The globalization of agricultural trade has dramatically altered global nitrogen flows by changing the spatial pattern of nitrogen utilization and emissions at a global scale. As a major trading country, China uses a large amount of nitrogen, which has a profound impact on global nitrogen flows. Using data on food production and trade between China and 26 other countries and regions, we calculated nitrogen inputs and outputs in food production ecosystem in each country. We estimated nitrogen flows in international food trade and analyzed their impact on nitrogen pollution in China. We divided nitrogen flows into embodied and virtual nitrogen flows. Embodied nitrogen is taken up by the plant and incorporated into the final food product, whereas virtual nitrogen is lost to the environment throughout the food production process and is not contained in the final food product. Our results show that China mainly imports food products from America and Asia, accounting for 95 % of all imported food. Asia (mainly Japan) and Europe are the main exporters of food from China, with Japan and the EU accounting for 17 and 10 % of all exported food, respectively. Total nitrogen inputs and outputs in food production in China were 55,400 and 61,000 Gg respectively, which were much higher than in other countries. About 1440 and 950 Gg of embodied and virtual nitrogen respectively flow into China through the food trade, mainly from food-exporting countries such as the USA, Argentina, and Brazil. Meanwhile, 177 and 160 Gg of embodied and virtual nitrogen respectively flow out of China from the export of food products, mainly to Japan. China’s net food imports have reduced 720 and 458 Gg for nitrogen utilization and outputs, respectively, which accounted for 1.3 and 0.78 % of total nitrogen inputs and outputs in China. These results suggest that food trade in China has a profound effect on nitrogen flows and has greatly reduced environmental impacts on nitrogen pollution in China.

Excess nitrogen loading has contributed to the impairment of major watersheds across North Carolina. Onsite wastewater systems (OWS) are a potential source of nitrogen to water resources, but more research is needed to determine their actual contributions, especially in the Piedmont region of the state. The objective of this study was to determine the total dissolved nitrogen (TDN) treatment efficiency of four OWS in clayey soils of the North Carolina Piedmont. Two OWS were conventional style, and two were single-pass sand filters. The four volunteered sites with OWS were instrumented with piezometers (27 total) for groundwater collection and analyses. Piezometers were installed within 1.5 m of each OWS and downgradient from the conventional OWS. Septic tank effluent, groundwater from the piezometers, sand filter effluent, and adjacent surface waters were sampled bimonthly (five times) during 2015. Samples were analyzed for TDN, NO₃ ⁻-N, NH₄ ⁺-N, chloride, dissolved organic carbon, and physical and chemical parameters on each sampling event. Groundwater samples collected 35 m downgradient from the two conventional OWSs had TDN concentrations and masses, on average, of 98 and 70 %, respectively, lower than septic tank effluent. Isotopic analysis of the natural abundance of δ¹⁵N and δ¹⁸O in NO₃ ⁻ in groundwater collected at the conventional OWS sites suggests that denitrification was a mass removal mechanism. The sand filter OWS reduced TDN concentrations by an average of 80 % and mass loading by 50 % prior to discharge to surface waters. Nitrogen management regulations in nutrient-sensitive watersheds should consider the contributions from OWS, especially direct discharge systems like sand filters. Improvements in the TDN treatment efficiency of direct discharge OWS would result in immediate surface water quality improvements.

Photocatalytic fuel cell is considered as a sustainable wastewater treatment system which could degrade organic pollutants and generate electricity simultaneously. In this study, a single-chambered photocatalytic fuel cell based on immobilized ZnO/Zn photoanode was evaluated under sunlight and UV light irradiation, respectively. Methylene blue was used as the dye pollutant in the photocatalytic fuel cell. The fabricated ZnO/Zn photoanode was characterized using scanning electron microscopy and X-ray diffraction. Significant difference in degradation efficiency of methylene blue was observed under UV and sunlight irradiation, respectively. Results showed that the decolorization efficiency and electricity generation of methylene blue in PFC and photolysis were higher under sunlight irradiation compared to those of the UV light irradiation. The decolorization trend of methylene blue was unstable under photolysis using UV light irradiation. Under sunlight irradiation, about 85% of methylene blue was decolorized by PFC, but only 35% of decolorization was observed under UV light irradiation. The maximum power density of the PFC under sunlight irradiation (0.0032 mW/cm²) was almost two times of that under the UV light irradiation (0.0017 mW/cm²).

Studies on replacement of inorganic fertilizer with organic residues to improve crop productivity and their impact on greenhouse gas emission from agricultural soil merit more attention. Two-year field experiments were conducted to study the impact of different organic residues with varied carbon (C)/nitrogen (N) ratios as substitutes of chemical fertilizer on emission reduction of nitrous oxide (N₂O) and crop yield from a tropical summer rice paddy of India. Five treatments comprising of conventional N fertilizer (NPK), cow manure (CD), rice straw (RS), poultry manure (PM), and sugarcane bagasse (SCB) were applied in a rice field to estimate N₂O emission. Application of CD (at 10 t ha⁻¹) resulted in maximum reduction of seasonal N₂O emissions (15 %) over NPK, RS, PM, and SCB. Application of CD and RS enhanced leaf photosynthetic rate and caused maximum utilization of photosynthates towards developing grains as evident from grain filling ability and higher grain yield. Substitution of NPK with organic residues enhanced soil nutrient availability in terms of C and N resulting in improved soil fertility and to some extent influenced soil nitrogen processes which in turn reduced N₂O emissions. We conclude that suitable management of soil in agricultural ecosystem can reduce the emission of N₂O and protect and preserve the soil health without compromising the agronomic productivity reducing the use of chemical fertilizer and maintaining the sustainability of rice ecosystem as evident from lower carbon equivalent emissions (CEE) and higher carbon efficiency ratio (CER) at CD in rice paddies in the present study.

Cadmium is a cumulative, chronic toxicant in humans for which the main exposure pathway is via plant foods. Cadmium-tolerant plants may be used to create healthier food products, provided that the tolerance is associated with the exclusion of Cd from the edible portion of the plant. An earlier study identified the cabbage (Brassica oleracea L.) variety, Pluto, as relatively Cd tolerant. We exposed the roots of intact, 4-week-old seedlings of Pluto to Cd (control ∼1 mg L⁻¹ treatment 500 μg L⁻¹) for 4 weeks in flowing nutrient solutions and observed plant responses. Exposure began when leaf 3 started to emerge, plants were harvested after 4 weeks of Cd exposure and the high Cd treatment affected all measured parameters. The elongation rate of leaves 4–8, but not the duration of elongation was reduced; consequently, individual leaf area was also reduced (P < 0.001) and total leaf area and dry weight were approximately halved. A/C ᵢ curves immediately before harvest showed that Cd depressed the photosynthetic capacity of the last fully expanded leaf (leaf 5). Despite such large impairments of the source and sink capacities, specific leaf weight and the partitioning of photosynthate between roots, stems and leaves were unaffected (P > 0.1). Phytochelatins (PCs) and glutathione (GSH) were present in the roots even at the lowest Cd concentration in the nutrient medium, i.e. ∼1 μg Cd L⁻¹, which would not be considered contaminated if it were a soil solution. The Cd concentration in these roots was unexpectedly high (5 mg kg⁻¹ DW) and the molar ratio of –SH (in PCs plus GSH) to Cd was large (>100:1). In these control plants, the Cd concentration in the leaves was 1.1 mg kg⁻¹ DW, and PCs were undetectable. For the high Cd treatment, the concentration of Cd in roots exceeded 680 mg kg⁻¹ DW and the molar –SH to Cd ratio fell to ∼1.5:1. For these plants, Cd flooded into the leaves (107 mg kg⁻¹ DW) where it probably induced synthesis of PCs, and the molar –SH to Cd ratio was ∼3:1. Nonetheless, this was insufficient to sequester all the Cd, as evidenced by the toxic effects on photosynthesis and growth noted above. Lastly, Cd accumulation in the leaves was associated with lowered concentrations of some trace elements, such as Zn, a combination of traits that is highly undesirable in food plants.

Open-cut mining operations can form pit lakes on mine closure. These new water bodies typically have low nutrient concentrations and may have acidic and metal-contaminated waters from acid mine drainage (AMD) causing low algal biomass and algal biodiversity. A preliminary study was carried out on an acidic coal pit lake, Lake Kepwari, in Western Australia to determine which factors limited algal biomass. Water quality was monitored to obtain baseline data. pH ranged between 3.7 and 4.1, and solute concentrations were slightly elevated to levels of brackish water. Concentrations of N were highly relative to natural lakes, although concentrations of FRP (<0.01 mg/L) and C (total C 0.7–3.7 and DOC 0.7–3.5 mg/L) were very low, and as a result, algal growth was also extremely low. Microcosm experiment was conducted to test the hypothesis that nutrient enrichment will be able to stimulate algal growth regardless of water quality. Microcosms of Lake Kepwari water were amended with N, P and C nutrients with and without sediment. Nutrient amendments under microcosm conditions could not show any significant phytoplankton growth but was able to promote benthic algal growth. P amendments without sediment showed a statistically higher mean algal biomass concentration than controls or microcosms amended with phosphorus but with sediment did. Results indicated that algal biomass in acidic pit lake (Lake Kepwari) may be limited primarily by low nutrient concentrations (especially phosphorus) and not by low pH or elevated metal concentrations. Furthermore, sediment processes may also reduce the nutrient availability.

The Mediterranean area is highly vulnerable to climate changes that combined with potential land use changes could influence its aquatic systems significantly. The Evros River is one of the most important surface water bodies in the Balkans with an ecologically significant delta that is protected by international legislation. The aim of this study is to analyze the impacts of climate and land use changes on Evros River water quality, for different climatic and socioeconomic scenarios. For this purpose, a hydrodynamic and advection-dispersion model was set up and calibrated, three IPCC climatic scenarios were applied, and the pollution loads of the catchment area were estimated. These scenarios involved river discharge decrease due to regional climate changes and socioeconomic and technological development that would lead to population growth and to the decrease of agricultural activities. The results indicated that in the case of discharge reduction only, the total nitrate and phosphate concentrations will be increased, while in case of combined land use and discharge changes, the concentration of nutrients will be decreased. Thus, a transboundary long-term management plan of the entire River is needed that would eliminate the pollution pressures and restore its good ecological status.

Anthropic eutrophication is one of the most widespread problems affecting water quality worldwide. This condition is caused by excessive nutrient inputs to aquatic systems, and one of the main consequences is accelerated phytoplankton growth. Eutrophication can lead to damage to human health, the environment, society, and the economy. One of the most serious consequences of eutrophication is the proliferation of cyanobacteria that can release toxins into the water. The aim of this research was to evaluate the trophic condition of a tropical reservoir over the course of time, using a database extending over 15 years to investigate relationships with environmental conditions, considering spatial heterogeneity and seasonality, as well as inter-relations between trophic state indicators. Data for chlorophyll-a, total phosphorus, and total nitrogen were collected from 2000 to 2014, and cyanobacteria abundance was determined from 2004 to 2014. The trophic state index was also calculated. The results demonstrated the existence of two distinct compartments in the reservoir: one lotic and the other lentic. No relationship was observed between chlorophyll-a and phosphorus. The results suggested that phytoplankton growth was mainly controlled by nitrogen concentrations. These conditions favored cyanobacteria predominance, resulting in increasing abundance of these potentially toxic bacteria over time. The model obtained indicated hypereutrophic conditions, with high phytoplankton biomass and cyanobacteria abundance during the next years likely to affect the uses of the water of the reservoir.

For the purpose of clarifying the chemical nature of fly ashes, the raw fly ashes were collected from the stacks of 17 fixed sources consisting of 15 municipal waste incinerators, a metal melting factory, and a cement plant all of which are located in the western Japan from Nov. 2000 to Jan. 2007. The municipal waste incinerators were successfully classified into four groups in terms of the relative mass ratios between chloride, potassium, and sodium. Sodium, potassium, and calcium were found abundantly in fly ashes collected from all four types of municipal waste incinerators. The theoretical estimation of chlorine form suggested that the form of NaCI, KCl, MgCl, and CaCl₂ accounted for approximately 55 % of total chlorine in raw fly ash. Trace heavy metals (i.e., Zn, Mn, Pb, Cu, Cr, Ni, and V) were preferentially enriched in the ambient PM₂.₅ which was strongly influenced by regional stationary sources (including municipal waste incinerators). The water-soluble OC to TC fraction in the fly ashes of municipal waste incinerator, metal furnace, and cement plant was estimated as 56.8, 79.0, and 89.6 %, respectively.

Although 8-hydroxy-2-deoxyguanosine (8-OHdG) is a widely used promising biomarker of DNA damage, there are concerns about which tissues or body fluids should be sampled. The objective of this study is to evaluate the correlation of DNA oxidative damage biomarkers, 8-OHdG, between blood and urine and risk factors associated with 8OHdG. The study population was recruited from a baseline survey of a worksite lifestyle study including 92 office workers aged 23 to 60 years. A self-administered questionnaire was used to collect information on personal characteristics. The plasma and urinary 8-OHdG was measured by liquid chromatography tandem mass spectrometry (LC-MS/MS). In linear regression, a positive relation was found (p < 0.01) between the log-transformed plasma and urinary 8-OHdG levels adjusted for gender, age, BMI, and smoking status. Our findings showed that age, gender and smoking were significantly associated with plasma 8-OHdG, but not with urinary 8-OHdG. Our results suggest that there is a positive relation between the biomarkers of plasma (steady state DNA damage) and urinary 8-OHdG (total DNA damage). However, the plasma 8-OHdG is more sensitive than urinary 8-OHdG to detect increased oxidative damages induced by risk factors.