On the use and error of approximation in the Domenico (1987) solution

A mathematical solution for solute transport in a three-dimensional porous medium with a patch source under steady-state, uniform ground water flow conditions was developed by Domenico (1987). The solution derivation strategy used an approximate approach to solve the boundary value problem, resulting in a nonexact solution. Variations of the Domenico (1987) solution are incorporated into the software programs BIOSCREEN and BIOCHLOR, which are frequently used to evaluate subsurface contaminant transport problems. This article mathematically elucidates the error in the approximation and presents simulations that compare different versions of the Domenico (1987) solution to an exact analytical solution to demonstrate the potential error inherent in the approximate expressions. Results suggest that the accuracy of the approximate solutions is highly variable and dependent on the selection of input parameters. For solute transport in a medium-grained sand aquifer, the Domenico (1987) solution underpredicts solute concentrations along the centerline of the plume by as much as 80% depending on the case of interest. Increasing the dispersivity, time, or dimensionality of the system leads to increased error. Because more accurate exact analytical solutions exist, we suggest that the Domenico (1987) solution, and its predecessor and successor approximate solutions, need not be employed as the basis for screening tools at contaminated sites.     

Effects of the construction of Scroby Sands offshore wind farm on the prey base of Little tern Sternula albifrons at its most important UK colony

Despite widespread interest in the impacts of wind farms upon birds, few researchers have examined the potential for indirect or trophic (predator-prey) effects. Using surface trawls, we monitored prey abundance before and after construction of a 30 turbine offshore wind farm sited close to an internationally important colony of Little terns. Observations confirmed that young-of-the-year clupeids dominated chick diet, which trawl samples suggested were mainly herring. Multivariate modelling indicated a significant reduction in herring abundance from 2004 onwards that could not be explained by environmental factors. Intensely noisy monopile installation during the winter spawning period was suggested to be responsible. Reduced prey abundance corresponded with a significant decline in Little tern foraging success. Unprecedented egg abandonment and lack of chick hatching tentatively suggested a colony-scale response in some years. We urge a precautionary approach to the timing and duration of pile-driving activity supported with long-term targeted monitoring of sensitive receptors.     

Pollutant impacts to Cape Hatteras National Seashore from urban runoff and septic leachate

The sandy barrier islands of Cape Hatteras National Seashore, USA, attract large seasonal influxes of tourists, and are host to numerous motels, rentals and second homes. To investigate the impacts of nearby urbanization on public trust waters, sampling was conducted in nine brackish water bodies within this coastal national park. A large tidal urban ditch delivered runoff-driven fecal-contaminated water directly into public beach waters. At all sites except the control, ammonium, phosphorus and fecal bacteria concentrations were high, strongly seasonal and significantly correlated with community water usage, indicating that increased septic tank usage led to increased pollutant concentrations in area waterways. Nutrients from septic systems caused ecosystem-level problems from algal blooms, BOD, and hypoxia while fecal microbes created potential human health problems. Septic system usage is widespread in sensitive coastal areas with high water tables and sandy soils and alternatives to standard septic systems must be required to protect human health and the environment.     

Heavy metal contamination in coastal sediments and soils near the Brazilian Antarctic Station, King George Island

This paper investigates the natural and anthropogenic processes controlling sediment chemistry in Admiralty Bay, King George Island, Antarctica, emphasizing the area affected by the Brazilian Antarctic Station Comandante Ferraz (Ferraz). Total and bioavailable concentrations of sixteen elements were determined in 32 sediment and 14 soils samples. Factor analysis allowed us to distinguish three groups of samples: (1) Ferraz sediments, with higher content of total trace metals and organic matter; (2) control sediments, with intermediate characteristics; (3) Ferraz soils, with higher bioavailability of most metals due to its oxidizing condition and low organic matter content. Major elements such as Fe, Al, Ca and Ti presented similar levels in all three groups. Enrichment factor calculations showed that paints, sewage and petroleum contamination enhanced metal concentrations in Ferraz surface sediments as follows: B, Mo, and Pb (>90%); V and Zn (70-80%); Ni, Cu, Mg, and Mn (30-40%). Despite evidence of contamination in these sediments, the low bioavailability, probably caused by iron-sulfide, indicates small environmental risks.     

Baseline metal concentrations in coastal Labrador sediments

Levels of Cr, Cu, Fe, Pb, Ni, and Zn in surface sediment from the Voisey's Bay area of coastal Labrador showed no evidence of recent anthropogenic input of metals. Metal concentrations in surface sediments, normalized to Li, fell within the 95% confidence limits of the background levels. Further analysis showed that the Li-metal regression lines from the surface sediments and sediments from 30-cm depth had the same slope and intercepts, suggesting that there was no difference in the metal content of the sediments at the two depths. Li-metal relationships can be used as a measure of the natural variability of the metal concentrations for the region and will serve as a baseline against which future anthropogenic affects may be assessed.     

借鉴国外,结合国情,谈谈我国测绘机制的更名

借鉴国外经验，结合本国实际，广泛征集意见，有助于选我国的测绘机构（院、系）更名后的合适名称。本文介绍国外测绘机构更名情况并分析其特点，揭示Ｇｅｏｍａｔｉｃｓ的本质内涵，最后简要谈测绘局和武汉测绘科技大学的更名。     

分形理论及其在测绘和其他领域中的应用

非线性科学是当今自然科学研究的尖端和前沿，而分形理论则是非线性科学研究的重要内容之一和分支新学科。近１０年来分形的理论和应用发展非常迅速。由于分形几乎无处不存在，自然界和人类社会遍布有它的足迹，所以其应用非常之广，在国外测绘刊物上偶尔可见一有关文章，我们测绘界只有少数学者在注视着这一新学科的发展，大部分人对它都非常陌生。为了让更多的测绘界同仁了解分形理论及其应用，笔者将以通俗的方式将曼德尔罗提出的