National Drinking Water Standards Research Articles

Arsenic and fluoride in groundwater triggering a high risk: Probabilistic results using Monte Carlo simulation and species sensitivity distribution

The widespread presence of arsenic (As) and fluoride (F−) in groundwater poses substantial risks to human health on a global scale. These elements have been identified as the most prevalent geogenic contaminants in groundwater in northern Mexico. Consequently, this study aimed to evaluate the human health and ecological risks associated with the content of As and F− in the Meoqui-Delicias aquifer, which is in one of Mexico's most emblematic irrigation districts. Concentrations of As and F− were measured in 38 groundwater samples using ICP-MS and ion chromatography, respectively. Overall, these elements showed a similar trend across the aquifer, revealing a positive correlation between them and pH. The concentration of As and F− in the groundwater ranged from 5.3 μg/L to 303 μg/L and from 0.5 mg/L to 8.8 mg/L, respectively. Additionally, the levels of As and F− surpassed the established national standards for safe drinking water in 92% and 97% of samples, respectively. Given that groundwater is used for both agricultural purposes and human activities, this study also assessed the associated human health and ecological risks posed by these elements using Monte Carlo simulation and Species Sensitivity Distribution. The findings disclosed a significant noncarcinogenic health risk associated with exposure to As and F−, as well as an unacceptable carcinogenic health risk to As through water consumption for both adults and children. Furthermore, a high ecological risk to aquatic species was identified for F− and high to medium risks for As in the sampling sites. Therefore, the findings in this study provide valuable information for Mexican authorities and international organizations (e.g., WHO) about the adverse effects that any exposure without treatment to groundwater from this region represents for human health.

Annual atrazine residue estimation in Chinese agricultural soils by integrated modeling of machine learning and mechanism-based models

This study presents a comprehensive approach to estimating annual atrazine residues in China's agricultural soils, integrating machine learning algorithms and mechanism-based models. First, machine learning was used to predict essential parameters influencing atrazine's adsorption, degradation, and dispersivity of solute transport. The results demonstrated that soil organic matter was the most important input variable for predicting adsorption and degradation; clay content was the primary variable for predicting dispersivity. The SHapley Additive exPlanations (SHAP) contribution of various soil properties on target variables were also analyzed to reveal whether each input variable has a positive, negative, or complex effect. Subsequently, these parameters inform the construction of a detailed model across 23,692 subregions of China, with a 20 km × 20 km resolution. The model considered regional variations and soil layer heterogeneity, including rainfall, soil depth-specific properties, and parameters for adsorption, degradation, and dispersivity. Utilizing the convection-dispersion equations and the Phydrus, the model simulated atrazine's transport and degradation patterns across diverse soil environments after applying 250 mL of atrazine (40%) per Chinese mu. The outcomes provided a spatially explicit distribution of atrazine residues, specifying that the arid areas have the highest residual risk, followed by the Northeast, Southwest, and Southeast. Atrazine levels may exceed national drinking water standards at 50 cm depth in Inner Mongolia, the Qinghai-Tibet Plateau, and the Jungar Basin. This study's integrative approach may also offer valuable insights and tools for evaluating residues of various pesticides and herbicides in agricultural soils.

Application of bioassays and physicochemical analysis for assessing groundwater quality of selected tube wells in a CKDu impacted area

Groundwater from tube and dug wells are primarily used for drinking purposes by rural communities inhabiting Chronic Kidney Disease of unknown aetiology (CKDu) impacted areas in Sri Lanka. Groundwater safety assessment using targeted physicochemical analysis alone is not adequate to capture interactive effects of chemical mixtures in the groundwater. This study explored for the first time combined use of physicochemical analysis and bioassays with root meristems of Allium cepa and erythrocytes of Cyprinus carpio to assess groundwater quality of selected tube wells in Medawachchiya (a CKDu impacted area), Sri Lanka covering pre-monsoon, monsoon and postmonsoon seasons. The pH, turbidity, arsenic, cadmium, lead, mercury, fluoride, chloride, nitrate and nitrite levels in the groundwater complied with Sri Lanka standards for potable drinking water in all seasons. Yet, alkalinity and total hardness levels in the groundwater exceeded national drinking water standards (nearly up to two folds) mostly in the monsoon season. Bioassays revealed genotoxic effects of the groundwater of some tube wells in pre-monsoon and monsoon seasons. Observed genotoxicity may be associated with synergistic effects of contaminants including undetected and unknown chemicals in the groundwater depending on the season. The results support the use of bioassays as complementary tools for evaluating groundwater quality of CKDu hotspots considering consumer safety.

Fluorescent bacterial cellulose@Zr-MOF via in-situ synthesis for efficient enrichment and sensitive detection of Cr(VI)

In this study, for the first time, a new Zr-metal–organic framework (MOF) with strong aggregation-induced emission was successfully grown on bacterial cellulose (BC) using an in situ synthesis method, yielding the fluorescent composite nanofiber BC@Zr-MOF. The BC with abundant hydroxyl groups, which can be uniformly wrapped in the interior of the MOF layer to form BC@Zr-MOF, was used as the growth template. The resulting composite nanofibers had a higher specific surface area (1, 116 m2/g), stronger fluorescence emission and better pH stability than MOF particles. In addition, BC@Zr-MOF exhibited selective recognition and enrichment of Cr2O72− in the aqueous phase and a high adsorption capacity of 90 mg/g. Moreover, because of the high aspect ratio and good tensile strength (6.73 N/mm2), BC@Zr-MOF nanofibers could be readily made into freestanding nanopapers via vacuum filtration, thus solving the molding and recycling problems of MOFs. The facilely prepared test paper could rapidly, sensitively and selectively detect Cr2O72− with the limit of detection (LOD) of 41.8 nM, which is nearly 500 times lower than that of the national drinking water standard. Moreover, the LOD of BC@Zr-MOF nanopapers, when used in combination with circulating filtration, decreases to 6.9 nM owing to the adsorption-enrichment effect.

A comprehensive survey and analysis of international drinking water regulations for inorganic chemicals with comparisons to the World Health Organization's drinking-water guidelines.

The World Health Organization (WHO) has published criteria for determining the quality of drinking water since 1958. Since 1984, these criteria were termed "guidelines" to emphasize that they are not national standards, but rather guidelines for nations to develop their own national standards, which may take into account local environmental, social, economic, and cultural conditions. When calculating guideline values (GVs), the WHO reviews the toxicological literature, calculates a health-based value (HBV), and determines whether the HBV should be adopted as a GV. The WHO also considers aesthetic aspects of drinking water quality, such as taste and the staining of plumbing fixtures, and additionally supplies aesthetic values (AVs) for certain drinking water contaminants. There is no central registry for national drinking water standards, so the degree of variation of national drinking water standards is not known. We examined standards, guidelines, and background documents for all inorganic contaminants published by the WHO from 1958-2022. We also searched for national drinking water standards for all independent countries. We found the WHO currently has 16 GVs, six HBVs without GVs, and six AVs without HBVs or GVs for inorganic drinking water contaminants, excluding disinfection agents and their byproducts. More than half of the point of departure studies used to support these values were published in 2005 or earlier. Ninety-eight percent of the world's population lives in jurisdictions with drinking water standards, and 14 countries directly link their national standards to the current WHO's drinking water guidelines. Lack of transparency (standards available only through purchase) and typographical errors are common problems, especially for resource-limited countries. The WHO drinking water guidelines are crucially important for drinking water safety; they are used for guidance or as official standards throughout the world. It is crucial that they be based on the best available science.

Use of Extracted Proteins from Oak Leaves as Bio-Coagulant for Water and Wastewater Treatment: Optimization by a Fractional Factorial Design

The present work sheds light on the potentiality of proteins extracted from oak (Quercus robur) leaves to treat both drinking water and industrial oily wastewater. The work was structured in three steps: firstly, oak leaves in powder form were analyzed by FTIR, XRD and SEM, thus showing the presence of proteins acting as bio-coagulants; secondly, an experimental design was conducted. According to the design of experiences based on fractional design (28−4), the highest protein concentration (4.895 mg/g) was obtained for the following operating parameters: no filtration, pH of 12, temperature of 20 °C, stirring speed of 300 rpm, stirring time of 60 min, maceration time of 4 h, centrifugation speed of 400 rpm, centrifugation time of 10 min. Finally, a jar test apparatus was used to study the effects of proteins from oak leaves on the characteristics of both drinking water and industrial oily wastewater. In drinking water, the turbidity was reduced from 15.7 to 4.82 NTU when 0.098 mg/L of oak leaves protein was added, thus satisfying the requirements of the national drinking water standards; whereas, in industrial oily wastewater turbidity, total suspended solids, chemical oxygen demand and organic matter were reduced by 96.87, 89.86, 96.39 and 46.28%, respectively, when 0.538 mg/L of oak leaves protein was added. This study opens new perspectives related to the research and development of organic coagulants applicable to industrial wastewater treatment.

Assessment of heavy metal content in groundwaters of Ikpe Community, Akwa Ibom State, Niger Delta, Nigeria

Accumulation of heavy metals in groundwater system could portend adverse health consequences to users. Heavy metal content of five randomly selected hand dug wells in Ikpe community, Akwa Ibom State, Nigeria was assessed between April and November 2022. The water was evaluated using standard methods and water quality indices to determine its suitability for human consumption. Eight heavy metals were evaluated using Heavy metal Pollution Index (HPI) and Comprehensive Pollution Index (CPI). The results were compared with the National drinking water standard. Results showed that chromium ranged from 0.001 to 0.20 mg/L, cadmium (0.001 - 0.008 mg/L), nickel (0.01- 0.08 mg/L), manganese (0.001- 0.6 mg/L), zinc (0.36 -1.90 mg/L), iron (0.1 - 0.8 mg/L), lead (0.001 - 0.02 mg/L) and arsenic (0.00 - 0.004 mg/L). HPI and CPI ranged between 44.62-126.30 and 0.18-1.33, respectively. Concentrations of these heavy metals exceeded acceptable limits, except lead and arsenic. The concentration of the metals from wells 2, 4 and 5 were generally higher and/or had values that exceeded acceptable limits. This could be attributed with geogenic and anthropogenic influences as well as the general conditions of the wells and their environment. The water quality indices (HPI and CPI) showed varying levels of heavy metal pollution in line with the heavy metal concentrations. Consequently, it can be concluded that water from wells 2, 4 and 5 is not suitable for human consumption, and it can be used for other purposes.

Assessment of Bacterial Contamination in Drinking water of Schools of Tokha Municipality, Kathmandu

Assessment of drinking water quality is being crucial especially in school institutions since children spend most of the time in school premises. The aim of this study was to assess bacterial contamination of the selected schools of Tokha Municipality. Total of 17 water samples from Ward 1, 2 and 3 were sampled and membrane filtration (MF) technique was used to analyses total coliform and fecal coliform incubated for 37 °C and 44 °C respectively. Multiple drinking water sources were found in the study area such as natural springs, piped-line system, bottled water and private wells. Almost all of the water samples exceeded WHO guideline and National Drinking Water Standards which implied none of the water samples are safe for drinking. Very few schools were found to adopt purification measures while other used to supply directly. Water samples of school were even not tested once in many schools for microbial analysis. Therefore, school management need to be responsible in coming days to ensure safe drinking water not just for children, for the wellbeing of the society and Nation.

Spatial distribution, source apportionment and health risk assessment of inorganic pollutants of surface water and groundwater in the southern margin of Junggar Basin, Xinjiang, China

Surface water (SW) and groundwater (GW) are crucial water supply sources in the southern margin of Junggar Basin in Xinjiang. The sources of toxic components in SW and GW and their negative effects on human health are of great concern. A total of 40 SW and 596 GW samples were collected at the oasis belt to analyze distribution, sources and potential health risks of inorganic pollutants in SW and GW. Results revealed that SW quality was severely affected by Hg, 30.0% of which had Hg concentration greater than the national drinking water standard. High Hg SW was mainly distributed near Manas County and Urumqi City. GW quality was mostly affected by SO42−, 24.7% of which had SO42− concentration greater than the national drinking water standard. High SO42− GW primarily occurred in the northwest and middle of the study area. Source apportionment of inorganic pollutants identified geological background, municipal wastewater disposal, water-rock interaction, geological environment, geological structure and industrial emission were the prominent potential sources of inorganic pollution in SW, with contribution rates of 1.2%, 10.0%, 43.6%, 35.1%, 6.3% and 3.8%, respectively. Five potential pollution sources in GW (including geological background, municipal wastewater disposal, water-rock interaction, geological environment and aquifer burial depth) were identified, with contribution rates of 0.7%, 9.6%, 77.6%, 11.1% and 1.0%, respectively. Probabilistic health risk assessment showed that Cl− and As in SW and GW were the main inorganic pollutants threatening human health. Non-carcinogenic risks for adults and children were negligible, while carcinogenic risks cannot be negligible. Furthermore, the contribution of potential pollution sources to health risks was quantified using positive matrix factorization coupling with health risk assessment model. Based on which, we offered the suggestion that water quality improvement in contaminated areas should be implemented in combination with pollution monitoring systems.

Assessing the efficiency of drinking water treatment plant and the impact of broken distribution systems on water quality of Wukari-Ibi plant

Water treatment is essential in the provision of potable drinking water to communities. However, studies have shown that many local conventional drinking water treatment plants in Nigeria are ineffective in removing contaminants. This study evaluated the efficiency of drinking water from Wukari-Ibi plant by assessing water samples before and after treatment and comparing results to national and international drinking water standards. Forty water samples were collected and selected physical and biological parameters were determined according to standard laboratory procedures. The results indicated that after treatment, turbidity (6.74 NTU) and coliform count (17 cfu/100 mL) were still significantly greater than standard guidelines, which suggest that the treatment plant is unable to reduce the concentration of these contaminants to a safe level for consumption. Furthermore, assessing water at consumer taps indicated that broken distribution system is likely serving as a potential pathway for contamination. The plant removal efficiency of colour, turbidity, Total Dissolved Solids, hardness, and coliform count was computed as 74.7%, 66.57%, 32.58%, 30.11%, and 59.88% respectively. Overall, the removal efficiency was 52.77% which is considered unacceptable for the supply of potable drinking water. The study concludes that cost and poor skilled personnel are the major factors in the inefficient treatment and therefore we suggest a low-cost treatment using activated carbon from locally sourced plants to be incorporated for effective removal of contaminants. There is also a need for government to invest in infrastructure and equipment so as to upgrade the treatment plant.

Competition-Induced Binding Spherical Nucleic AcidFluorescence Amplifier for the Detection of Di (2-ethylhexyl) Phthalate in the Aquatic Environment.

Di-2-ethylhexyl phthalate (DEHP) is a toxic plasticizer and androgen antagonist. Its accumulation in water exceeds national drinking water standards and it must be continuously and effectively regulated. Currently, methods used to detect DEHP are still unsatisfactory because they usually have limited detection sensitivity and require complex operating procedures. A competition-induced fluorescence detection method was developed for the selective detection of DEHP in an aquatic environment. An aptamer with walking function was used as the recognition element for DEHP, and its quantification was induced by competition to change the fluorescence signal. The detection range was 0.01~100 µg/L, and the detection limit was 1.008 μg/L. This high-sensitivity DEHP detection capability and simplified process facilitates real-time fields and other monitoring tasks.

Delineation of Groundwater Salinity Zones in Shefa and Malampa Provinces, Vanuatu

A preliminary assessment was carried out in identifying the salinity zones due to considerable concern over salty groundwater resources in Vanuatu’s Shefa and Malampa regions. Electrical conductivity (EC) and pH were measured on the islands of Efate, Lamen, and Nguna in Shefa province, as well as the islands of Ambrym and Paama in Malampa province. Thirty-four percent of the samples exceeded Vanuatu’s National Drinking Water Standards with an average of 3123 μS/Cm indicating possible salinity zones. Whereas the average pH of 7.21 was in the range of acceptable levels. EC values as high as 18,520 μS/cm indicate groundwater in some locations are unfit for drinking. The average Total Dissolved Solids (TDS) of 1717 mg.L-1 is also indicating non-compliance with standards. Salinity zone maps were developed based on the observations. Further detailed studies need to be conducted to ascertain the factors that influence groundwater salinity, such as geology, island type, and seasonality.

Arsenic in drinking water: An analysis of global drinking water regulations and recommendations for updates to protect public health.

Evidence-based public health policy often comes years or decades after the underlying scientific breakthrough. The World Health Organization's (WHO's) provisional 10 μg/L arsenic (As) drinking water guideline was set in 1993 based on "analytical achievability." In 2011, an additional proviso of "treatment performance" was added; a health-based risk assessment would lead to a lower and more protective guideline. Since the WHO does not require United Nations member states to submit copies of national drinking water regulations, there is no complete database of national drinking water standards or guidelines. In this study, we collated and analyzed all drinking water regulations for As from national governments worldwide. We found regulations for 176 countries. Of these countries, 136 have drinking water regulations that specify 10 μg/L As or less, while 40 have regulations that allow more than 10 μg/L of As; we could not find any evidence of regulations for 19 countries. The number of people living in countries that do not meet the WHO's guideline constitutes 32% of the global population. Global As regulations are also strongly tied to national income, with high income countries more likely to meet the WHO's guideline. In this study, we examined the health risk assessments that show a clear need for reducing As exposure to levels far below the current WHO provisional guideline. We also show that advances in analytical chemistry, drinking water treatment, and the possibility of accessing alternative drinking water supplies without As suggest that both low-income countries with limited resources and high-income countries with adequate resources can adopt a lower and more protective national drinking water standards or guidelines for As. Thus, we recommend that regulators and stake holders of all nations reassess the possibilities for improving public health and reducing health care expenses by adopting more stringent regulations for As in drinking water.

Community-Based Monitoring Detects Sources and Risks of Mining-Related Water Pollution in Zimbabwe

Although mining and mineral processing are vital for many economies in the Global South, they are associated with enormous challenges of managing potentially devastating environmental impacts. In contexts where environmental oversight agencies often lack financial and personal capacities to fulfill their role, community-based monitoring might be a valid alternative to monitor potential environmental impacts. In this study, we present the setup and the implementation of a citizen science project to monitor water quality parameters in a river downstream of a coal mining area in Hwange, Western Zimbabwe. In a joint effort over 1.5 years, community monitors and scientists took close to 800 water samples in the Deka River and effluent channels. The data allowed identifying sources of pollution and relating these to past and present mining activities. The primary source of acid mine drainage came from abandoned underground mine sites. Illegal mine water dumping from active mine sites accentuated the problem and resulted in fish kills and food risks for the local population. Concentrations of manganese, nickel and arsenic were exceeding national fresh water guidelines and international drinking water standards. Manganese concentrations exceeded guidelines by a factor of 70 resulting in a public health risk. In this study, we showed that community-based monitoring offers a promising approach to establish a high-quality dataset for assessing mining-related risks if the implementation of sampling protocols is followed tightly. The monitoring scheme significantly improves the collection and interpretation of water quality data in challenging contexts where governmental institutions and industrial players are not enforcing environmental standards.

Comparative Analysis of Direct Drinking Water and the Relevant Sanitation Standards in China

Along with the economic and technological development and growing demand for high-quality drinking water, direct drinking water has gained general popularity in China. However, no authoritative policy has been issued, giving a clear definition of direct drinking water and existing standards and regulations concerning direct drinking water are not definitive in nature. Existing water quality parameters are not well supported and sometimes even contradict each other. We elaborated, in this paper, the history of direct drinking water in China and systematically reviewed the existing regulations and standards related to direct drinking water. We also compared and analyzed the important microbiology, toxicology, sensory perception and general chemistry parameters in the standards. This paper is the first ever attempt at an in-depth analysis of the chaotic state of the direct drinking water industry. We have also highlighted the problems in the current standards and regulations for direct drinking water. Our study provides a basis for market regulation and the supervision and management of direct drinking water. In addition, the paper provides helpful information for laying down a definition of direct drinking water, calling for and approving of project proposals concerning the establishment of national standards for direct drinking water, and actually formulating the standards. We have made a number of suggestions: A. defining direct drinking water clearly and formulating the national standards for direct drinking water as soon as possible; B. conducting research on water quality benchmarks to provide scientific support for the formulation of the national standards for direct drinking water; C. giving more attention to the formulation of standards concerning microbiology parameters and their limits and giving consideration to the inclusion of parameters concerning viruses.

Eco-Friendly Coagulant versus Industrially Used Coagulants: Identification of Their Coagulation Performance, Mechanism and Optimization in Water Treatment Process.

The evaluation of complex organic and inorganic coagulant’s performances and their relationships could compromise the surface water treatment process time and its efficiency. In this work, process optimization was investigated by comparing an eco-friendly chitosan with the industrially used coagulants namely aluminum sulfate (alum), polyaluminum chloride (PAC), and aluminum chlorohydrate (ACH) in compliance with national drinking water standards. To treat various water samples from different treatment plants with turbidity and pH ranges from 20–826.3 NTU and 5.21–6.80, respectively, 5–20 mg/L coagulant dosages were varied in the presence of aluminum, ferum, and manganese. Among all, 10 mg/L of the respective ACH and chitosan demonstrated 97% and 99% turbidity removal in addition to the removal of the metals that complies with the referred standard. However, chitosan owes fewer sensitive responses (turbidity and residual metal) with the change in its input factors (dosage and pH), especially in acidic conditions. This finding suggested its beneficial role to be used under the non-critical dosage monitoring. Meanwhile, ACH was found to perform better than chitosan only at pH > 7.4 with half dosage required. In summary, chitosan and ACH could perform equally at a different set of optimum conditions. This optimization study offers precise selections of coagulants for a practical water treatment operation.

The challenges of monitoring and controlling drinking-water quality in dispersed rural areas: a case study based on two settlements in the Colombian Caribbean.

Water quality surveillance systems are hardly applied in rural contexts. To provide a comprehensive analysis of drinking-water quality in two rural settlements in the Colombian Caribbean drinking-water samples were collected and analyzed from storage containers in 42 homes. The results of physical, chemical, and microbiological analyses of the water samples were compared with values established by the World Health Organization (WHO) Guidelines for Drinking-water Quality, and Colombian regulations. The Kruskal-Wallis test was applied to compare each parameter for supply source, season (rainy or dry), settlement, and types of storage. Drinking-water Quality Risk Index (IRCA) was calculated for each of the samples. The water supply sources were varied: well (33.3%), rainwater (23.8%), artificial pond (23.8%), and river (19.0%). One-hundred percent of the samples contained Escherichia coli and total coliforms. The IRCA varied between 57.3 and 83.9, with a median of 72.9. Eighty-eight percent of the samples exhibited high risk levels (35.1 < IRCA < 80.0) and 12% were unsanitary (80.1 < IRCA < 100.0). Artificial pond water was the source of supply with the worst IRCA (83.79). Drinking water in the El Cascajo and La Delfina settlements does not meet international and national drinking-water standards. A change is required whereby monitoring and quality control policies take into account the reality of rural settings.

Validation of large-volume batch solar reactors for the treatment of rainwater in field trials in sub-Saharan Africa

The efficiency of two large-volume batch solar reactors [Prototype I (140 L) and II (88 L)] in treating rainwater on-site in a local informal settlement and farming community was assessed. Untreated [Tank 1 and Tank 2-(First-flush)] and treated (Prototype I and II) tank water samples were routinely collected from each site and all the measured physico-chemical parameters (e.g. pH and turbidity, amongst others), anions (e.g. sulphate and chloride, amongst others) and cations (e.g. iron and lead, amongst others) were within national and international drinking water guidelines limits. Culture-based analysis indicated that Escherichia coli, total and faecal coliforms, enterococci and heterotrophic bacteria counts exceeded drinking water guideline limits in 61%, 100%, 45%, 24% and 100% of the untreated tank water samples collected from both sites. However, an 8 hour solar exposure treatment for both solar reactors was sufficient to reduce these indicator organisms to within national and international drinking water standards, with the exception of the heterotrophic bacteria which exceeded the drinking water standard limit in 43% of the samples treated with the Prototype I reactor (1 log reduction). Molecular viability analysis subsequently indicated that mean overall reductions of 75% and 74% were obtained for the analysed indicator organisms (E. coli and enterococci spp.) and opportunistic pathogens (Klebsiella spp., Legionella spp., Pseudomonas spp., Salmonella spp. and Cryptosporidium spp. oocysts) in the Prototype I and II solar reactors, respectively. The large-volume batch solar reactor prototypes could thus effectively provide four (88 L Prototype II) to seven (144 L Prototype I) people on a daily basis with the basic water requirement for human activities (20 L). Additionally, a generic Water Safety Plan was developed to aid practitioners in identifying risks and implement remedial actions in this type of installation in order to ensure the safety of the treated water.

Municipal plastic recycling at two areas in China and heavy metal leachability of plastic in municipal solid waste

The total plastic waste generation in China has not been reported due to a lack of information on diverted recyclable wastes. This study was conducted with two objectives: to identify the characteristics of plastic waste generation, recycling, and compositions in informal and formal waste management sectors in selected Shenzhen (SZ) and Honghuatao Town (HT) study areas in China and to measure the leachability of the heavy metals of waste plastics using the synthetic precipitation leaching procedure (SPLP) and leaching tests with different pHs. The results showed that film plastic waste occupied the largest proportion among plastic components in the mixed MSW. It is estimated that the plastic waste generation rates in SZ and HT were 0.20–0.33 kg/capita/day and 0.08–0.14 kg/capita/day, respectively. The plastic recycling rates of SZ and HT ranged from 6.24 to 11.93% and 16.84–33.31%, respectively. Among the measured heavy metals, Ba, Zn, Cu, Mn contents were high in most plastic samples. In addition, Mn, Pb, Ni, and Zn in plastic wastes occasionally exceeded Chinese national drinking water standards in the different pH leaching tests and SPLP. Therefore, it is suggested that plastic waste should be managed in a controlled manner.

Analysis of Nitrate Pollution Sources in the Rainy Season of the Lower Fenhe River

Through the application of multi-isotope tracing, IsoSource model calculation, and microbial detection, the source of nitrate pollution in the lower reaches of the Fenhe River was screened, and the contribution rate of each source was calculated. The results showed that the main forms of nitrogen-containing substances in the lower reaches of the Fenhe River are NO3--N and NH4+-N and that the NO3--N content in 77.8% of the samples exceed the national drinking water standard. The abundance of denitrifying microorganisms in Jishan, Hejin, and the Fenhe River into the Yellow River is high, and many dominant bacteria participate in denitrification, resulting in nitrogen fractionation. The contents of δ15N-NO3- and δ18O-NO3- in the isotopes ranged from 5.30‰ to 12.90‰ and from 1.3‰ to 1.8‰, respectively. Manure and sewage were the main sources of nitrate in the Linfen section, accounting for 68% of the total nitrate source. In the Xiangfen section, the main sources of nitrate in the river were manure and sewage, at 37.5%, and agricultural fertilizer, at 37%. Agrochemicals are the main sources of nitrate in the Hejin section of the river, with a contribution ratio of 49.3%.