Geochemical stability of chromium in sediments from the lower Hackensack River, New Jersey

Elevated levels of chromium, partly attributable to historical disposal of chromite ore processing residue, are present in sediment along the eastern shore of the lower Hackensack River near the confluence with Newark Bay. Due to anaerobic conditions in the sediment, the chromium is in the form of Cr(III), which poses no unacceptable risks to human health or to the river ecology. However, as water quality conditions have improved since the 1970s, aerobic conditions have become increasingly prevalent in the overlying water column. If these conditions result in oxidation of Cr(III) to Cr(VI), either under quiescent conditions or during severe weather or anthropogenic scouring events, the potential for adverse ecological effects due to biological exposures to Cr(VI) is possible, though the reaction kinetics associated with oxidation of Cr(III) to Cr(VI) are unfavorable. To investigate the stability of Cr(III) in Hackensack River sediments exposed to oxic conditions, sediment suspension and oxidation experiments and intertidal sediment exposure experiments that exposed the sediments to oxic conditions were conducted. Results revealed no detectable concentrations of Cr(VI), and thus no measurable potential for total chromium oxidation to Cr(VI). Furthermore, total chromium released from sediment to elutriate water in the oxidation and suspension experiments ranged from below detection (<0.01 mg/L) to 0.18 mg/L, below the freshwater National Recommended Water Quality Criteria (NRWQC) of 0.57 mg/L for Cr(III). These results support conclusions of a stable, in situ geochemical environment in sediments in the lower Hackensack River with respect to chromium. Results showed that chemicals other than Cr(VI), including copper, lead, mercury, zinc, and PCBs, were released at levels that may pose a potential for adverse ecological effects.     

Assessing chemical behavior and developing remedial actions using a mass balance model of chemical fate in the Bay of Quinte

A multi-segment model of chemical fate and transport in the Bay of Quinte and a food chain model that simulate average annual conditions, are used to examine the behavior of arsenic (As), pentachlorophenol (PCP) and polychlorinated biphenyls (PCBs) in the Bay, an “Area of Concern” in the Great Lakes. The Bay model was used to predict the status of As and PCP from known loading data, but for PCBs with unknown loadings, the Bay and food chain models were used to “back-calculate” total loadings to the Bay. Chemical behavior depends on the characteristics of the Bay and physical-chemical properties of chemicals. Short water residence times of less than a week to several months result in chemicals being advected, unless subject to other, more rapid processes. In Upper Bay, rapid rates of sediment deposition and resuspension retard losses by advection of persistent chemicals such as PCBs and As, despite As being largely dissolved in the water column. Overall, behavior in Upper Bay is dominated by sediment-water exchange, and in Lower Bay by water exchange with Lake Ontario. Because of PCP's rapid transformation rate in the water column, most chemical is transformed before it reaches the sediments or downstream segments. It is recommended that elevated As inputs from the Moira River must be controlled to reduce in-Bay water and sediment concentrations, and for PCP, industrial discharges must be reduced. If reduced, concentrations in the Bay would respond within 3 months, 1 month and 3 years in the water, and about 6, 3 and 10 years in sediments for As, PCP and PCBs, respectively.     

Selenium contamination of the grasslands,a major California waterfowl area

In a recent study at Kesterson Reservoir in California, selenium was shown to cause mortality and deformities in embryos of aquatic birds. The present study was conducted to determine if selenium or other contaminants in agricultural drainwater used for marsh management were likely to cause similar adverse effects in the nearby Grasslands area. Selenium concentrations were elevated ( < 15 ppm, dry-weight) in livers of some birds of all species collected from the Grasslands. Mean selenium concentrations in all species sampled in the South Grasslands were significantly higher (P < 0.05) than those from the “control site”, the Volta Wildlife Area. Mean selenium levels in black-necked stilts (Himantopus mexicanus) from the South Grasslands (35.6 ppm) were similar (P > 0.05) to levels in stilts from Kesterson (46.4 ppm), but means for American avocets (Recurvirostra americana) from the South Grasslands (67.3 ppm) were higher (P < 0.05) than those from Kesterson (28.4 ppm). Bird eggs and fish from the Grasslands also contained elevated levels of selenium. Concentrations of eight heavy metals in fish generally reflected those patterns previously found in water entering the study areas. Of the organochlorines detected in fish, only DDE occurred at concentrations potentially harmful to birds (6.1 and 3.0 ppm, wet weight, at two South Grassland sites). The effect on avian health or reproduction of the other contaminants, singly or in combination, could not be determined. However, selenium levels were apparently sufficiently elevated in 1984 to have caused adverse effects on avian reproduction in the South Grasslands.     

基于Maxent模型的深圳湾鸟类热点生境 判别及修复研究

鸟类热点生境判别对于掌握鸟类空间分布格局、 识别保护空缺及指引生境修复策略具有科学价值。采用最大 熵模型确定深圳湾2000与2020年的鸟类热点生境,分析鸟 类生境的变化及其与景观格局演变的关系。结果表明：1)各 环境因子对不同生态类群的鸟类影响程度各不相同,除鸣禽 以外水源距离对其他类群鸟类的影响较大,其次为高程和 年降水量;2)2020年深圳湾的鸟类热点生境占总研究区的 3%(22km2),呈现从自然保护区向城市内陆逐渐减少的趋 势,存在2km2的保护空缺;3)20年间深圳湾鸟类的热点生 境减少了7%,热点生境下降的地区主要集中在深圳湾沿海滩 涂、香港山贝河与屯门河流域中,且猛禽与游禽的生境退化最 为严重;4)鸟类热点生境面积随斑块的数量、密度、形状与用 地类型等景观指数的增加而降低,景观破碎化和景观连通性降 低是导致鸟类生境退化的主要原因。研究为深圳湾鸟类多样性 保护及生境修复提供了参考,对粤港澳大湾区协同生态保护与 城市建设的关系具有重要意义。     

Efficacy and environmental acceptability of two ballast water treatment chemicals and an alkylamine based-biocide

Ship's ballast waters transport large numbers of organisms which may become invasive in coastal regions. One option to address this problem is the use of biocides as ballast water treatment (BWT). Efficacy and environmental acceptability of three commercial active substances (the BWT biocides Peraclean^® Ocean and Seakleen^®, and alkylamine-based biocide Mexel^® 432/336) were tested against three bacteria species, two vegetative microalgae and one zooplanktonic larva, in 10 and 30 Practical Salinity Unit (PSU) waters. In both salinities, PeraClean^® Ocean was the most effective biocide against bacteria causing > 90% mortality at 20 mg/l, compared with 50 mg/l for Mexel^® 432/336 and > 500 mg/l for Seakleen^®. Regarding zooplankton, Seakleen^® was the most effective chemical causing 90% mortality in 24 h at concentrations < 6 mg/l (LC90_24 h) in both salinities, compared with 23 and 26 mg/l for Mexel^® 432/336 and 370 and 480 mg/l for PeraClean^® Ocean in 10 and 30 PSU, respectively. Similar pattern of efficacy was obtained for microalgae in 30 PSU: effective concentrations inducing 50% growth inhibition in 4 days were ≤ 1.6 mg/l for Seakleen^®, ≤ 10.1 mg/l for Mexel^® 432/336 and ≤ 30.9 mg/l for PeraClean^® Ocean. Our work highlighted that treated waters displayed residual toxicity after 24 h still inducing mortality depending on the organism and biocide. However Mexel^® 432/336 is the only biocide which had no impact on oyster larvae development at effective concentration. Altogether our data showed that Mexel^® 432/336 was the only biocide displaying a broad spectrum efficacy in concentrations < 50 mg/l and not toxic for oyster larvae development at this concentration. However residual toxicity of treated waters for any organism should be taken into account in BWT systems utilising biocides.     

Controlling toxic cyanobacteria: effects of dredging and phosphorus-binding clay on cyanobacteria and microcystins

Sediment dredging and Phoslock^® addition were applied individually and in combination in an enclosure experiment in a Dutch hypertrophic urban pond. These measures were applied to control eutrophication and reduce the risk of exposure to cyanobacterial toxins. Over the 58 days course of the experiment, cyanobacteria (predominantly Microcystis aeruginosa) gradually decreased until they dropped below the level of detection in the combined treated enclosures, they were reduced in dredged enclosures, but remained flourishing in controls and Phoslock^® treated enclosures. Cyanobacteria were, however, less abundant in the enclosures (medians chlorophyll-a 30-87 μg l⁻¹) than in the pond (median chlorophyll-a 162 μg l⁻¹), where also a thick surface scum covered one-third of the pond for many weeks.Soluble reactive phosphorus (SRP), total phosphorus and total nitrogen concentrations were significantly lower in the combined dredged and Phoslock^® treated enclosures than in controls. Median SRP concentrations were 24 μg P l⁻¹ in the combined treatment, 58 μg P l⁻¹ in dredged enclosures, and 90 μg P l⁻¹ in controls and 95 μg P l⁻¹ in Phoslock^® treated enclosures. Hence, the combined treatment was most effective in decreasing SRP and TP, and in lowering cyanobacterial biomass.Microcystin (MC) concentrations were analyzed by LC-MS/MS. MC concentrations and cyanobacterial biomass were positively correlated in all treatments. Mean MC concentrations in controls (71 μg l⁻¹), Phoslock^® treated enclosures (37 μg l⁻¹) and dredged enclosures (25 μg l⁻¹) exceeded the provisional guideline of 20 μg l⁻¹, whereas mean MC concentrations were 13 μg l⁻¹ in the combined treated enclosures. All samples contained the MC variants dmMC-RR, MC-RR, MC-YR, dmMC-LR and MC-LR; traces of MC-LY and nodularin were detected in few samples. The different treatments did not change the relative contribution of the variants to the MC pool; MC profiles in all treatments and the pond showed dominance of MC-RR followed by MC-LR. In the surface scum of the pond, total MC concentration was extremely high (64000 μg l⁻¹ or 1300 μg g⁻¹ DW), which poses a serious health hazard to children playing on the banks of the pond. Based on our results and pond characteristics, we propose combined sediment dredging and Phoslock^® addition, fish removal and strong reduction of duck feeding by the neighborhood as most promising measures controlling cyanobacterial hazards in this pond.     

Ecological food web analysis for chemical risk assessment

Food web analysis can be a critical component of ecological risk assessment, yet it has received relatively little attention among risk assessors. Food web data are currently used in modeling bioaccumulation of toxic chemicals and, to a limited extent, in the determination of the ecological significance of risks. Achieving more realism in ecological risk assessments requires new analysis tools and models that incorporate accurate information on key receptors in a food web paradigm. Application of food web analysis in risk assessments demands consideration of: 1) different kinds of food webs; 2) definition of trophic guilds; 3) variation in food webs with habitat, space, and time; and 4) issues for basic sampling design and collection of dietary data. The different kinds of food webs include connectance webs, materials flow webs, and functional (or interaction) webs. These three kinds of webs play different roles throughout various phases of an ecological risk assessment, but risk assessors have failed to distinguish among web types. When modeling food webs, choices must be made regarding the level of complexity for the web, assignment of species to trophic guilds, selection of representative species for guilds, use of average diets, the characterization of variation among individuals or guild members within a web, and the spatial and temporal scales/dynamics of webs. Integrating exposure and effects data in ecological models for risk assessment of toxic chemicals relies on coupling food web analysis with bioaccumulation models (e.g., Gobas-type models for fish and their food webs), wildlife exposure models, dose-response models, and population dynamics models.     

Ecological risk assessment of multimedia hazardous air pollutants: estimating exposure and effects.

Hazardous air pollutants, some of which have the potential for multimedia distribution, raise several hurdles for ecological risk assessment including: (1) the development of an adequate transport, fate and exposure model; and (2) the selection of exposure-response models that can accommodate multiple exposure routes for ecological receptors. To address the first issue, the EPA Office of Air Quality Planning and Standards has developed TRIM.FaTE, a mass-balance, fate, transport, and ecological exposure model that is a component of the Total Risk Integrated Methodology (TRIM) for air pollutants. In addition to abiotic transfers and transformations, TRIM.FaTE estimates the uptake of a chemical by terrestrial and aquatic organisms with time. Measures of exposure that TRIM.FaTE can provide include: (1) body burdens or tissue concentrations; (2) doses averaged over any time period; or (3) concentrations of chemicals in abiotic media. The model provides the user with the flexibility to choose the exposure-response thresholds or dose-response relationships that are best suited to data availability, routes of exposure, and the mechanism of toxicity of the chemical to an ecological receptor. One of the challenges of incorporating TRIM.FaTE into a risk assessment methodology lies in defining a streamlined model simulation scenario for initial screening-level risk assessments. These assessments may encompass multiple facilities that emit a variety of pollutants near diverse ecosystems. The information on ecological risk assessment methodology that is described is applicable to the EPA Residual Risk Program with emphasis on multimedia pollutants and the role of TRIM.FaTE.     

Sediment mercury dynamics and historical trends of mercury deposition in the St. Lawrence River area of concern near Cornwall, Ontario, Canada

The St. Lawrence River near Cornwall, Ontario was designated an Area of Concern by the International Joint Commission in 1985. Sediments from this area have historically been contaminated with mercury (Hg), and although concentrations have decreased since the 1970s, they still remain high. Nine sediment cores were collected from three sites within the Area of Concern in 2004/05 to determine the variability in historical profiles of Hg deposition to the river. Sediment and pore water phases were analyzed for total mercury (THg) and methyl mercury (MeHg) and cores were analyzed for ²¹⁰Pb to determine chronologies of sedimentation at these sites. Mercury diffusion rates in pore waters within the sediment column were determined to be very low (between 0 and 2.15 ng cm^− 2 year^− 1, n = 3) compared to the recent Hg sedimentation rates at these sites (183 ± 30 ng cm^− 2 year^− 1 SE, n = 9) determined by multiplying surface Hg concentrations with ²¹⁰Pb-derived sedimentation rates. These results indicate that Hg profiles in these cores accurately depict historical releases of Hg to the river bed. The influence of federal regulations in the early 1970s to restrict Hg emissions to the river was apparent in these dated sediment cores, as were the closures of several local industries in the mid 1990s. Mercury accumulation rates prior to 1970 were 60 times higher than those occurring after 1995. Methyl mercury showed surface enrichment in most of these sediment cores providing evidence that mercury methylation occurred most rapidly near the sediment surface.     

Butyltins in sediments and deposit-feeding bivalves Scrobicularia plana from Arcachon Bay,France

A survey was conducted in Arcachon Bay during the summer of 1993 to determine the concentrations of tributyltin (TBT) and two degradation products in sediments and deposit-feeding bivalves Scrobicularia plana; the recruitment of juvenile clams to one site was also investigated. The three butyltins were detected in all sediment samples; however, the concentrations of TBT (from 7 to 30 ng Sn g⁻¹) were far lower than the literature values shown to have adverse effects on populations of sediment-dwelling bivalves. TBT levels in adult S. plana were similarly reduced (from 28 to 165 ng Sn g⁻¹), and they were consistently lower than the values predicted by the modelled bioavailability of TBT in sediments. On the other hand, recruitment to that particular site was negligible when compared to that recorded in the 1970s; the same applies to the adult density in this and other sites. This decline of the local S. plana populations is discussed in relation to present and past TBT pollution.     

Controlling eutrophication by combined bloom precipitation and sediment phosphorus inactivation

The hypothesis that the combination of the flocculent polyaluminium chloride (PAC) with the lanthanum-modified bentonite Phoslock^® (Flock & Lock) could sink effectively a water bloom of cyanobacteria and could shift a turbid, cyanobacteria infested lake to a clear water lake was tested in a controlled laboratory experiment and a whole lake experiment. In the laboratory, a relatively low dose of the flocculent PAC (2.2 and 4.4 mg Al l⁻¹) was insufficient to sediment positively buoyant cyanobacteria (Microcystis aeruginosa). Similarly, the lanthanum modified clay (dosed at 390 mg l⁻¹) was insufficient to sediment the positively buoyant cyanobacteria. However, the combination of PAC and Phoslock^® effectively sedimented cyanobacteria flocks. Likewise, a combined treatment of 2 tons PAC and 18 tons Phoslock^® in Lake Rauwbraken in April 2008 effectively sedimented a developing cyanobacteria bloom of Aphanizomenon flos-aquae. The average chlorophyll-a concentration in the two years prior to this Flock & Lock treatment was 19.5 (±36.5) μg l⁻¹, while it was as low as 3.7 (±4.5) μg l⁻¹ in the years following the treatment. The combined treatment effectively reduced the amount of total phosphorus (TP) in the water column from on average 169 (±126) μg P l⁻¹ before the application to 14 (±15) μg P l⁻¹ after the treatment. Based on mean summer chlorophyll-a and TP concentrations, the lake was shifted from a eutrophic/hypertrophic state to an oligo/mesotrophic state. From directly after treatment in April 2008 until and including 2013, Lake Rauwbraken remained in an oligo-mesotrophic clear water state with TP reduced to less than 10% of the pre-treatment. This result shows that eutrophication in relatively small, isolated, stratifying lakes can be restored by targeting both water column and sediment P using a combination of flocculent and solid phase P-sorbent.     

Mercury accumulation and attenuation at a rapidly forming delta with a point source of mining waste

The Walker Creek intertidal delta of Tomales Bay, California is impacted by a former mercury mine within the watershed. Eleven short sediment cores (10 cm length) collected from the delta found monomethylmercury (MMHg) concentrations ranging from 0.3 to 11.4 ng/g (dry wt.), with lower concentrations occurring at the vegetated marsh and upstream channel locations. Algal mats common to the delta's sediment surface had MMHg concentrations ranging from 7.5 to 31.5 ng/g, and the top 1 cm of sediment directly under the mats had two times greater MMHg concentrations compared to adjacent locations without algal covering. Spatial trends in resident biota reflect enhanced MMHg uptake at the delta compared to other bay locations. Eighteen sediment cores, 1 to 2 m deep, collected from the 1.2 km² delta provide an estimate of a total mercury (Hg) inventory of 2500 ± 500 kg. Sediment Hg concentrations ranged from pre-mining background conditions of approximately 0.1 μg/g to a post-mining maximum of 5 μg/g. Sediment accumulation rates were determined from three sediment cores using measured differences of ¹³⁷Cs activity. We estimate a pre-mining Hg accumulation of less than 20 kg/yr, and a period of maximum Hg accumulation in the 1970s and 1980s with loading rates greater than 50 kg/yr, corresponding to the failure of a tailings dam at the mine site. At the time of sampling (2003) over 40 kg/yr of Hg was still accumulating at the delta, indicating limited recovery. We attribute observed spatial evolution of elevated Hg levels to ongoing inputs and sediment re-working, and estimate the inventory of the anthropogenic fraction of total Hg to be at least 1500 ± 300 kg. We suggest ongoing sediment inputs and methylation at the deltaic surface support enhanced mercury levels for resident biota and transfer to higher trophic levels throughout the Bay.     

Urban anglers' perception of risk from contaminated fish.

The Newark Bay Complex includes the Newark Bay, tidal portions of the Hackensack River, Passaic River, Arthur Kill, and Kill van Kull. It is a highly industrialized urban area including five counties and more than 20 local governments with a large racially-mixed population of more than 3 million people. In 1982, research conducted by the New Jersey Department of Environmental Protection (NJDEP) showed elevated levels of chemical contaminants in five species of fish and one type of crab in the Newark Bay Complex. Subsequently, the State of New Jersey adopted advisories to guide citizens on safe consumption practices for fish and crabs. Since then, fish consumption advisories have been issued primarily through the Fish and Game Digest, a publication distributed by the state to licensed anglers. However, anglers in the Complex are not required to have a fishing license because the waters are marine. Therefore, most anglers in this area do not receive advisory information. To gain greater insight into the information sources and risk perceptions of urban anglers, a survey was conducted of 300 anglers at 26 fishing and crabbing locations in the Newark Bay Complex during the summer and early fall of 1995. The objectives of the study were to learn anglers': (1) knowledge of fish consumption advisories; (2) belief in the advisories; (3) perception of how safe fish are to eat; (4) sources for information about fish and fishing; and (5) sources for information on fish consumption advisories. The study concluded that while 60% had heard about advisories, they either did not believe or were unconcerned about health effects from eating contaminated species. In addition, the most used source for information about fish and fishing was other fishermen, while newspapers were selected as a source for information about community news, health, and food safety.     

Degradation models and ecotoxicity in marine waters of two antifouling compounds: Sodium hypochlorite and an alkylamine surfactant

Industrial wastes have a substantial impact on coastal environments. Therefore, to evaluate the impact of cooling water discharges from coastal power plants, we studied the kinetics of the degradative processes and the ecotoxicity of two antifouling products: (1) a classic antifouling product; sodium hypochlorite (NaClO) and (2) an alternative one; aliphatic amines (commercial under the registered trade mark Mexel^®432). To assess the persistence of both compounds the decay of sodium hypochlorite and the primary biodegradation rate of Mexel^®432 were determined in natural seawater at 20 °C. The results indicated a more rapid decay of NaClO than Mexel^®432. The degradation behavior of both chemicals was described following a logistic model, which permitted calculating kinetic parameters such as t₅₀ or t₉₀. The t₅₀ was 1 h and 2 d for NaClO and Mexel^®432, respectively. To evaluate the potential risks of the aforementioned treatments to marine organisms, the acute toxicity of both antifouling products was studied on the microalgae Isochrysis galbana and Dunaliella salina, and on the invertebrate Brachionus plicatilis, using growth inhibition and death tests as toxic response, respectively. For I. galbana, the 96-h EC₅₀ values were 2.91 ± 0.15 mg/L of NaClO and 4.55 ± 0.11 mg/L of Mexel^®432. D. salina showed values of 96-h EC₅₀ of 1.73 ± 0.16 mg/L of NaClO and 7.21 ± 0.1 mg/L of Mexel^®432. Brachionus plicatilis showed a 24-h LC₅₀ of 1.23 ± 0.1 mg/L of NaClO and 3.62 ± 0.37 mg/L of Mexel^®432. Acute toxicity was highly dependent on the chemical and species tested. NaClO presented more toxic effects than Mexel^®432, also B. plicatilis was the most sensitive species in both cases. The lowest NOECs obtained, 0.25 mg/L for NaClO and 2.12 mg/L for Mexel^®432, were similar to the theoretical residual concentrations of these biocides in cooling water discharges. Therefore, these discharges can cause undesirable negative effects upon the aquatic organisms present.     

Soil metal concentrations and toxicity: Associations with distances to industrial facilities and implications for human health

Urban and rural areas may have different levels of environmental contamination and different potential sources of exposure. Many metals, i.e., arsenic (As), lead (Pb), and mercury (Hg), have well-documented negative neurological effects, and the developing fetus and young children are particularly at risk. Using a database of mother and child pairs, three areas were identified: a rural area with no increased prevalence of mental retardation and developmental delay (MR/DD) (Area A), and a rural area (Area B) and an urban area (Area C) with significantly higher prevalence of MR/DD in children as compared to the state-wide average. Areas were mapped and surface soil samples were collected from nodes of a uniform grid. Samples were analyzed for As, barium (Ba), beryllium (Be), chromium (Cr), copper (Cu), Pb, manganese (Mn), nickel (Ni), and Hg concentrations and for soil toxicity, and correlated to identify potential common sources. ArcGIS^® was used to determine distances between sample locations and industrial facilities, which were correlated with both metal concentrations and soil toxicity. Results indicated that all metal concentrations (except Be and Hg) in Area C were significantly greater than those in Areas A and B (p ≤ 0.0001) and that Area C had fewer correlations between metals suggesting more varied sources of metals than in rural areas. Area C also had a large number of facilities whose distances were significantly correlated with metals, particularly Cr (maximum r = 0.33; p = 0.0002), and with soil toxicity (maximum r = 0.25; p = 0.007) over a large spatial scale. Arsenic was not associated with distance to any facility and may have a different anthropogenic, or natural source. In contrast to Area C, both rural areas had lower concentrations of metals, lower soil toxicity, and a small number of facilities with significant associations between distance and soil metals.     

粤港澳大湾区典型滨海河口景观植物选择 策略研究 ——以珠海西部河口湿地为例

粤港澳大湾区9+2城市群是中国开放程度最高、经 济活力最强的区域之一,是以生态优先,绿色发展理念,建设 美丽湾区为引领,着力提升生态环境质量为目标的生态文明建 设区域。珠海处于粤港澳大湾区中最典型的珠江口地区,以该 区域城镇发展最快、规模最大的珠海西部河口湿地为研究对 象,对其植物景观群落的观赏性、耐盐性、抗风性、耐涝性、 耐旱性和耐污性等特质进行综合分析,结合对典型河口湿地景 观植物种类及立地条件开展调查,对河口湿地植物立地影响因 子进行了定量分析与评价。通过主成分分析法(PCA),综合 评估现阶段该区域湿地景观植物的适宜性、观赏性,并提出今 后适宜河口环境的景观植物种类,为河口湿地景观植物选择提 供技术支撑。     

Lake responses following lanthanum-modified bentonite clay (Phoslock) application: An analysis of water column lanthanum data from 16 case study lakes

Phoslock^® is a lanthanum (La) modified bentonite clay that is being increasingly used as a geo-engineering tool for the control of legacy phosphorus (P) release from lake bed sediments to overlying waters. This study investigates the potential for negative ecological impacts from elevated La concentrations associated with the use of Phoslock^® across 16 case study lakes. Impact-recovery trajectories associated with total lanthanum (TLa) and filterable La (FLa) concentrations in surface and bottom waters were quantified over a period of up to 60 months following Phoslock^® application. Both surface and bottom water TLa and FLa concentrations were <0.001 mg L⁻¹ in all lakes prior to the application of Phoslock^®. The effects of Phoslock^® application were evident in the post-application maximum TLa and FLa concentrations reported for surface waters between 0.026 mg L⁻¹–2.30 mg L⁻¹ and 0.002 mg L⁻¹ to 0.14 mg L⁻¹, respectively. Results of generalised additive modelling indicated that recovery trajectories for TLa and FLa in surface and bottom waters in lakes were represented by 2nd order decay relationships, with time, and that recovery reached an end-point between 3 and 12 months post-application. Recovery in bottom water was slower (11–12 months) than surface waters (3–8 months), most probably as a result of variation in physicochemical conditions of the receiving waters and associated effects on product settling rates and processes relating to the disturbance of bed sediments. CHEAQS PRO modelling was also undertaken on 11 of the treated lakes in order to predict concentrations of La³⁺ ions and the potential for negative ecological impacts. This modelling indicated that the concentrations of La³⁺ ions will be very low (<0.0004 mg L⁻¹) in lakes of moderately low to high alkalinity (>0.8 mEq L⁻¹), but higher (up to 0.12 mg L⁻¹) in lakes characterised by very low alkalinity. The effects of elevated La³⁺ concentrations following Phoslock^® applications in lakes of very low alkalinity requires further evaluation. The implications for the use of Phoslock^® in eutrophication management are discussed.     

Multi-laboratory evaluations of the performance of Catellicoccus marimammalium PCR assays developed to target gull fecal sources

Here we report results from a multi-laboratory (n = 11) evaluation of four different PCR methods targeting the 16S rRNA gene of Catellicoccus marimammalium originally developed to detect gull fecal contamination in coastal environments. The methods included a conventional end-point PCR method, a SYBR^® Green qPCR method, and two TaqMan^® qPCR methods. Different techniques for data normalization and analysis were tested. Data analysis methods had a pronounced impact on assay sensitivity and specificity calculations. Across-laboratory standardization of metrics including the lower limit of quantification (LLOQ), target detected but not quantifiable (DNQ), and target not detected (ND) significantly improved results compared to results submitted by individual laboratories prior to definition standardization. The unit of measure used for data normalization also had a pronounced effect on measured assay performance. Data normalization to DNA mass improved quantitative method performance as compared to enterococcus normalization. The MST methods tested here were originally designed for gulls but were found in this study to also detect feces from other birds, particularly feces composited from pigeons. Sequencing efforts showed that some pigeon feces from California contained sequences similar to C. marimammalium found in gull feces. These data suggest that the prevalence, geographic scope, and ecology of C. marimammalium in host birds other than gulls require further investigation. This study represents an important first step in the multi-laboratory assessment of these methods and highlights the need to broaden and standardize additional evaluations, including environmentally relevant target concentrations in ambient waters from diverse geographic regions.     

Temporal and spatial distributions of sediment mercury at salt pond wetland restoration sites, San Francisco Bay, CA, USA

Decommissioned agricultural salt ponds within south San Francisco Bay, California, are in the process of being converted to habitat for the benefit of wildlife as well as water management needs and recreation. Little is known of baseline levels of contaminants in these ponds, particularly mercury (Hg), which has a well established legacy in the Bay. In this study we described spatial and short-term temporal variations in sediment Hg species concentrations within and among the Alviso and Eden Landing salt ponds in the southern region of San Francisco Bay. We determined total Hg (Hg_t) and methylmercury (MeHg) in the top 5 cm of sediment of most ponds in order to establish baseline conditions prior to restoration, sediment Hg_t concentrations in a subset of these ponds after commencement of restoration, and variation in MeHg concentrations relative to sediment Hg_t, pH, and total Fe concentrations and water depth and salinity in the subset of Alviso ponds. Inter-pond differences were greatest within the Alviso pond complex, where sediment Hg_t concentrations averaged (arithmetic mean) 0.74 μg/g pre and 1.03 μg/g post-restoration activity compared to 0.11 μg/g pre and post at Eden Landing ponds. Sediment Hg_t levels at Alviso were fairly stable temporally and spatially, whereas MeHg levels were variable relative to restoration activities across time and space. Mean (arithmetic) sediment MeHg concentrations increased (2.58 to 3.03 ng/g) in Alviso and decreased (2.20 to 1.03 ng/g) in Eden Landing restoration ponds during the study. Differences in MeHg levels were related to water depth and pH, but these relationships were not consistent between years or among ponds and were viewed with caution. Factors affecting MeHg levels in these ponds (and in general) are highly complex and require in-depth study to understand.     

Cola soft drinks for evaluating the bioaccessibility of uranium in contaminated mine soils

There is a rising need for scientifically sound and quantitative as well as simple, rapid, cheap and readily available soil testing procedures. The purpose of this study was to explore selected soft drinks (Coca-Cola Classic®, Diet Coke®, Coke Zero®) as indicators of bioaccessible uranium and other trace elements (As, Ce, Cu, La, Mn, Ni, Pb, Th, Y, Zn) in contaminated soils of the Mary Kathleen uranium mine site, Australia. Data of single extraction tests using Coca-Cola Classic®, Diet Coke® and Coke Zero® demonstrate that extractable arsenic, copper, lanthanum, manganese, nickel, yttrium and zinc concentrations correlate significantly with DTPA- and CaCl₂-extractable metals. Moreover, the correlation between DTPA-extractable uranium and that extracted using Coca-Cola Classic® is close to unity (+ 0.98), with reduced correlations for Diet Coke® (+ 0.66) and Coke Zero® (+ 0.55). Also, Coca-Cola Classic® extracts uranium concentrations near identical to DTPA, whereas distinctly higher uranium fractions were extracted using Diet Coke® and Coke Zero®. Results of this study demonstrate that the use of Coca-Cola Classic® in single extraction tests provided an excellent indication of bioaccessible uranium in the analysed soils and of uranium uptake into leaves and stems of the Sodom apple (Calotropis procera). Moreover, the unconventional reagent is superior in terms of availability, costs, preparation and disposal compared to traditional chemicals. Contaminated site assessments and rehabilitation of uranium mine sites require a solid understanding of the chemical speciation of environmentally significant elements for estimating their translocation in soils and plant uptake. Therefore, Cola soft drinks have potential applications in single extraction tests of uranium contaminated soils and may be used for environmental impact assessments of uranium mine sites, nuclear fuel processing plants and waste storage and disposal facilities.