Bayesian spatial modeling of Lavaca Bay pollutants

Locational risk of increased mercury and PAH concentrations in Lavaca Bay, Texas sediments and eastern oysters (Crassostrea virginica) harvested from Lavaca Bay, Texas were analysed. Chemical analysis results were evaluated utilizing Bayesian geo-statistical methods for comparison of the model fit of a random effects model versus a convoluted model which included both random and spatial effects. For those results fit best with the convoluted model, continuous surface maps of predicted parameter values were created. Sediment and oyster concentrations of mercury and the majority of measured PAHs were fit best with the convoluted model. The locational risks of encountering elevated concentrations of these pollutants in Lavaca Bay sediments and oysters were highest in close proximity to industrial facilities.     

Embryotoxic and genotoxic effects of heavy metals and pesticides on early life stages of Pacific oyster (Crassostrea gigas)

This study evaluated embryotoxicity and genotoxicity of two dissolved metals copper and cadmium (Cu and Cd) and two pesticides (metolachlor and irgarol) occurring in Arcachon Bay (SW France) in Pacific oyster (Crassostrea gigas) larvae and investigated the relationship between those two endpoints. Embryotoxicity was measured by calculating the percentage of abnormal D-shaped larvae and genotoxicity was evaluated with DNA strand breaks using the comet assay. After 24 h exposure, significant increases of the percentage of abnormal D-larvae and the DNA strand breaks were observed from 0.1 μg L⁻¹ for Cu, 10 μg L⁻¹ for Cd and 0.01 μg L⁻¹ for both irgarol and metolachlor in comparison with the controls. A strong positive relationship between embryotoxicity and genotoxicity was recorded for Cu, Cd and metolachlor. The current study suggests that copper, irgarol and metolachlor can induce larval abnormalities and DNA damage in a population of exposed oysters at environmentally relevant concentrations.     

Eastern oyster (Crassostrea virginica) δN as a bioindicator of nitrogen sources: Observations and modeling

Stable nitrogen isotopes (δ¹⁵N) in bioindicators are increasingly employed to identify nitrogen sources in many ecosystems and biological characteristics of the eastern oyster (Crassostrea virginica) make it an appropriate species for this purpose. To assess nitrogen isotopic fractionation associated with assimilation and baseline variations in oyster mantle, gill, and muscle tissue δ¹⁵N, manipulative fieldwork in Chesapeake Bay and corresponding modeling exercises were conducted. This study (1) determined that five individuals represented an optimal sample size; (2) verified that δ¹⁵N in oysters from two locations converged after shared deployment to a new location reflecting a change in nitrogen sources; (3) identified required exposure time and temporal integration (four months for muscle, two to three months for gill and mantle); and (4) demonstrated seasonal δ¹⁵N increases in seston (summer) and oysters (winter). As bioindicators, oysters can be deployed for spatial interpolation of nitrogen sources, even in areas lacking extant populations.     

Experimental Measurement of P-wave Attenuation Due to Fractures Over the 100 to 300 kHz Bandwidth

— A series of experiments was conducted where rock core specimens were cyclically loaded to 50?MPa uniaxial stress while P waveforms were pulsed along the core axis. Some of these specimens were intact while others were prepared with a single through-going tensile fracture oriented perpendicular to the core axis. Recorded data was processed to determine Q, velocity and fracture closure. Results indicated that Q was constant over the studied bandwidth and Q for the fractured specimens decreased relative to the intact specimens as fracture stress decreased. Observed variations in static fracture stiffness among the tested specimens did not result in corresponding variations in Q. Velocity results showed similar trends. This work was done to provide comparative data for related field studies examining the feasibility of using attenuation measurements in comparable frequency bands to indicate the potential for roof failure during excavation in fractured rock masses.     

Homogenization of the transport behavior of nonlinearly adsorbing pollutants in physically and chemically heterogeneous aquifers

This paper addresses the question of how spatial variability in the hydraulic and chemical properties of groundwater systems affects the transport and sorption behavior of pollutants at the field scale. In this paper, we limit our investigations on pollutants that adsorb according to an equilibrium controlled nonlinear Freundlich sorption isotherm. The new contribution of this paper is take into account not only spatially variable Freundlich distribution coefficients _KS$K_S$ but spatially variable Freundlich nonlinearity parameters p as well. Using a homogenization theory approach, we shortly review the impact of spatially variable hydraulic properties on the transport and extend the theory to spatially variable chemical properties. We show that spatially variable Freundlich exponents cause a very different field scale transport and sorption behavior than spatial variations in the distribution coefficients only since in the first case field scale Freundlich parameters and field scale dispersion coefficients become concentration dependent. In particular, field scale retardation is much larger than small-scale retardation.     

Sediment concentrations of heavy metals in the Homa Lagoon (Eastern Aegean Sea): Assessment of contamination and ecological risks

The concentrations of heavy metals and organic carbon in sediment of the Homa Lagoon which is one of the most productive lagoons and commercial important active fish trap in the Eastern Aegean Sea, were investigated in order to describe the temporal and spatial distributions of metals. These results were used to evaluate possible ecological risks that could be a problem for the environment of the lagoon in the future. Sediments were enriched with Cr, Ni and considered as heavily polluted per the SQG. The C_f of Ni and Cr were presented moderate level of contamination in this area. The C_d levels indicated moderate degree of contamination at station B, C, D and E due to agricultural drainage water, industrial and domestic wastewater, are transported by the Gediz River. Sediments from Homa Lagoon were most toxic for Ni due to exceedances of the TEL and PEL values.     

鲁东地区视应力时空变化特征分析

利用山东数字地震台网记录到的山东东部地区2008年以来的地震波形资料,在去除地震序列的余震之后,采用Brune模型,并结合遗传算法反演计算了225 次Mr≥2. 0地震的视应力,讨论了视应力与震级的关系,分析研究了视应力的时空变化特征,并通过视应力的时空变化来研究该区应力状态的特征。结果表明:鲁东地区中小地震的视应力范围在0.06~3.91 MPa,平均应力水平在0.31 MPa,可作为该区的背景应力水平;视应力与震级呈正相关关系,随震级的增加而升高,利用稳态回归拟合初步得到适合于该区的定量统计关系;计算的视应力值减去由震级得到的理论视应力,去除震级的相关性干扰,得到差视应力,能更真实的反应该地区的应力变化特征;视应力的时间变化显示鲁东地区目前正处于应力的积累增强阶段,可能与近期鲁东地区震群频发有关;空间分布显示目前高视应力集中区主要分布在沂沭断裂带安丘段附近和烟台附近地区,对于山东地区年度危险区的判定有一定意义。     

Stress-strain state of the lithosphere in the southern Baikal region and northern Mongolia from data on seismic moments of earthquakes

Investigation and understanding of the present-day geodynamic situation are of key importance for the elucidation of the laws and evolution of the seismic process in a seismically active region. In this work, seismic moments of nearly 26000 earthquakes with K _p ≥ 7 (M _LH ≥ 2) that occurred in the southern Baikal region and northern Mongolia (SBNM) (48°–54°N, 96°–108°E) from 1968 through 1994 are determined from amplitudes and periods of maximum displacements in transverse body waves. The resulting set of seismic moments is used for spatial-temporal analysis of the stress-strain state of the SBNM lithosphere. The stress fields of the Baikal rift and the India-Asia collision zone are supposed to interact in the region studied. Since the seismic moment of a tectonic earthquake depends on the type of motion in the source, seismic moments and focal mechanisms of earthquakes belonging to four long-term aftershock and swarm clusters of shocks in the Baikal region were used to “calibrate” average seismic moments in accordance with the source faulting type. The study showed that the stress-strain state of the SBNM lithosphere is spatially inhomogeneous and nonstationary. A space-time discrepancy is observed in the formation of faulting types in sources of weak (K _p = 7 and 8) and stronger (K _p ≥ 9) earthquakes. This discrepancy is interpreted in terms of rock fracture at various hierarchical levels of ruptures on differently oriented general, regional, and local faults. A gradual increase and an abrupt, nearly pulsed, decrease in the vertical component of the stress field S _v is a characteristic feature of time variations. The zones where the stress S _v prevails are localized at “singular points” of the lithosphere. Shocks of various energy classes in these zones are dominated by the normal-fault slip mechanism. For earthquakes with K _p = 9, the source faulting changes with depth from the strike-slip type to the normal-strike-slip and normal types, suggesting an increase in S _v . On the whole, the results of this study are well consistent with the synergism of open unstable dissipative systems and are usable for interpreting the main observable variations in the stress-strain state of the lithosphere in terms of spatiotemporal variations in the vertical component of the stress field S _v . This suggests the influence of rifting on the present-day geodynamic processes in the SBNM lithosphere.     

Spatial and temporal variations in nutrient and chlorophyll-a concentrations in the northern East China Sea surrounding Cheju Island

Nutrients, chlorophyll-a (Chl-a), and environmental conditions were extensively investigated in the northern East China Sea (ECS) near Cheju Island during five research cruises from 2003 to 2007. In the eastern part of the study area, surface waters were characterized only by the Tsushima Current Water (TCW) during all five cruises. However, the western surface waters changed with season and were characterized by the Yellow Sea Cold Water (YSCW) in spring, the Changjiang Diluted Water (CDW) in summer, and the Yellow Sea Mixed Water (YSMW) in autumn. In spring and autumn, relatively high concentrations of nitrate and phosphate were observed in the surface waters in the western part of the study area, where vertical mixing brought large supplies of nutrients from deep waters. Changes in wind direction occasionally varied the inflow of the Changjiang plume in summer, clearly causing the annual variation in surface nitrate and phosphate concentrations in summer. In summer, the surface distribution of nitrate and phosphate did not coincide with that of silicate in the study area, which probably resulted from the significant drop in the Si:N ratio in the Changjiang plume since construction of the Three Gorges Dam (TGD). Despite large temporal and spatial variations in surface Chl-a concentrations, depth-integrated Chl-a concentrations exhibited little variation temporally and spatially. In the study area, surface Chl-a concentration did not well reflect the standing stocks of phytoplankton. The vertical distribution of Chl-a showed large temporal and spatial variations, and the main factor controlling the vertical distribution of Chl-a in summer was the availability of nitrate. The thermohaline front may play an important role for accumulation of phytoplankton biomass in spring and autumn.     

By-products of oxidative biocides: Toxicity to oyster larvae

Selected by-products which are produced upon chlorination or ozonization of seawater were examined for their effect on eastern oyster (Crassostrea virginica) larvae. The compounds, bromate, bromoform, and chloroform, were studied at 0.05, 0.1, 1.0, and 10.0 mg/l. Repeated bioassays indicated that even at these low levels, all three substances produced some larval mortality. This preliminary study suggests that oxidation by-products formed during chlorination or ozonization of power plant cooling waters may have adverse effects upon the growth of marine invertebrates, such as C. virginica, during their delicate larval stages.     

Evaluation of a Florida coastal golf complex as a local and watershed source of bioavailable contaminants

Contaminant fate in coastal areas impacted by golf course runoff is not well understood. This report summarizes trace metal, pesticide and PCB residues for colonized periphyton, Ruppia maritima (widgeon grass), Callinectes sapidus Rathbun (blue crabs) and Crassostrea virginica Gemlin (Eastern oyster) collected from areas adjacent to a Florida golf course complex which receive runoff containing reclaimed municipal wastewater. Concentrations of 19 chlorinated pesticides and 18 PCB congeners were usually below detection in the biota. In contrast, 8 trace metals were commonly detected although concentrations were not usually significantly different for biota collected from reference and non-reference coastal areas. Residue concentrations in decreasing order were typically: zinc, arsenic, copper, chromium, lead, nickel, cadmium and mercury. Mean BCF values for the eight trace metals ranged between 160-57000 (periphyton), 79-11033 (R. maritima), 87-162625 (C. virginica) and 12-9800 (C. sapidus). Most trace metal residues in periphyton colonized adjacent to the golf complex, were either similar to or significantly less than those reported for periphyton colonized in nearby coastal areas impacted by urban stormwater runoff and treated municipal and industrial wastewater discharges. Consequently, the recreational complex does not appear to be a major source of bioavailable contaminants locally nor in the immediate watershed based on results for the selected biota.     

Spatiotemporal distributions of earthquakes in the northeastern segment of the Amur plate in two phases of variations in the modulus of the Earth’s rotation rate

The modeling results are presented on the annual dynamics of seismicity in the northeastern segment of the Amur plate, which are obtained from statistical studies of the number of earthquakes with magnitudes 2 ≤ М ≤ 6 in different phases of variations in the Earth’s rotation rate. We have calculated a degree of relationship between the observed seismicity variations and phases of decrease and increase in the Earth’s rotation rate for the magnitude ranges between 2 ≤ М < 4 and 4 ≤ М < 5 using rank correlation methods. It has been established that epicenters of earthquakes with magnitudes 5 ≤ М ≤ 6 are spatially grouped into a sequence of homogeneous equally spaced, 3.5°–4°, on average, east-westerly oriented clusters.     

Origin and analysis of aliphatic and cyclic hydrocarbons in northeast United Kingdom coastal marine sediments

Sediment samples from multiple sites in the North Sea Coast of England were solvent extracted and analysed by a quadruple gas chromatograph equipped with a mass spectrometer detector in order to determine the concentration and distribution of aliphatic and alicyclic n-alkanes. Results indicate that most of the organic species present in the sediment samples consisted of anthropogenically derived long chain aliphatic and alicyclic n-alkanes (_nC_{10-15, 17, 19-21, 24, 26, 27, 29, 30, 33, 35, 36, 43}), n-alkanols, n-alkanals, n-alkanones, esters as well as many volatile organic compounds (VOCs). Chemical composition of samples and relative concentration were found to vary both spatially and temporally on all scales. These variations are mainly attributable to spatial and temporal variations in source but also parameters such as rainfall, turbulence and micro-organism activity also account for the observed trends.     

Evidence for Increasing Indoor Sources of 1,2-Dichloroethane Since 2004 at Two Colorado Residential Vapor Intrusion Sites

Groundwater contamination associated with two former industrial facilities in Denver, Colorado, has led to concerns about vapor intrusion into residences adjacent to the facilities. 1,1,1-Trichloroethane (1,1,1-TCA), 1,1-dichloroethene (1,1-DCE), and trichloroethene (TCE) are the main contaminants of concern in groundwater, with trace levels of 1,2-dichloroethane (1,2-DCA) present at one of the sites. Indoor air monitoring programs have been ongoing at these two sites since 1998 and recent results have suggested that background, indoor source, 1,2-DCA has been increasing in the frequency of detection, and median and maximum concentration over the past several years. A lines of evidence evaluation was undertaken for both sites in order to document the predominance of indoor sources of 1,2-DCA. Evidence utilized included spatial evaluation of 1,2-DCA in indoor air; comparison of 1,2-DCA concentrations in mitigated and unmitigated homes; a phone survey to evaluate the potential for smoking to contribute to indoor air 1,2-DCA levels; evaluation of mitigation system effluent data; and an evaluation of volatile organic compound (VOC) ratios in groundwater and indoor air. The results of this evaluation indicated that smoking had no demonstrable influence on measured indoor air concentrations. In addition, it appears that consumer products have had a markedly increased influence on indoor air concentrations since 2005. Data from one of the industrial facilities at one of the sites also indicated that polyvinyl chloride (PVC) and vinyl composite floor adhesive used in a building remodel in 2005 apparently generated elevated levels of indoor 1,2-DCA and vinyl chloride, which have been sustained up to the present time.     

Spatial patterns of submerged macrophytes and heavy metals in the hypertrophic, contaminated, shallow reservoir Lake Qattieneh/Syria

Our investigation on macrophytes in Lake Qattieneh, a large, shallow reservoir in western Syria, is a first assessment of ecological status of this lake. We studied spatial distribution patterns of aquatic macrophyte vegetation and heavy metal concentrations to determine if they can be used as indicators of point sources of pollution. Industrial and municipal point sources at the lake shore increase nutrient load and contamination by heavy metals. Water analyses revealed high concentrations of some heavy metals at some littoral sites: Ni 88.7 μg L⁻¹, Cr 49.99 μg L⁻¹, Co 14.38 μg L⁻¹, and Cu 11.65 μg L⁻¹. Despite hypertrophic conditions and high heavy metal contamination, we recorded several submerged macrophyte species with heterogeneous spatial distribution patterns. Whereas Potamogeton pectinatus L. dominates in the eastern part of the lake, near industrial point sources, both Myriophyllum spicatum L. and Potamogeton lucens L. form extended patches in the western part of the lake. The shallow, littoral areas near villages are dominated by Ranunculus trichophyllus Chaix in Villars and Ceratophyllum demersum L. The west-east gradient in nutrient and heavy metal concentrations in waters and sediments are reflected by the spatial distribution of submersed species. While the heavy metal concentrations of the water body vary considerably in different seasons, the contents in submersed macrophytes integrate seasonal variations of longer time periods. Spatial distribution and tissue accumulation of littoral macrophyte species reflect the environmental conditions at respective sites such as heavy metal contents in water and sediment.     

Spatiotemporal variations of internal P-loading and the related mechanisms in the large shallow Lake Chaohu

Spatiotemporal variations of P species and adsorption behavior in water column, interstitial water, and sediments were investigated in the large shallow eutrophic Lake Chaohu. Orthophosphate (Ortho-P) and total phosphorus (TP) concentrations were significantly higher in the western part than in the eastern part of the lake, due to different nutrient inputs from the surrounding rivers. Moreover, particulate phosphorus (PP) concentration was in a similar spatial pattern to Ortho-P and TP concentrations, and also showed significantly positive correlation with the biomass of Microcystis, indicating more uptake and store of phosphorus by Microcystis than by other algae. Increase of pH and intensive utilization of P by phytoplankton were the main factors promoting P (especially Fe-P) release from the sediment to interstitial water during the cyanobacterial blooms in Lake Chaohu. Spatial dynamics in TP concentration, P species and adsorption behavior of the sediment, coupled with the statistical analyses, suggested that the spatial heterogeneity of P contents in the sediment was influenced by various factors, e.g. human activities, soil geochemistry and mineral composition. In spite of similar TP contents in the sediments, increase in proportion of Fe-P concentration in the sediment may result in a high risk of P release.     

Multivariate probabilistic estimates of heat stress for rice across China

Heat stress, a major threat to rice (Oryza sativa) production across China, would tend to increase in frequency and intensity under warming climate. Unlike probabilistic analysis via a univariate character, heat stress events, characterized by three variables (i.e., duration, peak and accumulated detrimental intensity), were identified in the past years. Nine distribution functions (i.e., Beta, Cauchy, Logistic, Normal, Exponential, Gamma, Lognormal, Weibull and Generalized Extreme Value) were firstly introduced and compared to select the best-fit marginal distribution of univariable by using Kolmogorov–Smirnov test, and seven copula functions (i.e., Normal and t, Gumbel–Hougaard, Clayton, Frank, Joe, Ali-Mikhail-Haq) were applied in the distributions of multivariables by Akaike Information Criterion statistics. It was obvious that higher magnitude was in the eastern parts in the context of heat stress frequency and characteristic variables. Critical values of heat stress variables corresponding to the certain return periods (i.e. 5, 10, 20 and 50 years) successively expanded in intensity and spatial scope. Inter-correlations of heat stress variables were significant, enlightening the importance of copula in connecting heat stress variables. The combined and co-occurrence bivariate and trivariate return period at certain univariate value corresponding to the given return periods, were consistent at the spatial scale. Accordingly, it was highlighted that eastern parts, especially Zhejiang, central-northern Fujian and eastern Jiangxi, were prone to heat stress, as a consequence of not only univariate but also multivariate probabilistic analysis. These results can be helpful in quantitatively assessing the vulnerability of rice to heat stress and provide us desired information of prevention strategies for heat stress.     

Chemical and toxicological characteristics of sewage sludge ocean dumped in the New York Bight

This paper compares and contrasts data on the chemical characteristics and acute toxicities of the waste from nine applicants (representing 20 sewage treatment facilities) currently disposing of municipal sewage sludge at the 12-Mile dumpsite located in the New York Bight Apex. Each of the chemical analytes examined for the 20 facilities was highly variable, both within and among facilities. Toxicity tests conducted by the applicants revealed that, in the majority of tests, Mysidopsis bahia was the most sensitive of the three species tested. Five facilities that receive large volumes of industrial waste were found to contribute over 75% of the total toxic load to the dumpsite.     

Surface Water Contamination by Uranium Mining/Milling Activities in Northern Guangdong Province,China

The northern region of Guangdong Province, China, has suffered from the extensive mining/milling of uranium for several decades. In this study, surface waters in the region were analyzed by inductively coupled plasma optical emission spectrometry (ICP‐OES) for the concentrations of uranium (U), thorium (Th), and non‐radioactive metals (Fe, Mn, Mg, Li, Co, Cu, Ni, and Zn). Results showed highly elevated concentrations of the studied radionuclides and metals in the discharged effluents and the tailing seepage of the U mining/milling sites. Radionuclide and heavy metal concentrations were also observed to be overall enhanced in the recipient stream that collected the discharged effluents from the industrial site, compared to the control streams, and rivers with no impacts from the U mining/milling sites. They displayed significant spatial variations and a general decrease downstream away from upper point‐source discharges of the industrial site. In addition, obvious positive correlations were found between U and Th, Fe, Zn, Li, and Co (R² > 0.93, n = 28) in the studied water samples, which suggest for an identical source and transport pathway of these elements. In combination with present surface water chemistry and chemical compositions of uraniferous minerals, the elevation of the analyzed elements in the recipient stream most likely arose from the liquid effluents, processing water, and acid drainage from the U mining/milling facilities. The dispersion of radionuclides and hazardous metals is actually limited to a small area at present, but some potential risk should not be negligible for local ecosystem. The results indicate that environmental remediation work is required to implement and future cleaner production technology should be oriented to avoid wide dispersion of radioactivity and non‐radioactive hazards in U mining/milling sites.     

Modelling the influence of spatially varying hydrodynamics on the cross-sectional stability of double inlet systems

The cross-sectional stability of double inlet systems is investigated using an exploratory model that combines Escoffier’s stability concept for the evolution of the inlet’s cross-sectional area with a two-dimensional, depth-averaged (2DH) hydrodynamic model for tidal flow. The model geometry consists of four rectangular compartments, each with a uniform depth, associated with the ocean, tidal inlets and basin. The water motion, forced by an incoming Kelvin wave at the ocean’s open boundary and satisfying the linear shallow water equations on the f -plane with linearised bottom friction, is in each compartment written as a superposition of eigenmodes, i.e. Kelvin and Poincaré waves. A collocation method is employed to satisfy boundary and matching conditions. The analysis of resulting equilibrium configurations is done using flow diagrams. Model results show that internally generated spatial variations in the water motion are essential for the existence of stable equilibria with two inlets open. In the hydrodynamic model used in the paper, both radiation damping into the ocean and basin depth effects result in these necessary spatial variations. Coriolis effects trigger an asymmetry in the stable equilibrium cross-sectional areas of the inlets. Furthermore, square basin geometries generally correspond to significantly larger equilibrium values of the inlet cross-sections. These model outcomes result from a competition between a destabilising (caused by inlet bottom friction) and a stabilising mechanism (caused by spatially varying local pressure gradients over the inlets).