The long-term use of sewage to irrigate farmland will increase the content of heavy metals in the soil and cause soil pollution. Heavy metal pollution in soils will restrict the sustainable development of local agriculture and will have a negative impact on the ecological environment. In this paper, the irrigation areas using domestic sewage, mixed sewage and industrial sewage as an irrigation water source for many years have been selected as the research objects, and the content of the heavy metals lead (Pb), copper (Cu), zinc (Zn) and cadmium (Cd) in the soil with the depth of 0-20cm, 20-50cm and 50-80cm of three kinds of sewage irrigation areas are assessed using single factor pollution index method and Nemerow comprehensive index method, and the potential ecological risks of heavy metals in the soil are assessed using Hakanson ecological risk index method. The results show that the content of heavy metals Pb, Cu, Zn and Cd in different depths of the three sewage irrigation areas does not exceed the national standard limit, and the heavy metal pollution grade in the soil belongs to the safety grade, indicating that the content of heavy metals in the soil has not reached the alert level. The potential ecological risks of heavy metals in the soil show minor ecological risks judging from single indexes, while Cd shows that the ecological risks are at a strong level. Judging from the comprehensive potential ecological risk index, the potential ecological risks of the heavy metals in the study area is minor in graded, but the heavy metals in the soil of the mixed sewage irrigation area and the industrial sewage irrigation area have a moderate grade of potential ecological risks at the depth of 50-80 cm. Therefore, although the content of the heavy metals in the soil of the three kinds of sewage irrigation areas in the study area is safe, the potential ecological risk of Cd is quite high, which should be paid attention to.

The contamination of heavy metal in leachate was investigated at various sites with different solid waste management, namely an open dump, controlled dump, and sanitary landfill. The results indicated that all four heavy metals investigated (cadmium, lead, mercury, and manganese) were present in the leachate at all solid waste management sites. The highest cadmium and lead concentrations were each observed in open dump leachate samples, while the highest manganese and mercury concentrations were each observed in controlled dump leachate samples.

Analysis of soil samples collected from various banana fields in Kozhikode district was carried out to identify the extent of heavy metal and pesticide contamination. Analysis by atomic absorption spectrometry revealed contamination of lead in some of the banana fields (Omasseri, Balussery, Vengeri & Nanmanda) in the district. The Gas Chromatogram analysis revealed that the banana fields in Kozhikode district were free of organo-chloride and organo-phosphate pesticide contamination. Among the several ornamental plants evaluated for assessing lead phytoremediation potential, Dianthus chinensis L. showed the highest phytoaccumulation potential. Chrysanthemum indicum L., Ruellia simplex C. Wright and Lantana camara L.also showed high lead accumulation. Therefore, these ornamental plants could be used in phytoremediation to remove lead from contaminated soils.

Heavy metal accumulation in soils, and subsequently, in vegetation by long-term wastewater irrigation has a potentially detrimental effect on humans via their transfer along the food chain. In this reconnaissance study the effects of wastewater irrigation on the accumulation of heavy metals (Co, Cr, Cu, Mn, Ni, Pb and Zn) in soils and vegetables from croplands along some ~60 km stretches of Sabarmati River, near Ahmedabad city were assessed. Geochemical factors associated with metals in the soil-water environment seem to regulate more the metal transfer (soil-to-vegetable) than the physiological factors associated with the vegetable’s types.The risk associated with the dietary intake of metal contaminated vegetables was quantified by Hazard Quotient (HQ). HQ was found to be very less sensitive on to the dietary intake pattern (e.g., leafy versus non-leafy vegetables) of the consumers. In contrast to low risk associated with Co, Cu, Ni and Zn with very low HQ values, high risk was found for Pb (HQ of ~6.1±0.6) followed by both Mn and Cr (HQ of ~1.0 ± 0.1). Based on the results on wastewater irrigation in the studied region, we suggest more efficient treatment of wastewater facilities and semi-decadal monitoring of heavy metal in vegetables grown under wastewater irrigated soils.

Soil pollution is a worldwide problem caused by both natural and anthropogenic activities. This has resulted in health and physiological problems to both plants and animals. This study investigated heavy metals in soils within the immediate vicinity. Soils from Seven APIIC zones in Visakhapatnam were collected and analysed for physicochemical characteristics and heavy metals. The data obtained were subjected to the pollution index model and multivariate statistical analysis. The data obtained showed that the soils are rich in zinc, and heavy metals are above trace level with a minor positively skewed distribution. The analysis of pollution index, geoaccumulation index and ecological risk factors in soils in all the locations showed that they are mainly contaminated and polluted by Cd followed by Zn. The mean heavy metal concentrations around APIIC can be arranged in increasing order as Cr < Co < Pb < Cu < Cd < Zn. Element pairs such as Zn-Pb, Zn-Cu, Zn-Cd, Pb-Cu, Pb-Cd, Cu-Cr, Cd-Co and Cr-Co showed strong positive correlation coefficient “r” indicating their association in the study area. The observed concentrations of heavy metals revealed that soil contamination has been increasing and measures must be taken to ensure the adoption of more environment-friendly practices.

An assessment of heavy metal concentration in wild-captured Macrobrachium rosenbergii (giant freshwater prawns) from their natural habitat is important since it is susceptible to environmental pollution due to the rapid development and human activities along the Sarawak River. This study aimed to estimate the heavy metal contamination in muscles, exoskeletons and gills of the M. rosenbergii and to estimate the health risk assessment to human consumption. The concentration of heavy metals was analyzed by the flame atomic absorption spectrophotometer and the flow injection mercury system. The metal concentrations in prawns were detected in the following order: Hg < Cd < Co < Cu < Zn; in all body parts (P < 0.05), where a high concentration of metals was recorded in gills due to its function as the excretion site of contaminants from the body. A positive correlation of Co, Cu, and Zn in muscles and gills was observed with the increasing size of prawns. The human health risk assessment indicated a less potential adverse health effect of prawns for consumption from Sarawak River (hazard index values < 1). All samples contained metals below the Joint FAO/WHO Expert Committee on Food Additives (JECFA) permissible limit for human consumption (Cd < 2 mg/kg; Cu < 30 mg/kg; Zn < 150 mg/kg; Hg < 1 mg/kg). Therefore, M. rosenbergii from the Sarawak River were not contaminated enough to prevail high risk on human health, but regular monitoring is suggested for seasonal variability of heavy metals in M. rosenbergii for safeguarding human health.