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A large amount of chemicals is annually applied at the agricultural soils as fertilizers and pesticides. Such applications may result in the increase of heavy metals particularly Cd, Pb, and As. The objective of this study was to investigate the variability of chemical applications on Cd, Pb, and As concentrations of wheat-cultivated soils. Consequently, a study area was designed and was divided into four subareas (A, B, C, and D). The soil sampling was carried out in 40 points of cultivated durum wheat during the 2006-2007 periods. The samples were taken to the laboratory to measure their heavy metal concentration, soil texture, pH, electrical conductivity, cationic exchange capacity, organic matter, and carbonate contents. The result indicated that Cd, Pb, and As concentrations were increased in the cultivated soils due to fertilizer application. Although the statistical analysis indicates that these heavy metals increased significantly (P value < 0.05), the lead and arsenic concentrations were increased dramatically compared to Cd concentration. This can be related to overapplication of fertilizers as well as the pesticides that are used to replant plant pests, herbs, and rats.

Concentrations of Cu, Zn, Pb, Cr, Cd, Fe, and Ni have been estimated in soils and vegetables grown in and around an industrial area of Bangladesh. The order of metal contents was found to be Fe > Cu > Zn > Cr > Pb > Ni > Cd in contaminated irrigation water, and a similar pattern Fe > Zn > Ni > Cr > Pb > Cu > Cd was also observed in arable soils. Metal levels observed in different sources were compared with WHO, SEPA, and established permissible levels reported by different authors. Mean concentration of Cu, Fe, and Cd in irrigation water and Cd content in soil were much above the recommended level. Accumulation of the heavy metals in vegetables studied was lower than the recommended maximum tolerable levels proposed by the Joint FAO/WHO Expert Committee on Food Additives (1999), with the exception of Cd which exhibited elevated content. Uptake and translocation pattern of metal from soil to edible parts of vegetables were quite distinguished for almost all the elements examined.

The interrelationships between hydrologically driven evolution of legacy landscapes downstream of major mining districts and the contamination of lowland ecosystems are poorly understood over centennial time scales. Here, we demonstrate within piedmont valleys of California’s Sierra Nevada, through new and historical data supported by modeling, that anthropogenic fans produced by 19th century gold mining comprise an episodically persistent source of sediment-adsorbed Hg to lowlands. Within the enormous, iconic Yuba Fan, we highlight (i) an apparent shift in the relative processes of fan evolution from gradual vertical channel entrenchment to punctuated lateral erosion of fan terraces, thus enabling entrainment of large volumes of Hg-laden sediment during individual floods, and (ii) systematic intrafan redistribution and downstream progradation of fan sediment into the Central Valley, triggered by terrace erosion during increasingly long, 10-y flood events. Each major flood apparently erodes stored sediment and delivers to sensitive lowlands the equivalent of ∼10–30% of the entire postmining Sierran Hg mass so far conveyed to the San Francisco Bay-Delta (SFBD). This process of protracted but episodic erosion of legacy sediment and associated Hg is likely to persist for >10 ⁴ y. It creates, within an immense swath of river corridor well upstream of the SFBD, new contaminated floodplain surfaces primed for Hg methylation and augments/replenishes potential Hg sources to the SFBD. Anticipation, prediction, and management of toxic sediment delivery, and corresponding risks to lowland ecology and human society globally, depend on the morphodynamic stage of anthropogenic fan evolution, synergistically coupled to changing frequency of and duration extreme floods.

This paper investigates the pollution load of selected trace elements in 32 soil samples collected around 21 different mining areas of the Iberian Pyrite Belt (Southwest Spain), integrating chemical data with soil parameters to help understand the partitioning and mobility of pollutants. The minesoils are depleted in acid neutralising minerals and show limiting physicochemical properties, including low pH values and very high anomalies of potentially hazardous metals. The total concentrations of As (up to 1,560 mg kg⁻¹) and certain heavy metals (up to 2,874 mg kg⁻¹ Cu, 6,500 mg kg⁻¹ Pb, 6,890 mg kg⁻¹ Zn, 62 mg kg⁻¹ Hg and 22 mg kg⁻¹ Cd) are two orders of magnitude above the soil background values. The close association of Cd and Zn with the carbonate content in lime-amended minesoils suggests metal immobilisation through adsorption and/or co-precipitation mechanisms, after acid neutralisation, whereas As and Pb are similarly partitioned into the soil and mostly associated with iron oxy-hydroxides.

Phosphorus application in excess of crop needs has increased the concentration of P in surface soil and runoff and led many states to develop P‐based nutrient management strategies. However, insufficient data are available relating P in surface soil, surface runoff, and subsurface drainage to develop sound guidelines. Thus, we investigated P release from the surface (0–5 cm depth) of a Denbigh silt loam from Devon, U.K. (30–160 mg kg−1 Olsen P) and Alvin, Berks, Calvin, and Watson soils from Pennsylvania (10–763 mg kg−1 Mehlich‐3 P) in relation to the concentration of P in surface runoff and subsurface drainage. A change point, where the slopes of two linear relationships between water‐ or CaCl2–extractable soil P and soil test phosphorus (STP) (Olsen or Mehlich‐3) meet, was evident for the Denbigh at 33 to 36 mg kg−1 Olsen P, and the Alvin and Berks soils at 185 to 190 mg Mehlich‐3 P kg−1 Similar change points were also observed when STP was related to the P concentration of surface runoff (185 mg kg−1) and subsurface drainage (193 mg kg−1). The use of water and CaCl2 extraction of surface soil is suggested to estimate surface runoff P (r2 of 0.92 for UK and 0.86 for PA soils) and subsurface drainage P (r2 of 0.82 for UK and 0.88 for PA soils), and to determine a change point in STP, which may be used in support of agricultural and environmental P management.

Four soil profiles located near a copper smelter in Poland were investigated for the distribution and chemical fractions of Cu, Pb, and Zn and their mobility in relation to soil properties. Contamination with heavy metals was primarily restricted to surface horizons and the extent of contamination was 7‐ to 115‐fold for Cu, 30‐fold for Pb, and 6‐fold for Zn as compared with subsurface horizons. In the less‐contaminated fine‐textured soil, the metals were distributed in the order: residual >> Fe–Mn oxides occluded > organically complexed > exchangeable and specifically adsorbed, while the order for sandy soils was: residual > organically complexed > Fe–Mn oxides occluded > exchangeable and specifically adsorbed. The contaminated surface horizons of these profiles showed no consistent pattern of metal distribution. However, the common features of highly contaminated soils were very low percentage of residual fraction and the dominance of the NH4OAc extractable fraction. The sum of mobile metal fractions was generally <10% in subsurface horizons, while in the contaminated surface horizons these fractions made up 50% of the total metal contents. Soil properties contributed more to the relative distribution of the metal fractions in the studied profiles than did the distance and direction to the source of pollution. The amounts of metal extracted by 0.01 M CaCl2 accounted for only a small part of the same metals extracted by NH4OAc. The mobility indexes of metals correlated positively and significantly with the total content of metals and negatively with the clay content.

The current study investigated the sorption of sulfadimethoxine (SMT), sulfamethoxazole (SMX), tetracycline (TET), and oxytetracycline (OTC) to Na-rich montmorillonite clay in synthetic effluent (SE) and field wastewater effluent (FE). Both SMT and SMX showed a low sorption capacity and are therefore likely to be highly mobile in the environment, while the sorption of TET to clay in environmental pH range (6.5-7.5) showed similarly high adsorption capacity. Differences in sorption capacities of TET and OTC to SE or FE were attributed to the various concentrations of divalent cations in the effluents. In addition, differences in sorption of OTC or TET to SE were attributed to their different molecular structure. Moreover, the adsorption of TET in SE and FE showed linear adsorption isotherms and fitted to Freundlich model. Further experiments showed that addition of humic acid or SE to TET sorbed to clay did not enhance or suppress the sorption of TET to clay.

To investigate the influence of crop residues decomposition on nitrous oxide (N 2 O) emission, a field study was performed with application of crop residues with different C:N ratios in a bare yellow brown soil at the experimental station of Zhangjiachong at Zigui, China. We set up six experimental treatments: no crop residue (CK), rapeseed cake (RC), potato stalk (PS), rice straw (RS), wheat straw (WS), and corn straw (CS). The carbon (C) to nitrogen (N) ratios of these crop residues were 7.5, 32.9, 40.4, 65.7, and 90.9, respectively. Nitrous oxide fluxes were measured using a static closed chamber method. N 2 O emissions were significantly enhanced by incorporation of crop residues. Cumulative N 2 O emissions negatively correlated with C:N ratio ( R 2  = 0.9821) of the crop residue, but they were positively correlated with average concentrations of dissolved organic carbon and microbial biomass carbon. Nitrogen emission fraction, calculated as N 2 O–N emissions originated from the crop residues N, positively correlated with C:N ratio of the residues ( P   <  0.05). Soil temperature did, whereas soil moisture did not, control the residue’s induced N 2 O emissions because a significant correlation ( P   <  0.01) existed between soil temperature and N 2 O emissions in all treatments except the control. In contrast, a significant relationship between soil moisture and N 2 O emissions was found in the control only. Furthermore, N 2 O emission significantly correlated ( P   <  0.05) with NO 3 – –N, and NH 4 + –N contents from all residue treatments. These results indicate that (1) crop residues with distinct carbon and nitrogen contents can significantly alter soil N 2 O flux rates; and (2) soil biotic as well as abiotic variables are critical in determining soil–atmospheric N 2 O emissions after crop residue incorporation into soil.

Trace elements may present an environmental hazard in the vicinity of mining and smelting activities. However, the factors controlling their distribution and transfer within the soil and vegetation systems are not always well defined. Total concentrations of up to 15,195mg . kg super(-1) As, 6,690mg . kg super(-1) Cu, 24,820mg . kg super(-1) Pb and 9,810mg . kg super(-1) Zn in soils, and 62mg . kg super(-1) As, 1,765mg . kg super(-1) Cu, 280mg . kg super(-1) Pb and 3,460mg . kg super(-1) Zn in vegetation were measured. However, unusually for smelters and mines of a similar size, the elevated trace element concentrations in soils were found to be restricted to the immediate vicinity of the mines and smelters (maximum 2-3km). Parent material, prevailing wind direction, and soil physical and chemical characteristics were found to correlate poorly with the restricted trace element distributions in soils. Hypotheses are given for this unusual distribution: (1) the contaminated soils were removed by erosion or (2) mines and smelters released large heavy particles that could not have been transported long distances. Analyses of the accumulation of trace elements in vegetation (median ratios: As 0.06, Cu 0.19, Pb 0.54 and Zn 1.07) and the percentage of total trace elements being DTPA extractable in soils (median percentages: As 0.06%, Cu 15%, Pb 7% and Zn 4%) indicated higher relative trace element mobility in soils with low total concentrations than in soils with elevated concentrations.

Subsurface pathways can play an important role in agricultural phosphorus (P) losses that can decrease surface water quality. This study evaluated agronomic and environmental soil tests for predicting P losses in water leaching from undisturbed soils. Intact soil columns were collected for five soil types that had a wide range in soil test P. The columns were leached with deionized water, the leachate analyzed for dissolved reactive phosphorus (DRP), and the soils analyzed for water-soluble phosphorus (WSP), 0.01 M CaCl2 P (CaCl2–P), iron-strip phosphorus (FeO-P), and Mehlich-1 and Mehlich-3 extractable P, Al, and Fe. The Mehlich-3 P saturation ratio (M3-PSR) was calculated as the molar ratio of Mehlich-3 extractable P/[Al + Fe]. Leachate DRP was frequently above concentrations associated with eutrophication. For the relationship between DRP in leachate and all of the soil tests used, a change point was determined, below which leachate DRP increased slowly per unit increase in soil test P, and above which leachate DRP increased rapidly. Environmental soil tests (WSP, CaCl2–P, and FeO-P) were slightly better at predicting leachate DRP than agronomic soil tests (Mehlich-1 P, Mehlich-3 P, and the M3-PSR), although the M3-PSR was as good as the environmental soil tests if two outliers were omitted. Our results support the development of Mehlich-3 P and M3-PSR categories for profitable agriculture and environmental protection; however, to most accurately characterize the risk of P loss from soil to water by leaching, soil P testing must be fully integrated with other site properties and P management practices.