Groundwater nitrate pollution and human health risk assessment by using HHRA model in an agricultural area, NE China

Freshwater environments as reservoirs of antibiotic resistant bacteria and their role in the dissemination of antibiotic resistance genes

Groundwater is critical for the sustainable development of the Loess Plateau, while groundwater quality is generally poor in this area due to natural factors and anthropogenic pollution. This study was carried out to investigate the suitability of groundwater for domestic and agricultural purposes in Yan’an City on the Chinese Loess Plateau and to assess its implications to sustainable groundwater management on the plateau. The index levels were compared with the threshold values established by the national and the WHO drinking water guidelines, and the suitability of groundwater for irrigation purposes was assessed using multiple agricultural water quality indicators. An entropy-weighted Technique for Order Preference by Similarity to an Ideal Solution (entropy-weighted TOPSIS) was adopted for overall groundwater quality assessment. The results indicate that the study area is characterized by saline, hard, and slightly alkaline groundwater, mainly of the HCO3–Ca·Mg type, accompanied by some minor SO4·Cl–Ca·Mg type. The dissolution of carbonates and gypsum and the leaching of soluble salts are important natural processes influencing the groundwater ion chemistry. The parameters TH, TDS, and SO42− are major indices, while Fe, Mn, F−, and NH4+ are minor contaminants affecting groundwater quality. The overall groundwater quality is generally acceptable for irrigation, and most of the water is suitable for drinking. Rainwater harvesting, water quality improvement programs, regular water quality monitoring, and multidisciplinary water research programs are suggested as measures for sustainable groundwater management on the Loess Plateau.

Groundwater quality assessment for domestic and agricultural purposes in Yan’an City, northwest China: implications to sustainable groundwater quality management on the Loess Plateau

Groundwater is the only water source in the Siddipeta-Vagu (SDV) region, India, and its quality is vital as it is the primary factor determining the groundwater suitability for drinking and irrigat...

Groundwater quality and associated health risks in a semi-arid region of south India: Implication to sustainable groundwater management

The deep challenge of nitrate pollution in river water of China

This study aims to investigate the physical and chemical effects of interactions between groundwater and surface water (GW–SW)—particularly in streams—on nitrate contamination. The effects of GW–SW interactions are briefly reviewed, with a particular emphasis on processes and environments that influence increases or decreases in nitrate concentration. Then, this paper analyses nitrate concentrations in groundwater and surface water in the western Po plain (Northwestern Italy); this analysis includes the nitrate concentration profiles across the shallow aquifer and intersecting the main streams on the plain. The investigation highlights how the concentration trends are similar, even when nitrate levels in rivers and groundwater are not comparable. The maximum nitrate concentrations in the surface water were generally measured in areas with high-nitrate levels in groundwater. An analysis of the nitrate concentration profiles highlighted the mutual influences of GW–SW. The most important streams on the plain (the Po River and Stura di Demonte River), both of them gaining streams, seem to reduce the nitrate concentrations of groundwater at a study scale. The proposed conceptual model indicates how the near-stream environment (the riparian zone, wetlands, hyporheic zone and shallow organic-rich soils in the near-stream environment) and the groundwater flow systems in shallow and deep aquifers, from the recharge zone to the streams, could dramatically affect the nitrate concentrations.

Nitrate contamination of groundwater in the western Po Plain (Italy): the effects of groundwater and surface water interactions

Currently, diffuse pollution by nitrate is considered one of the main causes of groundwater quality deterioration. Many methodologies have been suggested to map aquifer vulnerability to nitrate pollution; however, no standard method has yet been established. Many proposed methods only take into account the aquifer’s protection and do not consider the physical or chemical processes in groundwater. More specifically, recent studies indicate that the fate and concentration of nitrates in aquifers mainly depend on the following: (a) the efficiency of natural attenuation (e.g. biological denitrification), (b) the physical processes of attenuation (e.g. dilution). Both the processes can lower the nitrate levels in groundwater. The aim of this research is to describe the features and role of these processes in aquifers. According to previous studies and our results, dilution and denitrification occurring in aquifers have a key role in the attenuation of nitrate. More specifically, the occurrence and effectiveness of denitrification were evaluated in a plain area in NW Italy through nitrogen isotopic fractionation analysis; the volumetric flow rate per unit width perpendicular to the flow direction, which is a function of the hydraulic gradient, hydraulic conductivity and aquifer thickness, was instead used for the assessment of nitrate attenuation capacity by means of the dilution process. Knowledge and understanding of these processes is essential to the identification of areas where groundwater is more prone to contamination. Thus, the evaluation of groundwater vulnerability to nitrate contamination cannot be separated from the comprehension of these processes.

The role of physical and biological processes in aquifers and their importance on groundwater vulnerability to nitrate pollution

The concept of aquifer vulnerability is certainly useful in the field of groundwater protection. Nevertheless, within the scientific community, the definition of vulnerability is still under debate and lacks standardisation. As a consequence, the methods for evaluating the vulnerability degree are numerous and often lead to conflicting results. Thus, in this study, three methods that are commonly used in groundwater vulnerability assessments due to their easy application (namely DRASTIC, GOD and TOT) were utilised in four areas of the Piedmont region (NW Italy). The results obtained by the different methods were compared and correlated with the nitrate concentrations in the groundwater. The aims of the study were (i) to evaluate the effectiveness of the adopted methods and their comparability, (ii) to discuss the limits of the intrinsic vulnerability methods and (iii) to verify the applicability of nitrate as a tracer in the assessment of groundwater vulnerability or explain the reasons why it is not applicable. It was observed that the three intrinsic vulnerability methods are not able to uniquely identify the most or least vulnerable areas. Additionally, the comparison of the intrinsic vulnerability indexes only occasionally showed a reasonable correlation. Furthermore, there was no clear correlation between the vulnerability indexes and nitrate concentrations in the groundwater. These results could be explained by several reasons: (1) the methods are mostly based on the level of groundwater protection provided by the overlaying lithologies and do not consider the physical processes occurring in the aquifer; (2) the intrinsic vulnerability methods only consider vertical pathways for contaminants, but a pre-existing contaminant could be present in the aquifer; (3) groundwater nitrate concentrations are affected by the nitrate input and surplus; and (4) nitrates are subject to physical and biological attenuation in aquifers and cannot necessarily be considered stable tracers in the assessment of groundwater vulnerability.

Intrinsic groundwater vulnerability assessment: issues, comparison of different methodologies and correlation with nitrate concentrations in NW Italy

Several areas in Piedmont plain (North-Western Italy) are characterized by nitrate concentrations higher than 50 mg/L, the maximum nitrate concentration accepted by Italian law. The Piedmont plain sector is the most important water reservoir of the Piedmont Region, due to its size, the characteristics of its deposits and the possibility of recharge. In the Piedmont plain groundwater, the origin of nitrate contamination is due to the increasing amount of synthetic nitrogenous fertilizers and organic manure used for agricultural purposes but also to septic tank effluents input. Univariate and bivariate statistics and concentration maps were used to describe the distribution of nitrate in Piedmont plain, both in shallow and in deep aquifers, to highlight the variation of nitrate levels from year 2000 to 2012 and to analyse the relation of nitrate versus well depth. The purpose is to create the basis for future investigations and insights about the nitrate sources and the attenuation processes in aquifers.

Elisa Franchino

Papers

Nitrate contamination of groundwater in the western Po Plain (Italy): the effects of groundwater and surface water interactions

The role of physical and biological processes in aquifers and their importance on groundwater vulnerability to nitrate pollution

Intrinsic groundwater vulnerability assessment: issues, comparison of different methodologies and correlation with nitrate concentrations in NW Italy

Areal and Vertical Distribution of Nitrate Concentration in Piedmont Plain Aquifers (North-Western Italy)

Groundwater chemistry characterization using multi-criteria approach: The upper Samala River basin (SW Guatemala)