NONPARAMETRIC TEST PERFORMANCE FOR TRENDS IN WATER QUALITY WITH SAMPLING DESIGN APPLICATIONS1

ABSTRACT: In this paper four nonparametric tests for monotonic trend detection are compared with respect to their power and accuracy. The importance of comparing powers at equal empirical significance levels rather than nominal levels is stressed. Therefore, an appropriate graphical method is presented. The effect of the sampling frequency is also assessed using Monte Carlo simulations and a trajectory representation that visualizes the dynamics of the trade-off between the type I and type II errors. These methods are applied to compare four nonparametrical tests (seasonal Mann. Kendall, modified seasonal Mann-Kendall, covariance eigenvalue and covariance inversion) under several conditions. It is concluded with respect to the power that it is not worthwhile for the modified seasonal Mann-Kendall test applied to the AR(1) process considered in this paper to increase the sampling frequency from monthly to biweekly for detecting a monotonic trend of 5 percent, 10 percent, or 15 percent of the process variance. Under these conditions the seasonal Mann-Kendall test is highly liberal, while the covariance inversion and the covariance eigenvalue test are conservative. This research is situated in the development of an efficient sampling design for the Flemish water quality monitoring network.     

采空区火源位置探测技术现状及发展方向

概述了国内外采空区火源位置探测技术的现状,着重介绍了温度探测法、气体探测法、磁力探测法、数理解算法、电磁波探测法及电阻探测法等探测技术,并展望了国内外采空区火源位置探测技术的发展方向     

我国钢铁工业废水治理及其发展趋势

我国水资源人均拥有量仅为世界人均拥有量的四分之一，而且降水在时空分布上很不均衡。这一现实，决定了节省水资源，保护水环境是我国一项长期的战略任务。文章概要地叙述了钢铁工业废水治理及其发展过程。作者认为，要从根本上解决钢铁工业废水对水环境的污染与破坏，必须采取综合防治措施，并把整套循环用水技术引入生产工艺过程，使废水与污染物都作为资源加以回收，并实现循环利用。上述过程的实质，是模拟大自然生物圈循环运行     

湖北省荒山荒地资源开发利用的原则和方向

荒山荒地是我省农业的重要后备，本文将主要探讨这部分资源的开发利用及其原则和方向，为发展农业寻求新的途径与措施。     

REGIONAL SCALE TREND MONITORING OF INDICATORS OF TROPHIC CONDITION OF LAKES1

ABSTRACT: The U.S. Environmental Protection Agency has proposed a sample survey design to answer questions about the ecological condition and trends in condition of U.S. ecological resources. To meet the objectives, the design relies on a probability sample of the resource population of interest (e.g., a random sample of lakes) each year on which measurements are made during an index period. Natural spatial and temporal variability and variability in the sampling process all affect the ability to describe the status of a population and the sensitivity for trend detection. We describe the important components of variance and estimate their magnitude for indicators of trophic condition of lakes to illustrate the process. We also describe models for trend detection and use them to demonstrate the sensitivity of the proposed design to detect trends. If the variance structure that develops during the probability surveys is like that synthesized from available databases and the literature, then the trends in common indicators of trophic condition of the specified magnitude should be detectable within about a decade for Secchi disk transparency (0.5–1 percentiyear) and total phosphorus (2–3 percent/year), but not for chlorophyll-a (> 3–4 percent/year), which will take longer.     

TESTING FOR TREND IN LAKE AND GROUND WATER QUALITY TIME SERIES1

ABSTRACT: The detection of gradual trends in water quality time series is increasing in importance as concern grows for diffuse sources of pollution such as acid precipitation and agricultural non-point sources. A significant body of literature has arisen dealing with trend detection in water quality variables that exhibit seasonal patterns. Much of the literature has dealt with seasonality of the first moment. However, little has been mentioned about seasonality in the variance, and its effect upon the performance of trend detection techniques. In this paper, eight methods of trend detection that arise from both the statistical literature as well as the water quality literature have been compared by means of a simulation study. Varying degrees of seasonality in both the variances and the means have been introduced into the artificial data, and the performances of these procedures are analyzed. Since the focus is on lake and ground water quality monitoring, quarterly sampling and short to moderate record lengths are examined.     

Eutrophication of Buttermilk Bay,a cape cod coastal embayment: Concentrations of nutrients and watershed nutrient budgets

Nutrient concentrations in Buttermilk Bay, a coastal embayment on the northern end of Buzzards Bay, MA, are higher in the nearshore where salinities are lower. This pattern suggests that freshwater sources may contribute significantly to nutrient inputs into Buttermilk Bay. To evaluate the relative importance of the various sources we estimated inputs of nutrients by each major source into the watershed and into the bay itself. Septic systems contributed about 40% of the nitrogen and phosphorus entering the watershed, with precipitation and fertilizer use adding the remainder. Groundwater transported over 85% of the nitrogen and 75% of the phosphorus entering the bay. Most nutrients entering the watershed failed to reach the bay; uptake by forests, soils, denitrification, and adsorption intercepted two-thirds of the nitrogen and nine-tenths of the phosphorus that entered the watershed. The nutrients that did reach the bay most likely originated from subsoil injections into groundwater by septic tanks, plus some leaching of fertilizers.Buttermilk Bay water has relatively low nutrient concentrations, probably because of uptake of nutrients by macrophytes and because of relatively rapid tidal flushing. Annual budgets of nutrients entering the watershed showed a low nitrogen-to-phosphorus ratio of 6, but passage of nutrients through the watershed raised N/P to 23, probably because of adsorption of PO₄ during transit. The N/P ratio of water that leaves the watershed and presumably enters the bay is probably high enough to maintain active growth of nitrogenlimited coastal producers. There is a seasonal shift in N/P in the water column of Buttermilk Bay. N/P exceeded the 161 Redfield ratio during midwinter; the remainder of the year N/P fell below 161. This suggests that annual budgets do not provide sufficiently detailed data with which to interpret nutrient-limitation of producers. Further, some idea of water turnover is also needed to evaluate impact of loading rates. Urbanization of watersheds seems to increase loadings to nearshore environments, and to shift the nutrient loadings delivered to coastal waters to relatively high N-to-P ratios, potentially stimulating growth of nitrogen-limited primary producers.     

TECHNIQUES FOR DETECTING TRENDS IN LAKE WATER QUALITY1

ABSTRACT: With the advent of standards and criteria for water quality variables, there has been an increasing concern about the changes of these variables over time. Thus, sound statistical methods for determining the presence or absence of trends are needed. A Trend Detection Method is presented that provides: 1) Hypothesis Formulation - statement of the problem to be tested, 2) Data Preparation - selection of water quality variable and data, 3) Data Analysis - exploratory data analysis techniques, and 4) Statistical Tests - tests for detecting trends. The method is utilized in a stepwise fashion and is presented in a nonstatistical manner to allow use by those not well versed in statistical theory. While the emphasis herein is on lakes, the method may be adopted easily to other water bodies.     

湖泊富营养化评价的Euclid贴近度评价法──兼与《湖泊营养状态的Hamming贴近度评价法》作者商榷

针对湖泊富营养状态Ｈａｍｍｉｎｇ贴近度评价模型存在的“阈值漂移”问题,重新构造了评价参数隶属函数,提出了一种湖泊营养状态Ｅｕｃｌｉｄ贴近度评价模型,经过对全国２３个湖泊富营养状态的实例分析,证明这种评价模型结构合理,评价过程简单,模型通用性好。     

长江中下游地区地下水中铅元素的背景特征及其形成

根据调查结果，研究了长江中下游地区地下水铅元素的背景特征及其分布规律，并分析了地下水的含水介质成分，氧化还原环境，径流条件及酸碱度对铅元素的分布的影响。