Urbanization affects stream ecosystem function by altering hydrology, chemistry, and biotic richness.

Catchment urbanization can alter physical, chemical, and biological attributes of stream ecosystems. In particular, changes in land use may affect the dynamics of organic matter decomposition, a measure of ecosystem function. We examined leaf-litter decomposition in 18 tributaries of the St. Johns River, Florida, USA. Land use in all 18 catchments ranged from 0% to 93% urban which translated to 0% to 66% total impervious area (TIA). Using a litter-bag technique, we measured mass loss, fungal biomass, and macroinvertebrate biomass for two leaf species (red maple [Acer rubrum] and sweetgum [Liquidambar styraciflua]). Rates of litter mass loss, which ranged from 0.01 to 0.05 per day for red maple and 0.006 to 0.018 per day for sweetgum, increased with impervious catchment area to levels of approximately 30-40% TIA and then decreased as impervious catchment area exceeded 40% TIA. Fungal biomass was also highest in streams draining catchments with intermediate levels of TIA. Macroinvertebrate biomass ranged from 17 to 354 mg/bag for red maple and from 15 to 399 mg/bag for sweetgum. Snail biomass and snail and total invertebrate richness were strongly related to breakdown rates among streams regardless of leaf species. Land-use and physical, chemical, and biological variables were highly intercorrelated. Principal-components analysis was therefore used to reduce the variables into several orthogonal axes. Using stepwise regression, we found that flow regime, snail biomass, snail and total invertebrate richness, and metal and nutrient content (which varied in a nonlinear manner with impervious surface area) were likely factors affecting litter breakdown rates in these streams.     

Annual occurrence,abundance and diversity of fish in a South Carolina intertidal creek

An intertidal creek in North Inlet Estuary, South Carolina, USA, was sampled monthly for 1 year to determine the occurrence, abundance and diversity of fish species. Sampling was so conducted as to reduce sampling bias to a minimum and all individuals caught were weighed and measured. A total of 16,611 individuals weighing 202.45 kg and comprising 51 species and 25 families of fish was collected. Three diversity indices were calculated for species number. Analysis of variance revealed that season had a highly significant effect on all indices and the number of species, but had no effect on the number of individuals caught.This work was supported by the Belle W. Baruch Foundation and the South Carolina State Development Board, and is Contribution No. 71 of the Belle W. Baruch Institute for Marine Biology and Coastal Research.     

铜绿假单孢菌AS1.860对紫杉醇的微生物转化

从32株微生物中筛选出对紫杉醇1具有转化能力的4个菌株，并从中挑选出铜绿假单孢菌AS1．860进行放大实验，投入100mg紫杉醇，分离出3个产物，并通过核磁共振谱鉴定了结构，分别为baccatin Ⅲ2、baccatin V3和10—去乙酰baccatin Ⅲ4，其中2和3也是人体代谢的产物。     

Cadmium in naturally-occurring water hyacinths

Water hyacinth [$\text{Eichhornia}$$\text{crassipes}$ (Mart.) Solms] is an effective fertillizer, mulch, soil amendment and fodder for cattle and sheep. The consequences of the ability of the plant to accumulate heavy metals needs consideration. Small and large water hyacinth ecotypes collected from two “rural” rivers in Florida, the Peace and Withalachoochee respectively, were examined for an accumulation of cadmium from the natural environment. Less than trace amounts (below limits of detection, 2.5ppb) were present. Water hyacinths tested for cadmium accumulation under laboratory conditions exhibited a pronounced ability to absorb and accumulate the metal. The roots contained 0.982 mg of the 2.0 mg cadmium presented to the plant. The distribution of the metal within the plant was 76.7% in the roots, 22.4% in the stems with the remainder in the leaves. Of the total cadmium presented to the plant, 80.8 ± 3.0% was recovered by the plant after 7 days, the mean generation time of the plant. With increasing urbanization, accumulation of cadmium by water hyacinths exists. It is either an asset or a potential hazard and needs to be appreciated.     

Assessing the recovery of lakes in southeastern Canada from the effects of acidic deposition

Reductions in North American sulfur dioxide (SO2) emissions promoted expectations that aquatic ecosystems in southeastern Canada would soon recover from acidification. Only lakes located near smelters that have dramatically reduced emissions approach this expectation. Lakes in the Atlantic provinces, Quebec and Ontario affected only by long-range sources show a general decline in sulfate (SO4(2-)) concentrations, but with a relatively smaller compensating increase in pH or alkalinity. Several factors may contribute to the constrained (or most likely delayed) acidity response: declining base cation concentrations, drought-induced mobilization of SO4(2-), damaged internal alkalinity generation mechanisms, and perhaps increasing nitrate or organic anion levels. Monitoring to detect biological recovery in southeastern Canada is extremely limited, but where it occurs, there is little evidence of recovery outside of the Sudbury/Killarney area. Both the occurrence of Atlantic salmon in Nova Scotia rivers and the breeding success of Common Loons in Ontario lakes are in fact declining although factors beyond acidification also play a role. Chemical and biological models predict that much greater SO2 emission reductions than those presently required by legislation will be needed to promote widespread chemical and latterly, biological recovery. It may be unrealistic to expect that pre-industrial chemical and biological conditions can ever be reestablished in many lakes of southeastern Canada.     

Human health risk from Pb in urban street dust in northern UK cities

The presence of Pb in the environment can cause significant health problems. These issues are exasperated when the lead is in a more amenable form for potential ingestion. This study investigates the potential human health risk from Pb in urban street dusts. The lead levels in urban street dust in major city centres in northern UK have been compared to levels determined in 35 cities around the world. With a few exceptions, it was noted that the mean Pb levels in this study exceeded those found in other cities worldwide. Samples (n = 15) of urban street dust were collected across five city centres, and specifically in areas in which pedestrians are likely to concentrate, as well as near historical buildings. Typical total lead concentrations across all sampling sites ranged from 306 to 558 mg/kg. The human health risk was assessed using oral bioaccessibility testing of the urban street dust. The mean oral bioaccessibility data, irrespective of site and sample location, were in the range 43 ± 9 %. The total and bioaccessible concentrations of lead were compared to the estimated tolerable daily intake (TDI_oral) values based on unintentional soil/dust consumption. It is noted, in all cases, that the maximum estimated lead daily intake exceeded the TDI_oral. An alternative approach for assessing the daily intake is proposed based on the actual measured air quality in selected cities on the same day as the sampled urban dust.     

Melt Strength and Rheological Properties of Biodegradable Poly(Lactic Aacid) Modified via Alkyl Radical-Based Reactive Extrusion Processes

Poly(lactic acid) (PLA) has been modified using twin-screw reactive extrusion to improve its melt properties and crystallinity. In this work lauroyl peroxide was used as an alkyl free radical source, abstracting hydrogen atoms from the PLA backbone leading to branching and chain extension reactions. Once the linear viscoelastic region was determined for these polymers, changes in dynamic rheology (dynamic viscosity real and loss modulus) were measured. Gel permeation chromatography showed that the molecular weight and polydispersity increased to a maximum with the addition of 1.00 and 0.50?wt% peroxide, respectively. Low temperature ?? transitions in dynamical mechanical thermal traces gave further evidence that branching had also occurred. G?ttfert Rheotens measurements showed a three fold increase in melt strength due to both increased chain length and branching. Thermal analysis showed the level of crystallisation had decreased also possibly due to branching. Reductions in crystallinity and improved melt strength are known to be critical for film and foam formation.     

How safe is the playground? An environmental health risk assessment of As and Pb levels in school playing fields in NE England

The risk from potentially toxic elements in playground soils is of concern to children’s health as a result of the potential for intentional or unintentional consumption. Current approaches, based on total potentially toxic element concentration, may overestimate the risk. This has resulted in the development and use of in vitro gastrointestinal extraction protocols. The concentration of arsenic (As) and lead (Pb) in soils collected from 12 schools in north-east England has been compared with Soil Guideline Values from seven countries as well as reported literature concentrations for playgrounds and recreational parks. It was found that the mean As concentration of 14.1 ± 5.4 mg/kg does not exceed the England residential Soil Guideline Value in any location, while the mean Pb concentration of 298 ± 380 mg/kg is high but not excessive. Both concentrations have been assessed using the maximum potential daily intake from soil that a child could ingest. Based on this protocol Pb does not exceed the tolerable daily intake in any playground location, while As is generally 10 times lower than the oral index dose in the majority of playgrounds. The oral bioaccessibility of As and Pb was investigated. It was concluded that the highest concentrations were determined in the gastric phase with maximum bioaccessibilities of 54 and 46 % for As and Pb, respectively. Here we have demonstrated that minimal risk arises from the investigated playgrounds provided that good personal hygiene is adhered to.     

Assessment of the aquatic biodiversity of a threatened coastal lagoon at Bimini, Bahamas

Coastal biodiversity is threatened worldwide by both direct and indirect anthropogenic activities. To more effectively manage and protect coastal biodiversity, accurate assessments of genetic, species, and ecosystem level diversity are required. We present the results from an assessment of the aquatic species diversity of a small (3?km²), shallow, mangrove-fringed Bahamian lagoon (the North Sound) subject to ongoing anthropogenic development. The assessment was conducted through a collation of field observations and data in published literature. We found that eight angiosperm species, 30 macroalgal species, and 370 animal species (including 95 fishes, 69 arthropods, 56 birds, and 45 mollusks) were documented within the lagoon. At least 11 of these species are of conservation concern, such as the critically endangered smalltooth sawfish (Pristis pectinata) and hawksbill turtle (Eretmochelys imbricata). Comparisons of community similarity indicated that the North Sound has a relatively distinct fauna and flora, but available data suggest that the species found there are most similar to those found in nearby habitats in Cuba. The lagoon forms a key nursery habitat for many species, including lemon sharks (Negaprion brevirostris), Caribbean spiny lobsters (Panulirus argus), and queen conch (Strombas gigas). Recently, the lagoon was included as part of a new marine protected area (MPA), but much of the habitat has already experienced considerable anthropogenic disturbance and the MPA boundaries have yet to be established. We have therefore analyzed the lagoon biodiversity and expect the data presented here to serve as a baseline for future comparisons.