Quantifying microplastics in environmental waters: Mass concentrations are superior to abundance

Woodchip bioreactors that stimulate denitrification are proposed to reduce nitrogen (N) loads emanating from subsurface agricultural drainage. However, agricultural drainage water contains both N and phosphorus (P), frequently in concentrations exceeding environmental criteria. A mixed-media bioreactor containing woodchips plus reactive media that binds soluble P could concurrently lower both N and P loads in subsurface agricultural drainage. This study evaluated the P concentration and load reductions achieved with woodchip and mixed-media bioreactors in full-scale field installations in the cold, humid climate of Quebec, Canada, during a three-year period. Bioreactors contained either woodchips-only or woodchips plus an activated alumina/gravel mixture (mixed media). Total P, particulate P, soluble P, soluble reactive P, and soluble organic P concentrations and loads for the bioreactor influents and effluents were assessed weekly and also following >10 mm rainfall events. In the first two months of operation, both woodchips-only and mixed-media bioreactors released P but became either a negligible source or net sink for P retention within the first year of operation. While the mixed-media bioreactor had 9% lower total P concentration and about 19 times greater reduction in total P load than woodchips-only bioreactors during the study period, the total P concentration was not reduced to the critical environmental threshold level of 0.03 mg L⁻¹ with either bioreactor type. Both configurations were effective at reducing the soluble P fraction, especially the soluble reactive P species that are bioavailable and thus contribute directly to eutrophication. A woodchips-only bioreactor can adsorb P from subsurface agricultural drainage; however, a woodchips bioreactor containing the activated alumina/gravel mixture has greater P sorption capacity and should be considered as part of an integrated system for concurrent N and P removal from subsurface agricultural drainage.

Supplementing Bacillus sp. RS1 with Dechloromonas sp. HZ for enhancing selenate reduction in agricultural drainage water

A cost-effective remediation method is needed to remove selenium (Se) from Se-contaminated water. In this study, a selenate [Se(VI)]-reducing bacterium, Citrobacter braakii, that is capable of using molasses as a carbon source to reduce Se(VI) from natural river and drainage waters was isolated. During an 8-day experiment, 87-97% of the added Se(VI) in New River water and White River water, California, was reduced to elemental Se [Se(0)] or transformed to organic Se. In highly saline drainage water, removal of Se(VI) by C. braakii was limited, with 20% Se(VI) removal in a 7-day experiment. Addition of zero-valent iron (ZVI) into these waters along with C. braakii inoculation significantly enhanced the removal of Se(VI) and reduced the formation of organic Se. This study suggests that the combination of a bacterial treatment using inexpensive molasses and ZVI can effectively remove Se from natural river water and agricultural drainage waters.

An economic evaluation of the effect of irrigating tomato plants with agricultural drainage water remediated with DHS technology was conducted in a field experiment at Rahawy, Giza governorate. According to the findings, Egypt's reuse of agricultural drainage water meets around 15% of its irrigation needs, while the overall expenses of remediating one cubic metre of agricultural drainage water using DHS technology reached LE 1.03. The volume of irrigation water used to grow tomato plants decreased by 5% in non-remediated soil ecosystems, 14% in soil ecosystems remediated by microbial inoculation and fortified by bentonite clay mineral, and 22% in soil ecosystems receiving a mix of clay minerals, rock phosphate, and sulphur and inoculated by Thiobacillus sps and phosphate dissolving bacteria PDB. the productivity of one feddan of tomato crop irrigated with non-remediated agricultural drainage water reached 11.31 tons per feddan, irrigation with agricultural drainage water increased tomato crop by about 31%, all studied indicators of the economic efficiency of tomato production grown in remediated soil ecosystem and irrigated with remediated agricultural drainage water were higher than their counterparts grown in non-remediated soil ecosystem and irrigated with non-remediated agricultural drainage water, total tomato yield increased under irrigation with remediated agricultural drainage to LE 31.668, reaching 47% over its counterpart grown in non-remediated soil ecosystem irrigated with non-remediated agricultural drainage water, the net yield per feddan increased by 716% under irrigation with remediated agricultural drainage water over its counterpart irrigated with non-remediated agricultural drainage water. When irrigated with remediated agricultural drainage water, the cost of one tonne of tomato fruits harvested from non-remediated, remediated with bacteria, or remediated with clay minerals soil ecosystems decreased by 11%, 40%, and 44%, respectively, when compared to its counterparts irrigated with non-remediated agricultural drainage water. The profitability of one pound spent on tomato fruits harvested from non-remediated, remediated with bacteria, or remediated with clay minerals soil ecosystems decreased by 598 percent, 1010 percent, and 163 percent more than its counterpart irrigated with non-remediated agricultural drainage water, respectively, under irrigation with remediated agricultural drainage water. The net return of the water unit increased by 761 percent, 1367 percent, and 282 percent in tomato fruits harvested from non-remediated, remediated with certain microorganisms, or remediated with clay minerals soil ecosystems under irrigation with remediated agricultural drainage water, respectively, over its counterpart irrigated with non-remediated agricultural drainage water. The estimated profitability of each pound spent on agricultural drainage water remediation was LE 2.36 for tomato plants growing in an unremediated soil ecosystem, LE 10.07 for those remediated with specific microbes, and LE 33.43 for those remediated with clay minerals. The economic valuation of irrigating tomato plants with agricultural drainage water remediated with DHS technology was good, which will support farmers' social acceptance and sustainability of DHS use.

Constant carbon dosing of a pilot-scale denitrifying bioreactor to improve nitrate removal from agricultural tile drainage

Irrigation of fish farms with agricultural drainage water may affect cultured fish species. So, the present study utilizes antioxidants supplemented diet to overcome deterioration of drainage water and its negative effect on fish. The studied groups are fish cultured in dechlorinated tap water as control group or drainage water and fed commercial basal diet. While, the other studied groups represented by Oreochromis niloticus fish cultured in drainage water and fed either commercial diet supplemented with vitamin C (5 g/kg diet) or fennel (5 g/kg diet) for 12 weeks. Results of the water physico-chemical parameters of all studied treatments revealed deterioration of the drainage water with a decrease in dissolved oxygen and an increase in pH, total hardness, total alkalinity, salinity, ammonia, nitrite and heavy metals (Cu, Pb and Cd) with significant differences (P ≤ 0.01) in comparison to that of the control dechlorinated tap water group. Data clarified also that Oreochromis niloticus cultured in drainage water showed a decrease in growth rate accompanied by deterioration of fish meat quality. However, fish reared in the same drainage water for the same exposure period and fed vitamin C or fennel supplemented basal diet (5 g/kg diet) recorded values of the studied parameters more or less similar to that of control group fish. Data of the present study, empowered aquaculturist to supplement fish rations with fennel or vitamin C as antioxidants to improve fish growth rate, meat quality as well as protect fish against heavy metals toxicity that could threat Human Being.

Trace levels of the veterinary antibiotic compound sulfadiazine (SDZ) can be determined in agricultural drainage water samples with this new method. Optimized sample pretreatment and solid-phase extraction was combined with liquid chromatography coupled to tandem mass spectrometry (SPE LC-MS/MS) using positive electrospray ionization. The linear dynamic range for the LC-MS/MS was assessed from 5 μg/L to 25 mg/L with a 15-point calibration curve displaying a coefficient of correlation r(2) = 0.9915. Agricultural drainage water spiked at a concentration of 25 ng/L gave recoveries between 63 and 98 % (relative standard deviation 15 %), while at 10 ng/L, it showed a lower recovery of 32 % (relative standard deviation 47 %). The final SPE LC-MS/MS method had a limit of detection (LOD)(Method) and a limit of quantification (LOQ)(Method) of 7.5 and 23 ng/L agricultural drainage water, respectively. Determination of SDZ, spiked at a realistic concentration of 50 μg/L, in artificial drainage water (ADW) containing common and high levels of phosphate (0.05, 0.5, and 5 mg/L) gave recoveries between 70 and 92 % (relative standard deviation 7.4-12.9 %). Analysis of the same realistic concentration of SDZ in ADW, spiked with common and high levels of dissolved organic carbon (2, 6, and 15 mg/L) confirmed the possible adaptation of a tandem solid-phase extraction (strong anion exchange (SAX)-hydrophilic-lipophilic balance (HLB)) followed by liquid chromatography-tandem mass spectrometry methodology. Recoveries obtained ranged from 104 to 109 % (relative standard deviation 2.8-5.2 %). The new methods enable determination of the veterinary antibiotic compound SDZ in agricultural drainage water from field experiments and monitoring schemes for phosphate- and dissolved organic carbon (DOC)-rich water samples in intensive farming areas.

Microplastic (MP) contamination in the marine environment has received growing attention. In 2022, the surface water of the U-Taphao River was sampled four times, in February, April, June, and August. The surface water samples were taken at seven different locations, ranging from upstream to downstream parts of the river. The results reveal that the number of MPs detected at the U-Taphao River in February, April, June, and August were 0.41 ± 0.08, 0.25 ±0.06, 0.24 ± 0.11, and 0.26 ± 0.06 particles/L, respectively. The MPs in the U-Taphao River each month were not statistically different (p = 0.190). The trend of the number of MPs found declined from upstream to downstream. Fibers were the most commonly found MPs in the U-Taphao River in this study and were found at more than 80% of all stations during all sample collection periods. Our results indicate that MP contamination is present in the river water, but it is noted that slightly different polymer types were found during each collection month. MPs can be transferred through the food chain and potentially to humans. Regular monitoring of MPs in the riverine system is, therefore, important, for which the findings of the present study can be used as a baseline for the number of MPs in the river water in the region.

以呼伦湖流域为例研究该区域氢氧稳定同位素在不同水体中的分布特征，并探讨氢氧稳定同位素对在该区域水文过程的指示作用.流域湖水、入湖河水、周边地下水水样的氢氧稳定同位素分析结果表明，夏季8月份湖水中的重氢氧稳定同位素比7月份的更加富集.而河水中氢氧稳定同位素在同一时间内的河流沿程上存在明显的差异，下游水体中的氢氧稳定同位素要比上游更加富集.研究区的河水和湖水的δ¹⁸OδD关系特征显示，河水和湖水的δ¹⁸OδD的关系点全部位于当地降水线的右下方，说明流域河水和湖水水体受到明显的蒸发作用.而井水的δ¹⁸OδD的关系点大都靠近当地大气降水线，说明这一区域的地下水主要是大气降水渗入地下形成.利用氢氧稳定同位素分馏过程中的氢氧稳定同位素的比率与剩余水体的关系，并在考虑湿度因子的动力分馏模拟下，计算出河水的剩余水体比例在0.85~0.96之间，而湖水的剩余水体比例在0.71~0.77之间.最后，利用氢氧稳定同位素质量平衡法对呼伦湖多年平均蒸发量进行了估算，估算的湖泊蒸发量结果与实测值相近，相对误差为5.4%，说明方法可靠.氢氧稳定同位素对于研究区域水文过程有着重要的作用，在今后呼伦湖流域水文研究中有着更加广泛的应用空间.;The aim of this paper is to analyze water stable isotopes(δD and δ¹⁸O)in Lake Hulun Basin, and to explore the indicative function of stable isotopes in hydrological cycle in this region. The analytical results of lake water, river water and well water around Lake Hulun indicate that there are temporal variations of stable isotopes in lake and river water and spatial variations in river water along the flow path. Furthermore, the relationship between δ¹⁸O and δD in lake water, river water and groundwater in Lake Hulun Basin shows the crossing points of lake and river water are located in the lower right of local meteoric water line, suggesting lake water and river water have suffered from evaporation. However, the crossing points of well water are located closely to the local meteoric water line except southwestern area (W1) around the lake, indicating all groundwater except W1 reflects a precipitation origin, and the weird high isotope values in W1 may have connections to the lake water and well water. Using the relationship between stable isotopic ratio in residual water and residual water proportion with consideration of the effect of temperature and humidity, the proportions of modern lake water and river water after evaporation are calculated as 0.85-0.96 for river water, and 0.71-0.77 for lake water. Obviously, the extent of lake water evaporation is greater than that of river water, with 4%-15% water loss for rivers and 23%-29% water loss for the lake. In addition, the annual lake water evaporation was calculated based on isotopic mass balance method, the low relative error (5.4%) compared with measured data indicates this model is appropriate to calculate water evaporation for Lake Hulun. Using stable isotope (δD and δ¹⁸O) is an essential method to study on hydrological cycle in a basin, thus stable isotope still has a wide application space in hydrological cycle in Lake Hulun Basin.

Transport of nitrogen and phosphorus from agricultural and urban landscapes to surface water bodies can cause adverse environmental impacts. The main objective of this long-term study was to quantify and compare contaminant transport in agricultural drainage water and urban stormwater runoff. We measured flow rate and contaminant concentration in stormwater runoff from Willmar, Minnesota, USA, and in drainage water from subsurface-drained fields with surface inlets, namely, Unfertilized and Fertilized Fields. Commercial fertilizer and turkey litter manure were applied to the Fertilized Field based on agronomic requirements. Results showed that the City Stormwater transported significantly higher loads per unit area of ammonium, total suspended solids (TSS), and total phosphorus (TP) than the Fertilized Field, but nitrate load was significantly lower. Nitrate load transport in drainage water from the Unfertilized Field was 58% of that from the Fertilized Field. Linear regression analysis indicated that a 1% increase in flow depth resulted in a 1.05% increase of TSS load from the City Stormwater, a 1.07% increase in nitrate load from the Fertilized Field, and a 1.11% increase in TP load from the Fertilized Field. This indicates an increase in concentration with a rise in flow depth, revealing that concentration variation was a significant factor influencing the dynamics of load transport. Further regression analysis showed the importance of targeting high flows to reduce contaminant transport. In conclusion, for watersheds similar to this one, management practices should be directed to load reduction of ammonium and TSS from urban areas, and nitrate from cropland while TP should be a target for both.

Controlled drainage‐subirrigation (CDS), conservation tillage, and corn (Zea mays L.) production practices were evaluated as methods of reducing NO−3 loss through tile drainage. Controlled drainage‐subirrigation was used to manage water from precipitation and subirrigation. Samples of tile drainage (5801) and surface runoff (3274) water were collected with autosamplers during each runoff event over a 3‐yr period. Annual tile drainage volumes were reduced 24% with CDS compared with the drainage (DR) treatments. Flow weighted mean NO−3 concentration of tile drainage water was reduced 25% from 10.6 mg N L−1 for the DR treatments to 7.9 mg N L−1 for the CDS treatments. The average annual NO−3 loss was reduced 43% from 25.8 kg N ha−1 for the DR treatment to 14.6 kg N ha−1 for the CDS treatments. Eighty‐eight to 95% of the NO−3 losses from all treatments occurred in the noncrop period (1 Nov.–31 Apr.). Conservation tillage in combination with CDS reduced annual NO−3 losses 49% (11.6 kg N ha−1) when compared with the conventional moldboard plow tillage and DR treatment. Annual NO−3 loss through surface runoff was increased to 1.9 kg N ha−1 with the CDS treatments compared with 1.4 kg N ha−1 with the DR treatment, this loss was minor compared with losses incurred through tile drainage. Controlled drainage‐subirrigation is a technological advancement in soil and water management as it enables farmers to minimize the effect of dry summers on crop growth and reduce NO−3 contamination of drainage water.

Water quality plays an important role in water resources management plans, particularly for arid and semiarid regions, where water scarcity has become a real issue. Agricultural drainage water can be reused separately/or in conjunction with fresh water. However, the water quality status of drainage water is concern in reuse implementation strategies. Moreover, the water quality degradation of natural water body that receives the drainage water can be effected. Thus, implementation of water quality treatment practices and technologies is essential. In this chapter, available drainage water treatment practices and technologies, such as controlled drainage, wetlands, bioreactors, and two-stage open ditch, will be discussed in detail. The pilot studies of implementing drainage water treatment systems in Egypt were reviewed and will be described in this chapter. It is recommended to experiment with some low-cost applicable technologies, such as in-stream control structures and treatment systems, and to implement constructed wetland treatment systems on major Egyptian drains.

Veterinary antibiotics are widely used in New Zealand and around the world to treat bacterial infections and for non‐therapeutic use as growth promoters. There is growing concern that unmetabolised antibiotics pass through stock and enter the environment, facilitating antibiotic resistance in pathogenic bacteria and harming aquatic ecosystems. Bioassay experiments showed that filtered water from an agricultural drain reduced the abundance of aquatic bacteria in Lake Waipori, a shallow coastal lake, whereas most other planktonic organisms were not inhibited. This result was consistent with the presence in the drain water of bacte‐riolytic antibiotics (e.g., penicillin). Further experiments were conducted to examine the effects of admixtures of water from the same agricultural drain both on the abundance and respiration rate of aquatic bacteria in the lake. One of four experiments showed inhibition of bacterial respiration consistent with the presence of bacteriostatic antibiotics (e.g., tetracyclines, aminoglycosides, macrolides) in the drain water. No further significant bacteriolytic effects were observed. A mixture of commonly used antibiotics was not consistently effective at reducing bacterial abundance or inhibiting bacterial respiration in lake water. Although we found evidence of antibacterial activity in the drain water this was intermittent, indicating either that antibiotic inputs to the drain were also intermittent, that other environmental factors intermittently affected the potency of antibiotics in the drain water, and/or that aquatic bacteria exhibited temporally variable resistance to antibiotics.

Modelling phosphorus removal efficiency of a reactive filter treating agricultural tile drainage water

Malathion and chlorpyrifos are pesticides used excessively for agricultural purposes in Egypt to fight insects. The presence of such toxic compounds in watercourses exhibits harmful threats to the environment. The technology of bio-removal (or biodegradation) is nowadays the alternate method for environmental curing. The present study aimed to isolate and identify microbial strains (fungi and bacteria) with strong capabilities of biodegrading such pesticides, and to evaluate their abilities to uptake both pesticides at the same time. Agricultural drainage water samples were collected from four different drains in Egypt, named; El-Rahawi drain, Giza Governorate; Sabal drain, Minufiya Governorate; Ketshiner drain, Kafr El-Shiekh Governorate and Genag drain, Gharbiya Governorate. Water quality studies were carried out for water samples including organophosphorus (OP) pesticide contamination using Gas Chromatography-Mass Spectrometry (GC-MS). Malathion and chlorpyrifos was detected in slightly high concentration in Genag drain. So, Genag drainage water was used as enrichment to isolate the microorganisms having pesticide-biodegrading abilities. A total of four fungal and two bacterial strains were isolated, all of which showed a high ability to biodegrade one or both of the pesticides. The identification of the fungal isolates was carried out by 18S rRNA sequence analysis as Aspergillus fumigatus, Aspergillus niger, Penicillium chrysogenum and Aspergillus flavus. The bacterial isolates were identified as Acinetobacter boumnnii and Pseudomonas putida using 16S rRNA sequence analysis. The results of the biodegradation – capabilities experiments indicated the promising efficiency of A. niger, P. chrysogenum and P. putida where they could remove 90.5%, 95% and 64.4% of malathion and 85.8%, 85% and 88.2% of chlorpyrifos, respectively. Also, they exhibited potential abilities in biodegrading both pesticides at once, so, we recommend the use of such microorganisms as tools for bioremediation of agricultural drainage water contaminated with pesticides.