Mercury species of sediment and fish in freshwater fish ponds around the Pearl River Delta, PR China: human health risk assessment

This study investigated total mercury (THg) and methylmercury (MeHg) concentrations in five species of freshwater fish and their associated fish pond sediments collected from 18 freshwater fish ponds around the Pearl River Delta (PRD). The concentrations of THg and MeHg in fish pond surface sediments were 33.1-386 ng g(-1) dry wt and 0.18-1.25 ng g(-1) dry wt, respectively. The age of ponds affected the surface sediment MeHg concentration. The vertical distribution of MeHg in sediment cores showed that MeHg concentrations decreased with increasing depth in the top 10 cm. In addition, a significant correlation was observed between %MeHg and DNA from Desulfovibrionacaea or Desulfobulbus (p<0.05) in sediment cores. Concentrations of THg and MeHg in fish muscles ranged from 7.43-76.7 to 5.93-76.1 ng g(-1) wet wt, respectively, with significant linear relationships (r=0.97, p<0.01, n=122) observed between THg and MeHg levels in fish. A significant correlation between THg concentrations in fish (herbivorous: r=0.71, p<0.05, n=7; carnivorous: r=0.77, p<0.05, n=11) and corresponding sediments was also obtained. Risk assessment indicated that the consumption of largemouth bass and mandarin fish would result in higher estimated daily intakes (EDIs) of MeHg than reference dose (RfD) for both adults and children.     

Significance of metal exchange in EDDS-flushing column experiments

Chelating agents have been widely studied for extracting heavy metals from contaminated soils, and the effectiveness of EDDS ([S,S]-ethylene-diamine-disuccinic acid) has aroused extensive attention because of its biodegradability in the natural environment. However, in the course of EDDS-flushing, metal exchange of newly extracted metal-EDDS complexes with other sorbed metals and mineral cations may result in metal re-adsorption on the soil surfaces. Therefore, this study investigated the relative significance of metal exchange under different travel distances of chelant complexes, characteristics of soil contamination, and solution pH in the column experiments. As a result of metal exchange, the elution of Zn and Pb was retarded and the cumulative extraction was lower than those of Ni and Cu, especially over a longer travel distance. Compared with the field-contaminated soils, the effects of metal exchange were even more substantial in the artificially contaminated soil because of a greater amount of extractable metals and a larger proportion of weakly bound fractions. By contrast, metal exchange was insignificant at pH 8, probably due to less adsorption of metal-EDDS complexes. These findings highlight the conditions under which metal exchange of metal-EDDS complexes and the resulting impacts are more significant during EDDS-flushing.     

Influences of redox transformation, metal complexation and aggregation of fulvic acid and humic acid on Cr(VI) and As(V) removal by zero-valent iron

This study investigated the removal kinetics and mechanisms of Cr(VI) and As(V) by Fe(0) in the presence of fulvic acid (FA) and humic acid (HA) by means of batch experiments. The focus was on the involvements of FA and HA in redox reactions, metal complexation, and iron corrosion product aggregation in the removal of Cr(VI) and As(V) removal by Fe(0). Synthetic groundwater was used as the background electrolyte to simulate typical groundwater. The results showed faster Cr(VI) removal in the presence of HA compared to FA. Fluorescence spectroscopy revealed that no redox reaction occurred in the FA and HA. The results of the speciation modeling indicate that the free Fe(II) concentration was higher in the presence of HA, resulting in a higher removal rate of Cr(VI). However, the removal of As(V) was inhibited in the HA solution. Speciation modeling showed that the concentration of dissolved metal-natural organic matter (metal-NOM) complexes significantly affected the aggregation of the iron corrosion products which in turn affected the removal of As(V). The aggregation was found to be induced by gel-bridging of metal-NOM with the iron corrosion products. The effects of metal-NOM on the aggregation of the iron corrosion products were further confirmed by TEM studies. Larger sizes of iron corrosion products were formed in the FA solution compared to HA solution. This study can shed light on understanding the relationships between the properties of NOM (especially the content of metal-binding sites) and the removal of Cr(VI) and As(V) by Fe(0).     

Simultaneous chemical and sensory characterization of volatile organic compounds and semi-volatile organic compounds emitted from swine manure using solid phase microextraction and multidimensional gas chromatography-mass spectrometry-olfactometry

Swine manure is associated with emissions of odor, volatile organic compounds (VOCs) and other gases that can affect air quality on local and regional scales. In this research, a solid phase microextraction (SPME) and novel multidimensional gas chromatography-mass spectrometry-olfactometry (MDGC-MS-O) system were used to simultaneously identify VOCs and related odors emitted from swine manure. Gas samples were extracted from manure headspace using Carboxen/polydimethylsiloxane (PDMS) 85-microm SPME fibers. The MDGC-MS-O system was equipped with two columns in series with a system of valves allowing transfer of samples between columns (heartcutting). The heartcuts were used to maximize the isolation, separation, and identification of compounds. The odor impact of separated compounds was evaluated by a trained panelist for character and intensity. A total of 295 compounds with molecular weights ranging from 34 to 260 were identified. Seventy one compounds had a distinct odor. Nearly 68% of the compounds for which reaction rates with OH* radicals are known had an estimated atmospheric lifetime <24 h.     

Microwave treatment and struvite recovery potential of dairy manure

Microwave digestion of liquid dairy manure was tested for the release of nutrients, such as orthophosphates, ammonia-nitrogen, magnesium, calcium and potassium, both with and without the aid of an oxidizing agent (hydrogen peroxide). The orthophosphate to total phosphorus ratio of the manure increased from 21% to greater than 80% with 5 minutes of microwave treatment. More than 36% of total chemical oxygen demand (t-COD) of the manure was reduced when microwave digestion was assisted with peroxide addition. In addition, the volatile fatty acids (VFAs) distribution shifted to simpler chain acids (acetic acid in particular) with an increase in operating temperature. In the second part of the study, digested manure with increased soluble phosphate was tested for the recovery of struvite (magnesium ammonium phosphate) at different pH. It was found that up to 90% of orthophosphate can be removed from the solution. Overall, it was concluded that the oxidizing agent-assisted microwave digestion process can be used upstream of anaerobic digestion, following which the anaerobically digested manure can be used for struvite recovery. Thus, this microwave digestion process presents the potential for enhanced efficiencies in both manure digestion and struvite recovery.     

A GIS-based system for allocating municipal solid waste incinerator compensatory fund

To ease the NIMBY (not in my back yard) syndrome of constructing municipal solid waste (MSW) incinerators in Taiwan, compensatory funding is widely allocated to the impacted communities to gain the acceptance and support of residents living the impacted areas. This paper presents a spatial methodology for distributing a compensatory fund more logically based on the environmental impact on each neighborhood in Taipei City. This method integrates ten impact factors, which have been proposed by a local committee, to evaluate all neighborhoods using mathematical models combined with spatial analyses in an analytic hierarchy process. The compensatory fund is distributed according to the resulting final scores. A GIS (geographic information systems)-based system has been developed to assist in assigning the final scores to the neighborhoods impacted. Results on impact factors and fund distributions are combined; they are included in an information system and displayed in spatial scales. For Taipei City, the impact of air quality during the incinerator operating period is the item of greatest concern to the surrounding residents and thus, it receives a relatively higher weight of 0.2894. As a result, high impact scores were assigned to not only those neighborhoods hosting the incinerators, but also the neighborhoods where the maximum particulate air pollutants occurred. This approach could be applicable to other MSW incinerators with similar environmental impact problems and interest in compensation schemes.     

Copper extraction effectiveness and soil dissolution issues of EDTA-flushing of artificially contaminated soils

Ethylenediaminetetraacetic acid (EDTA) was used as a reference chelating agent in column experiments to investigate the effectiveness of chelant-enhanced flushing of soils artificially contaminated under various conditions (low/high Cu loading, and aging). The associated soil dissolution issues were of particular concern. Dissolution of indigenous Fe/Al oxides, Ca carbonates and organic matter was monitored over the course of flushing. Regardless of contamination condition, above 85% extraction efficiency could be accomplished by 10(-2) and 10(-3)M EDTA-flushing, but not 10(-4)M. The Cu extraction kinetics positively correlated to EDTA concentration but inversely to Cu loading in soils. In addition to extraction from weakly sorbed fractions, a large portion of Cu was extracted from oxide, organic matter and residual fractions, which appears to derive from soil dissolution. Cumulative dissolved amounts of Fe, Al, and Ca were found to reach as high as hundreds of mgkg(-1), which were comparable to Cu contamination. Soil organic matter, which is known to strongly interact with Fe and Al oxides, was also mobilized. The rate and extent of these soil dissolutions were also positively correlated to EDTA concentration. Therefore, the co-extraction of soil minerals and organic matter during chelant-enhanced flushing, which would alter both physical structure and chemical properties of the soils, is detrimental to future land use and deserves greater attention. The concentration of chelating agent is the most crucial factor for an effective soil flushing with minimal damage.     

The nonlinearity and related band strength of carbon monoxide when applied in ambient air measurement using open long-path Fourier transform infrared spectrometry

The accuracy of CO concentration determination by open-path Fourier transform infrared (FTIR) spectrometry has been re-evaluated in detail. The evaluation focuses on the correction of the calibration curve--the integrated intensity of a standard spectrum--that is used as a comparison spectrum when doing quantitative analysis of CO. Results show that the calibration curve (with 0.5 cm(-1) or 1 cm(-1) resolution) is apparently inclined to be nonlinear under standard conditions, and that the threshold point of nonlinearity is approximately 0.1 atm-cm. Two commercial FTIR field monitoring systems have been used to investigate the nonlinearity trend. The experimental method consists of using open-path FTIR systems in combination with nondispersive infrared (NDIR) monitors to establish the calibration curve in a semi-closed corridor The results have been double-checked using closed-cell dynamic equilibrium systems. When the optical density is larger than a certain value, the curves begin to bend, and when the optical density approaches zero, the band strength is around 178 +/- 3 atm(-1) cm(-2) and 173 +/- 2 atm(-1) cm(-2), respectively, for 0.5 and 1 cm(-1) resolution at standard temperature and pressure (STP). These values are quite different from other published data that have been acquired by the pressurized method or by high-resolution (<0.006 cm(-1)) spectrometers. It is thought that a higher accuracy is achieved when these new calibration results are used to quantify the CO concentration. The error in concentration determination within 0.1 optical density is less than 2%, and that in the higher optical density region is less than 5%.     

Towards a framework for assessment and management of cumulative human impacts on marine food webs

Effective ecosystem‐based management requires understanding ecosystem responses to multiple human threats, rather than focusing on single threats. To understand ecosystem responses to anthropogenic threats holistically, it is necessary to know how threats affect different components within ecosystems and ultimately alter ecosystem functioning. We used a case study of a Mediterranean seagrass (Posidonia oceanica) food web and expert knowledge elicitation in an application of the initial steps of a framework for assessment of cumulative human impacts on food webs. We produced a conceptual seagrass food web model, determined the main trophic relationships, identified the main threats to the food web components, and assessed the components’ vulnerability to those threats. Some threats had high (e.g., coastal infrastructure) or low impacts (e.g., agricultural runoff) on all food web components, whereas others (e.g., introduced carnivores) had very different impacts on each component. Partitioning the ecosystem into its components enabled us to identify threats previously overlooked and to reevaluate the importance of threats commonly perceived as major. By incorporating this understanding of system vulnerability with data on changes in the state of each threat (e.g., decreasing domestic pollution and increasing fishing) into a food web model, managers may be better able to estimate and predict cumulative human impacts on ecosystems and to prioritize conservation actions.     

The clinical impact of the first-trimester nuchal translucency between the 95th–99th percentiles

Objectives

To evaluate the clinical significance of nuchal translucency (NT) between the 95th–99th percentile in terms of typical and atypical chromosomal abnormalities (ACAs), associated fetal congenital defects and postnatal outcome.

Methods

A retrospective cohort study of fetuses with NT between the 95th–99th percentile. Data regarding the rate of associated fetal defects, genetic abnormalities and postnatal outcome were collected.

Results

A total of 306 cases of fetuses with an NT between the 95th–99th percentiles were included. The overall rate of genetic abnormalities was 12.1% (37/306). Chromosomal abnormalities were found in 10.1% (31/306) of cases and 2% were ACA (6/306). Within this group, two were pathogenic Copy Number Variants (CNVs) and four were single gene disorders. The overall rate of fetal congenital defects was 13.7% (42/306). All ACAs were found in fetuses with congenital defects. Postnatally, a new diagnosis of a single gene disorder was made in 0.85% of cases (2/236).

Conclusions

The presence of an NT between the 95th–99th percentiles carries a 10-fold increased risk of fetal defects, representing an indication for referral for a detailed fetal anatomy evaluation. The risk of ACA is mainly related to the presence of fetal defects, irrespective of the combined test risk.