Effect of amendments on soil Cd sorption and trophic transfer of Cd and mineral nutrition along the food chain.

Phytotoxicity of cadmium (Cd) and its trophic transfer along a terrestrial food chain have been extensively investigated. However, few studies focused on the role of amendments on the trophic transfer of Cd and related mineral nutrients. In a 60-day pot experiment, soil Cd availability, accumulation of Cd, mineral nutrients (Ca and Si) in lettuce, and subsequent trophic transfer along the lettuce-snail system were investigated with or without 3% (w/w) soil amendment (biochar or micro-hydroxyapatite, µHAP). Soil CaCl2 extractable Cd (CdCaCl2) contents decreased by both amendments. µHAP amended soil increased the Freundlich sorption capacity of Cd2+ to a greater extent (15.9 mmol/kg) than biochar (12.6 mmol/kg). Cd, Ca and Si accumulation in lettuce tissues (roots and shoots) varied with amendment species and soil Cd levels. Linear regression analysis showed that root Cd contents are negatively correlated with root Ca and Si contents (r2 = 0.96, p < 0.05). But no significant correlation between shoot Cd and lettuce Ca and Si contents was found (p > 0.05). After 15 days snail feeding, nearly 90% content of Cd was found in snail viscera, while nearly 95% content of Ca was found in snail shells. Contents of Si distributed equally in snail tissues. Biomagnification of Cd, Ca and Si (TF > 1) was found in lettuce shoot - snail viscera system. Opposite tendency of TF variation between Cd and nutrient elements (Ca and Si) from shoots to snail tissues indicated that µHAP, rather than biochar, amendment is applicable to remediate soil Cd contamination in our study.

Effects of soil amendments on cadmium transfer along the lettuce-snail food chain: Influence of chemical speciation.

Cadmium (Cd) trophic transfer along the soil-lettuce-snail food chain was investigated using the root bags-based pot experiments. Two amendments (corn straw biochar and micro-hydroxyapatite (µHAP)) were investigated on Cd (0, 2.5, and 5 mg/kg soil) availability in soils, chemical distribution in plant cells and accumulation in snails. After 60 days, both the CaCl2 extractable Cd in rhizosphere soil (CdCaCl2,rhizo) and Cd accumulation in lettuce decreased with amendments addition. Biochar had a great capacity to reduce both Cd contents and toxicity-sensitive associated Cd (CdFi+Fii) percentages in lettuce roots at 2.5 mg/kg Cd contaminated soil; while µHAP generates a higher reduction in both Cd contents and chain transfer associated Cd (CdFi+Fii+Fiii) percentages in lettuce shoots at 5 mg/kg Cd contaminated soil. Linear regression showed that both contents of root CdFi+Fii and shoot CdFi+Fii+Fiii are better correlated with the CdCaCl2,rhizo (R2 > 0.70, p < 0.01). After 15 days feeding, almost 90% content of Cd accumulated in snail viscera. µHAP had a higher reduction in snail soft tissues Cd accumulation than biochar. Distributions of Cd in snail tissues are significantly correlated with CdFi+Fii+Fiii in shoots (viscera R2 = 0.835; soft tissue R2 = 0.771). Established quantitative relationships could be used to predict the bioavailability and transfer of Cd in terrestrial food chain in the presence of amendments.

[Spatial Distributions of Transferable Nitrogen Forms and Influencing Factors in Sediments from Inflow Rivers in Different Lake Basins].

It is necessary to investigate the distribution of nitrogen forms in river sediments to recognize the water environment quality. In this study, ion exchangeable form nitrogen(IEF-N), weak acid extractable form nitrogen (WAEF-N), strong alkali extractable form nitrogen (SAEF-N) and strong oxidation extractable form nitrogen (SOEF-N) in sediments were obtained by means of sequential extraction procedures.We analyzed the spatial variations of nitrogen forms in sediments from Taihu watershed (Dongtiaoxi River and Xitiaoxi River) and Hongzehu watershed (Anhe River and Suihe River), and expounded the influence factors of nitrogen form distribution. The results showed that the physicochemical properties of sediments from different watersheds varied in space. The concentrations of total nitrogen and nitrogen fractions also showed obvious changes in river sediments. As a whole, the concentrations of total nitrogen and transferable nitrogen in Taihu rivers were higher than those in Hongzehu rivers, but the former showed smaller spatial changes. Sediments from Taihu rivers showed the different concentration order of total nitrogen and transferable nitrogen comparing with those from Hongzehu rivers. The former followed the order of SOEF-N > SAEF-N > IEF-N > WAEF-N, and the latter followed the order of SOEF-N > SAEF-N > WAEF-N > IEF-N.The spatial varitions of transferable nitrogen fractions in Hongzehu rivers were prominent, which was associated with nitrogen sources. The spatial distributions of transferable nitrogen in sediments were obviously affected by their physicochemical properties, especially for organic matter and grain size.

Targeting the RhoA-ROCK pathway to regulate T-cell homeostasis in hypoxia-induced pulmonary arterial hypertension.

BACKGROUND: Hypoxic pulmonary arterial hypertension (PAH) is a crippling disease with limited therapeutic methods. The imbalance of T helper 17 cell (Th17)/regulatory T cell (Treg) plays an important role in the development of Hypoxic PAH. However, whether targeting the ras homolog family member A-Rho kinase (RhoA-ROCK) pathway (activation and inhibition) by lysophosphatidic acid (LPA) and fasudil (FSD) regulate T-cell homeostasis in Hypoxic PAH remain unknown. OBJECTIVE: To examine the effects of LPA and FSD on hypoxic pulmonary vascular remodeling and homeostasis of Th17/Treg cells in Hypoxic PAH. METHODS: Rats were exposed to hypoxia (10 ±â€¯0.5% O2) to induce Hypoxic PAH. The experiments consists of two parts. Forty rats were randomly divided into four groups (n = 10): normoxia group, normoxia + LPA group, hypoxia group and hypoxia + LPA group. Thirty rats were randomly divided into another three groups (n = 10): normoxia group, hypoxia group, and hypoxia + FSD group. Rats in normoxia + LPA group and hypoxia + LPA group were intraperitoneally injected 40 µg/kg LPA daily. Rats in hypoxia + FSD group were intraperitoneally injected 30 mg/kg fasudil daily. The effects of LPA and FSD on the development of hypoxic PAH and right ventricle (RV) hypertrophy, on pulmonary vascular remodeling, and on changes of Th17/Treg cells and levels of interleukin-17 (IL-17) and IL-10 were examined. RESULTS: PAH and RV hypertrophy occurred in rats exposed to hypoxia. LPA exacerbated hypoxic pulmonary vascular remodeling and FSD inhibited it. LPA increased Th17/Treg imbalance in peripheral blood and spleen. However, after treatment with FSD, hypoxic PAH rats showed an obvious reduction of Th17 cells as well as an increase of Treg cells. LPA increased the expression of phosphorylated-signal transducer and activator of transcription 3 (p-STAT3) and reduced the p-STAT5 in peripheral blood and spleen in hypoxic PAH rats. The expression of p-STAT3 and p-STAT5 in hypoxic PAH rats treated with FSD showed opposite changes. LPA increased the expression of IL-17 and reduced the IL-10 in small intrapulmonary arteries and serum in hypoxic PAH. However, the expression of IL-17 and IL-10 in hypoxic PAH rats treated with FSD showed opposite changes. CONCLUSIONS: Activation and inhibition of RhoA-ROCK pathway by LPA and FSD modulated the homeostasis of Th17/Treg cells via regulating STAT3/STAT5 phosphorylation in hypoxic PAH. Thus, Apart from influence of pulmonary vascular remodeling, regulation of Th17/Treg homeostasis by RhoA-ROCK pathway play a key role in hypoxic PAH.