USEPA Drinking Water Standards Research Articles

Preferential flow of phosphorus and nitrogen under steady‐state saturated conditions

AbstractRepeated broiler litter application on agricultural lands can cause nutrient enrichment of subsurface effluent, especially with the existence of preferential flow through soil macropores. Previous studies quantifying soil macropores have not attempted to establish a connection of soil macropore characteristics with the subsurface nutrient (nitrogen [N] and phosphorus [P]) losses, across different topographical locations in the field. This study investigated the effect of broiler litter application and preferential flow on subsurface nutrient transport (N and P) at different topographical positions (upslope, midslope, and downslope) in a no‐till pasture field located in Alabama, USA. Twelve intact soil columns (150 mm id and 500 mm length) were used, and the nutrient leaching measurements from laboratory experiments were linked to soil macropore characteristics quantified using X‐ray computed tomography image analysis and solute transport modeling. Treatments included surface broadcast broiler litter (5 Mg ha−1, on dry basis) and unamended control. Leachates were analyzed for dissolved reactive P (DRP), total P (TP), and nitrate + nitrite‐N (NO3− + NO2−–N). The bromide breakthrough curves provided evidence of preferential flow in all columns. Litter application significantly increased leachate P concentrations, and average TP and DRP concentrations were significantly higher in the leachate from upslope columns compared to those at downslope location. The NO3−–N concentrations in leachate exceeded the US EPA drinking water standard of 10 mg L−1 in all the treatment columns. The highest flow‐weighted mean concentrations of TP and DRP, at 2.7 and 2.5 mg L−1, respectively, were recorded in the upslope columns. Soil physicochemical properties and nutrient leaching losses varied substantially across topographical positions, indicating a need for variable litter application rates to reduce P build‐up and subsequent leaching in vulnerable locations within the field. The relevance of the effect of topographic position on nutrient leaching found in this study should be further tested by investigating a wider range of slopes and soil types in pastures.

Sensitive Electrochemical Determination of Bisphenol a Using a Disposable, Electrodeposited Antimony-Graphene Nanocomposite Pencil Graphite Electrode (PGE) and Differential Pulse Voltammetry (DPV)

Herein the synergistic properties of electrochemically reduced graphene oxide–antimony nanoparticles (ERGO-SbNPs) were leveraged for the ultrasensitive determination of bisphenol A (BPA) in water samples using disposable pencil graphite rods. A novel pencil-graphite multi-electrode array was utilized as the coating tool resulting in the production of highly reproducible and disposable single-use ERGO-SbNP-coated pencil graphite rods. This coating method effectively mitigated the fouling caused by BPA by-products during oxidation. The analytical determination of BPA oxidation on the single-use ERGO-SbNP-coated pencil graphite rods demonstrated an impressive 0.0,125 µM detection limit, surpassing the USEPA drinking water standard of 0.087 µM. Furthermore, the developed electrochemical sensor exhibited exceptional reproducibility for BPA in tap water samples from Western Cape, South Africa with few interferences. The study’s findings not only highlight the sensor’s superior performance but also present a promising alternative to existing anti-fouling measures.

A bionic solar-driven interfacial evaporation system with a photothermal-photocatalytic hydrogel for VOC removal during solar distillation

Solar-driven interfacial evaporation is a breakthrough water treatment method because it harvests solar energy for producing clean water. However, evaporated volatile organic compounds (VOCs) in distilled water are the greatest barrier to this technology. Herein, a bionic solar-driven interfacial evaporation system integrating photothermal and photocatalysis technology was developed based on a new combined material TiO2/Ti3C2/C3N4/PVA (TTCP) hydrogel as an evaporator. Phenol-contaminated water, especially actual water (seawater, lake water and reclaimed water), is used to evaluate the water evaporation and VOC photocatalytic degradation performance. The results show that the evaporation rate of TTCP hydrogel was 1.54 kg m − 2h − 1 under 1 kW m − 2, and the removal efficiency of phenol ranged from 69.4% to 100% at different concentrations (1–50 mg/L) in source water. Particularly, the capacity of the bionic evaporator was first evaluated for different types of actual water. Despite the initial TOC (38.12–57.93 mg/L) and total dissolved solids (TDS, 1.35×103–8.78×104 mg/L) for seawater, lake water and reclaimed water being very different, the TDS was decreased by more than two orders of magnitude, below the US EPA drinking water standard (500 mg/L). The maximum TOC removal efficiency reached 80% under simulated sunlight (1 kW m − 2), which is comparable to the efficiency of the ultrafiltration technique previously reported except for seawater. Furthermore, real sunlight (average solar irradiation ∼0.82 kW m- 2) was used to assess the practicability. The bionic evaporator can produce 0.72 kg m − 2h − 1 of vapor from reclaimed water and run with steadily efficient TDS and TOC removals, reaching 99% and 74%, respectively. This technology, as a small, decentralized water treatment method, is a good choice for remote and off-grid areas.

The Clean Water Act and biosolids: A 45‐year chronological review of biosolids land application research in Colorado

The 1972 U.S. Clean Water Act set forth the generation of biosolids. In Colorado, biosolids land application research began in 1976 and continues today. Pastureland research suggested that sewage effluent could effectively be land applied to benefit aboveground plant growth and to polish water prior to reaching receiving waters. Forest wildfire-affected ecosystems can also benefit from biosolids applications; application rates of up to 80 Mg ha-1 can lead to greater plant establishment, soil microbial activity, and nutrient turnover and reduced nutrient and heavy metal concentrations in runoff below livestock and USEPA drinking water standards. Long-term (24-yr) observations in oil shale-mined lands showed that biosolids (up to 224 Mg ha-1 ) can have a positive effect on microbial-mediated nutrient cycling and, in turn, on aboveground plant community structure. Biosolids applications of up to 40 Mg ha-1 in high-elevation shrubland ecosystems, dominated by Mo-containing shale deposits, can aid in reducing imbalances between Mo and Cu in soils and plants; excessive plant Mo, when consumed by ruminants, can lead to molybdenosis. Biosolids and lime applications (both at 224 Mg ha-1 ) have been shown to improve long-term reclamation success on acid-generating, heavy metal-containing fluvial mine tailings. Thirty years of grazing land research, focused on soil and aboveground plant benefits, illustrate that soil health and plant productivity can be improved to the greatest extent at biosolids application rates close to 10 Mg ha-1 . Finally, 40 yr of dryland agroecosystem research (a) have helped identify biosolids N fertilizer equivalency (∼8kg N Mg-1 ) and thus dryland winter wheat application rates (e.g., 4.5-6.7 dry Mg ha-1 ); (b) have identified first-year mineralization rates of 25-32%; (c) dispute the "time bomb" theory by showing that plant metal uptake follows an exponential rise to a maximum; (d) showcase economic return to producers via increased wheat grain protein content; (e) suggest that biosolids-borne proteins and their degradation products are labile C and N sources; (f) have led to long-term tracking of micronutrients and heavy metals in soils and revealed that plants-soil concentrations will not lead to groundwater degradation and that plants are safe for human consumption; and (g) have shown that biosolids provide Zn, helping to overcome soil deficiencies and enhancing Zn biofortification in wheat grain. This latter point is important because ∼2 billion people globally suffer from Zn deficiencies. Forty-five years of research in Colorado have proven that biosolids can enhance environmental quality, improve soil health, and produce healthy food products.

Treatment for removing radium in soil and groundwater

The results of 226Ra activity concentration measurements in 50 soil and groundwater samples in Ninh Son region, Vietnam were evaluated in the present study. Average activity concentration in the soils was significantly higher than the worldwide average concentration in soils published by UNSCEAR, 2008. 90% of groundwater samples had concentrations of 226Ra that were higher than the USEPA drinking water standard. The results showed that there was a linear correlation between the 226Ra radioactivity in the soils and the concentration of 226Ra in the groundwater samples. The procedure for removal of 226Ra from soil and groundwater samples was built upon the chemistry behavior of radium. 226Ra in contaminated groundwater samples was removed by using MnO2 fiber. The removal efficiency of 226Ra reached ∼ 91% for the groundwater samples and ∼ 70% for the soil samples. Chemical removal of 226Ra from soils was investigated using a three-step extraction procedure (Easily leachable and exchangeable, Acid-reducible, and Oxidisable-organic). A moderate mobility of 226Ra (22–52%) was noted and mainly found in acid-reducible fractions, which suggests that 226Ra is mainly bound to Fe/Mn oxides and hydroxides. A multiple regression indicates that the 226Ra removal efficiency appears to be significantly dependent on Fe/Mn and organic matter content.

Nonpoint source arsenic contamination of soil and groundwater from legacy pesticides.

Arsenic (As) contamination in wells is common throughout the northeastern United States. It is well documented that lead-arsenate (PbHAsO4 ) pesticides were widely used on fruit tree orchards from the 1890s to 1950s. This study evaluates the potential for As contamination of groundwater from former orchards in Connecticut, where there were over 47,000 orchards in 1935. A proximity analysis involving 189 orchards and 114 domestic wells was conducted to assess the spatial relationship between historic orchards and As in wells. Field studies were then conducted to characterize As and lead (Pb) distributions in soils and wells near historic orchards. The proximity analysis found that the wells with no detected As were further away from historic orchards and had fewer historic orchards within their vicinity when compared with wells that contained As. The field investigations found that elevated levels of As and Pb were widespread in soils from orchards established by 1951, with some As concentrations exceeding 200ppm. In some soils, As and Pb were leachable at concentrations exceeding USEPA drinking water standards in synthetic precipitation laboratory tests. It was also found that the wells nearest to the impacted soils tended to contain the highest As concentrations, while the wells located in areas that were forested prior to 1970 contained no As. Overall, this study found that As and Pb from legacy pesticide residues are still abundant in former orchard soils and that a strong spatial relationship exists between As-contaminated wells and historic orchards. Greater consideration should be given to historic orchard soils as a potential contributing nonpoint source of As to the groundwater in Connecticut, where domestic well contamination rates are high.

A pilot study on the feasibility of testing residential tap water in North Carolina: implications for environmental justice and health

In 2015 alone, community water systems serving about 21 million Americans violated the United States Environmental Protection Agency's (US-EPA) water quality standards. While water at community treatment and distribution centers is regularly monitored and tested, little is known about pollutants in the water systems at the household level. This pilot study assessed the feasibility of (1) testing for the presence and concentration of 14 contaminants and physicochemical parameters in household tap water in a low-income neighborhood and (2) using community engagement for recruitment and citizen science approaches to data collection. We used a multistage approach that included geo-mapping to delineate testing sites, community engagement for recruitment and citizen science approaches to increase the response rate. We used a 14-in-one dipstick test designed to measure trace amounts of heavy metals, non-metallic elements, and physicochemical water properties in drinking water in a sample of 70 homes. In 50%, 25%, and 7% of water samples tested, the concentration of mercury, lead, and chromium, respectively, were higher than US-EPA drinking water standards. Citizen science approaches were effective for increasing response rates and low-income household participation in water quality testing. The overlap between poverty, older homes, and high concentrations of potentially toxic metals in drinking water presents concerns for community health. Our pilot community engagement and citizen science approaches are likely scalable and would be of benefit to both the scientific community and to municipalities with constrained budgets. Future studies may examine the role of the principles of environmental justice in the distribution and prevalence of toxic elements in drinking water.

Chromium, manganese, nickel, and cobalt mobility and bioavailability from mafic-to-ultramafic mine spoil weathering in western Massachusetts, USA.

Fragmented ultramafic bodies in New England were important mineral resources until the early twentieth century, yet few studies have addressed their potential to release trace metals to terrestrial and aquatic environments. Here, we evaluate the release of four trace metals (Cr, Co, Mn, and Ni) from a historic serpentine-talc "soapstone" quarry in Blandford, MA, USA. Soil pits, sediment and rock samples, and stream water samples were collected from upslope undisturbed areas, within the mine spoils and mine face, and downslope of the mine. In order to provide a bottom-up approach for understanding metal release, careful petrographic analysis, electron-dispersive spectroscopy, and wavelength-dispersive spectroscopy were employed to provide first-order insight into the mineralogy of the deposit and a determination of potential metal-bearing phases. Trace metals were primarily observed in ultramafic sheet silicates, primary Fe-oxides, and interstitial weathering-related sulfates. Bulk rock concentrations were Cr (1550mgkg-1), Co (230mgkg-1), Mn (1100mgkg-1), and Ni (1960mg kg1); Cr, Co, and Ni were elevated relative to the surrounding country rock. However, soils and sediments total concentrations were comparable to background soil concentrations: Cr (119mgkg-1), Co (73mgkg-1), Mn (894mgkg-1), and Ni (65mgkg-1). Moreover, < 0.5% of the total concentrations were bioavailable (0.1M ammonium acetate extraction), implying that metals are present as insoluble forms. However, ~ 20% of the total Cr, Mn, Ni, and Co concentrations were strong acid extractable, suggesting mobilization over the coming decades. Stream water concentrations of Mn and Cr were < 50µg L-1, below concentrations outlined by USEPA drinking water standards, and WHO water guidelines for Ni. These results suggest that transport of Cr, Mn, Ni, and Co from the serpentine-talc as dissolved compounds or sediments is limited by retention within silicate and oxides.

Density functional theory studies of the adsorption of Cr (VI) on Fe-(hydr) oxide: Gibbs free energies and pH effect

Adsorption of chromium (VI) on iron oxides is a potential removal method from industrial wastewater. Cr (VI) is a toxic specie for human health due to its easy mobility in the environment. Currently, US EPA drinking water standards establish a maximum Cr level of 100 μg/L. Since the adsorption process occurs in the solid/liquid interface, pH is one of the main factors that affect this process and it is a very important parameter to study. Understanding the adsorption process and the molecular geometries of complexes, is essential to predict the environmental transport of Cr (VI) and to develop appropriate models for the remediation of Cr (VI). Therefore, in this work, we describe the adsorption of Cr (VI) onto Fe-hydr (oxides) through computational methods. A complete characterization of the adsorbed surface complexes was performed, and three different pH conditions were simulated (acidic, intermediate and basic). It was found that, the thermodynamic favourability of the different adsorbed complexes was directly related to the pH. Bidentate complex (BB) was the most thermodynamically favourable complex with an adsorption energy of -143.3 kJ/mol under acidic pH conditions.

Potential impact of leaking CO2 gas and CO2-rich fluids on shallow groundwater quality in the Chungcheong region (South Korea): A hydrogeochemical approach

This study evaluates the potential impact of leaking CO2 gas and CO2-rich waters on shallow groundwater quality by focusing on the mobilization of trace elements. For this study, Group I (acidic CO2-rich waters with low TDS), Group II (slightly acidic CO2-rich waters with high TDS), and Group III (CO2-poor waters with low TDS) were sampled in the study area occurring naturally CO2-rich waters. The carbon isotope data (δ13C and 14C) indicate that the dissolved CO2 in CO2-rich water originates from old and deep-seated CO2. Our results show that Group I is formed by the direct input of CO2 gas into recently recharged shallow groundwater, whereas Group II discharging along fractures or wells occurs by long-term CO2-water-rock interactions in the subsurface. Group I shows higher concentrations of trace elements (Al, Ba, Be, Cr, Cs, Fe, Mn, Ni, Rb, and U) than Group III, and its Al and Mn concentrations slightly exceed the US EPA drinking water standard. However, Group II has significantly higher concentrations of trace elements than Group I. In particular, harmful Be exceeds the US EPA drinking water standard by over 6.5-fold. In addition, Fe and Mn exceed the US EPA drinking water standard by 27.7-fold and 16.1-fold, respectively. The higher concentration of bicarbonate by pH buffering in Group II also increases the mobilization of U6+. Our results show that the mobilization of trace elements in the aquifer having little buffering capacity is mainly determined by the degree of CO2-water-rock interactions. This study indicates that upwelling of deep CO2-rich fluids with long-term water-rock interactions can be harmful to shallow potable groundwaters by supplying high levels of trace elements into shallow aquifers.

Naturally occurring radioactive materials (NORM) in the groundwater of two islands with various geologic settings in South Korea

Since 2007, Naturally Occurring Radioactive Materials (NORM) such as uranium-238 and radon-222 etc. in groundwater from the Community Water-supply Systems (CWS) in two islands have been studied in South Korea. In 71 samples from Ganghwa (G) Island, the maximum value of uranium-238 concentration is 72.21 μg/L. 3 CWSs (4.2%) exceeded the Maximum Contaminant Level (MCL) of 30 μg/L for uranium-238. The maximum value of radon-222 activity is 614 Bq/L. 28 CWSs (39.4 %) did not meet the United States Environment Protection Agency (US EPA) proposed Alternative Maximum Contaminant Level (AMCL) of 148 Bq/L for radon-222. At all CWS that did not meet the US EPA’s MCL or AMCL, some appropriate actions were taken such as water treatment, alternative well development, mixing water of different origins, and so forth. In the 52 CWSs of Jeju (J) Island, the maximum value of uranium-238 and radon-222 concentrations are 1.37 μg/L and 94.83 Bq/L, respectively. All values for uranium-238, gross alpha, and radon-222 meet MCL and proposed AMCL of US EPA drinking water standard. The two islands have different geological settings that are believed to be the causes of the big differences in the NORM levels. Geologically an old island has much higher NORM values than a young island formed in the Quaternary Period due to hydrogeological factors such as recharge and infiltration rates of precipitation. The residence times in the aquifers for water-rock (mineral) interactions are very different from each other.

Metals, heavy metals and microorganism removal from spent filter backwash water by hybrid coagulation-UF processes

Abstract Spent filter backwash water (SFBW) reuse has attracted particular attention, especially in countries that experience water scarcity. It can act as a permanent water source until the water treatment plant is working. In this study, the concentrations of Fe, Al, Pb, As, and Cd with total and fecal coliform (TC/FC) were investigated in raw and treated SFBW by hybrid coagulation-UF processes. The pilot plant consisted of pre-sedimentation, coagulation, flocculation, clarification, and ultrafiltration (UF) units. Poly-aluminum ferric chloride (PAFCL) and ferric chloride (FeCl3) were used as pretreatment. The results showed that, at the optimum dose of PAFCl, the average removal of TC and FC was 88 and 79% and with PAFCl-UF process, it reached 100 and 100%, respectively. For FeCl3, removal efficiency of TC and FC were 81 and 72% and by applying FeCl3-UF process, it reached 100 and 100%, respectively. In comparison with FeCl3, PAFCl showed better removal efficiency for Fe, Pb, As, and Cd, except residual Al concentration. Coagulation-UF process could treat SFBW efficiently and treated SFBW could meet the US-EPA drinking water standard. Health risk index values of Fe, AL, Pb, AS, and Cd in treated SFBW indicate no risk of exposure to the use of this water.

Competitive adsorption between arsenic and fluoride from binary mixture on chemically treated laterite

The present paper deals with individual as well as simultaneous removal of arsenic and fluoride from synthetic water using acid-base treated laterite in batch mode along with management of the spent adsorbent. Optimum conditions for maximum removal of both arsenic and fluoride in single component system are found as pH 5, adsorbent dose 20gL−1, contact time 300min with initial concentration of arsenic and fluoride as 500μgL−1 and 10000μgL−1 respectively. Adsorption isotherm data fitted well to Langmuir model and under the optimum conditions the Langmuir adsorption capacity of present adsorbent is found to be 769μgg−1 for arsenic and 526μgg−1 for fluoride. Single component adsorption followed Pseudo 2nd order kinetics. The binary adsorption experiments were performed at the same optimum conditions with varying concentrations of arsenic and fluoride. The combined adsorptions of arsenic in binary systems do not differ much, while fluoride shows antagonistic behavior. The extended Freundlich model is found to best represent the apparent equilibrium adsorption phenomena in binary system. The present adsorbent is able to simultaneously reduce the arsenic and fluoride concentration below permissible limits of USEPA drinking water standards. Solidification technique was used for the management of the spent adsorbent by its immobilization in form of a clay brick. Leaching test results revealed that leaching of arsenic and fluoride from the spent adsorbent is well below the permissible limits as per the USEPA norms.

An Index Approach to Metallic Pollution in Groundwater Sources of South Region of Pemba Island

The South Region of Pemba is one of the two Regions in Pemba Island. Residents within the region depend on groundwater as the main water source for the domestic and other social purposes. This study was conducted to assess the quality of drinking water in different areas of South region of Pemba. In order to evaluate the quality of groundwater in the study area, 17 groundwater samples were collected and analyzed for different physico-chemical parameters. In each water sample, four physicochemical parameters were analyzed, namely, electrical conductivity (EC), total dissolved solids (TDS), pH, and turbidity. For the case of metals, eleven metals, namely, Cd, Co, Cu, Cr (III), Li, Fe, Mg, Ni, Pb, Sr, and Zn were analyzed using standard procedures. The dataobtained were then compared with the available WHO and or USEPA drinking water standards. All the samples had EC and TDS within the recommended limits, while 53% and 29% of the samples had higher turbidity levels and lower pH, respectively than the WHO recommended guidelines. All the samples contained Co, Cu, Fe, Mg, Ni, Pb, and Zn within the maximum admissible limits. According to heavy metal pollution index (HPI), degree of contamination (Cd), and heavy metal evaluation index (HEI), only one area (Mgonanje-1) showed alarming risks. In most water samples, the ratio of concentrations of Li to Ni was greater than 1, while all Sr to Mg ratios were less than 1. Generally, the values of the analyzed physico-chemical parameters were within the recommended maximum admissible limits. However, the study recommends the stakeholders and other responsible authorities to take appropriate and corrective measures for the water sources located at the Mgonanje area.

Petroleum contaminated water and health symptoms: a cross-sectional pilot study in a rural Nigerian community.

BackgroundThe oil-rich Niger Delta suffers from extensive petroleum contamination. A pilot study was conducted in the region of Ogoniland where one community, Ogale, has drinking water wells highly contaminated with a refined oil product. In a 2011 study, the United Nations Environment Programme (UNEP) sampled Ogale drinking water wells and detected numerous petroleum hydrocarbons, including benzene at concentrations as much as 1800 times higher than the USEPA drinking water standard. UNEP recommended immediate provision of clean drinking water, medical surveillance, and a prospective cohort study. Although the Nigerian government has provided emergency drinking water, other UNEP recommendations have not been implemented. We aimed to (i) follow up on UNEP recommendations by investigating health symptoms associated with exposure to contaminated water; and (ii) assess the adequacy and utilization of the government-supplied emergency drinking water.MethodsWe recruited 200 participants from Ogale and a reference community, Eteo, and administered questionnaires to investigate water use, perceived water safety, and self-reported health symptoms.ResultsOur multivariate regression analyses show statistically significant associations between exposure to Ogale drinking water and self-reported health symptoms consistent with petroleum exposure. Participants in Ogale more frequently reported health symptoms related to neurological effects (OR = 2.8), hematological effects (OR = 3.3), and irritation (OR = 2.7).ConclusionsOur results are the first from a community relying on drinking water with such extremely high concentrations of benzene and other hydrocarbons. The ongoing exposure and these pilot study results highlight the need for more refined investigation as recommended by UNEP.

Preliminary Laboratory Evaluation ofIron-Bearing Reactive Media forPesticide Water Treatment

Abstract. Agricultural pesticides are often found in ground and surface waters, and if present in high enough concentrations, create risks to human and ecological health. Filter treatment systems can potentially remove pesticides from water. Therefore, a laboratory investigation was conducted to assess the water treatment capabilities of four iron-bearing reactive media to remove three different organochloride pesticides. The iron-bearing reactive media evaluated were zero valent iron (ZVI), porous iron composite (PIC), sulfur modified iron (SMI), and a synthetic goethite - iron oxide/hydroxide (SG). The three organochloride pesticides tested for removal by the four iron-bearing reactive media were 2,4-D, alachlor, and atrazine. The laboratory investigation included contaminant removal batch tests and saturated solute transport column tests at two hydraulic retention times. Results of replicated contaminant removal batch tests indicate, that of the four iron-bearing reactive media evaluated, PIC is clearly the most effective for water treatment of 2,4-D, alachlor, and atrazine. The initial batch test concentration for each of the three pesticides was 500 ppb, and the replicated PIC batch tests averaged more than 98% removal for alachlor and greater than 99% removal of 2,4-D and atrazine. Pesticide water treatment capabilities for PIC were further assessed by comparing results between control (no filter material - empty column) and PIC saturated solute transport column tests. In contrast to an influent concentration entering the PIC column of 500 ppb for each of the three pesticides, the effluent 2,4-D, alachlor, and atrazine concentrations exiting the PIC column were less than 0.3 ppb, even when the hydraulic retention time was only 4 min. Importantly, all PIC column test effluent pesticide concentrations were well below USEPA drinking water standards. Consequently, this preliminary laboratory assessment indicates that the PIC filter material exhibits promise for organochloride pesticide water treatment; however, more laboratory and field testing is needed to fully determine PIC capabilities.

Europium(III) complex-functionalized magnetic nanoparticle as a chemosensor for ultrasensitive detection and removal of copper(II) from aqueous solution.

Ultrasensitive, accurate detection and separation of heavy metal ions is very important in environmental monitoring and biological detection. In this paper, a highly sensitive and specific detection method for Cu(2+) based on the fluorescence quenching of a europium(III) hybrid magnetic nanoprobe is presented. This nanoprobe can detect Cu(2+) over a wide pH range (5.0-10.0) with a detection limit as low as 0.1 nM and it can be used for detecting Cu(2+) in living cells. After the magnetic separation, the Cu(2+) concentration decreased to 1.18 ppm, which is less than the US EPA drinking water standard (1.3 ppm), and more than 70% Cu(2+) could be removed when the amount of nanocomposite 1 reached 1 mg.

Soil profile sulfate in irrigated southern high plains cotton fields and Ogallala groundwater

Sulfate (SO4) is one of the most important anions in soils and groundwater in semiarid regions, including west Texas. Crops9 sulfur (S) requirement is about 10% to 20% of the nitrogen requirements. However, there is far less information on soil test SO4-S (S in the SO4 form [sulfate-S]) for the western United States, compared to the humid eastern United States. The deposition of S from the atmosphere has declined nationwide, as coal-fired power plants have been scrubbing their emissions of S. This, combined with greater cotton yields and the lack of S fertilization on the Texas Southern High Plains (SHP) point to the need for a soil profile SO4-S assessment. The first objective of this study was to assess residual soil profile SO4-S content in irrigated cotton (Gossypium hirsutum) fields across a range of soil types and counties of the Texas SHP. The second objective was to compile regional SO4-S concentration data from the Texas Water Development Board irrigation well water quality database and analyze Ogallala groundwater SO4-S levels by county, soil map unit, and well depth. Soil profile (0 to 0.9 m [0 to 36 in]) SO4-S content ranged from 120 to 475 kg ha−1 (107 to 424 lb ac−1) among seven center-pivot fields sampled. About half of this S was in the 0.6 to 0.9 m (24 to 36 in) soil layer, which typically was sandy clay loam or clay loam in texture. Well water SO4-S concentration ranged from 9 to 220 mg L−1 (ppm) in clayey soils with deep groundwater to sandy soils with shallow groundwater, respectively. Groundwater SO4-S concentration was greater than the USEPA drinking water standard of 83 mg L−1 in 32% of the wells, especially in the southeastern corner of the study area. There was no consistent relationship between soil map unit and SO4-S content in the soil profile (0 to 0.9 m). A significant negative relationship between well depth and well water SO4-S concentration was observed in all the eleven-county study area of the SHP of West Texas. In conclusion, soil profile SO4 content to 0.9 m is high in SHP irrigated cotton fields and in most cases should be adequate for crop S nutritional requirements.

The exchangeability and leachability of metals from select green roof growth substrates

Batch extraction and leaching studies were conducted with potential green roof substrates (e.g., Axis, Arklayte, coal bottom ash, Haydite, Lassenite, lava rock, and composted pine bark). The results indicated that these materials would not likely be sources of Cr, Cu, Fe, Ni, or Zn and that Lassenite would be considered a source of Mn if the leachate concentrations were compared to USEPA drinking water standards for these elements. Lassenite would not be a source of Mn if the data was compared to a USEPA standard for Mn toxicity to aquatic life. All of the substrates tested leached Cd and/or Pb concentrations that exceeded the USEPA water quality standards at least once during the 6-month leaching study, so these materials may be potential sources of Cd and Pb in green roof storm water runoff. The leaching of Cu, Cd, Fe, Mn, Pb, and Zn was differentially influenced by time and/or the presence of a single Sedum hybridum ‘immergrauch’ plant. The leaching of Cd, Cu, and Pb displayed complex, three-way interactions between main effects (substrate type and the presence or absence of a plant) and between leaching events. For all substrates except Lassenite, the presence of a S. hybridum plant decreased the leaching of Pb over time. The leaching of Cd was generally enhanced by plants for most substrates with time. Collectively the results suggest that changes in the biogeochemical conditions within green roof systems may alter metal solubility, decreasing the leaching of some elements and increasing the leaching of others.

NEWater—multi safety barrier approach for indirect potable use

Singapore, a small island city-state depends on four sources, namely local catchment, imported water from Malaysia, desalinated water, and NEWater, to provide for its daily water consumption of about 1.36 million m3 per day. NEWater, a high grade reclaimed water, is key in achieving water sustainability through the multiplying effect of water reuse. In addition to being used for direct non-potable use (DNU) in wafer fabrication processes and other industrial processes, NEWater is being injected into surface reservoirs for indirect potable use (IPU). To ensure the safety of NEWater for IPU, PUB has adopted a multi barrier safety approach. The multi safety barrier approach starts from source and extends to taps in households in stages, namely source control; greater than 85% of wastewater from domestic source; comprehensive secondary wastewater treatment; microfiltration (MF) process, reverse osmosis (RO) process and ultra-violet (UV) disinfection in NEWater production; natural attenuation in surface reservoirs; as well as conventional water treatment process of coagulation, flocculation, sand filtration and disinfection. The approach is further enhanced by a comprehensive water quality monitoring programme that includes emerging contaminants of concern and a strict operating philosophy. The water quality test results are in turn reviewed by experts from local universities as well as overseas experts of international standing. Over the years of operations, NEWater has been found to be well within WHO Drinking Water Guidelines and USEPA Drinking Water Standards and each safety barrier has a significant role to play in ensuring the safety of NEWater for IPU.