Comparative study on different sediment transport capacity based on dimensionless flow intensity index

Journal of Soils and Sediments - Sediment transport plays a vital role in the development of soil erosion process models. The primary purpose of this study is to establish new sediment transport...     

岩溶湿地和稻田的土壤酶活性与CO2和CH4排放特征

【目的】探究土地利用变化对湿地土壤酶活性和温室气体排放之间关系的影响。【方法】以会仙岩溶湿地为研究样点,以湖泊湿地和其相邻的稻田为研究对象,采用比色法和静态暗箱法分别测定水稻整个生育期内主要土壤酶的活性及CO₂和CH₄的排放,并对二者之间的关系进行分析。【结果】稻田土壤的β-葡萄糖苷酶、纤维素酶、蔗糖酶、几丁质酶、脲酶和碱性磷酸酶活性均高于湖泊湿地,高出幅度为11.8%—32.7%。稻田CO₂和CH₄排放通量分别为255.9—789.7和-0.41—1.74 mg·m^-2·h^-1,平均值分别为445.8和0.42 mg·m^-2·h^-1,低于天然湖泊湿地。与湖泊湿地相比,稻田CO₂和CH₄排放总量分别降低了22.3%和83.3%,而增温潜势（GHGs,含N₂O）降低了29.6%。相关性结果显示,CO₂排放通量与β-葡萄糖苷酶、纤维素酶、蔗糖酶和几丁质酶活性呈显著负相关关系,CH₄排放通量与6种土壤酶活性显著负相关（P<0.05）。【结论】在会仙岩溶湿地系统中,天然的湖泊湿地转变为稻田可显著提高土壤酶活性,同时降低CO₂和CH₄的排放量,有利于微生物碳利用率的提高和土壤碳的封存。     

叶面喷施黄腐酸对川芎生长及品质的影响

以川芎苓种为试材,采用随机区组设计并开展大田试验,研究了不同浓度黄腐酸叶面喷施对川芎农艺性状、产量、质量及重金属含量的影响,以期为黄腐酸在川芎上的合理施用提供参考依据.结果 表明:叶面喷施黄腐酸能够显著提升川芎分蘖数和冠幅;川芎在H2(1.0 kg·hm-2)和H3(1.5kg·hm-2)处理后产量较CK提升23.47％以上;H3处理(1.5 kg·hm-2)能增加川芎挥发油和浸出物含量,H1处理(0.5 kg·hm-2)、H2处理(1.0 kg·hm-2)对川芎水溶性浸出物、醇溶性浸出物、挥发油、有效成分等影响较小;川芎施用黄腐酸后对其铅(Pb)、镉(Cd)、砷(As)、汞(Hg)、铜(Cu)5种重金属含量影响较大,其中重金属镉(Cd)含量与黄腐酸施用浓度呈明显的正相关关系,在不同浓度的黄腐酸处理后镉(Cd)含量与CK相比皆高出16.67％以上.综上,叶面喷施黄腐酸对川芎产量及品质提升有促进作用,但增加了其重金属超标风险.     

Effect of fish meal replacement by Chlorella meal with dietary cellulase addition on growth performance,digestive enzymatic activities,histology and myogenic genes’ expression for crucian carp Carassius auratus

This study was conducted to investigate the effects of fish meal (FM) replacement by Chlorella meal (CM) with dietary cellulase supplementation on growth performance, digestive enzymatic activities, histology and myogenic genes’ expression in crucian carp Carassius auratus (initial body weight: 2.90 ± 0.02 g, mean ± SEM). Six isonitrogenous diets were formulated at two cellulase levels (0 and 2 g kg^?1). At each cellulase level, CM was added at three levels of 0, 533.1 and 710.8 g kg^?1 to substitute 0, 75 and 100% of dietary FM respectively. Each experimental diet was randomly assigned to triplicate groups with 25 juvenile fish per fibreglass tank for 8 weeks. Dietary CM substitution significantly increased growth, feed utilization, amylase activity and the expression of Myod, Mrf4 and Myf5, but reduced the Myog expression. Dietary cellulase addition increased hepatosomatic and viscerosomatic index, lipase activity and the expression of Mrf4, but reduced trypsin activity and the expression of Myog and Myf5. Dietary CM substitution enlarged the cell size and also caused some karyopyknosis in liver. Our results showed that CM could totally replace FM in diets; dietary cellulase supplementation at the level of 2 g kg^?1 played a subtle role in improving growth and feed utilization for crucian carp.     

Effects of dietary supplementation of Haematococcus pluvialis powder on gonadal development,coloration and antioxidant capacity of adult male Chinese mitten crab (Eriocheir sinensis)

The green algae Haematococcus pluvialis is an important source of natural astaxanthin as feed additive. This study was conducted to investigate the effects of dietary supplementation of H. pluvialis powder on gonadal development, coloration and antioxidant capacity of adult male Chinese mitten crab Eriocheir sinensis, and four experimental diets were formulated to contain 0, 0.2%, 0.4% and 0.6% of H. pluvialis powder. There were four treatments (defined as D1~D4) in this study and each treatment had three replicates. Dietary H. pluvialis contents had no significant effects on survival, body weight gain rate and gonadal development of male E. sinensis. For colour parameters, the total carotenoids content in carapace and hepatopancreas as well as hepatopancreatic lightness (L*) and carapace redness (a*) increased significantly with increasing dietary H. pluvialis (p < 0.05). For the antioxidant indices in the serum, D4 had the lowest activities of superoxide dismutase (SOD) and peroxidase (POD), but the highest glutathione peroxidase (GSH‐Px) and lactic dehydrogenase (LDH), while the malondialdehyde (MDA) in serum and hepatopancreas decreased significantly with the rising content of dietary H. pluvialis (p < 0.05); D1 had the highest levels of SOD, POD and GSH‐Px in hepatopancreas. For the non‐specific immune indices, the highest activities of acid phosphatase (ACP) and γ‐glutamyl transpeptidase (γ‐GT) were found on the serum of D3 and D4 (p < 0.05). D1 had the highest levels of ACP and alkaline phosphatase (ALP) in hepatopancreas, while D2 and D3 had the lowest levels of ALP and ACP respectively. These results suggested the optimal dietary natural astaxanthin level was around 40 mg/kg diets.     

Impacts of diet on hindgut microbiota and short‐chain fatty acids in grass carp (Ctenopharyngodon idellus)

Diet is known to influence intestinal microbiota in fish, but the specifics of these impacts are still poorly understood. Different protein/fibre ratio diets may result in differing structures and activities of gut microbiota. We examined the hindgut microbiome of grass carp (Ctenopharyngodon idellus) fed three different diets: fish meal (FM, high protein – low fibre), Sudan grass (SG, high fibre – low protein) and compound feed (CF, intermediate). Microbial profiles of fish fed on FM were significantly different from profiles of fish fed CF and SG (F = 18.85, p < .01). Cetobacterium, known to be positively associated with protein digestion, was the dominant microbial group in FM samples (approximately 75.7%), while Lachnospiraceae and Erysipelotrichaceae, thought to be involved in fermentation of plant polysaccharides, were dominant in CF and SG samples (46.8% and 42.9% respectively). Network analyses indicated that the abundance of Lachnospiraceae and Erysipelotrichaceae was in a significantly positive correlation (r = .895, p = .001). Short‐chain fatty acid (SCFA) levels may indicate that the digestibility of diet by microbiota in the grass carp gut decreased from FM to SG (FM>CF>SG). Overall low SCFA levels indicate that hindgut fermentation probably provides a low proportion of energy requirements in grass carp.     

Combining multi-source data to explore a mechanism for the effects of micrometeorological elements on nutrient variations in paddy land water

Paddy land plays a key role in global crop production. Thus, paddy land water is a potential source of nitrogen and phosphorus; both nutrients largely contribute to non-point source pollution because they usually vary closely with micrometeorological elements (MEs) during the growth period. However, few studies have focused on the mechanism of co-variation between nutrients and MEs at the field scale. The relationships between nutrients in the paddy land water and MEs as well as soil water content, soil temperature, and the normalized difference vegetation index (NDVI) are still unclear. In this paper, an in situ experiment was designed to obtain 5 years of meteorological data and nutrient data (nitrogen and phosphorus); the size of the experiment plot is in accordance with the spatial resolution of NDVI data. Multi-source meteorological and satellite data were integrated to explore the mechanism of co-variation. The results show that precipitation, air temperature, and solar radiation are the three MEs significantly affecting the nitrogen concentration in the paddy land water during the growth period. The air temperature is the most important ME influencing the phosphorus concentration. At the same time, the NDVI, as an effective indicator of the photosynthetic potential of rice used to explore the relationship between nutrients, has a prominent influence on soluble nutrients, especially on dissolved phosphorus. These findings could significantly improve our understanding about the responses of paddy land nutrients during the growth period to the surrounding drivers, inclusive of MEs, soil water, soil temperature, and NDVI. Undoubtedly, it is a potentially helpful means to monitor the sources of non-point pollution.     

Artificial fertilization and generating families for a selective breeding programme of large yellow croaker ( Larimichthys crocea )

Large yellow croaker is an important marine aquaculture species in China. The aim was to determine an appropriate protocol of artificial fertilization for family construction in the breeding programme based on two trials. In trial 1, luteinizing hormone-releasing hormone A3 (LHRHA3) was injected once, with a dosage of 2 μg/kg for females and 1 μg/kg for males. The latency time was in the range of 30–34 h. The maturation stage was checked by extracting a few eggs with a Pasteur pipette. The fertilization rate and hatching rate were 27 and 52%, respectively. The percentage of females with spawning difficulties was 30%. In trial 2, the females were injected LHRHA3 twice: with a first dose of 0.8 μg/kg and a second dose of 2 μg/kg, at an interval of 10 h, whereas the males were still injected once. The latency time was in the range of 29.5–35 h, determined by only observing courtship behaviour of males. The females with spawning difficulties decreased to 10%, and the fertilization rate and hatching rate also improved to 41 and 62%, respectively.     

The influence of diet on the grass carp intestinal microbiota and bile acids

To elucidate the influence of different diet on the intestinal microbe and bile acids, we characterized the microbiota and bile acids in the hindgut content of grass carp fed on formula feed (FF group) or Sudan grass (SG group). Fusobacteria and Proteobacteria were significantly more represented in FF group than in SG group whereas Bacteroidetes was significantly more abundant in SG group than in FF group. Simpson diversity was significantly higher in FF group than in SG group (t = 2.33, P < 0.05). Chenodeoxycholic acid (CDCA) was the most abundant primary bile acid in the two groups, with average concentrations of 1.03 ± 0.62 and 4.44 ± 1.80 ng mg^?1 in SG and FF group respectively. The most abundant secondary bile acid was deoxycholic acid (DCA) in SG group and ursodeoxycholic acid (UDCA) in FF group, with average concentrations of 0.17 ± 0.06 and 2.67 ± 0.88 ng mg^?1 respectively. UDCA is significantly more abundant in FF group than in SG group, and the total bile acids were higher in FF group than in SG group. Cetobacterium and Fusobacteriaceae U114 were significantly related with the concentrations of CDCA (r = 0.85, P < 0.05 and r = 0.82, P < 0.05 respectively) and UDCA (r = 0.92, P < 0.01 and r = 0.92, P < 0.01 respectively). However, Bacteroides was negatively related with the concentration of UDCA (r = ?0.67, P < 0.05). Overall, there existed certain relationship between the intestinal microbes and the faecal bile acids, and they were both influenced by the diet.     

火山岩和沸石填料BAF深度处理印染废水的效能比较

针对纺织印染行业水质不达标回用率低的问题,采用火山岩和沸石为填料的曝气生物滤池对纺织印染废水二级生化出水进行了深度处理,进行了两反应器出水效能的比较。研究表明:火山岩填料深度处理纺织印染废水的效能要高于沸石填料,建议气水比在10∶1左右,出水CODcr为36~48mg/L,出水色度35~55度,NH3-N浓度0.5~1.7mg/L,出水浊度范围0.9~3NTU。