ABSTRACT
To reveal the hydrochemical characteristics of karst wetland located in a subtropical area and at lower elevations in China, 27 surface water samples were collected during three periods (wet, normal, and dry) in the Huixian karst wetland to investigate the distributions, pollution, and irrigation application of 12 inorganic ions and 10 heavy metals. Based on their concentrations, the Nemerow index and the four evaluation systems of the sodium adsorption ratio (SAR), sodium concentration (SC), permeability index (PI), and residual sodium carbonate (RSC) were applied to evaluate the pollution characteristics and irrigation application. It was found that the water type in this area was Ca2+-HCO3- and weakly alkaline. Regarding the 12 inorganic ions and 10 heavy metals, NH4+ exceeded the Chinese standards for drinking water with an exceedance rate of 25.93%, and the exceedance rates of Al, Mn, and Hg were 11.11%, 44.44%, and 37.04%, respectively. The spatiotemporal scaling effect on inorganic ions was lower than that of heavy metals, and the distributions of the inorganic ions and heavy metals were in the order of wet period > normal period > dry period. However, the surface water quality in the Huixian karst wetland was generally well-protected based on the pollution assessment. The Nemerow index ranged from 0.75 to 2.69, which recognized the main pollution contributors as NH4+, Mn, Al, and Hg with the contamination grade from slight pollution to moderate pollution, especially in the core area during the wet period. According to the limits of standards for irrigation water quality and environmental quality for surface water, as well as the evaluation results of the SAR, SC, PI, and RSC, the surface water in the Huixian karst wetland was generally suitable for irrigation, and the water quality in the dry period was better than that in the wet and normal periods. The surface water from site PH1 during the normal period with 19.1 µg·L-1 of Hg and site FH8 during the wet period with 13.7 mg·L-1 of NH4+ were not suitable for agricultural irrigation.
ABSTRACT
Low molecular weight seleno-aminopolysaccharide (LSA) is an organic selenium compound comprising selenium and low molecular weight aminopolysaccharide (LA), a low molecular weight natural linear polysaccharide derived from chitosan. LSA has been found to exert strong pharmacological activity. In this study, we aimed to investigate the protective effect of LSA on intestinal mucosal oxidative stress in a weaning piglet model by detecting the growth performance, intestinal mucosal structure, antioxidant indices, and expression level of intracellular transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) and its related factors. Our results indicated that LSA significantly increased the average daily gain and feed/gain (p < 0.05), suggesting that LSA can effectively promote the growth of weaning piglets. The results of scanning electron microscope (SEM) microscopy showed that LSA effectively reduced intestinal damage, indicating that LSA improved the intestinal stress response and protected the intestinal structure integrity. In addition, diamine oxidase (DAO) and d-lactic acid (d-LA) levels remarkably decreased in LSA group compared with control group (p < 0.05), suggesting that LSA alleviated the damage and permeability of weaning piglets. LSA significantly increased superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), and total antioxidant capacity (T-AOC) levels, but decreased malondialdehyde (MDA) level, indicating that LSA significantly enhanced the antioxidant capacity and reduced oxidative stress in weaning piglets. RT-PCR results showed that LSA significantly increased GSH-Px1, GSH-Px2, SOD-1, SOD-2, CAT, Nrf2, HO-1, and NQO1 gene expression (p < 0.05). Western blot analysis revealed that LSA activated the Nrf2 signaling pathway by downregulating the expression of Keap1 and upregulating the expression of Nrf2 to protect intestinal mucosa against oxidative stress. Collectively, LSA reduced intestinal mucosal damage induced by oxidative stress via Nrf2-Keap1 pathway in weaning stress of infants.
