Hypoxia in the Gulf of Mexico

Seasonally severe and persistent hypoxia, or low dissolved oxygen concentration, occurs on the inner- to mid-Louisiana continental shelf to the west of the Mississippi River and Atchafalaya River deltas. The estimated areal extent of bottom dissolved oxygen concentration less than 2 mg L-1 during mid-summer surveys of 1993-2000 reached as high as 16,000 to 20,000 km2. The distribution for a similar mapping grid for 1985 to 1992 averaged 8000 to 9000 km2. Hypoxia occurs below the pycnocline from as early as late February through early October, but is most widespread, persistent, and severe in June, July, and August. Spatial and temporal variability in the distribution of hypoxia exists and is, at least partially, related to the amplitude and phasing of the Mississippi and Atchafalaya discharges and their nutrient flux. Mississippi River nutrient concentrations and loadings to the adjacent continental shelf have changed dramatically this century, with an acceleration of these changes since the 1950s to 1960s. An analysis of diatoms, foraminiferans, and carbon accumulation in the sedimentary record provides evidence of increased eutrophication and hypoxia in the Mississippi River delta bight coincident with changes in nitrogen loading.     

Bioavailability of biosolids molybdenum to soybean grain

Legumes grown in biosolids-amended soils and then fed to ruminants can represent problematic sources of molybdenum (Mo), but few field data are available to quantify the risk. We used a set of fields amended to high cumulative biosolids Mo loads (>18 kg ha(-1)) over 27 yr to generate additional data. Soybean [Glycine max (L.) Merr.] was grown on 29 fields (pH values>6.8) amended to a wide range of soil Mo loads. Soybean grain harvested from each field was analyzed for Mo and the concentrations regressed against soil Mo loads estimated from actual soil Mo concentrations in the 0- to 15-cm depth. Slopes of such linear regressions represent uptake coefficients (UC values) used by the USEPA to assess risk of biosolids Mo to ruminants fed forage grown on biosolids-amended land. The UC value for all 29 fields was estimated as 1.66, which agrees with the few soybean grain data in the literature. The UC value, however, is well below a conservative UC value of 4, recently recommended for all fresh legume materials fed to cattle. Soybean grain can contain high concentrations of Mo (>10 mg kg(-1)) and have low (<2:1) Cu to Mo ratios, which can exacerbate molybdenosis problems in cattle. However, soybean grain normally constitutes only -10% of dairy cattle diet, and other constituents (e.g., corn grain, stover, mineral supplements) are sufficient, or can be manipulated, to control molybdenosis.     

Ecological impacts of arable intensification in Europe

Although arable landscapes have a long history, environmental problems have accelerated in recent decades. The effects of these changes are usually externalized, being greater for society as a whole than for the farms on which they operate, and incentives to correct them are therefore largely lacking. Arable landscapes are valued by society beyond the farming community, but increased mechanization and farm size, simplification of crop rotations, and loss of non-crop features, have led to a reduction in landscape diversity. Low intensity arable systems have evolved a characteristic and diverse fauna and flora, but development of high input, simplified arable systems has been associated with a decline in biodiversity. Arable intensification has resulted in loss of non-crop habitats and simplification of plant and animal communities within crops, with consequent disruption to food chains and declines in many farmland species. Abandonment of arable management has also led to the replacement of such wildlife with more common and widespread species. Soils have deteriorated as a result of erosion, compaction, loss of organic matter and contamination with pesticides, and in some areas, heavy metals. Impacts on water are closely related to those on soils as nutrient and pesticide pollution of water results from surface runoff and subsurface flow, often associated with soil particles, which themselves have economic and ecological impacts. Nitrates and some pesticides also enter groundwater following leaching from arable land. Greatest impacts are associated with simplified, high input arable systems. Intensification of arable farming has been associated with pollution of air by pesticides, NO2 and CO2, while the loss of soil organic matter has reduced the system's capacity for carbon sequestration. International trade contributes to global climate change through long distance transport of arable inputs and products. The EU Rural Development Regulation (1257/99) provides an opportunity to implement measures for alleviating ecological impacts of arable management through a combination of cross-compliance and agri-environment schemes. To alleviate the problems described in this paper, such measures should take account of opportunities for public/private partnerships and should integrate social, cultural, economic and ecological objectives for multifunctional land use.     

Relationships between ambient geochemistry, watershed land-use and trace metal concentrations in aquatic invertebrates living in stormwater treatment ponds

Stormwater treatment ponds receive elevated levels of metals from urban runoff, but the effects of these pollutants on organisms residing in the ponds are unknown. We investigated the accumulation of Cu, Zn, and Pb by macroinvertebrates collected from stormwater treatment ponds in Maryland serving commercial, highway, residential and open-space watersheds, and determined whether watershed land-use classification influences metal concentrations in macroinvertebrates, sediments, and water. Three types of invertebrate samples were analyzed--molluscs, odonates, and composite. Zn concentrations in odonates from ponds draining watersheds with commercial development (mean = 113.82 micrograms g-1) were significantly higher than concentrations in the other land-use categories. Similarly, Cu levels in odonates from commercial ponds (mean = 27.12 micrograms g-1) were significantly higher than from highway (mean = 20.23 micrograms g-1) and open space (mean = 17.79 micrograms g-1) ponds. However, metal concentrations in sediments and water did not differ significantly among land-uses. The results suggest that despite the high variation in ambient metal concentrations within each land-use category, macroinvertebrates in ponds serving commercial watersheds accumulate higher levels of Cu and Zn. The levels of Cu, Zn, and Pb in invertebrates from all ponds were less than dietary concentrations considered toxic to fish.     

Factor analysis of essential and toxic elements in human placentas from deliveries in arctic and subarctic areas of Russia and Norway

Concentrations in human placenta of 11 essential elements (P, Ca, Mg, Cu, S, Na, Fe, Zn, K, Se, Mn) and 5 toxic elements (Ba, Sr, Pb, Ni, Cd) are compared for each of two arctic communities in eastern Norway and western Russia, and for another in each country located at more southerly latitudes. All but Mg, Fe, P and K were present in higher concentrations in the Russian study group. The observed inter-element correlations are reflected by the four major factors identified in a principal component analysis. The total variation explained was 67.3%, of which more than half (35.3%) was contributed by Factor 1. P, Ca, Mg, Ba, Sr, Pb, and Ni were major contributors to this factor. The placental concentrations of these elements depended strongly on gestational age, increasing from about week 35 and peaking near weeks 39 and 40, and exhibited skewed frequency distributions and a dependence on maternal smoking. The gestational-dependent mineralization of the placenta is interpreted to reflect the deposition of metal phosphates coinciding with smoking-induced tissue damage. The loadings of the remaining three factors are reviewed in the context of common uptake mechanisms, similar biochemistries and unique transport pathways. The inter-element relationships and grouping of the elements observed should constitute a scientific base for the use of placenta composition in environmental monitoring and epidemiological studies.     

Simulation of Live and Dead Phytomass Formation and Transformation in Optimized Agrocenoses

The formation and transformation of live and dead phytomass in agrocenoses with a complex horizontal structure are described. These processes are demonstrated to be specific and to be determined by differences in the horizontal structure. Only agrocenoses of a mosaic structure (with square parcels) have optimal conditions for these processes.     

环境信息不对称对于循环经济的影响及其对策——兼谈环境信息服务业的发展与完善

指出循环经济背景下我国环境信息分布中的致命问题--环境信息的不对称分布,并指出不对称的表现,而后分析了环境信息对称对于循环经济的影响,在此基础上提出解决环境信息不对称的对策--发展环境信息服务业,并初步探讨了发展环境信息服务业的模式和步骤.     

区域相对资源承载力与可持续发展问题探讨——以济南长清区为例

以相对资源承载力的研究思路和方法，分别选取山东省和济南市作为参照区域，计算了1996-2003年长清区相对土地资源承载力、相对经济资源承载力和综合资源承载力及其动态变化过程。结果表明，该地区对自然资源的利用不够合理，经济发展缓慢；相对土地资源承载力和相对经济资源承载力不协调发展是其实现可持续发展面临的主要问题之一。