Adsorption by minerals is a common geochemical process of dissolved organic matter (DOM) which may induce fractionation of DOM at the mineral-water interface. Here, we examine the molecular fractionation of DOM induced by adsorption onto three common iron oxyhydroxides using electrospray ionization coupled with Fouriertransform ion cyclotron resonance mass spectrometry (ESI-FT-ICR-MS). Ferrihydrite exhibited higher affinity to DOM and induced more pronounced molecular fractionation of DOM than did goethite or lepidocrocite. High molecular weight (>500 Da) compounds and compounds high in unsaturation or rich in oxygen including polycyclic aromatics, polyphenols and carboxylic compounds had higher affinity to iron oxyhydroxides and especially to ferrihydrite. Low molecular weight compounds and compounds low in unsaturation or containing few oxygenated groups (mainly alcohols and ethers) were preferentially maintained in solution. This study confirms that the double bond equivalence and the number of oxygen atoms are valuable parameters indicating the selective fractionation of DOM at mineral and water interfaces. The results of this study provide important information for further understanding the behavior of DOM in the natural environment.

Chronic neuroinflammation is a common feature of the ageing brain and some neurodegenerative disorders. However, the molecular and cellular mechanisms underlying the regulation of innate immunity in the central nervous system remain elusive. Here we show that the astrocytic dopamine D2 receptor (DRD2) modulates innate immunity through αB-crystallin (CRYAB), which is known to suppress neuroinflammation. We demonstrate that knockout mice lacking Drd2 showed remarkable inflammatory response in multiple central nervous system regions and increased the vulnerability of nigral dopaminergic neurons to neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced neurotoxicity. Astrocytes null for Drd2 became hyper-responsive to immune stimuli with a marked reduction in the level of CRYAB. Preferential ablation of Drd2 in astrocytes robustly activated astrocytes in the substantia nigra. Gain- or loss-of-function studies showed that CRYAB is critical for DRD2-mediated modulation of innate immune response in astrocytes. Furthermore, treatment of wild-type mice with the selective DRD2 agonist quinpirole increased resistance of the nigral dopaminergic neurons to MPTP through partial suppression of inflammation. Our study indicates that astrocytic DRD2 activation normally suppresses neuroinflammation in the central nervous system through a CRYAB-dependent mechanism, and provides a new strategy for targeting the astrocyte-mediated innate immune response in the central nervous system during ageing and disease.

a b s t r a c tIt is important to understand the status and extent of soil contamination with trace elements to make sustainable management strategies for agricultural soils. The inputs of trace elements to agricultural soils via atmospheric deposition, livestock manures, fertilizers and agrochemicals, sewage irrigation and sewage sludge in China were analyzed and an annual inventory of trace element inputs was developed. The results showed that atmospheric deposition was responsible for 43-85% of the total As, Cr, Hg, Ni and Pb inputs, while livestock manures accounted for approximately 55%, 69% and 51% of the total Cd, Cu and Zn inputs, respectively. Among the elements concerned, Cd was a top priority in agricultural soils in China, with an average input rate of 0.004 mg/kg/yr in the plough layer (0-20 cm). Due to the spatial and temporal heterogeneity of the sources, the inventory as well as the environmental risks of trace elements in soils varies on a regional scale. For example, sewage sludge and fertilizers (mainly organic and phosphate-based inorganic fertilizers) can also be the predominant sources of trace elements where these materials were excessively applied. This work provides baseline information to develop policies to control and reduce toxic element inputs to and accumulation in agricultural soils.