Municipal Wastewater Discharges Research Articles

At the Intersection of Urbanization, Water, and Food Security: Determination of Select Contaminants of Emerging Concern in Mussels and Oysters from Hong Kong.

Aquaculture, which is growing 3-5 times faster than terrestrial agriculture, will play an important role to meet future global food production needs. However, over 80% of global sewage production is returned to the environment untreated or poorly treated. In developing nations, these nontraditional waters of diverse quality are being recycled for aquaculture, yet chemical residues are differentially studied. Here, we examined pharmaceuticals, pesticides, polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), polycyclic aromatic hydrocarbons (PAHs), and flame retardants in marine bivalves using isotope dilution liquid chromatography-tandem mass spectrometry (LC-MS/MS) and low-pressure gas chromatography-tandem mass spectrometry (LP GC-MS/MS). Green-lipped mussels from the field and oysters from aquaculture net pens, which are harvested as food products, were collected adjacent to point source municipal wastewater and landfill leachate effluent discharges, respectively, in Hong Kong, the fourth most densely populated country in the world. Multiple classes of pharmaceutical, pesticides, PAHs, and phosphorus-based flame retardants were detected at low μg/kg levels. Acceptable servings per week indicated minimal risk for a number of chemicals; however, such calculations could not be performed for other contaminants of emerging concern. Future efforts are needed to better understand contaminant influences on marine bivalve populations and aquaculture product safety, particularly in rapidly urbanizing regions of developing countries with limited wastewater infrastructure.

Validation of the Three-Step Strategic Approach for Improving Urban Water Management and Water Resource Quality Improvement

The impact on water resources caused by municipal wastewater discharges has become a critical and ever-growing environmental and public health concern. So far, interventions have been positioned largely ‘at the end of the pipe’, via the introduction of high-tech and innovative wastewater treatment technologies. This approach is incomplete, inefficient and expensive, and will not be able to address the rapidly growing global wastewater challenge. In order to be able to efficiently address this problem, it is important to adopt an integrated approach such as the three-step strategic approach (3-SSA) consisting of (1) minimization and prevention, (2) treatment for reuse and (3) stimulated natural self-purification. In this study, the 3-SSA was validated by applying it to the Upper Cauca river basin, in Colombia and comparing it to a conventional strategy. The pollutant load removed was 64,805 kg/d Biochemical Oxygen Demand BOD5 (46%) for the conventional strategy and 69,402 kg/d BOD5 (50%) for the unconventional strategy. Cost benefit analysis results clearly favoured the 3-SSA (unconventional strategy): NPV for the conventional strategy = −276,318 × 103 Euros, and NPV for the unconventional strategy (3-SSA) = +338,266 × 103 Euros. The application of the 3-SSA resulted in avoided costs for initial investments and operation and maintenance (O&M), especially for groundwater wells and associated pumps for sugar cane irrigation. Furthermore, costs were avoided by optimization of wastewater treatment plants (WWTPs), tariffs and by replacement of fertilizers.

Environmentally relevant concentrations of glibenclamide induce oxidative stress in common carp (Cyprinus carpio)

The hypoglycemic pharmaceutical glibenclamide (GLB) is widely used around the world. This medication is released into the environment by municipal, hospital and industrial wastewater discharges. Although there are reports of its environmental occurrence in the scientific literature, toxicity studies on aquatic species of commercial interest such as the common carp Cyprinus carpio are scarce. The present study aimed to evaluate the oxidative stress induced on C. carpio by environmentally relevant concentrations of GLB. Biomarkers of oxidative damage such as hydroperoxide content, lipid peroxidation and protein carbonyl content were evaluated as well as the activity of the antioxidant enzymes superoxide dismutase and catalase. The concentration of GLB was determined in water as well as in gill, liver, muscle, brain and blood of carp at 12, 24, 48, 72 and 96 h. The findings obtained in the study prove that GLB induces increases in biomarkers of oxidative damage and antioxidant enzyme activity in the teleost C. carpio, that this response is not concentration dependent and that the organs evaluated bioconcentrate this hypoglycemic agent. These findings permit us to conclude that the presence of GLB in water bodies represents a risk for aquatic species.

Nitrate removal from water by ion exchange

High concentrations of nitrate in water, both in surface and in groundwater, is a consequence of geological composition of soil or human activity. Increased concentrations of nitrate in drinking water is a serious hazard to human health, causing abnormalities such as cancerous growth in human digestion system, while excessive nitrate intake via drinking water can cause methemoglobinemia in infants. Furthermore, the presence of nitrate in aquifers can stimulate eutrophication, which compromise the growth of algae and depletion of dissolved oxygen. Natural and chemical fertilizers in crop production, detergent manufacturing, uncontrolled land discharge of municipal wastewater, and industrial wastes have been identified as the main sources of nitrate in water sources. Nitrate is a stable, highly soluble ion that is difficult to remove by conventional water treatment methods such as coagulation and flocculation. The ion exchange is the most widely used procedure for removing nitrate from water. In this research the possibility of removing nitrate from water was examined by using commercial ion exchangers: Duolite A7 and Relite A490, respectively. The influence of the initial concentration of nitrate (10, 50 and 100 mg/l), the contact time (15 - 1440 min) and the mass of the ion exchanger (0.1 to 0.6 g) was also examined.

Structure and Composition of Mangrove Associations in Tubli Bay of Bahrain as Affected by Municipal Wastewater Discharge and Anthropogenic Sedimentation

The effects of municipal wastewater discharge and anthropogenic sedimentation on the structure and composition of gray mangrove (Avicennia marina (Forsk.) Vierh.) communities along Tubli Bay coastlines in Bahrain were investigated. Growth and regeneration of mangrove were measured, and its community was characterized. Sediment profile was analyzed for texture, pH, and salinity. Mangrove area covered by sand depositions was measured using Google Earth Pro. ANOVA and regression tests were employed in the analysis of the data. Results indicated that mangrove overwhelmingly dominated plant community in the study area, which was zoned by a community of other salt-tolerant species. Three main habitats exist in the study area with high similarity in their floristic composition. Species richness and the number of habitats were low due to the aridity and high sediment salinity. The dilution effect of the secondary treated wastewater had a favorable effect on height and diameters of mangrove trees. However, no differences were observed in leaf area index, basal area, and density of mangrove. The long-term accumulation of anthropogenic sedimentation had a detrimental effect on the mangrove community, expressed in swath death of mangrove trees due to root burials and formation of high topography within the community boundaries.

Pharmaceuticals and Personal Care Products in Municipal Wastewater and the Marine Receiving Environment Near Victoria Canada

Concerns over the fate of pharmaceuticals and personal care products (PPCP) within the environment have been growing with the advent of more precise analytical methods. The discharge of municipal wastewater has been identified as a significant source of these contaminants, particularly where wastewater treatment is minimal. Here we present results from a comprehensive monitoring regime located around Victoria, BC, Canada. Samples were collected between 2009 and 2016 from a variety of sources including marine water, sediment and biota adjacent to two major untreated sewage outfalls, as well as the sewage itself. PPCP concentrations within the untreated sewage were high, and the sediment surrounding the outfalls showed corresponding contamination. However, this contamination dropped quickly with distance from the outfall such that by 800 m distance most PPCPs were below detection limits. Tissue samples of resident Northern Horse mussels (Modiolus modiolus) collected adjacent to one of the major sewage outfalls showed high single sample concentrations of the antimicrobial triclosan (317 ng g-1 dry weight), the antibiotic ciprofloxacin (176 ng g-1 dry weight), as well as the antidepressant sertraline (84.1 ng g-1 dry weight). Reference stations from around the region showed very low concentrations of contamination with almost all PPCP concentrations being below detection limits. Within the sewage, concentrations were largely stable overtime, with the exception of triclosan and triclocarban which both showed declines over the study period.

Intuitionistic fuzzy analytical hierarchical processes for selecting the paradigms of mangroves in municipal wastewater treatment

Municipal wastewater discharge is widespread and one of the sources of coastal eutrophication, and is especially uncontrolled in developing and undeveloped coastal regions. Mangrove forests are natural filters of pollutants in wastewater. There are three paradigms of mangroves for municipal wastewater treatment and the selection of the optimal one is a multi-criteria decision-making problem. Combining intuitionistic fuzzy theory, the Fuzzy Delphi Method and the fuzzy analytical hierarchical process (AHP), this study develops an intuitionistic fuzzy AHP (IFAHP) method. For the Fuzzy Delphi Method, the judgments of experts and representatives on criterion weights are made by linguistic variables and quantified by intuitionistic fuzzy theory, which is also used to weight the importance of experts and representatives. This process generates the entropy weights of criteria, which are combined with indices values and weights to rank the alternatives by the fuzzy AHP method. The IFAHP method was used to select the optimal paradigm of mangroves for treating municipal wastewater. The entropy weights were entrained by the valid evaluation of 64 experts and representatives via online survey. Natural mangroves were found to be the optimal paradigm for municipal wastewater treatment. By assigning different weights to the criteria, sensitivity analysis shows that natural mangroves remain to be the optimal paradigm under most scenarios. This study stresses the importance of mangroves for wastewater treatment. Decision-makers need to contemplate mangrove reforestation projects, especially where mangroves are highly deforested but wastewater discharge is uncontrolled. The IFAHP method is expected to be applied in other multi-criteria decision-making cases.

Evidence of anaerobic coupling reactions between reduced intermediates of 4-nitroanisole

Nitroaromatic compounds are widely used in agricultural pesticides, pharmaceuticals, military explosives, and other applications. They enter the environment via manufacturing and municipal wastewater discharges and releases from agricultural and military operations. Because of their ubiquity and toxicity, they are considered an important class of environmental contaminants. Nitroaromatics are known to undergo reductive transformation to aromatic amines, and under aerobic conditions they are susceptible to coupling reactions which may lead to their irreversible incorporation into soil organic matter. However, there is also evidence of coupling reactions in the absence of oxygen between reduced intermediates of the insensitive munitions compound 2,4-dinitroanisole, leading to the formation of azo dimers. The formation of such products is a concern since they may be more toxic than the original nitroaromatic compounds. The objective of this research is to provide evidence of the anaerobic formation of azo coupling products. 4-Nitroanisole was used as a model compound and was spiked into incubations containing anaerobic granular sludge with H2 as the electron donor. Using liquid chromatography, UV–Vis spectroscopy, and mass spectrometry, the formation of the azo dimer 4,4′-dimethoxyazobenzene was confirmed. However, due to the instability of the azo bond under the reducing conditions of our incubations, the azo dimer did not accumulate. Consequently, 4-aminoanisole was the major product formed in our experiment. Other minor suspected coupling products were also detected in our incubations. The results provide clear evidence for the temporal formation of at least one azo dimer in the anaerobic reduction of a model nitroaromatic compound.

Oil contamination in surface sediment of Anzali Wetland in Iran is primarily even carbon number n-alkanes.

To determine the extent of oil contamination and biodegradation in Anzali Wetland of Iran, we examined aliphatic hydrocarbons in surface sediment of this area (n=20). Petroleum hydrocarbon levels (mean 1585±1117; range 316 to 4358μgg-1 dry weight) were similar in value to reports from other highly contaminated areas, such as New York Bight, Saudi and Kuwaiti coasts of the Persian Gulf, and Dubai shorelines. Even carbon homologs dominated distribution of n-alkanes in surface sediment of Anzali, which is rarely reported elsewhere. Multiple factors used in our study point to petrogenic source for n-alkanes in Anzali Wetland. Anzali receives multiple industrial and agricultural runoffs from the surrounding area. Shipping industry and oil industry are responsible for a major portion of pollutants entering Anzali. Municipal wastewater discharges are another source of Anzali pollution. To determine why even carbon number n-alkanes predominate in Anzali, we examined the following indices: existence of unresolved complex mixtures (UCM), ratio of UCM to resolved alkanes (RA), ratio of low-molecular weight to high-molecular weight molecules, presence of degraded oil residue, high-relative biodegradation, and the degree of hydrocarbon weathering in the surface sediment of the area. Our findings corroborate with such predominance.

Rapid nitrification process upgrade coupled with succession of the microbial community in a full-scale municipal wastewater treatment plant (WWTP)

Bioaugmentation was used to upgrade the nitrification process in a full-scale municipal WWTP with an A2/O system. A mixture of nitrifying bacteria was inoculated into the bioreactor for a final concentration of 1% (v/v). The upgrade process took 25 days, and the NH4+-N removals reached 94.6% (increased at least by 75%). The effluent concentrations of COD and NH4+-N stabilized at <30 mg/L and <4 mg/L even when the corresponding influent concentrations were over 300 mg/L and 60 mg/L, which met the first-class requirement of the National Municipal Wastewater Discharge Standards of China (COD ≤ 50 mg/L, NH4+-N ≤ 5 mg/L). The succession of the microbial community showed the enhanced NH4+-N removal efficiency mainly resulted from the persistence of introduced ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB), which increased from 0% to 0.4% and from 0.01% to 2.1%, respectively. This bioaugmentation was shown as an effective technology for upgrading or retrofitting conventional systems to tertiary-level.

Testicular oocytes in smallmouth bass in northeastern Minnesota in relation to varying levels of human activity.

Testicular oocytes (TOs) have been found in black bass (Micropterus spp.) from many locations in North America. The presence of TOs is often assumed to imply exposure to estrogenic endocrine disrupting compounds (EDCs); however, a definitive causal relationship has yet to be established, and TO prevalence is not consistently low in fish from areas lacking evident EDC sources. This might indicate any of a number of situations: 1) unknown or unidentified EDCs or EDC sources, 2) induction of TOs by other stressors, or 3) testicular oocytes occurring spontaneously during normal development. In the present study, we analyzed TO occurrence in smallmouth bass (Micropterus dolomieu) from 8 populations in northeastern Minnesota watersheds with differing degrees of human development and, hence, presumed likelihood of exposure to anthropogenic chemicals. Three watersheds were categorized as moderately developed, based on the presence of municipal wastewater discharges and higher human population density (4-81 per km2 ), and 5 watersheds were minimally developed, with very low human population density (0-1 per km2 ) and minimal built environment. Testicular tissues from mature fish were evaluated using a semiquantitative method that estimated TO density, normalized by cross-sectional area. Testicular oocyte prevalence and density among populations from moderately developed watersheds was higher than in populations from minimally developed watersheds. However, TO prevalence was unexpectedly high and variable (7-43%) in some populations from minimally developed watersheds, and only weak evidence was found for a relationship between TO density and watershed development, suggesting alternative or more complex explanations for TO presence in smallmouth bass from this region. Environ Toxicol Chem 2017;36:3424-3435. © 2017 SETAC.

Water chemistry of the southern Tibetan Plateau: an assessment of the Yarlung Tsangpo river basin

The Yarlung Tsangpo is the largest river draining the southern Tibetan Plateau along the Himalayan ranges. In this paper, the ions and elements in the water of the Yarlung Tsangpo were studied. In general, the water of the Yarlung Tsangpo had a fairly high buffering capacity (pH ~8.8) and oxidation environment (ORP ~190 mv). Total dissolved solids averaged approximately 157 mg L−1, which is higher than that of the global mean level. Under the dominant rock weathering due to the abundant carbonates around the river basin, the ionic chemistry of the Yarlung Tsangpo was mainly composed of Ca2+ and HCO3 −. In addition, with a large amount water discharged into the river, groundwater (e.g., numerous chloride-rich hot springs) is another potentially important source of ions that affect the water chemistry in the Yarlung Tsangpo basin. Although watercourses on the Tibetan Plateau can generally be considered pristine, concentrations of some toxic elements (i.e., Cd and Pb) were found to be higher than the WHO guideline for drinking water due to increasing influence from anthropogenic activities (e.g., tourism, mining operations and municipal wastewater discharge), which constitute a risk to human livelihoods in both local and surrounding regions.

Nitrogen Compounds Distribution in Diyala River Opposite Al-Rustimiyah Sewage Treatment Plants

The reach of Diyala River just before its confluence with Tigris River south of the capital city Baghdad was taken as a case-study. This segment of Diyala River is exposed to multiple points of treated and raw municipal wastewater discharges of Al-Rustimiyah wastewater treatment plants. Its pollution status was assessed with regard to nitrogen compounds levels. The aquatic parameters: DO, TN, TKN NH4-N, NH3-N, NO3-N, NO2-N, pH, and temperature were monitored and measured at nine sites along the river reach for a period of one year to assess seasonal variations. The first and last sites were chosen at the downstream and upstream of the points of pollution flowing into Diyala River, while the second to eighth sites were located at the effluents of the WWTPs of Al-Rustimiyah. It was found that water at sites two, seven, and four, respectively, were the most polluted points among all duo to the presence of the bypasses from the WWTPs at these sites. With regard to NH4-N, NH3-N, and TN concentrations, the river was found to be heavily polluted with untreated wastewater at site two and between low to medium strength at other sites, except for site one. On the other hand, NO3-N and NO2-N concentrations categorized the river water as an effluent rather than a stream according to Iraqi standard classification. Reversed relations were found between the DO concentrations and some of the nitrogen compounds and temperature. A statistical model relating TN concentration to DO, NH3-N, and temperature was derived. It was proved to be accurate.

Characterization of size fractionated dissolved organic matter from river water and wastewater effluent using preparative high performance size exclusion chromatography

Structural and functional characterization of dissolved organic matter (DOM) is challenging due to its inherent heterogeneity and coherent complexity. Here, a relatively new method based on preparative high performance size exclusion chromatography using deionized water as mobile phase (recovery rate of total carbon mass>97%) was developed to fractionate DOM depending on molecular size and identify molecular weight (MW)-dependent DOM characteristics presumably associated with its potential for formation of complexes with inorganic species (i.e. metals and metalloids), membrane fouling and disinfection byproducts. Size fractionated DOM from different types of source (river water vs. wastewater effluent) provided similar patterns in water quality, fluorescence properties and biopolymer composition. This suggested that discharge of municipal wastewater had an impact on the river water. However, the propensity for complexation between each size fractionated DOM sample and various inorganic species was substantially different, due to the differences in fluorescence spectral properties and associated biopolymer composition. Among three distinct size fractionated DOM samples, the fraction with medium MW and the main biopolymers polyhydroxy aromatics exhibited a relatively higher potential for metal complexation and the normalized ratio of metals and metalloids to dissolved organic carbon (DOC) [metal/DOC (fraction i, i=I, II, III)] to [metal/DOC (fraction I)] than the other size fractionated DOMs. The results indicate that the biopolymer composition of DOM plays a critical role in its complexation with inorganic species.

Biomarkers of exposure to nanosilver and silver accumulation in yellow perch (Perca flavescens).

There is a risk of exposure of aquatic organisms to silver nanoparticles (AgNPs) from discharges of municipal and industrial wastewater. In the present study, yellow perch (Perca flavescens) were exposed to environmentally relevant concentrations (1 mg/L and 100 mg/L) of AgNPs and silver ions (Ag+ ) in static-renewal experiments conducted over 96 h and 10 d. The greatest accumulation of total Ag occurred in the liver of P. flavescens, and there was >10-fold more accumulation in the treatments with Ag+ relative to the AgNP treatments. Residues of total Ag increased with concentration and duration of exposure in liver, gill, and muscle. Both exposures caused a 2-fold induction of gene expression for metallothionein (mt) in liver tissue after 96 h of exposure and reductions in levels of oxidized glutathione (GSSG) in liver after 10 d of exposure. Both AgNPs and Ag+ decreased the expression of heat-shock proteins (hsp70). Exposure to the high concentration of AgNPs for 10 d significantly increased lipid peroxidation in gill tissue, as indicated by the thiobarbituric acid reactive substances (TBARS) assay. There was a negative correlation between mean levels of GSSG and TBARS for both gill and liver tissue when data for all treatments were combined. It is significant that these biological responses were observed in P. flavescens exposed to AgNPs, even though accumulation of total Ag was at least 10-fold lower relative to the treatments with Ag+ . Environ Toxicol Chem 2017;36:1211-1220. © 2016 SETAC.

Hydrodynamic and water quality modeling of Lake Manzala (Egypt) under data scarcity

Egyptian coastal lakes represent about 25 % of the Mediterranean total wetlands. Four of the coastal lakes are located north of the Nile Delta and are known as the Northern Delta Lakes. They are severely environmentally degraded and are considered vulnerable to the impacts of climate change, in particular the expected sea level rise. Lake Manzala lies on the eastern north coast of Egypt and is considered as the largest Egyptian coastal lake. Economically, Lake Manzala is considered as one of the most valuable fish sources in Egypt. The water quality status of the lake has been degraded due to the progressive increase in industrial, municipal, and agricultural wastewater discharge. In this work, a hydrodynamic and water quality model for Lake Manzala was developed, under the limitation of hydrological data, which prevented model validation, using MIKE21 modeling system. The proposed model was calibrated with observed data for 1 year (August 2010–July 2011). Typical records at five stations for water levels were used, while the water quality data were collected from 11 field stations. The model results show good agreement with the observed water depth, water temperature, and salinity records. The values of average absolute error, for all stations, were about 0.06 m and 0.56 °C for water depth and water temperature, respectively. In the following, the calibrated model is going to be used to investigate the impacts of future climatic changes on hydrodynamic and water quality characteristics of the lake. Moreover, this developed model will be used as a management tool to examine different enhancement water quality scenarios for the lake.

Current-use pesticides in urban watersheds and receiving waters of western Lake Ontario measured using polar organic chemical integrative samplers (POCIS)

Abstract Surface water contamination with current-use pesticides (CUPs) is usually associated with inputs from agriculture. However, there are several urban sources of these compounds, including pesticides used in public spaces, golf courses, and lawns and gardens; discharges of municipal wastewater containing fungicides from pharmaceuticals and personal care products (PPCPs); and runoff of biocides that are used in construction materials. Polar organic chemical integrative samplers (POCIS) were used to monitor the occurrence of fungicides and selected herbicides in surface waters in the densely populated urban area near Toronto, Canada. Samplers were deployed in five urban streams, one agriculturally dominated stream, and at five locations in the nearshore zone of western Lake Ontario adjacent to urban areas. Sampling rates for target compounds in POCIS determined in laboratory calibration experiments ranged between 0.03 and 0.65 L/day. For herbicides, atrazine was detected at all sites, and diuron, 2,4-D, and mecoprop were frequently detected. The fungicides carbendazim and thiophanate-methyl were detected at all sites, and a hydroxy-metabolite of the fungicide chlorothalonil was also widely detected. Fungicides used in PPCPs (e.g. fluconazole, climbazole) were primarily detected in POCIS deployed in locations impacted by municipal wastewater. Estimated time-weighted average (TWA) concentrations of iprodione and carbendazim in urban streams were consistent with the number of golf courses in the watershed. However, runoff of biocides from building materials may also be a source of these fungicides. Overall, these data indicate that urban environments, as indicated by the Toronto area, have several point and non-point sources of fungicides and other CUPs.

Metal pollution and ecological risk assessment in the surface sediments of Anping Harbor, Taiwan

Surface sediments from 10 stations were sampled in Anping Harbor for heavy metals (Hg, Pb, Cd, Cr, Cu, Zn, and Al), water content, organic matter, total grease as well as grain size. Geo-accumulation index (Igeo), enrichment factor (EF), effect range median quotient, and potential ecological risk index were applied to estimate the degree of metal contamination and the potential ecological risk in sediments. The mean metals concentration with standard deviations (mg/kg) in the surface sediments was 0.28±0.17 of Hg, 0.40±0.27 of Cd, 202 ± 260 of Cr, 99 ± 102 of Cu, 36 ± 16 of Pb, and 257 ± 194 of Zn. For spatial distribution of heavy metals, a relatively high metal content was observed in the Bamboo River mouth region and it progressively decreased towards the harbor region. The estimates of Igeo and EF revealed that sediments of Bamboo River mouth were severely metal contamination. Results showed that upstream industrial and municipal wastewater discharges along the river bank may be the major sources of pollution. For the potential ecological risk assessment, the river mouth of Anping Harbor showed considerable ecological risk, while the other areas posed low and moderate ecological risk. This study can provide valuable information for developing future strategies for the management of river mouth and harbor.

Illinois River Nitrate-Nitrogen Concentrations and Loads: Long-term Variation and Association with Watershed Nitrogen Inputs.

The Illinois River is a major contributor of nitrate-N to the Mississippi River and the Gulf of Mexico, where nitrate is a leading cause of summertime benthic hypoxia. Corn-soybean production on tile-drained land is a leading source of nitrate-N in this river system, in addition to municipal wastewater discharge. We calculated annual nitrate-N loads in the Illinois River at Valley City from 1976 to 2014 by linear interpolation. Although there was not a significant trend in annual loads during the entire study period, there was a significant downward trend in flow-weighted nitrate-N concentration after 1990 despite high concentrations in 2013 after the 2012 drought. Multivariate regression analysis revealed a statistically significant association between annual flow-weighted nitrate-N concentration and cumulative residual agricultural N inputs to the watershed during a 6-yr window. This suggests that declines in flow-weighted nitrate-N concentration may reflect increasing N use efficiency in agriculture and a depletion of legacy N stored in the watershed. The watershed appears to have transitioned from a state of stationarity in nitrate concentration to nonstationarity. The average annual nitrate-N load at Valley City from 2010 to 2014 was 10% less than the 1980-1996 average load, indicating recent progress toward Illinois' nutrient loss reduction milestone of 15% reduction by 2025 and ultimate target of 45% reduction.

Environmental modelling of heavy metals using pollution indices and multivariate techniques in the soils of Bahr El Baqar, Egypt

Fewer studies have assessed the discharge of industrial, agricultural and municipal wastewaters on heavy metal pollution in the Soils of Bahr El Baqar, Egypt. Thirty-four samples were collected and analyzed for heavy metals, which were assessed using different indices. The summary statistics results indicate that Pb, Cd, Cu, Co, Cr and Ni concentrations in Bahr El Baqar soils are higher than those in the reference soil. By applying the Pearson rank order correlations, the result revealed that these metals have the same source of contamination. Average contamination factor values for heavy metals have an order Cd > Cr > Co > Ni > Cu > Pb > Zn > Mn > Fe, suggesting that soil samples were extremely high enriched with Cd, while Pb exhibit significant enrichment. Geoaccumulation index showed that the soils of Bahr El Baqar are having high concentrations of Cd, Ni, Co, and Cr, which exceeded the average standard value. These confirmed that Bahr El Baqar drain is facing probable environmental pollution especially with dangerous heavy metals (Pb, Cd, Co, Cr and Ni). Calculation of different indices indicates the study area falls under moderate to very high contamination degree, which regarded as polluted. These indices are useful tools for identification of anthropogenic source of soil contamination. According to this study, the agricultural activity in the Bahr El Baqar area requires careful consideration.