Water Quality Limits Research Articles

Seasonal hydrochemical dynamics of surface water in the Limbang River, Northern Borneo—evaluating for spatial and temporal trends

Limbang River Basin (LRB), an equatorial tropical river basin which witnesses the effect of climate change and terrain modification, is hydro-statistically characterized in the present research. In order to characterize the seasonal dynamics of hydrochemical characteristics of surface water, a total of 72 surface water samples were collected from 24 locations in the Limbang River and its tributaries for three different sampling periods (November 2016 (S1), March 2017 (S2), and September 2017 (S3)). Physical parameters (pH, electrical conductivity (EC), total dissolved solids (TDS), dissolved oxygen (DO), turbidity), nutrients (sulfate, nitrate, ammonia, phosphate), major ions (Ca, Mg, Na, K, Cl, HCO3), and trace metals (Co, Ni, Cd, Fe, Mn, Pb, Zn, Cu) were analyzed using standard procedures and the results were statistically processed through Pearson correlation and factor analysis. Gibbs diagram, Piper plot, partial pressure of carbon dioxide, and saturation index of carbonate minerals were also employed to determine the geochemical characteristics and dominant processes operating in the river basin. Higher mean EC value of 129.28 μS/cm in S3 and higher mean pH (6.77) in S1 were observed. The results show spatial and temporal variations in analyzed parameters but are within tolerable limits of the Malaysian water quality and WHO standards. A decreasing order of HCO3- > Cl- > Na+ > Mg2+ > Ca2+ > K+ was noted in the mean concentration of major ions, whereas the mean concentration of trace metals follows the order of Fe > Ni > Pb > Mn > Zn > Co > Cu > Cd. Higher mean concentration of HCO3 (47.09 mg/L) in S2 and higher mean concentration of Fe (1.77 mg/L) in S1 were observed. The Pearson correlation test (r ≥ ± 0.70) shows varying relationships among the parameters and is different in three sampling periods. Piper diagram revealed two distinct chemical facies such as mixed Ca2+-Mg2+-Cl- and Ca2+-Mg2+-HCO3- irrespective of seasons. At the same time, Gibbs plots indicated dominant control of precipitation (rainfall) with an influence of mineral dissolution over the surface water chemistry. An increasing trend of log pCO2 values from upstream to downstream shows the direct recharge of rainwater with lower log pCO2 values in the upstream side and mixed water with higher log pCO2 in the downstream side. The saturation index indicates the under-saturated state of the carbonate minerals in the order of SIMagnesite > SICalcite > SIAragonite > SIDolomite and suggesting the effect of dilution through monsoon rainfall. Factor analysis revealed the dominance of high sediment load in response to severe rainfall, weathering, leaching and dissolution of bed rocks, hydrolysis of organic nitrogen through decomposition of microorganisms, and the aerobic decomposition of organic nitrogenous matter and atmospheric fallout as the major contributors of surface water geochemistry.

Water quality of the volcanic crater lake, Lake Barombi Kotto, in Cameroon

Cameroon is endowed with many freshwater lakes and rivers but, because of increasing anthropogenic activities, most of these water bodies are gradually being degraded. Lake Barombi Kotto is one of the volcanic crater lakes in Cameroon that serves as a prime source of drinking water for the Barombi Kotto community. The overall objective of the study was to determine the water quality of Lake Barombi Kotto making use of some physico-chemical parameters, Carlson’s Trophic State Index (TSI), Heavy Metal Pollution index (HPI) and some bacteriological parameters. Water samples were collected over two seasons across a longitudinal transect at two depths and subjected to physico-chemical, bacteriological, nutrient, Chlorophyll a and phytoplankton analyses using standard methods. Descriptions, Analyses of Variance, ordinations and correlations were used to analyse resulting data at α = 0.05. Lake Barombi Kotto had a TSI of 93.67 and 87.92 in the dry and rainy season, respectively, indicating it is eutrophic. Of the six heavy metals studied, only the concentration of Fe was above the WHO (2008) drinking water quality limits. The HPI of the lake was 4.17 and 6.19 for the dry and rainy seasons, respectively, well below the critical index limit of 100. This lake is contaminated with faecal coliforms and pathogenic bacteria, such as Salmonella. This study has not only set baseline conditions for additional monitoring, but has exposed key dynamics and significant socio-economic and public health risks to humans.

Hydrochemical Evaluation of Surface and Groundwater in Khan Al-Baghdadi Area, Al- Anbar Province / West of Iraq

The hydrochemical study of the surface and groundwater in Khan AL-Baghdadi area included interpretation of physical, chemical and biological properties of 14 wells and 6 surface water samples collected from Euphrates River.. The study covered two periods representing dry and wet periods in October 2018 and April 2019, respectively. The surface water samples were characterized as slightly alkaline, fresh water, excessively mineralized, calcium-chloride type, and hard to very hard class. While the groundwater samples were characterized as slightly alkaline, brackish water, excessively mineralized, calcium-chloride and sodium-chloride type, and hard to very hard class. The assessment of water for irrigation purposes for both water sources in the dry period showed a Sodium Adsorption Ratio (SAR) of no harmful effects, while the Soluble Sodium Percentage (Na%) demonstrated a good irrigation Water Class, except for one well with a permissible irrigation Water Class. While in the wet period, all surface and groundwater samples were of a good irrigation Water Class, except for two wells with permissible irrigation Water Class. In terms of total dissolved solids (TDS) and electrical conductivity (EC), all surface water samples for the two periods were within the permissible limits of irrigation water quality, whereas groundwater samples for the two periods showed unsuitable limits, except for three wells within the permissible limits of irrigation water quality. The microbiological tests showed that all samples of surface and groundwater are classified as clean.

Periphyton removal flows determined by sediment entrainment thresholds

Periphyton (benthic algae) forms the base of the lotic food web but, under particular conditions, can grow to nuisance levels. River managers need to understand under what conditions the rivers might develop nuisance periphyton biomass in order to set water quality and quantity limits and support healthy ecosystems. Factors that promote periphyton growth (e.g., light, temperature, nutrients) and the frequency of flows that remove periphyton (the periphyton removal flow) have long been recognized as primary controls on periphyton abundance. Predicting differences in periphyton removal flows (PRFs) between rivers has remained a challenge. The main objective of this study is to investigate how bed sediment mobility affects periphyton removal and whether it can be used to better predict PRFs at unmonitored sites with acceptable levels of certainty.We calculated the sediment based PRFs at 113 periphyton monitoring sites in rivers of different sizes and different environmental conditions by finding, for a range of particle sizes, the entrainment flow that produced the strongest correlation between periphyton biomass (measured by Chlorophyll a, chl a) and days since the last exceedance of that flow. We then grouped the monitoring sites based on the size of sediment mobile at the PRF and identified a suite of environmental variables that best distinguished these groups using a discriminatory function analysis. We then predicted PRFs at unvisited sites using the same river groupings and associated sediment-based flow metrics. Sediment-based PRFs were able to be identified at 93 of the 113 monitoring sites. Across these sites, the variance in chl a explained by the sediment-based PRF (R2) ranged from 0.37 to 0.88 and averaged 0.58. 94% of these rivers with periphyton data were successfully discriminated into three periphyton removal flow groups, together with a non-identified group, by including 33 out of 44 tested environmental variables (e.g., temperature, nutrient concentrations, rainfall, width). The groups were then used to predict sediment-based periphyton removal flows for unvisited sites across a broad range of conditions. The value of our analysis lies in the ability to predict a range of sediment-based periphyton removal flows using only channel slope, substrate composition and wetted width. While acknowledging that sediment mobility is only one of several mechanistic controls on periphyton, this finding nonetheless offers a simple means to identify the range of sediment-based periphyton removal flows in a river reach, which can help inform river managers about the potential effects of changes in river flows on periphyton chl a.

ASSESSMENT OF MALIR RIVER WATER QUALITY AND IT SUITABILITY FOR IRRIGATION PURPOSES

Malir river, which is passing through industrial area of mega city Karachi is assessed for the suitability of its water for irrigation purposes. It was found that the concentration of studied metals is a function of position and season. Most of the pollutants are within the limits provided by national and international standards however, nickel was above the allowable limit for irrigation water quality (1000 μg/L) which is probably attributed to the discharge of effluent from vegetable-ghee manufacturing factories working in the vicinity. The overall suitability of Malir river based on EC, TDS and SAR is ranked’Permissible’ for irrigation.

Assessment of irrigation water quality (Ground water) of Melur block, Madurai district, Tamil Nadu

The irrigation water quality is gaining importance day by day due to the changes in the urbanisation and industrialisation which over utilise the under ground water. The ground water samples were collected from 15 revenue villages of Melur block, Madurai, Tamil Nadu during March, 2017 at variegated intervals, processed and analysed for the physico-chemical, anionic and cationic parameters to find out their quality by arriving calculated parameters viz., RSC (Residual Sodium Carbonate) and SAR (Sodium Absorption Ratio). Though the overall values lies well within the safe limit of water quality, the 25 percent water samples found to be alkaline, 42 percent found to slightly saline & two percent found to be critical in salinity levels. The highest value of 9.23, 2.62 dSm-1, 3.52 and 8.51 of pH, EC, RSC and SAR were observed in the irrigation water samples. The good quality of 92.8 per cent, marginally saline 2.9 per cent and marginally alkali of 4.3 per cent of irrigation water samples have been recorded as per AICRP, 1989 classification.

Trace metal leaching from quarry by-product-stabilized marine sediments

Millions of cubic meter of sediments are dredged annually to open channels for navigation of ships in ports and harbors. Beneficial reuse of these dredgings is typically possible upon their stabilization with calcium-rich amendments. A series of long-term laboratory column leaching tests and contaminant transport models were employed to study metal leaching behavior of bottom-sea dredged material (DM) and their blends with quarry by-products in the natural environment. Column leach tests yielded generally low or non-detectable metal concentrations. The results of the transport modeling indicated that the analyzed metals leached from the DM and the blends were below the national water quality limits at the point of entry to surface water or upon reaching groundwater. Model results showed a significant reduction in leached porewater concentrations due to adsorption and natural attenuation onto a simulated natural formation located between the DM or treated DM and the body of surface water. The overall findings showed that dredged sediments can be considered for reuse following amendment with quarry by-products.

Batch leaching testing of stabilized dredged bottom-sea sediments

This study aims to define the long-term leaching of metals from structural fills composed of quarry byproduct-amended marine-dredged material under the influence of pH and to study the geochemical behavior of the species likely to form. Compaction and shear tests, image analysis, and pHstat and toxicity characteristic leaching procedure tests were undertaken to study the metal leaching behavior of raw dredged sediments and their blends prepared with three different quarry fines. Geochemical analysis was conducted to determine the predominant oxidation states from the analyzed metals, the aqueous concentrations of metal species, and the dominant leaching control mechanisms in the leachates. The quarry fine-amended dredged sediments satisfied the local compaction specifications for highway embankment construction while the raw sediments did not. The effective friction angle of the blends was also higher than that of raw sediments due to differences in soil structure and shape parameters. Leaching of As during the pHstat leaching tests followed an amphoteric pattern for raw sediments and a cationic pattern for the blends. Al, Cu, Fe, Ni, and Zn concentrations leached from the blends were below the EPA water quality limits at near-neutral pH. The concentrations of all metals released during the batch leach tests from the treated dredged materials are below the water quality limits under varying pH conditions. Geochemical modeling results indicated that release of all elements except arsenic from the treated dredged sediments was controlled by the dissolution and precipitation of oxide, hydroxide, and carbonate solids containing the elements.

A close examination of the role and needed expertise of brokers in bridging and building science policy boundaries in environmental decision making

Knowledge brokers are often portrayed as neutral intermediaries that act as a necessary conduit between the spheres of science and policy. Conceived largely as a task in packaging, brokers are expected to link knowledge producers and users and objectively translate science into policy-useable knowledge. The research presented in this paper shows how brokering can be far more active and precarious. We present findings from semi-structured interviews with practitioners working with community-based groups involved in collaborative water planning in New Zealand’s South Island region of Canterbury. Working in a highly conflicted situation, our brokers had to navigate different knowledges and epistemic practices, highly divergent values and grapple with uncertainties to deliver recommendations for regional authorities to set water quality and quantity limits. Conceiving science and policy as interlinked, mutually constitutive and co-produced at multiple levels, rather than as separate domains, shows how the brokers of this study were not only bridging or blurring science policy boundaries to integrate and translate knowledges. They were also building boundaries between science and policy to foster credibility and legitimacy for themselves as scientists and the knowledge they were brokering. This research identifies further under-explored aspects of brokering expertise, namely, the multiple dimensions of brokering, transdisciplinary skills and expertise, ‘absorptive’ uncertainty management and knowledge translation practices.

Geoenvironmental behavior of lime-treated marine sediments

Several hundred million cubic meters of sediment are dredged from various U.S. ports, harbors, and waterways annually to maintain and improve the nation’s navigation system for commercial, national defense, and recreational purposes. The United States Environmental Protection Agency mandated containment of dredged sediments in designated containment facilities. The current study aims to explore the use of sediments dredged from Baltimore Harbor as a potential highway embankment material. Lime-based additives have been added to the dredged material and geotechnical analysis is coupled with environmental assessment in this study. Long-term sequential column leaching test results showed that aluminum, arsenic, nickel, cobalt, and zinc leached from the dredged sediments, but the metal concentrations quickly decreased to EPA water quality limits for protection of aquatic life and human health in freshwaters. Addition of lime kiln dust and quick lime lowered the amount of metals leaching from the material. Contaminant concentrations originating from the dredged sediment in an embankment are reduced up to 80 times in surface waters and decreased to negligible levels upon reaching groundwater.

Development of ambient marine standards using long-term data: An example from Abu Dhabi

Abu Dhabi, the capital of the United Arab Emirates, has a coastline that occupies 76% of the country’s Arabian Gulf coastline. The pressures accompanying the economic development that the country is undergoing ultimately affected the marine ecosystem including water and sediment quality. In order to protect the marine ecosystem and public health, the Environment Agency- Abu Dhabi developed ambient marine water and sediment quality standards using the long-term data collected along the coast of Abu Dhabi. Along with the data collected on 39 marine water quality and sediment parameters (hydrography, nutrients, and heavy metals), a review of best practices from jurisdictions whose approach was scientifically based and whose physical conditions were as similar as possible to those found in Abu Dhabi were used for the establishment of marine water and sediment quality limits. These promulgated ambient limits were then used to develop the marine water and sediment regulation that establish two uses of marine waters (protected and general) and an anti-degradation policy. In addition, the ambient water and sediment limits provide a bench mark to both assess trends that may indicate stress to marine flora and fauna and support the work of environmental permitting and enforcement.

No-regret selection of effective control handles for integrated urban wastewater systems management under parameter and input uncertainty.

Regulatory water quality limits are extended from the wastewater resource recovery facility (WRRF) to the sewer system. It is thus necessary to properly integrate those systems for the evaluation of the overall emissions to the receiving water. The integration of the sewer system and the WRRF, however, leaves us with multiple potential options to reduce these emissions. The proposed approach builds on previous research using global sensitivity analysis (GSA) as a screening method for available control handles. It considers parameter and input uncertainty to select control handles that generate large benefits even if the model differs from reality. Results from a real-life case study indicate that the three top-rated handles are comparably effective for all considered uncertainty and variability scenarios. But the results also showed that this does not apply to lower-rated handles.

Geochemical and health risk evaluation of fluoride rich groundwater in Sattenapalle Region, Guntur district, Andhra Pradesh, India

To assess the geochemical mechanisms of fluoride occurrence in the groundwater and its impact on human health, groundwater samples collected from the Sattenapalle Region, Guntur district, Andhra Pradesh, India were analyzed for various chemical parameters. Results show that the groundwater quality is of alkaline in nature, which is mainly characterized by Na-HCO3 facies. According to the groundwater quality index, 75% and 25% of the groundwater sampling points come under the poor and very poor groundwater quality categories for drinking purpose, respectively. The fluoride content varies from 1.3 to 12.9 mg/L, with 75% of the groundwater sampling points exceeding the drinking water quality limit of 1.5 mg/L. The study on Ca2++Mg2+ vs. HCO+SO Na++K+ vs. TC, Na+ vs. Cl HCO vs. TC, trilinear diagrams and CA indices specifies the soil-water-rock interactions together with dissolution, ion exchange and evaporation as the dominant controlling processes that affect the groundwater chemistry. The non-carcinogenic risk is from 0.83 to 9.77, exceeding its acceptable limit of one in 75%, 90% and 100% of the groundwater samples with respect to men, women and children, respectively, depending upon their body weights. Remedial measures are suggested to reduce the health risk in the study region.

Radiological health risk assessment of drinking water and soil dust from Gauteng and North West Provinces, in South Africa

Long-lived natural radionuclides such as (238U) uranium-238, (232Th) thorium-232, (226Ra) radium-226 and (40K) potassium-40 and heavy metals are normally exposed to the surface during mining activities. They enter the human body when inhaled (as dust) or ingested (by drinking contaminated water). An intake of large concentrations of these radionuclides and heavy metals can lead to health effects such as development of cancers. The aim of this work was to assess the radiological health risk due to intake of radionuclides in dust and drinking water from the West Rand gold mining area and Modiri Molema Municipality (MMM) water treatment plant. The dust samples were analyzed for radionuclides of interest using the well-type high purity Germanium detector. Water samples were collected before and after purification from the Modiri Molema Municipality water treatment plant and analyzed using the ultra-low level Liquid Scintillation Counter (LSC), to evaluate the gross alpha and beta radioactivity dose levels of the radionuclides in water. An Inductively Coupled Plasma Mass Spectrometry (ICP-MS) was used to evaluate the heavy metal concentrations in the drinking water after purification at the treatment plant. The total inhalation effective dose obtained in this study was (2.71 × 10−1 and 1.31 × 10−1) μSv.y−1 for adults and infants respectively, which is below the prescribed dose range of 5–10 μSv.y−1. The mean activity concentrations of the radionuclides in air dust were found to be; 226Ra, (2.14 ± 0.82) × 10−6 (Bq.m−3), 238U (6.08 ± 2.17) × 10−7 (Bq.m−3) and 232Th (2.65 ± 1.1) × 10−7 (Bq.m−3). The activity concentration of 226Ra obtained exceeded the world average by 2 times. The Raeq, the external hazard (Hex) and internal hazard (Hin) indices were calculated and the values obtained from soil were lower than the world average. However, the absorbed dose rate in air was higher than the world averages of 60 nGyh-1. The minimum and maximum gross alpha activity obtained was 0.0041 (Bq.L−1) and 0.0053 (Bq.L−1) respectively, while the minimum and maximum gross beta activity obtained for water samples was 0.0083 (Bq.L−1) and 0.0105 (Bq.L−1) respectively. More heavy metals were detected in the first two stages of the water treatment than on the last two stages, nevertheless, their concentrations did not exceed recommended limits. The results for soil dust indicates that the windward areas might pose health risks for human population staying in the area and the activity concentration for drinking water indicate that the specific activity in the water supply after purification is below the WHO guideline limit of 0.5 (Bq.L−1) for gross alpha and 1 (Bq.L−1) for gross beta. The results obtained were also within the range of the South Africa Department of Water Affairs and Forestry target water quality limit of (0–1.38) (Bq.L−1) for gross beta activity. Heavy metals concentrations in drinking water did not exceed the stipulated limits by USEPA and DWAF. Therefore, this water after treatment is radiologically and toxicologically safe for the members of the public.

Assessment of Heavy Metal Contamination in Waters due to Mineral Salts Company from Mighan playa/lake, Arak, Iran

The Mighan playa/lake is characterized as a closed catchment. In the recent years, the rapid industrialization and urbanization has resulted in a pollution area in the city of Arak. In this work, we focus on six regions around the playa/lake to study the distribution of heavy metals in the waters and their contamination risk. A total of 32 water samples are analyzed to determine the contamination degree of heavy metals, i.e. Hg, As, Cd, Cr, Cu, Pb, and Zn. The heavy metal pollution index, heavy metal evaluation index, and degree of contamination are utilized to assess the pollution extent of these metals. The spatial distribution patterns reveal that the waters in different areas of playa/lake are in a good condition. The island, lake in playa, and the Wastewater Mineral Salts Company are most seriously polluted with Pb, being higher than the standard of drinking water quality limit. Water in the wastewater treatment plant is polluted with Hg and As. The correlation matrix, factor analysis, and cluster analysis are used to support the idea that Pb may be mainly derived from the atmospheric input, and As and Hg from the wastewater treatment plant, agricultural lands, and domestic waste. Many native and migratory birds live in the Mighan playa, which is exposed to heavy metals. Therefore, it is required to monitor heavy metals in the Arak playa and to manage the municipal, industrial, and agricultural activities around it and to reduce them.

On the Treatment Trains for Municipal Wastewater Reuse for Irrigation

Traditional urban wastewater treatment plants (UWTPs) are badly efficient in eliminating most contaminants of emerging concern (CECs), comprising antibiotics, antibiotic-resistant bacteria and antibiotic resistance genes (ARB & ARGs). Such pollutants induce some worry for nature and human health, especially if UWTPs effluents are reused for crop irrigation. In all probability, traditional UWTPs will need extra advanced treatment stages to satisfy water quality limits for wastewater reuse. Recently, Rizzo and his co-workers [1] published an excellent review that aims to suggest potential advanced treatment solutions, especially concerning the elimination of CECs and ARB & ARGs. They deeply assessed the performance of the best available technologies (BATs) for domestic wastewater treatment to decrease CECs and ARB & ARGs. Especially, they evaluated ozonation, activated carbon adsorption, chemical disinfection, UV radiation, advanced oxidation processes (AOPs) and membrane filtration focusing on their capacity to efficiently eliminate CECs and ARB & ARGs, as well as their benefits and disadvantages. This work focuses on likely treatment trains involving the aforesaid BATs. As concluded by Rizzo et al. [1] a one advanced treatment technique is not enough to reduce the liberation of chemical CECs and ARB & ARGs and make wastewater reuse for crop irrigation safer; however, an impertinent integration of them and an appropriate controlling program would be needed. There is no miraculous BAT for treating wastewater for water reuse in agriculture. An appropriate combination of many techniques would be suggested following each case.

A Heuristic Method for Determining Changes of Source Loads to Comply with Water Quality Limits in Catchments.

A common land and water management task is to determine where and by how much source loadings need to change to meet water quality limits in receiving environments. This paper addresses the problem of quantifying changes in loading when limits are specified in many locations in a large and spatially heterogeneous catchment, accounting for cumulative downstream impacts. Current approaches to this problem tend to use either scenario analysis or optimization, which suffer from difficulties of generating scenarios that meet the limits, or high complexity of optimization approaches. In contrast, we present a novel method in which simple catchment models, load limits, upstream/downstream spatial relationships and spatial allocation rules are combined to arrive at source load changes. The process iteratively establishes the critical location (river segment or lake) where the limits are most constraining, and then adjusts sources upstream of the critical location to meet the limit at that location. The method is demonstrated with application to New Zealand (268,000 km2) for nutrients and the microbial indicator E. coli, which was conducted to support policy development regarding water quality limits. The model provided useful insights, such as a source load excess (the need for source load reduction) even after mitigation measures are introduced in order to comply with E. coli limits. On the other hand, there was headroom (ability to increase source loading) for nutrients. The method enables assessment of the necessary source load reductions to achieve water quality limits over broad areas such as large catchments or whole regions.

Isolation distance between municipal solid waste landfills and drinking water wells for bacteria attenuation and safe drinking

Groundwater pollution and human health risks caused by leachate leakage have become a worldwide environmental problem, and the harm and influence of bacteria in leachate have received increased attention. Setting the isolation distance between landfill sites and groundwater isolation targets is particularly important. Firstly, the intensity model of pollutant leakage source and solute transport model were established for the isolation of pathogenic Escherichia coli. Then, the migration, removal and reduction of bacteria in the aerated zone and ground were simulated. Finally, the isolation distance was calculated based on the acceptable water quality limits, and the influence of hydrogeological arameters was analyzed based on the parameter uncertainty. The results of this study suggest that the isolation distances vary widely ranging from 106 m–5.46 km in sand aquifers, 292 m–13.5 km in gravel aquifers and 2.4–58.7 km in coarse gravel aquifers. The gradient change of groundwater from 0.001 to 0.05 resulted in the isolation distance at the highest gradient position being 2–30 times greater than that at the lowest gradient position. There was a difference in the influence of the thickness of the vadose zone. For example, under the same conditions, with the increase of the thickness of the aeration zone, the isolation distance will be reduced by 1.5–5 times, or under the same thickness of the aeration zone, the isolation distance will be significantly shortened. Accordingly, this needs to be determined based on specific safety isolation requirements. In conclusion, this research has important guiding significance for the environmental safety assessment technology of municipal solid waste landfill.

Hydraulic and environmental impacts of using recycled asphalt pavement on highway shoulders

An experimental program was carried out to evaluate hydraulic and environmental behavior of recycled asphalt pavement (RAP) obtained from seven different roadways within the state of Maryland for their potential utilization in construction of highway shoulder edge drop-offs. Due to their common use in these edge drop-offs, graded aggregate base material, gravel, and topsoil were included as control materials in the testing program. Hydraulic conductivities of RAPs were evaluated through a series of constant-head tests, while their leaching potential was determined through batch and column leach tests. Laboratory test results indicated that the hydraulic conductivity of recycled asphalt pavement was comparable to that of natural aggregates with the gradation of a clean sand-gravel mixture. The stabilized concentrations of all metals released from the RAPs during the column leach tests were below the water quality limits. The numerical analysis results revealed that, with increasing distance from highway shoulder, the metal concentrations in nearby surface waters decreased further.

Rice Production with Restricted Water Usage: A Global Perspective

GLOBAL rice production remains critically import for food security; however, fresh water is an ever-increasingly diminished resource. The objective of this manuscript is to select central and comprehensive research focusing on rice production and diminished water availability to isolate and authenticate emerging initiatives to address continuance of rice production and to ensure water sustainability. Three regions were selected: (i) Asia with an emphasis of China and India, (ii) The United States of America and (iii) The Mediterranean region with an emphasis on Egypt. Each of these regions recognize current or emerging issues associated with water quantity, water quality, urbanization, climate change and other technological, social and policy constraints; however, each region has a different hierarchy of issue importance. China and India recognize climate change, aquifer overdraft and pollution of water resources as central issues, whereas the mid-South region of the United States of America is more focused on irrigation technology to improve farm profitability. Egypt is primarily focused on water quantity and quality limitations, with substantial research addressing desertification and saline soils/water. This review focuses on stated research objectives in compelling, peer-reviewed literature to indicate regional approaches addressing the causes of restricted water availability for rice production and the most-probable approaches for maintaining rice production to safe-guard food security and producer profitability. Thus, unique rice water management approaches are predicated on the region’s water quantity and quality environmental assessment.