Variations in pesticide leaching related to land use, pesticide properties, and unsaturated zone thickness

Pesticide leaching through variably thick soils beneath agricultural fields in Morgan Creek, Maryland was simulated for water years 1995 to 2004 using LEACHM (Leaching Estimation and Chemistry Model). Fifteen individual models were constructed to simulate five depths and three crop rotations with associated pesticide applications. Unsaturated zone thickness averaged 4.7 m but reached a maximum of 18.7 m. Average annual recharge to ground water decreased from 15.9 to 11.1 cm as the unsaturated zone increased in thickness from 1 to 10 m. These point estimates of recharge are at the lower end of previously published values, which used methods that integrate over larger areas capturing focused recharge in the numerous detention ponds in the watershed. The total amount of applied and leached masses for five parent pesticide compounds and seven metabolites were estimated for the 32-km2 Morgan Creek watershed by associating each hectare to the closest one-dimensional model analog of model depth and crop rotation scenario as determined from land-use surveys. LEACHM parameters were set such that branched, serial, first-order decay of pesticides and metabolites was realistically simulated. Leaching is predicted to be greatest for shallow soils and for persistent compounds with low sorptivity. Based on simulation results, percent parent compounds leached within the watershed can be described by a regression model of the form e(-depth) (a ln t1/2-b ln K OC) where t1/2 is the degradation half-life in aerobic soils, K OC is the organic carbon normalized sorption coefficient, and a and b are fitted coefficients (R2 = 0.86, p value = 7 x 10(-9)).     

The impact of alum addition on organic P transformations in poultry litter and litter-amended soil

Poultry litter treatment with alum (Al(2)(SO(4))(3) . 18H(2)O) lowers litter phosphorus (P) solubility and therefore can lower litter P release to runoff after land application. Lower P solubility in litter is generally attributed to aluminum-phosphate complex formation. However, recent studies suggest that alum additions to poultry litter may influence organic P mineralization. Therefore, alum-treated and untreated litters were incubated for 93 d to assess organic P transformations during simulated storage. A 62-d soil incubation was also conducted to determine the fate of incorporated litter organic P, which included alum-treated litter, untreated litter, KH(2)PO(4) applied at 60 mg P kg(-1) of soil, and an unamended control. Liquid-state (31)P nuclear magnetic resonance indicated that phytic acid was the only organic P compound present, accounting for 50 and 45% of the total P in untreated and alum-treated litters, respectively, before incubation and declined to 9 and 37% after 93 d of storage-simulating incubation. Sequential fractionation of litters showed that alum addition to litter transformed 30% of the organic P from the 1.0 mol L(-1) HCl to the 0.1 mol L(-1) NaOH extractable fraction and that both organic P fractions were more persistent in alum-treated litter compared with untreated litter. The soil incubation revealed that 0.1 mol L(-1) NaOH-extractable organic P was more recalcitrant after mixing than was the 1.0 mol L(-1) HCl-extractable organic P. Thus, adding alum to litter inhibits organic P mineralization during storage and promotes the formation of alkaline extractable organic P that sustains lower P solubility in the soil environment.     

Measuring the Impact of Urbanization on Channel Widths Using Historic Aerial Photographs and Modern Surveys1

Abstract: Land use in a watershed is commonly held to exert a strong influence on trunk channel form and process. Land use changes act over human time‐scales, which are short enough to measure effects on channels directly using historic aerial photographs. We show that high‐resolution topographic surveys for the channels of paired watersheds in the Lehigh Valley, Pennsylvania, are comparable, but have channel widths that have changed dramatically in the past five decades. The two watersheds, Little Lehigh Creek and Sacony Creek, are similar in most aspects except in their respective amount of urban land use. Aerial photographs of the urbanized Little Lehigh Creek show that a majority of the measured widths (67 of 85) were statistically wider in 1999 than in 1947. In contrast, the measured widths from the agricultural Sacony Creek are more evenly distributed among those that widened (18), narrowed (28), and those that were statistically unchanged (6) from 1946 to 1999. From 1946 to 1999 the only section of Sacony Creek that widened was that reach downstream of the only sizable urban area in the watershed. The current land use in Sacony Creek watershed resembles that of 1946, while the Little Lehigh Creek watershed has more than tripled its urban area. These data, in concert with other recent hydrologic data from the watersheds suggest that the increase in urban area‐generated peak discharges is the mechanism behind the widening that occurred in the Little Lehigh Creek. These wider channels can affect water quality, aquatic habitat, suspended sediment loads, and river esthetics.     

A modeling study of coarse particulate matter pollution in Beijing: regional source contributions and control implications for the 2008 Summer Olympics

In the last 10 yr, Beijing has made a great effort to improve its air quality. However, it is still suffering from regional coarse particulate matter (PM10) pollution that could be a challenge to the promise of clean air during the 2008 Olympics. To provide scientific guidance on regional air pollution control, the Mesoscale Modeling System Generation 5 (MM5) and the Models-3/Community Multiscale Air Quality Model (CMAQ) air quality modeling system was used to investigate the contributions of emission sources outside the Beijing area to pollution levels in Beijing. The contributions to the PM10 concentrations in Beijing were assessed for the following sources: power plants, industry, domestic sources, transportation, agriculture, and biomass open burning. In January, it is estimated that on average 22% of the PM10 concentrations can be attributed to outside sources, of which domestic and industrial sources contributed 37 and 31%, respectively. In August, as much as 40% of the PM10 concentrations came from regional sources, of which approximately 41% came from industry and 31% from power plants. However, the synchronous analysis of the hourly concentrations, regional contributions, and wind vectors indicates that in the heaviest pollution periods the local emission sources play a more important role. The implications are that long-term control strategies should be based on regional-scale collaborations, and that emission abatement of local sources may be more effective in lowering the PM10 concentration levels on the heavy pollution days. Better air quality can be attained during the Olympics by placing effective emission controls on the local sources in Beijing and by controlling emissions from industry and power plants in the surrounding regions.     

Soil erosion and sediment fluxes analysis: a watershed study of the Ni Reservoir,Spotsylvania County,VA, USA

Anthropogenic forces that alter the physical landscape are known to cause significant soil erosion, which has negative impact on surface water bodies, such as rivers, lakes/reservoirs, and coastal zones, and thus sediment control has become one of the central aspects of catchment management planning. The revised universal soil loss equation empirical model, erosion pins, and isotopic sediment core analyses were used to evaluate watershed erosion, stream bank erosion, and reservoir sediment accumulation rates for Ni Reservoir, in central Virginia. Land-use and land cover seems to be dominant control in watershed soil erosion, with barren land and human-disturbed areas contributing the most sediment, and forest and herbaceous areas contributing the least. Results show a 7 % increase in human development from 2001 (14 %) to 2009 (21.6 %), corresponding to an increase in soil loss of 0.82 Mg ha^-1 year^-1 in the same time period. ²¹⁰Pb-based sediment accumulation rates at three locations in Ni Reservoir were 1.020, 0.364, and 0.543 g cm^-2 year^-1 respectively, indicating that sediment accumulation and distribution in the reservoir is influenced by reservoir configuration and significant contributions from bedload. All three locations indicate an increase in modern sediment accumulation rates. Erosion pin results show variability in stream bank erosion with values ranging from 4.7 to 11.3 cm year^-1. These results indicate that urban growth and the decline in vegetative cover has increased sediment fluxes from the watershed and poses a significant threat to the long-term sustainability of the Ni Reservoir as urbanization continues to increase.     

Unique phenotypes in the sperm of the earthworm Eudrilus eugeniae for assessing radiation hazards

The earthworm, Eudrilus eugeniae is a segmented worm. It has two pairs of testes whose cells are highly proliferative. It was found that the earthworm, which is irradiated with X-ray, shows the following phenotypic changes in its sperm: fragmented acrosome in the head, break in the tail, and the appearance of zigzag sperm tail. Sperm morphology can be used as a tool to study radiation hazards in local areas. These three phenotypes were not observed in the sperm of worms exposed to different concentration of toxic chemicals such as sodium arsenate, lead acetate, and mercuric chloride. In contrast, exposure of worms to ethidium bromide caused fragmented acrosome in the head of their sperm cells.     

Divergence in sink contributions to population persistence

Population sinks present unique conservation challenges. The loss of individuals in sinks can compromise persistence; but conversely, sinks can improve viability by improving connectivity and facilitating the recolonization of vacant sources. To assess the contribution of sinks to regional population persistence of declining populations, we simulated source–sink dynamics for 3 very different endangered species: Black‐capped Vireos (Vireo atricapilla) at Fort Hood, Texas, Ord's kangaroo rats (Dipodomys ordii) in Alberta, and Northern Spotted Owls (Strix occidentalis caurina) in the northwestern United States. We used empirical data from these case studies to parameterize spatially explicit individual‐based models. We then used the models to quantify population abundance and persistence with and without long‐term sinks. The contributions of sink habitats varied widely. Sinks were detrimental, particularly when they functioned as strong sinks with few emigrants in declining populations (e.g., Alberta's Ord's kangaroo rat) and benign in robust populations (e.g., Black‐capped Vireos) when Brown‐headed Cowbird (Molothrus ater) parasitism was controlled. Sinks, including ecological traps, were also crucial in delaying declines when there were few sources (e.g., in Black‐capped Vireo populations with no Cowbird control). Sink contributions were also nuanced. For example, sinks that supported large, variable populations were subject to greater extinction risk (e.g., Northern Spotted Owls). In each of our case studies, new context‐dependent sinks emerged, underscoring the dynamic nature of sources and sinks and the need for frequent re‐assessment. Our results imply that management actions based on assumptions that sink habitats are generally harmful or helpful risk undermining conservation efforts for declining populations.     

应用Models-3/CMAQ研究长三角区域大气污染及输送

选用美国国家环保局第3代空气质量模式（Models-3，／CMAQ），配合中尺度气象模式（MM5）进行研究，模拟了2001年1、7月份长江三角洲区域冬夏季典型天气条件下大气层二次污染物臭氧及颗粒物的浓度分布及输送状况。采用2001年冬．夏季各10d的小时监测数据对模式验证。结果表明，Models-3／CMAQ对O3、PM10的模拟相关系数分别为0．77和052；一致性指数分别达到081和0．99。模型对于O3略微低估，标准偏差为-31％，而对于PM10则有所高估，标准偏差为46％。对长三角7月份O3浓度及1月份PM10的模拟结果显示，7月份长三角区域16个主要城市O3日均浓度集中在0．043～0．086mg／m^3之间，其中，泰州、扬州．湖州、镇江O3月日均浓度相对较高，均超过0．064mg／m3o模拟时段内O3最高小时浓度达0．276mg／m^3。1月份整个模拟区域PM10月日均浓度为O056mg／m^3，其中，南京市PM10日均浓度最高，达0．080mg／m^3模拟时段内PM10最高小时浓度达0.432mg／m^3研究表明，长三角地区存在明显的污染物输送现象，大气污染已经从局地污染转化为区域污染。     

First-trimester prenatal diagnosis of osteogenesis imperfecta type II by DNA analysis and sonography

Osteogenesis imperfecta type II was diagnosed prenatally by analysis of DNA obtained from chorionic villus sampling (CVS) performed at 12 weeks of gestation in a woman who previously had had an affected child. The father had been shown to be mosaic for a mutation in the gene (COL1A2) which encodes the α2(I) chain of type I collagen. An affected fetus was predicted by detection of the mutation in amplified chorionic villus genomic DNA. Ultrasound examination at 13 weeks 4 days demonstrated femoral deformity and virtual absence of calvarial mineralization. In pregnancies at risk for osteogenesis imperfecta type II, sonographic evidence of skeletal abnormalities may be evident by 13 weeks' gestation.