Effect of soil ageing on in vivo arsenic bioavailability in two dissimilar soils

Arsenic (As) bioavailability in spiked soils aged for up to 12 months was assessed using in vitro and in vivo methodologies. Ageing (natural attenuation) of spiked soils resulted in a decline in in vivo As bioavailability (swine assay) of over 75% in soil A (Red Ferrosol) but had no significant effect on in vivo As bioavailability even after 12 months of ageing in soil B (Brown Chromosol). Sequential fractionation, however, indicated that there was repartitioning of As within the soil fractions extracted during the time course investigated. In soil A, the As fraction associated with the more weakly bound soil fractions decreased while the residual fraction increased from 12% to 35%. In contrast, little repartitioning of As was observed in soil B indicating that natural attenuation may be only applicable for As in soils containing specific mineralogical properties.     

Physical and chemical properties of feedlot pen surfaces located on moderately coarse- and moderately fine-textured soils in southern Alberta

Southern Alberta has the highest density of feedlot cattle in Canada, and there is a concern that leaching of water and contaminants may be greater for feedlots located on coarser-textured than finer-textured soils. Our objective was to determine if infiltration and leaching were greater for a 4-yr-old feedlot located on a moderately coarse-textured (MC) soil compared with two feedlots located on moderately fine-textured (MF) soils (5- and 52-yr-old pens). Various soil physical properties of feedlot pen surfaces were measured, including field-saturated hydraulic conductivity (K(fs)) and near-saturated hydraulic conductivity at -0.9 and -3.9 cm water potential. Selected chemical properties of feedlot soil layers were measured, as well as the chloride content of the soil profile (0-100 cm). Mean K(fs), K(-0.9), and K(-3.9) values were not significantly (P > 0.10) greater at the MC site than the two MF sites, indicating no evidence of greater infiltration on coarser-textured soils. In addition, mean K(fs), K(-0.9), and K(-3.9) values of soils within feedlot pens at all three sites were significantly (P < or = 0.10) reduced by 46 to 78% compared with soil outside the pens. Depth of chloride accumulation was greatest at the 52-yr-old feedlot on MF soil (60-70 cm), followed by 4-yr-old feedlot on MC soil (40-50 cm) and 5-yr-old feedlot on MF soil (30-40 cm). Visual inspection determined that the black interface layer formed within 2 mo of cattle stocking at all three sites.     

A biome-scale assessment of the impact of invasive alien plants on ecosystem services in South Africa

This paper reports an assessment of the current and potential impacts of invasive alien plants on selected ecosystem services in South Africa. We used data on the current and potential future distribution of 56 invasive alien plant species to estimate their impact on four services (surface water runoff, groundwater recharge, livestock production and biodiversity) in five terrestrial biomes. The estimated reductions in surface water runoff as a result of current invasions were >3000 million m³ (about 7% of the national total), most of which is from the fynbos (shrubland) and grassland biomes; the potential reductions would be more than eight times greater if invasive alien plants were to occupy the full extent of their potential range. Impacts on groundwater recharge would be less severe, potentially amounting to approximately 1.5% of the estimated maximum reductions in surface water runoff. Reductions in grazing capacity as a result of current levels of invasion amounted to just over 1% of the potential number of livestock that could be supported. However, future impacts could increase to 71%. A ‘biodiversity intactness index’ (the remaining proportion of pre-modern populations) ranged from 89% to 71% for the five biomes. With the exception of the fynbos biome, current invasions have almost no impact on biodiversity intactness. Under future levels of invasion, however, these intactness values decrease to around 30% for the savanna, fynbos and grassland biomes, but to even lower values (13% and 4%) for the two karoo biomes. Thus, while the current impacts of invasive alien plants are relatively low (with the exception of those on surface water runoff), the future impacts could be very high. While the errors in these estimates are likely to be substantial, the predicted impacts are sufficiently large to suggest that there is serious cause for concern.     

Impediments and Solutions to Sustainable,Watershed-Scale Urban Stormwater Management: Lessons from Australia and the United States

In urban and suburban areas, stormwater runoff is a primary stressor on surface waters. Conventional urban stormwater drainage systems often route runoff directly to streams and rivers, thus exacerbating pollutant inputs and hydrologic disturbance, and resulting in the degradation of ecosystem structure and function. Decentralized stormwater management tools, such as low impact development (LID) or water sensitive urban design (WSUD), may offer a more sustainable solution to stormwater management if implemented at a watershed scale. These tools are designed to pond, infiltrate, and harvest water at the source, encouraging evaporation, evapotranspiration, groundwater recharge, and re-use of stormwater. While there are numerous demonstrations of WSUD practices, there are few examples of widespread implementation at a watershed scale with the explicit objective of protecting or restoring a receiving stream. This article identifies seven major impediments to sustainable urban stormwater management: (1) uncertainties in performance and cost, (2) insufficient engineering standards and guidelines, (3) fragmented responsibilities, (4) lack of institutional capacity, (5) lack of legislative mandate, (6) lack of funding and effective market incentives, and (7) resistance to change. By comparing experiences from Australia and the United States, two developed countries with existing conventional stormwater infrastructure and escalating stream ecosystem degradation, we highlight challenges facing sustainable urban stormwater management and offer several examples of successful, regional WSUD implementation. We conclude by identifying solutions to each of the seven impediments that, when employed separately or in combination, should encourage widespread implementation of WSUD with watershed-based goals to protect human health and safety, and stream ecosystems.     

Application of an in vivo swine model for the determination of arsenic bioavailability in contaminated vegetables

Considerable information is available in the literature regarding the uptake of arsenic (As) from contaminated soil and irrigation water by vegetables. However, few studies have investigated As speciation in these crops while a dearth of information is available on As bioavailability following their consumption. In this study, the concentration and speciation of As in chard, radish, lettuce and mung beans was determined following hydroponic growth of the vegetables using As-contaminated water. In addition, As bioavailability was assessed using an in vivo swine feeding assay. While As concentrations ranged from 3.0 to 84.2mg As kg(-1) (dry weight), only inorganic As (arsenite and arsenate) was detected in the edible portions of the vegetables. When As bioavailability was assessed through monitoring blood plasma As concentrations following swine consumption of As-contaminated vegetables, between 50% and 100% of the administered As dose was absorbed and entered systemic circulation. Arsenic bioavailability decreased in the order mung beans>radish>lettuce=chard.     

Performance of comprehensive first trimester fetal anatomy assessment

Objective

Ultrasound assessment of the fetal anatomy and fetal echocardiography are feasible in the first trimester of pregnancy. This study was designed to assess the performance of a comprehensive fetal anatomy assessment in a high-risk population at a tertiary fetal medicine unit.

Methods

A retrospective review of high-risk patients undergoing comprehensive fetal anatomy ultrasound assessment between 11 weeks and 13 + 6 weeks of gestation was conducted. Findings of the early anatomy ultrasound scan were compared with those of the second trimester anatomy scan, and birth outcomes or post-mortem results.

Results

Early anatomy ultrasounds were performed in 765 patients. The sensitivity of the scan for detecting fetal anomalies compared to the birth outcome was 80.5% (95% CI 73.5–86.3) and specificity was 93.1% (95%CI 90.6–95.2). Positive and negative predictive values were 78.5% (95% CI 71.4–84.6) and 93.9% (95% CI 91.4–95.8), respectively. The most missed and overdiagnosed abnormalities were ventricular septal defects. The second trimester ultrasound had sensitivity of 69.0% (95% CI 55.5–80.5) and specificity of 87.5% (95% CI 84.3–90.2).

Conclusions

In a high-risk population, early assessments had similar performance metrics as the second trimester anatomy ultrasound. We advocate for a comprehensive fetal assessment in the care of high-risk pregnancies.