超声萃取-佛罗里土净化-气相色谱法测定沉积物中的多氯联苯

应用毛细管柱气相色谱技术对海洋沉积物中的的多氯联苯进行了分析研究；沉积物中多氯联苯经超声提取、浓硫酸-佛罗里土柱净化、毛细管柱分离后，由GC-ECD测定。本方法的标准加标回收率在75．8％～102．4％之间，检测下限在2．72×10^-11～5．78×10^-11之间。实验结果表明，本方法适用于沉积物样品中多氯联苯的测定。

牛奶中多种有机氯和拟除虫菊酯类农药残留的测定

本文同时测定牛奶中的11种有机氯和拟除虫菊酯类农残。样品经乙睛溶剂提取，离心，佛罗里硅土SPE净化小柱纯化、富集，采用毛细管气相色谱，电子捕获检测器进行定最检测。本文的加标叫收率为68～99％；枪出限为0．25～0．50ug／Kg。

Numerical Modeling of Shallow Water Table Behavior with Lisse Effect

Air entrapment is an important consideration in environments with shallow water tables and sandy soil, like the condition of highly conductive sandy soils and flat topography in Florida, USA. It causes water table rises in soils, which are significantly faster and higher than those in soils without air entrapment. Two numerical models, Integrated Hydrologic Model (IHM) and HYDRUS-1D (a single-phase, one-dimensional Richards′ equation model) were tested at an area of west central Florida to help further understanding the shallow water table behavior during a long term air entrapment. This investigation employed field data with two modeling approaches to quantify the variation of air pressurization values. It was found that the air pressurization effect was responsible at time up to 40 cm of water table rise being recorded by the observation well for these two models. The values of air pressurization calculated from IHM and HYDRUS-1D match the previously published values. Results also indicated that the two numerical models did not consider air entrapment effect (as the predictive parameters remain uncertain) and thus results of depth to water table from these models did not compare to the observations for these selected periods. Incorporating air entrapment in prediction models is critical to reproduce shallow water table observations.

Validation of Growth and Nutrient Uptake Models for Tomato on a Gravelly South Florida Soil Under Greenhouse Conditions

The Soil and Water Assessment Tool(SWAT) has been widely used throughout the world to model crop growth and nutrient uptake in various types of soils.A greenhouse experiment was performed to validate the process equations embedded in SWAT for describing the growth and nutrient uptake of tomatoes in south Florida.The scaled growth curve of greenhouse-grown tomatoes was in close agreement with the theoretical model for field conditions,with the scaling factors being the maximum canopy height and the potential heat units.Similarly,the scaled leaf area index(LAI) growth curve and the scaled root depth curve for greenhousegrown tomatoes agreed with the SWAT functions,with the scaling factors being the maximum LAI and maximum root depth.The greenhouse experiment confirmed that the growth of biomass is a linear function of the intercepted photosynthetically active radiation.The fractions of nutrients in the plant biomass under greenhouse conditions were found to be on the order of 60% of those fractions observed in the field.Values of the initial P distribution(0.2 mg kg -1),initial ratio of mineral stable P to mineral active P(50:1),and initial ratio of humic N to humic P(2.4:1) were determined from soil measurements and can be used for field simulations.The conventional saturation-excess model for soil-water percolation was used to predict the movement of water in the top 10 cm of the greenhouse containers and the results agreed well with measurements.

Application of Visible/Near-Infrared Spectra in Modeling of Soil Total Phosphorus

Overabundance of phosphorus (P) in soils and water is of great concern and has received much attention in Florida, USA. Therefore, it is essential to analyze and predict the distribution of P in soils across large areas. This study was undertaken to model the variation of soil total phosphorus (TP) in Florida. A total of 448 soil samples were collected from different soil types. Soil samples were analyzed by chemical reference method and scanned in the visible/near-infrared (VNIR) region of 350-2 500 nm. Partial least squares regression (PLSR) calibration model was developed between chemical reference values and VNIR values. The coefficient of determination (R2) and the root mean squares error (RMSE) of calibration and validation sets, and the residual prediction deviation (RPD) were used to evaluate the models. The R2in calibration and validation for log-transformed TP (log TP) were 0.69 and 0.65, respectively, indicating that VNIR calibration obtained in this study accounted for at least 65% of the variance in log TP using only VNIR spectra, and the high RPD of 2.82 obtained suggested that the spectral model derived in this study was suitable and robust to predict TP in a wide range of soil types, being representative of Florida soil conditions.

Invasion and predation in aquatic ecosystems

This article reviews biological invasions in which predation （or its absence） plays a major role in the success of the invader. Examples are described in which the invader out-competes native species for the same food, and cases in which the in-vader consumes valued native species. In many instances, better predator avoidance by the invasive species or the absence of predators in the new habitat contributes to the success of the invaders; in other cases native or introduced predators appear to be able to keep the invasive species in check. A relatively new management approach in the US is the idea of adding another trophic level - to have humans act as the predators and consume the invasive species. This approach is being utilized in Florida and throughout the Caribbean against the lionfish, but could be extended to other fishes, as well as to various invasive crustaceans and mollusks. This idea is controversial, and current regulations prohibiting the possession of individuals of the invasive species （e.g., mitten crabs or snakefish） would preclude the development of a fishery for them [Current Zoology 57 （5）： 613~524, 2011].