Agricultural Cropland Research Articles

Assessment of cultivation intensity can improve the correlative strength between agriculture and the ecological status in rivers across Germany

Agriculture has been identified as a main cause for more than 90% of Germany´s rivers still not meeting good ecological status in 2021. While many large-scale studies observed a negative effect of catchment agricultural land use on river biota, they rarely considered differences in cultivation intensities, although small-scale studies highlight clear differences between the effects of agricultural crops. Here we used Germany-wide and spatially explicit information on crop types to calculate agricultural intensity indices for nutrients and pesticides, weighting different crop types based on average pesticide treatment and nutrient application rates. These indices were then used as explanatory variables for the ecological status of n = 7677 biological sampling sites. Pesticides were more important than nutrient pollution for macroinvertebrates and macrophytes, while diatoms were more sensitive to nutrients. Considering the most relevant intensity index (pesticide or nutrient) slightly increased the correlative strength with ecological status, as compared to the correlation with agricultural land or cropland cover by up to R² = 0.14 for diatoms. Correlative strength of agricultural intensity indices was substantially larger in small mountain and (pre)-alpine streams compared to lowland streams, with an R² up to 0.43 for macroinvertebrates. These results not only confirm previous large-scale studies by demonstrating the detrimental effects of present-day agriculture on river biota, but also shed light on the main pathways involved, particularly highlighting the adverse impacts of agrochemicals. Consequently, to protect river biota, a shift to more sustainable agricultural practices, like reducing pesticide application, is urgently required.

Аппроксимация временных рядов индексов вегетации (NDVI и EVI) для мониторинга сельхозкультур (посевов) Хабаровского края

Approximation of the series of the seasonal vegetation index time series is the basis for monitoring agricultural crops, their identification and cropland classification. For cropland of the Khabarovsk Territory in the period from May to October 2021, NDVI and EVI time series were constructed using Sentinel-2A (20 m) multispectral images using a cloud mask. Five functions were used to approximate time series: Gaussian function; double Gaussian; double sine wave; Fourier series; double logistic. Characteristics of extremums for approximated time series for different types of arable land were built and calculated: buckwheat, perennial grasses, soybeans, fallow and ley. It was shown that each type requires a characteristic species. It was found (p<0.05) that Fourier approximation showed the highest accuracy for NDVI and EVI series (average error, respectively, 8.5% and 16.0%). Approximation of the NDVI series using a double sine, double Gaussian and double logistic function resulted in an error increase of 8.9-10.6%. Approximation of EVI series based on double Gaussian and double sine wave causes an increase in average errors up to 18.3-18.5%. The conducted a posteriori analysis using the Tukey criterion showed that for soybean, fallow and ley lands, it is better to use the Fourier series, double Gaussian or double sine wave to approximate vegetation indices, for buckwheat it is advisable to use the Fourier series or double Gaussian. In general, the average approximation error of the NDVI seasonal time series is 1.5-4 times less than the approximation error of the EVI series.

Conserved grasslands support similar pollinator diversity as pollinator-specific practice regardless of proximal cropland and pesticide exposure.

Pollinator diversity and abundance are declining globally. Cropland agriculture and the corresponding use of agricultural pesticides may contribute to these declines, while increased pollinator habitat (flowering plants) can help mitigate them. Here we tested whether the relative effect of wildflower plantings on pollinator diversity and counts were modified by proportion of nearby agricultural land cover and pesticide exposure in 24 conserved grasslands in Iowa, USA. Compared with general grassland conservation practices, wildflower plantings led to only a 5% increase in pollinator diversity and no change in counts regardless of the proportion of cropland agriculture within a 1 km radius. Pollinator diversity increased earlier in the growing season and with per cent flower cover. Unexpectedly, neither insecticide nor total pesticide concentrations on above-ground passive samplers were related to pollinator diversity. However, pollinator community composition was most strongly related to date of sampling, total pesticide concentration, and forb or flower cover. Our results indicate very little difference in pollinator diversity between grassland conservation practices with and without wildflower plantings. Given the relatively high economic costs of wildflower plantings, our research provides initial evidence that investment in general grassland conservation may efficiently conserve pollinator diversity in temperate regions of intensive cropland agriculture.

Methods for estimating agricultural cropland yield based on the comparison of NDVI images analyzed by means of Image segmentation algorithms: A tool for spatial planning decisions

Methods for estimating agricultural cropland yield based on the comparison of NDVI images analyzed by means of Image segmentation algorithms: A tool for spatial planning decisions

EuroCrops: The Largest Harmonized Open Crop Dataset Across the European Union

EuroCrops contains geo-referenced polygons of agricultural croplands from 16 countries of the European Union (EU) as well as information on the respective crop species grown there. These semantic annotations are derived from self-declarations by farmers receiving subsidies under the common agricultural policy (CAP) of the European Commission (EC). Over the last 1.5 years, the individual national crop datasets have been manually collected, the crop classes have been translated into the English language and transferred into the newly developed hierarchical crop and agriculture taxonomy (HCAT). EuroCrops is publicly available under continuous improvement through an active user community.

Ecological Niche and Positive Clusters of Two West Nile Virus Vectors in Ontario, Canada

West Nile virus (WNV) is a mosquito-borne pathogen associated with uncommon but severe neurological complications in humans, especially among the elderly and immune-compromised. In Northeastern North America, the Culex pipiens/restuans complex and Aedes vexans are the two principal vector mosquito species/species groups of WNV. Using a 10-year surveillance dataset of WNV vector captures at 118 sites across an area of 40,000 km2 in Eastern Ontario, Canada, the ecological niches of Cx. pipiens/restuans and Aedes vexans were modeled by random forest analysis. Spatiotemporal clusters of WNV-positive mosquito pools were identified using Kulldorf’s spatial scan statistic. The study region encompasses land cover types and climate representative of highly populated Southeastern Canada. We found highest vector habitat suitability in the eastern half of the study area, where temperatures are generally warmer (variable importance > 0.40) and residential and agricultural cropland cover is more prominent (variable importance > 0.25). We found spatiotemporal clusters of high WNV infection rates around the city of Ottawa in both mosquito vector species. These results support the previous literature in the same region and elsewhere suggesting areas surrounding highly populated areas are also high-risk areas for vector-borne zoonoses such as the WNV.

Drivers of enhanced evaporative demand in U.S. croplands: Determining relative contribution using constrained input scenarios

AbstractAltered evaporative demand is a global phenomenon observed over recent decades, however, such change has not been attributed explicitly to specific meteorological drivers, hampering consensus on what has caused such change. Here we investigate exactly how much individual drivers have contributed to long‐term grass‐reference evapotranspiration (ETo) change within conterminous United States (CONUS), with an emphasis on agricultural croplands. Using scenarios that constrain individual drivers i.e., air temperatures (T), relative humidity (RH), solar radiation (Rs), and wind speeds (U2) to their climatologies, we determined their relative contribution toward ETo change at monthly and annual scales. Annual ETo increased by 111 mm, or >2 standard deviations (SD) relative to the 1981–2000 baseline, accompanied by strong increase in Rs (2.7 SD), U2 (2.5 SD), T (1.1 SD), and decreased RH (2.3 SD) in regions that account for one‐third of calories produced in the U.S. Annual ETo increase was attributed primarily to T (relative contribution of 36%), followed by Rs (29%), U2 (18%), and RH (17%) with significant spatial and seasonal variability. During agriculturally critical summer months, Rs was the dominant driver with a 40%–50% relative contribution, and other three drivers were roughly equally important. These findings address demand‐side of agricultural water use and imply long‐term change in crop functions and performance, water security, and planning across aridity gradients.

Flash drought evaluation using evaporative stress and evaporative demand drought indices: a case study from Awash River Basin (ARB), Ethiopia

Drought is one of the most devastating phenomena that affect the livelihood of most communities in Ethiopia as they have low adaptive capacity. Recent advancements in remote sensing and drought investigations have made it possible to identify a new type of flash drought that has rapid intensification with a short duration (i.e., less than 1 month unlike conventional droughts). This study intends to identify flash drought in the Awash River Basin (ARB) based on Moderate Resolution Imaging Spectroradiometer (MODIS) data of actual evapotranspiration and potential evapotranspiration using Evaporative Demand Drought Index (EDDI) and Evaporative Stress Index (ESI) indices. The flash drought result exhibited that agricultural lands, grasslands, vegetation areas, and irrigational croplands along the river were vulnerable to flash drought in the ARB. Using ESI, the area of ARB that experienced flash drought in 2002, 2008, 2009, 2012, and 2015 were 23%, 40%, 20%, 40%, and 24%, respectively. These intense flash drought areas can be used as drought monitoring sites. The flash drought extent of EDDI is more compared to ESI because of ESI’s dependency on vegetation coverages and soil moisture. The lowland downstream part of the ARB is highly prone to flash drought, particularly in the major rainy season (MRS) and the last two months of the minor rainy season (mRS). EDDI can discern the onset of flash drought better compared to ESI, but both can be used as a drought early warning mechanisms to minimize agricultural losses and drought-associated risks in the basin.

Markedly declining reproductive functional diversity of food plants in the world’s largest tropical country despite rapid cropland expansion

Cropland intensification in tropical regions is usually associated with agricultural commodity expansion that penalizes the species diversity and environmental services of natural ecosystems. However, the extent to which cropland expansion affects the reproductive functional diversity of crop arrangements remains poorly investigated. Here we examine the agricultural development of a leading agricultural producer and megadiverse country (Brazil) over the last six decades to understand the effects of agricultural expansion on the reproductive functional diversity of crops, particularly those bearing specialized traits. We used the FAO database, which provides annualized information on crop production from 1961 to 2018. Cultivated species were classified according to their reproductive traits and levels of dependence on biotic pollination, used as indicators of functional diversity. Our results show that cropland areas in Brazil expanded by 201.3% from 1961 to 2018. In particular, pollinator‐dependent crops expanded over this period by 305.2% compared to 125.3% in non-dependent crops. Expansion of monoculture farmland was remarkable, comprising 88% of the entire agricultural cropland acreage in 2018, 45% of which was represented by soybean. Additionally, cropland expansion was related to a reduction in functionally diverse crop species, which was most intense for those with specialized reproductive traits. These results indicate a threat to a diversified food production system and its resilience, given the impacts of cropland expansion on native biodiversity and the reduction in pollination services for many crops. We argue that agroecosystems in Brazil require sustainable, pollinator-friendly agricultural practices to maintain or enhance a nutritionally diversified food production system. Integrated practices that sustain agricultural cropland mosaics characterized by high reproductive functional diversity of the cultivated species can be a nature-based solution to protect natural pollinators and pollination services within a diversified food system.

Conservation intensification under risk: An assessment of adoption, additionality, and farmer preferences

AbstractConservation practices used on agricultural cropland can provide important ecosystem services. The United States relies largely on voluntary programs to incentivize adoption of conservation practices, but the success of these efforts relies on good program design. We use a choice experiment to evaluate farmers' willingness to adopt more intensive in‐field conservation practices (continuous no‐till, conservation crop rotation, cover crops, and variable rate application of inputs) using a nonlinear extended expected utility framework that incorporates risk under a conservation contract. We contribute to the literature by providing insights regarding producers' preference for incentive payment mechanism (federal program or carbon market) and the incentive payment needed to induce additionality and practice continuity. We find that although an additional payment might be needed to promote practice continuity among farmers who have previously adopted cover crops, in the case of continuous no‐till, adopters might be willing to forgo additional payment to continue benefiting from the use of this practice. Our results also revealed producers prefer conservation contracts accruing higher off‐farm environmental benefits and federally administered over carbon market programs. This is an important result given an increased public interest in climate change and new proposed carbon mitigation policies and private carbon market initiatives.

Cropland abandonment alleviates soil carbon emissions in the North China Plain

Land use change could profoundly influence the terrestrial ecosystem carbon (C) cycle. However, the effects of agricultural expansion and cropland abandonment on soil microbial respiration remain controversial, and the underlying mechanisms of the land use change effect are lacking. In this study, we conducted a comprehensive survey in four land use types (grassland, cropland, orchard, and old-field grassland) of North China Plain with eight replicates to explore the responses of soil microbial respiration to agricultural expansion and cropland abandonment. We collected surface soil (0-10cm in depth) in each land use type to measure soil physicochemical property and microbial analysis. Our results showed that soil microbial respiration was significantly increased by 15.10mg CO2 kg-1day-1 and 20.06mg CO2 kg-1day-1 due to the conversion of grassland to cropland and orchard, respectively. It confirmed that agricultural expansion might exacerbate soil C emissions. On the contrary, the returning of cropland and orchard to old-field grassland significantly decreased soil microbial respiration by 16.51mg CO2 kg-1day-1 and 21.47mg CO2 kg-1day-1, respectively. Effects of land use change on soil microbial respiration were predominately determined by soil organic and inorganic nitrogen contents, implying that nitrogen fertilizer plays an essential role in soil C loss. These findings highlight that cropland abandonment can effectively mitigate soil CO2 emissions, which should be implemented in agricultural lands with low grain production and high C emissions. Our results improve mechanistic understanding on the response of soil C emission to land use changes.

Per- and polyfluorinated alkyl substances (PFAS) in Pennsylvania surface waters: A statewide assessment, associated sources, and land-use relations

The objectives of this study are to identify per- and polyfluoroalkyl substances (PFAS) in Pennsylvania surface waters, corresponding associations with potential sources of PFAS contamination (PSOC) and other parameters, and compare raw surface water concentrations to human and ecological benchmarks. Surface water samples from 161 streams were collected in September 2019 and were analyzed for 33 target PFAS and water chemistry. Land use and physical attributes in upstream catchments and geospatial counts of PSOC in local catchments are summarized. The hydrologic yield of the sum of 33 PFAS (∑PFAS) for each stream was computed by normalizing each site's load by the drainage area of the upstream catchment. Utilizing conditional inference tree analysis, the percentage of development (>7.58 %) was identified as a primary driver of the ∑PFAS hydrologic yields. When percentage of development was removed from analysis, ∑PFAS yields were closely related to surface water chemistry associated with landscape alteration (e.g., development or agricultural cropland), such as concentrations of total nitrogen, chloride, and ammonia, but also to count of water pollution control facilities (agricultural, industrial, stormwater, and/or municipal waste pollution abatement facilities). In oil and gas development regions, ∑PFAS yields were associated with combined sewage outfalls. Sites surrounded by ≥2 electronic manufacturing facilities had elevated ∑PFAS yields (median = 241 ng/s/km2). Study results are critical to guide future research, regulatory policy, best practices that will mitigate PFAS contamination, and the communication of human health and ecological risks associated with PFAS exposure from surface waters.

Global vegetation greenness interannual variability and its evolvement in recent decades

The interannual variability (IAV) of global vegetation greenness needs careful assessment as it relates to the stability of the climate, conservation of biodiversity, sustainable ecosystem services, and global food security. Here, we investigated the spatial feature and temporal evolvement of global vegetation greenness interannual variability from 1982 to 2015 using the Global Inventory Modeling and Mapping Studies (GIMMS) Normalized Difference Vegetation Index third generation (NDVI3g) data. Generally, regions with herbaceous and short woody plants had larger IAV of vegetation greenness than those with tall woody biome types (7.9% versus 2.9%). On average, all the biomes displayed increasing IAV of vegetation greenness from 1982 to 2015, with notable increases over northern high latitudes (0.135%/year), Eastern Europe (0.037%//year), and Central Australia (0.231%/year). Croplands in China and India experienced decreasing IAV of vegetation greenness (–0.037%/year for China and –0.004%/year for India). The changing IAV of vegetation greenness had implications for climatic, environmental, and anthropogenic changes that influence vegetation dynamics. Some note-worthy factors include climate warming, the CO2 fertilization effect, agricultural practice improvement, cropland abandonment, and China’s Grain-for-Green Program.

Ammonia recovery from organic nitrogen in synthetic dairy manure with a microbial fuel cell

Increasing pressures on the animal and cropland agriculture sectors have led to the realization of problems with animal waste management and ammonia-based fertilizer supply. Bioelectrochemical systems (BES) are a new-age technology that offer a way to address these problems. Microbial fuel cells (MFCs), one type of BES, are traditionally used for electricity generation from microbial degradation of organic matters, but can also be used to recover nutrients from wastes simultaneous with treatment. This research investigated an MFC for ammonia recovery from the organic nitrogen (orgN) fraction of synthetic dairy manure, using the simple amino acid glycine as the orgN source. We used five different synthetic manure compositions to determine their effects on MFC performance, and found minimal sacrifices in performance under orgN conditions when compared to the base condition without orgN. The MFC achieved greater than 90% COD removal in all orgN conditions. Nitrogen (N) removal efficiencies of between 40% and 60% were achieved in orgN conditions, indicating that organic nitrogen can be used as the substrate for ammonia mineralization and further recovery as fertilizer. In addition, we found the MFC was largely populated by electrogenic organisms from the phyla Bacteroidota, Firmicutes, Proteobacteria, and Halobacterota, with organisms in both Bacteroidota and Firmicutes capable of N mineralization present. Lastly, we found that in conditions where orgN is scarce and the only N source provided, microbes preferentially degraded organic matter from other dead organisms, especially as an N source. This increases the concentration of N in the MFC system and introduces important operational constraints for MFCs operated for ammonia recovery from orgN.

Long-term land use and tillage influence on phosphorus species in Brazilian Oxisols: A multi-technique assessment by chemical P fractionation, 31P NMR and P K-edge XANES spectroscopies

Phosphorus (P) interacts with soil constituents in many ways, forming compounds of distinct stabilities in a number of chemical inorganic and organic forms. The identification of these P compounds in tropical agro-ecosystems is especially relevant to understanding potential P availability in these common P-fixing soils, providing information to improve P use efficiency. In this study, we investigated P partitioning and speciation in Brazilian Cerrado Oxisols under different management systems using a combination of sequential chemical P fractionation (SPF), P K-edge XANES and 31P NMR spectroscopy. Topsoil (0–10 cm) samples were obtained from soils under three management regimes, including native vegetation (Cerrado), no-tillage (NT), and conventional tillage (CT) agriculture. Four representative agricultural sites in the Brazilian Cerrado were selected: Ox-1 (Costa Rica-MS), Ox-2 (Sapezal-MT), Ox-3 (Cristalina-GO) and Ox-4 (Tasso Fragoso-MA). In all sites, the soils are classified as Typic Hapludox, varying in cultivation time, soil clay content and oxide types. Long-term cultivation in NT and CT led to large P accumulation in the soil. Chemical P fractionation indicated that labile P was the smallest pool at all sites. P K-edge XANES showed that P is mostly sorbed to the Fe and Al hydr(oxides), goethite, hematite and gibbsite. It also showed that phytate was the predominant organic P species, depleting in sequence from native vegetation to NT and CT management systems. 31P NMR showed that monoester P was present in all soils and management systems, whereas diester-P was found only in soils under native vegetation. The combined use of SPF, XANES and 31P NMR data was necessary to fully understand inorganic and organic P chemistry and reactivity in these tropical agricultural croplands.

Exploring Farmers’ Decisions on Agricultural Intensification and Cropland Expansion in Ethiopia, Ghana, and Zambia through Serious Gaming

This paper explores how increasing agricultural productivity through agricultural intensification may influence farmland expansion decisions of smallholder farmers in Ethiopia, Ghana, and Zambia. Six pairs of farmers at each site (72 in total) from different wealth groups were involved in serious games sessions that simulated different institutional, economic, and governance contexts, with players choosing their resource allocation accordingly. The approach was used to explore with farmers, in a ‘safe space’, whether an increase in agricultural productivity and profitability via intensification would reduce or end farmland expansion into natural habitats. The results show that, under certain conditions (such as poor forest governance and lack of alternative income-generating and investment opportunities), agricultural intensification can lead to more agricultural expansion at the expense of natural habitats, such as forests and grasslands. This suggests that intensification strategies to promote increased productivity may need companion strategies to protect forest ecosystems from expansion at the agricultural frontier.

An evaluation of mango cultivation soils and identification of potentially suitable lands upon conversion of agricultural crop land to mango plantations in semi-arid land of south Telangana plateau, Andhra Pradesh

In the south Telangana plateau, Andhra Pradesh, due to low rainfall and high tempera- ture which is limiting the agriculture crop production as the semi-arid climatic condition. Hence, the crop land is being converted to mango plantation/orchards in most of the areas. The soils of mango cultivation were assessed for their physic- chemical properties as well as soil fertility status by studying two representative pedons from mango cultivated areas. Through a detailed soil survey, land capability classification was done and determined the suitability of land for mango production using GIS and RS. Results revealed that 53.57% area is moderately good cultivable (class III) land followed by class IV which is fairly good cultivable land (16.90%). Out of total geographical area (23240.7 ha), mango is marginally suitable (S3) in 42.71% area which is potential for mango production and 29.45% area is not suitable for mango cultivation. Gravelliness, soil fertility, drainage, root restriction, soil texture are the limiting factors for mango production in the region. Organic carbon (OC) content is low (0.32-0.40%), slightly acidic to neutral in reaction (pH: 6-6.83), non-saline, high -1 base saturation (>50%), low CEC (3.1-6.1 cmol (p+) kg ) and available water content is 4.47 to 7.86%, reddish-brown (5YR4/4) to dark brown (7.5YR4/3) in surface and 35-60% coarse fragments. However, two mango cultivating series are identified. The study helps to increase the area under mango plantations in potential areas and to adopt mango cultivation by addressing limitations in problematic soils.

Drip irrigation improves spring wheat water productivity by reducing leaf area while increasing yield

To mitigate the climate change-induced water shortage and realize the sustainable development of agriculture, drip irrigation, a more efficient water-saving irrigation method, has been intensively implemented in most arid agricultural regions in the world. However, compared to traditional border irrigation, how drip irrigation affects the biophysical conditions in the cropland and how crops physiologically respond to changes in biophysical conditions in terms of water, heat and carbon exchange remain largely unknown. In view of the above situation, to reveal the mechanism of drip irrigation in improving spring wheat water productivity, paired field experiments based on drip irrigation and border irrigation were conducted to extensively monitor water and heat fluxes at a typical spring wheat field (Triticum aestivum L.) in Northwest China during 2017–2020. The results showed that drip irrigation improved yield by 10.3 % and crop water productivity (i.e., yield-to-evapotranspiration-ratio) by 15.6 %, but reduced LAI by 16.9 % in contrast with border irrigation. Under drip irrigation, the lateral development of spring wheat roots was promoted by higher soil temperature combined with frequent dry-wet alternation in the shallow soil layer (0–20 cm), which was the basis for efficient absorption of water and fertilizer, as well as efficient formation of photosynthate. Meanwhile, drip irrigation increased net radiation and decreased latent heat flux by inhibiting leaf growth, thereby increased sensible heat, causing a higher soil temperature (+1.10 ℃) and canopy temperature (+1.11 ℃). Further analysis proved that soil temperature was the key factor affecting yield formation. Based on the above conditions, the decrease in leaf distribution coefficient (−0.030) led to the decrease in evapotranspiration (−5.7 %) and the increase in ear distribution coefficient (+0.029). Therefore, drip irrigation emphasized the role of soil moisture in the soil-plant-atmosphere continuum, enhanced crop activity by increasing field temperature, especially soil temperature, and finally improved yield and water productivity via carbon reallocation. The study revealed the mechanism of drip irrigation for improving spring wheat yield, and would contribute to improving Earth system models in representing agricultural cropland ecosystems with drip irrigation and predicting the subsequent biophysical and biogeochemical feedbacks to climate change.

Global patterns of phylogenetic diversity and transmission of bat coronavirus.

Bats are reservoirs for multiple coronaviruses (CoVs). However, the phylogenetic diversity and transmission of global bat-borne CoVs remain poorly understood. Here, we performed a Bayesian phylogeographic analysis based on 3,594 bat CoV RdRp gene sequences to study the phylogenetic diversity and transmission of bat-borne CoVs and the underlying driving factors. We found that host-switching events occurred more frequently for α-CoVs than for β-CoVs, and the latter was highly constrained by bat phylogeny. Bat species in the families Molossidae, Rhinolophidae, Miniopteridae, and Vespertilionidae had larger contributions to the cross-species transmission of bat CoVs. Regions of eastern and southern Africa, southern South America, Western Europe, and Southeast Asia were more frequently involved in cross-region transmission events of bat CoVs than other regions. Phylogenetic and geographic distances were the most important factors limiting CoV transmission. Bat taxa and global geographic hotspots associated with bat CoV phylogenetic diversity were identified, and bat species richness, mean annual temperature, global agricultural cropland, and human population density were strongly correlated with the phylogenetic diversity of bat CoVs. These findings provide insight into bat CoV evolution and ecological transmission among bat taxa. The identified hotspots of bat CoV evolution and transmission will guide early warnings of bat-borne CoV zoonotic diseases.

Land Use Based Distribution Pattern, Fractionation forms and Health Risk Assessment of Heavy Metals in Mining-affected Soils of Western Ghat of Goa, India

Goa is a biodiversity hotspot and a major iron ore producer state in India. The study investigated heavy metal (HM) distribution pattern, fractionation forms under different land use types near an iron mining including health risks associated with different exposure pathways. Georeferenced 38 soil surface samples, 8 soil profile samples and 6 plant samples were collected from three land use types- agriculture cropland, fallow land and natural vegetation. Collected samples were analyzed for HM contamination in inductively coupled plasma atomic emission spectrophotometer (ICPAES). The mean total HM concentration in surface soil exceeded the background value. Weak acid soluble fraction % of metals posed no to medium risk values. Fallow land had higher metal content in surface soil. Principal component (PC) analysis showed Pb, Cd and Cr metals were more associated with mining activity. Vertical distribution pattern of HM accumulation in soil profiles showed a drastic reduction in HM concentration below plough layer in fallow land indicating anthropogenic sources of origin. Hazard index (HI) in the descending order were Cd> Cr >Pb. Non-carcinogenic HI value were considerably higher than safe level. Higher organic carbon (OC) and clay content in soil had a tendency to accumulate ample HM in unavailable form due to chelation effect. Soils had higher pool of unavailable residual HM as compared to available. Overall the land uses are in medium risk category and site specific management is requisite of the time to maintain the balance of this fragile ecosystem with anthropogenic activities in long run.