A new simple index for characterizing the labile heavy metal concentration in soil by diffusive gradients in thin films technique.

Diffusive gradients in thin films technique (DGT) is recognized as a more reliable method for determining labile heavy metal (HM) concentration in soil than traditional destructive methods. However, the current DGT measurement index, CDGT, theoretically underestimates the true labile concentration (Clabile) of HMs in soil and lacks direct comparability with the conventional soil HM content indices due to unit differences. Here, we proposed CDGT-W, a new simple index which is defined as the HM accumulation in the binding layer, normalized to the weight of soil (optimized water content = 100% of the maximum water holding capacity) filled in the open cavity-type DGT device over a specified deployment time (optimized time = 24 h). The procedure for measuring CDGT-W is analogous to that of CDGT but includes precise determination of water content (water/dry soil) and the mass of soil filled in the cavity. We conducted measurements of Cu, Pb, Cr(Ⅵ) and As(V) as CDGT-W, CDGT, solution concentration (Csoln), and CaCl2 extractable concentration (CCaCl2) on three soils with a diverse range of HM concentrations. CDGT-W showed significant linear correlations with all other tested indexes. The ratios of CDGT-W to CCaCl2 varied between 0.30 and 0.98 for all HM-soil combinations with only one exception, a range much greater than CDGT/Csoln (typically <0.1) but lower than 1. This suggested that CDGT-W may more accurately reflect Clabile than CDGT (theoretically underestimates Cliable) and CCaCl2(likely overestimates Cliable). Additionally, CDGT-W measurements for these four HMs exhibited a broad measure concentration range and a low detection limit (mg/kg level). Consequently, CDGT-W may offer a more reliable alternative to CDGT for characterizing Clabile in unsaturated soils.

Structural characterization and immune activity evaluation of a polysaccharide from Lyophyllum Decastes.

An innovative acidic hydrolysate fingerprinting workflow was proposed for the characterization of Lyophyllum Decastes polysaccharide (LDP) by ultra performance liquid chromatography-mass spectrometry (UPLC-MS). The crude polysaccharides were firstly separated and purified by using DE-52 column and the BRT GPC purification system, respectively. The molecular weight and monosaccharide content of homogeneous polysaccharides were ascertained by utilizing HPGPC and ion chromatography separately. Secondly, the linkage of LDP was identified by methylation analysis and 1D/2D NMR spectra. The UPLC-MS/MS was used to scan and identify the acidic hydrolysate products of LDP using the PGC column. The oligosaccharides were collected by chromatography and identified by mass spectrometry. Thirdly, the expression of IL-1ß, IL-6, iNOS, TNF-α and IFNAR-I was measured in order to assess the immunological activity of LDP. Besides, the targeted receptors identification of polysaccharides was performed by screening the expression of TLRs family protein. The results showed that oligosaccharide fragments with different molecular weights can be obtained by partial hydrolysis, which further verified that the structures of LDP polysaccharides was a 1-6-linked ß-glucan. Moreover, the LDP polysaccharide can up-regulate the content of IL-1ß, IL-6, iNOS, TNF-α and IFNAR-I and plays an important immunoregulation role through TLRs family.