder for electrodes in the chlor-alkali process or tars for sealing chlorine chambers,was the major source for PCDD/PCDFs formation.The complex PAH mixture in the tars which were chlorinated in the processes contained approx.1%dibenzofuran.Therefore in this study we screened the full range of chlorinated aromatic and heteroaromatic compounds in contaminated soils from former chlor-alkali plants in Germany and Japan as well as from a German Leblanc factory,using high resolution time-of-flight mass spectrometry GC-HR-TOF-MS.At all three sites the full range of unintentionally produced persistent organic pollutants(POPs)listed in the Stockholm Convention(PCDFs,PCDDs,PCBs,PCNs,HCB,HCBD and PeCBz)were present at high ppb levels and TEQ was up to several 100,000 ng/kg soil in hot spot areas.Additionally,a wide range of other polychlorinated(PC-)PAHs(PC-phenanthrene/anthracene,PC-pyrene/fluoranthene,PC-benzo(a)anthracene/chrysene)were detected.Some of these compound classes were present in one to two order of magnitude higher concentrations compared to PCDFs.Furthermore,polychlorinated methyldibenzofurans,polychlorinated dimethyl-/ethyl-dibenzofurans,and polychlorinated carbazoles e the N-analogue of dibenzofuran-were detected at levels comparable to PCDFs at all three sites.Polychlorinated benzonitriles were detected in addition to chlorobenzenes as monoaromatic pollutant.Since all three factories have stopped production 50e120 years ago,all detected chlorinated aromatics can be regarded as very persistent.The technologies have been used in several hundred locations globally.These(former)chlorine production sites should be assessed for contamination and their contemporary threat to humans and the environment should be evaluated.The toxicity of most of these polychlorinated PAHs and hetero-PAHs is unknown but due to their related structures,similar toxicity profiles can be expected and need to be investigated.Furthermore,all processes where chlorine and complex organic material are present should be screened for the entire resulting chlorinated pollutant mixture,the detailed fingerprints should be documented,and the overall toxicological risk assessed for individual processes to inform policy making.

Study on triaxial test method and failure criterion of asphalt mixture

Asphalt mixture is the most widely used pavement material all over the world. In China, more than 90% of service expressways are asphalt pavement. However, current asphalt pavement design method still has irrationality. Even though maximum tensile stress theory is used as failure criterion, pavement structure under the effects of wheel load is in three-dimensional complex stress state. Obviously, one-dimensional strength theory cannot reflect the failure characteristics and the resistance of pavement structure. So it is necessary to study the failure criterion of asphalt mixture under three-dimensional com- plex stress state. Due to limitations of test equipment, there are almost no studies in related area. Under this background, this paper develops a new triaxial test method, ac- cording to the investigation of strength characteristics of asphalt mixture under complex stress state through plane isobaric/axial tensile test, plane isobaric/axial compression test, plane tensile and compression/axial tensile test, to reveal the general rules of asphalt mixture＇s strength failure. The failure mode is divided into three types： tensile failure, shear failure and rheological failure. The tensile meridian and compression meridian in the stress space and strength envelope in the π plane where hydrostatic pressure is greater than zero are obtained, and the failure criterion of asphalt mixture under complex stress state is established, providing theoretical method and scientific basis for structure design as well as strength check of asphalt pavement under three-dimensional stress state.