超高效液相色谱-串联质谱法测定香蕉中壬基酚聚氧乙烯醚及其降解产物

为了研究壬基酚聚氧乙烯醚在食品中的残留量及安全性,通过乙腈提取、固相萃取法净化,建立了香蕉中壬基酚聚氧乙烯醚(NPnEO)及其降解产物壬基酚(NP)的超高效液相色谱-串联质谱(UPLC-MS/MS)测定方法,并对流动相、监测离子和校正曲线等进行了优化和探讨。结果表明:在5~40 μ g/kg添加水平范围内,NPnEO及NP的添加回收率在75%~117%之间,相对标准偏差(RSD)在3.2%~9.6%之间;NPnEO的检出限在0.005~0.04 μ g/kg之间,NP的检出限(LOD)为0.5 μ g/kg;该方法快速、灵敏,准确度高,符合残留检测的要求。     

东北地区湿润指数及其干湿界线的变化特征

利用1961～2007年东北地区124个气象站的温度、降水、风、水汽压、日照等气候资料,采用Penman-Monteith-模型计算参考蒸散量,进一步计算了湿润指数,分析了参考蒸散量和湿润指数的变化趋势及干湿界线的变化情况.结果表明:湿润指数总体呈下降的趋势,变干趋势发生在半干旱半湿润气候区及湿润气候区的大部分地区,湿...     

鼠害的综合防治试验

采用农业、化学、器械和生物防治的方法,对鼠害进行综合防治.试验的结果:鼠口密度下降了89%～93%,鼠害率控制在0.7%～1.1%,支收比为1:41.1,防治效果和经济效益显著。     

ABC-ELISA法检测犊弓首蛔虫IgG抗体实验研究

首次以动物为模型,应用 ABC-ELISA 法对家兔血清中犊弓首蛔虫 IgG 抗体进行了测试研究。实验中对犊弓首蛔虫的成虫体壁抗原、体腔液抗原、生殖器官抗原、虫卵抗原、幼虫抗原进行了比较研究,结果显示:幼虫抗原对血清检测的 P/N 值及对被检血清的检出率最高,而检测对照组血清未出现假阳性反应.由此表明,幼虫抗原是最敏感和特异的抗原.在检测方法上,ABC-ELISA 法对被检血清的检出率为96.62%。常规 ELISA 法和 IHA 法的检出率分别为90%和56.67%。3种方法检测对照组血清未出现假阳性反应;在抗体检测滴度上,ABC-ELISA 法比常规 ELISA 法高1～4倍,比 IHA 法高4～128倍.经统计处理,ABC-ELISA 法比常规 ELISA 法敏感1.21倍,比 IHA 法敏感33.76倍.在特异性实验中,用 ABC-ELISA 法检测家兔血清中犊弓首蛔虫 IgG 抗体,与实验家兔乳突类圆线虫和肝片吸虫阳性血清均未出现交叉反应,表明该法检测犊弓首蛔虫抗体特异性良好.另外,对4份血清多次重复检测结果,批内重复和批间试验 OD 值变异系数不超过10%,表明该法稳定性良好.实验结果表明,ABC-ELISA 法具有敏感性高,特异性强,并有较好的稳定性,可用于犊弓首蛔虫抗体的检测,故该法的建立无疑具有理论和实践意义.     

土壤中钙键和铁/铝键结合的有机碳差异的比较

为研究矿质元素在有机碳矿化中所起的作用,以棕壤、黄棕壤、红壤为供试土壤,比较了不同利用方式和施肥处理土壤中钙键、铁/铝键结合的有机碳的差异。结果表明,从北至南的地带性土壤(棕壤、黄棕壤和红壤)系列中,全钙及与有机碳结合的钙依次降低,钙键结合的有机碳占有机碳总量的比值依次升高;铁/铝键结合的有机碳及其占全碳的比值依次升高。与自然土壤相比,耕作土壤在不施肥条件下,钙键有机碳、铁/铝键有机碳占有机碳总量的比值增加,且铁/铝键有机碳占有机碳总量比值的增加率始终比钙键有机碳占有机碳总量比值的增加率要高;覆膜比不覆膜时铁/铝键有机碳占有机碳总量比值的增加率比钙键有机碳占有机碳总量比值的增加率高得多。这表明,与全土有机碳相比,有机碳矿化稳定性由高到低依次是铁/铝键有机碳、钙键有机碳、全土有机碳。     

Variable use of plant- and soil-derived carbon by microorganisms in agricultural soils

In this study we used compound specific ¹³C and ¹⁴C isotopic signatures to determine the degree to which recent plant material and older soil organic matter (SOM) served as carbon substrates for microorganisms in soils. We determined the degree to which plant-derived carbon was used as a substrate by comparison of the ¹³C content of microbial phospholipid fatty acids (PLFA) from soils of two sites that had undergone a vegetation change from C3 to C4 plants in the past 20-30 years. The importance of much older SOM as a substrate was determined by comparison of the radiocarbon content of PLFA from soils of two sites that had different ¹⁴C concentrations of SOM.The ¹³C shift in PLFA from the two sites that had experienced different vegetation history indicated that 40-90% of the PLFA carbon had been fixed since the vegetation change took place. Thus PLFA were more enriched in ¹³C from the new C4 vegetation than it was observed for bulk SOM indicating recent plant material as preferentially used substrate for soil microorganisms. The largest ¹³C shift of PLFA was observed in the soil that had high ¹⁴C concentrations of bulk SOM. These results reinforce that organic carbon in this soil for the most part cycles rapidly. The degree to which SOM is incorporated into microbial PLFA was determined by the difference in ¹⁴C concentration of PLFA derived from two soils one with high ¹⁴C concentrations of bulk SOM and one with low. These results showed that 0-40% of SOM carbon is used as substrate for soil microorganisms. Furthermore a different substrate usage was identified for different microorganisms. Gram-negative bacteria were found to prefer recent plant material as microbial carbon source while Gram-positive bacteria use substantial amounts of SOM carbon. This was indicated by ¹³C as well as ¹⁴C signatures of their PLFA. Our results find evidence to support ‘priming’ in that PLFA indicative of Gram-negative bacteria associated with roots contain both plant- and SOM-derived C. Most interestingly, we find PLFA indicative of archeobacteria (methanothrophs) that may indicate the use of other carbon sources than plant material and SOM to a substantial amount suggesting that inert or slow carbon pools are not essential to explain carbon dynamics in soil.     

The effect of land cover/vegetation on soil water dynamic in the hilly area of the loess plateau,China

Severe soil and water loss has lead to widespread land degradation in China's loess plateau. During the past decades, a great deal of effort was made on vegetation restoration to reduce soil and water loss in the loess plateau. However, due to water shortage the efficiency of vegetation restoration was not as satisfactory as expected. As part of a vegetation restoration project, we conducted research aiming to understand the relationship between vegetation pattern and soil water dynamics. The goal was to find vegetation types appropriate for the loess plateau with scarce water resources. In 1986, fifteen plots of land were planted with five vegetation types: pine woodland, shrubland, sloping cropland, alfalfa and semi-natural grassland. Soil water content, runoff, soil erosion were measured for each plot. Environmental variables, such as rainfall, evaporation and temperature, were recorded simultaneously by an automated meteorological station. The relationship between land cover pattern and soil water dynamic was evaluated by using statistical models. We found that: (1) soil water loss occurred during the growing season, and it reached the maximum in the second half of July; (2) soil water was not fully replenished from rainfall during the rainy season; (3) pine woodland induced the largest water loss to surface runoff, followed by sloping cropland, alfalfa, semi-natural grassland and shrubland; the poor capability of pine woodland for water conservation may be attributed to soil compaction and poor ground coverage under the tree; (4) in most cases, soil water of the five vegetation types was low except for shrubland and semi-natural grassland where it was moderate-high during a few periods. These conditions inhibit sustainable vegetation growth in the semi-arid loess hilly area of the loess plateau, China.