Normalization procedures for sediment contaminants in spatial and temporal trend monitoring

Rational pollution, or the effectiveness of natural attenuation assessments based upon estimating the degree of contamination, critically depends on the basis of a sound normalization to take into account heterogeneous sedimentary environments. By normalizing the measured contaminant concentration patterns for the sediment characteristics, the inherent variability can be reduced and so allow a more meaningful assessment of both the spatial distributions and the temporal trends. A brief overview and guidance in the methodology available for choosing an appropriate site-specific normalization approach is presented. This is followed by general recommendations with respect to the choice of normalizer and the necessary geochemical and statistical quality assurance methods, with support from the results of recent international intercomparison exercises within the QUASH (Quality Assurance of Sample Handling) programme, as well as discussions within the International Commission on the Exploration of the Sea (ICES) working groups. The most important of these recommendations is the use of a two-tiered normalization approach including wet sieving (<63 microm), followed by an additional geochemical co-factor normalization.     

An innovative statistical approach for analysing non-continuous variables in environmental monitoring: assessing temporal trends of TBT pollution

The current work presents an innovative statistical approach to model ordinal variables in environmental monitoring studies. An ordinal variable has values that can only be compared as "less", "equal" or "greater" and it is not possible to have information about the size of the difference between two particular values. The example of ordinal variable under this study is the vas deferens sequence (VDS) used in imposex (superimposition of male sexual characters onto prosobranch females) field assessment programmes for monitoring tributyltin (TBT) pollution. The statistical methodology presented here is the ordered logit regression model. It assumes that the VDS is an ordinal variable whose values match up a process of imposex development that can be considered continuous in both biological and statistical senses and can be described by a latent non-observable continuous variable. This model was applied to the case study of Nucella lapillus imposex monitoring surveys conducted in the Portuguese coast between 2003 and 2008 to evaluate the temporal evolution of TBT pollution in this country. In order to produce more reliable conclusions, the proposed model includes covariates that may influence the imposex response besides TBT (e.g. the shell size). The model also provides an analysis of the environmental risk associated to TBT pollution by estimating the probability of the occurrence of females with VDS ≥ 2 in each year, according to OSPAR criteria. We consider that the proposed application of this statistical methodology has a great potential in environmental monitoring whenever there is the need to model variables that can only be assessed through an ordinal scale of values.     

Trace metal and total suspended solids concentrations in freshwater: the importance of small-scale temporal variation

The temporal variation in the concentrations of particulate trace metals (Cu, Pb and Zn) and total suspended solids (TSS) was examined in three rivers that drain into the Port Jackson estuary, Australia, using a nested, hierarchical sampling design. Sampling was conducted between March and June 1999, under low flow conditions. The sampling design incorporated four temporal scales (hours, days, weeks and months). It was considered that hours, days, weeks and months were representative of such time scales and could be analyzed as random, nested sources of variation in an analysis of variance (ANOVA). Significant variation was found at temporal scales ranging from hours, within the same day, to months. The amount and scales of variation differed between particulate trace metals and TSS concentrations and between rivers. In many cases, differences between small-scale were as important as differences between months. The results suggest that higher anthropogenic influences cause higher variability at small temporal scale. Results indicate the need for nested sampling designs to be incorporated into studies of temporal variation in order to unconfound small-scale temporal variation. The conclusions of this study are likely to be applicable to other water quality variables and pollutants.     

An analysis of spatial and temporal properties of daily sulfate, nitrate and chloride concentrations at UK urban and rural sites

Daily measurements of sulfate, nitrate and chloride in PM(10) have been made at three geographically separated UK sites over a three year period. Chloride shows a clear seasonal pattern with highest concentrations in winter, whilst sulfate and nitrate both show highest concentrations in the spring, apparently related to weather patterns. Spatial variability of both sulfate and nitrate is low in comparison to temporal variations, with high correlations of both species between all three sites, London (North Kensington), Harwell and Belfast, despite a geographic separation of 510 km. Both SO/SO(2) and NO/NO(x) ratios are considerably higher in summer than winter, reflecting a greater oxidising capacity of the atmosphere. SO(4)(2-)/NO(3)(-) ratios are higher in summer than winter, suggesting that aqueous phase oxidation of SO(2), expected to be most important in the winter months is not appreciably influencing production of sulfate aerosol, although greater dissociation of ammonium nitrate in summer may also play a role. Regression of concentrations at London, North Kensington with those from the proximate rural site of Harwell is interpreted as showing a similar effect of regional transport at the two sites and a small influence of local formation in the urban atmosphere or primary emissions, averaging 0.46 microg m(-3) of nitrate and 0.22 microg m(-3) of sulfate.     

Groundwater quality and water quality index at Bhandara District

The present investigation reports the results of a monitoring study focusing on groundwater quality of Bhandara District of central India. Since, remediation of groundwater is very difficult, knowledge of the existing nature, magnitude, and sources of the various pollution loads is a prerequisite to assessing groundwater quality. The water quality index (WQI) value as a function of various physicochemical and bacteriological parameters was determined for groundwater obtained from a total of 21 locations. The WQI during pre-monsoon season varied from 68 to 83, while for post-monsoon, it was between 56 and 76. Significantly (P < 0.01) lower WQI for the post-monsoon season was observed, indicating deterioration of the groundwater overall in corresponding season. The study revealed that groundwater from only 19% locations was fit for domestic use, thus indicating the need of proper treatment before use.     

Economics of place-based monitoring under the safe drinking water act, part I: spatial and temporal patterns of contaminants, and design of screening strategies

The goals of environmental legislation and associated regulations are to protect public health, natural resources, and ecosystems. In this context, monitoring programs should provide timely and relevant information so that the regulatory community can implement legislation in a cost-effective and efficient manner. The Safe Drinking Water Act (SDWA) of 1974 attempts to ensure that public water systems (PWSs) supply safe water to its consumers. As is the case with many other federal environmental statutes, SDWA monitoring has been implemented in relatively uniform fashion across the USA. In this three part series, spatial and temporal patterns in water quality data are utilized to develop, compare, and evaluate the economic performance of alternative place-based monitoring approaches to current monitoring practice. Under the Safe Drinking Water Act (SDWA), a common list of over 90 contaminants is analyzed nationwide using EPA-authorized laboratory procedures. National and state-level summaries of SDWA data have shown that not all contaminants occur in all places at all times. This hypothesis is confirmed and extended by showing that only a few (less than seven) contaminants are of concern in any one of 19 Iowa surface water systems studied. These systems collectively serve about 350,000 people and their sizes vary between 1,200 and 120,000. The distributions of contaminants found in these systems are positively skewed, with many non-detect measurements. A screening strategy to identify such contaminants in individual systems is presented. These findings have significant implications not only for the design of alternative monitoring programs, but also in multi-billion-dollar decisions that influence the course of future drinking water infrastructure, repair, and maintenance investments.     

Groundwater monitoring in the context of EU legislation: reality and integration needs

A wide range of environmental policies are based on the monitoring of chemical and/or biological parameters which are used to evaluate the environmental status of relevant compartments (e.g. water, soil, air) with the ultimate aim of making appropriate management decisions. The soundness of policy decisions is therefore directly related to the reliability of the environmental monitoring programmes. Monitoring reliability in turn is predominantly linked to scientific and technological progress. Hence a correct design, development and implementation process of environmental policies is, at least in part, dependent upon a proper integration of scientific and technological advances (in monitoring, but also for all kinds of permit procedures, remediation strategies etc.). This paper examines science-policy integration needs in support of groundwater environmental monitoring, with focus on on-going policy developments. The article aims to summarise key information on groundwater policy and EU scientific developments to raise awareness of the scientific community involved in this issue and to enhance communication among scientists and policy-makers.     

Modelling temporal and spatial changes of PCBs in fish tissue from Lake Huron

A model has been developed to assess temporal and spatial changes in the concentration of polychlorinated biphenyl (PCB) contaminant in whole fish from Lake Huron during the years 1980 to 2004. The model uses log PCB concentration as the response variable and includes time trend, within-lake variability and dependence on age, weight and length as explanatory variables. A preliminary examination of the data revealed that some values are recorded as below detection limits (thus leading to the left censoring), and the PCB concentration appears to show declines in latter years. To this end, parametric log-location-scale regression models used in survival analysis were employed. It has been found that the Weibull model yields a better fit than the log-logistic or the log-normal models. The analysis provides strong evidence that, starting in 1996, the level of PCB concentration showed steady decline, which is most contributed by the Canadian and US governments?? actions carried out earlier to reduce the load of toxic contaminants to the Great Lakes. Spatially, fish from the north of the lake is less contaminated than fish from the south. The pattern and magnitude of the estimated spatial and temporal trends can provide useful information regarding the safety of fish consumption, the setting of regularity limits, the identifiability of PCB sources and the effects of remedial actions in the future. In addition, the developed model is not restricted to the current application but could be used for the analysis of other contaminants.     

Baseline of the spatial and temporal metal contamination in Dilek National Park, Turkey

Dilek National Park in Western Turkey is a protected habitat for several endangered and threatened species. In an attempt to protect the endangered species, the park was classified as a World Heritage Preserve. Even with this change, the animal and flora variety are still at risk from previous metal contamination. Water samples were collected 10 cm below the water surface and sediment from 0-30 and 30-60 cm depth. Inorganic elements were found in all sediment samples. Sodium had the highest aqueous concentration (10,312 mg/L), while Cu, Fe, Mn, and Zn were present at levels significantly lower than the chronic exposure criteria. Zn was the least prevalent (0.4 mg/kg) compound found in the sediment. The highest toxic contaminant concentration was Mg at an average of 1,100 mg/kg. The main contamination source of that seems to be Great Meandrous River. More studies are needed to develop a protection and remediation strategy for Dilek National Park.     

Evaluation of spatial and temporal variations in marine sediments quality using multivariate statistical techniques

Spatial and temporal variations of sediment quality in Matanzas Bay (Cuba) were studied by determining a total of 12 variables (Zn, Cu, Pb, As, Ni, Co, Al, Fe, Mn, V, CO₃ ^2?, and total hydrocarbons (THC). Surface sediments were collected, annually, at eight stations during 2005–2008. Multivariate statistical techniques, such as principal component (PCA), cluster (CA), and lineal discriminant (LDA) analyses were applied for identification of the most significant variables influencing the environmental quality of sediments. Heavy metals (Zn, Cu, Pb, V, and As) and THC were the most significant species contributing to sediment quality variations during the sampling period. Concentrations of V and As were determined in sediments of this ecosystem for the first time. The variation of sediment environmental quality with the sampling period and the differentiation of samples in three groups along the bay were obtained. The usefulness of the multivariate statistical techniques employed for the environmental interpretation of a limited dataset was confirmed.     

A survey on the temporal and spatial distribution of perchlorate in the Potomac River

Samples of river water and treated drinking water were obtained from eight sites along the Potomac River between western Maryland and Washington DC. Samples were collected each month from October 2007 to September 2008 and analyzed for perchlorate by ion chromatography/mass spectrometry. Data on anions were also collected for seven of the twelve months. Data were analyzed to identify spatial and temporal patterns for the occurrence of perchlorate in the Potomac. Over the year of sampling, the largest monthly increase occurred from June to July, with levels then decreasing from July to September. Samples from the period between December and May had lower perchlorate concentrations, relative to the remainder of the study year. Spatially, higher levels of perchlorate were found at sites located in west-central Maryland, the eastern panhandle of West Virginia, and central northern Virginia, with levels decreasing slightly as the Potomac approaches Washington DC. Within the sampling boundaries, river (untreated) water perchlorate concentrations ranged from 0.03 μg L(-1) to 7.63 μg L(-1), averaged 0.67 ± 0.97 μg L(-1) over the year-long period and had a median value of 0.37 μg L(-1). There was no evidence that any of the existing drinking water treatment technologies at the sampling sites were effective in removing perchlorate. There were no correlations found between the presence of perchlorate and any of the anions or water quality parameters examined in the source water with the exception of a weak positive correlation with water temperature. Results from the summer (June-August) and fall (September-November) months sampled in this study were generally higher than from the winter and spring months (December-May). All but one of the locations had annual average perchlorate levels below 1 μg L(-1); however, 7 of the 8 sites sampled had river water perchlorate detections over 1 μg L(-1) and 5 of the 8 sites had treated water detections over this level.     

Measurement instability and temporal bias in chemical soil monitoring: sources and control measures

Concern that human impacts on the environment may be harmful to natural resources such as soils as well as to living conditions is the major motivation for long-term environmental monitoring. However, the evidence that measurement bias is not constant through time affects time series as an artifact; this also holds true for chemical soil monitoring. Measurement instabilities occur along the whole measurement chain, from soil sampling to the expression of results. The first step in controlling measurement instability is to identify its relevant sources, and the second is to control it by stabilizing, minimizing, or quantifying measurement instability. For all five steps in the measurement process, from soil sampling to the expression of the analytical results, sources of measurement instability are identified and measures of control discussed, leading to the main conclusion concerning the requirement to continuously control the relevant environmental and measurement boundary conditions that may affect measurement instability. The innovative aspect of this paper consists in explicitly addressing measurement instability in chemical soil monitoring and tracking it along the whole measurement chain. The paper is also a plea for a change of paradigm in long-term environmental monitoring, namely to consider temporal measurements as unstable unless their degree of stability is traceably demonstrated, adequately quantified, and included in interpretation.     

An innovative approach to inventory and monitoring of natural resources in the Mexican State of Jalisco

This paper discusses the statistical design and estimation processes developed for the assessment of key land resources relevant to questions of their condition and change in the State of Jalisco, Mexico. Some initial results of the first phase of Jalisco's Natural Resource Inventory and Monitoring Program (IMRENAT) conducted in 2006 are presented and discussed. Since this is a relatively new approach for an inventory and monitoring program of this magnitude, designed from the beginning specifically for integration with orbital satellite data, it is anticipated that changes will have to be made over time to improve conceptual and operational design aspects. Alternative remote sensing capabilities to further improve local information, more sophisticated analysis to satisfy the requirements of officials as they become more aware of the capabilities of the system, possible improvements in change assessments over time, and opportunities to focus on specific interesting changes will be assessed. As this study indicates, current and future information technology advancements provide a solid prospect for the development and application of integrative sampling strategies to support sustainability science and management processes.     

Analysis of spatial and temporal water pollution patterns in Lake Dianchi using multivariate statistical methods

Various multivariate statistical methods including cluster analysis (CA), discriminant analysis (DA), factor analysis (FA), and principal component analysis (PCA) were used to explain the spatial and temporal patterns of surface water pollution in Lake Dianchi. The dataset, obtained during the period 2003–2007 from the Kunming Environmental Monitoring Center, consisted of 12 variables surveyed monthly at eight sites. The CA grouped the 12 months into two groups, August–September and the remainder, and divided the lake into two regions based on their different physicochemical properties and pollution levels. The DA showed the best results for data reduction and pattern recognition in both temporal and spatial analysis. It calculated four parameters (TEMP, pH, COD_Mn, and Chl-a) to 85.4% correct assignment in the temporal analysis and three parameters (BOD, NH 2009/11/20Heavy metals (Cd, Cu, Fe, Mn and Zn) concentrations were determined in different tissues (muscle, kidney, liver, brain, gonads, heart and feathers) of Glaucous Gulls (Larus hyperboreus) from Bjørnøya and Jan Mayen. The age and spatial dependent variations in heavy metals were quantified and interpreted in view of the three chemometric techniques, i.e. non-parametric Mann–Whitney U test, redundancy gradient analysis and detrended correspondence analysis. The Glaucous Gulls from Bjørnøya contained significantly higher (p?<?0.05) levels of Cd, Cu and Zn than those inhabited Jan Mayen. Adult birds were characterized by greater (p?<?0.01) concentration of muscle, hepatic and renal heavy metals in comparison to chicks. Insignificantly higher slope constant Zn/Cd for the liver than for the kidney may reflect insignificant Cd exposure. Estimate of transfer factor (TF) allows us to assess variations in heavy metal concentrations during the individual development of Glaucous Gulls. It may be stated that there is a distinct increase of bioaccumulation of all the studied metals during subsequent stages of the bird life.     

Site location optimization of regional air quality monitoring network in China: methodology and case study

Regional air quality monitoring networks (RAQMN) are urgently needed in China due to increasing regional air pollution in city clusters, arising from rapid economic development in recent decades. This paper proposes a methodological framework for site location optimization in designing a RAQMN adapting to air quality management practice in China. The framework utilizes synthetic assessment concentrations developed from simulated data from a regional air quality model in order to simplify the optimal process and to reduce costs. On the basis of analyzing various constraints such as cost and budget, terrain conditions, administrative district, population density and spatial coverage, the framework takes the maximum approximate degree as an optimization objective to achieve site location optimization of a RAQMN. An expert judgment approach was incorporated into the framework to help adjust initial optimization results in order to make the network more practical and representative. A case study was used to demonstrate the application of the framework, indicating that it is feasible to conduct site optimization for a RAQMN design in China. The effects of different combinations of primary and secondary pollutants on site location optimization were investigated. It is suggested that the network design considering both primary and secondary pollutants could better represent regional pollution characteristics and more extensively reflect temporal and spatial variations of regional air quality. The work shown in this study can be used as a reference to guide site location optimization of a RAQMN design in China or other regions of the world.     

Brominated flame retardants in the environment of Asia-Pacific: an overview of spatial and temporal trends

In this paper, we summarize spatial and temporal trends of polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecanes (HBCDs) in coastal and marine biota, and further assess human exposure to these brominated flame retardants (BFRs) in Asia-Pacific. The review is based mainly on the studies that were conducted in our laboratory and utilized samples archived in the environmental specimen bank (es-BANK) of Ehime University, Japan. The studies suggest that the target BFRs are ubiquitous in the environment of Asia-Pacific. Examination of spatial trends reveals that concentrations of these contaminants are relatively high in samples from Korea, South China and Japan. In general, the magnitude of environmental contamination by PBDEs in Asia-Pacific, as well as human exposure to these contaminants, seem to be comparable to or slightly higher than in Europe, but lower than in North America. Evaluation of temporal trends in concentrations of BFRs in marine mammals from the coastal waters of Japan and China showed drastic increase during the last 30 years. These changes in BFR levels in samples from Japan were in line with trends in production/use of the commercial formulations. Since the withdrawal of some PBDE products from the Japanese market in the 1990s, concentrations of HBCDs appear to exceed those of PBDEs, reflecting increasing usage of HBCDs over PBDEs. The increasing environmental contamination by BFRs in Chinese coastal waters indicates that contamination by BFRs has already become evident, even in developing countries. In view of the rising environmental levels and the high consumption volume of BFRs in Asia, further efforts should be made to monitor environmental contamination by these chemicals in order to identify sources and reduce emissions.     

High-frequency measurements reveal spatial and temporal patterns of dissolved organic matter in an urban water conveyance

Stormwater runoff in urban areas can contribute high concentrations of dissolved organic matter (DOM) to receiving waters, potentially causing impairment to the aquatic ecosystem of urban streams and downstream water bodies. Compositional changes in DOM due to storm events in forested, agricultural, and urban landscapes have been well studied, but in situ sensors have not been widely applied to monitor stormwater contributions in urbanized areas, leaving the spatial and temporal characteristics of DOM within these systems poorly understood. We deployed fluorescent DOM (FDOM) sensors at upstream and downstream locations within a study reach to characterize the spatial and temporal changes in DOM quantity and sources within an urban water conveyance that receives stormwater runoff. Baseflow FDOM decreased over the summer season as seasonal flows upstream transported less DOM. FDOM fluctuated diurnally, the amplitude of which also declined as the summer season progressed. During storms, FDOM concentrations were rapidly elevated to values orders of magnitude greater than baseflow measurements, with greater concentrations at the downstream monitoring site, revealing high contributions from stormwater outfalls between the two locations. Observations from custom, in situ fluorometers resembled results obtained using laboratory methods for identifying DOM source material and indicated that DOM transitioned to a more microbially derived composition as the summer season progressed, while stormwater contributions contributed DOM from terrestrial sources. Deployment of a mobile sensing platform during varying flow conditions captured spatial changes in DOM concentration and composition and revealed contributions of DOM from outfalls during stormflows that would have otherwise been unobserved.     

Comparison of spatial interpolation methods for soil moisture and its application for monitoring drought

Soil moisture data can reflect valuable information on soil properties, terrain features, and drought condition. The current study compared and assessed the performance of different interpolation methods for estimating soil moisture in an area with complex topography in southwest China. The approaches were inverse distance weighting, multifarious forms of kriging, regularized spline with tension, and thin plate spline. The 5-day soil moisture observed at 167 stations and daily temperature recorded at 33 stations during the period of 2010–2014 were used in the current work. Model performance was tested with accuracy indicators of determination coefficient (R ²), mean absolute percentage error (MAPE), root mean square error (RMSE), relative root mean square error (RRMSE), and modeling efficiency (ME). The results indicated that inverse distance weighting had the best performance with R ², MAPE, RMSE, RRMSE, and ME of 0.32, 14.37, 13.02%, 0.16, and 0.30, respectively. Based on the best method, a spatial database of soil moisture was developed and used to investigate drought condition over the study area. The results showed that the distribution of drought was characterized by evidently regional difference. Besides, drought mainly occurred in August and September in the 5 years and was prone to happening in the western and central parts rather than in the northeastern and southeastern areas.     

Assessment of temporal and spatial water quality in international Gomishan Lagoon,Iran, using multivariate analysis

Coastal lagoon ecosystems are vulnerable to eutrophication, which leads to the accumulation of nutrients from the surrounding watershed over the long term. However, there is a lack of information about methods that could accurate quantify this problem in rapidly developed countries. Therefore, various statistical methods such as cluster analysis (CA), principal component analysis (PCA), partial least square (PLS), principal component regression (PCR), and ordinary least squares regression (OLS) were used in this study to estimate total organic matter content in sediments (TOM) using other parameters such as temperature, dissolved oxygen (DO), pH, electrical conductivity (EC), nitrite (NO₂), nitrate (NO₃), biological oxygen demand (BOD), phosphate (PO₄), total phosphorus (TP), salinity, and water depth along a 3-km transect in the Gomishan Lagoon (Iran). Results indicated that nutrient concentration and the dissolved oxygen gradient were the most significant parameters in the lagoon water quality heterogeneity. Additionally, anoxia at the bottom of the lagoon in sediments and re-suspension of the sediments were the main factors affecting internal nutrient loading. To validate the models, R², RMSECV, and RPDCV were used. The PLS model was stronger than the other models. Also, classification analysis of the Gomishan Lagoon identified two hydrological zones: (i) a North Zone characterized by higher water exchange, higher dissolved oxygen and lower salinity and nutrients, and (ii) a Central and South Zone with high residence time, higher nutrient concentrations, lower dissolved oxygen, and higher salinity. A recommendation for the management of coastal lagoons, specifically the Gomishan Lagoon, to decrease or eliminate nutrient loadings is discussed and should be transferred to policy makers, the scientific community, and local inhabitants.