Heavy metal contamination of agricultural soils is of worldwide concern. Unfortunately, there are currently no efficient and sustainable approaches for addressing this concern. In this study, we conducted a field experiment in which an agricultural soil highly contaminated by cadmium (Cd), lead (Pb) and zinc (Zn) was treated on-site by an ancient agricultural technique, ‘slash-and-char’, that was able to convert the biomass feedstock (rice straw) into biochar in only one day. We found evidence that in comparison to the untreated soil, the treated soil was associated with decreased bioavailability of the heavy metals and increased vegetable yields. Most importantly, the treatment was also coupled with dramatic reductions in concentrations of the heavy metals in vegetables, which made it possible to produce safe crops in this highly contaminated soil. Collectively, our results support the idea that slash-and-char offers new promise for management of soils contaminated by Cd, Pb and Zn.

Arsenic contamination is turning out to be a major problem these days with its area coverage and the number of people affected directly or indirectly. Now, the level of the contaminant has spread over the soil and sediments from groundwater and other natural sources. Arsenic poisoning in groundwater events is familiar to the world, but the consequences of soil contamination are still unrevealed to the community, specially the people of contaminated counties. Arsenic is a serious instantaneous concern for the people and other life forms regarding the poisoning through crops and vegetables. Many remediation technologies that mainly include physical, chemical, and a few biological methods have been evolved with time to check its effects. The physical and chemical methods for this purpose are often inefficient and/or very expensive, mainly limited to application in aqueous systems, and produce toxic sludge, which again becomes a matter of concern. But bioremediation relies on the fact that biological organisms have the ability to degrade, detoxify, and even accumulate harmful chemicals and offers attractive perspectives for biomonitoring (via biosensors), treatment of wastewater, and the recycling of polluted soils.

In the present work, the role of chemical compounds of one abundant vegetable waste, exhausted coffee, on Cr(VI), Cu(II), and Ni(II) sorption has been investigated. For this purpose, exhausted coffee was subjected to sequential extractions by using dichloromethane (DCM), ethanol (EtOH), water, and NaOH 1 %. The raw and treated biomass resulting from the extractions were used for metal ions sorption. Sorption results were discussed taking into consideration polarity and functional groups of raw and treated biomass. In general, the successive removal of extractives led to an insignificant increase in the studied metal ions sorption after DCM, EtOH, and water. The sorption results using free-extractive materials showed that metal sorption can be effectively achieved without this non-structural fraction of the sorbent. Alkaline hydrolysis destroyed in part the structural compounds of the sorbent resulting in an insignificant decrease of chromium removal while a significant increase of copper and nickel sorption was observed. The determination of elemental ratios of exhausted coffee and all treated biomass evidenced the involvement of oxygen functional groups in copper and nickel sorption. FTIR analysis confirmed the involvement of lignin moieties in the chromium sorption by exhausted coffee. As a final remark, this study shows that the sequential extraction opens new expectations to the total valorisation of lignocellulosic-based biomasses. The extractives can be removed and used as a biosource of valuable compounds, and the resulting waste can be used as a sorbent for metal ions keeping the same capacity for metal sorption as the non-extracted biomass.

High nitrogen (N) concentrations in rural domestic water supplies have been attributed to excessive agricultural N leaching into shallow groundwater systems; therefore, it is important to determine the impact of agriculture (e.g., rice production) on groundwater quality. To understand the impact of agricultural land use on the N concentrations in the shallow groundwater in subtropical central China, a large observation program was established to observe ammonium-N (NH₄-N), nitrate-N (NO₃-N), and total N (TN) concentrations in 161 groundwater observation wells from April 2010 to November 2012. The results indicated that the median values of NH₄-N, NO₃-N, and TN concentrations in the groundwater were 0.15, 0.39, and 1.38 mg N L⁻¹, respectively. A total of 36.3 % of the water samples were categorized as NH₄-N pollution, and only a small portion of the samples were categorized as NO₃-N pollution, based on the Chinese Environmental Quality Standards for Groundwater of GB/T 14848-93 (General Administration of Quality Supervision of China, 1993). These results indicated of moderate groundwater NH₄-N pollution, which was mainly attributed to intensive rice agriculture with great N fertilizer application rates in the catchment. In addition, tea and vegetable fields showed higher groundwater NO₃-N and TN concentrations than other agricultural land use types. The factorial correspondence analysis (FCA) suggested that the flooded agricultural land use types (e.g., single-rice and double-rice) had potential to impose NH₄-N pollution, particularly in the soil exhausting season during from July to October. And, the great N fertilizer application rates could lead to a worse NO₃-N and TN pollution in shallow groundwater. Hence, to protect groundwater quality and minimize NH₄-N pollution, managing optimal fertilizer application and applying appropriate agricultural land use types should be implemented in the region.

Long-term heavy organic fertilizer application has linked greenhouse vegetable production (GVP) with trace metal contamination in north China. Given that trace metals release from fertilizers and their availability may be affected by discrepant environmental conditions, especially temperature under different greenhouses, this study investigated Cd, Cu, Pb, and Zn accumulation and contamination extent in soil as well as their phytoavailability under two major greenhouses in Tongshan, north China, namely solar greenhouse (SG) and round-arched plastic greenhouse (RAPG), to evaluate their presumed difference. The results showed significant Cd, Cu, Pb, and Zn accumulation in GVP soil by comparing with those in open-field soil, but their accumulation extent and rates were generally greater in SG than those in RAPG. This may be related to more release of trace metals to soil due to the acceleration of decomposition and humification process of organic fertilizers under higher soil temperature in SG relative to that in RAPG. Overall, soil in both greenhouses was generally less polluted or moderately polluted by the study metals. Similarly, decreased soil pH and elevated soil available metals in SG caused higher trace metals in leaf vegetables in SG than those in RAPG, although there was no obvious risk via vegetable consumption under both greenhouses. Lower soil pH may be predominantly ascribed to more intensive farming practices in SG while elevated soil available metals may be attributed to more release of dissolved organic matter-metal complexes from soil under higher temperature in SG. The data provided in this study may assist in developing reasonable and sustainable fertilization strategies to abate trace metal contamination in both greenhouses.

The contamination of phthalate esters (PAEs) has become a potential threat to the environment and human health because they could be easily released as plasticizers from the daily supply products, especially in polyethylene films. Concentration levels of total six PAEs, nominated as priority pollutants by the US Environmental Protection Agency (USEPA), were investigated in soils and vegetables from four greenhouse areas in suburbs of Nanjing, East China. Total PAEs concentration ranged from 930 ± 840 to 2 450 ± 710 μg kg⁻¹ (dry weight (DW)) in soil and from 790 ± 630 to 3 010 ± 2 130 μg kg⁻¹ in vegetables. Higher concentrations of PAEs were found in soils except in Suo Shi (SS) area and in vegetables, especially in potherb mustard and purple tsai-tai samples. Risk assessment mainly based on the exposures of soil ingestion and daily vegetable intake indicated that bis(2-ethylhexyl) phthalate (DEHP) in the samples from Gu Li (GL) and Hu Shu (HS) exhibited the highest hazard to children less than 6-year old. Therefore, the human health risk of the PAEs contamination in soils and vegetables should greatly be of a concern, especially for their environmental estrogen analog effects.

Nitrogen (N) loss from vegetable cropping systems has become a significant environmental issue in China. In this study, estimation of N balances in both open-air and greenhouse vegetable cropping systems in China was established. Results showed that the total N input in open-air and greenhouse vegetable cropping systems in 2010 was 5.44 and 2.60 Tg, respectively. Chemical fertilizer N input in the two cropping systems was 201 kg N ha⁻¹ per season (open-air) and 478 kg N ha⁻¹ per season (greenhouse). The N use efficiency (NUE) was 25.9 ± 13.3 and 19.7 ± 9.4 % for open-air and greenhouse vegetable cropping systems, respectively, significantly lower than that of maize, wheat, and rice. Approximately 30.6 % of total N input was accumulated in soils and 0.8 % was lost by ammonia volatilization in greenhouse vegetable system, while N accumulation and ammonia volatilization accounted for 19.1 and 11.1 %, respectively, of total N input in open-air vegetable systems.

It is common knowledge that soils irrigated with wastewater accumulate heavy metals more than those irrigated with cleaner water sources. However, little is known on metal concentrations in soils and cultivars after the cessation of wastewater use. This study assessed the accumulation and health risk of heavy metals 3 years post-wastewater irrigation in soils, vegetables, and farmers’ hair. Soils, vegetables, and hair samples were collected from villages previously irrigating with wastewater (experimental villages) and villages with no history of wastewater irrigation (control villages). Soil samples were digested in a mixture of HCL/HNO₃/HCLO₄/HF. Plants and hair samples were digested in HNO₃/HCLO₄ mixture. Inductive coupled plasma-optical emission spectrometer (ICP-OES) was used to determine metal concentrations of digested extracts. Study results indicate a persistence of heavy metal concentration in soils and plants from farms previously irrigated with wastewater. In addition, soils previously irrigated with wastewater were severely contaminated with cadmium. Hair metal concentrations of farmers previously irrigating with wastewater were significantly higher (P < 0.05) than farmers irrigating with clean water, but metal concentrations in hair samples of farmers previously irrigating with wastewater were not associated with current soil metal concentrations. The study concludes that there is a persistence of heavy metals in soils and plants previously irrigated with wastewater, but high metal concentrations in hair samples of farmers cannot be associated with current soil metal concentrations.

A health risk assessment of food crops contaminated with heavy metals (Cu, Zn, Pb, As, Cd, and Cr) through the intake of cereals and vegetables grown from biogas slurry irrigated sites was conducted. In the vegetable soils and cereal soils, the concentrations of Zn, Pb, and Cd were far higher than Chinese agricultural standards. The pollution conditions of the aforementioned heavy metals varied with the seasons. Typically, the pollution was more serious in summer than in autumn. Furthermore, the accumulative properties of the heavy metals were different in the cereals and vegetables. In particular, Cu, Zn, and Pb tended to accumulate in rice with concentrations of 6.70, 36.58, and 4.14 mg kg⁻¹, respectively. Pb and Cd in cereals and vegetables exceeded the maximum permissible concentrations in China. The health risk assessment revealed that the daily intake (DI) and target hazard quotients (THQs) of Pb, As, and Cd in cereals and vegetables also exceeded the FAO/WHO limit. The results indicated that heavy metal contamination posed a severe health risk to local humans.

Since their discovery in the late 1980s, neonicotinoid pesticides have become the most widely used class of insecticides worldwide, with large-scale applications ranging from plant protection (crops, vegetables, fruits), veterinary products, and biocides to invertebrate pest control in fish farming. In this review, we address the phenyl-pyrazole fipronil together with neonicotinoids because of similarities in their toxicity, physicochemical profiles, and presence in the environment. Neonicotinoids and fipronil currently account for approximately one third of the world insecticide market; the annual world production of the archetype neonicotinoid, imidacloprid, was estimated to be ca. 20,000 tonnes active substance in 2010. There were several reasons for the initial success of neonicotinoids and fipronil: (1) there was no known pesticide resistance in target pests, mainly because of their recent development, (2) their physicochemical properties included many advantages over previous generations of insecticides (i.e., organophosphates, carbamates, pyrethroids, etc.), and (3) they shared an assumed reduced operator and consumer risk. Due to their systemic nature, they are taken up by the roots or leaves and translocated to all parts of the plant, which, in turn, makes them effectively toxic to herbivorous insects. The toxicity persists for a variable period of time—depending on the plant, its growth stage, and the amount of pesticide applied. A wide variety of applications are available, including the most common prophylactic non-Good Agricultural Practices (GAP) application by seed coating. As a result of their extensive use and physicochemical properties, these substances can be found in all environmental compartments including soil, water, and air. Neonicotinoids and fipronil operate by disrupting neural transmission in the central nervous system of invertebrates. Neonicotinoids mimic the action of neurotransmitters, while fipronil inhibits neuronal receptors. In doing so, they continuously stimulate neurons leading ultimately to death of target invertebrates. Like virtually all insecticides, they can also have lethal and sublethal impacts on non-target organisms, including insect predators and vertebrates. Furthermore, a range of synergistic effects with other stressors have been documented. Here, we review extensively their metabolic pathways, showing how they form both compound-specific and common metabolites which can themselves be toxic. These may result in prolonged toxicity. Considering their wide commercial expansion, mode of action, the systemic properties in plants, persistence and environmental fate, coupled with limited information about the toxicity profiles of these compounds and their metabolites, neonicotinoids and fipronil may entail significant risks to the environment. A global evaluation of the potential collateral effects of their use is therefore timely. The present paper and subsequent chapters in this review of the global literature explore these risks and show a growing body of evidence that persistent, low concentrations of these insecticides pose serious risks of undesirable environmental impacts.