Groundwater Nutrient Research Articles

Natural groundwater nutrient fluxes exceed anthropogenic inputs in an ecologically impacted estuary: lessons learned from Mobile Bay, Alabama

In this study we evaluated the magnitude and seasonal variations of natural and anthropogenic fluxes of inorganic (NO3−, NH4+, and PO43−) and organic (DON and dissolved organic carbon) nutrients delivered by submarine groundwater discharge (SGD) and rivers to the fourth largest estuary in the USA, Mobile Bay in Alabama. To identify the sources of SGD-nutrient in the estuary and their subsurface biogeochemical transformation, we applied a multi-method approach that combines geochemical nutrient (N and P) mass-balances, stable isotopes (nitrate $$\updelta^{15} {\text{N}}_{{{\text{NO}}_{3} }}$$ and $$\updelta^{18} {\text{O}}_{{{\text{NO}}_{3} }}$$ and sediment organic matter δ13Corg and δ15Norg) signatures, microbial sequencing analyses, dissolved organic matter source-composition, and shallow estuarine sediment lithological analyses. We found that during dry seasons SGD delivered nearly a quarter of the total nutrient inputs to Mobile Bay. These SGD fluxes were anoxic and N was delivered to the bay almost entirely as NH4+ and DON, which represented more than half of the total NH4+ and almost one fifth of the total DON inputs to the bay. We further observed that these significant SGD-derived N fluxes occurred exclusively to the east shore of Mobile Bay, historically impacted by hypoxia and large-scale fish kills known as “Jubilees”. We demonstrate here that although the Mobile Bay coastal area is largely developed and anthropogenic influences are well documented, a shallow peat layer identified only on the east shore serves as the main source of the exceptionally high NH4+ and DON fluxes. We found that the high groundwater NO3− concentrations observed further inland from over-fertilization also identified by previous studies, decreased dramatically as groundwater percolated through the intertidal zone of the coastal aquifer. The microbial community identified in the coastal sediments suggests that denitrification and dissimilatory nitrate reduction to ammonium (DNRA) were the main processes responsible for this extensive removal and transformation of anthropogenic N, respectively. Furthermore, we found no significant anthropogenic inputs from manure or sewage waste to the bay. These findings show that natural sources of nutrients can outcompete anthropogenic inputs despite extensive development of the coastal area. We hypothesize that similar subsurface biogeochemical nutrient transformations can occur in other shallow estuaries of the northern Gulf of Mexico and worldwide.

Managed Aquifer Recharge for Seawater Intrusion

Ground water is, as a rule, continuously seen as a dependable wellspring of supply to satisfy the requirements of residential water system and mechanical sections of the country. The progression practices during the years have ominously impacted the ground water dominion in various areas of the country. Seawater intervention or the movement of brine into the fresh formation zone will increment groundwater saltiness, posing an enormous ecological effect in coastal regions universally. Ocean level ascent and decrease in groundwater levels due to over usage may end up in saline water intervention; moving major ions and nutrients in groundwater. “Saltwater invasion is the biggest and much debated water story in the world these days. It’s a silent problem. It’s easy to ignore politically however it will ruin the water supply for future generations.” India’s water security is in a very unpredictable position. Even by conventional estimates, 40% of individuals in India won’t have drinking water by 2030. As indicated by an IBRD report, at least 21 Indian urban communities are heading towards zero groundwater level by 2020. Managed formation Recharge (MAR) could be an encouraging modification to the present lifestyle to cut back exposure to temperature change and hydrological variability. MAR can take a significant position as a measure to curb over-abstraction and to restore the groundwater balance. It can be utilized to recharge aquifers subject to decreasing yields, to control saltwater intervention or to prevent land collapse. MAR may likewise be employed to support or improve the working of ecosystems and the nature of groundwater.

Place-based management can reduce human impacts on coral reefs in a changing climate.

Declining natural resources have contributed to a cultural renaissance across the Pacific that seeks to revive customary ridge-to-reef management approaches to protect freshwater and restore abundant coral reef fisheries. We applied a linked land-sea modeling framework based on remote sensing and empirical data, which couples groundwater nutrient export and coral reef models at fine spatial resolution. This spatially explicit (60×60m) framework simultaneously tracks changes in multiple benthic and fish indicators as a function of community-led marine closures, land-use and climate change scenarios. We applied this framework in Hā'ena and Ka'ūpūlehu, located at opposite ends of the Hawaiian Archipelago to investigate the effects of coastal development and marine closures on coral reefs in the face of climate change. Our results indicated that projected coastal development and bleaching can result in a significant decrease in benthic habitat quality and community-led marine closures can result in a significant increase in fish biomass. In general, Ka'ūpūlehu is more vulnerable to land-based nutrients and coral bleaching than Hā'ena due to high coral cover and limited dilution and mixing from low rainfall and wave power, except for the shallow and wave-sheltered back-reef areas of Hā'ena, which support high coral cover and act as nursery habitat for fishes. By coupling spatially explicit land-sea models with scenario planning, we identified priority areas on land where upgrading cesspools can reduce human impacts on coral reefs in the face of projected climate change impacts.

A framework for conceptualizing groundwater-surface water interactions and identifying potential impacts on water quality, water quantity, and ecosystems

Developing an understanding of how groundwater (GW) and surface water (SW) systems function and interact to impact water quantity, water quality, and ecosystem health provides a basis for management of water resources, environmental protection, and land management. Although knowledge of these complex and dynamic systems has improved in recent decades, there is currently no systematic guidance for conceptualizing and evaluating GW-SW interactions and identifying their potential impact on management issues. For this reason, a holistic framework was created to provide a comprehensive and logical approach for identifying, understanding, and evaluating the key factors and processes controlling GW-SW interactions and understanding their relationship to environmental problems. The framework identifies fundamental hydrological, biogeochemical, and biological processes and critical factors to consider when developing robust conceptual models of GW-SW systems. The framework is comprehensive and can be adapted to different problems using only the aspects necessary to address a specific issue. The framework focuses on streams, rivers, and lakes but can be adapted for use in other GW-SW settings such as ponds, wetlands, and coastal marine environments. Applicability of the framework is illustrated through evaluation of three GW-SW interaction settings in southern Ontario, Canada: a groundwater contaminant plume discharging to the Pine River, discharge of groundwater nutrients to Lake Huron, and a regional-scale conceptualization of GW-SW flow interactions in the Duffins Creek watershed. The case studies highlight flexibility of the framework to develop conceptual models, assess environmental issues, identify knowledge gaps, and provide a basis for designing site investigations.

Phosphorus and nitrogen loading to Lake Huron from septic systems at Grand Bend, ON

Groundwater nutrient loading to L. Huron was assessed along a 1.7 km section of beach at Grand Bend, ON, Canada, where septic systems are used for wastewater disposal. The artificial sweetener acesulfame (ACE) was detected in all groundwater samples (7–842 ng/L, n = 78), revealing that the entire surficial aquifer was impacted by septic system wastewater. Nitrate concentrations (3.5 ± 1.4 mg/L, n = 78) were correlated with ACE (r2 = 0.54), indicating that septic systems contribute to nitrate loading in the aquifer. Chloride was also elevated (37 ± 11 mg/L, n = 78), but was not correlated with ACE (r2 = 0.008), indicating a non wastewater source was dominant, likely road salt. Soluble reactive phosphorus (SRP) values were low (5.3 ± 9.3 μg/L, n = 77) and were not correlated with ACE (r2 = 0.006). Sediment profiling below two of the septic system drain-fields, showed that the sand grains had distinct secondary coatings containing P, indicating that mineral precipitation reactions played a role in limiting P concentrations present in the aquifer. Groundwater nutrient loading to the lake was estimated at 13,000 kg N/year from NO3− and 1.9 kg P/year from SRP. These amounts are insignificant compared to nutrient loading from a stream that drains an agricultural catchment and discharges to the lake at the north end of the study site (Parkhill Creek). This calls into question, in some cases, the rationale of decommissioning properly functioning septic systems as a mitigation measure for reducing nutrient loading to nearby water courses.

Economic and environmental consequences of overfertilization under extreme weather conditions

Higher-than-recommended fertilizer application is considered by farmers as insurance to maintain sufficient levels of plant nutrients during periods of excessive rainfall, or to capitalize on favorable market conditions and facilitate an extended harvest period. In addition to increasing the likelihood of eutrophic waters, excess fertilizer application may exacerbate soil salinity that reduces yields and economic benefits after extreme weather events such as hurricanes. Research-based fertilizer recommendations are needed to address global eutrophication of fresh water systems. A three-year, four-season study evaluated the effects of higher-than-recommended nutrient and water inputs on tomato (Solanum lycopersicum) yield and farm profitability under normal and extreme weather conditions in subtropical Florida, a major fresh vegetable producing region. Three nutrient-water management treatments were considered: conventional high fertilizer rate with subirrigation (High-Sub), recommended (best management practice) fertilizer rate with subirrigation (Rec-Sub), and recommended fertilizer rate with subsurface drip irrigation (Rec-Drip). There were significant differences in yield between seasons (i.e., Fall, Year 1 = 52,742 kg ha−1; Fall, Year 2 = 22,045 kg ha−1; Spring, Year 3 = 78,926 kg ha−1; and Fall, Year 3 = 61,905 kg ha−1). Yield reductions in Year 2, an unusually wet season affected by Hurricane Wilma (21 cm rain in 11 hours), were related to high nitrogen (N) losses and soil salinity (electrical conductivity > 2,500 μS cm−1). Average groundwater N, seasonal groundwater electrical conductivity, and soil N indicated high salt concentrations and leaching in High-Sub especially during Fall Year 2. There were no statistically significant yield differences among treatments. Growers, however, tend to look at the differences in average yields for trends in farm profits and losses. With this perspective in mind, we conducted a grower-type economic calculation using prevailing market prices that showed additional revenues (US$12,000 ha−1) from Rec-Sub and Rec-Drip during Fall Year 2, which almost entirely balanced the lower revenues for remaining seasons. National market prices for tomato were highest during Fall Year 2 due to extensive crop damage (wind and flooding) from Hurricane Wilma. Given the average frequency of a tropical storm/hurricane being three years, growers may enjoy an economic benefit once every three years from not applying excess fertilizer, and at the same time, avoid external environmental costs that include publicly funded treatment systems. Reduced groundwater nutrient concentration (N = 61% and phosphorus [P] = 42%) in Rec-Sub could achieve similar reductions in nutrient loads in regions such as Florida, which have significant surface water and groundwater interaction. Future increases in frequency and magnitude of extreme events (e.g., 2017 Hurricane Irma, rainfall = 37 cm) may exacerbate the impacts on production and water quality. Therefore, excessive fertilization is not likely to be economically or environmentally sustainable.

Seasonality of Nutrient Flux and Biogeochemistry in an Intertidal Aquifer

AbstractBiogeochemical reactions in coastal aquifers highly affect the nutrient flux associated with submarine groundwater discharge (SGD) to the ocean, which subsequently influences the oceanic environment and ecology. This study investigates a seasonal variation of SGD‐derived nutrient flux to the ocean and nutrient biogeochemistry in an intertidal aquifer of Tolo Harbor, Hong Kong. The results show that the inventory of NOx− and PO43− in the intertidal aquifer has a clear seasonality with a large inventory in summer, a small inventory in spring, and a median inventory in autumn and winter, respectively. Differently, the inventory of NH4+ is large in winter and summer and small in spring and autumn, which results from the coupled effects of seasonal change of both production and removal of NH4+ in the aquifer. The SGD‐derived nutrient (NH4+, NOx−, and PO43−) flux is the highest in summer (271.71, 24.86, and 116.66 mmol·day−1·(m coastline)−1) and is the lowest in spring (114.83, 1.70, and 20.26 mmol·day−1·(m coastline)−1). The majority of SGD‐derived nutrient flux is supported by the local remineralization of organic matter along with seawater infiltration. In autumn, the recharge of seawater induced by tidal pumping significantly shifts the biogeochemical balance of nutrients and is the major source of groundwater nutrients in the intertidal aquifer. Among the various nutrient fluxes (SGD, river discharge, atmospheric deposition, and benthic sediment diffusion) to Tolo Harbor, SGD‐derived PO43− flux is the second major source of seawater PO43− in addition to benthic sediment diffusion. The PO43− loading via SGD is of significance to the primary production in the phosphorus‐limited environment in Tolo Harbor. After considering the natural attenuation of nutrients in a sandy/silty beach aquifer, this study suggests the overestimation of SGD‐derived nutrient loading estimated previously that simply use average nutrient concentration of fresh SGD endmember and saline SGD endmember as the nutrient concentration of total SGD endmember.

Seasonal variability of land-ocean groundwater nutrient fluxes from a tropical karstic region (southern Java, Indonesia)

In tropical karstic regions, knowledge about the timing and quantity of land-ocean groundwater nutrient fluxes is important, as those nutrients may affect sensitive coastal ecosystems such as coral reefs. High permeability of karst aquifers, combined with high discharge during heavy rain events, lead to a close connectivity between groundwater in the hinterland and the coastal zone. Alteration between dry and wet periods can lead to a temporal variability of groundwater discharge volume and its associated nutrient fluxes. We studied the seasonal variability of land-ocean groundwater nutrient fluxes in the tropical karstic region of Gunung Kidul (southern Java, Indonesia) from November 2015 to December 2016. Satellite thermal infrared imagery revealed two major areas of direct submarine and coastal groundwater discharge. Nutrient fluxes were estimated at the largest coastal spring using a discharge dataset from a subsurface river dam and a monthly record of nutrient concentrations sampled from the spring. Nitrate fluxes ranged from 6 × 106–245 × 106 mol/day, dissolved silicon fluxes from 58 × 106–546 × 106 mol/day and phosphate fluxes from 17 × 103–1571 × 103 mol/day. Nutrient fluxes are mostly controlled by discharge and show a high variability through time. Extraordinarily high nitrate and phosphate fluxes were observed after a period of constant and heavy rain. Most likely a nutrient pool in the top soil in the hinterland from untreated sewage or fertilizer is flushed during rain events through the aquifer to the coast. In tropical karstic regions sudden inputs of large amounts of nutrients via groundwater discharge may affect coastal ecosystems such as coral reefs making them especially vulnerable during high discharge events.

The Impact of Landscape Characteristics on Groundwater Dissolved Organic Nitrogen: Insights From Machine Learning Methods and Sensitivity Analysis

AbstractThe effect of groundwater nutrient inputs on river and estuary water quality and the potential impacts of urbanization on groundwater are central concerns in many coastal areas. It has been previously identified that dissolved organic nitrogen (DON) can be the dominant form of total dissolved nitrogen (TDN) in some aquifers. However, there is a paucity of evidence about the sources and flow paths of DON, relative to inorganic nitrogen in groundwater. DON and dissolved organic carbon/DON were first compared against different landscape variables in this study, and no significant relationships were found. However, the relationships became statistically significant when shallow samples (sampling depth < 10 m) were separated from deep samples. A random forest model and sensitivity analysis were then applied to further our understanding of the ecohydrological drivers and seasonal patterns that shape DON variability. The random forest algorithm was built to classify 171 groundwater wellbores into three classes (low: <0.5 mg/L; medium: 0.5–2.5 mg/L; and high: >2.5 mg/L) which achieved 72% classification accuracy using landscape characteristics, hydrological conditions, and temporal information. The results indicated that the effects of landscapes on sandy shallow groundwater DON were controlled both by certain landscape characteristics and depth to groundwater. A conceptual model of groundwater DON is therefore proposed where the balance of exposure and processing time scales from the surface to groundwater is the critical control on the preservation of landscape signatures; we expect that this conceptual model would be applicable for other sandy, shallow groundwater areas.

Seawater recirculation drives groundwater nutrient loading from a developed estuary shoreline with on-site wastewater treatment systems: Mobile Bay, USA

Previous studies have highlighted the influence of submarine groundwater discharge (SGD) on the environmental condition of coastal waters worldwide. Here, we focus on the quantity and quality of SGD from a developed estuarine shoreline in Mobile Bay to investigate the effects of residential development, specifically on-site wastewater treatment, on coastal water quality. A variety of techniques including a hydrologic balance, Darcy calculations, seepage meter observations, and coastal water radon-222 surveys were employed to quantify fresh and total components of SGD under varying hydrometeorological scenarios. Samples of groundwater from shallow wells, SGD from seepage meters, and surface water were analyzed for dissolved nutrients throughout the year to determine nutrient sources and loadings to the Bay. Comparisons of SGD yielded by Darcy’s calculations with seepage meter and radon-222 observations revealed that fresh, meteoric groundwater contributes only a minor fraction (~ 7%) of total SGD, thereby suggesting that seawater recirculation is the dominant mechanism driving SGD. Total dissolved nitrogen loading averaged 1960 mmol d−1 per m shoreline for the duration of the study; however, total dissolved nitrogen loading supported by the fresh, meteoric SGD component was only 11.2 mmol d−1 per m shoreline (less than 1% of the total loading), despite the presence of on-site wastewater treatment systems. These results demonstrate the importance of SGD as a source of nutrients to Mobile Bay and suggest that nutrient loading from regeneration and remineralization processes in the subterranean estuaries can exceed that of groundwater nutrient transport from developed watersheds.

Groundwater contamination by sewage causes benthic algal outbreaks in the littoral zone of Lake Baikal (East Siberia)

Abstract Lake Baikal, an ancient lake in Siberia, contains more endemic species than any other lake in the world with most of them residing in the benthic littoral zone. Explosive growth of benthic Spirogyra, a filamentous green alga, began approximately in 2011 in localized coastal areas, with the most severe examples occurring near coastal towns that lack a wastewater treatment facility or have a malfunctioning system. At other sites (small settlements, harbors), however, the cause of its excess growth is less obvious. Multiple hypotheses have been offered including lake level fluctuations, climate warming, a relaxation of grazing pressure, and coastal eutrophication. We assessed these hypotheses using data on historical lake levels, water temperature, the spatial-temporal distribution of Spirogyra along inhabited and non-inhabited shorelines, and measurements of fecal coliform bacteria and nutrients in ground water, interstitial water, and lake water. These data suggest that groundwater contamination is the primary cause of coastal eutrophication. Most houses and buildings in small settlements around Lake Baikal lack septic tanks but use unlined cesspools to collect human waste. This untreated human waste enters groundwater via passive filtration through permeable soils and flows to the coastal zone where it drives excess growth of Spirogyra. Remediation — including installation of septic systems, modernization of existing sewage treatment plants in coastal towns, and the adoption of non-phosphate containing detergents — as well as a reconsideration of the federal monitoring system regarding the coastal zone is urgently needed to protect this extraordinary lake.

Quantifying Processes Governing Nutrient Concentrations in a Coastal Aquifer via Principal Component Analysis

Submarine groundwater discharge (SGD) is an important source of nutrients to coastal ecosystems. The flux of nutrients associated with SGD is governed by the volumetric discharge of groundwater and the concentrations of nutrients in groundwater within the coastal aquifer. Nutrient concentrations in the coastal aquifer, in turn, are controlled by processes such as mixing, precipitation, adsorption-desorption, the decay of organic material, and nitrogen-fixation/denitrification. In this study, Principal Component Analysis (PCA) was applied to groundwater and ocean water nutrient concentration data from Monterey Bay, California, to identify and rank processes controlling coastal aquifer nutrient concentrations. Mixing with seawater, denitrification, the decay of organic matter, and desorption of phosphate were determined to be the three most important processes accounting for 39%, 19%, 14%, and 12% of the variability, respectively. This study shows how PCA can be applied to SGD studies to quantify the relative contribution of different processes controlling nutrient concentrations in coastal aquifers.

Groundwater nutrient inputs into an urbanized tropical estuary system in Indonesia

Groundwater discharge is known to transport nutrients into estuaries at several locations around the world. However, few studies report groundwater-associated nutrient fluxes from tropical developing regions such as Southeast Asia, even though this area shows the strongest human modifications in the coastal zone worldwide. We investigated groundwater nutrient flux into two streams and estuaries (Awur and Sekumbu Bay) in the urban area of Jepara, Indonesia, and its relation with the land usage surrounding the estuaries.We found that average concentrations of NO3, NH4, and PO4 in Jepara's aquifer reached 145μM, 68μM, and 14μM, respectively, and our results indicate that these were mainly originated from untreated sewage, agriculture, and manure input. Approximately 2200tonNyear−1 and 380tonPyear−1 were removed in the soil and aquifer before the nutrients were discharged into the river. The total groundwater discharge into the river and estuary was estimated to 461×103m3d−1, or up to 42% of the river discharge. Discharge of groundwater-associated NO3 (72×103mold−1), NH4 (34×103mold−1), PO4 (5×103mold−1), and additional surface runoff may contribute to eutrophication and a decrease of nearshore surface water quality. Nutrient concentrations in groundwater, river, and coastal seawater in the Jepara region are similar to those found in major urban areas in Southeast Asia, e.g. Manila and Bangkok, even though Jepara has smaller size and population. Thus, our results indicate that medium populated cities with highly modified regional land use can contribute a significant amount of nutrient discharge in the coastal area and should be included in global assessments of nutrient budget calculation.

Radium tracing nutrient inputs through submarine groundwater discharge in the global ocean

Riverine and atmospheric inputs are often considered as the main terrestrial sources of dissolved inorganic nitrogen (DIN), phosphorus (DIP), and silicon (DSi) in the ocean. However, the fluxes of nutrients via submarine groundwater discharge (SGD) often exceed riverine inputs in different local and regional scale settings. In this study, we provide a first approximation of global nutrient fluxes to the ocean via total SGD, including pore water fluxes, by combining a global compilation of nutrient concentrations in groundwater and the SGD-derived 228Ra fluxes. In order to avoid overestimations in calculating SGD-derived nutrient fluxes, the endmember value of nutrients in global groundwater was chosen from saline groundwater samples (salinity >10) which showed relatively lower values over all regions. The results show that the total SGD-derived fluxes of DIN, DIP, and DSi could be approximately 1.4-, 1.6-, and 0.7-fold of the river fluxes to the global ocean (Indo-Pacific and Atlantic Oceans), respectively. Although significant portions of these SGD-derived nutrient fluxes are thought to be recycled within sediment-aquifer systems over various timescales, SGD-derived nutrient fluxes should be included in the global ocean budget in order to better understand dynamic interactions at the land-ocean interface.

Groundwater impacts on surface water quality and nutrient loads in lowland polder catchments: monitoring the greater Amsterdam area

Abstract. The Amsterdam area, a highly manipulated delta area formed by polders and reclaimed lakes, struggles with high nutrient levels in its surface water system. The polders receive spatially and temporally variable amounts of water and nutrients via surface runoff, groundwater seepage, sewer leakage, and via water inlets from upstream polders. Diffuse anthropogenic sources, such as manure and fertiliser use and atmospheric deposition, add to the water quality problems in the polders. The major nutrient sources and pathways have not yet been clarified due to the complex hydrological system in lowland catchments with both urban and agricultural areas. In this study, the spatial variability of the groundwater seepage impact was identified by exploiting the dense groundwater and surface water monitoring networks in Amsterdam and its surrounding polders. A total of 25 variables (concentrations of total nitrogen (TN), total phosphorus (TP), NH4, NO3, HCO3, SO4, Ca, and Cl in surface water and groundwater, N and P agricultural inputs, seepage rate, elevation, land-use, and soil type) for 144 polders were analysed statistically and interpreted in relation to sources, transport mechanisms, and pathways. The results imply that groundwater is a large source of nutrients in the greater Amsterdam mixed urban–agricultural catchments. The groundwater nutrient concentrations exceeded the surface water environmental quality standards (EQSs) in 93 % of the polders for TP and in 91 % for TN. Groundwater outflow into the polders thus adds to nutrient levels in the surface water. High correlations (R2 up to 0.88) between solutes in groundwater and surface water, together with the close similarities in their spatial patterns, confirmed the large impact of groundwater on surface water chemistry, especially in the polders that have high seepage rates. Our analysis indicates that the elevated nutrient and bicarbonate concentrations in the groundwater seepage originate from the decomposition of organic matter in subsurface sediments coupled to sulfate reduction and possibly methanogenesis. The large loads of nutrient-rich groundwater seepage into the deepest polders indirectly affect surface water quality in the surrounding area, because excess water from the deep polders is pumped out and used to supply water to the surrounding infiltrating polders in dry periods. The study shows the importance of the connection between groundwater and surface water nutrient chemistry in the greater Amsterdam area. We expect that taking account of groundwater–surface water interaction is also important in other subsiding and urbanising deltas around the world, where water is managed intensively in order to enable agricultural productivity and achieve water-sustainable cities.

Groundwater Nutrient Concentrations and Mass Loading Rates at Iowa Golf Courses

AbstractGolf courses are often considered by the public to be significant nitrogen (N) and phosphorus (P) nonpoint sources but only limited information exists on nutrient concentrations and loads in golf course groundwater. In this study, we measured N and P concentrations in groundwater and available surface water at six randomly selected Iowa golf courses to assess the loading risk posed by these facilities to groundwater and local rivers. At each course, three shallow monitoring wells were installed, one each on representative tee, fairway, and rough locations. Wells and available surface water were sampled on eight occasions during 2015 and 2016. NO3‐N concentrations were not detected above 1 mg/L at three of the six courses monitored in this study and the overall mean NO3‐N concentration in Iowa golf courses was 2.2 mg/L. The mass of NO3‐N recharged to groundwater averaged 3.3 kg/ha at the six courses, which represents approximately one‐tenth of the NO3‐N load exported by the watershed that contains the course and represented approximately 0.1 to 8% of the fertilizer N applied. Groundwater orthophosphorus concentrations averaged 0.13 mg/L and were similar to those measured in a variety of settings across Iowa. Study results should prove useful in evaluating nutrient contributions from golf courses in Midwestern states where nutrient reduction strategies are being pursued.

Septic systems contribute to nutrient pollution and harmful algal blooms in the St. Lucie Estuary, Southeast Florida, USA

Nutrient enrichment is a significant global-scale driver of change in coastal waters, contributing to an array of problems in coastal ecosystems. The St. Lucie Estuary (SLE) in southeast Florida has received national attention as a result of its poor water quality (elevated nutrient concentrations and fecal bacteria counts), recurring toxic Microcystis aeruginosa blooms, and its proximity to the northern boundary of tropical coral species in the United States. The SLE has an artificially large watershed comprised of a network of drainage canals, one of which (C-44) is used to lower the water level in Lake Okeechobee. Public attention has primarily been directed at nutrient inputs originating from the lake, but recent concern over the importance of local watershed impacts prompted a one-year watershed study designed to investigate the interactions between on-site sewage treatment and disposal systems (OSTDS or septic systems), groundwaters, and surface waters in the SLE and nearshore reefs. Results provided multiple lines of evidence of OSTDS contamination of the SLE and its watershed: 1) dissolved nutrients in groundwaters and surface waters were most concentrated adjacent to two older (pre-1978) residential communities and the primary canals, and 2) sucralose was present in groundwater at residential sites (up to 32.0μg/L) and adjacent surface waters (up to 5.5μg/L), and 3) δ15N values in surface water (+7.5 o/oo), macroalgae (+4.4 o/oo) and phytoplankton (+5.0 o/oo) were within the published range (>+3 o/oo) for sewage N and similar to values in OSTDS-contaminated groundwaters. Measured δ15N values in M. aeruginosa became increasingly enriched during transport from the C-44 canal (∼5.8 o/oo) into the mid-estuary (∼8.0 o/oo), indicating uptake and growth on sewage N sources within the urbanized estuary. Consequently, there is a need to reduce N and P loading, as well as fecal loading, from the SLE watershed via septic-to-sewer conversion projects and to minimize the frequency and intensity of the releases from Lake Okeechobee to the SLE via additional water storage north of the lake. These enhancements would improve water quality in both the SLE and Lake Okeechobee, reduce the occurrence of toxic harmful algal blooms in the linked systems, and improve overall ecosystem health in the SLE and downstream reefs.

Nitrogen enrichment and speciation in a coral reef lagoon driven by groundwater inputs of bird guano

AbstractWhile the influence of river inputs on coral reef biogeochemistry has been investigated, there is limited information on nutrient fluxes related to submarine groundwater discharge (SGD). Here, we investigate whether significant saline groundwater‐derived nutrient inputs from bird guano drive coral reef photosynthesis and calcification off Heron Island (Great Barrier Reef, Australia). We used multiple experimental approaches including groundwater sampling, beach face transects, and detailed time series observations to assess the dynamics and speciation of groundwater nutrients as they travel across the island and discharge into the coral reef lagoon. Nitrogen speciation shifted from nitrate‐dominated groundwater (>90% of total dissolved nitrogen) to a coral reef lagoon dominated by dissolved organic nitrogen (DON; ∼86%). There was a minimum input of nitrate of 2.1 mmol m−2 d−1 into the lagoon from tidally driven submarine groundwater discharge estimated from a radon mass balance model. An independent approach based on the enrichment of dissolved nutrients during isolation at low tide implied nitrate fluxes of 5.4 mmol m−2 d−1. A correlation was observed between nitrate and daytime net ecosystem production and calcification. We suggest that groundwater nutrients derived from bird guano may offer a significant addition to oligotrophic coral reef lagoons and fuel ecosystem productivity and the coastal carbon cycle near Heron Island. The large input of groundwater nutrients in Heron Island may serve as a natural ecological analogue to other coral reefs subject to large nutrient inputs from anthropogenic sources.

ε-polylysine biopolymer for coagulation of clay suspensions

The coagulation or flocculation of cohesive clay suspensions is one of the most widely used treatment technologies for contaminated water. Flocculated clay can transport pollutants and nutrients in ground water. Coagulants are used to accelerate these mechanisms. However, existing coagulants (e.g., polyacrylamide, polyaluminum chloride) are known to have harmful effects in the environment and on human health. As an alternative, eco-friendly coagulant, this study suggests <TEX>${\varepsilon}-polylysine$</TEX>, a cationic biopolymer fermented by Streptomyces. A series of sedimentation experiments for various <TEX>${\varepsilon}-polylysine$</TEX> concentrations were performed, and the efficiency of sedimentation with <TEX>${\varepsilon}-polylysine$</TEX> was estimated by microscopic observation and light absorbance measurements. Two types of sedimentation were observed in the experiments: accumulation sedimentation (at 0.15%, 0.20%, 0.25% <TEX>${\varepsilon}-polylysine$</TEX>) and flocculation sedimentation (at 0%, 0.1%, 0.5%, 1.0%, 2.0% <TEX>${\varepsilon}-polylysine$</TEX>). These sedimentation types occur as a result of the concentration of counter ions. Additionally, the performance of <TEX>${\varepsilon}-polylysine$</TEX> was compared with that of a previously used environmentally friendly coagulant, chitosan. The obtained results indicate that flocculation sedimentation is appropriate for contamination removal and that <TEX>${\varepsilon}-polylysine$</TEX> functions more efficiently for clay removal than chitosan. From the experiments and analysis, this paper finds that polylysine is an alternative eco-friendly coagulant for removing chemical contaminants in groundwater.

Efficiency of old and young shelterbelts in reducing the contents of nutrients in Luvisols

The purpose of this study was to determine the effect of shelterbelts as biogeochemical barriers that can reduce the concentration of nutrients in groundwater migrating from adjacent cultivated fields. The shelterbelts differed in age, trees species composition and soil organic carbon content. The investigations were carried out in Luvisols, in the western part of Poland. Soil samples were taken from the topsoil (0–20cm) and then pH, soil organic carbon (SOC), total nitrogen (TN), exchangeable acidity, cation exchange capacity (CEC), particle size distribution, bulk density, porosity and hydraulic conductivity were analysed. Introduction of shelterbelts in a uniform agricultural landscape is one of the best ways for managing the water regime in the landscape. Surface runoff and percolation of water through a soil profile are controlled by shelterbelts. The studies conducted in the agricultural landscape showed that the 200-year-old shelterbelt (Old) with Robinia pseudoacacia L. as the dominant species and the 20-year-old (Young) multispecies shelterbelt effectively limit nitrate nitrogen (NO3−-N) and phosphate phosphorus (PO43−-P) in the groundwater. In the Old shelterbelt, the concentration of NO3−-N was lower by 60%, and in the Young shelterbelt, by 22% in relation to the groundwater migrating from the adjacent cultivated fields. However, the concentrations of PO43−-P decreased to 63% (Old shelterbelt) and 56% (Young shelterbelt) in comparison to the groundwater under the adjacent cultivated fields. In contrast to NO3−-N, the ammonium nitrogen (NH4+-N) behaved in an entirely different way. The concentration of NH4+-N increased in the groundwater under both the Old and Young shelterbelts. The balance of nitrogen and phosphorus inputs and outputs in a shelterbelt indicated that the internal recycling of these elements is of crucial importance for the effective control of the spread of nitrogen and phosphorus compounds in the environment.