Gaseous and soil OCPs and PCBs along the Indus River, Pakistan: spatial patterns and air–soil gradients

This study presents first-hand information on the occurrence of persistent organic pollutants (POPs) in the ambient air and surface soil along the Indus flood-plain, Pakistan. The sampling campaign was conducted at 15 site locations during 2014–15, along the Indus River (approximately 1300 km). Composite surface soil samples (N = 15) and passive air samples (N = 15) were collected for the estimation of gaseous POPs as well as air–soil exchange to evaluate the POP emission and distribution or dispersion patterns, source tracking, and contribution of the local and regional sources towards POP accumulation in the Indus River system. Among the studied POPs, levels of DDTs and PCBs were noticeably higher in ambient air (50–560 and 10–1100 pg m−3) and in soil (0.20–350 and 1.40–20 ng g−1), respectively. Regarding the spatial patterns, higher DDT concentrations (ng g−1) were detected in the air and soil samples collected from the wet mountain zone (WMZ) (p \u3c 0.05), followed by the alluvial riverine zone (ARZ), low-lying mountain zone (LLZ), and frozen mountain zone (FMZ). The PCB data did not exhibit significant differences (p \u3e 0.05) for the air samples, while PCB concentrations were significantly higher (p \u3c 0.05) in soil from the LLZ, which may be associated with rapid urbanization and industrial activities in this area. The air–soil exchange of DDTs and PCBs showed net volatilization at most of the studied sites except for a few samples from the FMZ and WMZ. Results of this study about air–soil exchange gradients indicate the long range regional atmospheric transport (LRAT) of POPs to the colder areas (FMZ) of Pakistan, where these act as a secondary source of POPs in these areas

Freely dissolved Organochlorine Pesticides (OCPs) and Polychlorinated Biphenyls (PCBs) along the Indus River Pakistan: Spatial pattern and Risk assessment

Freely dissolved OCPs and PCBs were measured by using polyethylene passive samplers at 15 sites during 2014 throughout the stretch of the Indus River to investigate the spatial pattern and risk assess. Levels (pg/L) of dissolved ∑OCPs and ∑PCBs ranged from 34 to 1600 and from 3 to 230. Among the detected OCPs, dissolved DDTs (p,p′-DDE, followed by p,p′-DDT) predominated with levels of 0.48 to 220 pg/L. The order of occurrence for other studied OCPs was as follows: HCB, endosulfans, chlordanes, and HCHs. Spatially, dissolved (pg/L) ∑OCPs varied (p \u3c 0.05) as the following: surface water of the alluvial riverine zone (ARZ) showed the highest levels (114) followed by the frozen mountain zone (FMZ) (52.9), low-lying zone (LLZ) (28.73), and wet mountain zone (WMZ) (14.43), respectively. However, our zone-wise PCB data did not exhibit significant differences (p \u3e 0.05). Principal component analysis/multilinear regression results showed pesticide usage in the crop/orchard fields and health sector, electric and electronic materials, and widespread industrial activities as the main source of OCPs and PCBs along the Indus River. Our results showed that OCPs and PCBs contaminated water intake, playing an important role towards the considerable cancer/non-cancer risk (HI and CR values) along the Indus River Flood-Plain

Soil phosphorus fractionation as a tool for monitoring dust phosphorus signature underneath a Blue Pine (Pinus wallichiana) canopy in a Temperate Forest

Aims of the study: This study aims (i) to monitor the amount of dust deposition during dry season in the moist temperate forest; (ii) to study nature of P fractions in the dust samples falling on the trees in the region; (iii) to study soil P fractions as influenced by the processes of throughfall and stemflow of a Blue Pine (Pinus wallichiana) canopy and to finger print the contribution of dust towards P input in the temperate forest ecosystem.Area of study: The site used for the collection of soil samples was situated at an elevation of 6900 feet above sea levels (temperate forest in Himalaya region) in the Thandani area national forest located in the north west of Pakistan.Material and methods:  For soil sampling and processing, three forest sites with three old tree plants per site were selected at approximately leveled plain for surface soil sampling. Two dust samples were collected and analyzed for different physicochemical properties along with different P fractions. First dust sample was collected from a site situated at an elevation of 4000 feet and second one was collected from an elevation of 6500 feet above sea levels. Modified Hedley procedure for the fractionation of P in the dust and soil samples were used.Main results: The input of dust was 43 and 20 kg ha-1 during drier months of the year (September-June) at lower and higher elevation sites respectively, and the dust from lower elevation site had relative more all P fractions than the other dust sample. However, HCl-Pi fraction was dominant in both samples. Both labile (water plus NaHCO3) and non-labile (NaOH plus HCl) inorganic P (Pi) fractions were significantly increased in the surface soil by both stemflow and throughfall compared to the open field soil. The buildup of NaOH and HCl-Pi pools in soils underneath the canopy might prove useful in fingerprinting the contribution of atmospheric dust towards P cycling in this temperate forest.Research highlights: The role of dust in the cycling of P in temperate forest in Himalaya region.Keywords: soil phosphorus fractions; atmospheric dust; stemflow, throughfall; temperate forest

Environmental monitoring of organo-halogenated contaminants (OHCs) in surface soils from Pakistan

Extensive monitoring of organo-halogenated contaminants (OHCs) from surface soils of different land-use types from Pakistan was carried out during 2010. The concentrations (ng g− 1; dry weight) and profiles clearly indicated the dominance of ∑ DDT contaminants followed by the ∑ HCHs, ∑30PCBs, chlordanes, and ∑10PBDEs in descending order. Concerning the spatial patterns of occurrence, industrial soils exhibited relatively higher concentration of DDTs, heavy PCBs, and PBDEs (noticeably BDE-47 and -99 congeners), while the urban soils were characterized by high total PCBs (with relatively higher levels of light PCBs), following the agricultural soils. Compared to available criterion guidelines, the current results suggested that 10% of soil samples from industrial sites exhibited slightly higher levels (> 50 ng g− 1) of DDTs. The ∑ TEQ levels for mono-ortho DL-PCBs ranged from 0.7 to 5.65 (1.9) pg TEQ g− 1 dw in all the studied samples and PCB-118 contributed significantly towards the total calculated TEQs. The results of this study will contribute to the environmental management of OHCs contaminated areas of Pakistan