Strong Acid Digestion Research Articles

Metallomic mapping of gut and brain in heavy metal exposed earthworms: A novel paradigm in ecotoxicology

This study explored the uptake of lead in the epigeic earthworm Dendrobaena veneta exposed to 0, 1000, and 2500 μg Pb/g soil. The soil metal content was extracted using strong acid digestion and water leaching, and analysed by means of Inductively Coupled Plasma Mass Spectrometry (ICP-MS) to estimate absolute and bioavailable concentrations of metals in the soil. The guts and heads of lead-exposed earthworms were processed into formalin-fixed and paraffin embedded sections for high-resolution multi-element metallomic imaging via Laser Ablation ICP-MS (LA-ICP-MS). Metallomic maps of phosphorus, zinc, and lead were produced at 15-μm resolution in the head and gut of D. veneta. Additional 4-μm resolution metallomic maps of the earthworm brains were taken, revealing the detailed localisation of metals in the brain. The Pb bioaccumulated in the chloragogenous tissues of the earthworm in a dose-dependent manner, making it possible to track the extent of soil contamination. The bioaccumulation of P and Zn in earthworm tissues was independent of Pb exposure concentration. This approach demonstrates the utility of LA-ICP-MS as a powerful approach for ecotoxicology and environmental risk assessments.

Replacing manual operation with bio-automation: A high-throughput evolution strategy to construct an integrated whole-cell biosensor for the simultaneous detection of methylmercury and mercury ions without manual sample digestion

Methylmercury is primarily responsible for most food mercury pollution cases. However, most biosensors developed for mercury pollution analysis can only detect mercury ions. Although oxidative strong-acid digestion or microwave-assisted digestion can convert methylmercury into mercury ions, it is unsuitable for on-site detection. This study designed a bio-digestion gene circuit and integrated it into a mercury ion whole-cell biosensor，creating a novel on-site methylmercury detection method. Five alkyl mercury lyases from different bacterial genomes were screened via bioinformatics analysis, of which goMerB from Gordonia otitis showed the highest catalytic biological digestion efficiency. The goMerB site-specific saturation and random mutation libraries were constructed. After two rounds of high-throughput visualization screening, the catalytic activity of the mutant increased 2.5-fold. The distance between the three crucial amino acid sites and methylmercury changed in the mutant, which likely contributed to the enhanced catalytic efficiency. The optimized whole-cell biosensor showed a linear dynamic concentration range of 100 nM to 100 μM (R2 =0.991), satisfactory specificity, and interference resistance. The detection limit of the goMerBt6-MerR-RFP biosensor was 0.015 μM, while the limit of quantitation was 0.049 μM. This study demonstrated the application of synthetic biology for food safety detection and highlighted the future potential of “Lab in a Cell” for hazard analysis.

Conventional diatom testing using strong acid: Notable false-positive results caused by an underestimated contamination source (blind spot)

Low rates of diatom positivity in the closed organs of drowning victims present challenges for diatom testing. High positivity rates in closed organs of non-drowning victims also raise an important issue. These contradictory findings were common in diatom testing studies undertaken during the 1960–80 s, but the reasons remained unclear. In the present study, we identified one of the most important factors associated with false-positive results in diatom testing using strong acid. One to 290 false-positive diatoms were found in reused Kjeldahl flasks that were thoroughly washed after the first diatom testing and kept free of tissue before the second testing. False-positive results occurred in 11 of 20 cases when more than approximately 10,000 diatoms were present in digested tissue or water samples. Reused flasks were found to contain many common diatoms (<30 µm), including Cocconeis, Cymbella, Diatoma, Gomphonema, Navicula, and Nitzschia, in agreement with reports of diatoms identified in closed organs. Surprisingly, such false-positive results occurred even at the sixth diatom testing using the same flasks kept free of tissues in each analysis. In contrast, no diatoms were detected in any reagent or associated with other glassware. Thus, reuse of Kjeldahl flasks can readily cause false-positive results that cannot be completely prevented by cleaning the flasks using alkali detergents, as evidenced by detection of diatoms even after six tests. We assume that diatoms causing false-positive results are partially melted by heating and fixed onto the flask’s inner surface glass, as the diatom frustule consists primarily of SiO2, similar to glass. Adherent diatoms are then released from the glass by re-heating at the next diatom testing. These results also suggest that the number of diatoms remaining in a flask can increase steadily as a result of repeated reuse for analysis of lung or water samples. In contrast, in analyses using only new flasks, only one or two diatoms were found in 4 of 20 kidney, 2 of 12 liver, and 2 of 8 blood samples from 20 drowning victims. It is difficult to determine whether such diatoms are actually carried via the blood circulation, as contamination with a few diatoms can occur during autopsy procedures and diatom testing. In conclusion, only new (unused) Kjeldahl flasks should be used for diatom testing with strong acid digestion. Moreover, these data suggest that the number and frequency of diatoms present in closed organs of drowning victims may be much lower than previously thought.

Assessment of Risk Behaviors and Toxic Heavy Metals Exposure of Car Dye Workers in Repairing Services in Erbil City, Kurdistan Region, Iraq

The main objective of this study was to determine blood cadmium (BCd) and blood lead (BPb) contents for 16 car dye workers in repairing service and compared to those of 16 controls (non-occupational exposed subjects) in Erbil City, Kurdistan Region, Iraq. Strong wet acid digestion method was applied to digest whole blood samples using a mixture H2O2 (50% v/v) and HNO3 (65% v/v) with a volume ration (1:2). Inductively coupled plasma - optical emission spectrometer (ICP-OES) was used to determine these toxic metals in collected whole blood samples. The recorded mean of BCd and BPb contents in subjected painters were higher levels compared to the control group. The mean ± standard deviation (SD) contents of BCd and BPb of painters were 2.93±2.35 μg/L and 32.19±16.95 μg/L, respectively. The mean ± SD contents of BCd and BPb of controls were 0.870±0.34 μg/L and 22.46±12.55 μg/L, respectively. A set of formal investigation questionnaire was performed to know participants history profile, smoking status, clinical profile, the risk behaviors at the workplace, and occurrence symptoms. The results showed that the percentages of occurrence of most investigated symptoms (especially respiratory and musculoskeletal) system on the experimental painters were significantly (p-value = 0.016) higher than those symptoms of the control group. The collected data on risk behaviors confirmed that personal protection equipment (PPE) had not been concerned by most of the experimental painters. Duration of work (years), and the use of PPE (wearing a respirator) were noticeably associated with BCd and BPb levels of painters.

Historical deposition of trace metals in a marine sapropel from Mangrove Lake, Bermuda with emphasis on mercury, lead, and their isotopic composition

Sapropel is an organic-rich sediment formed under conditions that can result in sequestration of trace metals. Here, we determined the concentration of total mercury (Hg), lead (Pb), and 16 other metals (Al, Ba, Ca, Cd, Cr, Cs, Cu, Fe, Li, Mn, Ni, Sr, Tl, U, V, Zn) in a sapropel core from Mangrove Lake, Bermuda that dated back nearly two millennia. The purpose was to assess historical patterns of metal deposition on this geographically remote island in the North Atlantic Ocean. Two sediment cores were collected from Mangrove Lake using a modified piston corer. Cores were age-dated with a Bayesian statistical age-depth model using a multiproxy approach relying on 210Pb and radiocarbon dates. Total Hg was determined following US EPA Method 7473 using a direct mercury analyzer. Other metals were determined by sector field ICP-MS following a microwave-assisted strong-acid digestion. Stable isotope measurements of Hg and Pb were used to better track sources of these contaminants. Sapropel Hg concentrations were low (~ 50 ng g−1) from about 1000 AD to 1600 AD, followed by a slow rise in concentration until a high point of 209 ng g−1 in the early nineteenth century. Hg levels then returned to ~ 70 ng g−1, still elevated above baseline levels, before a final sharp rise in the mid-1900s to 430 ng g−1. Pb, Zn, Cu, Cr, and Ba had similar patterns, with Pb isotope ratios showing early natural fluctuations followed by the greater influence of pollution sources. Mercury stable isotope data also show the influence of anthropogenic sources during the 1800s and suggest a mix of atmospheric, terrestrial, and possibly marine-derived Hg inputs to the lake. The vertical distribution of elements and isotopes reveals changes in deposition through time associated with pollution from industrialization, and, possibly, volcanic activity, seawater intrusion, intense hurricane events, and local pollution from ship and fortress building. Overall, this study demonstrates that organic-rich sapropel provides a good historical record of metal contamination, and that Bermuda, despite its remote location, had metal deposition profiles much like the records of other sediment cores from around the world.

A new enzymatic method for extracting diatoms from organs of suspected drowning cases using papain: Optimal digestion and first practical application

Diatom analysis is very effective for positive diagnosis of water inhalation in drowning. However, conventional strong acid diatom testing is laborious and potentially dangerous. We propose a simple, fast, and safe protocol using inexpensive reagents such as papain, SDS, and 5 N HCl for extracting diatoms from lung, kidney, and liver tissues. First, we determined optimal conditions for papain digestion using porcine tissues. Papain digestion was clearly superior to Proteinase K digestion. Next, for assessing the assay effectiveness in practical cases, the papain digestion protocol was applied to 80 tissue samples from 20 suspected drowning victims. Left and right lung tissues (1 g each) were digested in 15-mL conical centrifuge tubes. Kidney and liver tissues (10 g each) were extracted in 175-mL conical centrifuge bottles. Papain dissolved all organs sufficiently and permitted clear visualization of diatoms, although papain’s solubilization activity was still inferior to strong acid digestion. The proposed enzymatic method requires only a low-speed centrifuge and water bath. Diatoms typically can be extracted from tissue samples within 3–5 h. The cost of protease is reduced some 6-fold by using papain in place of Proteinase K. Thus, the proposed method can be useful as a less-laborious, less-hazardous, and less-costly minimal test when the conventional strong acid digestion method is not performed due to personnel, equipment, budgetary limitation, or environmental and safety considerations.

Characterisation and partition of valuable metals from WEEE in weathered municipal solid waste incineration bottom ash, with a view to recovering

As the demand for critical and valuable metals increases due to industrial developments, especially in electronics and high-technology industries, the search for novel and sustainable sources grows in significance. Incinerated municipal solid waste (MSW) is a potential source of valuable metals, since a lot of waste from electrical and electronic equipment (WEEE) is not recycled properly and are is managed together with the refuse fraction of MSW, which is often landfilled or incinerated. Bottom Ash (BA) is the main by-product of incinerated MSW, which has been characterized to assess the potential recovery of valuable metals. The determination of the total amount of valuable metals (Ag, Al, Au, Be, Co, Cu, Ga, Ge, In, Ir, Li, Ni, Pd, Pt, Sb, Ta, and W) in seasonal samples of weather bottom ash (WBA) was performed by a total acid digestion followed by a chemical analysis. Besides, a sequential extraction procedure (SEP) is conducted to define their partition. The characterisation has shown that the content of valuable metals in the incineration WBA, which was highest in the 0–2 mm fraction was much lower than in concentrated ores commonly used as primary sources. Moreover, the SEP showed little potential for the valorisation of most of the metals, as they are embedded in or bound to a silicic matrix or sintered metal oxides, and so their extraction requires strong-acid digestion or a highly oxidizing environment. This work contributes to the use of residual sources as secondary resources and to the correct management of the end-of-life electrical and electronic equipment.

Evaluation of lead release potential of new premise plumbing materials.

Premise plumbing materials such as pipes, valves, fittings, and faucets are made of various materials, including plastic, stainless steel, copper, and brass/bronze. Although lead pipe has been banned for its use in drinking water supply by most countries in the 1980s, lead is still commonly used as an additive in many plumbing materials for its flexibility and malleability. Certified leaching tests for plumbing materials are usually conducted using relatively mild solutions over short periods which may not reveal the true risk of lead exposure when these materials are used. The objective of this study is to investigate the extents of lead release from commonly used premise plumbing materials into drinking water. The maximum lead leaching potential for pluming material was operationally determined using high strength acidic EDTA solutions (pH 4, EDTA = 100mg/L) for a stagnation time of 3days for a total period of up to 1month. Lead leaching from each plumbing material was also evaluated using reconstituted tap water. Brass- and bronze-based plumbing materials were found to release dangerous levels of lead. Surface lead weight percentage obtained using SEM-EDX and lead weight percentages of the material body obtained using strong acid digestion were found to positively correlate with lead release. A re-examination of the appropriateness of current certified leaching tests and a more stringent regulation on the use of lead as an additive for plumbing materials should be considered.

SPATIAL VARIABILITY OF HEAVY METAL POLLUTION POTENTIAL FROM AN URBAN ROAD NETWORK

This study investigated the spatial variability of heavy metal emission patterns and associated measures of contamination on Riccarton Campus at Heriot-Watt University in Edinburgh, Scotland. Road deposited sediments were collected from 12-different sites representing typical urban/sub-urban road layout over a 10 month period covering seasonal variations. The heavy metal concentrations of the road sediments collected from different sites of a road were determined by strong nitric acid digestion and atomic absorption spectrometry. The contamination levels of the heavy metals in the road deposited sediments were assessed by the accumulation index, the degree of contamination and the ecological risk index. The outcomes of the investigation showed highly site-specific heavy metal emissions that primarily varied with road lay-out, with also influences from road surface condition, surrounding land use and traffic volume. The degree of contamination and the associated ecological risk index revealed that bus stops, a road bend, a road with speed control measures and a road intersection site were the pollutant hot-spot areas among all the sites that may likely pose moderate to considerable levels of pollution to the nearby water environment.

AN ASSESSMENT OF HEAVY METALS POLLUTION POTENTIAL OF ROAD SEDIMENT DERIVED FROM A SUBURBAN ROAD NETWORK UNDER DIFFERENT WEATHER CONDITIONS

The quantification of heavy metals in dry and wet weather derived (runoff and snowfall) sediment from roads, under three different environmental conditions, has indeed the potential to allow improved understanding on urban diffuse pollution. With that aim, the reported study determined the concentrations of Cd, Cu, Pb, Ni, Cr and Zn in road sediment, which are reported to be found in elevated level in the road-traffic environment, and associated pollution levels at four different sites, representing a typical suburban road lay-out, as part of a 10 months field and laboratory studies. The heavy metal concentrations in sediments are determined by strong nitric acid digestion and atomic absorption spectrometry. The results reveal that road sediment contain significant amounts of heavy metals and their concentrations vary with sediment type and size fraction (wet weather, snow and dry sediments), and between sampling sites according to the site specific attributes rather than traffic volume alone. The metal concentrations among three different environmental conditions are found in the order of rainfall-runoff, snow and dry sediment associated with smaller size fractions, in general. Contamination assessment suggests that road sediment may likely pose a moderate to considerable level of ecological risk to the nearby water environment which need attention while designing sustainable urban drainage for roads.

A new sample preparation method for crude or fuel oils by mineralization utilizing single reaction chamber microwave for broader multi-element analysis by ICP techniques

The objective of this study was to develop an effective and routine single sample preparation method to accurately and precisely analyze multiple elements (up to 57) in crude oils using both an inductively coupled plasma-optical emission spectrometer (ICP-OES) for high abundance elements and a triple quadrupole-inductively coupled plasma-mass spectrometer (QQQ-ICP-MS) (or ICP-MS) for low abundance trace and ultra-trace elements. A critical aspect of this study was to develop a single sample preparation method that could be effective in analyzing the largest number of quantifiable elements with instruments used in tandem to cover a wider and more practical combined dynamic range. Three sample preparation techniques were investigated and tested, including high pressure combustion with strong-acid digestion, high pressure and high temperature strong-acid digestion within Parr bombs, and high temperature and high pressure digestions in a Single Reaction Chamber (SRC) microwave. For the combustion method, no element showed recovery above 75%, thus this method was deemed unacceptable for accurate and precise analysis of crude oil. Average recoveries ranging from 94% to 106% for 19 analytes were achieved with high pressure and high temperature acid digestion within Parr bombs. A drawback of the method, however, was a rather small sample sizes (100mg) that could be achieved without venting, which places limitations on detection and quantitation limits of large numbers of low abundance analytes in natural crude oils. The best of the SRC microwave-assisted acid digestion tests, however, was also shown to be acceptable for 19 analytes using a certified organometallic standard, with average recoveries ranging from 93% to 113%. Because of rapid sample throughput and the larger sample sizes (1.2g sample size per digestion session) that can be accommodated with the single reaction chamber microwave digestion technique, better method detection and quantification limits and high precision on a range of low abundance elements could be achieved. We also then successfully tested the recovery of 53 elements with this SRC microwave method by adding a multi-element spike to Conostan base oil. This optimum SRC digestion method tested was then used to examine a NIST natural crude oil research material (NIST RM 8505) in an attempt to quantify up to 57 elements. The mean vanadium concentration (mass fraction) is reported as 390±0.4µg/g, the mean value of 5 replicate digestions by our method, which agrees well with the recommended value for the only element recommended for NIST 8505 of 390±10µg/g. The number of quantified analytes for the RM 8505 was further extended to a total of 52 elements with RSDs <5% for 38 elements, between 5% and 10% for 10 elements, and between 10% and 15.6% for 4 elements, all of which met our acceptability limits set at ≤20% RSD. Of the 57 elements analyzed in RM 8505, certain elements B, Nb, and W, although above method quantitation limits, were judged unacceptable because RSDs were ≥31.4%, whereas Ag and Tl were below method quantitation limits, and their RSDs were ≥44.2% and judged unacceptable. However, these elements have been quantified in other natural crude oils with higher abundances, which indicates that up to 57 elements can be potentially assessed in crude oils or refined oils with this method. The NIST RM 8505 crude oil reported here and others are being evaluated as potential natural crude oil standards to provide references values for more routine multi-element analysis.

Diatom Detection Using Enzyme Combined with Strong Acid Digestion Method

To detect diatom in the organs of drowners by enzyme combined with strong acid digestion method, and evaluate its application value. A total of 40 cases which have been identified as drowning in local region were collected. Samples of the lung, liver, kidney, and the water of the scene were also gathered from each case. Strong acid digestion method, enzyme combined with strong acid digestion method, and enzymic digestion method were respectively performed to detect the diatom in the samples. The comparative analysis was made on digestion time, digestive power and detection rate of diatom, etc. Enzyme combined with strong acid digestion method was significantly better than enzymic digestion method on digestion time and digestive power; enzyme combined with strong acid digestion method were obviously superior to strong acid digestion method on the detection rate of diatom. Enzyme combined with strong acid digestion method combines the advantages of strong acid digestion method and enzymic digestion method. It has the characters of operation safety with little pollution to environment, which is worthy of further popularization and practice.

Manganese and Mn/Ca ratios in soil and vegetation in forests across the northeastern US: Insights on spatial Mn enrichment

Manganese (Mn) cycling in the Critical Zone is important because of its role as an essential nutrient and potential toxicity to plants and organisms. Quantifying Mn enrichment in terrestrial environments has been limited since Mn is monoisotopic. However, elemental ratios of Mn/Ca ratios may be used to determine spatial Mn enrichment and in aboveground and belowground pools. The objectives of this study were to quantify the spatial variation in Mn concentrations and Mn/Ca ratios in foliage, bolewood, forest floor, and mineral soil horizons across the northeastern United States and compare Mn/Ca ratios to estimate enrichment. Forest floor and mineral soil samples were collected from 26 study sites across the northeastern United States and analyzed by strong acid digestion. Foliage and bolewood was collected from 12 of the 26 sites and analyzed for total Mn and Ca. Our results show forest floor and mineral soil horizon Mn concentrations and Mn/Ca ratios were higher at Pennsylvania and New York sites than New Hampshire and Vermont sites. Using a modified isotope equation, enrichment factors (EF) for Mn/Ca ratios were calculated to be ~3.6 in the forest floor, upper and lower mineral soil horizons at sites in New York and Pennsylvania compared to reference sites in New Hampshire and Vermont. Foliar and bolewood Mn concentrations also decreased from Pennsylvania towards New Hampshire. Moreover, foliar and bolewood Mn concentrations were strongly correlated to forest floor, upper, and lower mineral soil Mn concentrations. It was hypothesized that internal cycling (uptake, throughfall, and litterfall) of Mn controls retention of enriched Mn in forests. Geologic influences from a lithologic gradient and soil pH gradient could also influence Mn enrichment in addition to Mn pollution. Ratios of Mn/Ca and other elemental ratios hold promise as geochemical tracers but require further development.

Short-term leaching study of heavy metals from LD slag of important steel industries in Eastern India

Considering Linz-Donawitz (LD) slag as a waste material for its bulk utilisation, there is a possibility that heavy metals will leach to environment. It necessitates the study on physical, chemical, mineralogical and heavy metals leaching characteristic of LD slag. Short-term leaching procedures like batch leach test (BLT), toxicity characteristic leaching procedure (TCLP), strong acid digestion test (SADT) and American Society for Testing and Materials (ASTM) shake test were carried out for assessing heavy metals leaching potentiality. As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Se, V and Zn were leached from LD slag from three major steel industries i.e. Roulkela, Bokaro and Tata Steel Plants of India and were analysed by inductively coupled plasma optical emission spectrometer (ICP-OES). Most of the heavy metals like Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn showed relatively lesser leachability. Toxic heavy metals like As, Cd, Se and V were not leached by BLT, TCLP as well as ASTM shake test and were below detection limit. Rourkela LD slag heavy metals leaching were relatively higher than Bokaro and Tata Steel Plant LD slag and were below permissible limit. The present study reflects about non-hazardous nature of LD slag.

Investigating the phytoavailability of trace elements in contaminated agricultural soils and health risks via consumption of water spinach grown under field conditions in Zhuzhou, China

In this study, the phytoavailability of trace elements from contaminated agricultural soils to water spinach grown under field conditions in Zhuzhou, China was investigated using three single extraction methods: CaCl2, HAc, and acid ammonium acetate-EDTA (AEDTA) compared with a strong acid digestion method. The soils are primarily contaminated by Cd (4.16 ± 5.98 mg kg−1) and Pb (152 ± 160 mg kg−1), followed by Zn (403 ± 443 mg kg−1), Cu (60.5 ± 29.4 mg kg−1) and As (39.1 ± 36.0 mg kg−1). The main pollutants in water spinach grown in this area are Pb and Cd. The estimated dietary intakes of Cd, Pb and As in some sampling sites were higher than the tolerable limits, indicating that the potential health risks from exposure to these three elements through consumption of water spinach need more attention. Importantly, water spinach has an increased propensity for Cd phytoextraction in contaminated soils with an average bioaccumulation factor of higher than 1, whereas Pb in the edible parts of water spinach is probably present from atmospheric deposition. Statistical analysis indicated that more aggressive extraction procedures (HAc or AEDTA) were better able to predict the phytoavailability of trace elements. Moreover, the phytoavailability of Pb, Cd and Zn could also be well predicted by their total concentrations in soils. Although the trace elements content in water spinach could mostly be explained by total or extractable concentrations, the regression predictions were further improved by the incorporation of soil properties.

Iodide-assisted total lead measurement and determination of different lead fractions in drinking water samples

Lead and its compounds are toxic and can harm human health, especially the intelligence development in children. Accurate measurement of total lead present in drinking water is crucial in determining the extent of lead contamination and human exposure due to drinking water consumption. The USEPA method for total lead measurement (no. 200.8) is often used to analyze lead levels in drinking water. However, in the presence of high concentration of the tetravalent lead corrosion product PbO(2), the USEPA method was not able to fully recover particulate lead due to incomplete dissolution of PbO(2) particles during strong acid digestion. In this study, a new procedure that integrates membrane separation, iodometric PbO(2) measurement, strong acid digestion and ICP-MS measurement was proposed and evaluated for accurate total lead measurement and quantification of different lead fractions including soluble Pb(2+), particulate Pb(II) carbonate and PbO(2) in drinking water samples. The proposed procedure was evaluated using drinking water reconstituted with spiked Pb(2+), spiked particulate Pb(II) carbonate and in situ formed or spiked PbO(2). Recovery tests showed that the proposed procedure and the USEPA method can achieve 93-112% and 86-103% recoveries respectively for samples containing low PbO(2) concentrations (0.018-0.076 mg Pb per L). For samples containing higher concentrations of PbO(2) (0.089-1.316 mg Pb per L), the USEPA method failed to meet the recovery requirement for total lead (85-115%) while the proposed method can achieve satisfactory recoveries (91-111%) and differentiate the soluble Pb(2+), particulate Pb(II) carbonate and PbO(2).

Emission patterns of traffic-related metals and associated contamination in road deposited sediment

Road deposited sediment (RDS) is regarded as sinks for metal pollutants derived from road-traffic that may pose a danger for the nearby water environment. The reported study aims to analyse RDS build-up and associated metal emission patterns using Riccarton Campus of Heriot Watt University, Edinburgh, Scotland as a study site. The RDS samples were collected from four different sites over a four month period to characterise the influence of road lay-out on metal emissions. The metal concentrations associated with the RDS were determined by strong nitric acid digestion and atomic absorption spectrometry. The outcomes of the investigation show highly site-specific variability of the RDS build-up primarily linked to road lay-out, and that road surface conditions and surrounding land use influenced the results. Similarly, irrespective of traffic volume, site attributes were found to be the drivers for the observed differences in metal concentration. Furthermore, a significant proportion of pollutants were found to be associated with finer particles (size < 63 µm) and that RDS exhibited moderate to strong levels of pollution for Zn, Cu and Pb.

Assessment of heavy metals emission from traffic on road surfaces

Abstract This study aims to analyse RDS heavy metal concentrations on road deposited sediment (RDS) using Riccarton Campus of Heriot-Watt University, Edinburgh, Scotland as a study site. RDS samples were collected at two transverse positions from different sites over a 4 month period in order to describe the influence of traffic on heavy metal emissions. The heavy metal concentrations of the RDS were determined by strong nitric acid digestion and atomic absorption spectrometry. The mean concentrations for Zn, Cu, Cd, Cr, Ni, Pb and Fe were found to be 213, 57, 1, 16, 15, 118, and 13497 mg kg-1 from samples near to the curb and 211, 79, 2, 15, 9, 35, and 14276 mg kg−1 from samples 1 m from the curb respectively. Furthermore for both positions the highest concentrations for all metals were associated with the finer fraction (&lt;63 µm) and stronger correlations between the metals were found further from the curb than near the curb, indicating that metals accumulating on the road surface further from the curb may likely be from the same source (traffic), while the sources of metals near the curb are more diverse.

Exploring Amino Acid Side Chain Decomposition Using Enzymatic Digestion and HPLC-MS: Combined Lysine Transformations in Chlorinated Waters

Characterizing the transformations of polypeptides is important across a broad range of scientific disciplines. As polypeptides are an important constituent of dissolved organic matter within seawater and freshwater, it is important to understand their (bio)geochemical fate. Oxidants, formed in blood as part of the immunological response or applied to waters for disinfection, react with polypeptides to form transformation products that may exert toxicity. An analytical method was developed to characterize and quantify modifications to the side chains of amino acid residues within polypeptides. Enzymatic digestion of polypeptides using Pronase E, a protease cocktail, proved preferable to common strong acid digestion techniques, because the circumneutral pH conditions employed during enzymatic digestion prevent artifacts arising from extreme pH conditions. Lysine nitrile, one of the predicted transformation products of lysine residues within polypeptides, was destroyed during strong acid digestion but not enzymatic digestion. Due to the potential variability in enzymatic digestion efficiencies, the liberation of a mass-labeled leucine monomer from an octapeptide spiked standard was employed as a measure of complete digestion efficiency for each sample and enabled quantification of modified amino acid residues within polypeptides. A multivariate statistical analysis was conducted to evaluate the influence on digestion efficiency of Pronase E loadings, salinity, natural organic matter concentration, and pH across the range of conditions relevant to blood, seawater, and concentrated freshwaters and disinfected drinking/recreational waters. At Pronase E loadings of 10 mg, the analysis indicated that digestion efficiencies ranged from 25 to 55% over the range of conditions expected for typical drinking waters concentrated from 1 L to 10 mL. The analytical method was applied to triplicate 1 L samples of a chlorinated tap water and a chlorinated indoor pool water. For the tap water, the digestion efficiency was 47.2% (+/-11.1% relative standard deviation), and the lysine nitrile concentration was 104.6 ng/L (+/-6.8 ng/L standard deviation). For the pool water, the digestion efficiency was 23% (+/-15% relative standard deviation); although the occurrence of lysine nitrile was verified, matrix effects must be overcome for quantification.

Heavy metal pollution monitoring using the brown seaweed Padina durvillaei in the coastal zone of the Santa Rosalía mining region, Baja California Peninsula, Mexico

The coastal marine sediments near Santa Rosalia on the eastern coast of the Baja California Peninsula (Mexico) are heavily polluted by metals due to copper mining and smelting over the past century (up to 1984). The present study compares the accumulation of metals in the brown seaweed Padina durvillaei from the central segment of the coast of Santa Rosalia (polluted by Co, Cu, Mn and Zn) and from two segments north and south of the known “hot spot”. The seaweed samples were collected in May and August 2004 and June 2005 at 13 stations located along the Santa Rosalia mining region. Heavy metal concentrations were measured by instrumental neutron activation analysis (Co and Fe) directly in dried homogenized subsamples or by flame atomic absorption spectrophotometry (Cd, Cu, Mn, Ni, Pb and Zn) after complete strong acid digestion of sub-samples. The means and standard deviations of the concentrations in dry tissues of Padina durvillaei specimens for all the studied metals and stations lie in the following sequence: Cd (3.6 ± 1.6 mg kg−1) < Co (6.5 ± 6.1 mg kg−1) < Pb (7.8 ± 6.2) < Ni (9.96 ± 5.28 mg kg−1) < Cu (53 ± 38 mg kg−1) < Zn (63 ± 43 mg kg−1) < Mn (295 ± 269 mg kg−1) < Fe (2243 ± 2325 mg kg−1). This increase of the average concentrations was statistically significant. Principal Component Analysis showed that Factor 1 (36.46%) displays high positive loadings for Co, Cu, Mn and Zn, reflecting the influence of local anthropogenic pollution on the seaweed composition, while Factor 2 (26.91%) is important for Co, Fe and Ni and probably corresponds to the adsorption or accumulation of terrigenous elements of the regional origin, while Factor 3, with a high positive loading for Pb and a high negative loading for Cd, is probably controlled by local and regional anthropogenic input of Pb and episodic supply of Cd by local upwellings. The results of ANOVA for each element do not show any significant differences between the average concentrations for Cd, Fe, Ni and Pb in the seaweed of the three segments, or between the central and southern segments for Cu, Mn and Zn. Cobalt contents in the seaweed from the northern and central segments are, however, significantly different from the southern segment. This indicates that element concentrations in Padina durvillaei generally do not follow the drastic increases and gradients of Cu, Co, Mn and Zn contents detected in surface sediments. The apparent contradiction could be explained by a low geochemical mobility of these metals in the polluted sediments, composed mainly of stable residues of smelter wastes, with very low content of organic matter usually driving diagenetic mobilization of some metals into interstitial waters and then to the overlying water.